CBSE Board Class 12 Biology Previous Year Question Papers 2009

BIOLOGY (Theory) 
class 12 2009
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. Give one function of aerenchyma in aquatic plants. 1

2. What is threshold stimulus for a nerve cell ? 1

3. How can you revert a freshly plasmolysed plant cell to its normal state ? 1

4. What are psychoactive drugs ? 1

5. List two characters of pollen grains that favour anemophily in plants. 1

SECTION B
6. If you breathe over the surface of a leaf repeatedly in quick succession, what will happen
to the stomata of the leaf ? Explain giving reasons. 2

7. Explain a Synovial joint. 2

8. What is keystone species ? Mention any one function performed by it in a community.         2
OR
How  do  tropical  deciduous  forests  change  in  appearance   during rainy  and   summer
seasons ? Name two dominant species of such forests in India.

9. As per ‘wear and tear’ theory of ageing, list two factors that can cause damage to cellular
DNA. Explain any two consequences of this damage. 2

10. Define (i) total fertility rate and (ii) replacement level in population. 2

11. Name any one of the three scientists associated with glycolysis. Where does this process
occur in a cell ? List two ways in which this process helps in ATP production during
aerobic respiration. 2

12. Name the two pathways through which water moves in the roots. Explain any one of
them. 2

13. What is electroencephalography ? What do alpha and theta waves represent in an EEG ? 2

14. What are induced mutations ? Give one example each of physical and chemical mutagens. 2

15. What is IUCN Red List ? Give any two uses of this list. 2

SECTION C
16. What is the difference between biochemical oxygen demand (BOD) and chemical oxygen
demand (COD) ? What is the effect of a higher BOD on the level of dissolved oxygen and
sensitive organisms in a water body ? 3

17. What is the role of ostia, alary muscles and head sinus in the process of blood circulation
in cockroach ? 3

18. How are autoimmune diseases different from immuno-deficiency diseases ? Give one
example of each in humans. 3

19. Explain the role of oxygen, F 0 -F 1
particles and NADH 2
in oxidative phosphorylation. 3

20. Give one functional role each of Retinol, Calciferol and Tocopherol in the human body.
Name the deficiency diseases associated with each one of these.                                          3
OR
What is cerebrospinal fluid ? Explain any four of its functions.

21. Describe the three major steps of spermatogenesis in humans. 3

22. What is a biopatent ? List any four items for which biopatents are awarded. 3

23. Give four causes of deforestation. How does deforestation contribute to global warming ? 3

24. Explain how cancer spreads from its first location in the human body. List any two
therapeutic strategies used for the treatment of cancer. 3

25. Name the hormones and their source gland cells, which are involved in the regulation of
blood glucose level in humans. Explain how they act antagonistically. 3

SECTION D
26. Mention any four advantages of vegetative reproduction in plants. Explain any two types
of artificial methods of vegetative reproduction.                                                                  5
OR
What is photoperiodism ? Explain the different categories of plants on the basis of
photoperiodism giving one example of each category.

27. Draw a labelled diagram of the human urinary system along with the associated main
blood vessels.                                                                                                                
   5
OR
Draw   a   labelled   diagram   of  the   T.S.   of  spinal   cord   along   with   the   schematic
representation of the nerve pathway in the knee-jerk reflex arc.

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.