With reference to lichens, which of the following statements is/are correct ?
1. Lichens are very good indicators of pollution.
2. Lichens grow well in polluted areas.
Select the correct answer from t

Question

With reference to lichens, which of the following statements is/are correct ?
1. Lichens are very good indicators of pollution.
2. Lichens grow well in polluted areas.
Select the correct answer from the code given below :
Code :

UnlockIAS · Accepted Answer

Correct — D, Only 1. Statement 1 is the standard textbook fact: lichens are the classic bioindicator of air pollution, and sulphur dioxide in particular. Statement 2 states the exact opposite of the truth and is what makes statement 1 work. A lichen is a symbiosis of a fungus with an alga or a cyanobacterium; it has no roots, no waxy cuticle and no stomata, so it absorbs water and dissolved minerals directly from rain and the atmosphere over its entire surface — and it has no way of excluding or excreting what it takes in. Dissolved sulphur dioxide attacks the chlorophyll of the photosynthetic partner, the partnership breaks down, and lichen cover simply disappears. That is why industrial and heavily built-up areas show 'lichen deserts' where the bark of trees and the surface of stone are bare. So lichens do not grow well in polluted areas; their retreat from an area is the signal that the air there has deteriorated.

Why the other options are wrong — (a) It keeps the false statement and drops the true one. Lichens are conspicuously absent from polluted air, not flourishing in it, while their value as an indicator of air quality is settled and is the reason they are surveyed at all.  (b) The two statements cannot both be true — accepting statement 2 destroys statement 1. If lichens grew equally well in clean and polluted air, their presence would carry no information about air quality and they could not be indicators. A candidate who reads 'indicator of pollution' loosely as 'found where there is pollution' walks straight into this option.  (c) Statement 1 is correct and is one of the most frequently examined facts in Indian environment papers — lichens are the standard bioindicator of air pollution, especially of sulphur dioxide. Rejecting it leaves the option untenable.

Concept: A lichen is not a single organism but a stable mutualistic association: a fungus (the mycobiont) forms the body, and an alga or cyanobacterium (the photobiont) housed inside it does the photosynthesis. Because the fungal body has no roots, no cuticle and no stomata, everything the lichen needs — and everything the air contains — enters directly across its whole surface, with no regulation and no route of excretion. That physiology makes lichens both extraordinarily hardy in clean but harsh habitats (bare rock, bark, Arctic tundra) and extraordinarily fragile in polluted ones. Sensitivity varies by growth form: the shrubby, hanging fruticose lichens go first, foliose (leafy) lichens next, and the tightly crust-like crustose lichens last.

State PCS 2025 Q34 — Environment & Ecology PYQ with Answer

State PCS 2025 Q34 — Environment & Ecology PYQ with Answer