CBSE Previous Year Question Papers March 2011

Set – III (Question)

Time allowed : 3 hours                            Maximum Marks : 70

General Instructions:

1. All questions are compulsory.

2.This question paper consists of four 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 3 questions

of five marks each.

3.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.

4. Wherever necessary, the diagrams drawn should be neat and properly

labelled.

SECTION – A

1. What stimulates pituitary to release the hormone responsible for parturition?

Name the hormone.

2. Pollinating species of wasps show mutualism with specific fig plants. Mention

the benefits the female wasps derive from the fig trees from such an interaction.

3. Biotechnilogists refer to Agrobacterium tumifaciens as a natural genetic

engineer of plants. Give reasons to support the statement.

4. How do algal blooms affect the life in water bodies?

5. Name the common ancestor of the great apes and man.

6. Write a difference between net primary productivity and gross productivity.

7. Mention the contribution of genetic maps in human genome project.

8. Name the phase all organisms have to pass through before they can reproduce

Sexually.

SECTION – B

9. A relevant portion of β-chain of haemoglobin of a normal human is given

below:

Val-His-Leu-Thr-Pro-Glu-Glu

1     2      3      4      5      6    7

The codon for the sixth amino acid is GAG. The sixth codon GAG mutates to

GAA as a result of mutation 'A' and into GUG as a result of mutation 'B'.

Haemoglobin structure did not change as a result of mutation 'A' whereas

haemoglobin structure changed because of mutation 'B' leading to sickle shaped

RBCs. Explain giving reasons how could mutation 'B' change the haemoglobin

structure and not mutation 'A'.

10. Biopiracy should be prevented. State why and how?

11. State the use of Biodiversity in modern agriculture.

12. Write the full form of VNTR. How is VNTR different from 'Probe'?

13. Why is tobacco smoking associated with rise in blood pressure and

emphysema (oxygen deficiency in the body)? Explain.

14.The above graph shows Species -Area relationship. Write the equation of the curve

'a' and explain.

OR

Differentiate between in situ and ex-situ approaches of conservation of

biodiversity.

15.The cell division involved in gamete formation is not of the same type in

different organisms. Justify.

16. Identify the type of the given ecological pyramid and give one example each of

pyramid of number and pyramid of biomass in such cases.

17. Describe the Lactational Amenrrhoea method of birth control.

18. What is polyblend? Why did the plastic manufacturers think of producing it?

Write its usefulness.

19. Draw a labelled diagram of the reproductive system in a human female.

20. Branching decent and natural selection are the two key concepts of Darwinian

Theory of Evolution. Explain each concept with the help of a suitable example.

21. Scientists have succeeded in recovering healthy sugarcane plants from a

diseased one.

(a) Name the part of the plant used as explant by the scientists.

(b) Describe the procedure the scienctists followed to recover the healthy plants.

(c) Name this technology used for crop improvement.

22. (i) Name the enzyme that catalyses the transcription of hnRNA.

(ii) Why does the hnRNA need to undergo changes? List the changes hnRNA

undergoes and where in the cell such changes take place.

23.Study the diagram showing replication of HIV in humans and answer the

following questions accordingly:

(I) Write the chemical nature of the coat 'A'.

(ii) Name the enzyme 'B' acting on 'X' to produce molecule 'C'. Name 'C'.

(iii) Mention the name of the host cell 'D' the HIV attacks first when it enters into

the human body.

(iv) Name the two different cells the new viruses 'E' subsequently attack.

24. Name the genus to which baculoviruses belong. Describe their role in the

integrated pest management programmes.

25. Answer the following questions based on Meselson and Stahi's experiment:

(a) Write the name of the chemical substance used as a source of nitrogen in the

experiment by them.

(b) Why did the scientists synthesise the light and the heavy DNA molecules in the

organism used in the experiment?

(c) How did the scientists make it possible to distinguish the heavy DNA molecule

from the light DNA molecule? Explain.

(d) Write the conclusion the scientists arrive at after completing the experiment.

26. Water is very essential for life. Write any three features both for plants and

animals which enable them to survive in water scarce environment.

OR

How do organisms cope with stressful external environmental conditions which

are localised or of short duration?

27. (i) State the consequence if the electrostatic precipitator of a thermal plant fails

to function.

(ii) Mention any four methods by which the vehicular air pollution can be

controlled.

SECTION-D

28. Give reasons why:

(i) most zygotes in angiosperms divide only after certain amount of endosperm is

formed.

(ii) groundnut seeds are exalnuminous and castor seeds are albuminous.

(iii) Micropyle remains as a small pore in the seed coat of a seed.

(iv) integuments of an ovule harden and the water content is highly reduced, as the

seed matures.

(v) apple and cashew are not called true fruits.

OR

(a) Draw a labelled diagram of L.S. Of 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.

29. (a) State the arrangement of different genes that in bacteria is referred to as

'operon'.

(b) Draw a schematic labelled illustration of lac operon in a 'switched on' state.

(c) Describe the role of lactose in lac operon.

OR

(a) A true breeding homozygous pea plant with green pods and axial flowers as

dominant characters, is crossed with a recessive homozygous pea plant with

yellow pods and terminal flowers. Work out the cross upto F2 generation giving

the phenotypic ratios of F1 and F2 generation respectively.

(b) State the Mendelian principle which can be derived from such a cross and not

from monohybrid cross.

30. (i) Describe the characteristics a cloning vector must possess.

(ii) Why DNA cannot pass through the cell membrane? Explain how is a bacterial

cell made 'competent' to take up recombinant DNA from the medium.

OR

If a desired gene is identified in an organism for some experiments, explain the

process of the following:

(i) Cutting this desired gene at specific location

(ii) Synthesis of multiple copies of this desired gene.