Why are lichens called bio-indicators?
Lichens are called bio indicators as they indicate the environmental pollution through their gradual extinction in those regions where there is excessive pollution especially the air pollution.
Where do lichens grow?
Lichens grow on the old walls, trunk of trees , bare ground and the rocks .Some lichens (crustose lichens) secrete acids into rocks and disintegrate them to soil particles from which vegetation arises so they are also called pioneers of vegetation.