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.
define lichens and give two examples .
Lichens are the "dual or composite"organisms formed by the symbiotic association between "algae and fungi".
They are the simple slow-growing plant that typically forms a low crusty, leaf-like or branching growth on rocks, walls and trees.
Example:
Peltigera Canina, Cristatella, Cretaria islandica, Parmelia(genus)