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Board Paper of Class 12-Science 2012 Biology Delhi(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

    Mention the difference between spermiogenesis and spermiation. (1)

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  • Question 2

    A garden pea plant (A) produced inflated yellow pod, and another plant (B) of the same species produced constricted green pods. Identify the dominant traits. (1)

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  • Question 3

    What is an interaction called when an orchid grows on a mango plant?

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  • Question 4

    Write the names of the semi-dwarf and high yielding rice varieties developed in India after 1966.

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  • Question 5

    Write what do phytophagous insects feed on. (1)

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  • Question 6

    Mention the unique feature with respect to flowering and fruiting in bamboo species. (1)

     

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  • Question 7

    How does smoking tobacco in human lead to oxygen deficiency in their body? (1)

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  • Question 8

    State the significance of biochemical similarities among diverse organisms in evolution? (1)

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  • Question 9

    Explain the work carried out by Cohen and Boyer that contributed immensely in biotechnology. (2)

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  • Question 10

    (a) State the difference between meiocyte and gamete with respect to chromosome number.

    (b) Why is a whiptail lizard referred to as parthenogenetic? (2)

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  • Question 11

    Draw a neat labeled sketch of a replicating fork of DNA. (2)

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  • Question 12

    Some organisms suspend their metabolic activities to survive in unfavourable conditions. Explain with the help of any four examples. (2)

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  • Question 13

    (a) State the role of DNA ligase in biotechnology.

    (b) What happens when Meloidegyne incognitia consumes cells with RNAi gene? (2)

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  • Question 14

    Where is sporopollenin present in plants? State its significance with reference to its chemical nature. (2)

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  • Question 15

    Mention the importance of Lactic acid bacteria to humans other than setting milk into curd. (2)

    OR

    How do methanogens help in producing biogas?

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  • Question 16

    (a) Name the Protozoan parasite that causes amoebic dysentery in humans.

    (b) Mention two diagnostic symptoms of the disease.

    (c) How is this disease transmitted to others? (2)

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  • Question 17

    (a) Highlight the role of thymus as a lymphoid organ.

    (b) Name the cells that are released from the above mentioned gland. Mention how they help in immunity. (2)

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  • Question 18

    Why do clown fish and sea anemone pair up? What is this relationship called? (2)

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  • Question 19

    (a) Construct a complete transcription unit with promoter and terminator on the basis of the hypothetical template strand given below:

    (b) Write the RNA strand transcribed from the above transcription unit along with its polarity.

    OR

    How are the structural genes inactivated in lac operon in E. coli? Explain

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  • Question 20

    Write the function of each of the following: (3)

    (a) Seminal vesicle

    (b) Scutellum

    (c) Acrosome of human sperm.

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  • Question 21

    Study a part of the life cycle of malarial parasite given below. Answer the questions that follow: (3)

    (a) Mention the roles of ‘A’ in the life cycle of the malarial parasite.

    (b) Name the event ‘C’ and the organ where this event occurs.

    (c) Identify the organ ‘B’ and name the cells being released from it.

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  • Question 22

    Draw a schematic sketch of pBR 322 plasmid and label the following in it: (3)

    (a) Any two restriction sites.

    (b) Ori and rop genes.

    (c) An antibiotic resistant gene.

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  • Question 23

    State the theory of Biogenesis. How does Miller’s experiment support this theory? (3)

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  • Question 24

    Given below is the representation of amino acid composition of the relevant translated portion of β-chain of haemoglobin, related to the shape of human red blood cells. (3)

    (a) Is this representation indicating a normal human or a sufferer from certain related genetic disease? Give reason in support of your answer.

    (b) What difference would be noticed in the phenotype of the normal and the sufferer related to this gene?

    (c) Who are likely to suffer more from the defect related to the gene represented the males, the females or both males and females equally? And why?

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  • Question 25

    (a) Why are the colourful polystyrene and plastic package used for protecting the food, considered an environment menace?

    (b) Write about the remedy found for the efficient use of plastic waste by Ahmed khan of Bangalore. (3)

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  • Question 26

    Name the genes responsible for making Bt cotton plants resistant to bollworm attack. How do such plants attain resistance against bollworm attacks? Explain. (3)

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  • Question 27

    Name the two different categories of microbes naturally occurring in sewage water. Explain their role in cleaning sewage water into usable water. (3)

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  • Question 28

    Explain the carbon cycle with the help of a simplified model. (5)

    OR

    Explain how does:

    (a) a primary succession start on a bare rock and reach a climax community?

    (b) the algal bloom eventually choke the water body in an industrial area?

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  • Question 29

    The following is the illustration of the sequence of ovarian events (a − i) in a human female.

    (5)

    (i) Identify the figure that illustrates ovulation and mention the stage of oogenesis it represents.

    (ii) Name the ovarian hormone and the pituitary hormone that have caused the above mentioned event.

    (iii) Explain the changes that occur in the uterus simultaneously in anticipation.

    (iv) Write the difference between ‘c’ and ‘h’.

    (v) Draw a labeled sketch of the structure of a human ovum prior to fertilization.

    OR

    How does the megaspore mother cell develop into 7-celled, 8 nucleate embryo sac in an angiosperm? Draw a labeled diagram of a mature embryo sac.

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  • Question 30

    Name the scientists who proved experimentally that DNA is the genetic material. Describe their experiment. (5)

    OR

    (a) List of three different allelic forms of gene 'I'in humans. Explain the different phenotypic expressions, controlled by these three forms.

    (b) A woman with blood group ‘A’ marries a man with blood group ‘O’. Discus the possibilities of the inheritance of the blood group in the following starting with “yes” or “no” for each:

    (i) They produce children with blood group “A” only.

    (ii) They produce children some with “O” blood group and some with “A” blood group.

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