CBSE Board Class 12 Biology Previous Year Question Papers 2005

PREVIOUS YEAR PAPER
BIOLOGY (Theory) 2005

CLASS-12
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 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

2. In humans, starch digestion begins in the buccal cavity but stops in the stomach. Why ? 1

3. Name the two most biodiversity-rich zones of India. 1

4. Name the hormone that makes the plants more tolerant to various stresses. 1

5. Name the two major groups of cells required in attaining specific immunity. 1

SECTION B

6. Name the end products of aerobic and anaerobic glycolysis. List two ways by which
molecules of ATP are produced in glycolysis during aerobic respiration in a cell. 2

7. Differentiate between Total Fertility Rate (TFR) and Replacement Level (RL). 3 s

8. 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

9. Name the source gland of leutinising hormone (LH). Mention the other hormone along
with which it acts on its target cells/organ. Give their two functions. 2

10. 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.

11. 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

12. What is thermal stratification ? How does thermal stratification in temperate lakes help
in rich growth of phytoplankton during autumn and spring turn-over? 2

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

14. What is meant by bioassay ? Name the two bioassays that are used to examine auxin
activity in plants. 2

15. Explain CO 2
compensation point. 2 CO2

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

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

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

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

20. 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

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

22. Where and how is urea produced in ureotelic animals ? What happens to the kidney
filtrate in descending loop of Henle and collecting tubules in humans ? 3

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

24. 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

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

SECTION D

26. 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.

27. 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.

28. Explain the process of biosynthetic phase of photosynthesis occurring in the chloroplast. 5
OR
Describe the process of development of root nodules in a leguminous plant. Name the
oxygen scavenger molecule present in the root nodules.