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Board Paper of Class 12-Science 2018 Biology (SET 3) - Solutions

General Instructions :
(i) There are a total of 26 questions and five sections in the question paper, All questions are compulsory.
(ii) Section A contains question number 1 to 5, Very Short Answer type questions of one mark each.
(iii) Section B contains question number 6 to 10, Short Answer type I questions of two marks each.
(iv) Section C contains question number 11 to 22, Short Answer type II questions of three marks each.
(v) Section D contains question number 23, Value Based Question of four marks.
(vi) Section E contains question number 24 to 26, Long Answer type questions of five marks each.
(vii) There is no overall choice in the question paper, however, an internal choice is provided in one question of two marks, one question of three marks and all three questions of five marks. An examinee is to attempt any one of the questions out of the two given in the question paper with the same question number.
  • Question 1
    How do cytokine barriers provide innate immunity in humans? VIEW SOLUTION
  • Question 2
    Write the dual purpose served by Deoxyribonucleoside triphosphates in polymerisation. VIEW SOLUTION
  • Question 3
    Write the names of the following:
    (a) A 15 mya primate that was ape-like
    (b) A 2 mya primate that lived in East African grasslands VIEW SOLUTION
  • Question 4
    Mention the chemical change that proinsulin undergoes, to be able to act as mature insulin. VIEW SOLUTION
  • Question 5
    Name two diseases whose spread can be controlled by the eradication of Aedes mosquitoes. VIEW SOLUTION
  • Question 6
    How did a citizen group called Friends of Arcata Marsh Arcata, California, USA, help to improve water quality of the marshland using Integrated Waste Water Treatment? Explain in four steps. VIEW SOLUTION
  • Question 7
    Your advice is sought to improve the nitrogen content of the soil to be used for cultivation of a non-leguminous terrestrial crop.

    (a) Recommend two microbes that can enrich the soil with nitrogen.

    (b) Why do leguminous crops not require such enrichment of the soil?    VIEW SOLUTION
  • Question 8
    You have obtained a high yielding variety of tomato. Name and explain the procedure that ensures retention of the desired characteristics repeatedly in large populations of future generations of the tomato crop. VIEW SOLUTION
  • Question 9
    (a) Name the source plant of heroin drug. How is it obtained from the plant?

    (b) Write the effects of heroin on the human body. VIEW SOLUTION
  • Question 10
    With the help of an algebraic equation, how did Hardy-Weinberg explain that in a given population the frequency of occurrence of alleles of a gene is supposed to remain the same through generations?
     
    OR

    Although a prokaryotic cell has no defined nucleus, yet DNA is not scattered throughout the cell. Explain. VIEW SOLUTION
  • Question 11
    (a) Differentiate between analogous and homologous structures.
    (b) Select and write analogous structures from the list given below :
    (i) Wings of butterfly and birds
    (ii) Vertebrate hearts
    (iii) Tendrils of Bougainvillea and Cucurbita
    (iv) Tubers of sweet potato and potato
    VIEW SOLUTION
  • Question 12
    How has the use of Agrobacterium as vectors helped in controlling Meloidegyne incognitia infestation in tobacco plants? Explain in correct sequence. VIEW SOLUTION
  • Question 13
    (a) 'India has greater ecosystem diversity than Norway." Do you agree with the statement? Give reasons in support of your answer.
    (b) Write the difference between genetic biodiversity and species biodiversity that exists at all the levels of biological organisation.

    OR
     
    Explain the effect on the characteristics of a river when urban sewage is discharged into it. VIEW SOLUTION
  • Question 14
    Explain the mechanism of 'sex determination' in birds. How does it differ from that of human beings? VIEW SOLUTION
  • Question 15
    Explain out-breeding, out-crossing and cross-breeding practices in normal husbandry. VIEW SOLUTION
  • Question 16
    (a) Organic farmers prefer biological control of diseases and pests to the use of chemicals for the same purpose. Justify.

    (b) Give an example of a bacterium, a fungus and an insect that are used as biocontrol agents. VIEW SOLUTION
  • Question 17
    (a) How has the development of bioreactor helped in biotechnology?
    (b) Name the most commonly used bioreactor and describe its working. VIEW SOLUTION
  • Question 18
    Explain the roles of the following with the help of an example each in recombinant DNA technology :

    (a) Restriction Enzymes
    (b) Plasmids VIEW SOLUTION
  • Question 19
    Differentiate between Parthenocarpy and Parthenogenesis. Give one example of each. VIEW SOLUTION
  • Question 20
    Medically it is advised to all young mothers that breastfeeding is the best for their newborn babies. Do you agree? Give reasons in support of your answer. VIEW SOLUTION
  • Question 21
    Draw a diagram of a mature human sperm. Label any three parts and write their functions. VIEW SOLUTION
  • Question 22
    (a) Expand VNTR and describe its role in DNA fingerprinting.
    (b) List any two applications of DNA fingerprinting technique. VIEW SOLUTION
  • Question 23
    Looking at the deteriorating air quality because of air pollution in many cities of the country, the citizens are very much worried and concerned about their health. The doctors have declared health emergency in the cities where the air quality is very severely poor.
    (a) Mention any two major causes of air pollution.
    (b) Write any two harmful effects of air pollution to plants and humans.
    (c) As a captain of your school Eco-club, suggest any two programmes you would plan to organise in the school so as to bring awareness among the students on how to check air pollution in and around the school. VIEW SOLUTION
  • Question 24
    (a) Write the scientific name of the organism Thomas Hunt Morgan and his colleagues worked with for their experiments. Explain the correlation between linkage and recombination with respect to genes as studied by them.

    (b) How did Sturtevant explain gene mapping while working with Morgan?
     
    OR

    (a) State the 'Central dogma' as proposed by Francis Crick. Are there any exceptions to it? Support your answer with a reason and an example.

    (b) Explain how the biochemical characterisation (nature) of 'Transforming Principle' was determined, which was not defined from Griffth's experiments. VIEW SOLUTION
  • Question 25
    (a) Following are the responses of different animals to various abiotic factors. Describe each one with the help of an example.
     (i) Regulate
     (ii) Conform
     (iii) Migrate
     (iv) Suspend

    (b) If 8 individuals in a population of 80 butterflies die in a week, calculate the death rate of population of butterflies during that period.

    OR

    (a) What is a trophic level in an ecosystem? What is 'standing crop' with reference to it?
    (b) Explain the role of the 'first trophic level' in an ecosystem.
    (c) How is the detritus food chain connected with the grazing food chain in a natural ecosystem? VIEW SOLUTION
  • Question 26
    (a) Describe any two devices in a flowering plant which prevent both autogamy and geitonogamy.

    (b) Explain the events upto double fertilisation after the pollen tube enters one of the synergids in an ovule of an angiosperm.
     
    OR

    (a) Explain menstrual cycle in human females.

    (b) How can the scientific understanding of the menstrual cycle of human females help as a contraceptive measure? VIEW SOLUTION
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