CBSE Board Class 12 Biology Previous Year Question Papers 2010

BIOLOGY (Theory)
class 12
previous paper 2010
Time allowed : 3 hours Maximum Marks : 70

General Instructions :
(i) This question paper consists of four sections  A, B, C and  D. Section  A contains
5  questions of one mark each, Section  B is of  10 questions of  two marks each,
Section  C is of  10 questions of  three marks each and Section  D is of  3 questions
of  five marks each.
(ii) All questions are compulsory.
(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 one question of  5 marks weightage.
Attempt only one of the choices in such questions.
(iv) Question numbers  1 to  5 are to be answered in  one word or  one sentence each.
(v) Question numbers  6 to  15 are to be answered in approximately  20-30 words each.
(vi) Question numbers  16 to  25 are to be answered in approximately  30-50 words each.
(vii) Question numbers  26 to  28 are to be answered in approximately  80-120 words
each.
SECTION A
1. What is the function of secretin ? 1

2. Name any two threatened animal species of India. 1

3. How is nastic movement different from tropic movement ? 1

4. What would happen to the rate of photosynthesis in C 3 plants if the CO 2  concentration level almost doubles from its present level in the atmosphere ? 1

5. Name the disease in humans where the myelin sheath of nerve cells is attacked by the
antibodies of self. 1

SECTION B
6. Due to uncontrolled excessive hunting the population of tigers in a forest becomes zero.
Discuss the long-term effects of this situation on the population of deer in that forest. 2

7. Can all the four chambers of the human heart experience systole simultaneously?
Explain justifying your answer. 2
OR
What do you call the circulatory fluid in the body of cockroach ? Mention its three
functions.3

8. What is the importance of  F 0 — F 1 particles in ATP production during aerobic respiration ? 2

9. What usually can cause oversecretion of parathormone in human body ? List any two
effects on the body because of this oversecretion. 2

10. Where do PGA and glycine gain entry respectively after being formed during
photorespiration in plants ? What happens to them immediately after ? 2

11. Name the hormone that acts as an antagonist to abscisic acid. From which
micro-organism was it extracted initially ? List two bioassays of this growth hormone. 2

12. Explain CO 2 compensation point. 2 CO2

13. Name the two middle horizons of soil profile of tropical rain forests, and mention their
characteristics. 2

14. Why did scientists pick hydrogen as the basis for MRI scanning ? Name two parts of the
human body that do not appear in an MRI scan. 2

15. Define birth rate. Differentiate between crude birth rate and crude death rate. 2

SECTION C
16. Explain the initiation of muscle contraction. What is the role of Sarcoplasmic Reticulum,
Myosin head and F-Actin during contraction in striated muscles ? 3

17. What is meant by ozone shield ? Name two gases that can cause damage to this shield.
Give one harmful effect of this damage each on plants and animals. 3

18. Why is sub-culturing essential in plant tissue culture ? 3
OR
Explain the process of heterosis. How is it different from inbreeding depression?

19. Define the following and give their values in a normal human adult : 3
(i) Tidal volume
(ii) Expiratory reserve volume
(iii) Inspiratory capacity

20. (i) How do grasslands differ from Savannas ?
(ii) Name the two major categories of plant forms that dominate the desert vegetation. 3

21. Define innate immunity. Name and explain the category of barrier which involves
macrophages. 3

22. Why is glomerular filtrate hypertonic and hypotonic in descending and ascending limb of
loop of Henle respectively ? What is the effect of ADH on collecting tubules ? 3

23. Mention where the following are located in the human brain, and give one function of
each : 3
(i) Temporal lobe
(ii) Cerebellum
(iii) Corpus callosum

24. Explain the Capillarity Theory in respect of ascent of water in plants. Name the tissue
involved. 3

25. Distinguish between epimorphic and morphallactic regeneration, giving one example of
each. 3

SECTION D

26. Explain the opening and closing mechanism of stomata. Name the category of plants
which keep their stomata open during the night and closed during the day.                        5
OR
Explain the mechanism of C photosynthetic carbon cycle. Name any two plants where it occurs. Mention the difference in the structure of chloroplasts in the mesophyll cells and bundle sheath cells of such plants.

27. What is the basis of classifying cancer ? Name and explain the different categories of
cancer. Mention any two approaches for cancer treatment. 5
OR
What is embryo culture ? What is the objective of this culture ? Describe the three
applications of this technique.

28. Draw a diagram of the longitudinal section of a mature anatropous ovule and label any
ten parts in it. 5
OR
Draw a flow-chart to show the hormonal control of the human male reproductive
system, highlighting the inhibitory and stimulatory directions in it.