CBSE Class 12 Biology Question Paper 2021 Set 04 Solved

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Official CBSE Exam Papers for Class 12 Biology

Review targeted exam resources with the CBSE Class 12 Biology Question Paper 2021 Set 04 Solved. Built according to official CBSE standards for the 2026-27 academic year, these downloadable Class 12 Biology question papers support effective revision and performance tracking.

Solved Previous Year Papers for Biology

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SECTION A
 
1. After a brief medical examination a healthy couple came to know that both of them are unable to produce functional gametes and should look for an „ART‟ (Assisted Reproductive Technique). Name the „ART‟ that you can suggest to them to help them bear a child.
 
2. List any two characters of Pea plants used by Mendel in his experiments other than height of the plant and the colour of the seed.
 
3. Mention the role of Restriction Enzymes in Recombinant DNA technology. 
 
4. What is Biopiracy? 
 
5. Write the importance of MOET. 

SECTION B
 
6. What is amniocentesis? Justify the statutory ban on it. 
 
7. Why is the possibility of human female suffering from hemophilia rare? Explain. 
 
8. What is the pathogenic property of baculovirus, used as a biological agents? Name the genus of these organisms.
 
OR
 
Mycorrhizal association exists between fungi (Glomus sp) and roots of higher plants. How is this association beneficial to each member?
 
9. a) Why is small amount of curd added to milk?
b) What is the difference between fermentation of dough for making dosa and bread?
 
10 “Niche is a part of a habitat.” Explain with the help of an example. 
 
SECTION C
 
11. (a) Draw a diagram of Pistil showing pollen tube growth in angiosperm and label (i)
Stigma; (ii) male gametes; (iii) micropyle and (iv) Ovule.
(b) Write the function of micropyle.
 
12. Give reason : -
(a) A liverwort plant is unable to complete its life cycle in a dry environment.
(b) Number of male gametes produced is much more than the female gametes produced.
(c) Organisms exhibiting external fertilization show great synchrony between the sexes and
release a large number of gametes into surrounding medium.
 
13. How is Darwin‟s theory of natural selection different from Hugo deVries theory of mutation? Explain
 
14. Write the three basic facts that are highlighted in Mendel‟s Law of Dominance. 
 
15. “A population has been exhibiting genetic equilibrium”. 
Answer the following with regard to the above statement.
(i) Explain the above statement.
(ii) Name the underlying principle.
(iii) List any two factors which would upset the genetic equilibrium of the population.
(iv) Take up any one such factor and explain how the gene pool will change due to that factor
 
16. (a) Name the causative agent of amoebiasis and mention its symptoms.
(b) Write how does it spread.
 
17. Microbes play a dual role when used for sewage treatment as they not only help to retrieve usable water but also generate fuel. Write in points how this happens?
 
18. What was the challenge for production of insulin using rDNA techniques? How did Eli Lilly produce insulin using rDNA technology?
 
19. (a) What is an “allergic reaction”?
(b) Name any two drugs used to quickly reduce the symptoms of allergy.
(c) Why do more and more children in metro cities of India suffer from allergies and asthma?
 
20. Explain the role(s) of the following in Biotechnology:
(a) Restriction endonuclease
(b) Gel - electrophoresis
(c) Selectable markers in pBR322.
 
OR
 
Write the steps you would suggest to be undertaken to obtain a foreign-gene-product.
 
21. Why do lepidopterans die when they feed on Bt cotton plant? Explain how it happens. 
 
22. Explain with the help of two examples how certain plants have evolved morphological and chemical defenses against primary consumers such as cows and goats.
 
SECTION D
 
23. A son persuades his father to replace his old mobile phone with the latest model launched in the market. He also shares the latest features it has and explains how it can be of a help to him in the modern technological world. Father is reluctant in buying a new one and tries to explain about its environmental impact. How do you think, the biologist father would try to convince his son? Justify the arguments of father and son both, by mentioning positive aspects of the behavior displayed by both of them in the situation concerned (three each).
 
SECTION E
 
24. (a) What are the benefits of choosing a dioecious plant species for plant breeding experiments?
(b) How would you proceed to cross-pollinate a monoecious flower?
(c) Draw a labelled schematic diagram of T.S. of an anther of an angiosperm.
 
OR
 
(a) Explain the hormonal regulation of spermatogenesis in humans.
(b) Draw the diagram of a human sperm. Label and write the functions of the components of its head.
 
25. State and explain the “law of independent assortment” in a typical Mendelian dihybrid cross.
 
OR
 
(a) How are the observations made during moth collection in pre- and post-industrialized era in England support evolution by Natural Selection?
(b) Explain the phenomenon that is well represented by Darwin‟s finches other than natural selection.
 
26. (a) Write the percentage of land area that was covered by forests by the end of the last century.
(b) Describe any two practices that led to deforestation.
(c) State the consequences of deforestation.
(d) Suggest a method to overcome deforestation.
 
OR
 
(a) Comment on the pattern in which all communities undergo a change in composition and structure with changing environmental conditions.
(b) Explain „Climax community‟ and „sere‟.
(c) Differentiate between primary and secondary succession with examples


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Are the solutions for CBSE Class 12 Biology Question Paper 2021 Set 04 Solved based on the official CBSE marking scheme?

Yes, the solutions for CBSE Class 12 Biology Question Paper 2021 Set 04 Solved are prepared by subject matter experts as per official marking scheme. Class 12 students will understand the structure of answers and 'step-marks' methodology Biology.

How does solving CBSE Class 12 Biology Question Paper 2021 Set 04 Solved help in preparing for the 2026 exams?

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Can I access CBSE Class 12 Biology Question Paper 2021 Set 04 Solved in different languages?

Yes, where applicable, CBSE Class 12 Biology Question Paper 2021 Set 04 Solved is available in both English and Hindi mediums. All students from Class 12 can access Biology study material in their preferred language.

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