NIOS Class 12 BIOLOGY Oct 2024 ESS Set A Solved

NIOS Biology Paper 2024 October Set A

SECTION–A  (1 MARK) 

1. The bacteria that help in the fixation of atmospheric nitrogen:

(A) Rhizobium 

(B) Streptomyces

(C) Salmonella 

(D) Lactobacillus

2. Which one of the following represent the gametophyte of fern?

(A) Indusium 

(B) Sorus

(C) Prothallus 

(D) Frond

3. Which one of the following is the living part of xylem?

(A) Tracheid

(B) Vessel

(C) Xylem Fibre 

(D) Xylem Parenchyma

4. Name the cells that are seen in the lymph nodes and attack bacteria

(A) Lymphocytes 

(B) Monocytes

(C) Granulocytes 

(D) Erythrocytes

5. The blood protein that provides factors for clotting is

(A) Albumin 

(B) Fibrinogen

(C) Globulin

(D) Thrombin

6. Identify “A” in the given diagram

(A) Cerebellum 

(B) Cerebrum

(C) Medulla oblongata 

(D) Pons

7. Which one of the following is not produced due to undersecretion of thyroxine?

(A) Goitre 

(B) Cretinism

(C) Myxoedema 

(D) Rickets

8. Which one of the following adaptations is seen in plants to promote self-pollination?

(A) Cleistogamy 

(B) Dichogamy 

(C) Unisexuality 

(D) Self-sterility

9. Corpus luteum produces

(A) Oestrogen 

(B) Androgens 

(C) Progesterone 

(D) Prolactin

10. In the following flow chart A, B, C, and D represent

(A) A-AA+ZW, B-A+W, C-AA+ZW, D-AA+ZW

(B) A-AA+ZZ, B-A+W, C-AA+ZW, D-AA+ZW

(C) A-AA+ZW, B-A+Z, C-AA+ZW, D-AA+ZW

(D) A-AA+ZW, B-A+W, C-AA+ZW, D-AA+ZZ

11. The formation of RNA from DNA is known as

(A) Translation 

(B) Transcription

(C) Transformation 

(D) Transduction

12. In the given food chain identify the trophic level of frog.

(A) First trophic level 

(B) Second trophic level

(C) Third trophic level 

(D) Tertiary trophic level

13. The biological community in an area or ecosystem is a complex network of interactions. Interactions may be of various types. In commensalism type

(A) One species gets benefitted, and the other species is neither harmed nor benefitted.

(B) One species is inhibited and the other is unaffected.

(C) One species is benefitted, and the other is harmed and inhibited.

(D) Both the species are benefitted.

14. Biotechnology helps in synthesizing enzymes from cloned genes. Your friend wants to

manufacture meat tenderisers. Which enzyme would you recommend to him?

(A) Lipases 

(B) Proteases 

(C) Amylases 

(D) Glucoisomerases

15. Which one of the following is not the step of microinjection process in biotechnology?

(A) Collection and in vitro maturation of oocytes

(B) In vitro fertilization with male semen

(C) Microinjection of “input DNA” into male pronuclei

(D) Infection of pre-implantation embryos with retroviruses carrying foreign DNA

16. Identify the immunoglobulin found in highest concentration in our body

(A) IgD 

(B) IgA 

(C) IgG 

(D) IgM

SECTION – B (2 Marks)

17. Name the following

(i) Excretory organs of earthworm – __________

(ii) Naked seeds are the characteristic feature of this group of plants – __________

Ans: 

• (i) Nephridia.
• (ii) Gymnosperms

18. Match Column I with the functions given in Column II.

Column-I	Column-II
(i) Pneumatophores	(a) Roots with chlorophyll and manufacture food
(ii) Haustoria	(b) Roots developing from nodes and provide anchorage
	(c) Roots which grow vertically up in the air and help in respiration
	(d) Roots which penetrate the host plant and suck food from host

Ans: 

• (i) Pneumatophores- (c) Roots which grow vertically up in the air and help in respiration
• (ii) Haustoria- (d) Roots which penetrate the host plant and suck food from the host

19. Observe the diagrams given below and assign the correct name from the list supplied. (Attempt any two parts from A-D). (Rhizome, Tuber, Corm, Bulb)

(Rhizome, Tuber, Corm, Bulb)

Ans: 

• Rhizome – A
• Tuber – D
• Corm – B
• Bulb – C

20. Photosynthesis occurs in green parts of the plants, mostly the leaves which have chloroplasts. The thylakoids of chloroplast contain pigments which absorb light of different wavelengths and carry out the photochemical reactions. These pigments are packed into functional clusters called photosystems-PS-I and PS-II.

(a) Name the pigments that constitute the photosystems.

(b) What is the function of Photosystems?

Ans: 

• (i) Chlorophyll a, P₇₀₀, P₆₈₀.
• (ii) To trap the solar energy and convert it into chemical energy

21. Study the flow chart and complete it by substituting A-D with suitable words. (Attempt any two parts from A-D).

Ans: 

• A – Glycolysis
• B – Ethanol + CO2
• C – Anaerobic respiration in Muscle cells
• D – Krebs’ Cycle

22. Supply the technical term for the following

(a) Division of other cells in embryo sac like synergids or antipodal cells to give rise to additional embryos.

(b) The process in which the zygote may divide to give rise to two or more cells each of which develops into a separate embryo.

Ans: 

1. Adventive polyembryony.
2. Cleavage polyembryony.

23. Match the statement given in Column I with the right option in Column II

Column-I	Column-II
(i) Copper-T	(a) Interfere with the ovulation process and prevent fertilization
(ii) Condoms	(b) Prevent sperm from meeting the ovulated egg
	(c) Implantation is not possible
	(d) Permanently prevent fertilization

Ans: 

(i) Copper-T – (a) Interfere with the ovulation process and prevent fertilization

(ii) Condoms – (b) Prevent sperm from meeting the ovulated egg

24. Read the following passage and fill in the blanks with appropriate words.

(Attempt any two parts A-D)

Criss Cross inheritance in humans

A .and B . are examples of sex-linked inheritance in humans. The defective gene is located on C . chromosome. Thus a single defective gene causes disease in males while two defective genes ( D . condition) only can cause the disease in females.

Ans: 

• A – Red-green colour blindness
• B – Haemophilia
• C – X chromosome
• D – Homozygous condition

25. Aquatic ecosystems are classified on the basis of salinity into two types-Fresh water and Marine. The common flora and fauna found in fresh water bodies like rivers, lake include phytoplanktons, water hyacinth, water lily and zooplankton, crab, and fishes, respectively. Wetlands are between aquatic and terrestrial ecosystems. They show an edge effect and form an ecotone.

(a) What is the study of freshwater ecosystem known as?

(b) Define ecotone.

Ans: 

1. Limnology
2. Ecotone is a transitional zone between two ecosystems.

26. Study the diagram given below carefully and answer the questions that follow. Identify the processes “A” and “B”.

Ans: 

• A – Photosynthesis
• B – Respiration

27. Given below is the list of vitamins with their functions. Choose the incorrect pairs of vitamins with reference to their function.

(a) Vitamin A: Maintenance of vision

(b) Vitamin C: Formation of blood

(c) Vitamin D: Healthy bones and teeth

(d) Vitamin K: antioxidant: ageing vitamin

Ans: Incorrect pairs are, 

• (b) Vitamin C: Formation of blood
• (d) Vitamin K: antioxidant: ageing vitamin

28. Fill in the spaces A and B in the sentences given below

(a) Cell-mediated immune response is mediated by A.

(b) Humoral immune responses is mediated by B.

Ans: 

1. Cytotoxic T-cells and natural killer cells. 
2. Antibodies.  

SECTION – C (2 Marks)

29. What are the four nutritional categories found in bacteria?

Ans: The four nutritional categories found in bacteria are, 

• Autotrophs
• Saprotrophs
• Symbionts
• Parasites

30. Analyse the differences between striated muscles and unstriated muscles with reference to their shape.

Ans: 

Striated muscles	Unstriated muscles
Elongated, cylindrical, and unbranched fibres	Spindle-shaped and tapering.
Myofibrils are so arranged in the cytoplasm that striations are seen.	No such striations are visible here, as the myofibrils are not uniformly arranged.

31. (a) Name the two biochemical reactions for biosynthesis of amino acids in plants.

Ans: 

(i) Reductive amination reaction

(ii) Transamination reaction

OR

(b) Name the two proteins found in root nodules and help in nitrogen fixation.

Ans: 

(i) Leghaemoglobin

(ii) Nodulins

32. Identify A in the diagram given below and state its function

32. Identify A in the diagram given below and state its function

Ans: 

• A- Sinu auricular node.
• It initiates and regularises the heartbeat. Therefore, it is also called the pacemaker. 

33. Identify the type of neuron given in the diagram and state the function of axon.

Ans: 

• It is a neuron that conducts nerve impulses. 
• Axon: An axon carries the impulse from the cell body towards its terminal branches, which may either pass on the impulse to another neuron, or into a muscle or gland to bring about the required action.

34. (a) Why is the process of fertilization in flowering plants said to be double fertilization?

Ans: In flowering plants, one sperm fuses with the egg (syngamy) and forms a diploid zygote. The other sperm fuses with the secondary nucleus to form the primary endosperm nucleus, which is triploid in nature. Since two types of fusion, syngamy and triple fusion, take place in an embryo sac, the process is termed double fertilization.

OR

(b) What is the function of Endosperm in the flowering plants? Write the names of any

types of endosperms.

Ans: Endosperm provides food to the developing embryo. Types of endosperm are nuclear type, cellular type, and helobial type. 

35. Observe the given diagram and answer the questions that follow.

35. Observe the given diagram and answer the questions that follow.

(a) In which direction does the enzyme DNA polymerase catalyze DNA replication – 5′ to 3′ or 3′ to 5′?

(b) Which enzymes join the Okazaki fragments to form a complete DNA strand?

Ans: 

1. In 5’-3’ direction
2. Enzyme ligase

36. A group of food items is given in the table. Categorize them into energy-providing foods and bodybuilding foods. Cereals, legumes, meat, sugar, oil, fish, egg, jaggery

Ans: 

• Energy-providing foods: Cereals, Sugar, oil, and jaggery
• Body Building Foods: Legumes, meat, fish, and eggs. 

37. (a) Following is the representation of how a plasmid isolated from bacterium that causes galls in several plants is used to produce transgenic plants.

(i) Name the bacterium that causes galls in plants.

(ii) Name the plasmid used to transmit the desired genes.

Ans: 

(i) Agrobacterium tumefaciens causes galls (tumours) in plants.

(ii) T_i plasmid

OR

(b) Given below is the picture of a normal mouse (A) and a transgenic mouse (B).

Why is there an increase in the size of mouse (B)?

Ans: A Gene for growth hormone from rats was microinjected into mouse eggs. These mice grew larger than their littermates. This was because the rat gene got integrated into the mouse DNA and was being expressed.

SECTION – D  (3 Marks)

38. (a) Define obesity.

(b) List any two causes of obesity.

(c) State two Harmful effects of obesity.

Ans: 

1. The overweight and bulkiness of a person’s body due to the accumulation of carbohydrates and fats is called obesity.
2. Two causes of obesity are overeating and insufficient exercise
3. Hypertension and atherosclerosis are two harmful effects of obesity.

39. (I) Illustrate the 3 major phases in glycolysis.

Ans: The three major phases of glycolysis are activation, splitting of glucose, and oxidation. 

OR

(II) Distinguish between C3 and C4 plants with reference to the following characteristics.

(a) Carbon dioxide acceptor

(b) Carbon dioxide fixing enzymes

(c) First product of photosynthesis

Ans: Features C3 Plants C4 Plants

	C3 Plants	C4 Plants
(a) Carbon dioxide acceptor	5-Carbon sugar- ribulose biphosphate or RuBP	Phosphoenol pyruvic acid or PEP,
(b) Carbon dioxide fixing enzymes	Ribulose bisphosphate carboxylase/oxygenase or Rubisco.	Phosphoenol pyruvate carboxylase (PEP carboxylase)
(c) First product of photosynthesis	3-Phosphoglyceric acid (PGA).	Oxaloacetic acid (OAA).

40. (I) Observe the Lac operon diagram given below and answer the questions that follow.

(a) Which substance acts as inducer in this operon?

(b) Where does RNA polymerase bind to initiate transcription?

(c) What are the genes z, y, a called as?

Ans: 

1. Lactose is the inducer in this operon. 
2. RNA polymerase binds to the promoter gene p. 
3. Genes z, y, and a are structural genes, where gene a codes for the enzymes galactosidase, permease, and transacetylase. 

OR

(II) Study the karyotype given below and answer the questions that follow.

(II) Study the karyotype given below and answer the questions that follow.

(a) What is this disorder known as?

(b) How many chromosomes are present in the individuals with this disorder?

(c) State one typical feature of this syndrome.

Ans: 

1. Klinefelter’s syndrome
2. This individual male has 47 chromosomes with an extra X chromosome. 
3. A typical feature of this syndrome is being tall and mentally retarded. 

41. Deficiency in minerals in our food may lead to deficiency diseases. Name which mineral deficiency may lead to the following :

(a) Anaemia

(b) Osteomalacia

(c) Goitre

Ans: 

1. Deficiency of Vitamin B12
2. Deficiency of Vitamin D
3. Iodine deficiency

SECTION – E  (5 Marks)

42. (a) A snapdragon plant with red flowers (RR) is crossed with a plant with white flowers (rr). Work out the cross up to F2 generation. Find out the phenotypic and genotypic ratio.

Ans: 

Parents	RR x rr
Gametes	R, R x r, r
F1	Rr (Pink)
F2	1 Red: 2 Pink: 1 White
	1RR: 2Rr: 1rr

OR

(b) A tall pea plant with red flowers (TTRR) is crossed with white dwarf plants (ttrr). Work out the phenotypic ratio in F2 for this cross.

Ans: 

Cross between TTRR (tall red) x ttrr (Dwarf white)

Gametes formed by TTRR are TR, TR

Gametes formed by ttrr are tr and tr

Gametes	TR	TR
tr	TtRr – Tall red	TtRr – Tall red
tr	TtRr – Tall red	TtRr – Tall red

The F1 generation is all Tall red with a genotype of TtRr. 

F2 is crossed between TtRr x TtRr

The gametes procured are TR, Tr, tR, tr

Gametes	TR	Tr	tR	tr
TR	TTRRTall red	TTRrTall red	TtRRTall red	TtRrTall red
Tr	TTRrTall red	TTrrTall white	TtRrTall red	TtrrTall white
tR	TtRRTall red	TtRrTall red	ttRRDwarf red	ttRrDwarf red
tr	TtRrTall red	TtrrTall white	ttRrDwarf red	TtrrDwarf white

The phenotypic ratio in F2 is 9 tall red: 3Dwarf red: 3 Tall white: 1 Dwarf white

43. (a) What is Chemosynthesis? Write any four differences between chemosynthesis and photosynthesis.

Ans: Chemosynthesis is the process in bacteria where they use chemical energy to reduce CO₂ for carbohydrate synthesis. 

Chemosynthesis	Photosynthesis
It occurs only in colourless anaerobic bacteria	This process occurs in all green plants, including green bacteria.
During this process, CO2 is reduced to carbohydrates without light and chlorophyll.	CO2 and H2O are converted into carbohydrates in the presence of light and chlorophyll.
Here, chemical energy released during the oxidation of inorganic substances is used up to synthesise carbohydrates.	Light energy is converted into chemical energy and stored in the form of carbohydrates.
No pigment molecule is involved, and oxygen is not evolved.	Several pigments are involved, and oxygen is evolved as a by-product.
No photophosphorylation takes place.	Photophosphorylation takes place, i.e., ATP is produced.

OR

(b) With the help of a diagram explain the external structure of human heart.

Ans: 

Additional Study Materials

• NIOS Class 12 Biology PYQ April 2025 Set A
• NIOS Class 12 Biology Terminal Exercises Solutions
• NIOS Class 12 Biology Intext Questions Solutions