Previous Year Question
Which one of the following is a bio indicator of air pollution?
Fern
Lichen
Money plant
Dodder
Correct Answer: B
Detailed Solution
A Lichen is not a single organism; it represents a symbiotic association between a Fungus and a photosynthetic Alga or Cyanobacterium.
Lichens lack a developed root system, protective cuticle and stomata. They obtain water and many nutrients directly from the surrounding atmosphere. Therefore, atmospheric pollutants can affect them readily.
Different lichen species show different sensitivities to air pollutants. In particular, many lichens are highly sensitive to Sulphur Dioxide (SO₂) and other atmospheric pollutants.
The presence, absence, abundance and diversity of lichen species in an area can therefore be used to assess air quality. Under severe pollution, sensitive lichen species may decline or disappear completely.
For this reason, Lichens are widely used as Bio-indicators of Air Pollution.