A lichen with rounded lobes

A lichen with rolled or channeled lobes

Division Mycomycota are the fungi in lichens, mutualist associations between these fungi and algae or photosynthetic bacteria. Lichens consist of many small photosynthesizers trapped in the tangled hyphae of the lichen fungus. The photoautotrophs are located near the surface of the fungus to allow access to sunlight.

Though the details of the relationship between the fungi and the algae or cyanobacteria are not completely known, it seems that the photosynthesizers provide the fungus with organic sugars in exchange for shelter, inorganic nutrients and water. Some of the lichen algae are capable of living by themselves, but the fungi of Division Mycomycota rely on their partners to survive. The lichen relationship enables both partners to survive where neither could live alone, such inhospitable rock surfaces.

This, and their ability to erode and eventually break up rocks by growing into rock crevices, makes lichens important in the primary succession of a habitat. Lichens can also withstand conditions of extreme cold and drought, as they are opportunists: a lichen will take advantage of occasional favorable conditions to allow it to live for very long periods of time. Lichens are thus important in such ecosystems as the frozen tundra.

Lichens can reproduce in three ways. First of these is fragmenting, when the lichen extends itself over a large area and then breaks into two or more pieces. The second method involves production of reproductive units: small bits of hyphae containing one or several algal/bacterial cells. These reproductive units are scattered by the wind, and each will land and begin to grow. Also, lichen fungi and photosynthesizers can reproduce independently, and lichen fungi produce fruiting bodie for this purpose. Once they have reproduced, however, the two parts must reassociate with each other.

Procedures
1. Define lichen.
2. Discuss their ecological role.

To see the ecological roles of lichen, click here