Lichens are symbioses of algae and fungi or even bacteria. You can find them on trees and stones, and they are often the first settlers of bleak areas. Because of their sensitivity, they can show us whether the air is good or bad.
How do lichens
show us if
the air is clean?
Picture: Tree trunk with three important representatives of microbiota, slime mould (1), lichens (2) and fungal fruiting bodies (3)
fungal fruiting body