Biology Class 12 NCERT Solutions: Chapter 16 Environmental Issues Part 3 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Q. 6 Why ozone hole forms over Antarctica? How will enhanced ultraviolet Radiations affect us?


  • The ozone hole is more prominent over the region of Antarctica. It is formed due to an increased concentration of chlorine in the atmosphere.
  • Chlorine is mainly released from chlorofluorocarbons (CFC՚s) widely used as refrigerants. The CFC՚s magnate from the troposphere to the stratosphere, where they release chlorine atoms by the action of UV rays on them.
  • The release of Chlorine atoms causes the conversion of ozone into molecular oxygen. One atom of chlorine can destroy around 10,000 molecules of ozone and causes ozone depletion.
  • The formation of the ozone hole will result in an increased concentration of UV -B radiations on the Earth՚s surface. UV − B damages DNA and activates the process of skin ageing.
  • It also causes skin darkening and skin cancer. High levels of UV − B cause corneal cataract in human beings.

Q. 7 Discuss the role of women and communities in protection and conservation of forests.


Women and communities have played a major role in environmental conservation movements.

  1. Case study of the bishnoi community:
  2. The Bishnoi community in Rajasthan strictly believes in the concept of living peacefully with nature. In 1731, the king of Jodhpur ordered his ministers to arrange wood for the construction of his new palace.
  3. For this purpose, the minister and the workers went to bishnoi village. There, a Bishnoi woman called Amrita Devi along with her daughter and hundreds of other Bishnois showed the courage to step forward and stop them from cutting trees.
  4. They embraced the trees and lost their lives at the hands of soldiers of the king. This resistance by the people of the village forced the king to give up the idea of cutting trees.
  5. Chipko movement:
  6. The Chipko movement was started in 1974 in the Garhwal region of the Himalayas. In this movement, the women from the village stopped the contractors from cutting forest trees by embracing them.

Q. 8 What measures, as an individual, you would take to reduce environmental pollution?


  • The following initiatives can be taken to prevent environmental pollution:
  • Measures for preventing Air pollution
  • Planting more trees
  • Use of clean and renewable energy sources such as CNG and bio-fuels
  • Reducing the use of fossil fuels
  • Use of catalytic converters in automobiles
  1. Measures for preventing water pollution
  2. Optimizing the use of water
  3. Using kitchen waste water in gardening and other household purposes
  4. Measures for controlling Noise pollution
  5. Avoid burning crackers on Diwali
  6. Plantation of more trees
  7. Measures for decreasing solid waste generation
  8. Segregation of waste
  9. Recycling and reuse of plastic and paper. Reducing the use of plastics.
  10. Composting of biodegradable kitchen waste.

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