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CBSE Previous Year Question Paper 2013
CBSE Previous Year Question Paper 2013
Set – I (Question)
Time allowed : 3
hours Maximum Marks : 70
General Instructions:
1. All questions are compulsory.
2. This question paper consists of four A,B,C and D. Section A contains 8 questions of one mark each. Section B is of 10 questions of two marks each. Section C is of 9 questions of three marks each and Section D is 3 questions of five marks each.
3. There is no overall choice. However, an internal choice has been provided in one question of 2 marks, one question of 3 marks and two questions of 5 marks weightage. A student has to attempt only one of the atternatives in such questions.
4. Wherever necessary, the diagrams drawn should be neat and properly labelled.
SECTION-A
1.What is a detritus food chain made up of? How do they meet their energy and nutritional requirements?
2.When does a human body elicit an anamnestic response?
3. Name the phenomenon and one bird where the female gamete directly develops into a new organism.
4. State the role of transposons in silencing of mRNA in eukaryotic cells.
5. Why are green algae not likely to be found in the deepest strata of the ocean?
6. State what does 'standing crop' of a tropic level represent.
7.Why is the use of unleaded petrol recommended for motor vehicles equipped with catalytic converters?
8.Name the type of biodiversity represented by the following:
(i)1000 varieties of mangoes of India.
(ii)Variations in terms of potency and concentration of reserpine in Rauwolfia.
SECTION – B
9. In angiosperms, zygote is diploid while primary endosperm cell is triploid.
Explain.
10. What is meant by “alien species” invasion? Name one plant and one animal alien species that are a threat to our Indian native species.
11. List the two main propositions of Oparin and Haldane.
12. Write the events that take place when a vaccine for any disease is introduced into the human body.
OR
Why is a person with cuts and bruises following an accident administered tetanus antitoxin? Give reasons.
13. Differentiate between the two cells enclosed in a mature male gametophyte of an angiosperm.
14. Work out a cross to find the genotype of a tall pea plant. Name the type of cross.
15. Write the Oparin and Haldane's hypothesis about the origin of life on Earth. How does meteorite analysis favour this hypothesis?
16. Why is proinsulin so called? How is insulin different from it?
17. Where would you expect more species biodiversity – in tropics or in polar regions? Give reasons in support of your answer.
18.“It is possible that a species may occupy more than one trophic level in the same ecosystem at the same time”. Explain with the help of one example.
SECTION – C
19.(a) Explain DNA polymorphism as the basis of genetic mapping of human genome.
(b)State the role of VNTR in DNA fingerprinting.
20.Why are human females rarely haemophilic? Explain. How do haemophilic patients suffer?
21.In a maternity clinic, for some reasons the authorities are not able to hand over the two new-borns to their respective real parents. Name and describe the technique that you would suggest to sort out the matter.
22.Explain the increase in the numbers of melanic (dark winged) moths in the urban areas of post-industiralisation period in England.
23.Describe how biogas is generated from activated sludge. List the components of biogas.
24. Name the pest that destroys the cotton bolls. Explain the role of Bacillus thuringiensis in protecting the cotton crop against the pest to increase the yield.
25.(a) Write the importance of measuring the size of a population in a habitat or an ecosystem.
(b) Explain with the help of an example how the percentage cover is a more meaningful measure of population size than mere numbers.
26.Differentiate between two different types of pyramids of biomass with the help of one example of each.
27.(a) Explain “death rate” in a populationby taking a suitable example.
(b) Write the other two characteristics which only a population shows but an individual cannot.
SECTION – D
28.(a) Draw a L.S. of a pistil showing pollen tube entering the embryo-sac in an angiosperm and label any six parts other than stigma, style and ovary.
(b) Write the changes a fertilized ovule undergoes within the ovary in an angiosperm plant.
OR
(a) Draw a diagrammatic sactional view of a human seminiferous tubule, and label Sertoli cells, primary spermatocyte, spermatogonium and spermatozoa in it.
(b) Explain the hormonal regulation of the process of spermatogenesis in humans.
29.(a) Write the conclusion drawn by Griffith at the end of his experiment with Streptococcus pneumoniae.
(b) How did O. Avery, C MacLeod and M.McCarty prove that DNA was the genetic material? Explain.
OR
(a) Explain the mechanism of sex-determination in humans.
(b) Differentiate between male haterogamety and female heterogamety with the help of an example of each.
30. How does the process of natural selection affect Hardy-Weinberg equilibrium? Explain. List the other four factors that disturb the equilibrium.
OR
(a)Explain Mendel's law of independent assortment by taking a suitable example.
(b)How did Morgan show the deviation in inheritance pattern in Drosophila with respect to this law?
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