Question

Which of these is a bioindicator?
a) Lichens tracing the presence of pollution
b) Fossil lichens
c) Special type of litmus paper
d) None of the above

Answer 1

Hint:-As the name suggests, bioindicator is an indicator species whose presence indicates the quality of its environment. These species help us understand the presence and exposure to pollutants. Bioindicators can be plants or animals.

Complete Answer:-
Lichens are formed due to association of algae and fungi. Lichens are widely distributed in nature and found on barks of trees, walls and mountains. They are autotrophic organisms and reproduce by asexual, sexual and vegetative modes. The association as seen in Lichens can be symbiotic or parasitic.
Lichens play a major role in detecting environmental pollution. These species are very sensitive to sulphur dioxide and cannot grow in areas where this pollutant is present in high concentration in air. Thus, the absence of Lichens in a certain area indicates air pollution. This basic information can lead to further investigative studies on the amount of exposure to the pollutant.
Lichens are estimated to have formed first around 400 million years ago. Fossil lichens’ records are not very clear. Fossils provide a lot of information on the morphology, structure and evolution of Lichens over a period of time. However, fossil lichens do not provide any information on environment quality, hence they are not bioindicators.
Litmus paper are filter papers adsorbed with Litmus. Litmus is a water soluble mixture of dyes. The chief source of litmus are different forms of Lichens. Litmus papers act as an indicator of acidity or basicity of a solution. Red litmus paper turns blue in basic solutions and Blue litmus paper turns red in acidic solutions. However, they do not act as bioindicators.
Therefore, it can be concluded that Lichens are indicators of environmental pollution or bioindicators.
Thus, the right option is A.

Note:- Lichens are the result of association between an alga and a fungus. They are found in all biomes of the world. Lichens serve as a bioindicator species. Their absence indicates environmental pollution in an area. Lichens are also colonizers and the first organisms to develop in a barren area. They are also used as food, fodder and a source of medicines.