Question

Lichens are important in the studies on atmospheric pollution because they
A. Can also grow in greatly polluted atmosphere
B. Can readily multiply in polluted atmosphere
C. Are very sensitive to pollutants like $S{O_2}$
D. Efficiently purify the atmosphere

Answer 1

Lichens are composite organisms made of fungus and algae/cyanobacteria. These different life forms work closely together. The algae or cyanobacteria provide sugar molecules made from sunlight to fungus, and in turn the fungus provides shelter for both of them. Lichens obtain their nutrients from the air and are quick to respond to environmental changes.

Complete explanation:
Option A: Lichens are extremely sensitive to air pollutants. Since they have no roots or protective surface to filter what they absorb, the pollutants in the air can accumulate in the lichens and affect their growth.
Option A is incorrect.
Option B: Lichens are found in smaller sizes and less variety in areas having more air pollution. The toxic air pollutants accumulate and prevent the multiplication of Lichens.
Option B is incorrect.
Option C: Lichens are extremely sensitive to air pollutants like sulfur dioxide. Sulfur dioxide greatly affects the growth, metabolism and biochemical process of Lichens. When excessive sulfur dioxide is present in the air, Lichens cannot be seen in that area. This forms as nature’s indicator of air pollution.
Option C is correct.
Option D: Lichens do not have the ability to purify the air. They are composite organisms that depend on clean air for their nutrition.
Option D is incorrect.

Hence the correct answer is option C. Are very sensitive to pollutants like $S{O_2}$.

Note:
Sulphur dioxide pollution comes from coal-burning industries. This pollutant has killed many lichens in the past, but now it has lessened due to less burning coal. In humans, sulfur dioxide can irritate the mucus lining of the nose, throat, and lungs. The sensitivity of lichens to air pollution makes them a great air quality indicator.