Description
Lichens are composite organisms made by a symbiotic association of cyanobacteria or green algae and filamentous fungi. Lichens take on the external shape of the fungal partner. The algae cells contain chlorophyll which allows them to live in mineral environments by producing their own organic compounds. Some fix atmospheric nitrogen and some extract minerals from the object they are attached to. They are often the pioneer life form appearing on bare rock in extreme environments.
