Lichens are composite, symbiotic organisms made up from members of as many as three kingdoms. The dominant partner is a fungus (kingdom Fungi) which then cultivates partners that manufacture food by photosynthesis. Sometimes the partner is algae, sometimes cyanobacteria (formerly called blue-green algae), and sometimes both partners at once. Lichens grow everywhere. They are pioneers on bare rock, scrub sand, cleared soil, and living bark. Able to shut down metabolically during periods of unfavorable conditions, they can survive extremes of heat, cold, and drought. Given appropriate amounts of light and moisture, clean air, and freedom from competition, lichens can colonize almost any undisturbed surface.
Most lichens grow very, very slowly, often less than a millimeter per year, and some lichens are thought to be among the oldest living things on Earth.
Most lichens grow very, very slowly, often less than a millimeter per year, and some lichens are thought to be among the oldest living things on Earth.
Rainder Moss from John Bradford on Vimeo.