Biology Class XII

You are on questions of Section A,B,C,D

Max Marks : 70

Time allowed : 3 hrs

Section A

Question Nos. 1-8 are of very short answer type carrying 1 mark each only. Answer them in 1-20 words each.

Question 1. What induces parthenocarpy in grapes?

Question 2. What is the term used for the regions of a gene which become part of mRNA and code for the different regions of the proteins?

Question 3. The venous blood in the lung has a PCO₂ of 46 mm Hg. Should the alveolar PCO₂ exceed or be less than 46 mm Hg to result in diffusion of CO₂ from the blood into the alveolus?

Question 4. Which part of the plant leaf is modified to form spines of Acacia and the sheath covering the leaf of Ficus elastica.

Question 5. Name the enzyme that can break and reseal one strand of DNA.

Question 6. What does the J-shaped growth curve of a population indicate?

Question 7. What forms the cambial ring in a dicot stem during the secondary growth?

Question 8. Name the principal mineral anion in the extracellular fluid.

Section B

Question Nos. 9 – 18 are short answer questions carrying 2 marks each. It is appropriate to answer them in about 20 – 30 words.

Question 9. A mother with O type blood group has conceived. The expected blood group of the foetus is B. Will there be any problems to the mother or the foetus? If so, specify the problems?

Question 10. What are the two types of fibres of the connective tissue? Differentiate between the two.

Question 11. A farmer observed drops of water along the margins of leaves of tomato plants growing in his well-irrigated field on a winter morning. Give reasons for this occurrence. Why had the water drops appeared only along the leaf margins?

Question 12. Give the scientific name of modern wheat. Why is it quoted as a typical example of rapid speciation?

Question 13. Name any two of cyanobacteria and explain how they serve as main sources of bio-fertilisers.

Question 14. What are the two striking observations when different stages of embryos of different classes of vertebrates are studied comparatively? How does this study support evolution?

Question 15. (I) An animal should possess at least one out of the three possible characteristics to enable it to function as a ureotelic organism. List these characteristics.

(II) Which among the following is / are ureotelic animals : Whale, camel, toad, shark.

Question 16. Pick out the plant with whorled arrangement of leaves from the list given below and say why it is categorised so : Neem; Nerium; Nepenthes.

Question 17. How is elongation carried on during protein synthesis in a cell?

Question 18. What category of pathogens causes poliomyelitis? How is crippling caused in the victim of this disease? How can this disease be prevented?