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Board Paper of Class 12-Science 2008 Biology All India(SET 1) - 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

    Name any two vertebrate body parts that are homologous to human forelimbs.

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  • Question 2

    When and why do some animals like snails go into aestivation?

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  • Question 3

    What is the economic value of Spirulina?

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  • Question 4

    What was the speciality of the milk produced by the transgenic cow Rosie?

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  • Question 5

    How do neutrophils act as a cellular barrier to pathogens in humans?

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  • Question 6

    Mention the polarity of the DNA strands a-b and c-d shown in the replicating fork given below.

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  • Question 7

    Mention any two significant roles predation plays in nature.

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  • Question 8

    Why is the polar region not a suitable habitat for tiny humming birds?

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  • Question 9

    (a) Expand IUD.

    (b) Why is hormone releasing IUD considered a good contraceptive to space children?

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  • Question 10

    Name the interaction in each of the following:

    (a) Cuscuta growing on a shoe flower plant

    (b) Mycorrhiza living on the roots of higher plants

    (c) Clown fish living among the tentacles of sea anemone

    (d) Koel laying her eggs in crow’s nest

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  • Question 11

    A plant of Antirrhinum majus with red flowers was crossed with another plant of the same species with white flowers. The plants of the F1 generation bore pink flowers. Explain the pattern of inheritance with the help of a cross.

    OR

    A woman with blood group O married a man with AB group. Show the possible blood groups of the progeny. List the alleles involved in this inheritance.

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  • Question 12

    Why do sportspersons often fall a victim to cocaine addiction?

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  • Question 13

    State the difference between the first trophic level of detritus food chain and grazing food chain.

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  • Question 14

    Coconut palm is monoecious while date palm is dioecious. Why are they called so?

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  • Question 15

    How can DNA segments, separated by gel electrophoresis, be visualised and isolated?

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  • Question 16

    How do Darwin’s finches illustrate adaptive radiation?

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  • Question 17

    Name the blank spaces a, b, c, and d from the table given below:

    Type of microbe

    Scientific name

    Commercial product

    Bacterium

    a

    Lactic acid

    Fungus

    b

    Cyclosporine A

    c

    Monascus purpureus

    Statin

    Fungus

    Penicillium notatum

    d

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  • Question 18

    DDT content in the water of a lake that supplies drinking water to the nearby villages is found to be 0.003 ppm. The kingfishers of that area are reported to have 3 ppm of DDT. Why has the concentration increased in these birds? What harm will this cause to the bird population? Name the phenomenon.

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  • Question 19

    (a)

    Read the graph given above and correlate the uterine events that take place according to the hormonal levels on

    (i) 6 − 15 days

    (ii) 16 − 25 days

    (iii) 26 − 28 days (if the ovum is not fertilised)

    (b) Specify the sources of the hormones mentioned in the graph.

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  • Question 20

    Explain the role of baculoviruses as biological control agents. Mention their importance in organic farming.

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  • Question 21

    (a) Draw the structure of the initiator tRNA adaptor molecule.

    (b) Why is tRNA called an adaptor molecule?

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  • Question 22

    Study the population growth curves shown above.

    (i) Identify curves ‘a’ and ‘b’.

    (ii) Mention the conditions responsible for the curves ‘a’ and ‘b’ respectively.

    (iii) Give the necessary equation of the curve ‘b’.

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  • Question 23

    Why is Agrobacterium tumefaciens a good cloning vector? Explain.

    OR

    Explain the importance of (a) ori (b) ampR and (c) rop in the E. coli vector shown below:

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  • Question 24

    Study the mRNA segment given above which is complete to be translated into a polypeptide chain.

    (i) Write the codons ‘a’ and ‘b’.

    (ii) What do they code for?

    (iii) How is peptide bond formed between two amino acids in the ribosome?

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  • Question 25

    (a) Name the infective stage of Plasmodium which Anopheles mosquito takes in along with the blood meal from an infected human.

    (b) Why does the infection cause fever in humans?

    (c) Give a flow chart of the part of the life-cycle of this parasite passed in the insect.

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  • Question 26

    A factory drains its waste water into the nearby lake. It has caused algal bloom.

    (a) How was the algal bloom caused?

    (b) What would be the consequences?

    (c) Name the phenomenon that caused it.

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  • Question 27

    Study the given pedigree chart and answer the questions that follow.

    (a) Is the trait recessive or dominant?

    (b) Is the trait sex-linked or autosomal?

    (c) Give the genotypes of the parents in generation I and of their third and fourth child in generation II.

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  • Question 28

    (a) Draw a schematic labelled diagram of a fertilised embryo sac of an Angiosperm.

    (b) Describe the stages in embryo development in a dicot plant.

    OR

    (a) Draw a labelled diagram of a sectional view of human seminiferous tubule.

    (b) Differentiate between gametogenesis in human males and females on the basis of:

    (i) Time of initiation of the process

    (ii) Products formed at the end of the process

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  • Question 29

    Explain the steps involved in the production of genetically engineered insulin.

    OR

    (a) Name the nematode that infests and damages tobacco roots.

    (b) How are transgenic tobacco plants produced to solve this problem?

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  • Question 30

    What is ‘semi-conservative’ DNA replication? How was it experimentally proved and by whom?

    OR

    A homozygous tall pea plant with green seeds is crossed with a dwarf pea plant with yellow seeds.

    (i) What would be the phenotype and genotype of F1?

    (ii) Work out the phenotypic ratio of F2 generation with the help of a Punnett square.

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