Question

Lichen is indicator of
(A) $C{O_2}$ pollution
(B) $S{O_2}$ Pollution
(C) $C{O_2}$ pollution
(D) Water Pollution

Answer 1

Lichen is the symbiotic association between algae and fungi. Symbiotic association leads to mutual relationships between two organisms in which both organisms are benefited together. Algae provides food to fungi whereas fungi provides shelter to the algae.

Complete answer:
Pollution is defined as the addition of pollutants in the environment which will lead to impact the quality of the environment.
Lichen consists of two organisms i.e. Algae and fungi.

Algae: Algae synthesizes their own food by the process of photosynthesis because of the presence of chloroplast.
Fungi: Fungi don’t contain chloroplast. That’s why they can’t synthesize their own food. Hence, they depend on another organism for their food.
That’s why fungi is generally found in association with algae in lichen. Because algae provides the food to the fungi.
In return, fungi provide shelter to the algae. Hence both algae and fungi are mutually benefited together. This kind of interaction between two organisms is known as symbiotic association.
Indicator species are those species which can grow or not grow in specific conditions. This leads to finding the characteristics of that environment on the basis of their growth pattern.
Lichen can grow in presence as well as in absence of carbon dioxide ($C{O_2}$). Because fungal and algal partners release Carbon dioxide in the respiration process. That’s why option A is incorrect.
Absence of water in the environment or presence of Carbon mono-oxide ($C{O_2}$) concentration affects the growth of lichen in a harsh manner. But lichen are also found in these conditions. That’s why option C and D are incorrect.
Lichen can grow in absence of sulphur dioxide ($S{O_2}$). But in presence of sulphur dioxide, lichen absorbs sulphur dioxide via its efficient absorption system. This leads to accumulation of sulphur in lichen. This enhances sulphur dioxide concentration affects the algal partner because sulphur dioxide is responsible for breaking down of chlorophyll and photosynthesis is inhibited. That’s why lichen acts as an indicator for $S{O_2}$ pollution.

That’s why the right answer is: “Option B”.

Note: Lichen can’t grow in sulphur enriched condition and they are sensitive to sulphur dioxide. That’s why lichen acts as indicator species for sulphur dioxide- pollution. Because lichen has an efficient mode of absorption system. They absorb sulphur dioxide from the environment. This inhibits the growth of algae because photosynthesis is inhibited due to break down of chlorophyll in presence of sulphur dioxide.