Lichen - GCSE Biology Definition

Lichens are organisms that are formed by a partnership between a fungus and an alga or a cyanobacterium. The fungus provides structure and protection, while the alga or cyanobacterium carries out photosynthesis to make food. This teamwork allows lichens to survive in environments that can be harsh, such as on rocks or tree bark. Lichens are important for ecosystems because they help break down rocks to form soil, provide food for animals, and are useful indicators of air pollution levels. In GCSE Biology, lichens are an example of symbiosis, which is when two different organisms live and function together closely.