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Environmental Issues — BIOLOGY STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 ScienceBIOLOGYEnvironmental Issues5 Marks
Question
  1. Why is the ozone layer required in the stratosphere? How does it get degraded? Explain.
  2. Why is the ozone depletion a threat to mankind?
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Answer

  1. Ozone layer in the stratosphere acts as a shield to absorb the ultraviolet radiation from the sun, which is highly injurious to living organisms.
  • Chlorofluorocarbons (CFCs), from refrigerators and aerosol sprays, degrade the ozone layers.
  • The UV rays act on the CFCs and release CI atoms, which degrade ozone to molecular oxygen.
  1. In the absence of ozone, which absorbs the ultraviolet radiation, the UV rays reach the earth and cause the following ill-effects.
  • (i) UV-B damages DNA and causes mutation in living organisms.
  • (ii) It causes ageing of skin, damage to skin cells and various types of skin cancers.
  • (iii) A high dose of UV-B causes inflammation of cornea, called snow blindness, cataract and even permanent damage to cornea.

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