Belonging to the phylum My-co-phy-co-phy-ta, their hardy nature allows them to thrive in extremely cold and exposed regions, but some species are extremely sensitive to air pollution, leading to their use as indicator species.  
These organisms come in three major categories: crustose, foliose and fruticose. They sometimes reproduce by releasing small bodies called soredia or by the detachment of outgrowths known as isidia. Belonging to the phylum My-co-phy-co-phy-ta, their hardy nature allows them to thrive in extremely cold and exposed regions, but some species are extremely sensitive to air pollution, leading to their use as indicator species.  FTP, name this symbiotic combination of a fungus and an alga.
These organisms come in three major categories: crustose, foliose and fruticose.
lichen