CBSE Question Paper 2015 class 12 Biology

General Instructions:

• There are total of 26 questions and five sections in the question paper. All questions are compulsory.
• A contains question number 1 to 5 Very Short Answer type questions of one mark each.
• B contains question number 6 to 10 Short Answer type I questions of two marks each.
• C contains question number 11 to 22 Short Answer type II questions of three marks each.
• D contains question number 23, Value Based Question of four marks.
• E contains question number 24 to 26 Long Answer type questions of five marks each.
• There is no overall choice in the question paper, however, an internal choice is provided in one question of two marks, one question of three marks and all three questions of five marks. An examinee is to attempt any one of the questions out of the two given in the question paper with the same question number.

SECTION A

1. Name the vegetative propagules in the following angiosperms:

(a) Agave (b) Bryophyllum

2. Name any two diseases the Himgiri variety of wheat is resistant to.

3. How can bacterial DNA be released from bacterial cell for biotechnology experiments?

4. State ‘Gause’s Competitive Exclusion Principle’.

5. BOD of two samples of water A and B were 120mg/L and 400mg/L respectively. Which sample is more polluted?

SECTION B

6. State the dual role of deoxyribonucleoside triphosphates during DNA replication.

 7. (a) State the difference between meiocyte and gamete with respect to chromosome number.

(b) Why is whiptail lizard referred to as parthenogenetic?

OR

Where is sporopollenin present in plants? State its significance with reference to its chemical nature?

8. Why is pyramid of energy always upright? Explain.

9. (a) Explain the property that prevents normal cells from becoming cancerous.

(b) All normal cells have inherent characteristic of becoming cancerous. Explain.

10. What is divergent evolution? Explain taking an example from plants.

SECTION: C

11. What is inbreeding depression and how it is caused in organisms? Write any two advantages of inbreeding.

12. If there is a history of haemophilia in the family, the chances of male members becoming haemophilic are more than that of the female.

(a) Why is it so? Explain.

(b) Write the symptoms of the disease.

13.

(a) Name the molecule ‘M’ that binds with the operator.

(b) Mention the consequences of the such binding.

(c) What will prevent the binding of the molecule “M’ with the operator gene? Mention the event that follows:

(d) Which one of the structural genes codes for – galactosidase?

14. (a) Expand IUD.

(b) How do copper and harmone releasing IUDs act as contraceptives? Explain.

15. Using Punnett square demonstrate the law of independent assortment in a dihybrid cross involving two heterozygons parents. State the law.

16. Explain any three advantages of seeds offer to angiosperms

17. EcoRI is used cut a segment of foreign DNA and that a vector DNA to form a recombinant DNA. Show with the help of schematic diagrams.

(i) The set of palindromic nucleotide sequence of base pairs the EcoRI will recognize in both the DNA segments. Mark the site at which EcoRI will act and cut both the segments.

(ii) Sticky ends formed on both the segments, Where the DNA segments will join later to form recombinant DNA.

OR

Name the insect pest that is killed by the products of cry IAc gene. Explain how the gene makes the plans resistant to the insect pest.

18. Name a genus to which baculoviruses belong. Describe their role in integrated pest management.

19. Explain mutualism with the help of any two example. How it is different from commenalism?

20. (a) Name a molecular diagnostic technique to detect the presence of pathogen in its early stage of infection.

(b) Describe gene therapy procedure for an ADA- deficient patient.

21. Give three hypotheses for explaining why tropics show greatest levels of species richness?

22. (a) Describe the characteristics of a cloning vector must possess.

(b) What is biopiracy?

SECTION D

23. An active member of an awareness group conducts regular programmes to sensitive public against alcoholism amongst youth – a serious health hazard in his locality.
(i) Why is alcoholism a serious issue?
(ii) How can this member sensitive the public?
(iii) Identify the values this member is trying to propogate amongst the people in his locality.

SECTION E

24. (a) Write the specific location and functions of the following cells in human males:

(i) Leydig cells (ii) Sertoli cells (iii) Primary spermatocyte

(b) Explain the role of any two accessory glands in human male reproductive system.

OR

Describe in sequence the events that lead to the development of a 3-celled pollen grains from microspore mother cell in angiosperms.

25. (a) Explain the interpretation of Charles Darwin when he observed a variety of small birds on Galapagos Islands.
(b) Explain the three different ways the natural selection can affect the frequency of a heritable trait in a population in the graph given below.

OR

(a) Describe the various steps of Griffith’s experiment that lead to the conclusion of the ‘Transforming Principle’.
(b) How did the biochemical nature of the ‘Transforming Principle’ get established?

26. (a) Name the green-house gases. How do they affect the life on Earth.

(b) Describe the couses of eutrophication of a take.

OR

(a) Trace the succession of plants on a dry bare rock.

(b) How does phosphorus cycle differ from carbon cycle?

Last Year Question Paper Class 12 Biology 2015

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