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Board Paper of Class 12-Science 2013 Biology (SET 3) - Solutions

General Instructions:
(i) All questions are compulsory.
(ii) This question paper consists of four Sections 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 of 3 questions of five marks each.
(iii) 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 alternatives in such questions.
(iv) Wherever necessary, the diagrams drawn should be neat and properly labelled.
  • Question 1

    Why is the enzyme cellulase needed for isolating genetic material from plant cells and not form the animal cells? (1)

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  • Question 3

    An anther with malfunctioning tapetum often fails to produce viable male gametophytes. Give any one reason. (1)

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  • Question 4

    Why sharing of injection needles between two individuals is not recommended? (1)

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  • Question 5

    Name the enzyme and state its property that is responsible for continuous and discontinuous replication of the two strands of a DNA molecule. (1)

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  • Question 6

    “Sweet potato tubers and potato tubers are the result of convergent evolution.” Justify the statement. (1)

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  • Question 7

    Write the equation that helps in deriving the net primary productivity of an ecosystem. (1)

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  • Question 8

    Name the type biodiversity represented by the following: (1)

    (a) 50,000 different strains of rice in India.

    (b) Estuaries and alpine meadows in India

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  • Question 9

    Explain why very small animals are rarely found in polar region. (2)

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  • Question 10

    Why the pyramid of energy is always upright? Explain. (2)

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  • Question 11

    Expand the following and mention one application of each:

    (i) PCR

    (ii) ELISA

    OR

    (a) Mention the difference in the mode of action of exonuclease and endonuclease.

    (b) How does restriction endonuclease function? (2)

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  • Question 12

    Name any two sources of e-Wastes and write two difference ways of their disposal. (2)

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  • Question 13

    Explain the steps that ensure cross pollination in an autogamous flower. (2)

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  • Question 14

    When and where do chorionic villi appear in humans? State their function. (2)

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  • Question 15

    In a cross between two tall pea plants some of the offsprings produced were dwarf. Show with the help of Punett square how this is possible. (2)

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  • Question 16

    A student on a school picnic to park on a windy day started sneezing and having difficulty in breathing in reaching the park. The teacher enquired whether the student was allergic to something.

    (a) What is an allergy?

    (b) Write the two unique characteristics of the system involved in the response observed in the student. (2)

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  • Question 17

    Why and how bacteria can be made ‘competent’? (2)

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  • Question 18

    (a) Name the deficiency for which first clinical gene therapy was given.

    (b) Mention the cause of and one cure for this deficiency. (2)

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  • Question 19

    (a) Why is human ABO blood group gene considered a good example of multiple alleles?

    (b) Work out a cross up to F1 generation only, between a mother with blood group A (Homozygous) and the father with blood group B (Homozygous). Explain the pattern of inheritance exhibited. (3)

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  • Question 20

    Describe the structure of RNA polynucleotide chain having four different types of nucleotides. (3)

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  • Question 21

    (a) Differentiate between inbreeding and outbreeding.

    (b) Explain inbreeding depression and how it can be overcome.

    (c) Mention two advantages of inbreeding programme in cattle. (3)

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  • Question 22

    (a) Why are the fruit juices bought from market clearer as compared to those made at home?

    (b) Name the bioactive molecules produced by Trichoderma polysporum and Monascus purpureus. (3)

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  • Question 23

    Draw the following diagrams related to human reproduction and label them.

    (a) The zygote after the first cleavage division

    (b) Morula stage

    (c) Blastocyst stage (sectional view) (3)

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  • Question 24

    With the help of any two suitable examples explain the effect of anthropogenic actions on organic evolution. (3)

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  • Question 25

    How have human activities caused desertification? Explain.

    OR

    How does algal bloom destroy the quality of a fresh water body? Explain. (3)

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  • Question 26

    Explain mutualism with the help of any two examples. How is it different from commensalism? (3)

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  • Question 27

    (a) Why a transgenic animals so called?

    (b) Explain the role of transgenic animals in (i) Vaccine safety and (ii) Biological products with the help of an example each. (3)

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  • Question 28

    A child suffering from Thalassemia is born to a normal couple. But the mother is being blamed by the family for delivering a sick baby. (5)

    (a) What is Thalassemia?

    (b) How would you counsel the family not to blame the mother for delivering a child suffering from this disease? Explain.

    (c) List the values your counselling can propagate in the families.

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  • Question 29

    Draw a diagram of a mature embryo sac of an angiosperm and label the following parts in it.

    (i) Filiform apparatus

    (ii) Synergids

    (iii) Central cell

    (iv) Egg cell

    (v) Polar nuclei

    (vi) Antopodals

    (b) Write the fate of egg cell and polar nuclei after fertilization.

    OR

    (a) Describe the events of Oogenesis with the help of schematic representation.

    (b) Write two differences between Oogensis and spermatogenesis.

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  • Question 30

    Describe the asexual and sexual phases of life cycle of Plasmodium that causes malaria in humans. (5)

    OR

    (a) What is plant breeding? List the two steps the classical plant breeding involves.

    (b) How has the mutation breeding helped in improving crop varieties? Give one example where this technique has helped.

    (c) How has the breeding programme helped in improving the public nutritional health? State two examples in support of your answer.

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