CBSE Class 12 Biology Question Paper 2020 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 2020 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

Access the complete question paper PDF for Class 12 Biology below. Regular practice with these targeted exam papers builds familiarity with standard question patterns and helps secure higher marks in final evaluations.

SECTION A
 
1 How can an alien piece of DNA made to multiply in a host cell? 
 
2 If adenine constitutes 30% of an isolated DNA fragment, then what is the expected % of the base cytosine in it?
 
3 What is the relationship between egret and grazing cattle? Why?
 
OR
 
How is competition avoided in Nature? Give example.
 
4 A male honeybee has 16 chromosomes whereas its female has 32 chromosomes. Give one reason. 
 
5 Name the vector of Chikungunya disease. 
 
SECTION B
 
6 How does geitonogamy differ from xenogamy in plants? 
 
7 How are transgenic animals made useful in chemical safety testing and studying diseases? 
 
8 What is meant by germplasm Collection? Describe its significance in plant breeding programmes.
 
OR
 
Name two alcoholic drinks produced in each of the following ways. (i) by distillation and (ii) without distillation.
 
9 A person shows unwelcome immunogenic reactions while exposed to certain substances. (a) Name this condition. (b) What common term is given to the substances responsible for this condition? (c) Name the cells and the chemical substances released which cause such reactions.
 
10 Monocistronic structural genes in eukaryotes have interrupted coding sequences, Explain. How are they different in prokaryotes?
 
11 Name two types of animals based on their temperature tolerance. 
 
12 Categories the following pairs of examples as convergent or divergent evolutions: (a) Eyes of octopus and mammals. (b) Wings of butterfly and birds. (c) Tuber of sweet potatoes and potato.
(d) Thorns in bougainvillea and tendrils in cucurbits.
 
SECTION C
 
13 How is Biotechnology used to produce Bt cotton? Explain. 
 
14 How does paleontological evidence support evolution of organisms on Earth? 
 
15 Explain free nuclear endosperm development.
 
OR
 
Mention any three differences between spermatogenesis and oogenesis.
 
16 Explain the role of S and P in the experiments conducted by Hershey and chase?
 
OR
 
Explain the mechanism of sex determination in honeybees.
 
17 Describe the three different practices under natural methods of birth control. 
 
18 How do mycorrhizae function as biofertilisers? Explain with example. Name one cyanobacteria that can be used as a biofertiliser.
 
19 How is Agrobacterium tumifaciens used in rDNA technology? Explain ii) What and how are other pathogens are used for the purpose. State two other methods by which host organism can be transformed.
 
20 After a rainy day Shruti found many dragonflies flying over stagnant water. She thinks these flies
come to drink water. i) Is Shruti,s explanation correct? Give your views
ii) Write the significance of your view in organic farming.
 
OR
 
What is biochemical oxygen demand (BOD) test? At what stage of Sewage treatment this test is performed? BOD level of three samples of water labelled as A, B and C are 30 mg/ L, 10mg/L and 500 mg/L respectively. Which sample of water is most polluted?
 
21 a) Taking one example each of habitat loss and fragmentation, explain how the two are responsible for biodiversity loss. b) Explain two different ways of biodiversity conservation.
 
22 What are statins? Name the microorganism that produces this substance. How is it medically important?
 
23 What are the producers in grass land and oceans .How is GPP different from NPP? Why is the productivity in oceans lesser than on land?
 
24 What will be the genotype and phenotype of the offspring if a colour blind man marries a carrier woman? Show the cross.
 
OR
 
How do histones acquire positive charge?
 
SECTION D
 
25 With the help of a cross find out the F2 offsprings produced by crossing homozygous red flower of Snapdragon when crossed with a homozygous white flower. Write the phenotypic and genotypic ratio. State the pattern of inheritance.
 
OR
 
Describe DNA replication and draw the diagram of a replication fork.
 
26 Describe the development of male gametophyte in angiosperms.
 
OR
 
What is placenta? What is its role? Justify Placenta as an endocrine tissue.
 
27 With a flow chart explain the process of decomposition. What factors affect this process?
 
OR
 
In Arcata, the town’s people have created an integrated waste water treatment process within a natural system. A citizen group called FOAM helps in upkeep of this project.
(a) What are the main steps in waste water management done in this way? (b) Ecosan in Kerala and Sri Lanka is also an initiative for water conservation. How?


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Where can I download the official PDF for CBSE Class 12 Biology Question Paper 2020 Set 04 Solved?

The CBSE Class 12 Biology Question Paper 2020 Set 04 Solved is available for download on StudiesToday.com. It includes complete set with all sections so that Class 12 students can practice with the exact same paper that came in the CBSE exams.

Are the solutions for CBSE Class 12 Biology Question Paper 2020 Set 04 Solved based on the official CBSE marking scheme?

Yes, the solutions for CBSE Class 12 Biology Question Paper 2020 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 2020 Set 04 Solved help in preparing for the 2026
exams?

Solving previous year papers like CBSE Class 12 Biology Question Paper 2020 Set 04 Solved is important to understand repeat themes and question difficulty levels of Biology. It helps Class 12 students to test their time management skills too.

Can I access CBSE Class 12 Biology Question Paper 2020 Set 04 Solved in different languages?

Yes, where applicable, CBSE Class 12 Biology Question Paper 2020 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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