CBSE Class 12 Biology Question Paper 2011 Set 57 1

CBSE CLASS XII Questions

• 1.

  Assertion (A): The embryo with 8 to 16 blastomeres is called a morula.
  Reason (R): The morula continues to divide and transform into trophoblast.
  

  • Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
    
  • Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
    
  • Assertion (A) is true, but Reason (R) is false.
    
  • Assertion (A) is false, but Reason (R) is true.
    
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• 2.

  "Indo-Burma" is considered as a hotspot. What is meant by the term "hotspots" in biodiversity ? List two criteria used for determining a "hotspot". Name any two hotspots of India.

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• 3.

  If a sperm nucleus is injected into an oocyte then all of the following events are bypassed except -

  • The swimming of sperm to meet the egg in the oviduct.
  • The sperm’s acquisition of motility in the epididymis.
  • A sperm comes in contact with the zona pellucida layer of the ovum.
  • The complex process like cell division and cell differentiation.
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• 4.

  Choose a correct option that shows an interaction in which one species benefits while the other is neither harmed nor benefitted.

  • Mycorrhizal associations between fungi and roots of higher plants
    
  • Sea anemone and clownfish
    
  • Abingdon tortoises and goats in the Galapagos Island
    
  • Cuscuta on hedge plants
    
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• 5.

  Assertion (A) : The two chains of DNA have antipolarity.

  Reason (R) : In one chain of DNA, ribose sugar at \(5^{\prime}\) end consists of a free phosphate moiety, while at the other end, the ribose sugar has free \(3^{\prime}\) - OH group.

  • Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
  • Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
  • Assertion (A) is true, but Reason (R) is false.
  • Assertion (A) is false, but Reason (R) is true.
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• 6.

  Assertion (A) : Hardy-Weinberg principle says that allele frequencies in a population are stable.

  Reason (R) : Hardy-Weinberg principle is applicable only when genetic drift does not occur.

  • Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
  • Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
  • Assertion (A) is true, but Reason (R) is false.
  • Assertion (A) is false, but Reason (R) is true.
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