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Grade XIBiology

Exam Preparation Booklet

Chapter Wise - Important Questions and Solutions

Questions

The Living World

Q1. What are the characteristics of living organisms? (1 mark)

Q2. Name a plant that closes its leaves when touched. This feature is an example of which

characteristic of living things? (2 marks)

Biological Classification

Q1. Explain the dikaryophase of a fungus. (2 marks)

Q2. What are the various modes of reproduction in fungi? Mention various steps of sexual

reproduction in them. (4 marks)

Plant Kingdom

Q1. (a) Write two important features of pteridophytes that distinguishes them from bryophytes.

(b) Name the alga from which agar is obtained.

(2+1 marks)

Animal Kingdom

Q1. What are the basis on which animals are classified? (2 marks)

Q2. ‘All vertebrates are chordates but not all chordates are vertebrates.’ Justify this statement.

(2 marks) Q3. Give a schematic representation of the classification of Subphylum Vertebrata.

(3 marks)

Morphology of Flowering Plants

Q1. What is meant by placentation? What type of placentation is present in the gynoecium of the following plants? (a) China rose (b) Dianthus (c) Argemone

(2 marks)

Q2. Describe any two stem modifications with examples.

(2 marks) Q3. Describe the main regions of the root tip with the help of diagram.

(3 marks)

Anatomy of Flowering Plants

Q1. Name and briefly describe the four kinds of elements that constitute xylem. (4 marks)

Q2. Describe the different types of meristematic tissues present in plants.

(4 marks)

Structural Organisation in Animals

Q1. Name the three types of muscle fibres present in the bodies of animals. Give a brief description of each of the fibres.

(3 marks) Q2. Make a branch diagram to show the various categories and subcategories of connective

tissue. (3 marks)

Cell: The Unit of Life

Q1. Classify chromosomes on the basis of the position of centrioles. (5 marks)

Q2. Name the different components of the endomembrane system. Give the functions of two

types of endoplasmic reticulum. (4 marks)

Biomolecules

Q1. Explain the effect of temperature and pH on enzyme activity through appropriate graphs.

(2 marks)

Q2. Describe four levels of structure in proteins.

(4 marks)

Cell Cycle and Cell Division

Q1. State the differences between mitosis and meiosis. (5 marks)

Q2. Describe various stages of prophase I during meiotic division with suitable diagrams.

(5 marks)

Q3. How is cytokinesis in a plant cell different from that in an animal cell?

(2 marks)

Transport in Plants

Q1. Give two pathways by which water moves deeper into the root layer in plants. (3 marks)

Q2. Give a diagrammatic representation of how the translocation of sugars occurs from source to sink.

(3 marks) Q3. (a) Describe the structure of stomata with the help of well labelled diagram.

(b) Explain how is the opening and closing of stomata regulated. (3+2 marks)

Mineral nutrition

Q1. Explain how essential elements can be classified on the basis of their functions. (4 marks)

Q2. Explain how Rhizobium establishes a symbiotic association with the roots of leguminous

plants and helps them in obtaining nitrogen. (5 marks)

Photosynthesis in Higher Plants

Q1. (a) Which photosystem is associated with the splitting of water during the process of photosynthesis?

(b) Represent the ‘Z’ scheme of light reaction diagrammatically.

(1+2 marks) Q2. Describe the three main stages of Calvin pathway.

(5 marks) Q3. Compare the effect of CO2 concentration on the rate of photosynthesis in C3 and C4

plants. (2 marks)

Respiration in Plants

Q1. Why is the process of ATP synthesis during respiration known as oxidative phosphorylation? Briefly explain the process with the help of a suitable diagram.

(3 marks)

Q2. Represent schematically the pathway of cellular respiration common to all organisms,

aerobic and anaerobic. (5 marks)

Q3. Briefly explain the fate of pyruvate after it enters mitochondria.

(5 marks)

Plant Growth and Development

Q1. Which plant growth regulator can be used for inducing the following physiological effects? (i) Delay leaf senescence (ii) Induce growth in axillary buds (iii) Prevent shedding of mature leaves (iv) Promote flowering in short day plants (v) Inhibit auxin synthesis and transport

(5 marks)

Q2. What is photoperiodism in plants? What will happen when a long day plant with the

critical day length of 14 hours is exposed to light for more than 15 hours? (2 marks)

Digestion and Absorption

Q1. Mention the triggers required for the activation of following enzymes. (a) Salivary amylase (b) Pepsin (c) Trypsin (d) Bile juice

(4 marks) Q2. What is succus entericus? Give its composition.

(2 marks)

Breathing and Exchange of Gases

Q1. What is oxygen-dissociation curve? Name the factors favourable for the association of oxygen with haemoglobin in the alveoli.

(3 marks) Q2. How is ‘respiration’ different from ‘breathing’? Explain the processes of ‘aerobic’

respiration and ‘anaerobic’ respiration. (4 marks)

Q3. How is carbon dioxide transported throughout our body?

(5 marks)

Body Fluids and Circulation

Q1. (i) What do you understand by ECG? Give the graphic record of a normal person.

(ii) What changes would be observed in graphic record if a person is suffering from arteriosclerosis?

(2+2 marks) Q2. Give a schematic representation of how blood circulates in the human body with the help

of a flowchart showing the organs through which the blood passes during the course of circulation.

(3 marks) Q3. Describe the mechanism of blood clotting.

(3 marks)

Excretory Products and their elimination

Q1. (a) Draw a well-labelled structure of nephron.

(b) Give an account on the permeability of ascending and descending limbs of loop of

Henle in a nephron. (2+1 marks)

Q2. Explain the process of urine formation along with a diagram showing reabsorption and

secretion of substances in nephron. (5 marks)

Locomotion and Movement

Q1. Explain the sliding filament theory of muscle contraction along with diagram. (5 marks)

Neural Control and Coordination

Q1. How does a reflex pathway function? (3 marks)

Q2. Explain the process of generation of nerve impulse.

(5 marks) Q3. Describe the mechanism of hearing.

(5 marks)

Chemical Coordination

Q1. Name the different regions of the pituitary gland. List the hormones released by each region along with the regions.

(5 marks)

Solutions

The Living World Ans 1. All living organisms :-

(i) Need food (ii) Grow (iii) Respire (iv) Respond to stimuli (v) Reproduce (vi) Excrete (vii) Show movement.

Ans 2. Mimosa pudica (touch-me-not) is an example of a plant that closes its leaves when

touched. It is an example of response to stimulus, which is a characteristic of living things.


Ans 1. A fungi are heterotrophic and absorb soluble organic matter from dead substrates.

The dikaryophase of a fungus is the phase of formation of a dikaryon. In fungi such as ascomycetes and basidiomycetes, the fusion of two haploid cells results in a dikaryotic stage (n + n), where two nuclei are present per cell. This is known as dikaryon. Later, the nuclei fuse to form a diploid cell.

Ans 2. The means of reproduction in fungi are as follows:

1. Vegetative means: These include fragmentation, fission and budding. 2. Asexual reproduction: It involves the formation of spores like zoospores or

sporangiospores 3. Sexual reproduction: It involves the formation of oospores, ascospores and

basidiospores. These spores are produced inside the fruiting bodies. The steps of sexual cycle are as follows: • Fusion of protoplasm between two motile or non-motile gametes, i.e.,

plasmogamy. • Fusion of two nuclei, i.e., karyogamy.

Meiosis in zygote results in the formation of haploid spores.

Plant Kingdom Ans 1. (a) The important features of pteridophytes are as follows.

(i) They have specialized conducting tissues for the conduction of water and food while in bryophytes such types of conducting tissues are absent.

(ii) The dominant phase of the life cycle of pteridophyte is sporophyte that is differentiated into root, stem, and leaves while in the life cycle of bryophytes, gametophyte is the dominant phase.

(b) Agar is used as a culture medium for raising microbes. It is also used in jams and jellies. It is obtained from algae Gelidium and Gracilaria.

Animal Kingdom

Ans 1. Animals are basically classified on the basis of the following criteria in order of their

increasing complexities. • Arrangement of cells (levels of organisation). • Body symmetry, nature of coelom. • Patterns of digestive, circulatory, or reproductive systems. • Presence or absence of notochord.

Ans 2. The members of Vertebrata possess notochord during embryonic development. Thus,

all vertebrates are chordates. However, the notochord gets replaced by a cartilaginous or bony vertebral column in the adult. Thus, all chordates are not vertebrates.

Ans 3.

Morphology Of Flowering Plants Ans 1. Placentation is defined as the arrangement of ovules within the ovary.

Types of placentation (a) China rose − Axile placentation (b) Dianthus − Free central placentation (c) Argemone − Parietal placentation

Ans 2. Two stem modifications are:- 1. Storage of food as in underground stems of potato, ginger and turmeric. 2. Tendrils which are slender axillary buds are spirally coiled to help the plant

climb as in pumpkin. Ans 3. The regions of root tip are as follows:

• Region of meristematic activity: It lies above the root cap. It consists of small, thin-walled dividing cells with dense protoplasm.

• Region of elongation: It consists of enlarged cells that help in root growth. • Region of maturation: It bears root hair which consist of mature and

differentiated cells.

Anatomy of Flowering Plants Ans 1. The four kinds of elements that constitute xylem are as follows:

• Tracheids: These are elongated tube-like cells with tapering ends. These cells have thick and lignified walls. These cells are dead and lack protoplasm.

• Vessels: Cells called vessel members constitute these long cylindrical structures. The vessel members have lignified walls and a large central cavity. They are interconnected through perforations in their walls.

• Xylem fibres: They have thickened walls and a central lumen. These may be septate or aseptate.

• Xylem parenchyma: These cells and living and thin-walled and their cell walls are made of cellulose.

Ans 13. Meristem is of three types. These are represented in the given figure.

• Apical meristem: The cells of this meristem are present at the tips of

stems, roots and branches. They are responsible for the axial growth in a plant. Some cells of the apical meristem form axillary buds that are capable of giving rise to new leaves or flowers.

• Intercalary meristem: The cells of this meristem are present at the base of

internodes and are responsible for the growth of the internodal region. The apical meristem and the intercalary meristem constitute the primary meristem since they are responsible for the development of the primary plant body.

• Lateral meristem: The cells of this meristem are present on the lateral side of

stems and roots. Lateral meristem is responsible for the radial growth of plants. Fascicular vascular cambium, interfascicular cambium and cork cambium are the examples of lateral meristem.

Structural Organisation in Animals Ans 1. The three types of muscle fibres present in animals are as follows:

• Skeletal muscle fibre: They are attached to the skeletal bones and are voluntary in nature. Skeletal muscle fibres are striated and are bundled together in a parallel manner by a sheath of tough connective tissues.

• Smooth muscle fibres: They are present in the walls of internal organs such as blood vessels, stomach, etc., and are involuntary. They are fusiform i.e., tapered at both ends and non- striated. They are held together by cell junctions in a sheath of connective tissues.

• Cardiac muscle fibres: They are present only in the heart. They are contractile in nature and are involuntary. Plasma membranes of cardiac cells are fused together by cell junctions. Hence, the cells stick together. Communication junctions present as intercalated discs facilitate the contraction of cardiac cells as a unit.

Ans 2.

Cell: The Unit of Life Ans 1. On the basis of the position of centrioles, chromosomes are of four types. These are:

• Metacentric: The centromere located in the middle, forming two equal arms of the chromosome.

• Submetacentric: The centromere is located slightly away from the middle, thereby resulting in one arm being longer than the other.

• Acrocentric: The centromere is located close to the end, thereby resulting in one arm being extremely longer than the other.

• Telocentric: The centromere is located at the terminal point.

Ans 2. The endomembrane system includes endoplasmic reticulum (ER), Golgi complex,

lysosomes and vacuole.

Two kinds of endoplasmic reticula and their functions are as follows: • Rough endoplasmic reticulum (RER): They have ribosomes embedded on them

that are the main site for protein synthesis in cell. They help in the translation of mRNA to protein.

• Smooth endoplasmic reticulum (SER): They are the major site for lipid synthesis.

Biomolecules

Ans 1. The enzyme activity is maximum at optimum temperature and pH. The enzyme activity decreases at values both below and above this optimum point. Effect of enzyme on change in pH

Effect of enzyme on change in temperature

Ans 2. The structure in proteins can be divided into four levels.

(i) Primary structure: The linear sequence of amino acids in a polypeptide chain is known as primary structure of a protein. In this, the first amino acid is called N − terminal amino acid while the last is known as C − terminal amino acid.

(ii) Secondary structure: When two or more polypeptide chains are held together by

hydrogen bonds, it is known as secondary structure. The secondary structure of proteins is of two types - α-helix and β-pleated structure.

(iii) Tertiary structure: When polypeptide chain becomes further coiled by the formation of ionic bond, hydrogen bond, or disulphide bond, it is known as tertiary structure. The examples include enzymes such as amylase and pepsin.

(iv) Quaternary structure: When a protein has several polypeptide chains, it forms a highly complex structure called quaternary structure. The examples include the structure of haemoglobin, which consists of four subunits.


Ans 1.

S. No. Mitosis Meiosis

1 It involves single division,

resulting in the formation of two diploid daughter cells.

It involves two successive divisions, namely meiosis I and II, resulting in the formation of

four haploid daughter cells.

2

It is also known as equational division as the daughter cell has

the same number of chromosomes as the parent cell.

Meiosis I is known as reductional division because here the chromosome number is

reduced to half while meiosis II is known as equational division where the sister chromatids separate while the chromosome number remains

the same.

3

The prophase stage is short and does not comprise of synapsis,

crossing over, and the formation of chiasmata.

The prophase I stage is very long. It comprises of five stages. In the zygotene stage of meiosis

I, the pairing of homologous chromosomes takes place. During the pachytene stage,

crossing over occurs while in the diplotene stage, chiasmata formation occurs.

4 It plays a significant role in cell growth, repair, and healing of

wounds.

It brings about variation and maintains constant chromosome number from one generation to

another.

5 It mainly takes place in the somatic cells. It mainly takes place in the reproductive cells.

Ans 2. Meiosis I is a reductional division, where the chromosome number in the daughter

cells get reduced to half of the parental chromosomal number. The various stages of prophase I are as follows. (i) Leptotene: Leptotene is the first stage of prophase I of meiosis. During this

stage, condensation of chromatin fibres takes place that results in the formation of distinct chromosomes.

(ii) Zygotene: Zygotene is the second stage of prophase I, where the pairing of

chromosomes, called synapsis, takes place. Therefore, chromosomes appear in the form of bivalents. They are now known as homologous chromosomes. Synapsis is also accompanied by the formation of synaptonemal complex.

(iii) Pachytene: Pachytene is the third stage of prophase I. During this stage, the

bivalents become a tetrad, where each chromosome has four chromatids. The process of crossing over, which involves exchange of genetic material between the pair of non-sister chromatids of homologous chromosomes, takes place during this stage. The process is catalyzed by enzyme recombinase that causes the breaking and attachment of fragments from two non-sister chromatids. This results in the recombination of the genes.

(iv) Diplotene: Diplotene is the fourth stage of prophase I that is recognized by the dissolution of synaptonemal complex. The two homologous chromosomes (bivalents) separate from each other except at chiasmata.

(v) Diakinesis: Diakinesis is the last stage of prophase I marked by the

terminalization of chiasmata. During this stage, the chromosomes get fully condensed. The formation of spindle fibres starts during this stage so as to prepare homologous chromosomes for separation. The nucleolus and nuclear envelope completely disappear at the end of this stage.

Ans 3. In an animal cell, cytokinesis is initiated by the appearance of a furrow in the plasma membrane, which deepens and finally leads to the division of the cell into two daughter cells. In plant cells, the cell wall formation starts from the middle and proceeds outwards. This is initiated by the formation of a cell plate that is similar to the middle lamella.

Transport in Plants

Ans 1. The two pathways of water movement into the root layers are as follows.

(1) Apoplast pathway: It involves the movement of water through the cell wall and intercellular spaces, which is continuous except at the endodermis in the root. This pathway does not involve the crossing of the membrane and the movement of water is through mass flow.

(2) Symplast pathway: It involves the movement of water through the cytoplasm and the plasmodesmata of root cells. The water crosses the membrane and moves down through the potential gradient. The water movement occurs by the cytoplasmic stream.

Ans 2.

Ans 3. (a) Stomata are tiny pores present mainly on the surface of leaves. They are also present on the surface of young stems and roots. Stomata consist of a stomatal

opening or stoma, which is surrounded by two distinct epidermal cells known as guard cells. The opposing inner walls of the guard cells are thick and inelastic. The remaining walls are thin and elastic. The microfibrils are oriented radially in the walls of guard cells that aid in the opening of stomata.

(b) The opening and closing of stomata is caused by the change in turgidity of the

guard cells. The inner walls of the guard cells are thick and elastic. When turgidity increases within two guard cells, the outer walls bulge and the stomata open.

The opening is also aided due to the orientation of microfibril in the guard cells. These microfibrils are oriented radially rather than longitudinally making it easier for the stomata to open. When turgidity decreases within the guard cells, the inner walls regain their original shape and the stomata closes.

Mineral nutrition

Ans 1. On the basis of their functions, essential elements can be classified into four main

categories. 1. Essential as components of biomolecules: Some elements such as carbon,

hydrogen, oxygen and nitrogen form the components of biomolecules such as carbohydrates, proteins, fats, nucleic acids etc. Hence, they constitute the structural elements of cells.

2. Essential as components of energy-related compounds of the cell: Some elements are components of energy-related compounds in the cell. For example, magnesium is a component of chlorophyll and phosphorus is a component of ATP.

3. Essential for the activation/inhibition of enzymes: Some elements are essential for the activation or deactivation of enzymes. For example, magnesium is essential for the activation of photosynthetic enzymes such as RuBisCo and PEP carboxylase.

4. Essential for the maintenance of osmotic potential of the cell: Some elements such as sodium, potassium and chlorine are essential for maintaining the osmotic potential of a cell.

Ans 2. Rhizobium is a symbiotic nitrogen fixing bacteria that resides in the root nodules of

leguminous plants. • Nodules are the small outgrowths on roots. They involve the interaction

between the roots of the host plant and the bacteria that multiply and colonise the roots, thereby attaching themselves to the root hair cells and the epidermal cells.

• Root hair curls and bacteria infest there, and finally, reach the cortex, where nodule formation begins.

• An infection thread carries the bacteria to the cortex. In the next step, the bacteria get released from the thread and invade the cortex cells.

• Specialised nitrogen-fixing cells differentiate and form the nodules. These nodules establish a direct vascular connection with the host for exchange of nutrients.

• Nodules also carry the enzyme nitrogenase and the pink-coloured leg haemoglobin.

• Nitrogenase is a Mo−Fe protein that catalyses the conversion of N2 into ammonia. It is strictly anaerobic.

• Leg haemoglobin acts as an oxygen scavenger during the course of the process, which protects the oxygen-sensitive enzyme nitrogenase.

Photosynthesis in Higher Plants Ans 1. (a) Photosystem II is associated with the splitting of water. The electron produced

by this process is utilized in photosystem as

(b)

Ans 2. (i) Carboxylation: In this stage carboxylation of ribulose-1,5-bisphosphate (RuBP)

by atmospheric CO2 in the presence of enzyme RuBisCo takes place. This reaction generates two molecules of 3-PGA.

(ii) Reduction: In this stage series of reaction occur that lead to the formation of glucose. For this 2 molecules of ATP for phosphorylation, two of NADPH for reduction per CO2 molecule fixed are utilised.

(iii) Regeneration: For the continution of the cycle, regeneration of CO2 acceptor molecule RuBP is essential.It requires one ATP for phosphorylation to form RuBP.

Ans 30. CO2 concentration affects the rate of photosynthesis in both C3 and C4 plants. Though

both C3 and C4 plants show increase in rate of photosynthesis at high light intensity when CO2 concentration increases, the saturation point for C3 is obtained at higher concentrations as compared to C4. Therefore, C3 plants are more sensitive to changes in CO2 concentration as compared to C4 plants.


Ans 1. The production of proton gradient required for the production of ATP is provided by

the energy of oxidation−reduction reaction. Therefore, the process of ATP synthesis during respiration is called oxidative phosphorylation.

Complex V or ATP synthase is involved in this process. It has two major components. • F0 particle: It is an integral membrane protein that forms a channel through

which H+ cross the inner membrane. • F1 particle: The passage of H+ induces conformational changes in F1, which

forms a site for synthesis of ATP from ADP; for each ATP produced, 2H+ pass through F0 down the electrochemical proton gradient.

Ans 2. Glycolysis is a respiratory pathway that is common to all living organisms.

The two ATP-utilising steps of glycolysis are as follows: Glucose → Glucose − 6 − phosphate (1 ATP utilised) Fructose − 6 − phosphate → Fructose 1, 6 − bisphosphate (1 ATP utilised)

Ans 3. The product of glycolysis i.e., pyruvate, on entering the mitochondrial matrix, undergoes oxidative decarboxylation, thereby producing acetyl CoA that enters Krebs cycle.

Krebs cycle (Tricarboxylic acid cycle)

The basic steps in Krebs cycle are as follows: • In the beginning of the cycle, the acetyl group condenses with oxaloacetic acid

and water to yield citric acid. This reaction is catalysed by the enzyme citrate synthase. The citrate isomerises into isocitrate.

• Two successive decarboxylation steps follow, leading to the formation of α ketoglutaric acid, followed by succinyl CoA.

• This is followed by the conversion of succinyl CoA into succinic acid (substrate level phosphorylation). In a coupled reaction, GTP is converted into GDP, simultaneously synthesising ATP from ADP.

• The conversion of one molecule of pyruvate into acetyl CoA yields 1 molecule of CO2 and 1 NADH.

• One Krebs cycle yields 2 CO2 + 3 NADH + 1 FADH2 + 1 ATP. The overall equation of Krebs cycle can be given as follows:


Ans 34. (i) Cytokinin

(ii) Cytokinin (iii) Auxin (iv) Abscisic acid (v) Ethylene

Ans 35. Photoperiodism is defined as the physiological response of the plants to the relative

length of day and night. On the basis of photoperiodic responses, plants can be divided into three types. • Short-day plant • Long-day plant • Day-neutral plant When a long-day plant with a critical day length of 14 hours is exposed to light for more than 15 hours, it will show flowering and fruiting.


Ans 1. (a) Salivary amylase: It is secreted by salivary gland and is activated when

carbohydrate-rich food enters the buccal cavity. It can work only when pH of buccal cavity is around 6.8.

(b) Pepsin: It is released in inactive form i.e. pepsinogen from the peptic cells of gastric gland. The pro-enzyme pepsinogen, when exposed to HCl, gets converted into active pepsin and carries out digestion of proteins.

(c) Trypsin: It is the active form of the zymogen, trypsinogen present in the pancreatic juice. Inactive trypsinogen is converted into trypsin by enterokinase enzyme secreted by intestinal mucosa. Trypsin carries out further digestion of partially digested proteins.

(d) Bile juice: When fat-rich food enters the duodenum, bile is released from gall bladder. The contraction of gall bladder for the release of bile is stimulated by cholecystokinin.

Ans 2. Succus entericus is the intestinal juice secreted from the cells present in the intestinal

mucosal epithelium. It consists of secretions from the goblet cells and brush border

columnar cells. It contains mucus and a variety of enzymes such as disaccharidase, dipeptidase, nucleosidase, and lipase.


Ans 1. The oxygen-dissociation curve is a sigmoid curve plotted between the percentage

saturation of oxy-haemoglobin and partial pressure of oxygen. It helps in understanding the effects of factors such as hydrogen ion concentration, temperature, carbon dioxide, etc. on the formation of oxy-haemoglobin.

The factors favourable for the association of oxygen with haemoglobin in the alveoli are as follows. 1. Low pCO2 2. Low H+ concentration 3. Low temperature 4. High pO2

Ans 2. Breathing is the process by which oxygen is taken in (inhalation) and carbon dioxide

is released out (exhalation). Respiration involves the oxidation of the food we eat to release energy. Carbon dioxide produced as a result of this is released out during exhalation. Aerobic respiration: During aerobic respiration, the oxidation of food takes place in the presence of oxygen. Aerobic respiration can be summarised by the given equation:

Anaerobic respiration: During anaerobic respiration, food is broken down in the absence of oxygen. It is also known as fermentation and is more common in microorganisms such as yeast. Sometimes pyruvate gets converted into lactic acid in muscles by the process of anaerobic respiration.

Ans 3. Carbon dioxide, like oxygen, is circulated all over our body through blood. There are three different ways by which carbon dioxide gets transported throughout our body. They are as follows: • In combination with the amine group of haemoglobin protein (20−25%) • In the form of bicarbonate ions (70%) • In dissolved form through plasma (7%) The exchange of gases between blood and body tissues depends on their respective partial pressure. They flow from their high partial pressure to a low partial pressure by detaching themselves from the haemoglobin molecule. Transport of carbon dioxide through haemoglobin:- • Carbon dioxide gets attached to the amino group of the polypeptide chain of

haemoglobin to form carbamino-haemoglobin. This is a reversible reaction. • The formation of carbamino-haemoglobin depends upon pO2 and pCO2. In

tissues where the partial pressure of CO2 is high as compared to that of O2, CO2 combines with the free amine group of haemoglobin to form carbamino-haemoglobin.

• In alveoli, where the partial pressure of CO2 is lower than that of O2, CO2 gets dissociated from carbamino-haemoglobin. Thus, CO2 binds itself with the haemoglobin in the tissues and dissociates itself in the alveoli, where it is released.

Transport of carbon dioxide in the form of bicarbonate ions:- • Most of the carbon dioxide is transported in the form of bicarbonate ions with

the help of an enzyme called carbonic anhydrase that is present in RBCs and plasma.

• At the tissue site where partial pressure of CO2 is high due to catabolism, CO2 diffuses into blood (RBCs and plasma) and combines with water to form carbonic acid. This reaction is catalysed by carbonic anhydrase in both the directions. H2O + CO2⇔ H2CO3 The carbonic acid, so formed, dissociates into hydrogen ions and bicarbonate ions. This reaction is also catalysed by carbonic anhydrase in both the directions. H2CO3⇔ H+ + HCO−3


Ans 1. (i) ECG stands for Electrocardiogram. The recording of electrical potential

gradient generated by the spread of cardiac impulse is known as electrocardiogram. The ECG of a normal person can be represented as

(ii) During arteriosclerotic heart disease, the PQ interval lengthens. This is due to

inflammation of atria and AV node. As a result, the QR wave becomes enlarged.

The ST interval is the representation of time between the end of the spread of impulse through ventricles and its repolarisation. As a result, the ST segment would be elevated.

Ans 2.

Ans 3. Clotting is required for preventing excessive loss of blood from the body.

Blood clot is formed by the threads of the protein fibrin that traps the formed elements. Mechanism of coagulation is a cascade of reactions involving several clotting factors. It is initiated by the enzyme thrombokinase. The enzyme thrombokinase converts prothrombin into thrombin, which in turn, leads to the activation of other proteins involved in clotting. Calcium ions also play an important role in blood clotting mechanism. Prothrombin (inactive form) thrombin (active form)

Fibrinogen (inactive form) fibrin (active form)


Ans 1. (a)

(b) The ascending limb of Henle’s loop is impermeable to water. However, it is permeable to many other electrolytes. On the other hand, the descending limb of Henle’s loop is permeable to water, but impermeable to electrolytes.

Ans 2. Urine formation occurs in kidneys. It involves the following steps:

• Glomerular filtration: It is the first step of urine formation. It involves the filtration of blood by glomerulus. About 1100-1200 ml of blood is filtered every minute. The filtration occurs through three layers, the endothelium of glomerular blood vessels, epithelium of Bowman’s capsule, and the basement membrane between endothelial and epithelial layers. All the constituents of plasma pass through the slit pores except proteins. Hence, the process is called ultra filtration.

• Tubular reabsorption: 99% of the formed filtrate is reabsorbed by the renal tubules. Reabsorption occurs in different segments of nephron by active or passive mechanisms.

• Tubular secretion: The tubular cells secrete substance such as H+, K+ and ammonia for maintaining ionic and acid-base balance of body fluids.

Locomotion and Movement Ans 1. According to the sliding filament theory, the contraction of muscle fibres occurs by

the sliding of thin filaments over the thick filaments to reduce the length of sarcomere. It can be explained as follows: 1. The actin filaments move deeper into A-band towards the centre of sarcomere. 2. The heads of myosin filaments function as hooks and by attaching to the

F-actin, they form cross bridges. 3. As a result, the relative configuration changes and pulls the actin filament into

the A-band. 4. The Z-lines are drawn closer. 5. The length of A-band remains the same while the length of I-band decreases

resulting in shortening of sarcomere.

6. When the actin filaments slide out from the A-band, the I-band lengthens resulting in the lengthening of sarcomere.

Neural Control and Coordination Ans 1. Reflex action refers to the entire process of involuntary response to a peripheral

nervous stimulation. A reflex arc comprises of an afferent neuron that receives signals from a sensory organ and transmits the impulse to the CNS through dorsal nerve root. The signal, so carried, is then processed by the CNS (spinal cord in case of reflex action) and a response is generated. The efferent neuron of the reflex pathway carries signals from the CNS to the effector to produce a response.

Ans 2. Neurons are excitable cells because their membranes are polarised. Neural

membranes are polarised because selectively permeable ion channels are present in them. When a neuron is at the state of rest, axonal membrane is more permeable to K+ and nearly impermeable to Na+. It is also impermeable to negatively charged proteins present inside axoplasm. Thus, it does not let them go out. As a result, the axoplasm has higher concentration of K+ and negatively charged proteins and lower concentration of Na+.This creates a concentration gradient which is maintained by the sodium−potassium pump,which pumps 3 Na+ out and 2 K+ in. Hence, the outer surface of the membrane possesses positive charge and the inner surface possesses negative charge. This potential difference is called resting potential. When stimulus is applied at a particular site (say site A), it becomes freely permeable to the influx of Na+. Hence, polarity at that site is reversed. The membrane is now depolarised and potential difference across the site is called action potential (nerve impulse).

Ans 3. The ear consists of three sections with different functions. The outer ear consists of

the pinna, which receives sound waves in the ear tube (external auditory meatus); these sound waves results in the vibration of the tympanic membrane (ear drum). In the middle ear, the vibrations of the tympanic membrane are transmitted across the membranous oval window by the movement of three ear ossicles (malleus, incus and stapes). A lever system between these bones and the relative area of contact of the malleus with the tympanic membrane and the stapes with the oval window amplify the movement of the tympanic membrane. The inner ear is a complex system of canals and cavities within the skull bone. The vibrations are passed through the oval window onto the fluid of the cochlea, where they generate waves in the lymph. The waves in the lymph induce a ripple in the basilar membrane. These movements of the basilar membrane bend the hair cells, thus pressing them against the tectorial membrane. The auditory receptors found here help in the conduction of a message through afferent neurons to the auditory cortex of the brain for interpretation.

Chemical Coordination Ans 1. Pituitary gland is anatomically divided into:

1. Adenohypophysis: It consists of two portions − pars distalis and pars intermedia. It is also known as anterior pituitary.

2. Neurohypophysis: It is also known as pars nervosa or posterior pituitary. The hormones released by different regions of pituitary gland are: • Pars distalis: It produces growth hormone, prolactin, thyroid stimulating

hormone, adrenocorticotropic hormone, luteinizing hormone and follicle stimulating hormone.

• Pars intermedia: It produces melanocyte stimulating hormone. • Pars nervosa: It produces oxytocin and vasopressin.

Questions

The Living World

Q1. What are the characteristics of living organisms? (1 mark)

Q2. Name a plant that closes its leaves when touched. This feature is an example of which

characteristic of living things? (2 marks)


Q1. Explain the dikaryophase of a fungus. (2 marks)

Q2. What are the various modes of reproduction in fungi? Mention various steps of sexual

reproduction in them. (4 marks)

Plant Kingdom

Q1. (a) Write two important features of pteridophytes that distinguishes them from bryophytes.

(b) Name the alga from which agar is obtained.

(2+1 marks)

Animal Kingdom

Q1. What are the basis on which animals are classified? (2 marks)

Q2. ‘All vertebrates are chordates but not all chordates are vertebrates.’ Justify this statement.

(2 marks) Q3. Give a schematic representation of the classification of Subphylum Vertebrata.

(3 marks)

Morphology of Flowering Plants

Q1. What is meant by placentation? What type of placentation is present in the gynoecium of the following plants? (a) China rose (b) Dianthus (c) Argemone

(2 marks)

Q2. Describe any two stem modifications with examples.

(2 marks) Q3. Describe the main regions of the root tip with the help of diagram.

(3 marks)

Anatomy of Flowering Plants

Q1. Name and briefly describe the four kinds of elements that constitute xylem. (4 marks)

Q2. Describe the different types of meristematic tissues present in plants.

(4 marks)

Structural Organisation in Animals

Q1. Name the three types of muscle fibres present in the bodies of animals. Give a brief description of each of the fibres.

(3 marks) Q2. Make a branch diagram to show the various categories and subcategories of connective

tissue. (3 marks)

Cell: The Unit of Life

Q1. Classify chromosomes on the basis of the position of centrioles. (5 marks)

Q2. Name the different components of the endomembrane system. Give the functions of two

types of endoplasmic reticulum. (4 marks)

Biomolecules

Q1. Explain the effect of temperature and pH on enzyme activity through appropriate graphs.

(2 marks)

Q2. Describe four levels of structure in proteins.

(4 marks)


Q1. State the differences between mitosis and meiosis. (5 marks)

Q2. Describe various stages of prophase I during meiotic division with suitable diagrams.

(5 marks)

Q3. How is cytokinesis in a plant cell different from that in an animal cell?

(2 marks)

Transport in Plants

Q1. Give two pathways by which water moves deeper into the root layer in plants. (3 marks)

Q2. Give a diagrammatic representation of how the translocation of sugars occurs from source to sink.

(3 marks) Q3. (a) Describe the structure of stomata with the help of well labelled diagram.

(b) Explain how is the opening and closing of stomata regulated. (3+2 marks)

Mineral nutrition

Q1. Explain how essential elements can be classified on the basis of their functions. (4 marks)

Q2. Explain how Rhizobium establishes a symbiotic association with the roots of leguminous

plants and helps them in obtaining nitrogen. (5 marks)

Photosynthesis in Higher Plants

Q1. (a) Which photosystem is associated with the splitting of water during the process of photosynthesis?

(b) Represent the ‘Z’ scheme of light reaction diagrammatically.

(1+2 marks) Q2. Describe the three main stages of Calvin pathway.

(5 marks) Q3. Compare the effect of CO2 concentration on the rate of photosynthesis in C3 and C4

plants. (2 marks)


Q1. Why is the process of ATP synthesis during respiration known as oxidative phosphorylation? Briefly explain the process with the help of a suitable diagram.

(3 marks)

Q2. Represent schematically the pathway of cellular respiration common to all organisms,

aerobic and anaerobic. (5 marks)

Q3. Briefly explain the fate of pyruvate after it enters mitochondria.

(5 marks)


Q1. Which plant growth regulator can be used for inducing the following physiological effects? (i) Delay leaf senescence (ii) Induce growth in axillary buds (iii) Prevent shedding of mature leaves (iv) Promote flowering in short day plants (v) Inhibit auxin synthesis and transport

(5 marks)

Q2. What is photoperiodism in plants? What will happen when a long day plant with the

critical day length of 14 hours is exposed to light for more than 15 hours? (2 marks)


Q1. Mention the triggers required for the activation of following enzymes. (a) Salivary amylase (b) Pepsin (c) Trypsin (d) Bile juice

(4 marks) Q2. What is succus entericus? Give its composition.

(2 marks)


Q1. What is oxygen-dissociation curve? Name the factors favourable for the association of oxygen with haemoglobin in the alveoli.

(3 marks) Q2. How is ‘respiration’ different from ‘breathing’? Explain the processes of ‘aerobic’

respiration and ‘anaerobic’ respiration. (4 marks)

Q3. How is carbon dioxide transported throughout our body?

(5 marks)


Q1. (i) What do you understand by ECG? Give the graphic record of a normal person.

(ii) What changes would be observed in graphic record if a person is suffering from arteriosclerosis?

(2+2 marks) Q2. Give a schematic representation of how blood circulates in the human body with the help

of a flowchart showing the organs through which the blood passes during the course of circulation.

(3 marks) Q3. Describe the mechanism of blood clotting.

(3 marks)


Q1. (a) Draw a well-labelled structure of nephron.

(b) Give an account on the permeability of ascending and descending limbs of loop of

Henle in a nephron. (2+1 marks)

Q2. Explain the process of urine formation along with a diagram showing reabsorption and

secretion of substances in nephron. (5 marks)

Locomotion and Movement

Q1. Explain the sliding filament theory of muscle contraction along with diagram. (5 marks)

Neural Control and Coordination

Q1. How does a reflex pathway function? (3 marks)

Q2. Explain the process of generation of nerve impulse.

(5 marks) Q3. Describe the mechanism of hearing.

(5 marks)

Chemical Coordination

Q1. Name the different regions of the pituitary gland. List the hormones released by each region along with the regions.

(5 marks)

Solutions

The Living World Ans 1. All living organisms :-

(i) Need food (ii) Grow (iii) Respire (iv) Respond to stimuli (v) Reproduce (vi) Excrete (vii) Show movement.

Ans 2. Mimosa pudica (touch-me-not) is an example of a plant that closes its leaves when

touched. It is an example of response to stimulus, which is a characteristic of living things.


Ans 1. A fungi are heterotrophic and absorb soluble organic matter from dead substrates.

The dikaryophase of a fungus is the phase of formation of a dikaryon. In fungi such as ascomycetes and basidiomycetes, the fusion of two haploid cells results in a dikaryotic stage (n + n), where two nuclei are present per cell. This is known as dikaryon. Later, the nuclei fuse to form a diploid cell.

Ans 2. The means of reproduction in fungi are as follows:

1. Vegetative means: These include fragmentation, fission and budding. 2. Asexual reproduction: It involves the formation of spores like zoospores or

sporangiospores 3. Sexual reproduction: It involves the formation of oospores, ascospores and

basidiospores. These spores are produced inside the fruiting bodies. The steps of sexual cycle are as follows: • Fusion of protoplasm between two motile or non-motile gametes, i.e.,

plasmogamy. • Fusion of two nuclei, i.e., karyogamy.

Meiosis in zygote results in the formation of haploid spores.

Plant Kingdom Ans 1. (a) The important features of pteridophytes are as follows.

(i) They have specialized conducting tissues for the conduction of water and food while in bryophytes such types of conducting tissues are absent.

(ii) The dominant phase of the life cycle of pteridophyte is sporophyte that is differentiated into root, stem, and leaves while in the life cycle of bryophytes, gametophyte is the dominant phase.

(b) Agar is used as a culture medium for raising microbes. It is also used in jams and jellies. It is obtained from algae Gelidium and Gracilaria.

Animal Kingdom

Ans 1. Animals are basically classified on the basis of the following criteria in order of their

increasing complexities. • Arrangement of cells (levels of organisation). • Body symmetry, nature of coelom. • Patterns of digestive, circulatory, or reproductive systems. • Presence or absence of notochord.

Ans 2. The members of Vertebrata possess notochord during embryonic development. Thus,

all vertebrates are chordates. However, the notochord gets replaced by a cartilaginous or bony vertebral column in the adult. Thus, all chordates are not vertebrates.

Ans 3.

Morphology Of Flowering Plants Ans 1. Placentation is defined as the arrangement of ovules within the ovary.

Types of placentation (a) China rose − Axile placentation (b) Dianthus − Free central placentation (c) Argemone − Parietal placentation

Ans 2. Two stem modifications are:- 1. Storage of food as in underground stems of potato, ginger and turmeric. 2. Tendrils which are slender axillary buds are spirally coiled to help the plant

climb as in pumpkin. Ans 3. The regions of root tip are as follows:

• Region of meristematic activity: It lies above the root cap. It consists of small, thin-walled dividing cells with dense protoplasm.

• Region of elongation: It consists of enlarged cells that help in root growth. • Region of maturation: It bears root hair which consist of mature and

differentiated cells.

Anatomy of Flowering Plants Ans 1. The four kinds of elements that constitute xylem are as follows:

• Tracheids: These are elongated tube-like cells with tapering ends. These cells have thick and lignified walls. These cells are dead and lack protoplasm.

• Vessels: Cells called vessel members constitute these long cylindrical structures. The vessel members have lignified walls and a large central cavity. They are interconnected through perforations in their walls.

• Xylem fibres: They have thickened walls and a central lumen. These may be septate or aseptate.

• Xylem parenchyma: These cells and living and thin-walled and their cell walls are made of cellulose.

Ans 2. Meristem is of three types. These are represented in the given figure.

• Apical meristem: The cells of this meristem are present at the tips of

stems, roots and branches. They are responsible for the axial growth in a plant. Some cells of the apical meristem form axillary buds that are capable of giving rise to new leaves or flowers.

• Intercalary meristem: The cells of this meristem are present at the base of

internodes and are responsible for the growth of the internodal region. The apical meristem and the intercalary meristem constitute the primary meristem since they are responsible for the development of the primary plant body.

• Lateral meristem: The cells of this meristem are present on the lateral side of

stems and roots. Lateral meristem is responsible for the radial growth of plants. Fascicular vascular cambium, interfascicular cambium and cork cambium are the examples of lateral meristem.