Lichens
Lichens
Backyard Plants
Backyardnature.com
LICHEN STRUCTURE:
Structurally, lichens are among the most bizarre of all forms of life. That's because every lichen species is actually composed of two, possibly even three, distinct species of organisms. One species is a kind of fungus. Usually the other species is an alga, but sometimes it can be a photosynthesizing bacterium known as a cyanobacterium. Sometimes all three organisms are found in one lichen.
The drawing at the right gives an idea of what fungal hyphae wrapping around alga cells might look like at the microscopic level. Since all three kinds of organism are profoundly different from one another, what lichens do is almost like merging a shrub with a dog to produce something that looks and lives unlike either shrub or dog!
In this amazing association the fungus benefits from the algae because fungi, having no chlorophyll, can't photosynthesize their own food. A lichen's fungal part is thus "fed" by its photosynthesizing algal part. The algae benefit from the association because the fungus is better able to find, soak up, and retain water and nutrients than the algae. Also, the fungus gives the resulting lichen shape, and provides the reproductive structures. This kind of relationship between two or more organisms, where both organisms benefit, is known as mutualism.
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