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Board Paper of Class 12-Science 2011 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 role of the codons AUG and UGA during protein synthesis.

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  • Question 2

    Normally one embryo develops in one seed but when an orange seed is squeezed many embryos of different shapes and sizes are seen. Mention how it has happened.

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  • Question 3

    Why green plants are not found beyond a certain depth in the ocean?

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  • Question 4

    Write the scientific name of the microbe used for fermenting malted cereals and fruit juices.

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  • Question 5

    Name the type of cell division that takes place in the zygote of an organism exhibiting haplontic life cycle.

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  • Question 6

    How can bacterial DNA be released from the bacterial cell for biotechnology experiments?

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  • Question 7

    Name the event during cell division cycle that results in the gain or loss of chromosome.

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  • Question 8

    Write the importance of cryopreservation in conservation of biodiversity.

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  • Question 9

    State the dual role of deoxyribonucleoside triphosphates during DNA replication.

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  • Question 10

    Differentiate between albuminous and non-albuminous seeds, giving one example of each.

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  • Question 11

    Explain how a hereditary disease can be corrected. Give an example of first successful attempt made towards correction of such diseases.

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  • Question 12

    Justify with the help of an example where a deliberate attempt by humans has led to the extinction of a particular species.

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  • Question 13

    Explain the role of Ti plasmids in biotechnology.

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  • Question 14

    Study the graph given below. Explain how is oxygen concentration affected in the river when sewage is discharged into it.

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  • Question 15

    Name the two types of immune systems in a human body. Why are cell mediated and humoral immunities so called?

    OR

    Write the scientific names of the causal organisms of elephantiasis and ringworm in humans. Mention the body parts affected by them.

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  • Question 16

    State the functions of primary and secondary lymphoid organs in humans.

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  • Question 17

    Why is CuT considered a good contraceptive device to space children?

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  • Question 18

    Explain the process of RNA interference.

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  • Question 19

    (a) Identify (A) and (B) illustrations in the following:

    (i)

    (ii)

    (b) Write the term given to (A) and (C) and why?

    (c) Expand PCR. Mention its importance in biotechnology.

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  • Question 20

    Name the type of interaction seen in each of the following examples:

    (i) Ascaris worms living in the intestine of human

    (ii) Wasp pollinating fig inflorescence

    (iii) Clown fish living among the tentacles of sea-anemone

    (iv) Mycorrhizae living on the roots of higher plants

    (v) Orchid growing on a branch of a mango tree

    (vi) Disappearance of smaller barnacles when Balanus dominated in the Coast of Scotland.

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  • Question 21

    Why do you see two different types of replicating strands in the given DNA replication form? Explain. Name these strands.

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  • Question 22

    Draw a diagram of a male gametophyte of an angiosperm. Label any four parts. Why is sporopollenin considered the most resistant organic material?

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  • Question 23

    How are dominance, co-dominance and incomplete dominance patterns of inheritance different from each other?

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  • Question 24

    (a) Sickle celled anaemia in humans is a result of point mutation. Explain.

    (b) Write the genotypes of both the parents who have produced a sickle celled anaemic offspring.

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  • Question 25

    (a) Why do farmers prefer biofertilisers to chemical fertilizers these days? Explain.

    (b) How do Anabaena and mycorrhiza act as biofertilisers?

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  • Question 26

    (a) Name the stage of Plasmodium that gains entry into the human body.

    (b) Trace the stages of Plasmodium in the body of female Anopheles after its entry.

    (c) Explain the cause of periodic recurrence of chill and high fever during malarial attack in humans.

    OR

    Trace the events that occur in human body to cause immunodeficiency when HIV gains entry into the body.

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  • Question 27

    What is inbreeding depression and how is it caused in organisms? Write any two advantages of inbreeding.

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  • Question 28

    (a) Describe the stages of oogenesis in human females.

    (b) Draw a labelled diagram of human ovum released after ovulation.

    OR

    (a) When and where does spermatogenesis occur in a human male?

    (b) Draw a diagram of a mature human male gamete. Label the following parts: acrosome, nucleus, middle piece and tail.

    (c) Mention the functions of acrosome and middle piece.

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  • Question 29

    (a) Explain primary productivity and the factors that influence it.

    (b) Describe how do oxygen and chemical composition of detritus control decomposition?

    OR

    (a) What is El Nino effect? Explain how it accounts for biodiversity loss.

    (b) Explain any three measures that you as an individual would take, to reduce environmental pollution.

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  • Question 30

    Explain the salient features of Hugo de Vries theory of mutation. How is Darwin’s theory of natural selection different from it? Explain.

    OR

    (a) Name the primates that lived about 15 million years ago. List their characteristic features.

    (b) 

    (i) Where was the first man-like animal found?

    (ii) Write the order in which Neanderthals, Homo habilis and Homo erectus appeared on earth. State the brain capacity of each one of them.

    (iii) When did modern Homo sapiens appear on this planet?

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