Cbse class 12 biology sample paper model 2 - http://cbse.edurite.com/cbse-biology/cbse-class-12-biology.html

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Sample Question Paper
Biology
Class – XII
Time: 3 hrs. M.M.: 70
General Instructions:
(i) All questions are compulsory.
(ii) This question paper consists of four sections A, B, C and D. Section A contains 8
questions of one mark each, Section B is of 10 questions of two marks each, Section C is
of 9 questions of three marks each and Section D is of 3 questions of five marks each.
(iii) There is no overall choice. However, an internal choice has been provided in one
question of 2 marks, one question of 3 marks and two questions of 5 marks weightage. A
student has to attempt only one of the alternatives in such questions.
(iv) Whenever necessary. The diagrams should be neat and properly labeled.
Section-A (1x 8 = 8)
1. Write the formula to calculate the allele frequency in future generation according to Hardy
– Weinberg genetic equilibrium.
2. List any two economically important products for humans obtained from Apis indica.
3. Define uniparental.
4. Name any two vertebrate body parts that are homologous human forelimbs.
5. The gene I that controls the ABO blood grouping in human being has three alleles IA, Ib, and
i.
a) How many different genotypes are likely to be present in the human population?
b) Also, how many phenoytpes are possibly present?
6. What is fragmentation?
7. What stimulates pituitary to release the hormone responsible for parturition? Name the
hormone.
8. Name the common ancestor of the great apes and man.

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Section-B (2x 10 =20)
9. How is DNA isolated in purified form from a bacterial cell?
10. Explain metastasis. Why is it fatal?
11. Name the two types of immune systems in a human body. Hey are cell mediated and
humoral immunities so called?
12. What do you understand by amniocentasis? Why is there a statutory ban on this? Give
reason.
13. The steps in a programme are:
--- Collection of germplasm
--- Cross-breeding the selected parents
--- Selecting superiors recombinant progeny
--- Testing, releasing and marketing new cultivators.
(i) What is this programme related to?
(ii) Name two special qualities as basis of selection of the progeny?
(iii) What are the outcomes of the programme?
(iv) What is the popular term given to this outcome?
14. A man 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.
15. Banana is a parthenocarpic fruit whereas orange show polyembryony. How are they
different from each other with respect to seeds?
16. Describe the responsibility of GEAC, set-up by the Indian Government.
17. How does the Mediterranean orchid Ophrys ensure its pollination by bees?
18. List the specific symptoms of pneumonia. Name its causative organism.

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Section-C (3x9=27)
19. Expand the following and explain any one of them.
(a) IVF
(b) ZIFT
(c) IUI
(d) MTP
20. Draw a well labeled diagram of the microscopic structure of human sperm.
21. Fertilization is essential for production of seed, but in some angiosperms seeds develop
without fertilization:
(i) Give an example of an angiosperm that produces seed without fertilization. Name
the process.
(ii) Explain two ways by which seeds develop without fertilization.
22. The events of menstrual cycle are represented below. Answer the questions following the
diagram –
Poliferative phase or Follicular phase
(5th
to 15th
day)
Menstruation
(1th to 5th
day)
Luteal phase or Secretory phase
(16th
to 28th
day)
(i) State the levels of FSH, LH and Progesterone simply by mentioning the high or low,
around 13th
and 14th
day and 21st
– 23rd
day.
(ii) In which of the above mentioned phases does the egg travel to the fallopian tube?
(iii) Why is there no menstruation upon fertilization?
23. (a) Expand BOD.
(b) Ata particular segment of a river near a sugar factory, the BOD is much higher than the
normal level. What is it indicative of? What will happen to the living organisms in this part
of the river?

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(c) Under what conditions will the BOD be lowered in the river? How will it affect the
aquatic life?
24. (a) Draw the structure of the initiator tRNA adaptor molecule.
(b) Why is tRNA called an adaptor molecule?
25. Water is very essential for life. Write any three features both for plants and animals which
enable them to survive in water scarce environment.
26. How can crop varieties be made disease resistant to overcome food crisis in India? Explain.
Name one disease resistant variety in India of:
(a) Wheat to leaf and stripe rust.
(b) Brassica to white rust.
27. Write the source and the effect on the human body of the following drugs:
(i) Morphine,
(ii) Cocaine,
(iii) Marijuana.
Section-D
28. (a) Healthy ecosystems are the base of wide range of (ecosystem) services. Justify.
(b) Explain the differences and similarities between Hydrarch and Xerarch successions of
plants.
29. Describe the mechanism pattern of inheritance of ABO blood groups in humans.
30. In angiosperms, the pollen germinates to produce pollen tube that carries two gametes.
Moreover, it is generally observed that the number of male gametes produced is several
thousand times the number of female gametes. (Value based Question)
(i) What is the purpose of carrying two gametes when single gametes can fertilize
egg?[3]
(ii) Why the number of male gametes produced in large number than female
gametes?[2]