KENDRIYA VIDYALAYA SANGATHAN ERNAKULAM REGION FIRST COMMON PRE-BOARD EXAMINATION 2014-15 CLASS XII BIOLOGY (THEORY) SET A TIME ALLOWED-3 HOURS MAXIMUM MARKS : 70 1. All questions are compulsory. 2. This question paper consists of five sections A,B,C,D and E 3. Section A contains 5 questions of one mark each and Section B contains 5 questions of two marks each and Section C contains 12 questions of three marks each,section D contains 1 question of four marks and it is a value based Question and Section E contains 3 questions of five marks each. 4. There is no overall choice. However, an internal choice is provided in one question of 2 marks weightage, one question of three marks weightage and all three questions of 5 marks weightage. 5. Wherever necessary,diagrams drawn should be neat and properly labeled SECTION A (1 MARK EACH) 1. Do Eukaryotic cells have restriction endonucleases. Justify your answer. 2. How does saliva and tear help to prevent bacterial infection? 3. Write the Central Dogma of Molecular Biology as proposed by Crick. 4. What do you technically call the water that you drink and kernel that you eat in a tender Coconut? 5. What is pleiotropy?
SECTION B (2 MARKS EACH) 6. Give the chromosome number in the gametes of the following organisms, if the number of chromosomes in their meiocytes is as follows. (i)dog-78 (ii) Housefly -12 (iii) Butterfly 380 (iv) Ophioglossum 1260. 7. Give reason : (a) Bottled fruit juices bought from the market are clearer as compared to those made at home. (b) large holes are found o in swiss cheese. 8. What are the differences between aquaculture and pisciculture? 9. Why is Agrobacterium mediated genetic transformation described as natural genetic engineering in plants? 10. Classify the following into chromosomal and mendelian disorders. (a) Cystic fibrosis. (b) Klinefelter s Syndrome. (c) Haemophilia. (d) Turner s Syndrome. If the sequence of the coding strand in a transcription unit is written as follows: 5 - ATGCATGCATGCATGCATGCATGCATGCATGC-3 Write down the sequence of the template strand and the mrna SECTION C ( 3 MARKS EACH) 11. Name and explain the Kind of interaction in the following. (a) Algae and Fungi in lichens. (b) Head-louse and humans. (c)hermit crab and sea-anemone. 12. IARI has released several varietites of crop plants that are biofortified. Give three examples of such crops and their biofortifications. 13. In a family, each of the four children has a different blood group. the mother is Group A and the father is Group B. Explain the pattern of inheritance along with the genotype. 14. How does CuT act as an effective contraceptive for human females?
15. A person is suffering from Ascariasis. Mention the pathogen causing the disease and an organ of the body affected,three symptoms and one mode of transmission of the disease. A person is suffering from Chikungunya. Mention the pathogen causing the disease,an organ of the body affected,three symptoms and the mode of transmission of the disease. 16. Explain the steps involved in the separation and isolation of DNA fragments through agarose gel electrophoresis. 17. What are (a)spermatogenesis. (b) Spermiogenesis and (c) Spermiation. 18. How does Industrial Melanism support Darwin s theory of natural selection? 19. Name the pioneer species on a bare rock. How do they help in establishing the next type of vegetation. Mention the type of Climax community that will ultimately get established. 20. Give three hypothesis for explaining why tropics show greatest levels of species richness. 21. (a) Baculoviruses are excellent candidates for integrated pest management in an ecologically sensistive area. Explain giving two reasons. (b) Why do organic farmers do not recommend eradication of insect pests? 22. The length of a DNA molecule in a typical mammalian cell is calculated to be approximately 2.2 m. How is the packing of this long molecule done to accommodate it within the nucleus of the cell? SECTION D (VALUE BASED QUESTION) -4 MARKS. 23. Bioethics can be regarded as a set of standards that may be used to regulate our activities in relation to Biological research. Since Biotechnology,especially r DNA technology aims at exploiting the biological world for human use,it is branded as unnatural and unethical etc. (a) Mention some bioethical concerns (or)values that have been neglected. (b) How will you convince people that biotechnology is beneficial and not to be treated as unethical or unacceptable?
SECTION E ( 5 MARKS EACH) 24. (a) Why are catalytic converters recommended for vehicles? (b) Why should vehicles use only unleaded petrol? (c)why is CNG preferred to diesel as fuel in a vehicle? (d) How does electrostatic precipitator work to remove pollutants? (a) What is the relation between dissolved oxygen and biochemical oxygen demand? (b) Mention their effects on aquatic life in the river. (c) What are algal blooms? How are they formed? 25.What did Messelson and Stahl observe when: They cultured E.coli in a medium containing 15 NH 4 Cl for a few generations and centrifuged the contents, they transferred one such bacterium to the normal medium of NH 4 Cl and cultured for two generations. What did Messelson and Stahl conclude from the experiment? Explain with the help of diagrams. Explain the third largest genome sequencing project undertaken after human and mouse genomes. Give the salient features (any four) of this project 26. Explain with the help of diagrams,the development of a mature embryo sac from the megaspore mother cell in an angiosperm. Describe the post-zygotic events leading to implantation and placenta formation in humans. Mention any two functions of placenta.