CBSE Class 11 Biology Important questions

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Section A

CBSE Class 11 Biology Important questions

1. Conjoint and closed vascular bundles are present in:
   1. monocot stem
   2. monocot root
   3. dicot stem
   4. dicot root

Answer: a) monocot stem

2. Which of the following is in correct hierarchical order?
   1. family, order, class, phylum
   2. species, genus, order, family
   3. class, order, family, genus
   4. phylum, family, order, class

Answer: a) family, order, class, phylum

3. Unipolar neurons are usually found in ——–      
   1. Cerebral cortex
   2. cerebellum
   3. embryonic stage
   4. Retina of eye.    

Answer: c) embryonic stage

4. Match items from column A with column B and select the correct answer.

	Column ‘A’		Column ‘B’
a	Porifera	i	Jointed appendages
b	Annelida	ii	Water vascular system
c	Aschelminthes	iii	Muscular pharynx
d	Arthropoda	iv	Canal system
e	Echinodermata	v	Metameres

1. A-II, B-III, C-V, D-IV, E-I
2. A-II, B -V, C-III, D-IV, E-I
3. A -I, B-III, C-V, D-IV, E-II
4. A- IV, B -V, C-III, D-I, E- II

Answer: d) A- IV, B -V, C-III, D-I, E- II

CBSE Class 11 Biology Important questions

5. Electro cardiograph is used to obtain an electrocardiogram (ECG), a graphical representation of the electrical activity of the heart during a cardiac cycle.  In the ECG given below, Which one represents the excitation or depolarization of the auricles?

Answer: c) ‘P’ wave

6. An increase in blood flow to the atria of the heart can cause the release of one of the following factors which can check the mechanism of renin- angiotensin.
   1. anti-diuretic hormone (ADH)
   2. atrial natriuretic factor  (ANF)
   3. renin
   4. angiotensinogen

Answer: b) atrial natriuretic factor  (ANF)

7. Given below are two characteristic features of proteins.
   5. Proteins are polypeptides and not homopolymers.
   6. The amino acids of proteins are linked by hydrogen bonds.

Which of these is /are True?

1. only ‘E’
2. only “F’
3. both ‘E’ & ‘F’
4. neither ‘E’ nor ‘F’ 

Answer: a) only ‘E’

8. Pyruvate, which is formed by glycolysis undergoes oxidative decarboxylation after it enters into
   1. Cytoplasm
   2. mitochondria
   3. mitochondrial matrix
   4. inner mitochondrial membrane

Answer: c) mitochondrial matrix

9. Study the following statements. Which among the two are correct?
   • salvinia is homosporous
   • In bryophytes, the dominant plant body is the gametophyte.
   • gametophyte is the dominant phase of Pteridophyte
   • Gymnosperms lack free-living male and female gametophytes.

The two correct statements are:

1. statements b & c
2. statements a & b
3. statements a & c
4. statements b & d

AnsWER: d) statements b & d

CBSE Class 11 Biology Important questions

10. With the help of autonomous nervous system, a special neural centre in the medulla oblongata can moderate the cardiac function. Neural signals through the sympathetic nerves (part of ANS) can ————- the rate of heart beat.
    1. decrease
    2. increase
    3. optimise
    4. neither increase nor decrease   

Answer: b) increase

11. Which one of the following hormones helps a horticulturist to produce more tomatoes without seeds.
    1. ethylene
    2. gibberellins
    3. auxins
    4. cytokinins

Answer: c) auxins

12. The excretory products of frog and tadpole respectively are 
    1. ammonia and urea
    2. urea and uric acid
    3. urea and ammonia
    4. nitrogenous substance and urea

Answer: c) urea and ammonia

13. Which of the following does not come under taxon?
    1. Species
    2. Kingdom
    3. Division
    4. Key

Answer: d) Key

14. Iodine is found in
    1. Spirogyra
    2. Laminaria
    3. Polysiphonia
    4. Chlorella

Answer: b) Laminaria

15. Select the phylum that lacks a true coelom.
    1. Platyhelminthes
    2. Annelida
    3. Echinoderms
    4. Arthropoda 

Answer: a) Platyhelminthes

CBSE Class 11 Biology Important questions

16. Label the parts of a monocot seed.

Answer:  d) A.Endosperm, B. Scutellum, C. Coleoptile, D. Plumule, E. Radicle

17. In botanical terminology, the word “phyllotaxy” specifically refers to which of the following plant features?

1. The structure and position of the ovary within a flower
2. The pattern in which leaves are arranged on a stem or branch
3. The morphological classification of a plant’s root system
4. The organization of sepals and petals in a floral whorl

Answer: b) The pattern in which leaves are arranged on a stem or branch

18. Closed vascular bundles lack

1. pith
2. xylem
3. cambium
4. xylem vessels

Answer: c) cambium

19. Tendons connect the following:

1. bone to bone
2. muscle to muscle
3. cartilage to muscle
4. bone to muscle

Answer: d) bone to muscle

CBSE Class 11 Biology Important questions

20. Middle lamella is made up of ___________.

1. calcium sulphide
2. calcium pectate
3. calcium carbonate
4. calcium chloride

Answer: b) calcium pectate

21. With reference to enzymes, which one of the following statements is true?
    1. Apoenzyme = Holoenzyme + Coenzyme
    2. Holoenzyme = Apoenzyme + Coenzyme
    3. Coenzyme = Apoenzyme + Holoenzyme
    4. Holoenzyme = Coenzyme – Apoenzyme

Answer: b) Holoenzyme = Apoenzyme + Coenzyme

22. Choose the correct sequence. A. Pachytene B. Zygotene C. Leptotene D. Diakinesis E. Diplotene
    1. C, B, A, D, E
    2. C, A, B, E, D
    3. C, B, A, E, D
    4. D, B, C, E, A

Answer: c) C,B,A,E,D

23. Mobilization of stored food in germinating seeds is triggered by

1. auxins
2. cytokinins
3. gibberellins
4. ethylene

Answer: c) gibberellins

CBSE Class 11 Biology Important questions

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Assertion and reason

1. Both A and R are factually correct, and R provides the precise logical explanation for A.
2. A is true and R is also true, but R does not logically justify or clarify A.
3. Assertion A holds true; however, the reason given in R is factually incorrect.
4. Assertion A is not valid, but the statement in Reason R is accurate.

1. Assertion (A): Trachea will not collapse even if there is no air in it.

Reason (R): Trachea consists of cartilaginous rings.

Answer: A) Both A and R are factually correct, and R provides the precise logical explanation for A.

2. Assertion (A): During photosynthesis, starch is synthesised 1 from sugar using the products of light reactions (ATP and NADPH).

Reason (R): synthesis of starch depends on light.

Answer: C) Assertion A holds true; however, the reason given in R is factually incorrect.

3. Assertion (A): During muscle contraction, shortening of the sarcomere occurs when the ‘z’ line attached to the actins are pushed outward.

Reason (R): Myosin head binds to the active site on actin to form cross bridge which pulls the actin filaments towards the centre of ‘A’ band.

Answer: D) Assertion A is not valid, but the statement in Reason R is accurate.

4. Assertion (A): neurotransmitters are the chemicals involved in the transmission of impulses at the synapses.

Reason (R): impulse transmission across an electrical synapse is faster than that across chemical synapse.

Answer: B) A is true and R is also true, but R does not logically justify or clarify A.

5. Assertion (A): Haemoglobin is an oxygen carrier.

Reason (R): Oxygen binds to NH2 of haemoglobin.

Answer: C) Assertion A holds true; however, the reason given in R is factually incorrect.

6. Assertion (A): Thrombocytes play an important role in blood coagulation.

Reason (R): These cells are formed by the fragmentation of megakaryocytes.

Answer: B) A is true and R is also true, but R does not logically justify or clarify A.

7. Assertion (A): The epithelial cells of PCT have a brush border.

Reason (R): Luminal surfaces of the epithelial cells are provided with microvilli.

Answer: A) Both A and R are factually correct, and R provides the precise logical explanation for A.

8. Assertion (A): Rheumatoid arthritis is a viral disease.

Reason (R): This condition is often called ‘wear and tear’ arthritis.

Answer: D) Assertion A is not valid, but the statement in Reason R is accurate.

9. Assertion (A): Pancreas is a heterocrine gland. 

Reason (R): Pancreas consists of exocrine as well as endocrine tissues.

Answer: A) Both A and R are factually correct, and R provides the precise logical explanation for A.

CBSE Class 11 Biology Important questions

10. Assertion (A): Haemoglobin is a quaternary protein. 

Reason (R): It consists of 4 amino acid units

Answer: C) Assertion A holds true; however, the reason given in R is factually incorrect.

11. Assertion (A): Action spectrum of photosynthesis compares well with the absorption spectrum of chlorophyll.

Reason (R): Chlorophyll is the primary pigment that absorbs light and converts it into chemical energy.

Answer: B) A is true and R is also true, but R does not logically justify or clarify A.

12. Assertion (A): The urinary bladder has a well-developed, 3 layered detrusor muscle in its wall.

Reason (R): The bladder contracts rhythmically to expel urine during micturition.

Answer: A. Both A and R are factually correct, and R provides the precise logical explanation for A.

13. Assertion (A): Specialization of cells is advantageous for the organisms.

Reason (R): This process enhances an organism’s functional efficiency.

 Answer:  A) Both A and R are factually correct, and R provides the precise logical explanation for A.

14. Assertion (A): Cell growth is a continuous process in terms of cytoplasmic increase.

Reason (R): DNA is synthesized during two distinct phases of the cell cycle.

 Answer:  C) Assertion A holds true; however, the reason given in R is factually incorrect.

15. Assertion (A): Stomata are absent in submerged hydrophytes.

Reason (R): Submerged plants respire through air chambers.

Answer:  B) A is true and R is also true, but R does not logically justify or clarify A.

16. Assertion (A): Both ammonia and urea are excreted by earthworms.

Reason (R): Excretion in earthworm depends on the environment.

Answer: A) Both A and R are factually correct, and R provides the precise logical explanation for A.

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Section B

CBSE Class 11 Biology Important questions

1. How do the classes Phycomycetes and Ascomycetes of Kingdom Fungi differ from each other in term of:

i. Mode of nutrition

ii. Nature of mycelium

Answer:

Classes of fungi	Mode of nutrition	Nature of myceilium
Phycomycetes	Obligate parasites on plants	Aseptate and coenocytic.
Ascomycetes	Coprophilous (growing on dung)	Branched and septate.

2. Mention any two types of leucoplasts with its function.

Answer: amyloplasts – store carbohydrates, elaioplasts – store oils and fats, aleuroplasts store proteins

3. What is the building block of nucleic acids? What are its components?

Answer: Nucleotide, heterocyclic compound/ purines, pyrimidines, monosaccharide/ ribose or deoxy ribose, phosphoric acid or phosphate

4. The membrane of a resting nerve fibre is said to be in a polarised state? Why?

Answer: During resting, the axonal membrane is more permeable to potassium ions (K+) and impermeable to sodium ions Na+ and negatively charged proteins present in axoplasm, The active transports of ions by the sodium – potassium pump transports 3 Na+ ions outwards for 2 K+ ions into the cell, As a result, the outer surface of the axonal membrane possesses a positive charge, inner surface becomes negatively charged and therefore is polarised.

CBSE Class 11 Biology Important questions

5. • a) To which part of human neural system the afferent and efferent nerve fibres belong?
   • b) How do they differ from each other?

Answer:

a) Peripheral nervous system,

b) afferent nerve fibres transmit impulses from tissues/organs to the CNS, Efferent nerve fibres transmits regulatory impulses from the CNS to the concerned peripheral tissue/organs.

6. Write the difference between blood and lymph.

Answer:

	Blood	Lymph
1.	Red due to haemoglobin.	Colourless as it has no haemoglobin.
2.	Glucose concentration is low in blood	Glucose concentration is high
3	Contains plasma, RBC, WBC and blood platelets	Contains plasma and very low number of WBC
4	It transports materials from one organ to another.	It transports materials from tissue cells into the blood.
5.	Clotting of blood is a fast process.	Clotting of lymph is a comparatively slow process.
6	Flow of blood is fast	Flow of lymph is slow.

7. Write the difference between RBC and WBC.

Answer:

	RBC	WBC
1.	RBC is red due to Haemoglobin.	No haemoglobin so colourless.
2.	RBC of mammals is enucleated.	WBC is nucleated.
3.	Its life span is 100 -120 days.	Short lived
4.	It carries respiratory gases.	It is responsible for immunity

8. Why is it not advised to sleep in closed rooms warmed with burning of coals continuously?   

answer: It is not advised to sleep in a closed room warmed continuously with burning coal because person sleeping in room gets CO poisoning. CO combines with haemoglobin more readily than O2 forming Carboxyhaemoglobin. This reduces the amount of Free Hb available to carry O2. Thus the tissue is starved of O2.                 

CBSE Class 11 Biology Important questions

9. What are the effects of hypothyroidism (observed during the pregnancy) On the development and maturation of growing baby?         

Answer: Hypothyroidism during pregnancy causes defective development and maturation of the growing baby leading to stunted growth (cretinism), mental retardation, low intelligence, abnormal skin and deaf mutism.        

10. The following events occur during the various phases of cell cycle. Match each event with its corresponding phase.

1. Disintegration of nuclear membrane:   _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
2. Replication of DNA: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Answer:        (a) Prophase              (b)S-phase.

11. Draw a well labelled diagram of nerve cell.

Answer:

12. Draw the well labelled diagram of chloroplast.

Answer:

CBSE Class 11 Biology Important questions

13. In the graphical representation of pulmonary volumes and capacities given below, what does X and Y represent. Also give their values.

Answer:

X – Inspiratory Capacity

Inspiratory Capacity (IC) = Tidal Volume (TV) +Inspiratory Reserve Volume (IRV)

IC = 500 + 2500-3100

IC = 3000 – 3600 ml

Y – Vital Capacity

Vital Capacity is the sum of Tidal Volume, Expiratory Reserve Volume, and Inspiratory Reserve Volume (VC = TV + ERV + IRV).

VC = 500 + 1200 + 2500 – 3100

VC = 4200 – 4800 ml

14. Name the stages of cell division at which these events occur-

(a) Disappearance of nuclear membrane

(b) Crossing over between non-sister chromatids

(c) Terminalisation of Chiasmata

(d) Homologous pair of chromosomes separate and move to opposite poles of the spindle

Answer:

a. Prophase

b. Pachytene of Prophase I

c. Diakinesis of Prophase I

d. Anaphase I

15. Why is ABA is also known as ‘stress hormone’? Mention any two functions of this hormone.

Answer: Abscisic acid is a stress hormone that triggers adaptive plant responses and enhances tolerance to environmental stresses.

It induces the closure of the stomata during water stress / promotes seed dormancy and ensures seed germination during favourable conditions / helps seeds withstand desiccation / helps in inducing dormancy in plants at the end of the growing season / promotes abscission of leaves, fruits, and flowers.

16. Which one of the plant growth regulators would you use if you are asked to ?

(a) Induce rooting in a twig

(b) Quickly ripen a fruit

(c) Increase yield of sugarcane

(d) Bolt a rosette plant

Answer:

a. Auxin

b. Ethylene

c. Gibberellin

d. Gibberellin

CBSE Class 11 Biology Important questions

(a) What is meant by reabsorption in urine formation?

(b) Name the two modes of reabsorption

Answer:

(a) Glomerular filtrate contains substances the body needs like essential ions, glucose, amino acids, and smaller proteins in addition to wastes. This needed substances and some water are reabsorbed into adjacent blood capillaries.

(b) Active reabsorption of Glucose, amino acids, Na+ etc.

      Passive reabsorption of water

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Section C

1. Compare chordates and non chordates. Write any three points.

Answer:

1	Notochord present	Notochord absent
2	Central nervous system is dorsal, hollow and single	Central nervous system is ventral, solid and double
3	Pharynx perforated by gill slits	Gill slits are absent
4	Heart is ventral	Heart is dorsal (if present
5	A post anal part (tail) is present	Post anal tail is absent

1. Cotton and coriander plants have the ability to produce different shapes of leaves. What is it called?
2. Name the hormones that are responsible for the following functions.

1. Thinning of cotton,
2. Helps seeds to withstand desiccation and other factors unfavorable for growth.
3. To produce chloroplasts in leaves
4. Used to prepare weed free lawns by gardeners.

Answer:

a) plasticity

b) i) ethylene  ii) abscisic acid   iii) cytokinins   iv) auxins

1. What is glycolysis?
2. Where does it occur? What is the key product of glycolysis?
3. Mention the ways by which the product is handled by yeast, bacteria and muscles of human.

Answer:

a) break down of glucose to Pyruvic acid.

b) Cytoplasm.

c) Yeast – produce CO2 and ethanol from Pyruvic acid /alcoholic fermentation, bacteria –  produce lactic acid  from Pyruvic acid /lactic acid fermentation, human muscle cells – Pyruvic acid is reduced to lactic acid.

4. Lysosomes, vacuoles and mitochondria are endomembrane structures. Yet they differ in their function. Comment.

Answer:

Lysosomes: hydrolytic enzymes (hydrolases – lipases, proteases, carbohydrases which are capable of digesting carbohydrates, proteins, lipids and nucleic acids.

Vacuoles: facilitates transport of ions and other materials against concentration gradient (in plants) , for osmoregulation and excretion (ex., in amoeba).

Mitochondria generate ATP, the cell’s main energy currency.

5. List out any three modifications that are observed in birds that help them fly.

Answer:

1. presence of feathers
2. modification of forelimbs into wings
3. endoskeleton ossified and hollow long bones with air cavities.

6. The following parts were observed by a student of Biology.

Identify and illustrate the following structures in a labeled diagram: epidermis, collenchymatous hypodermis, parenchymatous cortex, endodermis containing starch grains, pericycle located internal to the endodermis, and pith. (6 labelling)

Answer:

7. Photorespiration is the process where the enzyme RuBisCO oxygenates RuBP with the release of carbon dioxide. It is also known as a wasteful process. But C4 plants escape from this phenomenon. How?

Answer: CO₂ concentration is increased at RuBisCO level to enable it to act as RuBP carboxylase enzyme , this occurs when the C4 acid/ oxaloacetic acid from the Mesophyll is broken down in the bundle sheath cells to release CO₂ , results in increasing the intracellular concentration  of CO₂ which favours the RuBisCO to function as a carboxylase enzyme but not as an oxygenase enzyme that favours photorespiration.        

8. Write the difference between C₃ and C₄ plants.

Answer:

	C3 Plant	C4 Plant
1	Do not have dimorphic chloroplast	Have dimorphic chloroplast
2	Photorespiration occurs in them	No photorespiration
3	First CO2 acceptor is Ribulose1,5-Biphosphate a 5 Carbon compound	First CO2 acceptor is PEP a 3 carbon compound.
4	First stable product formed is a 3 carbon compound PGA	First stable product formed is a 4 carbon compound OAA.

9. Write the difference between cyclic and non- cyclic photophosphorylation.

Ans:

	Cyclic-photo-phosphorylation	Non cyclic photo-phosphorylation
1	Only PS-I is involved	Both PS-I and PS-II are involved.
2	Only ATP is synthesized.	Both ATP and NADH2 are synthesized
3	No photolysis of water so no release of Oxygen	Photolysis of water and release of oxygen occurs.
4	Source of electron is Chlorophyll-a	Source of electron is  water

1. Write the energy balance sheet of Aerobic reaction?
2. What is the net gain of ATP during aerobic respiration?
3. What is R.Q. Using rice and potato as respiratory substrates.

Answer:     

(a)  Glycolysis  -2ATP+ 2NADH2 = 8 ATP released

 Oxydative carboxylation- 2NADH2= 2X3ATP=6ATP released

               Krebs cycle \rightarrow 6NADH2 = 18 ATP

Each FADH₂ yields 2 ATP, so 2 FADH₂ generate 4 ATP.

                       2GTP = 2 ATP

                       Total is 24

 Gross ATP release in Aerobic respiration is 38 ATP but 2 ATP are used up in pumping 2 NADH2 from cytoplasm to mitochondria so net gain of ATP is 36 ATP

 (b) net gain 36 ATP. Because 2 ATP are used up in pumping 2 NADH2 from cytoplasm to mitochondria.

 (c) R.Q. is 1 because it is rich in carbohydrate.

1. Why is photorespiration absent in C₄ plants?
2. Explain the dual role of RUBISCO.

Answer:

1. Photorespiration does not occur in C₄ plants because photorespiration takes place when RUBISCO enzyme show oxygenase activity at high temperature and high concentration of oxygen these condition is present in mesophyll cells but there is no RUBISCO enzyme And RUBISCO ENZYME is available in bundle sheath cells of C₄  plants where O₂ is not released and temperature is also not high.
2. RUBISCO shows dual role-
   • At high temperature and high concentration of O₂ it acts as oxygenase and causes photorespiration whereas at low temperature and low O₂ concentration it shows carboxylase activity and fixes CO₂

12. Study the diagram given below and answer the question that follows-

Answer:

1. Metaphase
2. Chromosomes aligned at equator to form metaphase plate.
3. Anaphase.

13. What are the physiological effects of cytokinins?

Answer: Physiological Effects of cytokinin-

1.It induces cell division in combination with Auxin.

2.Promote the growth of lateral buds by breaking apical dominance

3.Cytokinin in combination with Auxin control morphogenesis in plants.

4.It delays senescence of leaves and other parts.

14.  Which phytohormone is known as stress hormone and why?

Answer: ABA is called stress hormone because it stimulates the closure of stomata and increases the tolerance of plants to various kinds of stresses. ABA plays an important role in seed development, maturation and dormancy. ABA promotes seed dormancy, enabling survival under dry or otherwise unfavorable conditions.

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Section D

1. Diabetes mellitus is а major cause of blindness, kidney failure, heart аttаck, stroke and lower limb аmputаtion. WHO predicts diabetes will rank as the 7th leading cause of death by 2030. Diabetes mellitus is mainly of two types: Type 1 and Type 2. Type 1 Diabetes mellitus (previously known as insulin dependent, juvenile or childhood-onset) It leads to lack of Insulin and increased glucose in blood and urine. It requires daily аdministrаtion of insulin for survival. Its symptoms are frequent urination (polyuriа), increased thirst (polydipsiа), increased hunger (polyphаgiа), weight loss, vision changes and fatigue. These symptoms may occur suddenly. Formerly known as adult-onset diabetes, Type 2 is characterized by the body’s ineffective insulin use and accounts for most global diabetes cases. 90% cases of diabetes are type 2 diabetes, whereas only 10% cases may be of type 1 diabetes. Symptoms of type 2 diabetes are often less marked. Аs а result, the disease may be diagnosed several years after onset, once complications have аlreаdy arisen.

Answer:

a)  ‘β’ cells of ‘Islets of Langerhans’ of pancreas , peptide hormone

b)  Glucagon secreted by α-cells of Islets of Langerhans’ of pancreas acts on the liver cells (hepatocytes) and stimulates glycogenolysis (break down of glycogen to glucose) resulting in an increased blood sugar.

c)  Glucagon

d) Over weight, inactivity/ sedentary life style, smoking etc., (any two)

                                     Or

d) diabetic mellitus, by observing the loss of glucose through urine and formation of  ketone bodies.

2. Bryophytes are small, non-vascular plants, such as mosses, liverworts and hornworts. They play a vital role in regulating ecosystems because they provide an important buffer system for other plants, which live alongside and benefit from the water and nutrients that bryophytes collect.  Some bryophyte species are amongst the first to colonise open ground. Bryophytes are also very good indicators of habitat quality as many plant species in this group are sensitive to levels of moisture in the atmosphere, which are lower in disturbed habitats because there is less shade. Bryophytes do not have seeds or flowers. Instead they reproduce via spores. Bryophytes comprise approximately 20,000 species.

Answer the following:

1. Explain why bryophytes are considered amphibians of the plant kingdom.
2. Name the male gamete of bryophytes.

Answer:

a) they live in soil but are dependent on water for sexual reproduction.

b)  Antherozoids

c)   Moss -Funaria, C- capsule, A- leaves , B – rhizoids

OR

c)  A liverwort – Marchantia- male thallus, a- antheridiophore, b – Gemma cup   c- Rhizoids

3. In fermentation, say by yeast, the incomplete oxidation of glucose is achieved under anaerobic conditions by sets of reactions where pyruvic acid is converted to CO2 and ethanol. These reactions are catalyzed by pyruvic acid decarboxylase and alcohol dehydrogenase. In organisms such as certain bacteria, pyruvic acid is converted into lactic acid. In animal muscle cells during intense exercise, insufficient oxygen leads to the reduction of pyruvic acid into lactic acid via lactate dehydrogenase. The reducing agent is NADH+H+ which is reoxidised to NAD+ in both the processes. Both lactic acid and alcohol fermentation release less than 7% of glucose’s energy, with limited ATP capture. These pathways also produce harmful byproducts; for example, yeast dies when alcohol concentration reaches approximately 13%.

1. Under _ _ _ _ _ _ _ _ _ _condition incomplete oxidation of respiratory substrate takes place.

1. Aerobic
2. Anaerobic
3. Aerobic and anaerobic
4. None of the above

2. In fermentation process,

1. pyruvic acid is converted to Oxygen and ethanol
2. pyruvic acid is converted to Carbon dioxide and ethylene
3. pyruvic acid is converted to Carbon dioxide and ethanol
4. pyruvic acid is converted to Carbon dioxide and ethephon

3. Name the enzyme which facilitates the reactions where pyruvic acid is converted to Carbon dioxide and ethanol.
4. Identify the oxygen-dependent process that fully oxidizes organic compounds.

Answer:

1. b
2. c
3. Pyruvic acid decarboxylase and Alcohol dehydrogenase catalyse the reactions where pyruvic acid is converted to CO2 and ethanol.
4. Aerobic respiration is the process that leads to a complete oxidation of organic substances in the presence of oxygen and releases carbon dioxide, water and a large amount  of energy present in the organic substance.

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Section E

1. Ammonia is the simplest form of nitrogenous waste which is formed by deamination of amino acids. It is highly soluble in water hence is generally excreted across the body surface through diffusion. Terrestrial adaptation made the production of less toxic forms of nitrogenous waste like urea and uric acid. Ammonia is converted into urea in the liver and released into the blood. It than filtered and excreted out by kidneys.

1. Which is the least toxic form of excretory product?
2. What do we call the organism which excrete the ammonia as nitrogenous waste product?
3. Name two animals which excrete uric acid?
4. Arrange the three nitrogenous waste-product in decreasing order of their toxicity?
5. Some animals can excrete ammonia as waste product where as others do not. Why?

Answer:

1. Uric acid
2. Ammoniotelic
3. Birds and reptiles
4. Ammonia>Urea>Uric acid
5. Ammonia is most toxic nitrogenous product so it needs to be excreted in dilute form (dissolved in water) which causes tremendous loss of water which terrestrial animals can-not afford but aquatic animals can afford the loss of water so the excrete ammonia as waste product.

1. Compare the following:

1. Resting potential and action potential
2. myelinated and non-myelinated axon.

2. Mention the part of neuron which receives the stimuli.

Answer:

1. (i) Resting potential- axoplasm is negative and exterior is positive. Membrane is more permeable to potassium than to sodium ions.

Action potential- axoplasm is positive and exterior is negative.

ii) Membrane is more permeable to sodium than to potassium ions. (ii) myelinated- nerve fibre covered by myelin sheath Non-myelinated- nerve fibre not covered by myelin sheath.

2. Dendrites

3. The cells of the upper layer of the epidermis, cells of the lining  5 of the gut, and blood cells are being constantly replaced in animals by mitotic division. In plants, mitosis occurs in meristematic tissues like apical and lateral cambium, enabling lifelong growth. Identify the mitotic stage where each specified event occurs in plant meristems.

1. Spindle fibres attach to kinetochores of chromosomes.
2. Formation of mitotic apparatus. Explain how?
3. Nuclear envelope develops around the chromosome clusters at each pole forming two daughter nuclei.Centromeres split and chromatids separate.
4. How does cytokinesis differ in plant and animal cells?

Answer:

1. metaphase of meiosis
2. Prophase of mitosis, chromosomes which had undergone duplication during interphase, begins to move towards opposite poles of the cell. Each centrosome radiates out microtubules called asters. The mitotic apparatus is formed by two asters and spindle fibers.
3. Telophase
4. Anaphase
5. In animal cells, cytokinesis occurs by the formation of furrow in the plasma membrane, deepens and joins at the centre. In plants, cell plate is formed at the centre of the

4. Gametogenesis is the process of production of gametes. Males undergo spermatogenesis; females undergo oogenesis. The cells in the gonads undergo meiosis and forms gametes such as sperms and ova in higher animals.

1. What is the count of chromosomes of sperms at the end of meiosis?
2. Distinguish Anaphase I from Anaphase II of meiosis.
3. Name the stage and process that are involved in bringing genetic variation during meiosis.

Answer:

1. Haploid/ 23 chromosomes
2. Anaphase I: the homologous chromosomes separate, while sister chromatids remain associated at their centromeres. Anaphase II: Begins with simultaneous splitting of the centromeres of each chromosome (which was holding the sister chromatids together), allowing them to move toward opposite poles of the cell by shortening of microtubules attached to kinetochores.
3. The pachytene sub-stage of meiotic prophase I is when crossing over occurs.

5. List the salient features of the Calvin cycle. Why are the plants having this cycle are called C3 plants.

Answer:

1. It was studied by Calvin in a unicellular green alga Chlorella by using C14O2 with the help of autoradiography
2. Three types of reactions namely carboxylation, reduction and regeneration occur
3. There is utilization of 18 ATP and 12 NADPH molecules for 6 CO2 molecules
4. The fixation of 6 molecules of CO2 and 6 turns of the cycle are needed for the production of one molecule of glucose

6. Name the parts of the human forebrain indicating their respective functions.

Answer:

Part of forebrain	Functions
Olfactory region	Smell
Cerebrum	Thinking, intelligence, memory ability to learn from experience etc Heat, cold and pain
Diencephalon	Heat, cold and pain
Hypothalamus	Control centre of autonomic nervous system, Regulate body temp. appetite, emotions, metabolism etc

1. Where are ribsosomes present in a prokaryotic cell? What is their function? Differentiate between RER and SER .
2. What are plasmodesmata? What is their function?

Answer:

a) Ribosomes are present on Endoplasmic Reticulum

Function of ribosomes: Synthesis Protein

RER- Endoplasmic Reticulum that contains Ribosomes

SER- Endoplasmic Reticulum that does not contain Ribosomes

b) Plasmodesmata  – cytoplasmic bridges that transverse the primary cell wall and middle lamella and connect the adjacent cell.

Function: They form transport channels between adjacent cells

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