CBSE Class 12 Biology sample question paper

For those appearing for boards as well as NEET, here is a sample question paper to access their preparedness. This question paper is prepared by Shalini Almadi- Biology Teacher, VidyaGyan School. Students need to map their timing for three hours. The test is for 80 marks, as per CBSE pattern, as rest will be marked in internals. To pass the exam, candidates need to score at least 33 per cent marks in both written and practical exam separately, as per CBSE norms.

SECTION A

Q1. Earthworms, sponges, tapeworm and leech are examples of: [1]

(a) Bisexual animals (b) Unisexual animals

(c) Annelida (d) Porifera

OR

In a heterothallic flowering plant, male and female flowers are called:

(a) Staminate and dioecious (b) Staminate and pistillate 

(c) Staminode and pistillate (d) Staminode and dioecious 

Q2. The scientists who were awarded the Nobel Prize for the discovery of antibiotics were: 

[1]

(a) Fleming and Waksman (b) Fleming and Salk

(c) Waksman and Florey (d) Fleming and Florey 

Q3. At which stage does the crossing over occurs for the formation of recombinants:         [1]

(a) Metaphase I (b) Anaphase I

(c) Prophase I (d) Telophase I 

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Q4. ‘Restriction’ in Restriction enzyme refers to: [1]

(a) Cleaving of phosphodiester bond in DNA by the enzyme
(b) Cutting of DNA at specific position only
(c) Prevention of the multiplication of bacteriophage in bacteria
(d) all of the above

Q5. Define mycorrhizae. [1]

(a) Association between algae and roots of higher plants

(b) Association between fungi and algae

(c) Association between fungi and thallophytes

(d) Association between fungi and roots of higher plants

OR

The reservoir for the gaseous type of biogeochemical cycle exists in:
(a) stratosphere (b) atmosphere
(c) ionosphere (d) lithosphere

SECTION B

Q6. The diagram below represents location of few lymphoid organs in human body: [2]

(i) Label A and B shown in the diagram shown.

 (ii) Which of the two organs shown is primary lymphoid organ? Why is it termed as primary lymphoid organ?

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OR

Conventional breeding is often constrained by the availability of limited number of disease resistance genes that are present and identified in various crop varieties or wild relatives. By changing the sequence of genes we can achieve desirable traits. What we call this method of creating genetic variations and how is it achieved?

Q7. Why DNA is the predominant genetic material, whereas RNA performs dynamic functions of messenger? [2]

Q8. Name two genes which make pBR322 a good cloning vector. Which of the two genes, do you think, is more important for a cloning vector and why? [2]

Q9. Draw a well-labeled diagram of an antibody molecule. [2]

OR

Fisheries has an important place in the Indian economy. Comment.

Q10. What type of pollutants can be removed by using scrubber? What kind of pollutants cannot be removed by using precipitators? [2]

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Q11. (a) What was the significance of using characters with opposite traits in pea plants by Mendel? [2].

(b) How did Mendel conclude that there is no blending of genes without having actual information about the behavior of genes?

Q12. Comment on the pollination relationships of Amorphophallus and Yucca. [2]

SECTION C

Q13. Habitat loss and fragmentation is the most important cause of driving animals and plants to extinction. Substantiate this statement with suitable example. [3]

OR

Explain the structure of a typical biogas plant.  

Q14. A mature pollen grain is a two-celled structure in many species of angiosperms. Justify the statement with the help of a labelled diagram. [3]

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OR

In the flowering plants male and female gamete fuse to form zygote. Write down the changes that occur in the zygote to form a mature embryo.

Q15. Give two entirely different evidences of convergent evolution, stating one example for each. [3]

Q16. Explain the action of a named restriction enzyme, highlighting the significance of sticky ends. [3]

Q17. Apart from IVF, which other ART can be used to treat an infertile female? Explain how it is different from IVF. [3]

Q18. Following is the discontinuous stand of DNA. [3]

A-T-G-C-G-T-A-G-C-A-C-A

a) Draw complete parental DNA strand from which this discontinuous strand is formed.

b) What will be the RNA sequence if continuous strand will function as template strand for transcription?

c) What will be the initiating codon and its amino acid if the above RNA is translated?

OR

What were the two major approaches towards Human Genome Project and name the methods used to complete the assignment?

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Q19. Was patenting of Basmati rice by American company a case of biopiracy? Why/ why not? [3]

Q20. Name a diagnostic test for AIDS. What is the underlying principle for the test? When does the patient show up the symptoms like bouts of fever, diarrhea and weight loss? [3]

Q21. Study the given pedigree chart and answer the question that follows: [3]

(i) Is the trait dominant or recessive and sex-linked or autosomal?

 (ii) Write the possible genotypes of the parents of first generation, second offspring of second generation and sibling of the third generation daughter of third couple of second generation.

 (iii) Give one example of such a trait and write its cause.

OR

Color blindness is a sex-linked disease. Following is the pedigree chart showing inheritance of color blindness in two families. Study the given chart and answer the questions that follow:

(i) What are the possible genotypes of 1 and 4?

 (ii) What is the probability of member 12 passing the disease to the next generation of sons if she is married to a normal male? Draw a cross for the same.

 (iii) Draw a Punnett square to depict the cross between 8 and 9 and based on the results write genotypes of 13, 14, 15 and 16.

[3]

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SECTION D

Q22. Knowingly or unknowingly we are benefitted by microbes in our household. Describe any three such occurrence from our daily life. [3]

Q23. A farmer is rearing and breeding his cattle within to increase the profit and production. What we call such type of breeding. Give one advantage and one disadvantage of this method. [3]

Q24. The census of a population of a country reveals that the number of births per 1000 population in a particular year is 19.3 and number of deaths per 1000 population is 7.3. Calculate intrinsic rate of natural increase. What does it reflect about the socio-economic conditions of the country?

SECTION E

Q25. “Everest is no longer a wilderness experience,” During the high season, the human waste, abandon mountaineering gears (e.g. empty oxygen cylinders, food wrapper, broken tents, battery, etc.) and other trash become the hazardous by-product of relentless commercial Everest expedition. A series of environmental issues started to surface due to these things. State the possible problems which would arise due to this and suggest measures that could be taken to reduce the pollution. [5]

OR

In the recent years, during Deepawali, Delhi and NCR face problem of clouds of dark coloured smog. Many steps were taken but the problem still persists. Analyse the possible reasons due to which the rules implemented were not successful. Suggest measures that can be taken to make next Deepawali morning clear and blue.

Q26. Blood group inheritance in human beings is different from plant height inheritance in pea plant. Compare and contrast the patterns of inheritance of the two given traits. [5]

OR

(i) How is XO type of sex determination different from XY type? What is the similarity between the two?

 (ii) What kind of abnormality, at the time of cell division, can lead to monosomy and trisomy of chromosomes? Give one example of each stating their respective symptoms.

Q27. (a) What are the different phases of menstrual cycle? What are the respective roles of different hormones? What will happen if oestrogen is not secreted in right amount? [5]

OR

How is oogenesis different from spermatogenesis? Explain the role of gonadotropin releasing hormone in both the processes. How will the two processes be affected if FSH is hyposecreted?