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Extreme Growth Habitats
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Lichens, built for
...
 ENVIRONMENTS
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Lichens can grow in some of
the most extreme environments on Earth--the arctic tundra, hot
deserts, rainforests, dizzying cliff faces and even toxic waste
dumps.
Lichens aren't your "standard-issue"
plants. For one thing, red or brown pigments often camouflage the chlorophyll
that would otherwise make them look green. And lichens don't have special tubes
inside them for carrying water and nutrients. Nor do they have the standard
leaves that plants do.
The secret to the lichen's
success has to do with its being a combination of two organisms
living together as one in a symbiotic, or cooperative, relationship.
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(Photo courtesy of the Institute for
Field Education. Copyright 1995 William Gould.)
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Put another way, lichens are a "marriage"
between two lower types of plants: an alga (like stoneworts, seaweed, or pond
scum) plus a fungus (like molds, rusts, mildews, or mushrooms).
Algae are often green and mainly found in
water. Fungi don't have chlorophyll, and some are parasitic, meaning they feed
off other organisms. Other fungi absorb nutrients from soil or dead organic
material. |
 How these algae and fungi form a lichen is
one of the great puzzles in biology. But their symbiotic relationship is one of
the best examples of two or more organisms living together. Both live in the
same body, each doing what it does best and surviving in some of the world's
most extreme conditions.
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