CBSE Biology Theory Question Paper Class 12th (2010)

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Series OSS                                                                                                                         Code No.57/1

                                                                               BIOLOGY (Theory)


Time allowed : 3 hours                                                                                             Maximum Marks : 70

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.
(iv)    Wherever necessary,  the diagrams drawn should be neat and properly labelled.

 

 

                                                                                      SECTION A

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1. Mention the site where syngamy occurs in amphibians and reptiles respectively.                  1


2. How is snow-blindness caused in humans ?                           1

 

3. Name one autosomal dominant and one autosomal recessive Mendelian disorder in humans.                   1

 

4. How is the action of exonuclease different from that of endonuclease ?                         1

 

5. India has more than    50,000    strains of rice.  Mention the level of biodiversity it represents.                     1

 

6. Mention the information that the health workers derive by measuring BOD of a water body.                   1

 

7. Name the  enzyme involved in the  continuous replication of DNA strand. Mention the polarity of the template strand.                   1

8. Offsprings derived by asexual reproduction are called clones. Justify giving two reasons.                   1

 

 

                                                                                          SECTION B

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9. Mention the role of ribosomes in peptide-bond formation. How does ATP facilitate it ?                       2

 

10. How do copper and hormone releasing IUD’s act as contraceptives ? Explain.                             2

 

11. If you squeeze a seed of orange you might observe many embryos of different sizes. How is it possible ? Explain.     2

 

12. A recombinant DNA is formed when sticky ends of vector DNA and foreign DNA join.
      Explain how the sticky ends are formed and get joined.                      2

 

13. (i)    Mention  the  number  of primers  required  in  each  cycle  of polymerase chain reaction (PCR). Write the role of primers and DNA polymerase in PCR.
   (ii)    Give the characteristic feature and source organism of the DNA polymerase used in PCR.                       2


14. Define the term ‘health’. Mention any two ways of maintaining it.                         2
                                                OR
Why does a doctor administer tetanus antitoxin and not a tetanus vaccine to a child injured in a roadside accident with a bleeding  wound ? Explain.                               2

 

15.  Giving two reasons explain why there is more species biodiversity in tropical latitudes than in temperate ones.     2

 

16.  Name an opioid drug and its source plant. How does the drug affect the human body ?                 2

 

17. Mention the major cause of air pollution in metro cities. Write any three ways. by which it can be reduced.        2

 

18. How  did  Eli’ Lilly  synthesise  the  human  insulin ?  Mention  one difference between this insulin and the one produced by the human pancreas.                     2

 

 


                                                                                           SECTION C

 

19. (i)    Write the characteristic features of anther, pollen and stigma of wind pollinated flowers.
     (ii)    How do flowers reward their insect pollinators ? Explain.                       3

 

20. (i)    Why  are  grasshopper  and  Drosophila  said  to  show  male heterogamity ? Explain.
     (ii)    Explain female heterogamity with the help of an example.                        3

 

21. In a series of experiments with Streptococcus and mice F. Griffith concluded that R-strain bacteria had been transformed. Explain.                                      3

 

22. (a)    How does the Hardy Weinberg’s expression (p+ 2pq + q2 = 1)

              explain that genetic equilibrium is maintained in a population ?
      (b)    List any two factors that can disturb the genetic equilibrium.                      3

 

23. Mention the name of the causal organism, symptoms and the mode of transmission of the disease Amoebiasis.      3


24. (i)    Mention the property that enables the explants to regenerate into a new plant.
     (ii)    A banana herb is virus-infected. Describe the method that will help in obtaining healthy banana plants from this diseased plant.                        3

 

25.  Mention the product and its use produced by each of the microbes listed below :                            3
(i)      Streptococcus
(ii)     Lactobacillus
(iii)    Saccharomyces cerevisiae

 

26.(i)    Name the organism in which the vector shown is inserted to get the copies of the desired gene.
    (ii)    Mention the area labelled in the vector responsible for controlling the copy number of the inserted gene.
   (iii)    Name and explain the role of a selectable marker in the vector shown.                           3

                                                         

                                                                                            OR

Name  the  insect  pest  that  is  killed  by  the  products  of crylAc gene.  Explain  how  the  gene  makes  the  plant  resistant  to  the insect  pest.                        3

 

27. How do organisms like fungi, zooplanktons and bears overcome the temporary short-lived climatic stressful conditions ? Explain.

 


                                                                                            SECTION D

 

28. Describe in sequence the events that lead to the development of a 3-celled pollen grain from microspore mother cell in angiosperms.                               5
                                                                       OR
(a)    Give   a   schematic   representation   showing   the   events   of spermatogenesis in human male.
(b)    Describe the structure of a human sperm.                    3 + 2

 

29. (a)    State the law of independent assortment.
     (b)    Using  Punnett  Square  demonstrate  the  law of independent assortment  in  a  dihybrid  cross  involving  two  heterozygous parents.    1 + 4
                                                                        OR
How did Alfred Hershey and Martha Chase arrive at the conclusion that DNA is the genetic material ?                 5

 

30. (a)    Why  are  herbivores  considered  similar  to  predators  in  the ecological context ? Explain.
      (b)    Differentiate between the following interspecific interactions in a population :
(i)    Mutualism and Competition
(ii)    Commensalism and Amensalism                              5
                                         OR
(a)    Trace the succession of plants on a dry bare rock.
(b)    How does phosphorus cycle differ from carbon cycle ?                    4 + 1