CBSE practice Questions

Biology Sample Paper class 12

class 12 biology questions

CBSE Class 12 Biology question papers

1 mark Questions

Question: Why does hnRNA undergo splicing?

Question: Define SNP.

Question: How does colostrum provide initial protection against diseases to new born infants?

Question: Write any two examples of recent extinctions.

Question: What is the importance of DNA dependent RNA polymerase  ?

Question: Why are Amazon forests known as “lungs of the planet”.

Question: Give any two factors affecting decomposition.

Question: How do we determine order of genes on a chromosome?

Question: How is snow blindness caused in humans?

Question: Define Allen’s rule .

Question: Mention the strategy used to increase homozygosity in cattle for desired traits.

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Question: In F. Griffith’s experiment, how did the nonvirulent strain of Streptococcus pneumonia become virulent?

Question: Provide one word or one sentence information about plasmid with respect to its chemical nature and its duplication.

Question: Give any two examples where plants show unusual flowering phenomenon.

Question: The microscopic pollen grains of the past are obtained as fossils. Mention the characteristic of the pollen grains that makes it happen.

Question: Name the organism commercially used for the production of single cell protein.

Question: What is splicing?

Question: Why is colostrum provided to new born infants?

Question: 3 Mention the strategy used to overcome the problem of inbreeding depression in cattles.

Question: The microscopic pollen grains of the past are obtained as fossils. Mention the characteristic of the pollen grains that makes it happen.

Question: Name the organism commercially used for the production of single cell protein.

Question: Give any two examples where plants show unusual flowering phenomenon.

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Question: In F. Griffith’s experiment, how did the nonvirulent strain of Streptococcus pneumonia become virulent?

Question: Provide one word or one sentence information about plasmid with respect to its chemical nature and its duplication.

Question: Mention the role of molecular scissors in recombinant DNA technology.

Question: Name the embryonic stage that gets implanted in the uterine wall of a human female.

Question: What causes speciation according to Hugo de Vries?

Question: Name the cry-genes that control cotton bollworm and corn-borer respectively.

Question: Give an example where animal – plant interaction involves coevolution.

Question: State two different roles of spleen in the human body.

Question: Write names of the most common species of bees suitable for apiculture and an improved breed of chicken.

Question: In the whiptail lizards only females are born generation after generation. There are no males. How is this possible?

2 mark questions

Question: Describe the lactational amenorrhea method of birth control.

Question: Draw a labeled diagram of replication fork.

Question: Expand ELISA. On what principle is ELISA test based? List two ways by which an infection can be detected by this test.

Question: List the specific symptoms of filariasis. Name the causative organism.

Question: How does phosphorus cycle differ from carbon cycle?

Question: Why does introduction of alien species cause extinction of indigenous species? Give any one example.

Question: How is sixth episode of mass extinction different from previous episodes of extinction?

Question: What are conformers? What is the reason of success of mammals?

Question: A man with blood group A married a woman with B blood group. They have a son with AB blood group and a daughter with blood group O. Work out the cross and show the possibility of such inheritance.

Question: The male fruit fly and female fowl are heterogametic while the female fruit fly and the male fowl are homogametic. Why are they called so?

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Question: Name the plant source of ganja. How does it affect the body of the abuser?

Question: What is divergent evolution? Explain taking an example of plants.

Question: Name the causative organism of typhoid. How is this disease transmitted to other organisms and write any two symptoms of the disease.

Question: How does ADA deficiency affect human system? Explain any two approaches used for the treatment of the disease.

Question: Explain two ways of improper resource utilization that can cause degradation of natural resources.

Question: Explain the programme that is used to improve success rate of production of desired hybrid and herd size of cattle.

Question: Name the fungus used in organ transplant treatment. Write the product of this organism and explain its specific use.

Question: Why do normal cells not show cancerous growth?

Question: Name asexual reproductive structures in sponges, Penicillium notatum, algae and Hydra.

Question: How do macrophages in the human body act as ‘HIV factory’?

Question: Banana is parthenocarpic fruit whereas oranges show polyembryony. How are they different from each other with respect to seeds?

Question: Illustrate the recognition sequence of EcoRI and mention what such sequences are called? How does restriction endonuclease act on  a DNA molecule?

Question: Give any two devices developed by plants to discourage self pollination.

Question: List the specific symptoms of amoebiasis. Name the causative organism.

Question: Name the hormone present in oral pills. What is the mode of action of oral pills?

Question: Explain types of Intra Uterine Devices.

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Question: Explain the effect of deletion of the gene for ADA in an individual. How does the gene therapy help in this case?

Question: Suggest two non-genetic approaches for the treatment of SCID.

3 mark questions

Question: How is nucleosome formed? Draw the diagram of  a nucleosome.

Question: Draw a double stranded molecule of DNA, which is ready for transcription, label the polarity of DNA strands, promoter, terminator, sense and antisense strand.

Question: (a) Mention the property that enables the explants to regenerate into a new plant.

(b) A banana herb is virus-infected. Describe the method that will help in obtaining healthy banana plants from this diseased plant.

Question: Explain process of oogenesis in human female diagrammatically.

Question: (a) Name the technique used for separation of DNA fragments.
(b) Write the type of matrix used in this technique.
(c) How is the separated DNA visualized and extracted for use in recombinant technology.

Question: Describe the mechanism of inheritance of the ABO system of blood groups, highlighting the principle of genetics involved in it.

Question: State in what ways Stanley Miller simulated the conditions of :
(a) Primitive atmosphere on earth.
(b) energy source at the time of origin of life.
(c) formation of organic molecules of life to prove the theory of chemical evolution.

Question: Name the insect pest that is killed by the products of cryI Ac gene. Explain how the gene makes the plant resistant to the insect pest.

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Question: (a)Name the organism in which the vector pBR322 is inserted to get  the copies of the desired gene.
(b) Mention the area in the vector responsible for controlling the copy number of the inserted gene.
Name and explain the role of a selectable marker in this vector.

Question: A true breeding tall plant is crossed with a true breeding dwarf plant. F1 progeny is 100% tall and F2 has tall:dwarf in the ratio 3:1 ( 1 ) Explain why F1 shows only one type of parental phenotype ; ( 2 ) Name the patterns of inheritance in which the ratio deviates from above. Also mention the deviated ratio.

Question: A nonhemophilic couple was informed by their doctor that there is possibility of a hemophilic child to be born to them. Explain the basis on which the doctor conveyed this information. Give the genotypes and the phenotypes of  all the possible children who could be born to them.

Question: Draw a labeled diagram of the reproductive system in a human female.

Question: Identify the levels of biodiversity in India represented by :
(a) Diversity among amphibians in Eastern and Western Ghats.
(b) 50,000 strains of rice in India.
(c) Presence of deserts, mangroves and coral reefs in India.

Question: (a) Write the palindromic nucleotide sequence for the following DNA segment: 5’- GAATTC- 3’
(b) Name the restriction endonuclease that recognizes this sequence.
(c) How are sticky ends produced? Mention their role.

Question: What are biodiversity hotspots? What is the importance of biodiversity hotspots in conservation? Give some examples of biodiversity hotspots.

Question: What is population density ? Give any two methods of determination of population density

Question: Define decomposition. Explain all the steps of decomposition.
(a) How did Ahmed Khan solve the ever-increasing problem of accumulating plastic waste?
(b) what are the values shown by Ahmed Khan?

Question: One of the codons on mRNA is AUG . Draw the structure of t-RNA adapter molecule for this codon. Explain the uniqueness of this t-RNA.

Question: On seeing the bad state of roads, a student recommends to the Municipal Corporation to use polyblend.
(a) What is polyblend?
(b) What are the values shown by the student? (any four values)

Question: Explain the process of charging of t-RNA. Why is it essential in translation.

Question: Explain with the help of labeled diagram, the difference between an upright pyramid of biomass and an inverted pyramid of biomass.

Question: Why are plants obtained through micro-propagation termed somaclones? Name three food plants produced on commercial scale using this method.

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Question: Some tribal communities keep tracts of forests aside. These tracts are venerated and are given total protection.
(a) What are these tracts called? What is their importance?
(b) what are the values shown by these tribal communities?

5 Marks questions

Question: (a) “The pyramid of energy is always upright” Explain.
(b) Explain with the help of a labeled diagram, the difference between an upright pyramid of biomass and an inverted pyramid of biomass.

Question: (a) List any four abiotic components that lead to variations in the physical and chemical conditions of different habitats.
(b) Explain the impact of these components on the distribution of organisms in different habitats.

Question: (a) Explain Griffith’s series of experiments where he witnessed transformation in bacteria he worked with.
(b) Name the scientists responsible for determining the biochemical nature of ‘ transforming principle’ in Griffith’s experiments. What did they prove?

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Question: Give reasons why:
(a) most zygotes in angiosperms divide only after certain amount of endosperm is formed.
(b) groundnut seeds are exalbuminous and castor seeds are albuminous.
(c) micropyle remains as a small pore in the seed coat of a seed.
(d) integuments of an ovule harden and the water content is highly reduced, as the seed matures.
(e) apple and cashew are not called true fruits.

Question: (a) Draw a labeled diagram of L.S. an embryo of grass (any six labels).
(b) Give reason for each of the following:
(i.) anthers of angiosperm flowers are described as dithecous.
(ii.) hybrid seeds have to be produced year after year.

Question: Diagrammatically explain the development of embryo sac from megaspore mother cell. Show diagrammatically the stages of embryonic development from zygote upto implantation in humans.

Question: With an example, explain how biotechnology has been applied in each of the following:
(a) In curing Diabetes mellitus
(b) In producing more nutritionally balanced milk
Do you think it is ethical to manipulate organisms for human benefits? Justify your answer.

Question: How is a transgenic tobacco plant protected against Meloidegyne incognitia? Explain the procedure.

Question: How were the following proved experimentally? Explain.
(a) Biochemical nature of the transforming principle of Griffith’s experiment.
(b) DNA is the genetic material.

Question: (a) Why are herbivores considered similar to predators in the ecological context? Explain.
(b) Differentiate between the following interspecific interactions in a population:
(i.) mutualism and competition
(ii.) commensalism and amensalism

Question: (a) What depletes ozone in the stratosphere? How does this affect human life?
(b) Explain biomagnifications of DDT in an aquatic food chain. How does it affect the bird population?

Question: Name and describe the technique that will help in solving a case of paternity dispute over the custody of a child by two different families.

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Vishal Arora

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