Question

Why do lichens not occur in Delhi whereas they commonly grow in Manali or Darjeeling?

Answer 1

Lichens not grow in Delhi because of too much pollution in Delhi. Lichens cannot survive in the atmosphere having more amount of harmful gases and lot of pollution. Whereas in Manali and Darjeeling the atmosphere is fresh and free of too much pollution so lichens can survive there easily.

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Answer 2

Lichens occur in places that is free from pollution.
They are called bio-indicators of pollution. The reason why they are not found in Delhi is that the city has high incident of pollution in comparison to Manali or Darjeeling.

Manali and Darjeeling are free from pollution,so lichens are easily found there.

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