NIOS Biology PYQ April 2025 Set A

NIOS Biology Previous Year Question Paper 2025 Set A

SECTION A

Note: Question Nos. 1 to 16 consist of multiple-choice type questions (MCQs) carrying 1 mark each.

1. Which one of the following is not a characteristic feature of flatworms (Platyhelminthes)? 

(A) No digestive system 

(B) Having scolex

(C) Mostly parasitic 

(D) Coelomate

2. Cambium is a/an

(A) apical meristem 

(B) intercalary meristem

(C) lateral meristem 

(D) complex tissue 

3. Oversecretion of thyroxine produces

(A) exophthalmic goiter 

(B) simple goiter

(C) cretinism 

(D) myxoedema 

4. Self-pollination is observed in pea plants as their

(A) Stamens and pistils develop at the same time (synchronous) in closed flowers

(B) Stamens and pistils develop at different times

(C) Stamens and pistils are found in different plants

(D) Male and female sex organs are found in different flowers 

5. In a healthy human female, ovum is matured and released at what time of menstrual cycle? 

(A) 1st day of menstrual cycle

(B) Between 13th–14th day of menstrual cycle

(C) 18th day after start of menstrual cycle

(D) 28th day after start of menstrual cycle

6. The end products of glycolysis in muscles are

(A) pyruvic acid, 36 ATP 

(B) pyruvic acid, 4 ATP

(C) ethyl alcohol, 2 ATP 

(D) pyruvic acid, 2 ATP 1

Ans: It’s lactic acid + 2 ATPs.

7. The correct sequence of development of embryo in human female is

(A) union of sperm and ovum → zygote → morula → blastocyst

(B) morula → zygote → union of sperm and ovum → blastocyst

(C) zygote  →morula → blastocyst → union of sperm and ovum

(D) blastocyst → morula → zygote → union of sperm and ovum 

8. The types of inflorescence with one example each are given below. Identify the wrong pair. 

(A) Hypanthodium — fig 

(B) Umbel — coriander

(C) Cymose — wheat 

(D) Racemose — mustard

9. Oxytocin is the hormone secreted by pituitary for

(A) uterine contraction for childbirth 

(B) formation of corpus luteum

(C) ovulation 

(D) menstrual cycle 

10. In a dihybrid Mendelian cross, phenotypic ratio in F2 generation was 9: 3: 3: 1. In this, the 1/16 portion represents

(A) recessive phenotypic condition for both the characters

(B) one dominant and one recessive character

(C) both dominant characters

(D) new recombinants due to crossing over 

11. Cyanocobalamin is

(A) vitamin A 

(B) vitamin D

(C) vitamin B12 

(D) vitamin C 

12. Fraternal twins are produced when

(A) two ova are fertilized by two sperms

(B) fertilized ovum divides into two independent cells each develops into two separate individuals

(C) ova are developed into two embryos without fertilization

(D) twins produced from one egg fail to separate 

13. Elderly people often get their bones fractured during a slightest fall. The possible condition diagnosed in them is

(A) obesity 

(B) osteomalacia/osteoporosis

(C) anaemia 

(D) rickets 

14. Bacteria are preferred in experiments of recombinant DNA technology because

(A) bacteria have a huge single chromosome

(B) they have extranuclear chromosomes—the plasmid

(C) their chromosomes have exons and introns

(D) they have pili on their body surface 

15. The enzyme that joins DNA fragments is

(A) ligase 

(B) restriction enzyme

(C) polymerase 

(D) primase 

16. Which one of the following examples is not a transgenic variety? 

(A) Cotton 

(B) Corn

(C) Goat 

(D) Man

SECTION B (2 Marks)

Note: Question Nos. 17 to 28 are objective-type questions carrying 2 marks each.

17. Identify the wrong statements (any two): 

(a) Gametes are unicellular haploid.

(b) Spores have haploid nucleus.

(c) Zygotes have diploid nucleus.

(d) Zoospores are non-motile.

Ans: The wrong statement here is (d) Zoospores are non-motile.

18. Fill in the blanks [attempt any two parts from the following]: 

(a) Mitochondrion is called as the _____ of the cell.

(b) Conjoint, collateral, and open vascular bundles are found in _____stem.

(c) Yeast reproduces by _____ method.

(d) Ciliated columnar epithelium is found as lining of _____.

Ans: 

1. Powerhouse
2. Dicot
3. Budding
4. Trachea

19. Match the items given in Column I with the correct items given in Column II: 

Column–I	Column–II
(a) FSH	(i) Male hormone
(b) Testosterone	(ii) Placenta
	(iii) Graafian follicle
	(iv) Controls blood sugar

Ans: 

1. (a) FSH- (iii) Graafian follicle
2. (b) Testosterone- (i) Male hormone

20. The flow of blood is shown in diagram through heart, labelled as A, B, C, and D. Identify any two of them. 

Ans: 

1. Tissues with very little oxygen and a lot of CO₂
2. Different parts of the body
3. Pulmonary veins
4. Pulmonary artery

21. Match the items given in Column I with the correct items given in Column II: 

Column–I	Column–II
(a) Bulliform cells	(i) Xylem
(b) Guttation	(ii) Hydathodes
	(iii) Monocot leaf
	(iv) Palisade parenchyma

Ans: 

1. (a) Bulliform cells – (iii) Monocot leaf
2. (b) Guttation – (ii) Hydathodes

22. Given below is the structure of DNA. Redraw the diagram and fill in the blanks (any two):

Ans: 

23. Explain briefly any two of the following: 1×2=2

(a) Translation

(b) Transcription

(c) Primers

(d) t-RNA

Ans: 

1. Translation is the process of translating the information on the mRNA into protein.
2. Transcription is the process of copying information coded in DNA as a complementary messenger RNA or mRNA.
3. Primer is a short RNA molecule of about 5 to 10 bases.
4. tRNA is transfer RNA that “transfers” the amino acids to their respective positions

during the synthesis of protein.

24. Given below is the section of ovary. Identify the spots A and B.

Ans: 

1. Ruptured Graffian follicle
2. Corpus luteum

25. Study the following passage and fill in the blanks with appropriate words [attempt any two parts from A–D]: 

A is an association between maternal and foetal tissue. B is a tough structure which serves as the blood vascular connection between the foetus and uterine wall. The embryo is enclosed in a sac called C , which is filled with D . It acts as shock absorber to protect embryo from damage.

Ans: 

1. Placenta
2. Umbilical cord
3. Amnion
4. Amniotic fluid

26. Some people tend to take vitamins in excessive amounts. Excessive intake of water-soluble vitamins may not cause harm. But the excess amount of fat-soluble ones are poisonous to the body.

(a) What is hypervitaminosis?

(b) Name two fat-soluble vitamins. 

Ans: 

1. The disease caused by the presence of vitamins in excessive quantities in the body is called hypervitaminosis.
2. Fat-soluble vitamins are vitamins A, D, E, and K

27. Red-green colour blindness is a sex-linked disorder. Observe the flow chart of the disease given below:

(a) Which parent is contributing the gene for colour blindness to the offspring?

(b) What are the chances of the daughters showing the disease to these parents? 

Ans: 

1. The mother is contributing the gene for colour blindness.
2. Daughters will not show this disease in this cross as two defective genes (homozygous condition) can only cause the disease in females.

28. Given below is the sequence to succession of communities in a habitat. Fill in the gaps A and B with appropriate answer: 

Ans: 

1. Lichens
2. Shrubs

SECTION–C (2 Marks)

Note: Question Nos. 29 to 37 are very short answer-type questions carrying 2 marks each.

29. Write the names of two organisms belong to each one of the following groups: 

(a) Arthropoda

(b) Aves

Ans: 

1. Arthropoda: Scorpion, Prawns, Millipede, Cockroach (any two)
2. Aves: Ostrich, Kiwi, Pigeon, Crow.

30. Which tissue bears the following characters? 

(a) Small and compactly packed cells which divide continuously.

(b) End walls open and cells join to form a long tube having a dead cell wall.

Ans: 

1. Meristematic tissue
2. Xylem vessels

31. Why are bacteria called monerans? Support your answer by giving any two characters.

Ans: 

• Since only bacteria are prokaryotic (lacking a true nucleus, that is, without a nuclear membrane), Monera is the only prokaryotic kingdom.
• Most bacteria are single-celled or unicellular (monere: single), but actinomycetes and some cyanobacteria are multicellular and filamentous, wherein filaments may be branched.
• Monerans are also the most numerous of all living cellular organisms.

Or 

Maize is a monocot plant. Give any two valid reasons for considering it so.

Ans: Maize has a fibrous root system, which is a main characteristic of monocots. Maize lacks secondary growth in its stem and can easily bend. 

32. With the help of a lined diagram only, show the structural components of a habitat. 

Ans: 

Ans: 

33. How do immigration and emigration affect the existing population density?

Ans: Immigration refers to the movement of individuals into a new area. It increases the population. The movement of individuals of a population out of a region permanently is termed emigration. Emigration reduces the population. 

Or 

A rapidly growing population has a larger number of individuals of reproductive age. What is the growth pattern of the population if more pre-reproductive individuals are present in the population?

Ans: If there are pre-reproductive individuals present in the population. There will be an exponential growth in the population. After reaching a peak, there will be a sudden crash or decline due to environmental or other factors.

34. Tetracycline is a broad-spectrum antibiotic. Why do we say so? What is the source of it?

Ans: Broad-spectrum antibiotics can be used against more than one kind of pathogenic bacterium. Tetracycline is obtained from Streptomyces sp. 

35. Name two types of enzymes produced in large scale through genetic engineering. Mention one use of each of enzymes.

Ans: 

• Proteases: Used in the manufacture of detergents, meat tenderisers.
• Amylases: Used in the manufacture of beer, bread, and textiles

Or 

Write the names of two hormones produced in large scale through recombinant DNA technology. Name one therapeutic application for each.

Ans: 

• Insulin for Diabetes mellitus
• Growth hormones for Pituitary dwarfism

36. Write any four important functions of proteins in our body.

Ans: Functions of proteins (any four)

• Proteins are required for building and maintaining body tissues.
• Proteins are found in all the enzymes e.g. Trypsin, pepsin, and rennin.
• Some proteins function as hormones to regulate many body functions. For example, insulin is a hormone that regulates blood glucose levels in the body.
• Proteins also act as antibodies and protect the body from antigens (foreign agents).
• Transport protein carries different substances from the blood to the tissues in the body. Haemoglobin is a transport protein.

37. Brain is covered by three membranes called _____. The space between them is filled with _____ fluid.

Ans: Meninges and cerebrospinal fluid.

SECTION–D (3 Marks)

Note: Question Nos. 38 to 41 are short answer-type questions carrying 3 marks each.

38. Draw a neat diagram of a typical bisexual dicotyledonous flower and label its four whorls (parts):

Ans: 

39. Write the name of one surgical method of contraception carried on in human males. Explain how it is performed.

Ans: Vasectomy: In males, the vas deferens, through which sperm travel out of the epididymis, is ligated (tied) by the surgeon to prevent sperm from going out of the body. This method is temporary and can be reversed by the surgeon if required. For permanently preventing fertilization, the vas deferens is cut and the open ends ligatured (tied by thread).

Or 

Write the name of one contraception carried on in human females. Describe the procedure adopted for it.

Ans: Oral contraceptive pills are tablets that have to be taken as per directions from a medical practitioner. These pills interfere with ovulation and, in turn, prevent fertilization.

40. Define the following terms:

(a) Amnion

(b) Demography

(c) Population growth rate

Ans: 

1. Amnion: From the first few weeks of development, the embryo is enclosed in a sac called amnion which is filled with amniotic fluid.
2. Demography is the scientific and statistical study of the human population. It deals with population growth, its composition (age, sex ratio), and its distribution in space.
3. Population growth rate is the difference between the birth rate and the death rate.

Or 

Write three effects of uncontrolled population growth on a nation.

Ans: 

• Increasing population and transportation: An Increase in population requires a corresponding increase in the means of transport. The increase in the number of automobiles as a consequence of phenomenal population growth has increased the pollution load (air pollution, water pollution, and solid waste pollution).
• Increasing population and education: Education is most important for economic and social upliftment. Although the literacy rate is growing, we still have a very large number of illiterates in the country. The increasing population further adds to the problems of providing education to all.
• Increasing population, agricultural development, and environmental degradation: In order to meet the food requirements of the ever-increasing population of the country, new agricultural techniques have been adopted. Some of these have proved to be detrimental to the environment.

41. (a) Briefly explain the transformation in bacteria.

(b) Why do we consider DNA replication as semiconservative? Explain briefly.

Ans: 

1. Transformation in bacteria is the process by which a bacterium takes up genetic material from its surroundings and incorporates it into its own DNA, leading to a change in its characteristics. This was first demonstrated by Frederick Griffith in 1928 using Streptococcus pneumoniae. He found that harmless rough (R) bacteria became virulent when mixed with heat-killed smooth (S) virulent bacteria. Later, in 1944, Avery, MacLeod, and McCarty proved that DNA was responsible for this transformation, showing that DNA is the transforming principle in bacteria.
2. DNA replication is semiconservative, since in the two new molecules formed,  one parental strand is conserved and the other strand is newly synthesized. Messelson and Stahl experimentally proved the semiconservative mode of DNA replication.

Or 

Draw a replicating DNA molecule showing—

(a) parental strand;

(b) Okazaki fragments;

(c) leading strand;

(d) replication fork.

Ans: 

Ans: 

SECTION–E (5 Marks)

Note: Question Nos. 42 and 43 are long answer-type questions carrying 5 marks each.

42. Following is the information given with regard to the respiratory processes in living beings. Fill in the gaps with appropriate answers: 1×5=5

Type of respiration	Raw material	Site	Products
Aerobic	–	Cytoplasm and mitochondria	–
Anaerobic	–	–	CO2 + 2 ATP
Kreb’s Cycle	–	Mitochondria	CO2 + NADH2

Ans: 

Type of respiration	Raw material	Site	Products
Aerobic	C6H12O6	Cytoplasm and mitochondria	CO2 + H2O + 38ATP
Anaerobic	C6H12O6	Cytoplasm	CO2 + 2 ATP
Kreb’s Cycle	2 Pyruvic acid	Mitochondria	CO2 + NADH2

Or 

Complete the following statements: 1×5=5

(a) Muscular pain we get after prolonged exercise is due to _____.

(b) Lenticels are found in _____. Their function is _____.

(c) Each NADH₂ molecule produces _____ ATP molecules.

(d) Photosynthesis is a _____ path and respiration is a catabolic path.

Ans: 

1. Lactic acid
2. Bark of woody plants.
3. Facilitates gaseous exchange
4. 3ATPs
5. Anabolic

43. Draw a transverse section of a dicot root and label the following parts: Epiblema, cortex, endodermis, pericycle, protoxylem, metaxylem, phloem, and pith.

Ans: 

Ans: 

Or 

(a) With the help of a diagram, describe the structure of stomatal apparatus of a dicot leaf.

(b) Where are they located in xerophytes?

(c) What are bulliform cells? Where are they found? Write one important function of these cells.

Ans: 

1. In dicot leaves, the stomatal apparatus is made up of two semicircular guard cells surrounding a pore-stoma. The guard cells contain chloroplasts and regulate the opening and closing of stomata. Stomatal pores open into the intercellular spaces (substomatal cavity) of the mesophyll. The number, shape, and distribution of stomata vary depending on the plant, whether it is a xerophyte or a mesophyte.
   
   

2. On the lower surface.
3. Bulliform cells are a special type of cell (motor cells) found on the upper leaf surface of some monocots. They help the leaf to roll and unroll due to a change in its turgidity.

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