Biology | What Is A Lichen?
What is a lichen?
Lichens are organisms that grow on rocks, tree branches, or bare ground. They do not have roots, stems, flowers, or leaves. Lichens are composed of a green alga (singular form of algae) and a colorless fungus which co-exist for their mutual benefit. The alga, which has chlorophyll, manufactures its own food through photosynthesis (the process that uses sunlight as an energy source to convert water, carbon dioxide, and inorganic salts into oxygen and carbohydrates). The fungus, which has no chlorophyll, absorbs food from the alga. The fungus helps the alga by covering it and preventing it from drying out.
There is some question as to whether the fungus and alga derive equal benefit from their relationship. Some studies in which the fungus and alga of a lichen have been separated indicate that fungus is more dependent on the alga than vice-versa. While the alga is able to survive on its own, the isolated fungus has...
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