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(Download) CBSE Class-12 Sample Paper And Marking Scheme 2017-18 : Biology

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(Download) CBSE Class-12 Sample Paper And Marking Scheme 2017-18 : Biology

General Instructions:
1. There are a total of 26 questions and five sections in the question paper. All questions are compulsory.
2. Section A contains question number 1 to 5, Very Short Answer type questions of one mark each.
3. Section B contains question number 6 to 10, Short Answer type I questions of two marks each.
4. Section C contains question number 11 to 22, Short Answer type II questions of three marks each.
5. Section D contains question number 23, Value Based Question of four marks.
6. Section E contains question number 24 to 26, Long Answer type questions of five marks each.
7. 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. A tissue, of a tobacco plant, infected with TMV was used to obtain a new plant. Identify the technique used and reason out the possibility of obtaining a new healthy plant. 1
2. State a method of cellular defense which works in all eukaryotic organisms 1
3. In case of an infertile couple, the male partner can inseminate normally but the mobility of sperms is below 40 percent. Which kind of ART is suitable in this situation to form an embryo in the laboratory conditions, without involving a donor? 1
4. Write the two components of the first artificial recombinant DNA molecule constructed by Cohen and Boyer.1
5. A cross was carried out between two pea plants showing the contrasting traits of height of the plant. The result of the cross showed 50% of parental characters. Name the type of cross. 1

Section B

6. The alarming population growth is leading to scarcity of basic requirements. Suggest with reasons, any two population control measures other than contraception to address the situation.

7. During a cytological study conducted on the chromosomes of the insects, it was observed that only 50% of the sperms had a specific structure after spermatogenesis. Name the structure and write its significance in sex determination of insects.2
8. To reduce the percentage of population suffering from hunger and malnutrition, microbes are grown on a large scale to act as food supplements. Mention any two microbes used as food supplement and suggest their role.
Success rate of artificial insemination in cattle is fairly low. Identify any other technique to improve the successful production of hybrids. State two advantages of this technique. 2
9. (a) A patient who had an organ transplant was given cyclosporin– A. Mention the microbial source and state the reason for administration of this bioactive molecule.
(b) Bottled fruit juices bought from the market are clearer as compared to those made at home. Give reason. 2
10. Evaluate the effect of loss of biodiversity in a region. Mention any four such effects. 2

Section C

11. Draw the diagram of microsporangium of an Angiosperm and label any four parts State the function of its innermost wall layer. 3
12. Give reason : -
(a) A liverwort plant is unable to complete its life cycle in a dry environment.
(b) Number of male gametes produced is much more than the female gametes produced.
(c) Organisms exhibiting external fertilization show great synchrony between the sexes and release a large number of gametes into surrounding medium. 3
13. (a) Name the different gases contained in the flask used as an experimental setup by S.L. Miller.
(b) On the basis of composition of gases in this experiment, what was the condition in the flask?
(c) Write the conclusion drawn from this experiment. 3
14. When a snapdragon plant bearing pink colour flower was selfed, it was found that, 69 plants were having red coloured flowers. What would be the number of plants bearing pink flower and white flower. Show with the help of Punnett square. Identity the principle of inheritance involved in this experiment

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