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Vol. XX

No. 5

73

May 2018

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CONTENTS

46 29 58 85

80

10

10 Zoom in Bio

Class XI

The Human Heart

29 Bio Digest Biological Classification & Plant Kingdom

43 Check Your Vitals

Competition Edge

Class XII

46 Concept Map 58 Bio Digest Sexual Reproduction in Flowering Plants

73 CBSE Solved Paper 2018 64 Gear Up for AIIMS 67 NEET Warm Up 80 Rapid Fire 82 Puzzle Mania 85 Biogram

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ZOOM in The syllabus for NEET is very vast which impedes students from acquiring indepth knowledge and covering the entire syllabus at the same time. An important topic for NEET is therefore presented here in elaborate form to enable students grasp the topic, analyse the type of questions and SCORE HIGH.

The Human Heart The heart is one of the most important organs of human body. It is a muscular organ responsible for pumping blood through the blood vessels by repeated, rhythmic contractions. The term cardiac (as in cardiology) means “related to the heart” and comes from the Greek word kardia, for “heart.” The heart pumps the blood, which carries all the vital materials that help in various body functions. For example, the brain requires oxygen and glucose, which, if not received continuously, will cause it to loose consciousness. Muscles need oxygen, glucose and amino acids, as well as the proper ratio of sodium, calcium and potassium salts in order to contract normally. The glands need sufficient supply of raw materials from which they manufacture the specific secretions. If the heart ever ceases to pump blood, the body begins to shut down and after a very short period of time, death occurs. All vertebrates including humans have a single heart.

LOCATION OF HEART In the human body, the heart is usually situated in the middle of the thorax with the largest part of the heart slightly offset to the left (although sometimes it is on the right, underneath the breastbone). The heart is usually felt to be on the left side because the ventricle of left heart is stronger (it pumps to all body parts). The left lung is smaller than the right lung because the heart occupies more of the left hemithorax. The heart is located in the mediastinum which is the space between two lungs, i.e., the central subdivision of the thoracic cavity. The heart apex is the blunt point situated in an inferior (pointing down and left) direction. A stethoscope can be placed directly over the apex so that the beats can be counted. It is located posterior to the 5th intercostal space just median of the left mid-clavicular line.

STRUCTURE OF HEART The human heart is a muscular organ of a somewhat conical or pyramidal form with upper broad part, the base and lower narrow, the apex. The apex is slightly directed to the left. The heart has actually two separate pumps: a right one that pumps blood through the lungs and a left one that pumps blood through the peripheral organs. In turn, each of these is a pulsatile two-chambered part composed of an atrium and a ventricle. Each atrium is a weak primer pump for the ventricle, helping to move blood into the ventricle. The ventricles then supply the main pumping force that propels the blood to whole body. An average adult heart is about 12 cm in length, 9 cm in width and 6 cm in thickness. Its weight varies in males from 280-340 g (average 300 g) and in females from 230-280 g (average 250 g). Weight of the heart is said to be about 0.45% of body weight in males and 0.40% in females. The heart is enclosed in a fibrous sac known as the pericardium and is surrounded by the lungs. The pericardium is made up of two layers: parietal and visceral pericardium. In between these two layers, a space called pericardial cavity is present which is filled with a pericardial fluid. The pericardium protects the heart from shocks and mechanical injuries and also allows free movements of heart. 10

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Snap Shots • The mammalian heart is derived from embryonic mesoderm that differentiates after gastrulation into mesothelium,

endothelium, and myocardium. Myocardium develops into heart muscle.

External Structure Human heart is 4 chambered, consisting of two atria and two ventricles. The left and right atria are Aorta Superior vena Ligament arteriosum cava separated externally by a shallow vertical interatrial Left pulmonary artery groove. The atria are demarcated externally Right pulmonary artery Pulmonary trunk from the ventricles by an oblique groove called Left pulmonary veins atrioventricular sulcus. There are also present Right pulmonary Left auricle veins coronary sulcus, anterior interventricular Left coronary artery sulcus and posterior interventricular sulcus. Right auricle Great cardiac vein These have coronary arteries, through which the heart Right coronary Anterior interventricular artery receives blood. artery (in anterior Anterior cardiac The left atrium is smaller than the right atrium. Each vein interventricular sulcus) atrium has an appendage called an auricle which Small cardiac vein Left ventricle increases its surface area. The superior vena cava, Inferior vena cava inferior vena cava and coronary sinus open into right atrium. The left atrium receives four openings of Apex of the heart Right ventricle pulmonary veins. Fig.: Human heart in front view Ventricles are thick walled and the left ventricle is longer and narrower than the right ventricle. Its walls are about three times thicker than the right ventricle. The pulmonary trunk arises from the right ventricle. It divides into left and right pulmonary arteries that carry deoxygenated blood to the lungs. The aorta arises from the left ventricle.

Internal Structure

Atrium The two thin walled atria are separated by interatrial septum. The right atrium receives blood from superior vena cava, inferior vena cava and coronary sinus. The superior vena cava carries blood from upper body and the inferior vena cava carries blood from the lower body region. Coronary sinus carries blood from the heart itself. The right atrium receives deoxygenated blood while the left atrium receives oxygenated blood from the lungs through two pairs of pulmonary veins. An oval depression known as fossa ovalis is present in the right atrium near interatrial septum. It marks the position of an opening between two atria in the fetus, i.e., foramen ovale but in the adult it persists only as a depression. Ventricle The two ventricles are separated from each other by a thick, curved partition, the interventricular septum. The inner surface of the ventricles is raised into a network of low, muscular ridge called the columnae carneae or trabeculae carneae, and a few large, conical, muscular elevations termed the papillary muscles (musculi papillares). A prominent muscular trabeculum, called the moderator band, extends from the interventricular septum to the anterior papillary muscle in the right ventricle. The left and right pulmonary arteries carry deoxygenated blood to the lungs. The aorta arising from the left ventricle is divisible into the ascending aorta, arch of aorta and descending aorta. The right and left coronary arteries arise from the ascending aorta. The arch of the aorta (also called aortic arch) gives rise to the brachiocephalic artery (innominate artery), left common carotid artery and left subclavian artery. The descending aorta runs through the thorax and abdomen and hence it is divisible into thoracic and abdominal parts. The pulmonary trunk is connected with the aorta by the ligamentum arteriosum that represents the remnant of an embryonic connection between the pulmonary trunk and aorta. In embryo the ligamentum arteriosum is called ductus arteriosus. Coronary arteries arise from the ascending aorta and supply blood to the heart. These arteries exit from behind the aortic valve cusps in the very first part of the aorta and lead to a branching network of small arteries, arterioles, capillaries, venules and veins similar to those in other organs. Most of the cardiac veins drain into a single large vein, the coronary sinus, which empties into the right atrium. 12

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C-5A,

9337666760

Brachiocephalic artery

Left common carotid artery Left subclavian artery Aorta Left pulmonary artery

Superior vena cava

Left atrium

Right pulmonary artery

Left pulmonary veins

Pulmonary trunk Right atrium

Mitral (bicuspid) valve

Right pulmonary veins Fossa ovalis

Aortic semilunar valve

Pectinate muscles

Pulmonary semilunar valve

(horizontal muscle ridges)

Tricuspid valve Right ventricle Chordae tendineae

Left ventricle Papillary muscles Interventricular septum Epicardium Myocardium Endocardium

(held by papillary muscles)

Trabeculae carneae

(irregular muscle ridges)

Inferior vena cava

Fig.: Internal structure of human heart

Heart valves

Location and functions of heart valves have been summarised in the given table.

Table: Valves of the heart Name

Location

Function

1.

Bicuspid valve or Mitral valve (Left AV)

Between left atrium and ventricle Allows the blood to move from left atrium to left (has two flaps or cusps) ventricle

2.

Tricuspid valve (Right AV)

Between right atrium and ventricle (has three flaps)

3.

Aortic semilunar valve

Between aorta and left ventricle Allows unidirectional flow of oxygenated blood from left ventricle to aorta and prevents back flow.

4.

Pulmonary semilunar valve

Between pulmonary artery and Allows unidirectional flow of deoxygenated blood from right ventricle right ventricle to pulmonary artery and prevents back flow

5.

Eustachian valve

Right atrium

6.

Thebasian valve (Coronary valve) Right atrium

Allows the blood to move from right atrium to right ventricle

Guards the opening of inferior vena cava Guards the opening of coronary sinus

There are no valves at the entrances of the superior and inferior venae cavae (plural of vena cava) into the right atrium and of the pulmonary veins into the left atrium. However, atrial contraction pumps very little blood back into the veins because atrial contraction constricts their sites of entry into the atria, greatly increasing the resistance to backflow. Actually, a little blood is ejected back into the veins and this accounts for the venous pulse that can often be seen in the neck veins when the atria are contracting.

Functioning of valves The opening and closing of the AV valves are passive processes resulting from pressure differences across the valves. When the blood pressure in an atrium is greater than in the corresponding ventricle, the valve is pushed open and blood flows from atrium to ventricle. In contrast, when a contracting ventricle achieves an internal pressure greater than that in its connected atrium, the AV valve between them is forced closed. Therefore, blood does not normally move back into the atria and is forced into the pulmonary trunk from the right ventricle and into the aorta from the left ventricle. 14

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To prevent the AV valves from being pushed up into the atria when the ventricles are contracting (a condition called prolapse), the valves are fastened to muscular projections (papillary muscles) of the Pulmonary ventricular walls by fibrous strands chordae tendineae. The papillary semilunar valve muscles do not open or close the valves. They act only to limit the valves’ Openings to movement and prevent the backward flow of blood. coronary arteries The aortic and pulmonary artery semilunar valves function quite differently Aortic semilunar from the AV valves. The high pressure in the arteries at the end of systole valve causes the semilunar valves to snap to the closed position, in contrast to the much softer closure of the AV valves. Because of smaller openings, the Left AV velocity of blood ejection through the aortic and pulmonary valves is far (bicuspid) valve greater than that through the much larger AV valves.

HISTOLOGY OF HEART

Right AV (Tricuspid) valve

Fig.: Valves of the heart

The heart consists of an outermost smooth coelomic epithelium – visceral pericardium, the middle thick muscular layer – the myocardium, which is composed of cardiac muscle cells and the innermost layer – the endothelium consisting of the simple squamous epithelial cells.

Cardiac Muscle Cells Contractile muscles The cardiac muscle cells of the myocardium are arranged in layers that are tightly bound together and completely encircle the bloodfilled chambers. There are dark areas crossing the cardiac muscle fibres called intercalated discs; they are actually cell membranes that separate individual cardiac muscle cells from one another. When the walls of a chamber contract, they come together like a squeezing fist and exert pressure on the blood they enclose. This causes pumping of blood. Similar to smooth and skeletal muscle, it is an electrically excitable tissue that converts chemical energy stored in the bonds of ATP into force generation. Action potential propagates along cell membranes, Ca2+ enters the cytosol and the cycling of force-generation cross-bridges is activated. But unlike skeletal muscle cells, which can be rested for prolonged periods and only a fraction of which are activated in a given muscle during most contractions, every heart cell contracts with every beat of the heart. Beating about once every second, in an average life span, cardiac muscle cells may contract almost 3 billion times without resting. Remarkably, despite this enormous workload, the heart has only a limited ability to replace its muscle cells. Recent experiments suggest that only about 1 percent of heart muscle cells are replaced per year. Atrioventricular

Autorhythmic muscles (AV) node Approximately 1 percent of cardiac cells constitute a network known as the Sinoatrial conducting system of the heart (do not function in contraction rather (SA) node Bundle of His excitation). They constitute the nodal tissue which initiate heart beat and Left bundle spread the impulse. A patch of this tissue is present in the right atrium near branch the opening of superior vena cava called the sino-atrial node (SAN). Another mass of this tissue is seen in the right atrium called the atrioLeft interior ventricular node (AVN). A bundle of nodal fibres, atrioventricular division bundle (AV bundle) continues from the AVN which passes through the Left posterior atrioventricular septa to emerge on the top and immediately divides into a Right bundle division right and left bundle. These branches give rise to minute fibres throughout branch Purkinje fibres the ventricular musculature of the respective sides and are called Purkinje Fig.: Conducting system of the heart fibres which alongwith right and left bundles are known as bundle of His. The nodal musculature has the ability to generate action potentials without any external stimuli, i.e., it is autoexcitable. The SAN can generate the maximum number of action potentials, i.e., 70-75 min–1 and is responsible for initiating and maintaining the rhythmic contractile activity of the heart. Therefore, it is called the pacemaker. Our heart normally beats 70-75 times in a minute (average 72 beats min–1). The cardiac muscles contract in much the same way as skeletal muscle, except that the duration of contraction is much longer. Conversely, the specialised autorhythmic muscles contract only feebly because they contain few contractile fibrils. 16

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Working of SA node as pacemaker The AV nodal fibres when not externally stimulated discharge at 40-60 times/min. and Purkinje fibres discharge at approx. 15 to 40 times/min. in contrast to the normal rate of SA node i.e., 70-80 times/ min. The discharge rate of SA node is considerably faster than the natural self excitatory discharge rate of either of them. Each time the sinus node discharges, its impulse is conducted into both AV node or the Purkinje fibres, also discharging their excitable membranes. But the sinus node discharges again before either the AV node or the Purkinje fibres can reach their own thresholds for self-excitation. Therefore, the new impulse from the sinus node discharges both the AV node and the Purkinje fibres before self-excitation can occur in either of these. Thus, the SA node controls the beat of the heart because its rate of rhythmical discharge is faster than that of any other part of the heart and is virtually always the pacemaker of the normal heart.

HEARTBEAT To pump the blood into blood vessels, heart regularly contracts and relaxes in a rhythmic manner known as ‘heartbeat’. Each heartbeat includes one systole (contraction phase) and one diastole (relaxation phase) of the heart to distribute and receive blood to and from the body. The heart of a healthy person beats 72 times per minute. Beating is an inherent capacity of the heart. The heartbeat is of two types: neurogenic and myogenic. Neurogenic heartbeat is initiated by a nerve impulse coming from a nerve ganglion (mass of nerve cells) situated near the heart. It is present in the heart of some annelids and most arthropods. The myogenic heartbeat is initiated by a patch of modified heart muscle itself. It is found in hearts of molluscs and vertebrates.

Origin of heartbeat The mammalian heart is myogenic that means the heart beat originates from a muscle, however, it is regulated by the nerves. The heart beat originates from the sinoatrial node (SAN) or pacemaker.

Conduction of heartbeat Another mass of neuromuscular tissue, the atrioventricular node (AV node or pacesetter) is situated in the wall of the right atrium. The AV node picks up the wave of contraction propagated by SA node. A mass of specialised fibres, the bundle of His, originates from the AV node. The bundle of His divides into two branches, one going to each ventricle. Within the mycocardium of the ventricles the branches of bundle of His divide into a network of fine fibres called the Purkinje fibres. The bundle of His and the Purkinje fibres convey impulse of contraction from the AV node to the myocardium of the ventricles. The conduction of cardiac impulse can be summarised as : SA node → Atrial syncytium → Junctional fibres → AV node → AV bundle → Bundle branches → Purkinje fibres → Ventrical syncytium.

Regulation of heartbeat When a person is at rest, the heart pumps about 5 litres of blood each minute. During severe exercise, the heart may be required to pump four to seven times this amount. The basic means by which the volume pumped by the heart is regulated are of three types: (i) Intrinsic regulation : Under most conditions, amount of blood pumped per minute by heart is determined almost entirely by the rate of blood flow into heart from the veins, i.e., venous return. This intrinsic ability of heart to adapt to increasing volumes of blood is called Frank-Starling mechanism. It says that the greater the heart muscle is stretched during filling, greater is the force of contraction and the greater is the quantity of blood pumped into the aorta, i.e., within physiologic limits, the heart pumps all the blood that returns to it through veins. It can be explained as that when an extra amount of blood flows into the ventricles, the cardiac muscle is stretched to greater length, causing the muscle to contract with increased force because the actin and myosin filaments are brought to a more MT BIOLOGY

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nearly optimal degree of overlap for force generation. Therefore, the ventricle, because of its increased pumping, automatically pumps the extra blood into the arteries. This ability of stretched muscle, up to an optimal length, to contract with increased work output is characteristic of all striated muscles. Another factor also increases heart pumping when its volume is increased. Stretch of the right atrial wall directly increases the heart rate by 10 to 20 percent; this too, helps increase the amount of blood pumped each minute, although its contribution is much less than that of the Frank-Starling mechanism. (ii) Neural regulation : The cardiac centre lies in the medulla oblongata of the brain. The cardiac centre is formed of cardioinhibitor and cardio-accelerator parts. The former decreases the rate of heart beat and the latter accelerates it. The cardioinhibitor is connected with the heart through vagus nerve (it carries–parasympathetic nerve fibres) and cardio-accelerator through sympathetic nerve fibres. Sensory fibres extend from the receptors present in the superior vena cava, aorta and carotid sinuses to the cardiovascular centre in the medulla oblongata. The impulses received from the aorta and carotid sinuses decrease the heart rate, whereas, the impulses from the vena cava increase the heart rate.

Ventricular escape Strong parasympathetic stimulation can completely stop either the excitation by SA node or transmission of cardiac impulse from atria to ventricles. The ventricles stop beating for 5 to 20 seconds, but then some point in the Purkinje fibres, usually in the ventricular septal portion of the AV bundle, develops a rhythm of its own and causes ventricular contraction at a rate of 15 to 40 beats per minute. This phenomenon is called ventricular escape.

(iii) Hormonal regulation : Adrenaline (epinephrine) and noradrenaline (norepinephrine) hormones are secreted by the medulla of the adrenal glands. Noradrenaline accelerates the heartbeat under normal conditions while adrenaline does the function at the time of emergency. These hormones directly influence the SA node. Thyroxine hormone secreted by thyroid gland increases oxidative metabolism of the body cells. This requires more oxygen and thus indirectly increases heartbeat.

PULSE Pulse is the alternate expansion and elastic recoil of an artery with each systole. It is the strongest in the arteries closest to the heart. Therefore, it is also called as arterial pulse. Normal pulse rate ranges from 70–90 per minute.

HEART RATE Pulse per minute is called as heart rate. Human heart beats 72 times per minute, this is designated as heart rate. It increases during exercise, fever, anger and fear. Table:

Differences between heartbeat and pulse Heartbeat

Pulse

1.

It is the rhythmic contraction and relaxation of heart.

It is the rhythmic contraction and relaxation in aorta and its main arteries.

2.

It is regulated by the nervous and endocrine systems.

It is due to the flow of blood from the heart and is dependent on the rate of heartbeat.

3.

One complete heart beat consists of one systole and one It is a regular jerk of an artery. It depends on the rate of heartbeat. diastole and lasts for about 0.8 second.

Snap Shots • • • • • • 18

Tachycardia is the term applied to a rapid heart or pulse rate (over 100/ minute). Bradycardia is the term indicating a slow heart or pulse rate (under 50/ minute). Pulse is usually taken on the radial artery in the wrist but it can be taken on any artery. The pulse rate in children is more rapid than in adults. The pulse rate is more rapid in the female than in the male. When any strong emotion is experienced the pulse rate is increased, for example, anger excitement, fear, etc. MT BIOLOGY

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CARDIAC OUTPUT The amount of blood pumped by heart per minute is called cardiac output. Cardiac output of humans is approximately 5 litres per minute. Cardiac output is also the volume of blood flowing through either the systemic or the pulmonary circuit per minute. It is determined by multiplying the heart rate with the volume of blood ejected by each ventricle during each beat, which is called the stroke volume. Cardiac output = Heart rate × Stroke volume = 72 beats/min. × 0.07 litre/beat = 5.0 litres/min. These values are within the normal range for a resting, average-sized adult. Coincidentally, total blood volume is also approximately 5 L, so essentially all the blood is pumped around the circuit once each minute. During periods of strenuous exercise in well-trained athletes, the cardiac output may reach 35 L/min; the entire blood volume is pumped around the circuit seven times a minute. Even sedentary, untrained individuals can reach cardiac outputs of 20-25 L/min during exercise.

CARDIAC CYCLE Cardiac cycle is the term referring to the cardiac events that occur from the beginning of one heart beat to the beginning of the next heart beat. The contraction phase is called as systole while the relaxation phase is called as diastole. The durations of a cardiac cycle is 0.8 sec. The successive stages of the cardiac cycle are briefly described below. (a) Atrial systole : The atria contract due to a wave of contraction, stimulated by the SA node. The blood is forced into the ventricles as the bicuspid and tricuspid valves are open. (e) Complete ventricular diastole : The tricuspid and bicuspid valves open when the pressure in the ventricles falls and blood flows from the atria into the ventricles. Contraction of the heart does not cause this blood flow. It is due to the fact that the pressure within the relaxed ventricles is less than that in the atria and veins.

(b) Beginning of ventricular systole : The ventricles begin to contract due to a wave of contraction, stimulated by the AV node. The bicuspid and tricuspid valves close immediately producing part of the first heart sound.

(d) Beginning of ventricular diastole : The ventricles relax and the semilunar valves are closed. This causes the second heart sound.

(c) Complete ventricular systole : When the ventricles complete their contraction, the blood flows into the pulmonary trunk and aorta as the semilunar valves open.

HEART SOUNDS Two sounds are heard normally through a stethoscope (a medical instrument for listening the action of heartbeat) during each cardiac cycle. The first sound is a low pitched slightly prolonged “lubb”, caused by sudden closure of the mitral and the tricuspid valves at the start of ventricular systole. The second sound is a shorter, high pitched “dup” caused by vibrations associated with closure of the aortic and pulmonary semilunar valves just at the end of the ventricular systole. The first sound has a duration of 0.15 seconds and a frequency of 25-45 Hz. The second sound lasts about 0.12 seconds with a frequency of 50 Hz.

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Heart murmurs Murmurs are abnormal sounds heard in various parts of the vascular Normal open valve Stenotic valve system. The major cause of cardiac murmurs is due to abnormalities of the heart valves. It may arise due to improper closing of any heart valve or in patients with interventricular septal defects that cause Narrowed valve Laminar flow = Quiet Turbulent flow = Murmur blood flow to be turbulent. Normal closed valve Insufficient valve Normally, blood flow through valves and vessels is laminar flow– i.e., it flows in smooth concentric layers. Turbulent flow can be caused by : – blood flowing rapidly in the usual direction through an abnormally Leaky valve No flow = Quiet Turbulent backflow = Murmur narrowed valve (stenosis); Fig.: Heart valve defects causing turbulent blood – blood flowing backward through a damaged, leaky valve flow and murmurs. (insufficiency); – blood flowing between the two atria or two ventricles through a small hole in the wall separating them (called a septal defect).

Significance of heart sounds Heart sounds give valuable information about working of the heart valves. The exact timing and location of the murmur provide the physician with a powerful diagnostic clue. For example, a murmur heard throughout systole suggests a stenotic pulmonary or aortic valve, an insufficient AV valve, or a hole in the interventricular septum. In contrast, a murmur heard during diastole suggests a stenotic AV valve or an insufficient pulmonary or aortic valve.

DIAGNOSTIC TESTS Human cardiac functioning can be measured by a variety of methods. Moreover, two and three-dimensional images of the heart can be obtained throughout the entire cardiac cycle.

Echocardiography Ultrasonic waves are beamed at the heart and returning echoes are electronically plotted by computer to produce continuous images of the heart. This technique can detect the abnormal functioning of cardiac valves or contractions of the cardiac walls and can also be used to measure ejection fraction. Echocardiography is a non-invasive technique because everything used remains external to the body. Other visualisation techniques are invasive.

Cardiac angiography It requires the temporary threading of a thin, flexible tube called a catheter through an artery or vein into the heart. A liquid containing radio-opaque contrast material is then injected through the catheter during high-speed X-ray videography. This technique is useful not only for evaluating cardiac function but also for identifying narrowed coronary arteries.

Electrocardiogram (ECG) ECG is a graphic record of the electric current produced by the excitation of the cardiac muscles. Waller (1887) first recorded the electrocardiogram but Einthoven (1903) studied ECG in details, therefore, he got Nobel Prize in 1924 for the discovery of ECG. He is also considered “Father of the electrocardiography”. When the cardiac impulse passes through the heart, electrical current also spreads from the heart into the adjacent tissues surrounding the heart. A small portion of the current spreads all the way to the surface of the body. If electrodes are placed on the skin on opposite sides of the heart, electrical potentials generated by the current can be recorded; the recording is known as an electrocardiogram (ECG). The instrument used to record the changes is an electrocardiograph. P-R interval = 0.16 sec A normal electrocardiogram (ECG) is composed of a P wave, a QRS wave (complex) and a T wave. The letters are arbitrarily selected and do not stand for any particular words. The P wave is a small upward wave that indicates the depolarisation of the atria (atrial contraction). It is caused by the activation of SA node. The impulses of contraction start from the SA node and spread throughout the artia. 20

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The QRS wave (complex) begins after a fraction of second of the P wave. It begins as a small downward deflection (Q) and continues as large upright (R) and triangular wave, ending as downward wave (S) at its base. It represents ventricular depolarisation (ventricular contraction). It is caused by the impulses of the contraction from AV node throughout the bundle of His and Purkinje fibres and the contraction of the ventricular muscles. Thus this wave is due to the spread of electrical impulse through the ventricle. The T wave is dome-shaped which indicates ventricular repolarisation (ventricular relaxation). The potential generated by the recovery of the ventricle from the depolarisation state is called the repolarisation wave. The end of the T-wave marks the end of systole.

Table :

ECG intervals

Intervals

Normal duration (in sec.)

Events in the heart during interval

Average

Range

0.182

0.12 – 0.20

QRS duration

0.08

< 0.12

Ventricular depolarisation and atrial repolarisation

QT interval

0.40

< 0.44

Ventricular depolarisation plus ventricular repolarisation

ST interval (QT minus QRS)

0.32

–

PR

1 2

interval1

Atrial depolarisation and conduction through AV node

Ventricular repolarisation

Measured from the beginning of the P wave to the beginning of the QRS complex. Shortens as heart rate increases from average of 0.18 at a rate of 70 beats/min to 0.14 at a rate of 130 beats/min.

Clinical significance Any deviation from the normal ECG shape indicates a possible abnormality or disease. Enlargement of the P wave indicates enlargement of the atria. During atherosclerotic heart disease and rheumatic fever, the P–R interval is lengthened. This is due to the inflammation of atria and AV node. The enlarged Q and R waves indicate a myocardial infarction (heart attack). The S–T segment is elevated in acute myocardial infarction and depressed when the heart muscle receives insufficient oxygen. T wave is flat when the heart muscles receive insufficient oxygen as in atherosclerotic heart disease. It may be elevated when the body’s potassium level is increased.

Rate of heartbeat as determined from the electrocardiogram

The rate of heartbeat can be determined easily from an electrocardiogram because the heart rate is the reciprocal of the time interval between two successive heartbeats. If the interval between two beats as determined from the time calibration lines is 1 second, the heart rate is 60 beats per minute. The normal interval between two successive QRS complexes in the adult person is about 0.83 second. This is a heart rate of 60/0.83 times per minute or 72 beats per minute.

BLOOD PRESSURE Blood pressure is defined as the force or pressure which the blood exerts on the walls of the artery in which it is contained. The arterial blood pressure is the result of the discharge of the blood from the left ventricle into the already full aorta. When the left ventricle contracts pushing the blood into the aorta, the pressure produced is known as systolic blood pressure (120 mmHg). When the complete diastole occurs and the heart is resting, the pressure within the blood vessels is called as the diastolic blood pressure (80 mmHg). The blood pressure is expressed as BP = 120/80 mmHg. The difference between the systolic and diastolic pressure is called pulse pressure. The average of blood pressure levels is called mean blood pressure. Its normal value is 40 mmHg but becomes more in case of hypertension. Pulse pressure is lower in case of kids.

Measurement of blood pressure Both systolic and diastolic blood pressures are readily measured in human beings with the use of a device called sphygmomanometer, in terms of height in millimeters of a column of mercury. An inflatable cuff containing a pressure gauge is wrapped around the upper arm and a stethoscope is placed in a spot on the arm just below the cuff where the brachial artery lies. The cuff is then inflated with air to a pressure greater than systolic blood pressure. The high pressure in the cuff is transmitted through the tissue of the arm and completely compresses the artery under the cuff, thereby preventing blood flow through the artery. The air in MT BIOLOGY

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the cuff is then slowly released, causing the pressure in the cuff and on the artery to decrease. When cuff pressure has decreased to a value just below the systolic pressure, the artery opens slightly and allows blood flow for a brief time at the peak of systole. During this interval, the blood flow through the partially compressed artery occurs at a very high velocity because of the small opening and the large pressure difference across the opening. The high-velocity blood flow is turbulent and, therefore, produces vibrations called Korotkoff’s sounds that can be heard through the stethoscope. Thus, the pressure at which sounds are first heard as the cuff pressure decreases is identified as the systolic blood pressure. As the pressure in the cuff decreases further, the duration of blood flow through the artery in each cycle becomes longer. When the cuff pressure reaches the diastolic blood pressure, all sound stops because flow is now continuous and non-turbulent through the open artery. Therefore, diastolic pressure is identified as the cuff pressure at which sounds disappear. The sounds heard during measurement of blood pressure are not the same as the heart sounds described earlier, which are due to closing of cardiac valves.

BLOOD CIRCULATION In human, there are two circuits of blood circulation for greater efficiency and to completely prevent the mixing of oxygenated and deoxygenated blood. Usually, it is called double circulation that is defined as the passage of same blood twice in the heart through separate pathways for completing one cycle. It consists of pulmonary circulation and systemic circulation. Pulmonary artery carries deoxygenated blood from heart to lungs.

Capillary bed of lungs where gas exchange occurs, and deoxygenated blood becomes oxygenated. Pulmonary vein supplies oxygenated blood to the heart.

Vena cavae receive deoxygenated blood from all veins of systemic circulation and open into right atrium.

Right atrium Right ventricle Systemic veins Oxygen poor, CO2 rich blood

Pulmonary circuit: The flow of deoxygenated blood from the right ventricle to the lungs and the return of oxygenated blood from the lungs to the left atrium. Aorta and branches Left atrium Left ventricle Systemic arteries Oxygen rich, CO2 poor blood

Capillary bed of all body tissues Systemic circuit: It involves flow of oxygenated blood from where gas exchange occurs the left ventricles to all parts of the body and deoxygenated blood from various body parts to the right atrium. Fig.: Double circulation

• A portal system is named after the organ to which it carries blood. The vertebrates possess two or three portal systems: Hepatic

portal, renal portal and hypophysial portal systems.

Circulation through special regions Coronary circulation The flow of oxygenated blood from the ascending aorta to the heart muscle and the return of deoxygenated blood from the heart muscle to the right atrium is called coronary (cardiac) circulation. The coronary veins bring deoxygenated blood to the coronary sinus.

Hepatic portal circulation It is flow of deoxygenated blood from the digestive organs to the liver before returning to the heart. Excess glucose present in absorbed food is converted into glycogen in liver, which is stored for later use, during deficiency of food.

Hypophysial portal circulation This portal system consists of two hypophysial portal veins which carry blood from the hypothalamus of the brain to the anterior lobe of the pituitary gland (hypophysis). This portal system enables the hormones of hypothalamus to reach the anterior lobe of the pituitary gland.

The advantage of double circulation is that the blood can be sent to the lungs to pick up oxygen and then returned to the heart to be pumped again before travelling around the body. The blood therefore is pumped through the capillary bed (which slows it down and reduces its pressure) then receives another pump before it enters another capillary bed. Double circulatory systems are therefore, high pressure system. In this type of circulation there is no mixing of the oxygen rich blood and oxygen poor blood in the heart. Oxygenated blood carries more oxygen to different body parts as well as more CO2 is carried with deoxygenated blood for the removal through lungs. 22

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DISORDERS OF CIRCULATORY SYSTEM Hypertension It is the most common disease affecting the heart and blood vessels. A blood pressure of 120/80 mmHg is considered normal. But the increase in blood pressure beyond 140 mmHg (systolic) and 90 mmHg (diastolic) is called high blood pressure (hypertension). A diet full of oily food, is known to increase cholesterol level, causing thickening of the arteries which results in high blood pressure. Tobacco smoking increases the heart rate, contracts blood vessels and raises blood pressure. High blood pressure can harm heart, brain, kidneys and eyes.

Atherosclerosis /Coronary Artery Disease (CAD) It is the deposition of lipids (cholesterol) on the wall lining the lumen of arteries called atheromatous or atherosclerotic plaque. These plaques may completely block the artery. Such plaques, if formed in the coronary artery, reduce the blood supply to the heart and may result in heart attack or stroke.

Arteriosclerosis It is the hardening and thickening of the arteries due to the deposition of calcium salts and cholesterol. Such artery loses the property of distension and its walls may rupture, resulting in the formation of clot or thrombosis in the coronary artery leading to heart attack and even death.

Heart block It is a condition in which the sinus node is normal but the impulses are interrupted at any point along the conducting system of the heart. Thus, impulses do not follow the normal conduction pathway. Two common types of heart block are : AV block : It occurs at the atrioventricular node. The impulses from the SA node do not reach the AV node. Bundle branch block : It involves one of the branches of the bundle of His.

Angina pectoris Sclerosis of the coronary arteries can cause pain in the chest. This anginal pain usually starts in the centre of the chest and spreads down the left arm. The chest pain may be associated with restlessness, fear or anxiety, a pale skin, profuse sweating and vomiting (all because of increased adrenergic discharge). The pain lasts for only a few moments.

Coronary thrombosis A clot may form in the lumen of a coronary artery, it is called coronary thrombosis. Therefore, a large portion of the heart muscle is deprived of blood and the patient develops a ‘heart attack’. Anticoagulant drugs like TPA (tissue plasminogen factor) and streptokinase helps to prevent the formation and extension of blood clots if given within 4 hours of attack.

Heart failure (Congestive heart failure) It is a collection of signs and symptoms that occur when the heart fails to pump an adequate cardiac output. Heart failure is not the same as cardiac arrest (when the heart stops beating) or heart attack (when the heart muscle is suddenly damaged by inadequate blood supply). Rheumatic Heart Disease (RHD) The patient may have an acute rheumatic fever, joint pains and infection of throat. Rheumatic fever may cause permanent damage of one or more valves (mitral or aortic semilunar valves), pericarditis and myocarditis. Its causative factor is Streptococcus bacteria.

Ebstein’s disease It is a congenital downward displacement of the tricuspid valve into the right ventricle. Fibrillation Fibrillation is a condition in which the heart muscle contracts very rapidly but in an uncoordinated fashion. There are atrial and ventricular fibrillation. Ventricular fibrillation is life threatening unless it can be stopped by defibrillation. A machine called a defibrillator is used to do this. Cardiac arrest It is the complete stoppage of the heartbeat (sudden and complete loss of cardiac function).

Heart attack Heart attack, also called myocardial infarction (MI), refers to a sudden event in which a portion of the heart muscle stops working because it no longer receives blood, usually due to a blockage in the coronary artery. Generally, a heart attack occurs when plaque (fat, cholesterol and calcium) builds up and then ruptures in the coronary artery, creating a place where a blood clot can form (thrombus). Signs of heart attack : Chest pain; pain or discomfort in the upper body (arms, back, neck, jaws or stomach); shortness of breath (usually occurs at the same time as chest pain); cold sweat; nausea or vomiting and light headedness. Controllable risk factors : High cholesterol; cigarette smoking; excess weight; sedentary lifestyle; stress; high blood pressure; diabetes and certain drugs, such as oral contraceptives for women who smoke. Congenital heart diseases Defects or diseases of the heart from the birth are known as congenital heart diseases and are due to some error in the development of the heart. It is possible that some of these defects may be due to an infectious disease like rubella (German measles) in the mother or administration of some harmful drugs during first three months of pregnancy. A small number of cases of congenital heart diseases are associated with chromosomal abnormalities. Ischaemia It is inadequate flow of blood to a part of the heart caused by obstruction to its blood supply. MT BIOLOGY

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THERAPEUTIC DEVICES Prosthetic cardiac pacemaker/Artificial pacemaker. When the natural pacemaker SA node does not work properly, in such patients normal heart beat can be restored and maintained with an artificial pacemaker. The artificial pacemaker was introduced by Pacemaker Chardack in 1960. leads Temporary pace maker is used in emergency such as during bradycardia. Pacemaker Right Permanent pacemaker is used in atrioventricular (AV) block, SA node dysfunction, artrium Right etc. The artificial pacemaker consists of a pulse generator containing cell (solid state ventricle lithium cell), the lead in the form of a wire and an electrode. During implantation the pulse-generator is placed in a sub-cutaneous pocket. The lead is inserted into a particular vein which is finally carried to the right ventricle to make contact with the ventricular myocardium. Defibrillator : Artificial fibrillation may occur in myocardial infarction and in rheumatic heart disease. Ventricular fibrillation is immediately life threating unless it can be stopped by defibrillation. The arrest of cardiac muscle (atrial or ventricualr) with restoration of the normal rhythm is called defibrillation. A machine which is used to do defibrillation is called defibrillator. Angioplasty (Balloon catheterisation) : In this technique, atherosclerotic plaques from the coronary arteries are removed through ballooning. During this procedure, a very small balloon-tipped catheter is inserted into the coronary artery under X-ray observation. Then the balloon is inflated with air to squash the plaques against the blood vessel wall, thereby clearing the lumen of the vessel for blood. It increases the blood flow through the vessel. Vascular grafts (Artificial arteries) : Arteries supply blood to various parts of the body. So, any blockade in them would deprive the organ or the tissue to get blood or in other words the oxygen and various nutrients. This requires reconstructive operation which is done by the use of artificial arteries or vascular grafts. These artificial arteries are made from porous plastic fibres of dacron or teflon. Stent : It is small mesh tube that is used when plaque blocks blood vessels or treat narrow or weak arteries. It is made of either metal or plastic. Stent grafts are larger stents used for larger arteries. They may be made Stent Catheter of a specialised fabric. Coronary Artery Bypass Grafting (CABG) : It is normally done when the coronary artery is totally blocked by clot/clots. In this surgery, a blood vessel is taken from another Guide part of the body and is used to bypass the blocked region of the coronary artery. The wire saphenous vein (from the leg) and the internal mammary artery (from the chest) are mostly used for this procedure. After this surgery the blood supply to the heart increases.

1. Which of the following waves is not represented in a typical ECG? (a) Depolarisation of atria (b) Depolarisation of ventricles (c) Repolarisation of atria (d) Repolarisation of ventricles 2. The frequency of heartbeat in our body is maintained by (a) AV Node (b) SA Node (c) bundle of His (d) chordae tendineae. 3. During ventricular systole, (a) oxygenated blood is pumped into the pulmonary artery and deoxygenated blood is pumped into the pulmonary vein 24

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(b) oxygenated blood is pumped into the aorta and deoxygenated blood is pumped into the pulmonary vein (c) oxygenated blood is pumped into the pulmonary vein and deoxygenated blood is pumped into the pulmonary artery (d) oxygenated blood is pumped into the aorta and deoxygenated blood is pumped into the pulmonary artery. 4. Which of the following statement(s) regarding the cardiac system is/are correct? (i) Human heart is an ectodermal derivative. (ii) Mitral valve guards the opening between the right atrium and left ventricle.

(iii) SAN is located on the left upper corner of the right atrium. (iv) Stroke volume × Heart rate = Cardiac output. (a) (i) only (b) (i) and (ii) (c) (ii) and (iii) (d) (iv) only

10. If vagus nerve to heart is cut the heartbeat will (a) decrease (b) increase (c) remain normal (d) stop. 11. Given below is the ECG of a normal human. Which one of its components is correctly interpreted below?

5. Match column I with column II and select the correct option from the codes given below. Column I A. Superior vena cava B. Inferior vena cava C. Pulmonary artery

D. Pulmonary vein

(a) (b) (c) (d)

Column II (i) Carries deoxygenated blood to lungs (ii) Carries oxygenated blood from lungs (iii) Brings deoxygenated blood from lower part of body to right atrium (iv) Bring deoxygenated blood from upper part of body to right atrium

A-(ii), B-(iv), C-(iii), D-(i) A-(iv), B-(i), C-(ii), D-(iii) A-(iv), B-(iii), C-(i), D-(ii) A-(iv), B-(i), C-(iii), D-(ii)

6. Coronary heart disease is due to (a) streptococci bacteria (b) inflammation of pericardium (c) weakening of the heart valves (d) insufficient blood supply to the heart muscles. 7. The given figure shows schematic plan of blood circulation in humans with labels A to D. Identify the label and give its functions. (a) C-Vena cava - takes blood from body parts to right auricle, pCO2 = 45 mm Hg (b) D-Dorsal aorta - takes blood from heart to body parts, pO2 = 95 mm Hg (c) A-Pulmonary vein - takes impure blood from body parts, pO2 = 60 mm Hg (d) B-Pulmonary artery - takes blood from heart to lungs, pO2 = 90 mm Hg (NEET 2013) 8. Father of the electrocardiography is (a) Waller (b) Willam Harvery (c) Chardack (d) Einthoven. 9. Papillary muscles occur in (a) ventricles (b) auricles (c) atrioventricular valves (d) pulmonary valves.

(a) Complex QRS - one complete pulse (b) Peak T - initiation of total cardiac contraction (c) Peak P and peak R together - systolic and diastolic blood pressures (d) Peak P- initiation of left atrial contraction only

12. How many double circulations are normally completed by the human heart, in one minute? (a) Eight (b) Sixteen (c) Seventy two (d) Thirty six

13. During acute myocardial infarction which of the following changes occurs in the ECG? (a) Flattened T wave (b) Depressed ST segment (c) Elevated ST segment (d) Increased length of PQ interval 14. A heart murmur indicates a defective (a) sinoatrial node (b) atrioventricular node (c) bundle of His (d) heart valve. 15. Which of the following contains blood with the lowest oxygen content? (a) Aorta (b) Left atrium (c) Right ventricle (d) Pulmonary veins 16. Blood pressure is controlled by (a) thyroid gland (b) adrenal gland (c) thymus gland (d) parathyroid gland. 17. What happens when the pacemaker becomes non-functional? (a) Only auricles contract rhythmically. (b) Only ventricles contract rhythmically. (c) Cardiac muscles do not undergo co-ordinated rhythmic movements. (d) Auricles and ventricles contract rhythmically. 18. Identify the correct statement regarding cardiac activity. (a) Normal activities of the human heart is regulated intrinsically, hence, it is neurogenic. (b) A special neural centre in the medulla oblongata can moderate the cardiac function through the CNS. (c) Parasympathetic neural signals increase the rate of heart beat. (d) Adrenal medullary hormones can increase cardiac output. (e) The end of a T-wave marks the end of diastole. (Kerala PMT 2014) MT BIOLOGY

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19. Pacemaker is situated in heart (a) in the wall of right atrium (b) on inter auricular septum (c) on inter ventricular septum (d) in the wall of left atrium. 20. First heart sound is (a) ‘lubb’ due to closure of AV valves (b) ‘lubb’ due to closure of spiral valves (c) ‘dup’ due to closure of AV valves (d) ‘dup’ due to closure of spiral valves. 21. If the heart sound recording and ECG recordings are superimposed then the ‘lubb’ sound would occur (a) at the P wave (b) just after the T wave (c) just after the QRS complex (d) just after the P wave. 22. T wave of ECG represents (a) ventricular depolarisation (b) ventricular repolarisation (c) depolarisation of atria (d) auricular repolarisation. 23. How do parasympathetic neural signals affect the working of the heart? (a) Reduce both heart rate and cardiac output. (b) Heart rate is increased without affecting the cardiac output. (c) Both heart rate and cardiac output increase. (d) Heart rate decreases but cardiac output increases. (AIPMT 2014) 24. In the given figure the durations of the events of the cardiac cycle are given. Identify these events and select the correct option. A (a) Auricular systole (b) Ventricular systole (c) Ventricular systole (d) Joint diastole

B Joint diastole Joint diastole Auricular systole Auricular systole

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29. The system in which the veins begin as capillaries in one organ and breaks up into capillaries in different organ is called (a) portal system (b) pulmonary circulation (c) systemic circulation (d) cardiac capillaries. 30. Heart pumps blood more forcefully in older persons than younger ones due to (a) decrease in oxygen content of blood (b) decrease in elasticity of arteries (c) fall in nutrient content of blood (d) increase in elasticity of arteries. 31. The given figure shows an angiogram of the coronary blood vessel. Which one of the following statements correctly describes, what is being done?

B C

C Ventricular systole Auricular systole Joint diastole Ventricular systole

26. Blood vessel carrying least CO2 is (a) pulmonary vein (b) pulmonary artery (c) vena cava (d) hepatic vein. MT BIOLOGY

28. Which of the following statements is incorrect? (a) The amount of blood pumped each minute often can be increased more than 100 percent by parasympathetic stimulations. (b) Noradrenaline accelerates the heartbeat under normal conditions while adrenaline do the same function at the time of emergency. (c) Most of the cardiac veins drain into a single large vein, the coronary sinus which empties into the right atrium. (d) Veins have valves which prevent backward flow of blood.

A

25. Which of the following statements is incorrect? (a) Veins are typically larger in diameter than arteries. (b) Due to the small size of capillaries, blood flows more rapidly in them than in other parts of circulatory system. (c) Walls of arteries are elastic enabling them to stretch and shrink during changes in blood pressure. (d) Veins contain more blood than any other part of circulatory system.

26

27. Hardening of the wall of small arteries is known as (a) thrombosis (b) arteriosclerosis (c) atherosclerosis (d) heart attack.

(a) It is coronary artery which has a cancerous growth that is being removed. (b) It is coronary artery which is blocked by a plaque and the same is being cracked. (c) It is coronary vein in which the defective valves are being opened. (d) It is coronary vein blocked by a parasite (blood fluke) that is being removed. 32. Select the wrong statement. (a) One complete heartbeat consists of one systole and one diastole and lasts for about 0.8 second. (b) During myocardial infarction, the PR interval in ECG is lengthened. (c) SAN can generate the maximum number of action potential around 70-75 min–1. (d) Neural signals through the sympathetic nerves can increase the rate of heartbeat.

33. In normal ECG which of the segment shows the correct representation of respective activity of the human heart? (a) P - depolarisation of atria (b) R - repolarisation of ventricles (c) S - start of systole (d) T - end of diastole 34. Select the correct statement regarding the blood pressure. (a) 100/55 mmHg is considered an ideal blood pressure. (b) 130/90 mmHg is considered high and requires treatment. (c) 190/110 mmHg may harm vital organs like brain and kidney. (d) 105/50 mmHg makes one very active. 35. Select the incorrect match. (a) Aortic semilunar valve - Allows unidirectional flow of oxygenated blood from left ventricle to aorta (b) Mitral valve - Allows the blood to move from left atrium to left ventricle (c) Eustachian valve - Guards opening of coronary sinus (d) Tricuspid valve - Allows the blood to move from right atrium to right ventricle 36. Doctors use stethoscope to hear the sounds produced during each cardiac cycle. The second sound is heard when (a) AV node receives signal from SA node (b) AV valves open up (c) ventricular walls vibrate due to gushing in of blood from atria (d) semilunar valves close down after the blood flows into vessels from ventricles. (AIPMT 2015) 37. Consider the following statements and select the correct option stating which ones are true (T) and which ones are false (F). (i) Cardiac centre lies in the medulla oblongata of the brain. (ii) Tachycardia is the term indicating slow heart pulse rate. (iii) Cardiac output of humans is approximately 5 litres per minute. (iv) The first sound has a duration of 0.12 seconds and frequency of 40-50Hz. (a) (b) (c) (d)

(i)

(ii)

(iii)

(iv)

T T F F

T F T T

F T T F

F F F T

38. Which layer of the heart is composed of cardiac muscle cells? (a) Epicardium (b) Myocardium (c) Endocardium (d) All of these

39. Read the following statement and select the correct option. Statement A : Wall of the ventricles are thicker than the auricles. Statement B : Chordae tendineae are attached to cone shaped projections of the ventricular wall known as papillary muscles. (a) Both statements A and B are correct and B is the correct explanation of A. (b) Both statements A and B are correct but B is not the correct explanation of statement A. (c) Statement A is correct but B is incorrect. (d) Both statements A and B are incorrect. 40. The first heart sound is caused by the closure of A and B valve. A B (a) bicuspid aortic semilunar (b) bicuspid tricuspid (c) tricuspid pulmonary semilunar (d) Eustachian thebasian 41. Blood pressure in the pulmonary artery is (a) more than that in the pulmonary vein (b) less than that in the vena cava (c) same as that in the aorta (d) more than that in the carotid. (NEET-I 2016) 42. What is the stroke volume of an adult human heart? (a) 50 mL (b) 70 mL (c) 90 mL (d) 100 mL (West Bengal 2015) 43. The correct route through which pulse-making impulse travels in the heart is

1.

Make as many biological terms as possible using the given letters. Each word should contain the letter given in circle. 2. Minimum 4 letter word should be made. 3. In making a word, a letter can be used as many times as it appears in the box. 4. Make at least 1 seven letter word.

F R

L

C B

T U

G C I

S

M O A O E N L A

Send your response at [email protected] or post to us with complete address by 25th of every month to win exciting prizes. Winners’ name will be published in next issue.

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(a) SA node → Purkinje fibres → bundle of His → AV node → heart muscles (b) SA node → AV node → bundle of His → Purkinje fibres → heart muscles (c) AV node → bundle of His → SA node → Purkinje fibres → heart muscles (d) AV node → SA node → Purkinje fibres → bundle of His → heart muscles 44. Bundle of His is a network of (a) muscle fibres distributed throughout the heart walls (b) muscle fibres found only in the ventricle wall (c) nerve fibres distributed in ventricles (d) nerve fibres found throughout the heart. 45. If due to some injury the chordae tendinae of the tricuspid valve of the human heart is partially non-functional, what will be the immediate effect? (a) The flow of blood into the aorta will be slowed down. (b) The ‘pacemaker’ will stop working. (c) The blood will tend to flow back into the left atrium. (d) The flow of blood into the pulmonary artery will be reduced. 46. The hepatic portal vein drains blood to liver from (a) stomach (b) kidneys (c) intestine (d) heart. (NEET 2017) 47. In the given figure of the heart which of the marked structure (A, B, C, D, E) carries oxygenated blood? Contributed by : Shalaka Deo (Nagpur, Maharashtra)

SOLUTIONS TO APRIL 2018 CROSSWORD 1 C 2H A L K E 3 O T O L I T H E 4 R A 5 P 6N E A O O E S N O I S P 7 D I S U L F I R A M 8 L S 9 L L I G N I N 10 12 11 N S E R E O P I U M 13 P A N T H O T A X Y S L R 14 T I C K I 15 O G R A N A S X E

RIDDLE SOLUTIONS A. B. C. 28

Molecular farming Herdmania Prof. Karl von Frisch MT BIOLOGY

April 2018

D. Sella turcica E. Orthodox seed

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(a) A, B, C and D (c) A and D

(b) A and E (d) C and E

48. Read the statements A and B and select the correct option Statement A : Atherosclerosis is a disease characterised by the thickening of arterial walls. Statement B : Deposition of cholesterol and triglycerides in the arterial walls causes atherosclerosis. (a) Both statements A and B are correct and B is the correct explanation of A. (b) Both statements A and B are correct but B is not the correct explanation of statement A. (c) Statement A is correct but B is incorrect. (d) Both statements A and B are incorrect. 49. An artificial pacemaker is implanted sub-cutaneously and connected to the heart in patients (a) having 90% blockage of the three main coronary arteries (b) having a very high blood pressure (c) with irregularity in the heart rhythm (d) suffering from arteriosclerosis. (AIIMS 2017) 50. In order for the blood to flow from right ventricle to left ventricle in mammalian heart, it must flow through (a) right ventricle, pulmonary arteries, lungs, pulmonary veins, left atrium (b) right ventricle, pulmonary veins, lungs, pulmonary arteries, left atrium (c) right ventricle, right atrium, lungs, pulmonary veins, left atrium (d) right ventricle, systemic aorta, lungs, pulmonary veins, left atrium

ANSWER KEY 1. 6. 11. 16. 21. 26. 31. 36. 41. 46.

(c) (d) (a) (b) (c) (a) (b) (d) (a) (a,c)

2. 7. 12. 17. 22. 27. 32. 37. 42. 47.

(b) (a) (c) (c) (b) (b) (b) (b) (b) (c)

3. 8. 13. 18. 23. 28. 33. 38. 43. 48.

(d) (d) (c) (d) (a) (a) (a) (b) (b) (a)

4. 9. 14. 19. 24. 29. 34. 39. 44. 49.

(d) (a) (d) (a) (d) (a) (c) (b) (b) (c)

5. 10. 15. 20. 25. 30. 35. 40. 45. 50.

(c) (b) (c) (a) (b) (b) (c) (b) (d) (a)



Class XI

This article covers high yield facts of the given topic.

Biological Classification • The scientific procedure of arranging organisms into groups and subgroups on the basis of their similarities and dissimilarities and placing them in taxonomic hierarchy, is known as biological classification. • A classification system helps in identification of organisms and understanding the relationships amongst different groups of organisms. • The organisms of the past can be studied only with a proper system of classification and evolutionary tendencies can be known on the basis of relationship and simplicity or complexity found in the members of various taxa.

TYPES OF CLASSIFICATION • There are three main types of classification-artificial, natural and phylogenetic.

Types of Classification Artificial

• It uses one or two morphological characters for grouping of organisms.

• Often results in placing of unrelated organisms in a group.

Natural

• It considers comparable study of a number of characters for grouping of organisms.

• Related organisms are placed in the same group.

Phylogenetic

• It takes into account evolutionary relationships of organisms.

• This system is highly dynamic system as its major source is fossil records.

• Some of the advocates of artificial system of classification were Aristotle, Linnaeus, Pliny, Charaka, Andrea Caesalpino. • George Bentham and J.D. Hooker proposed the natural system of classification and some of the advocates of this system were John Ray, Michel Adanson, A.P. de Candolle. • Phylogenetic system of classification was proposed by Engler and Prantl and some of the advocates of this system of classification were Eichler, John Hutchinson. • Depending upon the type of system of classification, organisms are classified into two kingdoms, three kingdoms, four kingdoms, five kingdoms and now into six kingdoms. MT BIOLOGY

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Numerical Taxonomy : It evaluates resemblances and differences through statistical methods based on a large number of characters obtained from all disciplines of biology. Cytotaxonomy : It is based on cytological information like chromosome number, structure and meiotic behaviour. Chemotaxonomy : It uses the chemical constituents of the plants as these are generally specific and stable.

Two Kingdom Classification • Two kingdom classification system was suggested by Carolus Linnaeus (the father of taxonomy) in 1758. • The organisms were divided into two kingdoms - Kingdom Plantae and Kingdom Animalia. Two kingdom system of classification did not distinguish between the eukaryotes and prokaryotes, unicellular and multicellular and photosynthetic (green algae) and non-photosynthetic (fungi) organisms. Hence, two kingdom classification was found inadequate.

Three Kingdom Classification • Haeckel (1866) separated unicellular animals, algae and fungi from other organisms on the basis of lack of tissue differentiation. The new group was called Kingdom Protista. • Later on fungi and multicellular algae were taken out from the group so that Kingdom Protista came to have only unicellular organisms. The organisms were divided into three Kingdoms : Plantae, Protista and Animalia.

Four Kingdom Classification • With the discovery of electron microscope, it became clear that bacteria and related organisms have a different nuclear structure as compared to others. • They are prokaryotes in contrast to others which have a true nucleus and are called eukaryotes. • Copeland (1956) created a separate Kingdom Monera for them. • This divided the living world into four Kingdoms : Monera, Protista, Plantae and Animalia. • In this system fungi continued to remain with the plantae.

Five Kingdom Classification • Five kingdom classification was proposed by an American taxonomist, R.H. Whittaker (1969). • The kingdoms were named Monera, Protista, Fungi, Plantae and Animalia. • The main criteria for classification used by him include cell structure, thallus organisation, mode of nutrition, reproduction and phylogenetic relationships. Characteristics of the five kingdoms Characters

Table:

Monera

Five Kingdoms Protista Eukaryotic

Fungi Eukaryotic

Plantae Eukaryotic

Animalia Eukaryotic

Non-cellulosic (Polysaccharide + amino acid) Nuclear membrane Absent

Present in some

Present (without cellulose) Present

Present (cellulose)

Absent

Present

Present

Body organisation

Cellular

Cellular

Tissue/organ

Tissue/organ/ organ system

Mode of nutrition

Autotrophic (chemosynthetic and photosynthetic) and heterotrophic (saprophyte/ parasite)

Autotrophic Heterotrophic (photosynthetic) (saprophytic/ and heterotrophic parasitic)

Cell type

Prokaryotic

Cell wall

Present

Multicellular/ loose tissue

Autotrophic Heterotrophic (Photosynthetic) (Holozoic/ Saprophytic etc.)

Shortcomings of five kingdom classification • The Kingdoms Monera and Protista are still heterogenous groups. Both include photosynthetic (autotrophic) and nonphotosynthetic (heterotrophic), walled and wall-less organisms. 30

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• Phylogenetic relationships, particularly of lower organisms, are not fully reflected. For example, certain green algae and some photosynthetic bacteria get hydrogen from sources other than water but these are assigned to different kingdoms. • A distinction between unicellular and multicellular organisms is not possible in case of algae. Due to this, unicellular green algae such as Chlamydomonas, Volvox, etc., have not been included in the Kingdom Protista. • Viruses have not been included in this system of classification. • Archaebacteria differ from other bacteria in structure, composition and physiology.

Three Domains of Life (Six Kingdom Classification) • The three-domain system was introduced by Carl Woese (1990) that divides cellular life forms into archaea, bacteria and eukarya domains. • It emphasises the separation of prokaryotes into two groups, originally called Eubacteria (now Bacteria) and Archaebacteria (now Archaea). • Thus, the three-domain system divides the monera into two ‘domains’, leaving the remaining eukaryotic kingdoms in the third domain. • It is actually a six kingdom classification.

Six Kingdom Classification Domain Archaea (Contains a single kingdom)

Domain Bacteria (Contains a single kingdom)

Kingdom Archaebacteria

Kingdom Eubacteria Kingdom Protista

Domain Eukarya (Contains four kingdoms)

Kingdom Fungi

Kingdom Plantae

Kingdom Animalia

KINGDOM MONERA • It is a kingdom of prokaryotes, therefore, also known as prokaryota. • Two major groups of monera include: Archaebacteria and Eubacteria. Eubacteria is further of two types : bacteria and cyanobacteria (blue green algae). • The true nucleus with nuclear membrane is absent in bacterial cell. The nuclear material consisting of naked DNA molecule is called as nucleoid. • A layer of slime over the cell wall is present in bacterial cell. It is usually composed of polysaccharides. • Bacterial cell wall consists of acetyl glucosamine, acetyl muramic acid and a peptide chain of four or five amino acids. All these chemicals together form a polymer called peptidoglycan. • A thin, elastic and selectively permeable plasma membrane is situated just internal to the cell wall in each bacterial cell. • In many bacteria the plasma membrane gives rise to infoldings called mesosomes which participate in the separation of replicated nucleoid and formation of septa during cell division. • The ribosomes in bacteria are of 70S type. • Many bacteria (e.g., E.coli) have accessory rings of DNA called plasmids in addition to bacterial chromosomes. The plasmid DNA replicates independently and maintain independent integrity. • The plasmids which temporarily get associated with nucleoid DNA are known as episomes. • Bacteria reproduce asexually by binary fission. • Sexual reproduction or genetic recombination in bacteria takes place by three methods: conjugation, transformation and transduction. • Based on their shape bacteria are grouped under four categories : the spherical coccus, the rod shaped bacillus, the comma shaped vibrio and the spiral spirillum. • Bacteria show both autotrophic and heterotrophic nutrition. • Autotrophic nutrition is of two types : chemosynthesis and photosynthesis. The bacteria performing these modes of nutrition are called chemoautotrophs and photoautotrophs respectively. MT BIOLOGY

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• Heterotrophic nutrition is of three types : saprotrophic, symbiotic and parasitic. • Archaebacteria are a group of most primitive prokaryotes characterised by the absence of peptidoglycan in their cell wall. • Archaebacteria are of three major types: methanogens, halophiles and thermoacidophiles. Methanogens are obligate anaerobes and produce methane in biogas fermenters, e.g., Methanobacterium, Methanococcus. Halophiles are”salt-loving“ bacteria as they are found in environment with a very high salt concentration. Thermoacidophiles live in extremely acidic environment that have extremely high temperatures. They are found in hot sulphur springs. • Cyanobacteria (blue-green algae) are photosynthetic prokaryotes that have evolved more than 3 billion years back and paved the path for evolution of aerobic forms, including aerobic bacteria.

Mycoplasma (PPLO) Mycoplasmas are the simplest and the smallest of the free living prokaryotes. The organisms are often called PPLOs (Pleuro pneumonia like organisms). A cell wall is absent and plasma membrane forms the outer boundary of the cell. Due to the absence of cell wall the organisms can change their shape and are called pleomorphic. Mycoplasmas are heterotrophic in their nutrition.

KINGDOM PROTISTA • Kingdom Protista includes all the unicellular eukaryotic organisms. Phylogenetically, the Kingdom Protista acts as a connecting link between the prokaryotic Kingdom Monera on one hand and the complex multicellular Kingdoms Fungi, Plantae and Animalia on the other hand. • These are microscopic unicellular and eukaryotic organisms with cosmopolitan habitat. Many protists are found in water bodies in the form of plankton. • Many forms have more than one similar or dissimilar nuclei. • The cell is surrounded by plasma membrane and well developed membrane bound organelles are present inside the cell. • Five modes of locomotion are recognised in the protista : pseudopodial, flagellar, ciliary, wriggling and mucilage propulsion. • Mode of nutrition may be photosynthetic, holozoic, saprotrophic, parasitic and symbiotic etc. • Most of free living protists perform aerobic respiration, however, the parasitic protists respire anaerobically. • Protists reproduce by both asexual and sexual methods. • The major groups of protists include chrysophytes, dinoflagellates, euglenoids, slime moulds and protozoans. • Chrysophytes include diatoms and golden algae. They are found in fresh water as well as in marine environments. • The cell walls of chrysophytes are embedded with silica and thus are indestructible. • Chrysophytes produce diatomaceous earth and are the chief ‘producers’ in the oceans. • Dinoflagellates are mostly marine and photosynthetic. They appear yellow, green, brown and blue or red depending on the main pigment present in their cells. • Majority of euglenoids are fresh water organisms found in stagnant water. A protein rich layer called pellicle is present instead of a cell well which makes their body flexible. • Euglenoids are photosynthetic in the presence of sunlight, however, when deprived of sunlight they behave like heterotrophs. • Slime moulds are saprophytic protists. They form an aggregate called plasmodium which may move and spread over several feet under favorable conditions. • Protozoans are heterotrophs and live as predators or parasites. They are considered to be primitive relatives of animals.

Major groups of protozoans Amoeboid protozoans : They live in freshwater, sea water or moist soil. They move and capture their prey with the help of pseudopodia. Some of them such as Entamoeba are parasites. Flagellated protozoans : The members of this group are either free-living or parasitic. They have flagella. The parasitic forms such as Trypanosoma cause disease called sleeping sickness. Ciliated protozoans : These are aquatic and actively moving organisms because of presence of thousands of cilia, e.g., Paramecium. Sporozoans : These include diverse organisms that have an infectious spore-like stage in their life cycle, e.g., Plasmodium. 32

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1. 2. 3.

Which group of protista is photosynthetic in the presence of sunlight and behave like heterotrophs when deprived of sunlight? How does archaebacteria differ from eubacteria? Why phylogenetic system of classification is considered as highly dynamic?

KINGDOM FUNGI • They are achlorophyllous, heterotrophic, spore-forming, non-vascular, eukaryotic organisms which often contain chitin or fungal cellulose in their cell walls and possess glycogen as food reserve. • They have absorptive type of nutrition and are parasites or saprotrophs. • The body of fungus is filamentous and is called mycelium. The filaments are known as hyphae. • Hyphae are either multicellular or multinucleate. • Reproduction is of three types : sexual, vegetative and asexual. • Vegetative reproduction occurs by budding, fission, fragmentation, sclerotia and rhizomorphs. • Asexual reproduction occurs through the formation of different type of spores. • Sexual reproduction occurs by planogametic copulation, gametangial contact, gametangial copulation, spermatogamy and somatogamy. • Kingdom Fungi is classified as follows :

Kingdom Fungi Sexual reproduction not known Fungi Imperfecti or Deuteromycota

Sexual reproduction known Mycelium aseptate Phycomycota (lower or algal fungi) Oomycetes (Oogamous fungi)

Zygomycetes (Conjugation fungi)

Mycelium septate Eumycota (Higher fungi) Ascomycetes (Sac fungi)

Basidiomycetes (Club fungi)

• In oomycetes the mycelium is coenocytic (multinucleate and aseptate). • Asexual reproduction involves the formation of spore containing sacs or sporangia which produce zoospores in aquatic environment. In terrestrial environment, the sporangia often behave as spores and equivalent to conidia. • Zoospores are usually biflagellate. • Gametes are usually nonflagellate. • Sexual reproduction takes place by gametangial contact and the product of sexual reproduction is oospore. • Some examples are Albugo candida, Phytophthora infestans, Pythium debaryanum. • Zygomycetes is a class of terrestrial fungi which are mostly saprotrophic, rarely parasitic. • The mycelium is coenocytic. • Motile cells are absent. Sexual reproduction occurs through gametangial copulation or conjugation. MT BIOLOGY

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• • • • • • •

• • • • • • • • • • • • • • • • • •

The gametes are multinucleate and are called coenogametes. Analysis of various PMTs from 2013-2017 AIPMT/NEET 10 Sexual reproduction produces a diploid spore called zygospore. AIIMS 9 Some examples are Rhizopus stolonifer, Mucor pusillus, Pilobolus crystallinus. JIPMER Ascomycetes include pigmented moulds, yeasts, morels, truffles, cup fungi 8 7 and powdery mildews. 6 The mycelium consists of septate hyphae. 5 Motile structures do not occur in the life cycle. 4 The common mode of asexual reproduction is through the formation of 3 conidia. However, in yeasts asexual reproduction occurs through budding and 2 fission. Oidia stage is found in some other ascomycetes. 1 Sexual reproduction takes place through gametangial contact. 2013 2014 2015 2016 2017 Fertilisation takes place in two steps plasmogamy and karyogamy. Karyogamy is delayed after plasmogamy and a new transitional phase called dikaryophase appears in the life cycle. The cells of dikaryophase are called dikaryotic cells. Each cell possesses two nuclei (n + n). Later the two nuclei fuse and the cells become diploid. The fungi form fruiting bodies, in which reduction division occurs, leading to formation of haploid spores. Some examples are yeast, Aspergillus, Penicillium, Claviceps and Neurospora. Basidiomycetes grow in soil on logs and in living plant bodies as parasites. The mycelium is septate and branched. Septa have dolipores (pores with barrel shaped outgrowths). Vegetative reproduction occurs by fragmentation. The asexual spores are not found. The sex organs are absent but plasmogamy is brought about by fusion of two vegetative or somatic cells of different strains or genotypes. The resultant structure is dikaryotic which gives rise to basidium. Karyogamy and meiosis takes place in the basidium producing four basidiospores. Some examples are Agaricus, Ustilago and Puccinia. Deuteromycetes are commonly known as imperfect fungi because only the asexual or vegetative phases of these fungi are known. Some members of deuteromycetes are saprophytes or parasites while a large number of them are decomposers of litter and help in mineral cycling. The mycelium is septate and branched. The deuteromycetes reproduce only by asexual spores known as conidia. Some examples are Trichoderma, Alternaria and Colletotrichum.

Most fungi are heterotrophic and absorb soluble organic matter from dead substrates and hence are called saprophytes. Those fungi depend on living plants and animals are called parasites. They can also live as symbionts i.e., in association with algae as lichens and with roots of higher plants as mycorrhiza.

KINGDOM PLANTAE • • • •

It includes all eukaryotic chlorophyll containing organisms commonly called plants. A few members such as bladderwort and Venus fly trap are insectivorous while few others such as Cuscuta are parasitic. Kingdom Plantae includes algae, bryophytes, pteridophytes, gymnosperms and angiosperms. Two distinct phases are present in life cycle of plants : the diploid sporophytic phase and the haploid gametophytic phase that alternate with each other. • These two phases follow each other rigidly but in different patterns in different plant groups. This phenomenon is called alternation of generation.

KINGDOM ANIMALIA • This kingdom is characterised by heterotrophic, eukaryotic organisms that are multicellular and their cells lack cell walls. • They depend directly or indirectly on plants for food. The mode of nutrition is by ingestion of food, i.e., holozoic. 34

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• • • •

The food reserves are stored as glycogen or fat. Most of them are capable of locomotion. They have a definite shape and size and follow a definite growth pattern also. The sexual reproduction takes place by copulation of male and female followed by embryological development.

VIRUSES, VIROIDS AND LICHENS • The name virus was given by Pasteur. D.J. Ivanowsky (1892) is credited with the discovery of virus. Beijerinck (1896), called it contagium vivum fluidum. • The viruses are ultramicroscopic, highly infectious agents and non-cellular organisms characterised by having an inert crystalline structure outside the living cell. • Once they infect a cell they take over the machinery of the host cell to replicate themselves, killing the host. • Viruses contain capsid, the proteinaceous covering and genetic material, that could be either DNA or RNA. • Viruses that infect plants have single stranded RNA while those that infect animals have either single or double stranded RNA or double stranded DNA. Bacteriophages are usually double stranded DNA viruses. • In humans, viruses cause diseases like mumps, smallpox, herpes, influenza and AIDS. • In plants, the symptoms of virus infection can be mosaic formation, leaf rolling, yellowing, leaf curling and stunted growth. • Stanley (1935) crystallised Tobacco Mosaic Virus (TMV) for the first time. • An inert virus is called virion that can be crystallised and stored indefinitely. • Viroids are the smallest self replicating particles discovered by Diener (1971). • Viroids are infectious RNA particles devoid of protein coat. • Like viruses, they are obligate parasites. • Viroids are known to cause diseases in plants only, e.g., Potato spindle tuber chrysanthemum stunt. • Lichens are dual organisms or entities which contain a permanent association of a fungus or mycobiont and an alga or phycobiont. • The algal component is autotrophic while fungal component is heterotrophic. • Algae prepare food for fungi and fungi provide shelter and absorb mineral nutrients and water for algae. • Lichens cannot tolerate air pollution especially due to sulphur dioxide. Prions are highly resistant glycoprotein particles which function as infectious agents. Prions are not affected by proteases, nucleases, temperature upto 800°C, UV radiation and formaldehyde. Prions accumulate in nervous tissue and bring about its degeneration. Common diseases caused by them are mad cow disease, scrapie of sheep, kuru, Creutzfeldt-Jakob disease (CJD). Prions were discovered by Prusiner (1983).

4.

Name the scientist who crystallised Tobacco Mosaic Virus (TMV) for the first time.

5.

Why deuteromycetes are called imperfect fungi?

6.

Mention various methods by which sexual reproduction takes place in fungi.

ANSWERS

WHO AM I ...

1.

Mycoplasma

Pg. 33

2.

Phycoerythrin

Pg. 39

3.

Prothallus

Pg. 41

4.

Pollen mother cell

Pg. 62

Winner April 2018 1. Ann Madona Shaju- Calicut, Kerala

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Plant Kingdom • The Kingdom Plantae includes eukaryotic, photosynthetic organisms. According to traditional systems of classification, the Kingdom Plantae is divided into two subkingdoms : Cryptogamae and Phanerogamae. Cryptogamae is further divided into algae, bryophyta and pteridophyta, while phanerogamae is further divided into gymnospermae and angiospermae.

Kingdom Plantae Cryptogamae

• Plants called cryptogams do not bear conspicuous reproductive structures like seeds i.e., seedless plants.

• Plant body is not well organised and do not bear flowers, fruits and seeds. • The reproductive structures or sex organs are invisible.

Bryophyta

Algae

• Plant body is undifferentiated and is known as thallus.

• It may range from microscopic unicellular to macroscopic multicellular forms. • The plants are non-vascular and chlorophyllous.

• • • •

Phanerogamae Phanerogams are flowering or seed plants. The plant body is differentiated into root, stem and leaves. They bear visible reproductive structures like cones and flowers. There are vascular plant.

Pteridophyta

• Represent group of • Referred as first land plants growing in amphibious habitat. • They are simpler and smaller embryophytes.

plants or vascular cryptogams as they possess xylem and phloem.

Gymnospermae • Naked seed bearing plants. • Flowers are absent. • Vascular tissue are present, xylem vessels are absent.

Angiospermae

• Plants bear covered seeds and fruits. Most evolved group of plant kingdom. • Vascular tissue contains xylem vessels. • Double fertilisation occurs.

ALGAE • Algae are chlorophyllous thallophytes characterised by the absence of embryo stage and presence of non-jacketed gametangia. • These are usually aquatic, either marine or fresh water, a few algae occur in moist terrestrial habitat. • Algae are covered by mucilage which protects them from epiphytic growth and decaying effect of water and also prevents desiccation. • Vascular tissues and mechanical tissues are absent. • Algae mainly contain chlorophyll a, carotenes and xanthophylls. • Algae are usually classified on the basis of their pigments, flagellation and storage products. • According to Whittaker (1969), algae are of three types : red algae (Rhodophyta), brown algae (Phaeophyta) and green algae (Chlorophyta). • Vegetative, asexual and sexual modes of reproduction are present. • Vegetative reproduction may take place by fragmentation (e.g., Ulothrix, Oedogonium), fission (e.g.,Chlamydomonas), hormogonia (e.g., Oscillatoria), tubers (e.g., Chara), budding (e.g., Polysiphonia), etc. • Asexual reproduction takes place by flagellated zoospores (e.g., Ulothrix, Oedogonium); non-motile, thin walled aplanospore (e.g., Chlorella, Microspora) and non-motile, thick walled hypnospores (e.g., Vaucheria, Chlamydomonas nivalis, thick walled akinetes (e.g., Cladophora), palmella stage (e.g., Chlamydomonas). • Sexual reproduction involves isogamy, anisogamy and oogamy in different groups. • Life cycle may be haplontic, diplontic or diplohaplontic.

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Table :

Characteristics of different classes of algae

Classes

Structure

Occurrence

Major pigments

Reserve food material True starch and sugar

Chlorophyceae, (Green algae) e.g., Spirogyra, Ulothrix

Unicellular to heterotrichous filaments. Cellulosic cell wall, starch sheathed pyrenoids, motile cells with 2-4 equal flagella.

Chl. a and b, Mostly fresh water a few are carotenes and marine. A marked xanthophyll tendency towards terrestrial habitat.

Phaeophyceae (Brown algae) e.g., Fucus, Sargassum

Simple filamentous to bulky parenchymatous with giant size, external and internal differentiation, motile cells with 2 lateral flagella. Simple filamentous to complex forms, motile cells are not known.

Mostly marine

Fucoxanthin, flavoxanthin, b-carotenes, Chl. a and c.

Few freshwater, others are marine.

Phycoerythrins, Floridean phycocyanin, starch allophycocyanin, carotenoids, Chl. a and d.

Rhodophyceae (Red algae) e.g., Polysiphonia, Porphyra

Laminarin, mannitol

Reproduction Vegetative

Asexual

Sexual

Fragmentation Zoospores or fission

Isogamous to advanced oogamous

Fragmentation Zoospores, is most tetraspores common etc.

Isogamous to oogamous

Uncommon, except unicellular ones

Advanced oogamous type producing special carpospores.

Monospores, carpospores, polyspores etc.

Economic Importance of Algae • Marine algae such as Laminaria, Sargassum are used as food. • Algae are primary producers of food in large bodies of water and thus form the basis of food cycles of all aquatic animals. • Agar obtained from Gelidium and Gracilaria is used as a culture medium. • Algae such as Chlamydomonas, Chlorella are used in sewage oxidation tanks and provide aerobic conditions for disposal of sewage by decomposers.

BRYOPHYTES

Analysis of various PMTs from 2013-2017 AIPMT/NEET AIIMS JIPMER

5 4 3 2 1

2013 2014 2015 2016 2017 • Bryophytes are most primitive non-vascular terrestrial plants of moist habitats in which a multicellular diploid sporophyte is completely dependent on an independent multicellular haploid gametophyte. • They are called “amphibians of plant kingdom” because although they are terrestrial plants fundamentally but require presence of water to complete their life cycle. • Bryophytes are divided into three classes - hepaticopsida (liverworts), anthocerotopsida (hornworts) and bryopsida (mosses). • The dominant phase of the plant is a free living gametophyte. • The gametophytes are either thalloid (not differentiated into true roots, stem and leaves) or leafy shoot having stem-like central axis and leaf-like appendages. • The vascular tissues are completely absent. • Rhizoids are present instead of roots which may be unicellular or multicellular. • Vegetative reproduction occurs through fragmentation, tubers, gemmae, e.g., Marchantia, adventitious branches, e.g., Riccia. • Two types of sex organs are present male antheridium and female archegonium. Both are multicellular and jacketed. • Antheridium produces a number of flagellate male gametes called sperms or antherozoids. • Archegonium is flask-shaped with tubular neck and a swollen venter. • The venter encloses a venter cavity having a sterile venter canal cell and a fertile egg or oosphere. • An external layer of water is essential for the swimming of male gametes to the archegonia. MT BIOLOGY

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• • • • •

Embryo stage is present. The embryo grows into a sporophyte. The sporophyte consists of foot, seta and capsule. Sporophyte produces haploid meiospores inside its capsule. Each spore on germination produces a gametophyte, either directly or a juvenile filamentous stage celled protonema. Bryophytes show heteromorphic or heterologous alternation of generations.

Characteristics of different classes of bryophytes Features Hepaticopsida Anthocerotopsida Common name Liverworts Hornworts Gametophytic plant May be thallose or foliose, Thallose, Unicellular rhizoids. aseptate rhizoids body Table :

Sex organs Sporophyte or sporogonium

Elaters Sporogenous cells

Present on dorsal surface of thallus. Simple, represented by capsule only e.g., Riccia or differentiated into foot, seta and capsule (e.g., Marchantia). Generally present, absent in some like Riccia. Develops from endothecium.

Dehiscence of capsule Irregular and indefinite Riccia, Marchantia, Examples Sphaerocarpos, etc.

Present on dorsal surface of thallus. Differentiated into a bulbous foot, small meristematic seta and long cylindrical capsule. Pseudoelaters are present in the capsule. Develops from amphithecium and endothecium, forms sterile columella. Irregular Anthoceros, Notothylus, Megaceros, etc.

Bryopsida Mosses Gametophyte has two growth stages: thalloid protonema stage and leafy gametophore stage. Obliquely septate rhizoids. Develop from the superficial cells at the apex of leafy gametophore. Differentiated into foot, seta and capsule.

Absent Develops from outer layer of endothecium, inner layer forms sterile columella. Regular Sphagnum, Polytrichum, Funaria, etc.

Economic Importance of Bryophytes • Bryophytes such as mosses prevent soil erosion by forming dense mats over the soil surface. • Dry Sphagnum can keep seedlings and cut plants moist during transportation and propagation as it can absorb 18-26 times its weight of water. • Mosses alongwith lichens play a very important role in the formation of soil over the bare rocky surface. • Some bryophytes have important medicinal uses. For example, the tea prepared from Polytrichum commune is used to dissolve stones of kidney and gall bladder. Bryophytes seldom attain great heights and thus remain small in size. It may be due to absence of roots and vascular tissues, absence of cuticle on plant body, absence of mechanical tissues and requirement of external sheet of water for capillary conduction.

PTERIDOPHYTES • • • • •

Pteridophytes are seedless vascular plants that have sporophytic plant body and inconspicuous gametophytes. The sporophyte is differentiated into true roots, stem and leaves. All the vegetative parts possess vascular tissues (xylem and phloem) organised in definite groups or steles. The sporophyte reproduces asexually by means of spores, produced in small capsules called sporangia. Leaves bearing sporangia are called sporophylls which may be widely scattered or clustered in definite areas and structures called cones or strobili. • The diploid spore mother cells or sporocytes within the sporangia undergo meiosis to form haploid spores. • The spores produced are of only one type in homosporous pteridophytes (e.g., Lycopodium, Pteridium) or of two types (smaller microspores and larger megaspore) in heterosporous pteridophytes (e.g., Selaginella, Marsilea). 38

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• The spores germinate to produce haploid gametophyte, called prothallus. • The homosporous pteridophytes produce bisexual gametophytes (both antheridia and archegonia are borne on same prothallus) whereas heterosporous ones produce unisexual (antheridia and archegonia develop on separate male and female prothallus) gametophytes. • The sexual reproduction is oogamous. • Antheridia are small and sessile male sex organs comprising of androcytes each of which produces a male antherozoid. Archegonia are female sex organs partially embedded and consists of 4-rowed neck. • Water is essential for fertilisation, as it assists in carrying bi-or multiflagellate sperms to archegonia. • The diploid zygote formed after fertilisation develops into an embryo which remains attached to the gametophyte and gets nourishment during its early stage of development. • Pteridophytes exhibit alternate succession of sporophytic and gametophytic generation. • Pteridophytes can be classified into following types:

Pteridophyta

Psilophyta

• These are oldest known land inhabiting plants.

• Rootless, rhizoids

are present. • Homosporous • Most plants are fossils, e.g., Rhynia, Horneophyton etc.

Lycophyta

Sphenophyta

Pterophyta/Filicophyta

• Commonly called club

• At nodes, whorls of small

• Roots, stem and leaves

• Deposition of silica in stems

are present. • Members are microphyllous. • Homosporous (Lycopodium) or heterosporous (Selaginella).

make them rough in touch. • Ridges and grooves are found in stem. • Always homosporous, e.g., Equisetum.

mosses or spike mosses.

leaves are present.

• Fan like leaves. • Stem is in the form of rhizome.

• May be homosporous (Dryopteris, Pteris) or heterosporous (Marsilea).

Economic Importance of Pteridophytes • Many ferns are grown as ornamental plants in gardens for their large, showy and graceful foliage. • An anti-helminthic drug is obtained from the rhizomes and petioles of Dryopteris. Adiantum roots are used to cure throat infections. Lycopodium is used in treatment of rheumatism and disorders of lungs and kidneys. • The sporocarps of Marsilea are rich source of starch and eaten for their nutritive value by some tribals.

Evolution of Seed Habit • The ability of plant to form seed is called seed habit. It is considered to be originated in pteridosperms during Devoniancarboniferous periods. The development of zygote into young embryo within female gametophyte in heterosporous plants e.g., Selaginella is a precursor to the evolution of seed habit. • The differentiation of spores into microspores and megaspores and their dependence on the parent sporophyte for the nutrition are certain features considered as pre-requisites for the formation of seeds.

1.

Name the major pigments present in the following algae: Sargassum, Ulothrix, Porphyra.

2.

Bryophytes remain small sized and seldom attain great heights. Give reasons.

3.

Give an example of (a) homosporous pteridophyte (b) heterosporous pteridophyte. MT BIOLOGY

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GYMNOSPERMS

• Gymnosperms are seed plants in which the seeds remain exposed over the surface of the megasporophylls. • The plant body is differentiated into root, stem and leaves. • The plants possess well developed tap root system. In some cases, the roots are symbiotically associated with algae (e.g., coralloid roots of Cycas) or with fungus (e.g., mycorrhizal roots of Pinus). • The stem is erect, aerial, solid, woody and branched. The gymnosperms include world’s tallest tree-Sequoia sempervirens measuring about 125m in height and 30m in girth. The smallest gymnosperm is Zamia pygmaea, which has underground tuberous stem. It reaches only upto 25cm in height. • The vascular tissues, xylem and phloem are present. They are arranged in vascular bundles. The vascular bundles of stem are conjoint, collateral and open. Xylem vessels are absent. • Secondary growth occurs and annual rings are distinct in most of the gymnosperms. • Gymnosperms are heterosporous. • The two types of sporangia are borne on special leaf-like structures called sporophylls. The microsporangia are borne on microsporophylls (= stamens) and the megasporangia on megasporophylls (= carpels). • The sporophylls are aggregated in the form of cones or strobili. • The microsporangium produces numerous light pollen grains. • Pollination is anemophilous. Some of the pollen grains come in direct contact with the micropylar end of ovules and reach upto the nucellus. • Fertilisation occurs by siphonogamy, i.e., the male gametes reaches the female gamete by forming a tube. • The diploid zygote, develops into an embryo while still enclosed within the ovule and the ovule becomes a seed. • During seed development, the endosperm (haploid) supplies nutrients to the developing embryo. • The seeds of gymnosperm are naked and remain attached to the megasporophyll. • Polyembryony is common in Pinus. The number of cotyledons may be one or two or a whorl of many. • Gymnosperms can be classified into following types:

Gymnosperms • • • • • •

Cycadopsida Primitive group, represented by small plants. Wood is manoxylic. Male cones are large with compactly arranged microsporophylls. Megasporophylls are loosely arranged in female cone. Seeds are radially symmetrical. Examples : Cycas, Zamia, etc.

Coniferopsida

• Includes larger dominant • • • •

gymnosperms. Wood is pycnoxylic. Sporophylls form cones. Seeds are bilaterally symmetrical. Examples : Pinus, Ginkgo, Taxus.

Gnetopsida

• Includes advanced gymnosperms. • Secondary xylem shows vessels. • Ovules are orthotropous with long tubular micropyle.

• Examples : Order Gnetales (Gnetum, Ephedra, Welwitschia)

Economic Importance of Gymnosperms • Gymnosperms are a very good source of resins. The resins are oxidation products of various essential oils containing terpenes, resin acids and esters. The resins are utilised commercially in the manufacture of varnishes, waterproof paints, sealing wax etc. • Seeds of Pinus gerardiana are used as dry fruits, called chilgoza. • Ephedrine, a drug is obtained from Ephedra. It is used in the treatment of cough, asthma and bronchitis. • Leaves of Cycas and Thuja are extensively used in the floral decorations.

Adaptations to land

Seed plants, i.e., gymnosperms and angiosperms are the most successful of all the land plants. They are well adapted to land conditions because of the following features. – Presence of extensive underground root system for anchoring and absorption of water and minerals. – Presence of vascular tissue system for conduction of water and minerals. – Well developed mechanical tissue system. – Development of cambium for secondary growth in thickness. – Production of pollen grains in large number. – Transformation of megasporangium into ovule and development of female gametophyte inside the ovule. – Presence of external water is not required for fertilisation. – Zygote develops within the ovule to form an embryo. 40

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ANGIOSPERMS • • • • • • • • • • • • • • •

•

• • •

Angiosperms are seed plants in which seeds are formed inside fruits and the sporophylls are organised into flowers. Angiosperms are the most recently and highly evolved plants. Angiosperms are found in most environments on the earth. Plant body is sporophytic and represented by herbs, shrubs, trees, twiners, trailers, climbers, etc. Sporophytic plant body is differentiated into roots, stem and leaves. Depending upon the number of cotyledons (embryonic leaves) in the seeds, angiosperms are divided into two subgroups : dicotyledonous and monocotyledonous plants. Xylem contains vessels and phloem possesses sieve tubes and companion cells. Secondary growth occurs in root and stem of dicots. Sporophylls are aggregated to form flowers. Both microsporophylls and megasporophylls are specialised to form stamen and carpel producing male and female gametes respectively. Female gametophyte is represented by embryo sac. All the cells of embryo sac are haploid. Pollination takes place by several agencies such as air, water, birds, insects, bats, etc. The flowers possess showy petals, edible pollen and nectar to attract various pollinating agents. Pollen grains or microspores reach stigmatic surface found at the tip of carpel or megasporophyll. Embryo sac develops upto 8-nucleate state before fertilisation.There is a three cell egg apparatus, three antipodal cells and two polar nuclei. Double fertilisation is characteristic feature of angiosperms. One of the two male gametes, fuses with egg to form zygote while other fuses with central cell to form primary endosperm nucleus (PEN). Central cell containing triploid primary endosperm nucleus forms triploid endosperm. Endosperm provides nourishment to developing embryo. Synergids and antipodals degenerate after fertilisation. Fertilised ovules ripen into seeds. The seeds are covered by fruits. A fruit is a ripened ovary which not only protects the seeds but also help in their dispersal.

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Table: Comparison between dicots and monocots Features Cotyledons Flowers Pollen grains

Dicots Usually two Penta or tetramerous Three germ pores

Leaf venation Primary root

Reticulate Often long lived forming tap root system. Adventitious roots occur in some. Stem tissue Concentric arrangement of epidermis, cortex, endodermis, pericycle, pith, etc. Vascular bundles of stem In a ring, cambium (open), thus secondary growth present. Root Pith absent or small. Vascular bundles 8 or less. Xylem vessels Polygonal

Monocots One cotyledon Trimerous Single germinal furrow Parallel except a few Short-lived Tap roots absent, instead adventitious roots are found. Undifferentiated, a ground tissue occurs. Scattered, cambium is absent (closed). Pith present. Vascular bundles more than 8. Rounded

Flowering plants or angiosperms have exploited insects, birds and several other animals as agents of pollination, fruit and seed dispersal. It is one major reason for present day dominance of flowering plants.

ALTERNATION OF GENERATION • During the life cycle of sexually reproducing plants, there is an alternation between gamete producing haploid gametophyte and spore producing diploid sporophyte. • Different plant groups as well as individuals representing them, differ in the following patterns : • Haplontic life cycle - Sporophytic generation is represented by one-celled zygote. Meiosis in zygote results in the formation of haploid spores. The haploid spore forms free living gametophyte by mitosis. It is represented by many algae such as Volvox, Spirogyra and Chlamydomonas. • Diplontic life cycle - Diploid sporophyte is dominant, photosynthetic and independent phase of the plant. The gametophytic phase is represented by the single to fewcelled haploid gametophyte. All seed bearing plants, i.e., gymnosperms and angiosperms and an alga Fucus exhibit this kind of pattern. • Haplodiplontic life cycle - Bryophytes and pteridophytes exhibit this kind of pattern. In bryophytes, a dominant independent, photosynthetic, thalloid phase is represented by a gametophyte and it alternates with short-lived multicellular sporophyte totally or partially dependent on the gametophyte for its anchorage and nutrition. • In pteridophytes, the diploid sporophyte is represented by a dominant, independent, photosynthetic, vascular plant body. It alternates with multicellular, saprophytic / autotrophic, independent but short-lived haploid gametophyte. • Some algal genera such as Ectocarpus and Polysiphonia are also haplodiplontic.

4.

5. 6. 42

What is the meaning of alternation of generation in plants? Briefly describe diplontic life cycle with examples. What is double fertilisation? It is a characteristic feature of which group of plants? Give the characteristic features of cycadopsida. MT BIOLOGY

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CHECK YOUR

ITALS

POOR

GOOD

for NEET, AIIMS and JIPMER Maximise your chance of success in medical entrance exams by reading this article. This section is specially designed to optimise your preparation by practising more and more. It is a unitwise series having chapterwise question bank, allowing you to prepare systematically and become more competent. Recall question or single concept question – indicated by a single finger. Application question or question which requires 2 or 3 concepts - indicated by 2 fingers. Application question or question which requires 3 or more concepts - indicated by 3 fingers.

UNIT-I : DIVERSITY OF THE LIVING WORLD CHAPTER-1 : THE LIVING WORLD

Multiple Choice Questions 1. Select the option which correctly fills the given blanks. I. ______ contains instructions about occurrence, collection and identification of species that occurs in a specific area. II. The booklet that contains list of characters with their alternates that help in identification of various taxa is called a ______ . III. ______ provides information about a particular taxon such as an order or family. I II III (a) Catalogue monograph Flora (b) Monograph catalogue Key (c) Manual Key Monograph (d) Key flora Manual 2. Which of the following statement is incorrect with respect to modern taxonomy? (a) Primitiveness, inter-relationships and advancement of species are studied under it. (b) It has a population or biosystematic concept. (c) All types of variations in the species are systematically studied under modern taxonomy. (d) Species are delimited on the basis of morphological characters and are also considered to be immutable. 3. The defining properties that differentiate living organisms from non-living, without an exception, are (a) cellular organisation, reproduction and movement

(b) (c) (d)

cellular organisation, metabolism and consciousness metabolism, growth and reproduction reproduction, metabolism and consciousness.

4. According to taxonomic hierarchy, (a) Felis and Canis are placed under the same family (b) potato and brinjal belong to the same genus (c) classes of plants with few similar characters are assigned to higher category called order (d) Panthera leo and Felis domestica are placed in different families. 5. In the scientific name Ficus benghalensis L., the appended abbreviation L., signifies (a) the name of the scientist who discovered the organism and provided it with a scientific name. (b) the scientific name was derived from Latin (c) the variety of the banyan tree (d) the revised specific epithet after it was recategorised. 6. Consider the following statements and select the correct option stating which ones are true (T) and which ones are false (F) regarding binomial nomenclature. I. Scientific names are derived from Latin or latinised as the language will not change in form or spellings with time. II. Vernacular names cannot be used by scientists as they can be misleading. III. Julian Huxley defined species as an assemblage of individuals with similar parentage and having ability to pass the parental traits to the offspring. MT BIOLOGY

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IV. (a) (b) (c) (d)

First botanical garden was established by Hippocrates. I II III IV T T F T T F F T T T F F F T T T

7. Which of the following is not a criterion for delimiting a species in a population? (a) All members of the species have the ability to interbreed freely. (b) All members have a common ancestor. (c) All the members have complete anatomical similarity. (d) All the individuals have the same genetic makeup. 8. Select the option with a mismatched taxonomic category for Magnifera indica. (a) Order - Sapindales (b) Class - Anacardiaceae (c) Genus - Magnifera (d) Division - Angiospermae 9. The set of two contrasting characters in a key which are used for identification of organisms is called a (a) lead (b) couplet (c) diad (d) doublet. 10.A scientist discovered a new plant species which according to him, might not have been classified in the past. The taxonomic aid he is most likely to use for the identification of species is (a) manual (b) museum (c) herbarium (d) key. 11.Which of the following options exclusively contains obligate categories of taxonomic hierarchy? (a) Kingdom, class, species, family, variety (b) Phylum, Division, family, tribe, genus (c) Order, phylum, subphylum, subspecies, species (d) Class, division, genus, family, phylum 12.Read the following statements and select the incorrect option. (a) Zoological parks are very useful in spreading knowledge on the wildlife wealth of the country. (b) Zoological parks are established where standard care of animals is not observed. (c) In the zoological park, animals feel safe from their natural enemies. (d) Zoological parks have been involved in the rescue of many species threatened with extinction. 13.Reproduction is not an all inclusive criterion for defining living things because (a) asexual reproduction exists in nature (b) reproduction is not essential for the survival of individual (c) occasionally sterile hybrids occur in nature (d) some organisms like Amoeba divide into daughter cells hence considered immortal. 44

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14.According to the taxonomic hierarchy, the members of ______ will have least number of similarities whereas ______ will have maximum number of similarities in the characters. (a) kingdom, species (b) species, kingdom (c) genus, kingdom (d) family, phylum 15.Select the incorrect statement among the following. (a) Each statement of the key is called lead. (b) The primary purpose of museums is to preserve selected objects. (c) According to ICBN, the names of families and subfamilies should be based on name of type species. (d) Growing important plants of local flora is an important function of botanical garden.

Match The Columns 16. Match Column I with Column II. Column I Column II A. Theophrastus (i) Historia Naturalis B. Carolus Linnaeus (ii) Species Plantarum C. John Ray (iii) Historia Plantarum D. Pliny the Elder (iv) Historia Generalis Plantarum 17. Match Column I with Column II. (There can be more than one match for items in Column I). Column I Column II A. Binomial (i) National Botanical nomenclature Research Institute B. Botanical garden (ii) Scientific name C. Vernacular nomenclature (iii) Live plant specimens D. Herbarium (iv) Universal application (v) Museum of Natural History, Paris (vi) Carolus Linnaeus (vii) Vasculum (viii)Touch-me-not

Passage Based Questions 18.(A)Complete the given passage with appropriate words or phrases. The diversity in the living world has made it essential to have a universal system of (i) , (ii) and classification that helps in understanding of the relationships among organisms. These all form the domains of (iii) which is often used interchangeably with taxonomy. Through (i) each organism is given two word name (iv) and (v) . Two (vi) belonging to same (vii) cannot have similar (v) name. The original scientific names were taken from (viii) or (ix) languages. The name of the author is kept in (x) script.

(B) Read the given passage and correct the errors, wherever present. Herbarium is a place where fresh plant specimens, mounted on sheets are kept randomly. Herbarium is a repository for present use. It provides information about the local flora only and also about the ecology of different places. Herbaria are used for correct and authentic identification of known plants. It depicts the anatomical variations found in species.

Assertion & Reason In each of the following questions, a statement of Assertion (A) is given and a corresponding statement of Reason (R) is given just below it. Of the statements, mark the correct answer as : (a) if both A and R are true and R is the correct explanation of A (b) if both A and R are true but R is not the correct explanation of A (c) if A is true but R is false (d) if both A and R are false. 19. Assertion : All organisms reproduce for perpetuation of a population. Reason : Reproduction is an all inclusive characteristic of living organisms. 20. Assertion : Solanum is a polytypic genus. Reason : Solanum has a large number of closely related species, such as S. nigrum, S. tuberosum, S. melongena, etc. 21. Assertion : Cats and dogs have some similarities. Reason : Cats and dogs belong to the same Family Canidae. 22. Assertion : Classical taxonomy studies evolution and inter-relationships of species.

Reason : Organisms are identified according to binomial nomenclature. 28. Assertion : Every new objects that are added in a museum to its collection is called an acquisition. Reason : Method of acquisition and other information are entered in a record register.

Figure Based Questions 29. Refer to the given figure and answer the following questions. D C Class B A Genus Species (a) Identify A, B, C and D in the given figure. (b) Define B in the given figure. (c) Give the name of A, B and C for the genus Triticum and Felis. 30. Refer to the given flow chart and answer the following questions.

Reason : Classical taxonomy considers species to be dynamic. 23. Assertion : Petunia and Datura show some similarities. Reason : Petunia and Datura are placed in the same Family Brassicaceae. 24. Assertion : Systematics is the branch of biology that deals with classification of organisms. Reason : Aim of classification is to group the organisms in an orderly manner. 25. Assertion : Suborder is an intermediate category. Reason : Intermediate categories do not have any specific function in taxonomic hierarchy. 26. Assertion : Class is a taxonomic category that includes one or more families. Reason : All the families in a class have some similar features and correlated characters. 27. Assertion : Both the generic and specific name in a binomial nomenclature are written in italics or underlined.

(a) In the given flow chart A, B, C, D and E represent the characteristics features of herbarium, botanical garden, zoological park, museum and key respectively. Write the best suitable statements for A, B, C, D and E. (b) Identify the suitable words for (i), (ii), (iii), (iv), (v) and (vi). MT BIOLOGY

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Parasexual Cycle in Deuteromycotina

DEUTEROMYCOTINA : THE FUNGI IMPERFECTI

•• Parasexual cycle was first discovered by Pontecorvo and Roper of University of Glasgow in 1952 in Aspergillus nidulans the, imperfect stage of

The Subdivision Deuteromycotina includes those fungi in which only asexual or imperfect stages are known and sexual or perfect stages are not yet recorded. They are also called Fungi imperfecti. This subdivision includes about 600 genera and over 20,000 species, but this number is now decreasing as members previously included in Deuteromycotina are being transferred to appropriate groups as soon as their perfect sexual stages are discovered. Thus, this subdivision is a purely artificial and temporary assemblage of fungal species waiting to be included in appropriate groups after the discovery of their perfect stages.

General Characteristics of Deuteromycotina •• The members belonging to this group are saprophytes or parasites. •• The mycelium is well developed and profusely branched with perforated septa. •• The hyphae may be inter or intracellular and the cells are multinucleate. •• The reproduction takes place by asexual means only and sexual stages are not known. •• Asexual reproduction takes place by oidia or conidia formation. The conidia are non-motile structures which develop exogenously on conidiophores. •• Conidiophores are either free or are formed in some special types of fruiting bodies such as synnemata, acervuli, sporodochia and pycnidia. •• Some members show parasexuality.

Fruiting Bodies Synnema feather cluster or a brush. •• Branched or unbranched conidiophores arise very close to each other and are often united along a greater part of their length to form dense fascicles. •• This type of arrangement of conidiophores is given the name corenium or synnema. •• Towards the upper end of synnema the conidiophores become free and diverge to give rise to conidia.

Sporodochium

•• Sporodochium is

a hemispherical or barrel-shaped asexual fruiting body. Its lower or the basal part is a cushioned stoma like mass of hyphae. •• Conidiophores constitute the upper part of sporodochium bearing conidia. Conidia

Conidia

Pycnidium

•• It is a flask shaped fruiting

body whose cavity is lined by a sterile pseudo-parenchymatous tissue comprising its wall, called pycnidial wall. •• Fertile layer consists of very short conidiophores which bear pycniospores or pycnidiospores at their tips, lies in the cavity. The whole structure, i.e., cavity, wall and fertile layer constitute pycnidium. Ostiole

Acervulus

•• It is a saucer shaped

structure consisting of stromatic mass of hyphae and fertile layer of conidiophores. •• Conidiophores arise from a mat of closely crowded hyphae forming a small disc called stroma. •• The conidia are abstricted from the tips of conidiophores.

Conidia

Conidiophores

Conidia

Host epidermis

Hyphal mat

Sporodochium

Pycnidium

Acervulus

The classification of Deuteromycetes is artificial, hence various taxa are known as form - order, form-family, form-genus, etc. On the basis of structure of the asexual fruiting body and type of conidia, the group has been divided into following four orders.

•• This order is represented by about 10,000

form-species. The mycelium is colourless or black in colour. •• Mycelia are septate and branched. •• Conidia are produced directly on hyphal cell or specialised hyphal cells called conidiophores. •• The conidiophores are usually free but sometimes they are assembled into sporodochium or synnemata. E.g., Cercospora, Fusarium, etc.

Anastomosis Step (i)

pathogenic to plants. Many are responsible for the degradation of foods, including decay from rots on vegetables and fruits. Some of the common diseases caused by them are as follows. –• Red rot of sugarcane caused by Colletotrichum falcatum. –• Early blight of potato caused by Alternaria solani. –• Wilt of cotton caused by Fusarium oxysporum. –• Tikka disease of groundnut caused by Cercospora personata. –• Leaf stripe of barley is caused by Helminthosporium gramineum. –• Black point disease in wheat caused by Alternaria tenuis, Fusarium, Helminthosporium, etc.

Strain 2

Order : Sphaeropsidales

•• They produce

conidia in pycnidia. •• The pycnidia may be separate or joined by stromatic tissue. E.g., Phyllosticta, Macrophoma, etc.

Order : Melanoconiales

•• The mycelium is internal and asexual fruiting bodies are acervulus type.

•• The acervuli are sub-epidermal and

develop beneath the host cuticle or epidermis. •• Usually they burst through the host surface as the pigmented conidia mature. •• Conidiophores are aggregated in a palisade like layer on the surface of stroma and conidia are abstricted singly or in chains. E.g., Colletotrichum, Gloeosporium, etc.

Order : Mycelia Sterilia

•• It includes 20

genera and 200 form-species. •• The mycelium is sterile and conidia are not formed. •• They reproduce by sclerotia, rhizomorphs and other vegetative means. E.g., Rhizoctonia sterilia.

Step (ii)

Heterokaryon

Unlike nuclei fuse

Step (vi) Sorting out of new haploid nuclei through conidia

Haploid conidia

Diploid conidia

Haploid conidia Step (v) Haploidisation Recombinant diploid with yellow or white conidia Mitotic crossing over

Step (iii)

Sorting out of diploid nuclei through diploid conidia

Step (iv) Fig.: Pontecorvo’s idea of parasexual cycle

•• Several members, which were previously included in Deuteromycotina due to unknown sexual (perfect) stages, were later transferred to an appropriate group when their perfect stages were recorded in nature or in artificial culture media. The following are few examples : Imperfect stage

Classification

Order : Moniliales

Deuteromycotina Members as Potent Pathogens

Perfect Stages of Imperfect Fungi

Conidiophores Synnema

Strain 1

•• Many species of Deuteromycotina are

•• Conidiophores get assembled in a variety of ways to form different types of asexual fruiting bodies. These are:

•• The whole fructification resembles a long

Emericella nidulans. Parasexuality can be defined as a phenomenon in which the three processes, e.g., plasmogamy, karyogamy and meiosis occurs at an unspecified time and stages in the life of a fungus. Several steps involved in the process of parasexuality: •• Formation of heterokaryotic mycelium - Existence of nuclei of different strains in the protoplasm of the cells of a hypha is termed as heterokaryosis and such hypha is called ‘heterokaryotic’. Heterokaryosis generally occurs in the thallus of a fungus by following ways : by anastomosis (plasmogamy between two genetically different hyphae), by mutation of one or more nuclei in a homokaryotic mycelium by diploidisation, etc. •• Karyogamy - The fusion of haploid nuclei of similar or dissimlar genotypes results in the formation of homozygous or heterozygous diploid nucleus respectively. If the genotype of unlike nuclei present in the heterokaryotic mycelium are A and B, then five different types of nuclei may be formed (haploid A and B,homozygous diploid AA and BB and heterozygous diploid nuclei AB). •• Multiplication of diploid nuclei - These five types of nuclei multiply, but the diploid nuclei are present in much smaller number than the haploid nuclei. •• Occasional mitotic crossing over - Mitotic crossing over takes place during multiplication of diploid nuclei and new gene combinations are formed. These recombintions which are dependent on the existence of heterokaryosis and give the fungus some of the advantages of sexuality within the parasexual cycle. •• Sorting out of diploid nuclei - In those fungi which produce uninucleate conidia, sorting out of the diploid nucleus occurs by their incorporation into conidia. Conidium which contains diploid nucleus germinates to produce diploid mycelium. Diploid strains of several important imperfect fungi have been isolated. •• Haploidisation of diploid nuclei - Occasionally, some hyphae of diploid mycelium form haploid conidia which form haploid mycelia on germination. The formation of haploid conidia by diploid mycelium indicates that haploidisation occurs in some diploid nuclei. •• Sorting of new haploid strains - Some diploid nuclei undergo haploidisation in the mycelium and are sorted out by incorporation of haploid nuclei in the uninucleate conidia. Some of these haploid strains are genotypically different from their parents because of mitotic recombinations.

Perfect stage

Alternaria solani

Pleospora infectoria

Cercospora cerasella

Mycosphaerella cerasella

Cercospora personata

Mycosphaerella berkeleyi

Helminthosporium gramineum

Pyrenophora graminea

Helminthosporium oryzae

Cochliobolus miyabeanus

Colletotrichum falcatum

Glomerella tucumanensis

Economic Importance of Deuteromycotina •• The member of Genus Penicillium are cultivated for the industrial manufacture of cheese (Penicillium roqueforti, Penicillium camemberti), antibiotics (Penicillium notatum, P. chrysogenum) and gluconic acid (Penicillium purpurogenum).

•• Arthrobotrys oligospora and Dactylella cionopaga trap nematodes (microscopic roundworms that often infest the roots of crop plants) by forming hyphal

rings which constrict the nematode when stimulated by contact. Thereby, these Deuteromycotina reduce the disease incidence due to nematode of the crop plant.

CHAPTER-2 : BIOLOGICAL CLASSIFICATION

Multiple Choice Questions 1. How is a capsule advantageous to a bacterium? (a) It protects the bacterium from desiccation. (b) It provides means of locomotion. (c) It allows bacterium to “hide” from host’s immune system. (d) Both (a) and (c) 2. The sporozoa are all internal _____ that typically have an infective cyst stage in their life cycle. An example of sporozoa is the Genus _____, which causes malaria. (a) ciliates, Plasmodium (b) flagellates, Plasmodium (c) parasites, Plasmodium (d) parasites, Trypanosoma 3. Identify the parts labelled as A and B in the given figure of a blue green alga. (a) A-Vegetative cell, B-Heterocyst (b) A-Somatic cell, B-Gamete (c) A-Mucilaginous sheath, B-Heterocyst (d) A-Heterocyst, B-Mucilaginous sheath 4. The chief component of bacterial cell wall is (a) cellulose and chitin (b) cellulose and pectin (c) peptidoglycans (d) cellulose and carbohydrates. 5. Which of the following statements is incorrect? (a) Pathogenic bacteria cause 90% of human diseases. (b) A large number of antibiotics are produced by Actinomycetes (e.g., Streptomyces), which is a Class of Fungi. (c) N2-fixing bacteria pick up free N2 from soil atmosphere and convert it into nitrogenous compounds. (d) Archaebacteria differ from other bacteria in having a different cell wall structure and this feature is responsible for their survival in extreme conditions. 6. Dikaryon formation is characteristic of (a) ascomycetes and basidiomycetes (b) phycomycetes and basidiomycetes (c) ascomycetes and phycomycetes (d) phycomycetes and zygomycetes. 7. Read the given statements. A. Artificial system studies homology in characters viz. morphology, anatomy, molecular systematics, etc. B. Natural system gives information about both natural relationships and phylogeny. C. Natural system uses habit and habitat as criteria for classification. 48

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D.

Artificial system often results in placing of unrelated organisms in a group. Of the above statements, (a) A and B are correct, C and D are incorrect (b) B and D are correct, A and C are incorrect (c) A, B and D are correct, C is incorrect (d) A, B and C are correct, D is incorrect. 8. Select the mismatched pair. Virus (a) Alfalfa Mosaic Virus (b) Parrot fever Virus (c) Beet yellow Virus (d) TMV

-

Size 50 nm 400 nm 1250 × 40 nm 300 × 17.5 nm

9. Which of the following statements regarding the Class Phycomycetes is correct? (a) These are found in aquatic habitats and on decaying wood in moist and damp places or as obligate parasites on plants. (b) Mycelium in these fungi is aseptate and coenocytic. (c) Asexual reproduction occurs by motile zoospores or by non-motile aplanospores. (d) All of these 10.Which of the following is an example of amoeboid protozoan? (a) Trypanosoma (b) Paramecium (c) Plasmodium (d) Entamoeba 11.Identify the given figure X and select the correct option. (a) X is Entamoeba histolytica which capture its prey by putting out pseudopodia. (b) X is Plasmodium vivax that causes malaria which has a staggering effect on humans. (c) X is Giardia intestinalis that causes a disease known as chagas disease. (d) X is Trypanosoma gambiense that belongs X to flagellated protozoans and causes sleeping sickness. 12.Read the following statements and select the correct option. (a) Deuteromycetes reproduce only by asexual spores. (b) The mycelium is unbranched in basidiomycetes. (c) Fusion of two nuclei is known as plasmogamy. (d) Truffles are edible zygomycetes that are often dug out with trained dogs and pigs. 13.Which of the following is not the asexual reproductive structure in fungi?

(a) Sporangiospore (b) Conidia (c) Oospore (d) Zoospore 14.Select the incorrect statement among the followings. (a) Viruses posses either DNA or RNA but never both. (b) Most plant viruses are RNA viruses.

(c) (d)

Viruses cannot be grown in culture medium. Prions possess only nucleoid and no protein.

15.Select the mismatched pair. (a) Polio virus – Enders (b) Crystallised TMV – Stanley (c) Prions – Diener (d) Retrovirus – Temin

Match The Columns 16. Match Column I with Column II. Column I Column II A. Nostoc (i) Pleomorphic B. Alternaria (ii) Drosophila of Plant Kingdom C. Mycoplasma (iii) Star jelly D. Neurospora (iv) Imperfect fungi 17. Match Column I with Column II. (There can be more than one match for items in Column I). Column I Column II A. Purple bacteria (i) Thiopedia B. Pathogenic bacteria (ii) Cleaning agents in tooth paste C. Diatomite (iii) Industrial catalyst D. Antibiotics (iv) Xanthomonas citri (v) Streptomyces (vi) Rhodopseudomonas (vii) Agrobacterium tumefaciens (viii) Bacillus

Passage Based Questions 18.(A) Complete the given passage with appropriate words or phrases. Mycoplasmas are the simplest and (i) of the free living prokaryotes classified under Kingdom (ii). They were discovered in (iii) of cattle suffering from (iv). The size ranges from (v) disease. The genetic material is represented by (vi) which is naked because of absence of (vii) . They are (viii) in their nutrition. They mostly cause (ix) disease in humans and (x) disease in brinjal plant. (B) Read the given passage and correct the errors, wherever present. Sclerotia and rhizomorphs are the means of sexual reproduction in fungi. Rhizomorphs are perennating bodies made up of compact masses of hyphae whereas sclerotia are rope-like twisted subterranean masses of hyphae. Vegetative reproduction in fungi occurs through spores. The sexually produced spores are called mitospores,e.g., basidiospores, conidia, etc. The phenomenon of having two genetically similar and compatible sexual strains in same thalli is known as heterothallism.

Assertion & Reason In each of the following questions, a statement of Assertion (A) is given and a corresponding statement of Reason (R) is given just below it. Of the statements, mark the correct answer as : (a) if both A and R are true and R is the correct explanation of A (b) if both A and R are true but R is not the correct explanation of A (c) if A is true but R is false (d) if both A and R are false. 19. Assertion : Deuteromycetes is commonly called imperfect fungi. Reason : In deuteromycetes, only asexual or vegetative phase is known. 20. Assertion : Archaebacteria are able to survive in harsh habitats. Reason : Presence of peptidoglycan in cell wall helps archaebacteria to survive in extreme conditions. 21. Assertion : Diatoms are called ‘jewels of the plant kingdom’. Reason : Silica wall of diatoms is characterised by fine ridges, lines, pores etc. 22. Assertion : Individuals of Subphylum Sporozoa lack locomotory organelles. Reason : All sporozoa are parasites. 23. Assertion : Viroids are small infectious RNA particles which are devoid of protein coat. Reason : Viroids contain more than 900 nucleotides and do not contain any genes. 24. Assertion : Euglenoids pile up at the bottom of water reservoirs and form big heaps called diatomite. Reason : The reserve food material of euglenoids is in the form of volutin globules. 25. Assertion : Hopanoids are pentacyclic sterols found in plasma membrane of some bacteria. Reason : Hopanoids stabilise the plasma membrane. 26. Assertion : Ascomycetes are commonly known as sacfungi. Reason : Sexual spores of ascomycetes are produced endogenously in sac-like asci. 27. Assertion : In lichens, mycobiont and phycobiont are symbiotically associated with each other. Reason : Mycobiont provides food and phycobiont provides anchorage and absorption of water and minerals. 28. Assertion : Some dinoflagellates such as Gymnodinium cause red tide. Reason : Dinoflagellates are photosynthetic protists and mostly marine. MT BIOLOGY

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Figure Based Questions 29. Refer the given figure and answer the following questions.

2. Read the following statements and select the incorrect option. (a) Sargassum is used as fodder and manure. (b) In chlorophyta the food reserve is starch. (c) Archegonium is partially embedded in bryophytes. (d) Coralline algae produce limestone. 3. Identify A, B, C and D in the given table of different algae and their characteristics. Algae

Stored food

Flagellar number

A

Floridean starch

Absent

Cholorophyceae

B

2–8

C

Mannitol

D

Select the correct option. A B (a) (b) (c) (d)

(a) The given life cycles, (A and B) are found in protists. Identify the type of cycle A and B. (b) Give the examples of groups in which these two cycles (A and B) are found respectively. (c) Differentiate between life cycle A and B. 30. Consider the given figure and answer the following questions. B

A

C

D

Phaeophyceae Phaeophyceae Rhodophyceae Rhodophyceae

Starch Laminarin Starch Starch

C

D

Rhodophyceae 2 Rhodophyceae Absent Phaeophyceae 2 Phaeophyceae Absent

4. Select the correct option to fill up the blanks in the following statements. (i) The sperms of _____ are the largest in the biological world. (ii) _____ is a living fossil which has natural immunity to several plant diseases. (iii) _____ has branched stem with mycorrhizal roots occurring near the soil surface. (i) (ii) (iii) (a) Pinus Cycas Ginkgo (b) Cycas Ginkgo Pinus (c) Ginkgo Cycas Pinus (d) Cycas Pinus Ginkgo 5. Consider the following table for comparison between dicot and monocot. Dicot

(a) Identify A, B, C and D in the given figure. (b) What are the functions of A and B? (c) What will happen if this organism is allowed to grow in dark? CHAPTER-3 : PLANT KINGDOM

Multiple Choice Questions 1. Select the mismatched pair. (a) Agar – Gelidium (b) Carrageenin – Chondrus (c) Funori – Gloiopeltis (d) Algin – Gracilaria 50

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Monocot

(i)

Flowers are trimerous.

Flowers are pentamerous.

(ii)

Pollen grains have three germ pores.

Pollen grains possess a single germinal furrow.

(iii) Vascular bundles are scattered.

Vascular bundles are arranged in a ring.

(iv) Xylem vessels are polygonal.

Xylem vessels are rounded.

How many of the above differences are correct? (a) One (b) Three (c) Two (d) All of these

6. Identify A, B, C and D in the given figure of a moss.

11.Sporophyte became more dominant than gametophyte for the first time in which of the following group of plants? (a) Pteridophytes (b) Mosses (c) Liverworts (d) Gymnosperms 12.In angiosperms, the endosperm is (a) short lived (b) persistent female gametophyte (c) formed before fertilisation (d) formed after fertilisation.

(a) A-Apophysis, B-Capsule, C-Sporophyte,D-Gametophyte (b) A-Capsule, B-Seta, C-Sporophyte, D-Gametophyte (c) A-Apophysis, B-Seta, C-Gametophyte, D-Sporophyte (d) A-Apophysis, B-Capsule, C-Gametophyte,D-Sporophyte 7. Prothallus of pteridophytes is (a) conspicuous, small, multicellular, free-living, photosynthetic thalloid gametophyte (b) inconspicuous, small, multicellular, free-living, photosynthetic thalloid gametophyte (c) inconspicuous, large, unicellular, free-living, photosynthetic thalloid gametophyte (d) inconspicuous, small, multicellular, free-living, nonphotosynthetic thalloid sporophyte. 8. Selaginella and Salvinia are considered to represent a significant step towards evolution of seed habit because (a) female gametophyte is free and gets dispersed like seeds (b) female gametophyte lacks archegonia (c) megaspores possess endosperm and embryo surrounded by seed coat (d) embryo develops in female gametophyte which is retained on parent sporophyte. 9. Diplontic life cycle is present in (a) Riccia, Pinus, Fucus (b) Cycas, Sargassium, Helianthus (c) Selaginella, Marchantia, Chara (d) Bryopsis, Pinus, Marsilea 10.Select the number of correct statements among the following. (i) In liverworts, the leaves generally have a mid-rib. (ii) Antheridium is stalked in pteridophytes. (iii) Archegonia is absent in angiosperms. (iv) In gymnosperms, megasporophyll is commonly woody. (v) In algae, grana are absent in chloroplast. (a) 2 (b) 3 (c) 1 (d) 5

13.Bryophytes do not produce (a) non-ciliated antherozoids and independent sporophyte (b) vascular tissue and independent sporophyte (c) antheridium and archegonium (d) ciliated sperm and independent gametophyte. 14.Pyrenoids are structures made of (a) protein and stored starch (b) starch and stored lipids (c) protein and stored lipids (d) all of these. 15.The juvenile stage of the gametophyte of moss is (a) green, filamentous and branched structure (b) a tetraflagellate body (c) dorsiventrally flattened plate-like body (d) a colourless mass of tubular structure.

Match The Columns 16. Match Column I with Column II. Column I A. Rolling alga (i) B. Tree fern (ii) C. Horse tail (iii) D. Male shield fern (iv) E. Walking fern (v)

Column II Dryopteris Adiantum caudatum Volvox Equisetum Cyathea

17. Match Column I with Column II. (There can be more than one match for items in Column I). Column I Column II A. Agar (i) Gelidium B. Food supplement (ii) Selaginella for space travellers C. Heterosporous (iii) Chlorella pteridophytes D. Triploid endosperm (iv) Salvinia E. Dwarf shoots (v) Eucalyptus (vi) Gracilaria (vii) Spirulina (viii) Acacia (ix) Pinus (x) Ginkgo MT BIOLOGY

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Passage Based Questions 18.(A) Complete the given passage with appropriate words or phrases. Red algae are marine except a few freshwater species like (i) . The red colour is due to abundant formation of (ii) which is able to absorb (iii) wavelengths of light. The photosynthetic organelles are called (iv) . The reserve food is (v) which is very much similar to (vi) Asexual reproduction occurs through a variety of (vii) while sexual reproduction is (viii) . The male sex organ is called (ix) and the female sex organ is called (x) . (B) Read the given passage and correct the errors, wherever present. Ferns are seed producing vascular plants which inhabit dry areas. They constitute the smallest living group of primitive vascular plants. Ferns dominated the earth in permian period. Leaves are large and called ramenta. Mature leaves show circinate ptyxis. Younger parts of their stem, leaves and petiole possess hairs called fronds.

25. Assertion : True stem and leaves are absent in bryophytes. Reason : In bryophytes, sporophyte is parasitic over gametophyte. 26. Assertion : In green algae, sexual reproduction occurs through palmella stage. Reason : In palmella stage, two flagellated, thick walled cells lie close to each other embedded in mucilagenous mass. 27. Assertion : Giant kelps are used as fertiliser. Reason : Giant kelps are important source of minerals. 28. Assertion : In Marchantia, elaters are directly formed from the sporogenous cells. Reason : Elaters are haploid.

Figure Based Questions 29. Refer to the given figures and answer the following questions.

Assertion & Reason

TODAY | MAY ‘18

Sex organs (2n)

n sio

Gametes (n) B

Fu

s

MT BIOLOGY

30. Study to the given figure answer the following questions. iosi

52

(a) Name the plants and their division respectively represented by the given figures A and B. (b) Which given plant belongs to the plant group known as amphibians of the Plant Kingdom and why the plant group is named so? (c) Write economic importance of the division represented by plant B.

Me

In each of the following questions, a statement of Assertion (A) is given and a corresponding statement of Reason (R) is given just below it. Of the statements, mark the correct answer as : (a) if both A and R are true and R is the correct explanation of A (b) if both A and R are true but R is not the correct explanation of A (c) if A is true but R is false (d) if both A and R are false. 19. Assertion : In gymnosperms, the male and female gametophytes do not have independent existence. Reason : They remain within the sporangia retained on the sporophyte. 20. Assertion : Gymnosperms do not produce fruit. Reason : Ovules of gymnosperms are enclosed within the ovaries. 21. Assertion : Algae show only anisogamous type of reproduction. Reason : In algae, gametes can never be non-flagellated. 22. Assertion : In bryophytes, there is progressive sterilisation of sporogenous tissue as we move from lower to higher forms. Reason : In mosses the sporogenous tissue is present inside the capsule that includes columella. 23. Assertion : Pteridophytes are known as botanical snakes. Reason : The stem of pteridophyte is a rhizome which grows obliquely under the surface of soil with only apical portion coming out of soil surface. 24. Assertion : Flower is the characteristic feature of angiosperms. Reason : Flower ensures fertilisation of the ovule and development of fruit containing seeds.

Zygote (2n)

A Sporophyte (2n)

(a) Identify the type of life cycle along with A and B shown in the given figure. (b) Name two brown algae showing this type of life cycle. (c) State the significance of this life cycle in fucales. CHAPTER-4 : ANIMAL KINGDOM

Multiple Choice Questions 1. Sycon belongs to a group of animals which are best described as (a) unicellular or acellular (b) multicellular without any tissue organisation (c) multicellular with a gastrovascular system (d) multicellular having tissue organisation, but no body cavity.

2. Which one of the following phyla is correctly matched with its two general characteristics? (a) Echinodermata – pentamerous radial symmetry and mostly internal fertilisation (b) Mollusca – normally oviparous and development through a trochophore or veliger larva (c) Arthropoda – body divided into head, thorax and abdomen and respiration by mouth (d) Chordata – notochord persists throughout the life and separate anal and urinary openings to the outside 3. In the life history of liver fluke (1) Cercariae (2) Metacercariae (3) Sporocyst (4) Rediae (5) Miracidium are present. What is their proper sequence? (a) 21354 (b) 53412 (c) 54213 (d) 54312 4. Identify the figures A, B, C and D and select the correct option.

(a) (b) (c) (d)

A-Liver fluke; B-Male roundworm; C-Hirudinaria; D-Nereis A-Liver fluke; B-Female roundworm; C-Hirudinaria; D-Nereis A-Liver fluke; B-Male roundworm; C-Nereis; D-Hirudinaria A-Liver fluke; B-Female roundworm; C-Nereis; D-Hirudinaria

5. Which one of the following categories of animals, is correctly described with no single exception in it? (a) All reptiles possess scales, have a three chambered heart and are cold blooded (poikilothermal). (b) All bony fishes have four pairs of gills and an operculum on each side. (c) All sponges are marine and have collared cells. (d) All mammals are viviparous and possess diaphragm for breathing.

(c) (d)

Ventral heart Post-anal tail

– Palamneus – Octopus

8. Organism with shortest gestation period is (a) duck-billed platypus (b) opossum (c) elephant (d) rabbit. 9. Which of the following group is formed of only the hermaphrodite organisms? (a) Earthworm, tapeworm, housefly, frog (b) Earthworm, tapeworm, sea horse, housefly (c) Earthworm, leech, sponge, roundworm (d) Earthworm, tapeworm, leech, sponge 10.Crocodile and penguin are similar to whale and dog fish in which one of the following features? (a) Possess a solid single stranded central nervous system (b) Lay eggs and guard them till they hatch (c) Possess exoskeleton (d) Have gill slits at some stage 11.Select the incorrect statement among the following. (a) Spherical symmetry is present in Volvox. (b) In bilateral symmetry, the body can be divided into two equal halves by any plane passing through the centre from top to bottom. (c) Radial symmetry is present in sea anemones. (d) In blind sac body plan, the body has a single cavity with one opening to the outside. 12.Which of the following character is not present in cartilaginous fishes? (a) Ten pairs of cranial nerves (b) Sac-like outgrowth called air bladder arising from oesophagus (c) Well developed lateral line system (d) Minute placoid scales on skin 13.Which of the following is not a mammalian feature of crocodilians? (a) 12 pairs of cranial nerves (b) Four chambered heart (c) Foramen of panizza (d) Bony secondary palate

6. In cephalochordates, notochord is (a) confined only to head (b) confined only to tail (c) extended from head to tail (d) absent in adult.

14.Class Crustacea have which of the following features? (a) Cephalothorax, biramous appendages and gills (b) Cephalothorax, book lungs and chitinous exoskeleton (c) Head and thorax, book lungs and chitinous exoskeleton (d) Head and thorax, biramous appendages and book lungs

7. Which one of the following is correct matching pair of a body feature and the animal possessing it? (a) Ventral central – Hirudinaria nervous system (b) Pharyngeal gill slits – Chameleon absent in embryo

15.Which one of the following pairs of animals is correctly matched with the kind of their body symmetry? (a) Hydra and shark - Bilateral symmetry (b) Tapeworm and Octopus - Radial symmetry (c) Amoeba and sea urchin - Asymmetry (d) Jellyfish and starfish - Radial symmetry MT BIOLOGY

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Match The Columns 16. Match Column I with Column II. Column I Column II A. Choanocytes (i) Platyhelminthes B. Cnidoblasts (ii) Ctenophora C. Flame cells (iii) Porifera D. Nephridia (iv) Coelenterata E. Comb plates (v) Annelida 17. Match Column I with Column II. (There can be more than one match for items in column I). Column I Column II A. Mouth circular (i) Petromyzon and jawless B. Placoid scales (ii) Scoliodon C. Uropygial glands (iii) Struthio D. Marsupial pouch (iv) Didelphis E. Presence of pinna (v) Chimaera (vi) Myxine (vii) Columba (viii) Rattus (ix) Macropus (x) Cavia

20.

21.

22.

23.

24.

25.

Passage Based Questions 18.(A) Complete the given passage with appropriate words or phrases. The animals which posses true coelom are called (i) . The true coelom is a body cavity which arises as a cavity in (ii) . The (ii) provides a cellular lining called (iii) to the cavity. The coelom is filled with (iv) secreted by the (iii). True coelom is found in (v) , (vi) and (vii) . True coelom is of two types, (viii) and (ix) . The animals which do not have coelom are called (x) . (B) Amphibians are warm blooded animals. Their skull is monocondylic and the heart is two chambered. Kidneys are metanephric and urinary bladder is absent in frog. Their larval forms are ureotelic whereas adults are ammonotelic. Twelve pairs of cranial nerves are present in them Fertilisation is internal and they are mostly viviparous.

Assertion & Reason In each of the following questions, a statement of Assertion (A) is given and a corresponding statement of Reason (R) is given just below it. Of the statements, mark the correct answer as : (a) if both A and R are true and R is the correct explanation of A (b) if both A and R are true but R is not the correct explanation of A (c) if A is true but R is false (d) if both A and R are false. 19. Assertion : Gills of chordates differ from the gills of nonchordates. 54

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26.

27.

28.

Reason : Gills of chordates occur in pharyngeal gill slits which are absent in non-chordates. Assertion : Fishes have venous heart. Reason : Only veins are present in the circulatory system of fishes. Assertion : Metamerism is the characteristic feature of annelida. Reason : Annelids are diploblastic, segmented and coelomate animals. Assertion : Platyhelminthes and molluscs are diploblastic animals. Reason : In diploblastic animals, an undifferentiated layer called mesoderm is present between the ectoderm and endoderm. Assertion : Presence of water vascular system is the characteristic feature of Phylum Echinodermata. Reason : A perforated plate called madreporite is present in water vascular system which helps in locomotion. Assertion : Direct development is present in Hydra. Reason : In direct development, the young ones do not resemble the adults. Assertion : Aschelminthes are called as pseudocoelomates. Reason : In aschelminthes, mesoderm is present as scattered pouches in between ectoderm and endoderm. Assertion : In ctenophores, locomotion takes place through comb plates. Reason : Comb plates are comb-like ciliary plates present on the body of ctenophores. Assertion : Phylum Arthropoda is the largest phylum of Kingdom Animalia. Reason : Arthropods possess thick chitinous exoskeleton and jointed appendages. Assertion : Taenia solium does not have an alimentary canal. Reason : Adults of T. solium live as parasites in the small intestine of human beings.

Figure Based Questions 29. Examine the given figure and answer the questions regarding it. (a) What features do you find peculiar about urinogenital system of the given bird? (b) Give valid explanation for such unique characteristics of birds. (c) Where does fertilisation takes place in birds? (d) What would happen if in a bird shell gland is dysfunctional?

30. Refer the given figure and answer the following questions.

(a) Identify the generic names of organisms A, B and C. (b) What is the mode of nutrition in organism A? Which structures supplement its mode of nutrition? (c) Describe various cells found in the epidermal layer of body wall of organism B. (d) To which phylum organism C belongs? How does it defend itself from its enemies?

SOLUTIONS CHAPTER-1 : THE LIVING WORLD 1. (c) 2. (d) 3. (b) 4. (b) 6. (c) 7. (a) 8. (b) 9. (b) 11. (d) 12. (b) 13. (c) 14. (a)

5. (a) 10. (d) 15. (c)

16. A-(iii); B-(ii); C-(iv); D-(i) 17. A-(ii),(iv), (vi); B-(i),(iii); C-(viii); D-(v),(vii) 18.(A) (i) (ii) (iii) (iv) (v)

nomenclature identification systematics generic specific

(vi) (vii) (viii) (ix) (x)

species genus Latin Greek Roman

(B) Herbarium is a place where fresh dried and pressed plant specimens, mounted on sheets are kept randomly systematically. Herbarium is a repository for present future use. It provides information about the local flora only as well as flora of distant areas and also about the ecology of different places. Herbaria are used for correct and authentic identification of known unknown plants. It depicts the anatomical morphological variations found in species. 19. (d) 20. (a) 21. (c) 22. (d) 23. (c) 24. (b) 25. (c) 26. (d) 27. (c) 28. (b) 29. (a) The given figure is of taxonomical hierarchy. Here, A is Family, B is Order, C is Phylum/Division and D is Kingdom. (b) Order is one of the obligate category in taxonomic hierarchy which includes one or more related families one or more related orders are clustered together in a class. (c) The family (A), order (B) and phylum/division (C) of Triticum is poaceae, poales and angiospermae respectively. While for Felis it is felidae, carnivora and chordata respectively. 30. (a) A–A store house of collected plant specimens that are dried, pressed and preserved on sheets. B–Collection and maintenance of living plants for reference. C–Enclosed areas where animals are kept in open enclosures instead of cages. D–A place used for storage, preservation and exhibition of objects of natural history, art and antiquities. E–A dichotomic table of alternate characteristics known as couplet and each statement of key is called lead.

(b) (i) (ii) (iii) (iv) (v) (vi)

30×45 Moscow ex-situ Andaman and Nicobar Islands indented bracketed

CHAPTER-2 : BIOLOGICAL CLASSIFICATION

1. 6. 11. 16.

(d) 2. (c) 3. (d) (a) 7. (b) 8. (a) (d) 12. (a) 13. (c) A-(iii); B-(iv); C-(i); D-(ii)

4. (c) 9. (d) 14. (d)

5. (b) 10. (d) 15. (c)

17. A-(i, vi); B-(iv, vii); C-(ii, iii); D-(v, viii) 18.(A) (i) smallest (vi) single DNA duplex (ii) Monera (vii) histones (iii) pleural fluid (viii) heterotrophic (iv) pleuropneumonia (ix) mycoplasmal urethritis (v) 0.1 – 0.15 mm (x) little leaf disease (B) Sclerotia and rhizomorphs are the means of sexual vegetative reproduction in fungi. Rhizomorphs Sclerotia are perennating bodies made up of compact masses of hyphae whereas sclerotia rhizomorphs are rope like twisted subterranean masses of hyphae. Vegetative Asexual reproduction in fungi occurs through spores. The sexually produced spores are called mitospores, meiospores, e.g., basidiospores, conidia ascospores , etc. The phenomenon of having two genetically similar different and compatible sexual strains in same separate thalli is known as heterothallism. 19. (a) 20. (c) 21. (a) 22. (a) 23. (c) 24. (d) 25. (b) 26. (a) 27. (c) 28. (b) 29. (a) : In the given life cycles, A represents life cycle with zygotic meiosis while B represents life cycle with gametic meiosis. (b) Life cycle showing zygotic meiosis is found in dinoflagellates and cellular slime moulds. Life cycle showing gametic meiosis is found in majority of protozoan protists, diatoms and acellular slime moulds. (c) Differences between life cycle with zygotic meiosis (A) and life cycle with gametic meiosis (B) are as follows: MT BIOLOGY

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Life cycle with zygotic meiosis

Life cycle with gametic meiosis

(i)

Zygote is the only diploid All structures except structure in the life cycle. gametes are diploid.

(ii)

The dominant individual in the life cycle is haploid hence the life cycle is haplontic.

The dominant individual in the life cycle is diploid hence the life cycle is diplontic.

(iii) Meiosis takes place at the Meiosis occurs only at the time of zygote germination. time of gamete formation.

(Division Bryophyta) and Selaginella (Division Pteridophyta) respectively. (b) Plant A, Marchantia belongs to plant group bryophytes. Bryophytes are called amphibians of Plant Kingdom as they require an external layer of water on the soil surface for their existence. The external water is required for : (i) dehiscence of antheridia and archegonia (ii) swimming of male gametes to archegonia, (iii) protection from transpiration and hence desiccation as the plant body is not covered by cuticle (iv) supply of water to all parts through capillarity as vascular tissues are absent in them.

(b) The cytostome (A) is an eccentric mouth part at the apical end of the organism. It leads to a tubular canal, called cytopharynx which expands at the base to form a large rounded reservoir. At the end of the reservoir, the cytoplasm contains an orange red stigma or eye spot. It is photosensitive. It contains red pigment astaxanthin. Paraflagellar body and eye spot together help in directing the organism towards the optimum light.

(c) The economic importance of pteridophytes (B) is as follows: (i) Pteridophytes constitute a good source of food to animals. For example, sporocarps of Marsilea, yield starch that is cooked and eaten by certain tribal people. (ii) Pteridophytes bind the soil even along hill slopes and thus protect the soil from erosion. (iii) Equisetum stems have been used in scouring i.e., cleaning of utensils and polishing of metals. (iv) Azolla has a symbiotic association with nitrogen fixing cyanobacterium Anabaena azollae. (v) An antihelminthic drug is obtained from rhizomes of Dryopteris. (vi) Ferns are grown as ornamental plants for their delicate and graceful leaves.

(c) The nutrition in Euglena, is holophytic (photoautotrophic) or (saprobic). When it is allowed to grow in dark, the photosynthetic form can feed on organic remains. Such mode of nutrition is known as mixotrophic.

30. (a) The life cycle in the given figure is of diplontic type. A is the sporophytic generation while B is the gametophytic generation. (Sporophytic part is elaborate and major whereas haploid part is only confined to gametes).

CHAPTER-3: PLANT KINGDOM 1. (d) 2. (c) 3. (c) 6. (b) 7. (b) 8. (d) 11. (a) 12. (d) 13. (b)

(b) Fucus and Sargassum show diplontic life cycle.

30. (a) The given figure is of Euglena. Here, A is Cytostome, B is Stigma, C is Paramylum bodies and D is Chloroplast.

4. (b) 9. (b) 14. (a)

5. (c) 10. (a) 15. (a)

16. A-(iii); B-(v); C-(iv); D-(i); E-(ii) 17. A-(i, vi), B-(iii, vii), C-(ii, iv), D-(v, viii), E-(ix, x) 18.(A)(i) Batrachospermum (ii) phycoerythrin (iii) blue-green (iv) chromatophores (v) floridean starch (vi) glycogen (vii) spores (viii) oogamous (ix) antheridium (x) carpogonium (B) Ferns are seed producing seedless vascular plants which inhabit dry humid areas. They constitute the smallest largest living group of primitive vascular plants. Ferns dominated the earth in permian carboniferous period. Leaves are large and called ramenta fronds. Mature Young leaves show circinate ptyxis. Younger parts of their stem, leaves and petiole possess hairs called fronds ramenta. 19. (a) 20. (c) 21. (d) 22. (b) 23. (a) 24. (b) 25. (b) 26. (d) 27. (a) 28. (c) 29. (a) The given figures A and B represent Marchantia 56

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(c) The diplontic life history in fucales such as Fucus and Sargassum, is clearly derived from a diplo-haplontic life cycle where the gametophytic or haploid somatic phase gets eliminated through progressive evolution. CHAPTER - 4 : ANIMAL KINGDOM

1. (b) 2. (b) 3. (b) 4. (d) 5. (b) 6. (c) 7. (a) 8. (b) 9. (d) 10. (d) 11. (b) 12. (b) 13. (c) 14. (a) 15. (d) 16. A-(iii); B-(iv); C-(i); D-(v); E-(ii) 17. A-(i, vi); B-(ii, v); C-(iii,vii); D-(iv,ix); E-(viii, x) 18.(A) (i) eucoelomate or coelomate (vi) echinoderms (ii) embryonic mesoderm (vii) chordates (iii) peritoneum (viii) schizocoelom (iv) coelomic fluid (ix) enterocoelom (v) annelids (x) acoelomates (B) Amphibians are warm cold blooded animals. Their skull is monocondylic dicondylic and the heart is two three chambered. Kidneys are metanephric mesonephric and urinary bladder is absent present in frog. Their larval forms are ureotelic ammonotelic whereas adults are ammonotelic ureotelic. Twelve Ten pairs of cranial nerves are present in

them. Fertilisation is internal external and they are mostly viviparous oviparous. 19. (a)

20. (c)

21. (c)

22. (d)

23. (c)

24. (c)

25. (a)

26. (b)

27. (a)

28. (a)

29. (a) Presence of a single functional ovary on the left side in the female birds and absence of urinary bladder. (b) Only the left ovary and oviduct are developed in the mature females. Birds do not have the urinary bladder, which is present to store the urine temporarily in other animals. Moreover, the water of the excretory fluid is reabsorbed in the urinary tubules of kidneys and in the cloaca. The result is the formation of a semisolid excreta, chiefly containing the insoluble uric acid and urates which are excreted at once. These features help in reducing the unnecessary weight of the body which are advantageous for their flight. (c) Fertilisation takes place in the oviduct, near the ovary. (d) The shell gland which is actually the wall of oviduct, secretes albumen, shell membranes and calcareous shell over the egg. When the egg is laid, the shell on coming in contact with air becomes hard and non-porous which is essential for the proper development of the embryo. So, if the shell gland is non-functional, the egg will get broken

easily and the young one would not develop. 30. (a) In the given figure, A isTaenia, B is Aurelia and C is Octopus. (b) Organism A (Taenia) shows parasitic mode of nutrition. Its body is divisible into scolex, neck and strobila. Scolex contains cone like rostellum at its top. Rostellum bears chitinous hooks in two circlets. On the middle part of scolex, 4 cup shaped suckers are present. Hooks and suckers are adhesive organs which help these parasites to attach firmly to the body of host from which they derive nutrition. Hence, these structures supplement their parasitic mode of nutrition. (c) The epidermis of organism B consists of the following cells. (i) Epitheliomuscular cells that provide protection and act as muscles. (ii) Cnidoblasts ( = stinging cells) has nematocyst (‘stinging organ’) which are used for defence and offence. (iii) Interstitial cells are reserve cells also called totipotent cells which can be converted into any type of cells. (iv) Nerve cells form a primitive nervous system. (v) Sensory cells are sensory in function. (d) Organism C (Octopus) belongs to Phylum Mollusca. It ejects inky fluid in water and forms a screen for defence from its enemies. 

Unscramble the words given in column I and match them with their explanations in column II. Column I

Column II

1. NHOMECAUTRI

(a)

2. ECILHN

(b)

3. SOONKLIGYEI

(c)

4. 5. 6. 7.

SLCHOISIE SIVAMTA NAECCLUR ESRMSAEPE

(d) (e) (f) (g)

8. OOUHATXRP 9. IHOATDEIDML

(h) (i)

10. HEOPYRILTSIPEN

(j)

Integral carrier proteins that facilitate the transport of a given molecule through a cell membrane. Occasional reappearance of a remote ancestral trait in some individuals of a species. Mutant organism that cannot grow in the minimal medium and require additional nutrients. A synthetic teratogenic drug that is used in treatment of multiple myeloma. Pioneer species in xerarch succession. Inflammation of kidney, typically due to a bacterial infection. Genetic material which shows maximum staining during metaphase and less staining in interphase nucleus. The scientific study of body movements. A condition characterised by dry scaling, fissuring of the lips and corners of the mouth due to riboflavin deficiency. An outgrowth or appendage at or near the hilum of castor seed.

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Class XII

This article covers high yield facts of the given topic.

Sexual Reproduction in Flowering Plants • • • •

The process of development of new organisms through the formation and fusion of gametes is called sexual reproduction. In angiosperms, the organs specialised to perform sexual reproduction are flowers. Flowers are modified condensed reproductive shoots. A typical flower has a broad base called thalamus over which four whorls of floral leaves, i.e., sepals (calyx), petals (corolla), stamens (androecium) and carpels (gynoecium) are borne. • Stamens and carpels represent male and female reproductive structures of flowers respectively. They are called essential floral organs. • Sepals and petals are called non-essential floral organs because they have only supportive role.

STAMEN-THE MALE REPRODUCTIVE ORGAN

• Stamen consists of two parts-filament and anther. • Filament is long and slender stalk attached proximally to thalamus, petal or tepal. It bears an anther distally. • Anther is bilobed, knob-like fertile part of the stamen. The two anther lobes separated by a deep groove in the anterior side and attached to each other by a sterile parenchymatous tissue called connective on the posterior side. • Each anther lobe has two chambers which posses pollen sacs or microsporangia. • A bilobed anther is tetrasporangiate. • A microsporangium or pollen sac is a cylindrical sac which appears circular in transverse section. • It consists of two parts : outer wall and central homogeneous sporogenous tissue. • The outer wall has four types of layers epidermis, endothecium, 1-3 middle layers and tapetum. • The outer three layers protect the young anther and take part in the mechanism of dehiscence in the ripe anther. • The endothecium is also called fibrous layer due to the presence of fibrous thickenings. • The tapetal cells enlarge and become filled with dense protoplasmic content as well as nutrients. • Two types of tapetum are present amoeboid and secretory.

Functions of Tapetum

• It provides nourishment to the developing microspore mother cells and pollen grains either by forming a plasmodium (amoeboid type) or through diffusion (secretory type). • It produces lipid rich Ubisch granules containing sporopollenin for exine formation. • It secretes enzymes like callase responsible for degradation of callose wall around pollen tetrad. 58

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Microsporogenesis • The process of formation of pollen grains through meiosis in pollen mother cells is termed as microsporogenesis. • Sporogenous tissue within the anther grow and transform into pollen Analysis of various PMTs from 2013-2017 mother cell (PMC) which in turn produce tetrads of haploid microspores AIPMT/NEET 10 or pollen grains. AIIMS 9 JIPMER • The pollen grains of a tetrad grow and separate from one another. 8 • Usually the arrangement of microspores in a tetrad is tetrahedral or 7 isobilateral. However, decussate, linear and T-shaped tetrads are also found. 6 5 Structure of pollen grain 4 • Mature anther has two cavities, therefore, it is called dithecous. 3 • Pollen grain is commonly globular in outline though several other shapes 2 are found. 1 • Covering of pollen grain is called sporoderm consisting of two layers, outer 2013 2014 2015 2016 2017 exine and inner intine. • Intine is pecto-cellulosic in nature while exine is made of a highly resistant fatty substance called sporopollenin. Because of sporopollenin, pollen grains are well preserved as microfossils as sporopollenin is not affected by any enzyme, high temperature, strong acid or strong alkali. • Pollen grain is uninucleate in the beginning but at the time of liberation from anther it is 2-3 celled.

Structure and development of male gametophyte • Development of male gametophyte is precocious, i.e., it begins inside the microsporangium or pollen sac. • Young pollen grain has a centrally placed nucleus embedded in dense cytoplasm covered by plasma membrane. • It grows in size with the inflow of nutrients and eventually protoplast divides mitotically to form two unequal cells-small generative cell and large tube or vegetative cell. • The generative cell is spindle shaped to spherical in outline with thin dense cytoplasm surrounding a prominent nucleus. • The tube cell has a vacuolate cytoplasm rich in the food reserves and cell organelles. Its nucleus is large and irregular. • In some species the generative cell divides into two nonmotile male gametes prior to the dehiscence of anther and release of the pollen grains. • Therefore, at the time of pollination, the pollen grain is either 2-celled (tube cell + generative cell) or 3-celled (tube cell + two male gametes). • On the stigma the compatible pollen grain absorbs water and nutrients from the stigmatic secretion through its germ pores. • The tube or vegetative cell enlarges and comes out of the pollen grain through one of the germ pores to form a pollen tube covered over by intine. • The tube nucleus along with generative cell descend to the tip of the pollen tube. • The generative cell soon divides into two nonmotile male gametes if it is not already divided. • Each male gamete has a large nucleus surrounded by a thin sheath of cytoplasm and is considered to be one cell. • The tube nucleus may degenerate completely. • A pollen grain with pollen tube carrying male gametes represent mature male gametophyte and is 3 celled (1 tube cell and 2 male gametes) and 3 nucleated structure.

PISTIL - THE FEMALE REPRODUCTIVE ORGAN • • • •

Gynoecium represents the female part of a flower. The free unit of gynoecium is called pistil. A pistil has three parts-stigma, style and ovary. Stigma is the terminal receptive part of the pistil which functions as landing platform for the pollen grains. The style is the elongated slender part beneath the stigma that connects stigma with the ovary. The basal bulged part of the pistil is the ovary. • Inside the ovary lies the ovarian cavity (locule). The placenta is located inside the locule. • From the placenta megasporangia arises, commonly called ovules. • The number of ovules in an ovary may be one (wheat, paddy, mango) to many (papaya, watermelon, orchids). MT BIOLOGY

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Structure of Ovule

• A typical angiosperm ovule is a small structure attached to the placenta by means of stalk called funicle. The body of the ovule fuses with funicle and the point of attachment is called hilum. • The body of the ovule consists of a mass of parenchymatous cells named nucellus. • Nucellus is surrounded by one (unitegmic ovule, e.g., higher dicots) or two (bitegmic ovule, e.g., monocots and primitive dicots) or multicellular integuments. • The integuments leave a narrow passage known as micropyle at one end of the ovule. • The place of origin of the integuments usually lies at the opposite end of micropyle, termed as chalaza. • Embryo sac or female gametophyte is present in the micropylar half of nucellus. • Depending upon the configuration and orientation of the body of ovule in relation to funiculus there are six types of ovules in angiosperms - orthotropous (erect), anatropous (inverted), hemitropous (half-inverted), campylotropous (body curved), amphiotropous (both body and embryo sac curved), circinotropous (funiculus coiled around the ovule).

Megasporogenesis

• • • • • • •

The process of formation of haploid megaspores from the diploid megaspore mother cell is called megasporogenesis. Generally, a single megaspore mother cell (MMC) differentiates in the micropylar region of the nucellus. The megaspore mother cell undergoes meiotic division which results in the production of four haploid megaspores. In majority of angiosperms, only one of the megaspores is functional while the other three degenerate. The functional megaspore develops into the female gametophyte (embryo sac). The formation of embryo sac from a single megaspore is called monosporic development. The female gametophyte or embryo sac contains 8 nuclei but 7 cells-3 Chalaza micropylar, 3 chalazal and one central. Raphe Nucellus The three micropylar cells are known as egg apparatus. The middle Integuments cell of the egg apparatus is called egg which is larger with a central vacuole and a nucleus towards the chalazal end while the remaining Antipodal cells two cells are called synergids. Central cell Two polar Each of the synergids bears a filiform apparatus in the micropylar region Embryo sac nuclei which is a mass of finger like projections of the wall into the cytoplasm. Egg (oosphere) Synergids The three chalazal cells of the embryo sac are called antipodal cells. Vascular strand The central cell is the largest cell of the embryo sac. Hilum The central cell contains two polar nuclei which often fuse to form a Funiculus single diploid secondary or fusion or definitive nuclei. Micropyle

•

• • • •

Fig.: Structure of a typical ovule (anatropous ovule) prior to fertilisation.

1. 2.

What are the functions of tapetum? In which type of ovule funiculus is coiled around the ovule? Give an example.

POLLINATION

• The transfer of pollen grains from the anther to the stigma is called pollination.

Types of Pollination Self pollination Autogamy • Transfer of the pollen grains from the anther to the stigma of the same flower.

Geitonogamy • Transfer of pollen grains from the anther to the stigma of another flower of the same plant.

Cross pollination or Xenogamy

• Transfer of pollen grains from anther to the stigma of a genetically different plant.

• Some plants such as Oxalis, Viola and Commelina produce two types of flower - chasmogamous flowers with exposed anthers and stigma and cleistogamous flowers which do not open of all. • Cleistogamous flowers are invariably autogamous as there is no chance of cross-pollen landing on the stigma. 60

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Agents of Pollination

• Xenogamy or cross pollination is performed with the help of an external agency which may be abiotic (wind, water) or biotic (animals). • Cross pollination is named after the agency that assists it, e.g., anemophily (wind pollination), hydrophily (water pollination), entomophily (insect pollination), ornithophily (bird pollination), chiropterophily (bat pollination) and malacophily (snail pollination). Cross pollinating flowers with different agencies have different characteristic features.

Characteristics of cross pollinating flowers Wind pollinated flowers Flowers are small and inconspicuous. Pollen grains are dry, light and non sticky. Well exposed stamens Large often feathery stigma to trap air-borne pollen grains. • Single ovule in each ovary and numerous flowers packed into an inflorescence. • Common in grasses

• • • •

Water pollinated flowers

• Flowers are small and inconspicuous. • Pollen grains are long, ribbon like and protected from wetting by a mucilaginous covering. • Stigma is long, sticky but unwettable • Observed in Vallisneria, Zostera, Ceratophyllum.

Insect pollinated flowers

• Flowers are large, colourful, fragrant and rich in nectar

• The flowers produce an odour which may be pleasant or foul.

• When the flowers are small, a number of flowers are clustered together into an inflorescence to make them conspicuous. • Observed in jasmine, Rosa, Magnolia, etc.

Outbreeding Devices or Contrivances to Ensure Cross Pollination

• Continuous self-pollination results in inbreeding depression. Therefore, angiosperms have developed many devices to discourage self-pollination and encourage cross-pollination. • Dichogamy - Pollen release and stigma receptivity are not synchronised in some species. Either the pollen is released before the stigma becomes receptive or stigma becomes receptive much before the release of pollen. In protandry, anthers mature earlier than stigma of the same flower, e.g., Sunflower; in protogyny stigma mature earlier, e.g., Mirabilis. • Heterostyly - In some species the anther and stigma are placed at different positions so that the pollen cannot come in contact with the stigma of the same flower. E.g., Primula, Lythrum. • Self incompatibility - This is a genetic mechanism that prevents self-pollen (from the same flower or other flowers of the same plant) from fertilising the ovules by inhibiting pollen germination or pollen tube growth in the pistil. E.g., Tobacco, potato. • Dicliny - Flowers are unisexual so that self-pollination is not possible. The plants may be monoecious (bearing both male and female flowers, e.g., Maize) or dioecious (bearing male and female flowers on different plants, e.g., Mulberry, papaya). • Prepotency - Pollen grains of another flower germinate more rapidly than the pollen grains of the same flower over the stigma, e.g., apple, grape. • Herkogamy - The different mechanical devices to prevent self-pollination and promote cross pollination, e.g., Stigma lies inside a flap in pansy, anthers occurs inside corolla pocket in Kalmia.

Pollen - Pistil Interaction • • • • •

It is a dynamic process that occurs from the time of pollen deposition over the stigma to the time of pollen tube entry into ovule. It is a safety measure to ensure that illegitimate crossing do not occur. Pollen grains of a number of plants may settle over a stigma. Pollen - pistil interaction ensures that only the right pollen belonging to same species would germinate while others fail to do so. Knowledge of pollen-pistil interaction is helpful to plant breeders in manipulating pollen growth even in incompatible cases.

Artificial Hybridisation

• Artificial hybridisation has been used by plant breeders for crop improvement programme. • In artificial hybridisation, it is important to make sure that only the desired pollen grains are used for pollination and the stigma is protected from contamination. • This is achieved by emasculation and bagging technique. • Emasculation is removal of stamens from the floral buds of female parent (if the female parent bears bisexual flowers) so that chances of self-pollination are eliminated. • Bagging is covering of emasculated flowers with a bag made of butter paper to prevent contamination of its stigma with unwanted pollens. • When the stigma of bagged flower attains receptivity, mature pollen grains collected from the anthers of the male parent flower are dusted on the stigma and the flowers are rebagged and the fruits are allowed to develop. MT BIOLOGY

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FERTILISATION

• Fertilisation is the fusion of male and female gametes. In seed plants, i.e., gymnosperms and angiosperms the male gametes are brought to the egg containing female gametophyte by a pollen tube (Strasburger, 1884). This phenomenon is called siphonogamy. • The pollen tube carrying the male gametes enters the ovule either through its micropyle (porogamy, e.g., lily), chalaza (chalazogamy e.g., Casuarina) or the sides after piercing through the integuments or funicle (mesogamy, e.g., Cucurbita). • Usually the pollen tube enters the embryo sac by passing into one of the two synergids. • The pollen tube releases the two male gametes into the cytoplasm of the synergid. • One of the male gametes moves towards the egg cell and fuses with its nucleus resulting in the formation of diploid zygote. • The other male gamete moves towards the two polar nuclei located in the central cell and fuses with them to produce a triploid primary endosperm nucleus. • Since two types of fusion takes place (syngamy and triple fusion) in an embryo sac, the phenomenon is termed as double fertilisation, an event unique to angiosperms. • The primary endosperm nucleus develops into the endosperm while the zygote develops into an embryo.

POST-FERTILISATION : STRUCTURES AND EVENTS

• Following double fertilisation, events of endosperm and embryo development, maturation of ovule (s) into seed (s) and ovary into fruit, are collectively termed as post-fertilisation events. • The development of endosperm precedes embryo development since the cells of endosperm are filled with reserve food materials that are used for the nutrition of developing embryo. • In the most common type of endosperm development, the primary endosperm nucleus undergoes successive nuclear divisions to produce a large number of free nuclei without cell wall. This stage of endosperm development is called free nuclear endosperm. • Cell wall formation occurs subsequently and the endosperm becomes cellular. • The coconut water from tender coconut is free-nuclear endosperm and the surrounding white kernel is the cellular endosperm. (a) • Embryo develops at the micropylar end of the embryo sac where the zygote is situated. • The early stages of embryo development are similar in both monocotyledons and dicotyledons. • A typical dicotyledonous embryo consists of an embryonal axis and two cotyledons. The portion of the embryonal axis above the level of cotyledons is the epicotyl, which terminates with the plumule or stem tip. The cylindrical portion below the level of cotyledons is hypocotyl that terminates at its lower end in the radicle or root tip. The root tip is covered with a root cap. • Only one cotyledon is present in embryos of monocotyledons. In the grass family the cotyledon is called scutellum. At its lower end the embryonal axis has the radicle and root cap enclosed in an undifferentiated sheath called coleorhiza. The portion of the embryonal axis above the level of attachment of scutellum is the epicotyl. Epicotyl has a shoot apex and a few leaf primordia enclosed in a hollow foliar structure, the coleoptile. • The seed is the final product of sexual reproduction in angiosperms. • Seeds are often described as fertilised ovules and are formed inside fruits. • A seed typically consists of seed coat(s), cotyledon (s) and an embryo axis. (b) • As ovules mature into seeds, the ovary develops into a fruit. Fig.: (a) A typical dicot embryo, (b) L.S. of an embryo of grass • The wall of the ovary develops into the wall of fruit called pericarp. • In most plants, by the time the fruit develops from the ovary, other floral parts degenerate and fall off. • However, in few species such as apple, cashew, strawberry, etc. the thalamus also contributes to fruit formation. Such fruits are called false fruits. 62

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• In contrast, true fruits develop only from the ovary. • In few species, fruits develop without fertilisation. Such fruits are called parthenocarpic fruits. Banana is an example of parthenocarpic fruit.

Albuminous and non-albuminous seed

• Mature seeds may be albuminous or non-albuminous. Albuminous seeds retain a part of endosperm as it is not completely used up during embryo development (e.g., wheat, maize, barley, castor, sunflower). Non-albuminous seeds have no residual endosperm as it is completely consumed during embryo development (e.g., pea, groundnut). Occasionally, in some seeds such as black pepper remnants of nucellus are also persistent. This residual persistent nucellus is the perisperm.

APOMIXIS AND POLYEMBRYONY

• A few flowering plants such as some species of Asteraceae and grasses have evolved a mechanism to produce seeds without fertilisation called apomixis. • There are several methods of apomictic development in seeds, two common methods are recurrent agamospermy and adventive embryony. • Agamospermy is the formation of seed that has an embryo formed without meiosis and syngamy.

Agamospermy Non-recurrent agamospermy • The embryo is haploid and therefore the seed having it is nonviable.

Recurrent agamospermy

• All the cells of the embryo sac are diploid as it is formed directly either from a nucellar cell (apospory) or diploid megaspore mother cell (diplospory).

• The diploid egg as well as other diploid cells of embryo sac can grow into normal embryos.

• Formation of embryo directly from diploid egg without fertilisation is called diploid parthenogenesis, e.g., apple, Poa. • Adventive embryony - An embryo develops directly from a diploid cell other than egg like that of nucellus and integument, e.g., Citrus, Opuntia. It gives rise to a condition called polyembryony or the phenomenon of having more than one embryo. In gymnosperms, polyembryony can also occur due to cleavage of growing embryo. It is called cleavage polyembryony. Occurrence of polyembryony due to fertilisation of more than one egg is called simple polyembryony while formation of extra embryos through sporophytic budding is called adventive polyembryony. • Polyembryony is common in onion, groundnut, mango, lemon, orange.

3. 4.

What type of outbreeding contrivance is found in Primula? What is the advantage of recurrent agamospermy over non-recurrent agamospermy?

APRIL 2018 1-c- OPSONIN

2-d- EPHYRA

3-f- TURION

4-a- PITUICYTES

5-g- RIBOPHORIN

6-h- PUTREFACTION

7-j- BLEPHAROPLAST

8-i- GRISEOFULVIN

9-e-BICOLLATERAL

10-b- POLLINIUM

Winner : Aswini Mura (West Bengal)

To easily remember the characteristics of monocots, the mnemonic “Many Smart People Take French” can be used as follows: Many

:

Monocots

Smart

:

Scattered vascular bundles

People

:

Parallel leaf venation

Take

:

Threes (units of floral parts)

French

:

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1.

2. 3.

4.

5. 6.

7.

8.

9.

Ectopic pregnancy is a condition of (a) inflammation of cervix during pregnancy (b) implantation of embryo in the oviduct rather than uterus (c) high blood pressure during pregnancy (d) birth of premature baby. The method of hybridisation of DNA with a labelled probe is called (a) Southern blotting (b) Northern blotting (c) Western blotting (d) Eastern blotting. Which of the following is not used in SCP production? (a) Methylophilus methylotrophus (b) Candida utilis (c) Rhizopus stolonifer (d) Fusarium graminearum Refer to the given figure and select the incorrect option. (a) The organism belongs to the Class Osteichthyes. (b) This organism is an egg laying female. (c) It always swims upright in the sea water. (d) The pelvic and caudal fins are absent in it. Capitulum inflorescence is a modification of (a) spike (b) umbel (c) spadix (d) catkin. Select the mismatched pair. (a) SA node – Initiation of heart beat (b) Neurogenic heart beat – Vertebrates (c) Mitral valve – Left atrium (d) Cardiomegaly – Enlarged heart Select the correct statement regarding apoenzyme. (a) It is heat stabled. (b) It takes part in group transfer reactions. (c) It is the non-protein organic part of the holoenzyme. (d) It is specific for an enzyme. In Hamburger’s phenomenon, the chloride ions move from (a) plasma to RBC (b) RBC to plasma (c) blood capillary to tissue cell (d) tissue cell to blood plasma. Intrafascicular cambium is a kind of (a) intercalary meristem (b) apical meristem (c) primary lateral meristem (d) secondary meristem.

10. Select the correct statement. (a) Indirect development of Schistosoma includes velliger and trochophore larva. (b) Cartilaginous fishes have homocercal caudal fin and cycloid scales. (c) In Hemidactylus, eyelids are movable and nictitating membrane is present. (d) Spider has 3 pairs of legs. 11. In which of the following amino acids, polar hydrocarbon is not present? (a) Serine (b) Glutamic acid (c) Alanine (d) Both (b) and (c) 64

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12. The following features occur during protein synthesis. (i) Movement of mRNA from the nucleus into the cytoplasm, where it binds to small subunit or the ribosomes. (ii) Aminoacylation of tRNA. (iii) Transcription of specific segments of DNA into mRNA molecules in the nucleus. (iv) Binding of N-terminal amino acid, methionine tRNA to the P-site of the ribosome. The tRNA anticodon pairs with AUG on mRNA. (v) Formation of peptide bond between first and second amino acids at the A-site. (vi) Release of the complete polypeptide chain from mRNA and the ribosomes. (vii) Migration of dipeptide to form a tripeptide and then a polypeptide. The correct order of events will be (a) (iii) – (ii) – (i) – (iv) – (v) – (vi) – (vii) (b) (i) – (ii) – (iii) – (iv) – (v) – (vi) – (vii) (c) (iii) – (i) – (ii) – (v) – (iv) – (vi) – (vii) (d) (iii) – (i) – (ii) – (iv) – (v) – (vii) – (vi) 13. Consider the type of life cycle given and select the incorrect option.

(a) Meiosis occurs at the time of spore formation in sporophytic plant. (b) Gametophytic plant is produced by germination of spores. (c) This life cycle is exhibited by most algae and some seed bearing plants. (d) This life cycle is exhibited by many bryophytes and pteridophytes. 14. A person having I AI A or I AI O genotype can donate blood to the person having blood groups. (a) B, AB (b) A, O (c) A, AB (d) A, B. 15. Select the mismatched pair. (a) Yellow fever - Viral disease (b) Diphtheria - Bacterial disease (c) Hansen’s disease - Rickettsial disease (d) Syphilis - Spirochaetal disease 16. “Species are groups of interbreeding natural populations that are reproductively isolated from other such groups”. This statement refers to (a) biological species concept (b) evolutionary species concept (c) morphological species concept (d) polytypic species concept.

17. DDT residues are rapidly passed through food chain causing biomagnification because DDT is (a) water soluble (b) lipid soluble (c) moderately toxic (d) non-toxic to aquatic animals. 18. A mule is produced by the interspecific hybridisation between (a) Hisardale and Merino rams (b) male donkey and female horse (c) female donkey and male horse (d) Merino rams and female horse. 19. Which of the following technique is employed in the test-tube baby programme? (a) Intra Cytoplasmic Sperm Injection (ICSI) (b) Intra Uterine Insemination (IUI) (c) Gamete Intra Fallopian Transfer (GIFT) (d) Zygote Intra Fallopian Transfer (ZIFT) 20. The table summarises the differences between habitat and niche. Habitat Niche (i) It supports a single species. It supports a number of species. (ii) It has number of environmental variables.

It has specific set of environmental regimes.

(iii) A species does not change its habitat.

A species may live in more than one niche.

Which of the above given differences are correct? (a) (i) only (b) (ii) and (iii) only (c) (iii) only (d) (i) and (iii) only 21. Identify A, B and C the given diagram showing microsporangium of a mature anther.

Hormone Receptor

A

B

C

26.

27.

A B C

(a) A-Middle layer, B-Endothecium, C-Tapetum (b) A-Endothecium, B-Tapetum, C-Middle layer (c) A-Endothecium, B-Middle layer, C-Tapetum (d) A-Tapetum, B-Middle layer, C-Endothecium 22. Which of the following is a correct match of ear part and its function? (a) Organ of Corti – Increases the efficiency of sound waves (b) Eustachian tube – Maintains body balance and posture (c) Tectorial membrane – Determines patterns of vibration of sound waves (d) Semicircular canal – Equalises the air pressure on either sides of the ear drum 23. Refer the given reaction. 2H2O → 4H+ + O2 + 4e– Where does this reaction take place in the chloroplasts of plants? (a) Outer surface of thylakoid membrane (b) Inner surface of thylakoid membrane (c) In the matrix (stroma) (d) Intermembrane space 24. Columns of Bertin in the kidneys of mammals are formed as extensions of (a) cortex in medulla (b) cortex in pelvis (c) medulla in pelvis (d) pelvis in ureter. 25. Refer the given diagrammatic representation of the mechanism of action of a protein hormone.

Ovarian cell membrane

28.

29.

30.

31.

In which of the following options correct labelling of A, B and C is given? A B C (a) Generation of Physiological Biochemical second messenger responses responses (b) Activation Biochemical Generation of of genes responses second messenger (c) Generation of Biochemical Physiological second messenger responses responses (d) Biochemical Activation Physiological responses of genes responses Colchicine is a cell poison which arrests cell division at ____ and can induce _____. (a) metaphase, parthenocarpy (b) anaphase, parthenocarpy (c) metaphase, polyploidy (d) anaphase, polyploidy Which of the following statements is incorrect for centrioles? (a) Both the centrioles in a centrosome lie perpendicular to each other. (b) Central proteinaceous hub is missing in a centriole. (c) Each centriole has an organisation like that of a cartwheel. (d) Centrioles are absent in angiosperms, higher gymnosperms, some algae and fungi. In glycolysis, substrate level phosphorylation occurs during conversion of (a) 3-phosphoglycerate to 2-phosphoglycerate (b) phosphoenol pyruvate to pyruvate (c) glyceraldehyde 3-phosphate to 1, 3-biphosphoglycerate (d) fructose-6-phosphate to fructose-1, 6-biphosphate. Which of the following helps in absorption of phosphorus from soil by plants? (a) Glomus (b) Rhizobium (c) Frankia (d) Anabaena Read the given statements and select the option that correctly identifies the incorrect ones. (i) Cytokinins are primarily concerned with cell division. (ii) C2H4 breaks seed and bud dormancy. (iii) ABA stimulates the opening of stomata. (iv) C2H4 initiates germination in peanut seeds, sprouting of potato tubers. (v) ABA is synergistic to GA. (a) (i), (ii) and (iv) (b) (iii) and (ii) (c) (iii) and (v) (d) (iv) and (v) Which of the following is not a viral disease of plants? (a) Red rot of sugarcane (b) Tobacco mosaic disease (c) Leaf curl of tomato (d) Tristeza disease of citrus

32. The floral formula (a) Fabaceae (c) Solanaceae

K(5) C(5) A5 G(2) belongs to the Family (b) Asteraceae (d) Liliaceae.

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33. The first transgenic animal for food production is (a) ALV-resistant chicken (b) Tracy (c) Rainbow trout (d) Transgenic salmon. 34. Which is not a method of controlling solid wastes? (a) Composting (b) Pyrolysis (c) Sludge burning (d) Cyclone collectors 35. Large quantities of monoclonal antibodies are produced from (a) B-cells (b) myeloma (c) hybridoma (d) T-lymphocytes. 36. According to Westergren method, erythrocyte sedimentation rate in male is (i) in 1st hour and in female it is (ii) in 1st hour. (a) (i) 0 – 4 mm (ii) 0 – 7 mm (b) (i) 0 – 5 mm (ii) 0 – 7 mm (c) (i) 0.5 – 1.5 mm (ii) 0.7 – 1 mm (d) (i) 0 – 7 mm (ii) 0 – 4 mm 37. Duct of Rivinus is associated with (a) sublingual glands (b) parotid glands (c) submandibular glands (d) gastric glands. 38. Functional residual capacity includes (a) residual volume and expiratory reserve volume (b) inspiratory reserve volume and residual volume (c) tidal volume and expiratory reserve volume (d) inspiratory reserve volume and expiratory reserve volume. 39. Which one is incorrect about sexual reproduction in fungi? (a) In gametangial contact male gamete is transferred to the oogonium through a fertilisation tube. (b) Male and female gametangia fuse directly in gametangial copulation. (c) Zygospore is formed in somatogamy. (d) Isogamous or heterogamous fusion occurs in planogametic copulation. 40. Select the correct statement from the following. (a) Chl. a and b absorb maximum light in red wavelengths only. (b) Photosynthetically active radiation is ranged between 300-700 nm. (c) Absorption spectrum is studied by spectrophotometer. (d) The first action spectrum was studied by Emerson by using a brown algae. Directions : In the following questions (41-60), a statement of assertion is followed by a statement of reason. Mark the correct choice as : (a) If both assertion and reason are true and reason is the correct explanation of assertion. (b) If both assertion and reason are true but reason is not the correct explanation of assertion. (c) If assertion is true but reason is false. (d) If both assertion and reason are false. 41. Assertion : Papaya is a dioecious plant. Reason : In papaya, both male and female flowers are borne on the same plant. 42. Assertion : The middle piece is called as power house of the sperm. Reason : In the middle piece of sperm, numerous mitochondria coiled round the axial filament are present providing energy for the movement of the sperm. 43. Assertion : Meiosis increases the chance of genetic variability in the population of a species. Reason : Variability is important with respect to evolution. 44. Assertion : Decapitation with widely used in tea plantation. Reason : Decapitation usually promotes the growth of apical buds. 45. Assertion : All sporozoans are endoparasites. 66

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46. 47. 48. 49. 50.

51.

52.

53.

54. 55. 56.

57. 58. 59. 60.

1. 6. 11. 16. 21. 26. 31. 36. 41. 46. 51. 56.

Reason : Sexual and asexual phases of life cycle occur in one or two different hosts. Assertion : Cyathea is called tree fern. Reason : Cyathea possesses with upright aerial stem. Assertion : UAA, UAG and UGA terminate protein synthesis. Reason : UAA, UAG and UGA are recognised by protein synthesis factors. Assertion : ADH reduces the volume of urine. Reason : ADH facilitates reabsorption of water by the distal part of nephrons. Assertion : Fever is second line of body defence. Reason : Mild fever activates phagocytes and inhibits the growth of microbes. Assertion : Cyclosporine is a good immunosuppressant. Reason : Cyclosporine appears to act at an early stage in the antigen receptor induced differentiation of T cells and blocks their activation. Assertion : Pectoral fins of sharks and flippers of dolphins are analogous organs. Reason : Analogous organs have the same fundamental structures but are different in functions. Assertion : There is no involvement of microorganisms in primary treatment of sewage water. Reason : Decomposition of organic matter occurs in secondary treatment. Assertion : Both PS I and PS II is involved in cyclic photophosphorylation. Reason : In cyclic photophosphorylation, the electron moves from PS II to PS I. Assertion : Herbivores are known as key industry animals. Reason : Herbivores convert plant matter into animal matter. Assertion : Xylem sap contains mineral salts. Reason : Salt uptake from soil occurs against concentration gradient. Assertion : Calcitonin restores the normal concentration of calcium ions in the blood. Reason : Calcitonin reduces the mobilisation of calcium ions from the bones when the concentration of calcium ions rises in the blood plasma. Assertion : Nodes of Ranvier are not present in non-myelinated nerve fibres. Reason : Nissl’s bodies are absent in non-myelinated nerve fibres. Assertion : Bees form a well-organised insect society. Reason : A division of labour is seen in their society. Assertion : Fermentation is both intra-and extracellular process. Reason : Fermentation is a type of respiration which does not require oxygen. Assertion : Population growth rate is also called birth rate. Reason : Population growth rate can never be negative. (b) (b) (c) (a) (c) (c) (a) (b) (c) (a) (c) (a)

2. 7. 12. 17. 22. 27. 32. 37. 42. 47. 52. 57.

ANSWER

(a) (d) (d) (b) (c) (b) (c) (a) (a) (c) (b) (c)

3. 8. 13. 18. 23. 28. 33. 38. 43. 48. 53. 58.

(c) (a) (c) (b) (b) (b) (d) (a) (b) (a) (d) (a)

KEY

4. 9. 14. 19. 24. 29. 34. 39. 44. 49. 54. 59.

(b) (c) (c) (d) (a) (a) (d) (c) (c) (a) (c) (b)

5. 10. 15. 20. 25. 30. 35. 40. 45. 50. 55. 60.

(a) (c) (c) (b) (c) (c) (c) (c) (a) (a) (b) (d)



NEET 1.

Which of the following period is known as the age of fishes? (a) Ordovician period (b) Silurian period (c) Devonian period (d) Carboniferous period

2.

Read the following statements and select the correct one. (i) Juvenile phase is the pre-reproductive phase in the life cycle of an individual. (ii) Bambusa tulda is a monocarpic plant. (iii) Carrot and radish are polycarpic. (iv) In estrus cycle, broken endometrium is passed out. (a) (i) and (iii) (b) (ii) and (iv) (c) (i) only (d) (i) and (ii)

3.

Which is not true about euglenoids? (a) They have a protein rich layer called pellicle instead of cell wall. (b) Mixotrophic mode of nutrition is found among them. (c) In most forms the cells have stiff cellulose plates. (d) They occur in fresh water habitat and in damp soils.

4.

5.

6.

7.

The epiphytic roots of Vanda (a) absorb mineral salts and moisture from the dust collected on bark (b) possess velamen which helps to absorb water from moist atmosphere (c) helps in the fixation on the surface of host plant (d) arise from nodes and store air from the atmosphere. The and (a) (b) (c) (d)

(i) cartilage forms articular surface at the joints of long bones (ii) cartilage occurs in the pubic symphysis. (i)-hyaline (ii)-white fibrous (i)-calcified (ii)-hyaline (i)-white fibrous (ii)-calcified (i)-hyaline (ii)-calcified

The given plant (a) is vascular but cryptogamae (b) do not have vessels in its xylem (c) have assimilatory tissues in its vegetative propagules (d) is aquatic species of hornworts. In some organisms karyokinesis is not followed by cytokinesis as a result of which multinucleate condition arises leading to the formation of syncytium as in case of

Warm up! Exam on 6 May 2018 th

(a) (b) (c) (d)

embryo development liquid endosperm of coconut trophomixis scutellum development.

8.

Match the column I with column II and select the correct option. Column I Column II A. Marginal placentation (i) Dianthus B. Free central (ii) Marigold placentation C. Axile placentation (iii) Acacia D. Basal placentation (iv) Lemon (a) A-(i), B-(iv), C-(ii), D-(iii) (b) A-(iii), B-(i), C-(iv), D-(ii) (c) A-(iii), B-(iv), C-(i), D-(ii) (d) A-(i), B-(ii), C-(iv), D-(iii)

9.

A mRNA, consisting of 282 nucleotides can produce a polypeptide chain of (a) 282 amino acids (b) 120 amino acids (c) 94 amino acids (d) 141 amino acids.

10. Ganong’s respirometer is used to determine (a) vital capacity (b) total lung capacity (c) inspiratory reserve volume (d) respiratory quotient. 11. Which of the following is incorrect for the given figure. Discharge corona Negatively charged wire

Clean air

Dirty air

Dust particles

Collection plate grounded Electrostatic precipitator

(a) Most widely used instrument, for the removal of particulate matter. (b) It can remove over 99% particulate matter present in the exhaust from a thermal power plant. (c) It works on the principle of dust separation by centrifugation force. (d) The velocity of the air between the plates must be low enough to allow the dust to fall. MT BIOLOGY

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12. Which of the following bacteria is not associated with denitrification? (a) Nitrocystis (b) Pseudomonas (c) Thiobacillus (d) Micrococcus

14. The following graph depicts changes in two populations (A and B) of herbivores in a grassland. A possible reason for these changes is that

Number of organisms

13. Read the given statements and select the correct option. Statement A : Veins have valves which prevent backward flow of blood. Statement B : The flow of blood in veins is not very fast because the blood flows under low pressure. (a) Both the statements are true but statement B is the correct explanation of A. (b) Both the statements are true but statement B is not the correct explanation of A. (c) Statement A is true but statement B is false. (d) Both the statements A and B are false.

18. If we take out a small drop of each of the following separately on glass slides which will not coagulate? (a) Blood from hepatic portal vein (b) Blood from pulmonary vein (c) Blood plasma (d) Blood serum 19. Examine the figure of gastric glands given below and identify the labelled parts A to D. Opening of gastric gland

A B Gastric pit

C D

B

(a) Population ‘A’ produced more offspring than population ‘B’. A (b) Population ‘A’ consumed Time the members of population ‘B’. (c) Population ‘B’ competed more successfully for food than population ‘A’. (d) Both plant populations shows allelopathy relationship. 15. Read the following statements and select the correct ones. (i) In simple cuboidal epithelium nuclei are rounded and lie in the centre of the cells. (ii) Non-keratinised epithelium is impermeable to water. (iii) Yellow elastic fibrocartilage makes cartilage flexible. (iv) Areolar tissue forms a shock absorbing cushion around the eye balls and kidneys. (a) (i) and (iii) (b) (i) and (ii) (c) (iii) and (iv) (d) (ii) and (iv) 16. Cladonia rangiferina is (a) regarded as ‘bread of heaven’ by Jews (b) the staple food of reindeer (c) used to prepare perfumes (d) the source of litmus. 17. Select the correct option regarding the phytohormone to which the given molecular structure belongs.

(a) (b) (c) (d)

A B Oxyntic cell Chief cells Argentaffin cell Oxyntic cells G cell Chief cells Oxyntic cell G cells

C Mucous cells Mucous cells Mucous cells Mucous cells

D Argentaffin cell Chief cell Argentaffin cell Chief cell

20. Which of the following statements is correct? (a) Vasa recta is well developed in cortical nephrons. (b) PCT and DCT are situated in the medulla of the kidney. (c) The glomerulus encloses the Bowman’s capsule. (d) The ascending limb of the Henle’s loop extends as the DCT. 21. Match column I with column II and select the correct option from the codes given below. Column I Column II (Skeletal Part) (Number of bones) A. Cranium (i) 29 B. Skull (ii) 8 C. Face (iii) 14 D. Hindlimb (iv) 24 E. Ribs (v) 30 (a) A-(i), B-(ii), C-(iii), D-(v), E-(iv) (b) A-(ii), B-(i), C-(iii), D-(v), E-(iv) (c) A-(i), B-(ii), C-(iii), D-(iv),E-(v) (d) A-(v), B-(iv),C-(iii), D-(ii), E-(i) 22. The 3rd, 6th and 11th cranial nerves are respectively (a) oculomotor, abducens and spinal accessory (b) oculomotor, trigeminal and spinal accessory (c) optic, facial and spinal accessory (d) trochlear, abducens and vagus. 23. The given table enlists various hormones and their chemical nature. Select the option which completes the table.

(a) This hormone promotes femaleness in most flowers. (b) This hormone promotes apical dominance. (c) This hormone usually decreases the size of stem, leaves, flowers and fruits. (d) This hormones breaks seed dormancy by synthesis of certain enzymes. 68

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Hormone

Chemical composition

(i)

Peptide (ii) (iii) Amino-acid derivative

Testosterone

Thyroxine (iv)

(a) (b) (c) (d)

(i) Cortisol Insulin Cortisol Insulin

(ii) Steroid Protein Protein Steroid

(iii) Polypeptide Polypeptide Amine Amine

(iv) Estradiol Epinephrine Estradiol Epinephrine

24. Select the correct pathway of water movement inside the root. (a) Epidermis → Endodermis → Cortex → Pericycle → Xylem (b) Epidermis → Cortex → Endodermis → Pericycle → Xylem (c) Epidermis → Endodermis → Pericycle → Cortex → Xylem (d) Epidermis → Cortex → Pericycle → Endodermis → Xylem 25. It is a common practice to keep few riped bananas with unriped bananas so that, (a) riped bananas can be prevented from rottening (b) unriped bananas ripe quickly (c) unriped bananas stay as it is for a longer time (d) none of these. 26. Which of the following contraceptive methods has poor reversibility? (a)

(c)

(b)

(d)

(a) (i) and (ii) (c) (iii) and (iv)

(b) (ii) and (iii) (d) (i) and (iv)

31. The purpose of biological treatment of waste water is to (a) reduce BOD (b) increase BOD (c) reduce sedimentation (d) increase sedimentation. 32. Read the following statements and select the correct ones. (i) Same kind of sticky ends are produced when a DNA has been cut by different restriction enzymes. (ii) Exonucleases make cuts at specific positions within the DNA. (iii) Hind II was the first restriction endonuclease to be isolated. (iv) A bacteriophage has the ability to replicate within bacterial cells by integrating its DNA with bacterial DNA. (v) Presence of more than one recognition sites within the vector facilitates the gene cloning. (a) (i), (iii) and (v) (b) (i) and (iv) (c) (iii) and (iv) (d) (ii), (iii) and (iv) 33. Which of the following is not a benefit of transgenic animals? (a) Investigation of new treatments for diseases (b) Early detection of diseases (c) Testing the safety of vaccines (d) To produce useful biological products 34. Many freshwater organisms cannot live for long in seawater because the surrounding water will be ___ to body cells and ____ may occur. (a) hypertonic, exosmosis (b) hypertonic, endosmosis (c) hypotonic, exosmosis (d) hypotonic, endosmosis 35. Which kind of pyramid is represented by the given figure?

27. Read the given statements and select the correct option. Statement A : Test cross is used to determine an unknown genotype within one breeding generation. Statement A : Test cross is a cross between F1 hybrid and dominant parent. (a) Both statements A and B are correct and statement B is the correct explanation of statement A. (b) Both statements A and B are correct but statement B is not the correct explanation of statement A. (c) Statement A is correct and statement B is incorrect. (d) Both statements A and B are incorrect. 28. The preserved fossil remains of Archaeopteryx show that (a) it was a flying reptile from the permian period (b) reptiles gave rise to birds during jurassic period (c) it was a flying reptile in the triassic period (d) reptiles gave rise to birds during permian period. 29. A disease sometimes found in persons above the age of 40 years which is characterised by poor CNS coordination, forgetfulness and tremors of hands is (a) epilepsy (b) Alzheimer’s disease (c) migraine (d) schizophrenia. 30. Study the following statements regarding inbreeding and select the incorrect ones. (i) The inbreeding strategies allow the desirable qualities of two different breeds to be combined. (ii) It increases homozygosity. (iii) It also helps in elimination of less desirable genes. (iv) Continued inbreeding increases fertility and productivity.

Dry weight (Kg m–2) PC

21 4

PP

(a) (b) (c) (d)

Pyramid of numbers in terrestrial ecosystem Pyramid of biomass in terrestrial ecosystem Pyramid of biomass in aquatic ecosystem Pyramid of numbers in aquatic ecosystem

36. ‘Every species has a right to live’. What kind of value implies on the conservation of biodiversity? (a) Narrowly utilitarian (b) Broadly utilitarian (c) Ethical (d) Aesthetic 37. The radioactive fallout can cause (i) near-immediate effect only (ii) mutation in the DNA of living cells (iii) long term effect on future generation (iv) tissue damage and killing of cells only (a) (i) and (ii) are correct. (b) (ii) and (iii) are correct. (c) (ii) and (iv) are correct. (d) only (ii) is correct. 38. Select the correctly matched pair. (a) Supermale – XXYY (b) Klinefelter’s syndrome – XO (c) Superfemale – XXXX (d) Sterile male – XYY 39. Highly pleomorphic, smaller microorganisms, forming elementary bodies are (a) actinomycetes (b) mycoplasma (c) diatoms (d) virus. MT BIOLOGY

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40. Tensor tympani and stapedius muscles are present in (a) external ear (b) middle ear (c) inner ear (d) cochlea and utriculus.

51. Identify the parts marked as A , B and C in the given figure showing ATP synthesis through chemiosmosis.

41. Which event causes depolarisation of neuron? (a) Influx of K+ (b) Influx of Na+ (c) Influx of any positively charged on (d) Efflux of negatively charged organic ions 42. Absence of enterokinase causes (a) no conversion of chymotrypsinogen into chymotrypsin (b) no secretion of gastric juice (c) more secretion of gastric juice and gastric motility also increases (d) inhibition in release of bile juice from gall bladder. 43. In our tissues dissociation of oxyhaemoglobin occurs due to the (a) low O2 concentration and high CO2 concentration (b) low concentration of O2 and CO2 both (c) high concentration of O2 and CO2 both (d) high O2 concentration and low CO2 concentration. 44. After organ transplantation cyclosporin A is given to the patient because (a) it is a immune enhancer drug (b) It is an immunosuppressive drug (c) it is an immunologically inert substance (d) it increases the count of WBCs in recipient. 45. Head of cockroaches can move in all directions because (a) tentorium of head is very flexible which provide greater mobility (b) prothorax forms an extension which behaves as flexible neck (c) head capsule forms an extension which behaves as flexible neck (d) whole neck is made up of arthrodial membrane. 46. What is the location of troponin in the process of muscle contraction? (a) Attached to myosin filament (b) Attached to tropomyosin (c) Attached to myosin cross-bridges (d) Attached to T-tubule 47. The permissible use of technique amniocentesis is for (a) detecting sex of the unborn foetus (b) artificial insemination (c) transfer of embryo into the uterus of a surrogate mother (d) detecting any genetic abnormality. 48. Introduction of genetically modified food is not desirable because (a) it will affect economy of developing countries (b) the products are less tasty (c) they are costly (d) they could affect the biodiversity and environment. 49. The process of introduction of weakened inactivated pathogen into human body is called (a) immunisation (b) vaccination (c) attenuation (d) none of these. 50. Genetic material found in human immuno deficiency virus (HIV) is (a) double-stranded RNA (b) two strands of single-stranded RNA (c) double-stranded DNA (d) single-stranded DNA. 70

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(a) (b) (c) (d)

A Thylakoid lumen Thylakoid lumen Chloroplast lumen Chloroplast lumen

B F0 F1 F0 F1

C F1 F0 F1 F0

52. A test tube containing molasses solution and yeast is kept in a warm place overnight. The gas collected from this mixture (a) extinguishes the flame (b) bursts into flame when ignited (c) turns lime water milky (d) both (a) and (c). 53. Which of the following does not affect the genetic variation in a population? (a) Chromosomal mutation (b) Gene migration (c) Genetic drift (d) Balanced polymorphism 54. Which of the following shows the correct sequence of steps of plant tissue culture? (a) Sterilisation → hardening → selection of explant → inoculation → regeneration → plantlet transfer (b) Selection of explant → inoculation → regeneration → sterilisation → hardening → plantlet transfer (c) Selection of explant → sterilisation → inoculation → regeneration → hardening → plantlet transfer (d) Hardening → sterilisation → selection of explant → inoculation → regeneration → plantlet transfer 55. A jacket of sterile cells around the sperms and eggs is an adaptation to life on land, in (a) Riccia (b) Fucus (c) Laminaria (d) Ulothrix. 56. Given structural formula is correctly identified alongwith its related function by which of the following options?

HO

(a) (b) (c) (d)

Cholesterol Lecithin Triglyceride Adenosine

– – – –

A component of animal cell membrane A component of cell membrane An energy source A component of nucleic acids

57. Which is the best way to separate intact chloroplast from green leaves of angiospermic plant? (a) Petrol-ether (b) Chloroform (c) 10% sucrose solution (d) Alcohol 58. Phragmoplast is related to (a) division of nucleolus (b) cell elongation (c) cytokinesis (d) assemblage of chromosomes at metaphase. 59. Flowering plants have developed certain outbreeding devices to discourage self-pollination and to encourage cross-pollination. One of these is not an example of such outbreeding device. (a) Dicliny (b) Dichogamy (c) Herkogamy (d) Cleistogamy 60. The early stage human embryo distinctly possesses (a) gills (b) gill slits (c) external ear (pinna) (d) eyebrows. 61. Read the following statements carefully and select the correct statement(s). (i) hPL plays a major role in parturition. (ii) Foetus shows movements first time in the 7th month of pregnancy. (iii) Signal for parturition comes from fully developed foetus and placenta. (iv) Embryo’s heart is formed after the 2nd month of pregnancy. (a) (ii) and (iii) (b) (iii) only (c) (ii) and (iv) (d) (i) and (iv) 62. Which of the following equations correctly represents VerhulstPearl logistic growth? (a)

(b)

(c)

(d)

63. Identify A, B, C and D in the given diagram of mRNA. C

A

D 3

5 B

A

(a) Methylated

cap (b) Poly A tail (c)

Methylated cap (d) Methylated cap

B

C

Initiation Termination codon codon Termination Initiation codon codon Non-coding Coding region region Coding Non-coding region region

D Poly A tail Methylated cap Poly A tail Poly A tail

64. The rate of formation of new organic matter by rabbit in a grassland, is called (a) net productivity (b) secondary productivity (c) net primary productivity (d) gross primary productivity.

65. Study the pedigree chart of a family showing the inheritance of sickle-cell anaemia.

The trait traced in the above pedigree chart is (a) dominant X-linked (b) recessive X-linked (c) autosomal dominant (d) autosomal recessive. 66. Scientific names are derived from Latin language or are latinised. This is because (a) Latin is a dead language (b) Latin is more popular than other languages (c) Latin is the oldest language (d) all of these. 67. Halobacterium is (a) aerobic chemoautotroph (b) aerobic photoautotroph (c) anaerobic chemoautotroph (d) heterotroph. 68. Cysteine and methionine contain one common element that is (a) magnesium (b) sulphur (c) nitrogen (d) potassium. 69. Which one is incorrect among the followings? (a) Metaxylem is the later formed xylem. (b) Protoxylem elements are capable of being stretched. (c) Metaphloem is made up of smaller and narrower elements. (d) Protophloem is short lived and gets crushed. 70. Insects with incomplete metamorphosis are (a) hemimetabolous (b) ametabolous (c) paurometabolous (d) holometabolous. 71. Triglycerides are fatty acid esters of glycerol, which are formed by the esterification of ____ molecule(s) of fatty acids with ____ molecule(s) of glycerol. (a) one, two (b) one, three (c) three, one (d) two, one 72. The biochemical objective of PS I is to (a) oxidise NADPH (b) hydrolyse ATP (c) phosphorylate ADP (d) reduce NADP+. 73. When two molecules of acetyl-CoA enter the TCA cycle, net gain at the end of the cycle is (a) 2NADH2 + 2FADH2 + 1GTP (b) 3NADH2 + 2FADH2 + 2GTP (c) 6NADH2 + 2FADH2 + 2GTP (d) 3NADH2 + 1FADH2 + 4GTP. 74. Which of the following statements is incorrect? (a) Mucosal epithelium has goblet cells which secrete mucus for lubrication. (b) Mucosa forms gastric glands in the stomach and crypts in between the bases of villi in intestine. (c) Cells lining the villi has brush border or microvilli. (d) All the four basic layers in the wall of gut never show modifications in different parts of the alimentary canal. MT BIOLOGY

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75. The anther wall consists of four wall layers where (a) tapetum lies just inner to endothecium (b) middle layers lie between endothecium and tapetum (c) endothecium lies inner to middle layers (d) tapetum lies next to epidermis. 76. The sperms undergo physiological maturation, acquiring increased motility and fertilising capacity in (a) seminiferous tubules (b) vasa efferentia (c) epididymis (d) vagina. 77. Chromosome maps/ genetic maps were first prepared by (a) Sutton and Boveri (1902) (b) Bateson and Punnett (1906) (c) Morgan (1910) (d) Sturtevant (1911). 78. In transcription in eukaryotes, heterogenous nuclear RNA (hnRNA) is transcribed by (a) RNA polymerase I (b) RNA polymerase II (c) RNA polymerase III (d) all of these. 79. The pathogen Microsporum responsible for ringworm disease in humans belongs to the same kingdom as that of (a) Taenia, a tapeworm (b) Ascaris, a roundworm (c) Rhizopus, a mould (d) Wuchereria, a filarial worm. 80. Which of the following is an example of mutation breeding? (a) Pusa Swarnim, resistant to white rust (b) Mung bean, resistant to yellow mosaic virus (c) Pusa Sadabahar, resistant to chilli mosaic virus (d) Pusa Gaurav, resistant to aphids 81. Nitrogen fixation in root nodules of Alnus is brought about by (a) Frankia (b) Azorhizobium (c) Bradyrhizobium (d) Clostridium. 82. In a polymerase chain reaction after the denaturation step why the mixture needs to cool down to a lower temperature? (a) To permit specific annealing of the primers. (b) To give a halt to the reaction mixture. (c) To increase the activity of enzyme Taq polymerase. (d) To obtain the multiple copies of the DNA. 83. Which variety of rice was patented by a U.S. company even though the highest number of varieties of this rice are found in India? (a) Sharbati Sonora (b) Co-667 (c) Basmati (d) Lerma Rojo 84. The prickly pear cactus became unusually abundant after its introduction in Australia, because it (a) had no coevolved herbivores (b) formed new mycorrhizal association (c) lost its thorns (d) all of these. 85. In a comparative study of grassland ecosystem and pond ecosystem, it may be observed that (a) the abiotic components are almost similar (b) the biotic components are almost similar (c) both biotic and abiotic components are different (d) primary and secondary consumers are similar. 86. Identify the wrong statement regarding post-fertilisation development. (a) The ovary wall develops into pericarp. (b) The outer integument of ovule develops into tegmen. 72

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(c) The fusion nucleus (triple nucleus) develops intoendosperm. (d) The ovule develops into seed. 87. A patient of diabetes mellitus excretes glucose in urine even when he is kept on a carbohydrate free diet. It is because (a) fats are catabolised in adipose tissues to form glucose (b) amino acids are catabolised in kidney to form glucose (c) amino acids are discharged in blood stream from liver (d) glycogen from muscles is released in blood stream. 88. Cell bodies of neurons bringing afferent information into the spinal cord are located in (a) dorsal root ganglia (b) ventral root ganglia (c) gray matter of the spinal cord (d) white matter of the spinal cord. 89. Which of the following statement is incorrect regarding biodiversity? (a) Biodiversity deals with biological and geographical units such as genes, chromosomes, species, families and biogeographic regions. (b) Biodiversity is an addition sum of genetic, taxonomic and ecosystem diversity. (c) It is a measure of the amount of resources shared by the human population. (d) None of these 90. A lake near a village suffered heavy mortality of fishes within a few days. Which of the following statements could be the correct explanation for this? (i) Lots of urea and phosphate fertilizers were used in the crops in the nearby fields. (ii) The croplands of the village were sprayed with DDT. (iii) The lake water turned green and stinky. (iv) Phytoplankton populations in the lake declined initially thereby greatly reducing photosynthesis. (a) (i) and (iii) (b) (i) and (ii) (c) (ii) and (iii) (d) (iii) and (iv)

ANSWER 1. 6. 11. 16. 21. 26. 31. 36. 41. 46. 51. 56. 61. 66. 71. 76. 81. 86.

(c) (c) (c) (b) (b) (c) (a) (c) (b) (b) (a) (a) (b) (a) (c) (c) (a) (b)

2. 7. 12. 17. 22. 27. 32. 37. 42. 47. 52. 57. 62. 67. 72. 77. 82. 87.

(d) (b) (a) (d) (a) (c) (c) (b) (a) (d) (d) (d) (a) (a) (d) (d) (a) (a)

3. 8. 13. 18. 23. 28. 33. 38. 43. 48. 53. 58. 63. 68. 73. 78. 83. 88.

(c) (b) (b) (d) (d) (b) (b) (c) (a) (d) (d) (c) (c) (b) (c) (b) (c) (a)

KEY 4. 9. 14. 19. 24. 29. 34. 39. 44. 49. 54. 59. 64. 69. 74. 79. 84. 89.

(b) (c) (c) (a) (b) (b) (a) (b) (b) (b) (c) (d) (b) (c) (d) (c) (a) (c)

5. 10. 15. 20. 25. 30. 35. 40. 45. 50. 55. 60. 65. 70. 75. 80. 85. 90.

(a) (d) (a) (d) (b) (d) (c) (b) (b) (b) (a) (b) (d) (a) (b) (b) (c) (b) 

Time Allowed : 3 hours

Maximum Marks : 70 GENERAL INSTRUCTIONS

(i) There are total 26 questions in five sections in the question paper. All question are compulsory. (ii) Section A contains questions number 1 to 5. Very Short Answer type questions of one mark each. (iii) Section B contains questions number 6 to 10. Short Answer type-I questions of two marks each. (iv) Section C contains questions number 11 to 22. Short Answer type-II questions of three marks each. (v) Section D contains question number 23. Value Based Question of four marks. (vi) Section E contains questions number 24 to 26. Long Answer type questions of five marks each. (vii) There is no overall choice in the question paper, however, an internal choice is provided in one question of two marks, one question of three marks and all three questions of five marks. An examinee is to attempt any one question out of the two given in the question paper with the same question number.

SECTION - A 1. How do cytokine barriers provide innate immunity in humans? 2. Write the dual purpose served by deoxyribonucleoside triphosphates in polymerisation. 3. Write the names of the following : (a) A 15 mya primate that was ape-like. (b) A 2 mya primate that lived in East African grasslands. 4. Mention the chemical change that proinsulin undergoes, to be able to act as mature insulin. 5. Name two diseases whose spread can be controlled by the eradication of Aedes mosquitoes. SECTION - B 6. How did a citizen group called Friends of Arcata Marsh, Arcata, California, USA, help to improve water quality of the marshland using Integrated Waste Water Treatment? Explain in four steps. 7. Your advice is sought to improve the nitrogen content of the soil to be used for cultivation of a non-leguminous terrestrial crop. (a) Recommend two microbes that can enrich the soil with nitrogen. (b) Why do leguminous crops not require such enrichment of the soil? 8. You have obtained a high yielding variety of tomato. Name and explain the procedure that ensures retention of the

desired characteristics repeatedly in large populations of future generations of the tomato crop. 9. (a) Name the source plant of heroin drug. How is it obtained from the plant? (b) Write the effects of heroin on the human body. 10. With the help of an algebraic equation, how did HardyWeinberg explain that in a given population the frequency of occurrence of alleles of a gene is supposed to remain the same through generations? OR Although a prokaryotic cell has no defined nucleus, yet DNA is not scattered throughout the cell. Explain. SECTION - C 11. (a) Differentiate between analogous and homologous structures. (b) Select and write analogous structures from the list given below : (i) Wings of butterfly and birds (ii) Vertebrate hearts (iii) Tendrils of Bougainvillea and Cucurbita (iv) Tubers of sweet potato and potato. 12. How has the use of Agrobacterium as vectors helped in controlling Meloidogyne incognita infestation in tobacco plants? Explain in correct sequence. MT BIOLOGY

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13. (a) “India has greater ecosystem diversity than Norway”. Do you agree with the statement? Give reasons in support of your answer. (b) Write the difference between genetic biodiversity and species biodiversity that exists at all the levels of biological organisation. OR Explain the effect on the characteristics of a river when urban sewage is discharged into it. 14. Explain the mechanism of ‘sex determination’ in birds. How does it differ from that of human beings? 15. Explain outbreeding, outcrossing and crossbreeding practices in animal husbandry. 16. (a) Organic farmers prefer biological control of diseases and pests to the use of chemicals for the same purpose. Justify. (b) Give an example of a bacterium, a fungus and an insect that are used as biocontrol agents. 17. (a) How has the development of bioreactor helped in biotechnology? (b) Name the most commonly used bioreactor and describe its working. 18. Explain the roles of the following with the help of an example each, in recombinant DNA technology : (a) Restriction enzymes (b) Plasmids. 19. Differentiate between parthenocarpy and parthenogenesis. Give one example of each. 20. Medically it is advised to all young mothers that breastfeeding is the best for their newborn babies. Do you agree? Give reasons in support of your answer. 21. Draw a diagram of a mature human sperm. Label any three parts and write their functions. 22. (a) Expand VNTR and describe its role in DNA fingerprinting. (b) List any two applications of DNA fingerprinting technique. SECTION - D 23. Looking at the deteriorating air quality because of air pollution in many cities of the country, the citizens are very much worried and concerned about their health. The doctors have declared health emergency in the cities where the air quality is very severely poor. (a) Mention any two major causes of air pollution. (b) Write any two harmful effects of air pollution to plants and humans. (c) As a captain of your school Eco-club, suggest any two programmes you would plan to organise in the school so as to bring awareness among the students on how to check air pollution in and around the school. 74

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SECTION - E 24. (a) Write the scientific name of the organism Thomas Hunt Morgan and his colleagues worked with for their experiments. Explain the correlation between linkage and recombination with respect to genes as studied by them. (b) How did Sturtevant explain gene mapping while working with Morgan? OR (a) State the ‘central dogma’ as proposed by Francis Crick. Are there any exceptions to it? Support your answer with a reason and an example. (b) Explain how the biochemical characterisation (nature) of ‘Transforming Principle’ was determined, which was not defined from Griffith’s experiments. 25. (a) Following are the responses of different animals to various abiotic factors. Describe each one with the help of an example. (i) Regulate (ii) Conform (iii) Migrate (iv) Suspend (b) If 8 individuals in a population of 80 butterflies die in a week, calculate the death rate of population of butterflies during that period. OR (a) What is a trophic level in an ecosystem? What is ‘standing crop’ with reference to it? (b) Explain the role of the ‘first trophic level’ in an ecosystem. (c) How is the detritus food chain connected with the grazing food chain in a natural ecosystem? 26. (a) Describe any two devices in a flowering plant which prevent both autogamy and geitonogamy. (b) Explain the events upto double fertilisation after the pollen tube enters one of the synergids in an ovule of an angiosperm. OR (a) Explain menstrual cycle in human females. (b) How can the scientific understanding of the menstrual cycle of human females help as a contraceptive measure? SOLUTIONS 1. Certain cells when infected with virus, they produce cytokines such as interferon, which diffuse to healthy neighbouring cells and stimulates them to produce biochemicals, that block viral replication. When these cells become infected, the viruses are unable to take over the protein synthetic machinery to manufacture more of themselves and ultimately the spread of infection halts. This way cytokine barriers provide innate immunity in humans. 2. Deoxyribonucleoside triphosphates such as dATP, dCTP, dGTP and dTTP serve dual purpose during DNA replication.

3. (b) 4.

5. 6.

7. (b)

8.

9.

(b)

They act as substrates i.e., nucleotides for the replication process as well as provide energy for the polymerisation of nucleotides by cleavage of high energy terminal phosphate bonds. (a) Dryopithecus was apelike primate about 15 mya. Australopithecus lived in East African grasslands about 2 mya. Proinsulin has three polypeptide chains (A, B and C) which need to be processed before it becomes fully mature and functional insulin. C peptide chain is removed during maturation of insulin and has only two polypeptide chains i.e., A-chain and B-chain joined by disulphide bond are present in mature insulin. Chikungunya and dengue can be controlled by the eradication of Aedes mosquitoes. In the town of Arcata situated along the Northern Coast of California, an integrated waste water treatment process was developed with the help of biologist from Humboldt State University. Waste water is treated in the following manner : (i) Waste water is filtered to remove floating and large suspended solids. (ii) Precipitated solids (sediments) are removed in the next step. (iii) The clear water is now chlorinated with chlorine or perchlorate salt. This treated water contains lots of heavy metals and other dangerous pollutants. (iv) In this step, a series of six connected marshes in 60 hectares of marshland seeded with bacteria, algae, fungi and plants, which absorb, assimilate and neutralise the pollutants. The naturally purified water is the then allowed to flow out. (a) Azotobacter and Azospirillum. Leguminous crops have symbiotic nitrogen fixing bacteria such as Rhizobium that live in the root nodules of these plants. These bacteria obtain food and shelter from the plant and in return they trap nitrogen directly from the atmosphere which they provide to the plant. The retention of the desired characteristics repeatedly in the future generations of the tomato crop can be done by micropropagation which is a type of vegetative propagation. This procedure helps in rapid multiplication of plant in a short period of time and in less space. (a) Heroin is obtained from the poppy plant (Papaver somniferum). It is obtained by acetylation of morphine which is extracted from the latex of poppy plant. Some of the effects of heroin on the human body are as follows : (i) It is a depressant and slows down body functions It also induces drowsiness and lethargy.

(ii) Other effects include indigestion, reduced vision, decreased weight, sterility and total loss of interest in work. 10. In a given population one can find out the frequency of occurrence of alleles of a gene or a locus. This frequency is supposed to remain fixed and even remain the same through generations. Hardy-Weinberg principle stated it using algebraic equations which says that allele frequencies in a population are stable and is constant from generation to generation. The gene pool i.e., total genes and their alleles in a population remains constant. This is called genetic equilibrium. Sum total of all the allelic frequencies is 1. Individual frequencies, for example, can be named ‘p’, ‘q’, etc. In a diploid, ‘p’ and ‘q’ represent the frequency of allele ‘A’ and allele ‘a’. The frequency of ‘AA’ individuals in a population is simply p2. This is simply stated in another ways, i.e., the probability that an allele A with a frequency of ‘p’ appear on both the chromosomes of a diploid individual is simply the product of the probabilities, i.e., ‘p2’. Similarly of ‘aa’ is ‘q2’, of ‘Aa’ ‘2pq’. Hence, p2 + 2pq + q2 = 1. This is a binomial expansion of (p + q)2. When the measured frequency differs from expected values, the difference (direction) indicates the extent of evolutionary change. Disturbance in genetic equilibrium, or Hardy-Weinberg equilibrium, i.e., change of frequency of alleles in a population would then be interpreted as resulting in evolution. OR In prokaryotes, DNA lies in the cytoplasm which is supercoiled (coiled and recoiled) with the help of RNAs and non-histone basic proteins like polyamines. DNA being negatively charged is held in place with the help of these proteins that have positive charges in a region termed as nucleoid. The DNA in nucleoid is organised in large loops held by proteins. 11. (a) Differences between analogous and homologous structures are as follows : Analogous structures (i) They show superficial resemblance but their internal structure is quite different.

Homologous structures They differ morphologically but they have similar internal structure.

(ii) They develop in unrelated organisms. (iii) They have similar functions. (iv) Analogous organs show convergent evolution.

They develop in related organisms. They perform different functions. Homologous organs show adaptive radiation (divergent evolution).

(v) Example : Stings of Example : Vertebrate honey bee and scorpion. forelimbs. MT BIOLOGY

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(b) (i) Wings of butterfly and birds show analogy as the basic structure of the wings of the insects is different from the wings of birds, however, their function is similar. (ii) Vertebrates hearts show structural homology. (iii) Thorns (not tendrils) of Bougainvillea and tendrils of Cucurbita both arise in the axillary position thus, show homology. (iv) Sweet potato (root modification) and potato (stem modification) show analogy. 12. A nematode Meloidogyne incognita infects the roots of tobacco plants and causes a great reduction in yield. A novel strategy that was adopted to prevent this infestation was based on the process of RNA interference (RNAi), i.e., silencing of gene expression using a dsRNA. It involves silencing of specific mRNA due to complementary dsRNA molecule that binds to and prevents translation of mRNA (silencing). Using Agrobacterium vectors, nematodespecific genes were introduced into the host plant (tobacco plant). The introduction of DNA was such that it produced both sense and anti-sense RNA in the host cells. These two RNAs being complementary to each other formed a dsRNA (double stranded RNA) that initiated RNAi and thus, silenced specific mRNA of the nematode. The correct sequence of steps involved in making tobacco plant resistant to nematode are: (i) RNase enzyme called ‘dicer’ cuts all dsRNA molecules into small interfering RNAs (siRNAs) (21-23 nucleotides long). (ii) Each siRNA complexes with ribonucleases (distinct from dicer) to form an RNA-induced silencing complex (RISC). (iii) The siRNA unwinds and RISC is activated. (iv) The activated RISC targets complementary mRNA molecules. The siRNA strands act as guides where the RISCs cut the transcripts in an area where the siRNA binds to the mRNA. This destroys the mRNA. (v) When mRNA of the parasite is destroyed, no parasite proteins are synthesised that resulted in the death of the parasite (nematode) in the transgenic host. Thus, the transgenic plant gets itself protected from the parasite. 13. (a) Yes, India has greater ecosystem diversity than Norway as India comes under the tropical region whereas, Norway lies in temperate region. Tropical regions account for greater biological diversity as they have deserts, rain forests, mangroves, coral reefs, wetlands, estuaries and alpine meadows than temperate regions. In tropical region more solar energy is available that also promotes higher productivity and increased biological diversity. (b) Differences between genetic and species biodiversity are as follows : 76

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Genetic biodiversity

Species biodiversity

(i)

It is related to the number of genes and their alleles found in organisms.

It is related to number and distribution of species found in an area.

(ii)

It is trait of the species.

It is trait of a community.

(iii)

It influences the adaptability and distribution of a species in diverse habitats.

It influences biotic interactions and stability of the community.

(iv)

Example : India has more than 50,000 genetically different strains of rice and 1,000 varieties of mango.

Example : Western ghats have greater amphibian species diversity as compared to Eastern ghats.

OR Urban sewage includes domestic sewage (soaps, detergents, household wastes, feces, etc.) and industrial effluents (toxic metals, chemicals, etc.) which flow into the river through sewers. It also includes animal wastes, dumping of worship materials, ashes of dead bodies, bathing of animals, etc. Effects of sewage discharge in a river are : (i) Water becomes unfit for bathing and drinking and also for domestic or industrial use as it becomes coloured, turbid with a lot of particulate matter floating on water. (ii) Domestic sewage primarily contains biodegradable organic matter which is rich in nitrates and phosphates. These nitrates and phosphates encourage a thick bloom of planktonic algae that are toxic to humans and animals. Algal bloom also supports the growth of floating plants such as water hyacinth that cut-off sunlight for submerged plants. This results in organic loading of the rivers causing, depletion of oxygen content of the water. This suffocates the fish and other aquatic life. Consequently, river become highly polluted. (iii) Domestic sewage can be decomposed by microorganisms in the presence of oxygen. Biochemical oxygen demand (BOD) is the amount of oxygen required by the microorganisms in milligrams in five days to completely decompose the organic matter present in one litre of polluted water at 20°C. Higher the amount of oxygen consumed, greater is the degree of organic pollutants. So, the input of domestic sewage increases the BOD of the river because microorganisms consume oxygen during aerobic decomposition of organic wastes. This inturn decreases the dissolved oxygen in the river leading to death of large number of aquatic animals such as fish which disturbs numerous food chains. Hot water is released by industries that contains a variety of organic and inorganic residues which heavily pollute the river water.

14. In case of birds, the type of sex determination is ZW-ZZ type. Female has two different sex chromosomes (AA + ZW) whereas male has a pair of same chromosomes (AA + ZZ). As the female has heteromorphic sex chromosomes, the female is heterogametic and produces two types of eggs, (A + Z) and (A + W). The male gametes or sperms are of one type (A + Z). Therefore, in birds, sex is determined by female. Chromosomal determination of sex in human beings is of XX-XY type. Human beings have 22 pairs of autosomes and one pair of sex chromosomes. The females possess two homomorphic sex chromosomes, named XX while. The males have two heteromorphic sex chromosomes, i.e., XY. All the ova formed by female are similar in their chromosome type (22 + X). Therefore, females are homogametic. The male gametes or sperms produced by human males are of two types, gynosperms (22 + X) and androsperms (22 + Y). Human males are therefore, heterogametic. Thus, the genetic makeup of the sperm determines the sex of the child in case of human. 15. Outbreeding is the breeding of the unrelated animals which may be between individuals of the same breed, but without a common ancestors for 4-6 generations, or between different breeds or different species (interspecific hybridisation). Outcrossing is the mating of animals within the same breed but having no common ancestors on either side of their pedigree, up to 4–6 generations. The offspring of such a cross is called as an outcross. It is the best breeding method for animals that are below average in productivity in milk production, growth rate in beef cattle, etc. Sometimes only a single outcross helps to overcome inbreeding depression. In crossbreeding, superior males of one breed are mated with superior females of another breed. Many new animal breeds have been developed by this strategy and it gives better breeds. For example, cows of an inferior breed may be mated to bulls of a superior breed to get better progeny. Hisardale is a new breed of sheep developed in Punjab by crossing Bikaneri ewes and Marino rams. 16. (a) Chemical pesticides used in agricultural fields are toxic and they kill even useful organisms along with harmful ones, harm human beings and animals, pollute soil, water and crop plants. It is estimated that despite the use of chemical pesticides 30% of the agricultural produce is lost to pathogens and pests because these continue to develop resistance against various pesticides. Now, organic farmers prefer biological control of diseases and pests to the use of chemicals. Biopesticides are the biological agents that control the growth of weeds, insects and pathogens in an agricultural field. They have targeted actions and are harmless to the crop plants, other beneficial field animals and humans. In organic farming, pests and pathogens are not eradicated but kept at manageable levels by a system of

(b)

17.

(b)

18.

checks and balances as operating in ecosystem. An organic farmer holds the view that eradicating pests is undesirable because without them the beneficial predatory and parasitic organisms which depend upon them for food would also be annihilated. Bacterium as a biocontrol agent : Bacillus thuringiensis is effective against the cabbage looper. Fungi as a biocontrol agent : Trichoderma found in root ecosystem exerts biocontrol over several plant pathogens. Insect as a biocontrol agent : Lady bird beetle and dragonflies feeds on aphids and prey upon mosquitoes, respectively. (a) Small volume cultures cannot give large quantities of the product. So, the large scale production (100-1000 litres) of the products is carried out in bioreactors. Bioreactors are vessels in which raw materials are biologically converted into specific products by microbes, plants and animal cells and their enzymes. It provides optimal growth conditions such as temperature, pH, substrate, vitamins, oxygen and salts. This type of culturing method produces a larger biomass to get higher yields of desired proteins. The most commonly used bioreactor is stirred tank bioreactor. It consists of a large stainless steel vessel with a capacity of upto 500,000 dm3 around which there is a jacket of circulatory water used to control the temperature within the bioreactor. An agitator with a series of flat blades ensure thorough mixing of contents rotated with the help of a motor so that nutrients come in close with the microorganisms. It also prevents setting out of the cells at the bottom. Bioreactor also has adequate arrangement for aeration, temperature and pH control. Sparger is a porous ring at the bottom of the tank which aerates the culture. There are a number of ports through which materials can be introduced or withdrawn. A harvest line at the base of the tank extracts the culture medium and microbial products. To detect and regulate the pH and temperature changes, tank is fitted with certain probes. (a) Restriction enzymes : These enzymes belongs to the class of enzymes nucleases which breaks nucleic acids by cleaving their phosphodiester bonds. They are of two types: exonucleases and endonucleases. Exonucleases remove nucleotides from the ends of DNA. The cutting of DNA at specific locations within the DNA strand is possible with the help of ‘molecular scissors’ called restriction endonuclease. Restriction endonucleases make highly specific internal cuts in the DNA strand. These enzymes recognise palindromic sites within the DNA duplex and cut its strands by hydrolysing the phosphodiester bonds. Their single stranded free ends are called sticky ends which can be joined end to end by DNA ligases. Restriction endonucleases serve as a tool for cutting DNA molecules at predetermined sites, which is the basic requirement for gene cloning or recombinant DNA technology. For example, restriction endonuclease Eco RI MT BIOLOGY

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found in the colon bacteria Escherichia coli, recognises the base sequence GAATTC in DNA duplex and cuts its strands between G and A as shown below :

↓

5′ – G A A T T C – 3′ 3′ – C T T A A G – 5′.

↑

(b) Plasmids : They are extra-chromosomal, self-replicating, usually circular and double-stranded DNA molecules that are found naturally in many bacteria and also in some yeast. Although plasmids are usually not essential for normal cell growth and division, yet they often confer some traits on the host organism, for example, resistance to certain antibiotics or toxins that can be a selective advantage under certain conditions. The plasmid molecules may be present as single copies or in multiple copies (500-700) inside the host organism. These naturally occurring plasmids have been modified to serve as vectors in the laboratory. Plasmids are essential in biotechnological experiment as they help in transferring a segment of foreign DNA (gene of interest) into suitable host. Ti plasmid is widely used vector for cloning genes in plants. The most widely used, versatile, easily manipulated vector, pBR322 is an ideal plasmid vector. It was the first artificially cloned vector and is used widely in gene cloning experiments. The plasmids are cut and ligated with desired genes and transformed into the host cell for amplification to obtain the desired products. Some plasmids have antibiotic resistance genes which can be used as marker genes to identify recombinant plasmids from non-recombinant ones. 19. Refer to answer 118, page no. 37, MTG CBSE Champion Biology. 20. Yes, I agree that all young mothers must breast-feed their newborn babies to provide best nourishment to them. Human milk consists of fat, casein (milk protein), lactose (milk sugar), mineral salts (sodium, calcium, potassium, phosphorus, etc). and vitamins that are necessary for development of the child. Mammary glands start producing milk at the end of pregnancy. The milk produced by the mammary glands of mother during initial days after child birth, for 2 to 3 days is called colostrum. It is rich in proteins (lactalbumin and lactoprotein) and various other nutrients. It also contains certain antibodies (IgA), which provide passive immunity to the baby. This milk helps in developing resistance to disease for newborn babies. It helps the baby to fight from viruses and bacteria. It is also easily digested by the baby with no constipation or diarrhoea. 21. Refer to answer 38, page no. 62 and 42 page no. 63 MTG CBSE Champion Biology. 22. (a) VNTR stands for Variable Number of Tandem Repeats. Refer to answer 190(b), page no. 180, MTG CBSE Champion Biology. 78

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(b) Applications of DNA fingerprinting are as follows: (i) Paternity or maternity disputes can be solved by DNA fingerprinting as it can identify the real genetic mother, father and the offspring. (ii) This technique is being used to identify genes connected with hereditary diseases. (iii) It is useful in detection of crime and legal pursuits. (iv) It can identify racial groups, their origin, historical migrations and invasions. 23. (a) The major causes of air pollution are: (i) Combustion of fossil fuels and wood in automobiles, thermal plants, industries, aircrafts, etc., that gives out soot, fly ash and gases such as CO2, CO, NO2, etc. (ii) Metallurgical processing adds mineral dust, fumes rich in fluorides, metallic pollutants like lead, chromium, nickel, cadmium, etc., to the air. (iii) Burning of crop residues by farmers in agricultural lands leaves particulate matter, CO2, CO, oxides of nitrogen, methane, etc. This causes the air quality index to drop drastically. (b) Harmful effects of air pollution on plants and humans are : (i) The soot and smoke particulate matter settles on leaves and reduces the rate of photosynthesis. In humans, it penetrates deep into respiratory system and causes ailments like bronchitis, asthma, cardiovascular problems, etc. (ii) Oxides of nitrogen cause lesions, necrosis and defoliation in plants whereas in humans they cause decreased gaseous exchange in blood, eye irritation, lung edema, etc. (iii) Hydrocarbons, such as methane, lead to premature leaf fall and fruit drops in plants. In humans, it causes eye irritation, bronchial constriction, etc. Benzene and formaldehyde are carcinogenic and may cause leukemia. (c) As a captain of my school Eco-club, I would suggest the programmes to bring awareness among other students are as follows : (i) Awareness camps and seminars in the school premises with volunteers encouraging students to reduce usage of personal vehicles for pick ups and drops from home and school. Instead they should use school transports. Students can encourage their parents at home to use less of air conditioners, aerosols, etc. Also students can encourage them to use public transport i.e, buses and using CNG instead of diesel. (ii) A tree planting drive can be organised in school with all students participating and each one planting a tree sapling around the school or society to improve green cover. This would bring awareness among students as to how trees can reduce air pollution.

(iii) A poster making programme can be held in school depicting the causes, effects and solutions for air pollution. The students can use these posters in their society to make people aware. 24. (a) The organism that was used by Thomas Hunt Morgan and his colleagues for their experiments on linkage was Drosophila melanogaster. Refer to answer 80, page no. 120, MTG CBSE Champion Biology. (b) Sturtevant used the frequency of recombination between the gene pairs on the same chromosome as a measure of the distance between genes and mapped their position on the chromosome. This resulted in a chromosome map which was a linear graphic representation of the sequence and relative distances of the various genes present in that chromosome. This relative distance between genes was indicated by the percentage of their recombination or crossing over. A 100% cross over was termed as Morgan (M), 10% as deciMorgan (dM) and 1% as centiMorgan (cM) or 1 map unit. Today genetic maps are extensively used as a starting point in the sequencing of whole genomes.

OR (a) Trophic level in an ecosystem is defined as a specific place for an organism in the natural surroundings or in a community according to its feeding relationship with other organisms. It is based on the source of that organism’s nutrition or food because of which it occupies a specific position in the food chain. Standing crop is the total mass of living material at a particular trophic level at a specific time. The standing crop is measured as the mass of living organisms or biomass or the number in a unit area. The biomass of a species is expressed in terms of fresh or dry weight and the measurement of biomass in terms of dry weight is more accurate.

OR

(b) Trophic level of an organism depends upon the source of food and position in a food chain. The first trophic level is occupied by the producers which synthesise organic nutrients from inorganic raw materials with the help of solar radiations (photosynthesis) not only for themselves but also for heterotrophic organisms or consumers. They have this capacity due to the presence of chlorophyll which can convert solar energy into chemical energy, e.g., phytoplanktons, plants, trees, etc.

(a) Refer to answer 16(b), page no. 155, MTG CBSE Champion Biology.

(c) Refer to answer 29, page no. 345, MTG CBSE Champion Biology.

(b) Refer to answer 35(b), page no. 160, MTG CBSE Champion Biology.

26. (a) Flowering plants have developed many devices to discourage autogamy and geitonogamy. These are : (i) Dicliny (Unisexuality) : Flowers are unisexual so that self pollination is not possible. The plants may be monoecious (bearing both male and female flowers, e.g., maize) or dioecious (bearing male and female flowers on different plants, e.g., mulberry, papaya).Monoecious plants cannot undergo autogamy, however geitonogamy is possible in these plants whereas dioecious plants prevent both geitonogamy and autogamy. (ii) Dichogamy : Anthers and stigmas mature at different times in a bisexual flower so as to prevent self-pollination. (a) Protandry : Anthers mature earlier than stigma of the same flower. Their pollen grains become available to stigmas of the older flowers, e.g., sunflower, Salvia. (b) Protogyny : Stigmas mature earlier so that they get pollinated before the anthers of the same flower develop pollen grains, e.g., Mirabilis jalapa, Gloriosa, Plantago.

25. (a) (i),(ii) Refer to answer 28(a), page no. 323, MTG CBSE Champion Biology. (iii) Migrate : Under unfavourable conditions, some organisms migrate to more favourable areas and return when the conditions are less hostile. The movement can be in search of food, climate, etc. Many animals, specially birds, migrate during winters to more favourable areas. E.g., Arctic tern, Sea lamprey etc. Every winter the Keoladeo National Park (Bharatpur) in Rajasthan receives thousands of migratory birds which comes from Siberia and other very cold northern regions. (iv) Suspend : To tide over unfavourable conditions, some organisms suspend their metabolic activities. Bacteria, fungi and lower plants develop thick walled spores, which germinate during suitable conditions. Polar bears go into hibernation during winter season to escape cold. Some snails and fish undergo aestivation to avoid summer related problems like heat and dessication. (b) Death rate is defined as the number of deaths per 1000 individuals of a population. Since, total number of butterflies = 80 Number of butterflies that died = 8 Death rate =

8 = 0.1 butterflies per week 80

(b) Refer to answer 111, page no. 36, MTG CBSE Champion Biology. OR (a) Refer to answer 85(a), page no. 69 and 86(a), page no. 70, MTG CBSE Champion Biology. (b) Refer to answer 85(b), page no. 70, MTG CBSE Champion Biology.  MT BIOLOGY

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Rapid

- Revision

The questionnaire contains multiple choice questions from different topics covered in this issue for effective recapitulation.

1.

2.

3.

4.

5. 6.

7.

8.

9.

10.

11.

80

Select the number of plants out of the following in which haplodiplontic life cycle is present. Ulothrix, Fucus, Riccia, Selaginella, Pinus, Eucalyptus, Polysiphonia, Pteridium, Spirogyra, Ectocarpus (a) 7 (b) 6 (c) 5 (d) 4 The group of plants also known as botanical snakes is (a) bryophytes (b) pteridophytes (c) gymnosperms (d) angiosperms. Lichens are symbiotic associations between (a) algae and protists (b) fungi and bacteria (c) bacteria and protists (d) algae and fungi. A typical angiosperm embryo sac, at maturity is (a) 7-celled and 7-nucleate (b) 7-celled and 8-nucleate (c) 6-celled and 8-nucleate (d) 6-celled and 7-nucleate. Vibrio bacteria is-shaped (a) spherical (b) oval (c) comma (d) spiral. In which of the following scalariform conjugation occurs? (a) Chlamydomonas (b) Chara (c) Spirogyra (d) Chlorella A dikaryophase is present in the life cycles of (a) Agaricus and Penicillium (b) Penicillium and Pythium (c) Alternaria and Rhizopus (d) Rhizopus and Mucor. The outermost layer of a typical microsporangium is (a) tapetum (b) endothecium (c) exine (d) epidermis. Instead of a cell wall, a protein rich layer called pellicle is present in (a) Slime moulds (b) Euglena (c) Gonyaulax (d) Trypanosoma. Select the wrong statement about Deuteromycotina. (a) Conidiophores are either free or formed in some special types of fruiting bodies. (b) No specialised sex organs develop and sexual reproduction takes place by conjugation. (c) Some members show parasexuality (d) Fungi only shows asexual stages but sexual stages or perfect stages are absent. Select the wrong statement. (a) CAD is usually caused by atherosclerosis which build up plaque inside artery. (b) Now-a-days endoscopic vein harvest is used to harvest saphenous vein. MT BIOLOGY

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(c)

12. 13. 14.

15.

16.

17.

18.

19.

20.

Internal memory artery (IMA) graft is dominantly used in CABG. (d) Before bypass surgery, cardiopulmonary bypass has to be established. Eustachian valve is present at the opening of (a) coronary sinus (b) inferior vena cava (c) pulmonary aorta (d) systemic aorta. Viruses that infect plants generally have (a) single stranded DNA (b) double stranded DNA (c) single stranded RNA (d) double stranded RNA. Examples of water-pollinated plants are (a) Oxalis and Commelina (b) Viola and Vallisneria (c) Zostera and Ceratophyllum (d) Amorphophallus and Aristolochia. Which of the following medicine is given to the patient to reverse the effects of heparin? (a) Lovenox (b) Protamine (c) Arixtra (d) Both (a) and (c) Diploid parthenogenesis, that is formation of embryo directly from diploid egg without fertilisation is observed in (a) apple (b) Opuntia (c) Citrus (d) groundnut. Floridean starch as reserve food material is present in (a) Sargassum (b) Porphyra (c) Fucus (d) Ulothrix. Which of the following can be used to graft any coronary artery site? (a) Saphenous veins (b) Left internal thoracic artery (c) Radial artery (d) Ulnar artery Fusarium belongs to order (a) moniliales (b) sphaeropsidales (c) melanoconiales (d) mycelia sterilia. Select the correct statement among the following. (a) Seed plants are most successful of all the land plants because external supply of water is required for fertilisation. (b) A seed contains three generations locked one within another. (c) Fucus is also known as devil's apron. (d) Embryo stage is not present in bryophytes.

21.

22.

23.

24.

25.

26.

27.

28.

29.

30.

31.

32.

33.

34.

Which test is used to diagnose coronary artery disease (CAD)? (a) Electrocardiogram (b) Cardiac catheterisation (c) Treadmill stress test (d) All of these Which one of the following criteria was not used by Whittaker for classifying organisms in five Kingdoms? (a) Cell structure (b) Mode of nutrition (c) Presence of locomotion (d) Phylogenetic relationship Members of basidiomycetes are (a) Aspergillus, Agaricus, Neurospora (b) Trichoderma, Alternaria, Mucor (c) Ustilago, Puccinia, Agaricus (d) Puccinia, Claviceps, Albugo. In case of IMA graft, internal mammary artery anastomosed to (a) left circumflex artery (b) left anterior descending coronary artery (c) posterior descending artery (d) right marginal artery. The white kernel of a tender coconut is (a) embryo (b) nuclear endosperm (c) cellular endosperm (d) cotyledon. In angiosperms, during double fertilisation the second male gamete fuses with (a) one of the synergids (b) one of the antipodals (c) primary endosperm nucleus (d) dissolves on entering the embryo sac. True fruit among the following is (a) mango (b) cashew (c) apple (d) strawberry. Thickest muscular wall in human heart is present in (a) right auricle (b) left auricle (c) right ventricle (d) left ventricle. Which of the following can be considered as an artificial taxon? (a) Ascomycotina (b) Zygomycotina (c) Basidiomycotina (d) Deuteromycotina Algae, used in sewage oxidation tanks for disposal of sewage by decomposers are (a) Chlorella and Chlamydomonas (b) Laminaria and Macrocystis (c) Sargassum and Porphyra (d) Gracillaria and Chondrus. Polyembryony in gymnosperms can be developed due to (a) embryo development directly from diploid cells (b) embryo development from diploid egg cell (c) cleavage of growing embryo (d) sporophytic budding. The sporocarps of which of the following plants are rich source of starch and eaten for their nutritive value? (a) Adiantum (b) Marsilea (c) Lycopodium (d) Dryopteris Slowing of heart beat is called (a) tachycardia (b) bradycardia (c) cardiac arrest (d) lymphokinesis. Trimerous flowers are present in (a) rose (b) mustard (c) cotton (d) coconut.

35.

36.

37.

38.

39.

40.

41.

42.

43.

44.

45.

Coleorhiza encloses (a) radicle and root tip in a dicot embryo (b) shoot apex and a few leaf primordia in a monocot embryo (c) radicle and root tip in a monocot embryo (d) embryonal axis and a cotyledon in a monocot embryo. Heterosporous pteridophyte among the following is (a) Salvinia (b) Lycopodium (c) Dryopteris (d) Equisetum. Which one of the following is not a characteristic of wind pollinated flowers? (a) Light and non sticky pollen grains (b) Flowers produce an odour which may be pleasant or foul. (c) Well exposed stamens. (d) Single ovule in each ovary and numerous flowers packed into an inflorescence. Early blight of potato is caused by (a) Colletotrichum falcatum (b) Alternaria solani (c) Fusarium vasinfectum (d) Cercorspora personata. In normal human duration of cardiac cycle is about (a) 1.2 seconds (b) 1.0 second (c) 0.8 second (d) 0.5 second. The pollen on entering the embryo sac releases the two male gametes into the cytoplasm of (a) synergids (b) egg (c) antipodals (d) central cell. The organism that completely lacks a cell wall is (a) Mycoplasma (b) Nostoc (c) Methanococcus (d) Albugo. In a cardiac output of 5250 mL per minute, with 75 heartbeats per minute, the stroke volume is (a) 60 mL (b) 80 mL (c) 55 mL (d) 70 mL. Synnema fruiting body can be seen in members of fungi belongs to (a) ascomycetes (b) basidiomycetes (c) deuteromycetes (d) zygomycetes. The members of Kingdom Animalia store food reserves as (a) starch (b) inulin (c) glycogen (d) cellulose. Silica is present in cell walls of (a) protozoans (b) dinoflagellates (c) chrysophytes (d) euglenoids.

ANSWER 1. 6. 11. 16. 21. 26. 31. 36. 41.

(c) (c) (c) (a) (d) (c) (c) (a) (a)

2. 7. 12. 17. 22. 27. 32. 37. 42.

(b) (a) (b) (b) (c) (a) (b) (b) (d)

3. 8. 13. 18. 23. 28. 33. 38. 43.

KEY

(d) (d) (c) (a) (c) (d) (b) (b) (c)

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4. 9. 14. 19. 24. 29. 34. 39. 44.

(b) (b) (c) (a) (b) (d) (d) (c) (c)

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5. 10. 15. 20. 25. 30. 35. 40. 45.

(c) (b) (b) (b) (c) (a) (c) (a) (d)  81

Puzzle

Mania

CROSSWORD ACROSS 1. 6. 8. 11. 12. 13. 14. 15.

The process of maintaining the fertilised eggs of birds at the optimum temperature for successful development of embryos. (10) A tadpole-like larval stage of trematode worms that develops in the body of a mollusc. (8) An evolutionary process in which larval or juvenile features of an ancestral organism are displaced to the adult form of its descendants. (14) Inflammation of the gums characterised by the discharge of pus and loosening of teeth. (9) The unossified part of skull of a new born. (10) A protein found in many eukaryotic cells, that possesses ATPase activity and binds to microtubules. (6) An infectious RNA particle that causes diseases mainly in plants. (6) The highest taxonomic category, consisting of one or more kingdoms. (6)

DOWN

1

2 3 4 5

6

7

8 9 10

An alkaloid widely used in plant breeding for doubling the chromosome number and also known as mitotic poison. (10) 3. The depression on upper lip and below the nose commonly 12 found in mammals. (8) 4. A dimeric protein produced by the follicular cells of the thyroid gland and used entirely within the thyroid 14 gland. (13) 5. A structure by which two adjacent epithelial cells are attached, formed from protein plaques in the cell membranes linked by filaments. (10) 7. A lens in compound microscope that is used to collect and focus light on the specimen. (9) 9. The scientist who discovered Kappa particles in Paramecium. (9) 10. Alternate name of fermentation. (7) 2.

Readers are requested to send their responses of complete puzzle mania (crossword + riddle) to be the winner.

11

13

15

RIDDLE A

I am a red or brown respiratory pigment present in coelomic fluid in certain sea urchins.

B

I obtained proteinoid microspheres by heating a mixture of dry amino acids to 130 – 180°C and later cooling them in water.

C

I am a type of hallucinogenic drug that is derived from cactus.

D

I am a process by which the genetic material carried by an individual cell is altered by the incorporation of foreign DNA into its genome.

E

I am the smallest angiospermic parasite commonly known as “dwarf mistletoes”.

Readers can send their responses at [email protected] or post us with complete address by 10th of every month to win exciting prizes. Names of correct entries will be published in next issue.

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PROFILE

Shri Udai Singh Verma – A tale of perseverance and passion Shri Udai Singh Verma, an eminent academician, adept manager and institution builder in the field of education was born on 5th December 1936, at Shahpur, a very small village in the interiors of Haryana. Shri Verma, a veteran educationist and social reformer, has a distinguished academic career in teaching and administration spanning over 58 years. He started his professional career in 1960 as a teacher with Government school in Delhi. With his dedicated and meritorious services, he distinguished himself as an ideal teacher. All his heads whom he served held him in high esteem for his passion, perseverance and patience towards his profession. He is presently working as the Director Principal of Modern Delhi Public School, Faridabad. Shri Verma’s journey is reminiscent of no ordinary success story. It is a tale of toil and sweat, of struggle and perseverance. Coming from a humble family background, he has risen from rural hinterland to the zenith of modern education. He has worked for the cause of spreading quality education with a missionary zeal and has been on a relentless spree of setting up quality institutions, one after another. In 1968, Shri Deen Dayal, the Legendry Principal of DPS Mathura Road invited Shri Verma to be a part of his team as a guest lecturer. Shri Verma’s devotion to duty, diligence and resourcefulness earned him a high stature at DPS Mathura Road. In 1974, Shri R.S. Lugani, the Founder Principal of DPS R.K. Puram and the then Chairman, Late Dr. Prem Kirpal of the society impressed upon him to join DPS R.K. Puram as a guest lecturer and thereafter in 1982 he was inducted as the Head of the Department at DPS R.K. Puram. For giving new dimensions to education through his selfless, innovative and disciplined pursuit of excellence, Shri Verma, in 1981, was awarded with the State Award and become the first teacher from the NCR region to be selected and decorated for the National Award in 1988. During his stay at DPS R.K. Puram, he created for himself a prominent and respectable niche in the institution. Shri Verma has the credit of bringing into life the two great gems of Delhi Public School Society i.e. DPS, Vasant Vihar in 1986 and DPS Vasant Kunj in 1990, which are considered as dazzling diamonds by the members of Delhi Public School Society. In recognition to his services, Shri Verma was elevated

as the Vice Principal of DPS R.K. Puram in 1990. He extended his full cooperation and support in establishing and expanding DPS R.K. Puram, be it – academics, sports, cultural activities or infrastructure. In view of his dynamism, Shri Verma was entrusted with the challenging responsibility to establish a new venture – DPS Faridabad in 1995. DPS Faridabad started its odyssey on 10th July, 1995 with 640 students in Govt. school building at sector 21-C sans infrastructure and became a seat of excellence for the pupils of industrial city of Faridabad in a remarkably short time span. Beyond DPS under the dynamic leadership and able guidance of Shri Verma as Director Principal, Modern Delhi Public School, Faridabad, was established as a new milestone on 12th December, 2005 in the same Govt. school building at sector 21-C where DPS Faridabad was started 10 years back. Barely into its twelfth academic session, the school boasts of several milestones achieved and has become the major landmark in the educational area. Constant and concerted efforts of the students are yielding magnificent results, be it class X/XII Boards, IIT-JEE, NEET, AIIMS, KVPY, RMO, NSO, NCO, IEO, NTSE, Aryabhatta and many more. On the popular demand of the citizenries of Faridabad, Modern Delhi Public School has expanded its legacy of excellence by extending its window to Sector-89, Faridabad. The school provides the state-of-the-art infrastructure with spacious sports complex that is managed by expert sports instructors. As a result of their ceaseless efforts the students are bringing laurels in sports at state, national as well as international levels. The credentials of the school speak for it through the success of its students who passed through the portals of the school and are successfully pursuing their careers. The scholastic and co-scholastic results speak volumes about Shri Verma’s impeccable credentials as a teacher endowed with conspicuous administrative and managerial skills. Shri Verma is a living legend in the field of education, with a strong sense of vision, mission for the cause of nation and society at large. He is an architect with rich experience and expertise of setting up the educational institutions that shape the children to be academically sound, morally upright and socially well integrated citizens of whom not only the nation but humanity may be proud of.

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BIO -GRAM

Coronary Artery Bypass Grafting (CABG) C

oronary Artery Bypass Grafting (CABG) is a procedure to treat Narrowed Normal Heart artery artery severe Coronary Heart Disease (CHD) or Coronary Artery Disease (CAD)usually caused by atherosclerosis which builds up plaque on the artery walls causing the lumen of the arteries to become narrower. This slows down the flow of blood. Coronary artery disease can be diagnosed by Electrocardiogram (EKG), Treadmill stress test, Cardiac catheterisation, Plaque etc. If the blockages are significant enough, the end result will be heart attack or sudden death. CABG surgery is performed to treat narrowed and blocked arteries, allowing sufficient blood flow to deliver oxygen and nutrients to the heart muscle. CABG began in the late 1960s along two parallel paths that included bypassing coronary artery obstructions Dead heart muscle using either the Internal Mammary Artery (IMA) as the bypass conduit or reversed Saphenous Vein Graft (SVG) from the leg. The use of latter became the dominant approach as it could be used to graft any coronary artery site.

Process of CABG The majority of patients who undergo CABG surgery today receive a left IMA graft to the left anterior descending coronary artery and reversed saphenous vein grafts with proximal aortic anastomoses.

1

Different types of surgical accesses are used in CABG, but the most common name is sternotomy. In sternotomy, the cardiac surgeon makes an incision down the middle of the chest (A – B) and then saws through the breastbone (sternum).

3

A

2

B

Greater Saphenous Vein (GSV) of the lower extremity is harvested in two different ways. First, directly through multiple incisions and tunneling over the vein along the medial thigh and leg. Second, endoscopic vein harvest in which two small incisions are made one above the knee and the second on upper thigh.

After the cut, in case of off-pump surgery, the surgeon places devices to stabilise the heart. This type of surgery is called beating heart bypass grafting because the heart does not stop beating and a heart lung bypass machine (cardiac pulmonary bypass) is not used. In case of on-pump coronary artery bypass grafting, cardiac pulmonary bypass has to be established by arterial cannulation onto aortic arch and venous cannulation through the right atrial appendage into the inferior vena cava.

Off-pump coronary artery bypass graft surgery

Heart stabilising device

Vessel graft Heart

Sternal retractor

4

Coronary artery

Saphenous vein

5

In case of Internal Mammary Artery (IMA) graft, internal mammary artery is anastomosed to the Left Anterior Descending coronary artery (LAD). Once an adequate IMA with pedicle (artery with surrounding tissue) is determined, the LAD is incised and the IMA incised on an angle at an appropriate distal site. Internal mammary artery

Coronary artery

When harvesting is done, heparin is given to inhibit blood clotting. The saphenous vein is slightly tilted and anastomosed to the coronary artery with a single suture.

6

The final stage of the grafting procedure is the construction of proximal vein graf t anastomo ses. The aorta wall punch is used to create opening in aorta for anastomoses and the distal segment of the vein graft is anastomosed with aorta.

7

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After the grafting is done, the heart is restarted (in case of on-pump) or the stabilising devices are removed (in case of off-pump). Protamine is given to the patient to reverse the effects of heparin. Chest tubes are placed in the mediastinal and pleural space to drain blood from around the heart and lungs. The sternum is wired together and the incisions are sutured closed.

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Registered R.N.I. No. 71810/1999 Published on 1st of every month Postal Regd. No. DL-SW-01/4046/18-20 Lic. No. U(SW)-32/2018-2020 to post without prepayment of postage N.D.P.S.O.N.D-1 on 1-2nd same month