urbpan: (morel)
[personal profile] urbpan
Broadly speaking, there are three main divisions of complex multicellular organisms:

Plants, which cannot move, but can make their own food out of sunlight.
Animals, which can move, but cannot make their own food, so they move around and eat plants and other animals.
And Fungi, which can neither move nor make their own food.

So how do they get food?  They have to live in it.

Fungi all develop from spores, which are more or less analogous to seeds in plants, but much much smaller.  Spores are so small and light that most of them simply travel from the parent fungus to wherever they will become a new fungus organism by drifting on air currents.  The chances that an individual spore will happen to land in a suitable place to grow are incredibly remote, so fungi stack the deck by producing billions of spores at a time.  In order to produce this mind-boggling number of spores, fungi have evolved a range of bizarre and beautiful shapes that maximize surface area.  These fruiting bodies, or mushrooms, include shapes that resemble other things found in nature that maximize surface area.  There are spore bearing bodies that resemble the gills of a fish, the wrinkles of a brain, and the branching forms of coral.

These fruiting bodies are temporary short-term structures made by the long-term living fungus.  The fungus itself is a network of very fine strands of cells, called a mycelium.  The mycelium secretes enzymes into its environment, breaking down organic particles into nutrients that it can absorb.  Often as it does this, it makes material that is otherwise inedible, available to be consumed by plants and animals.  In a habitat like a forest, fungi play the primary role in turning dead trees into soil.  Without fungi, forests would simply be unable to survive.

Since they cannot move, and must live in their food sources, fungi (and the mushrooms they produce) can be reliably found in certain areas.  The two most common habitats for mushroom-producing fungi are dead wood, and the roots of trees.  Other habitats include very rich soil, leaf litter, feces and other organic debris.  Each fungus species has a specific habitat that it lives in;  Just as you will not find a polar bear in the desert, or a fresh water fish in the ocean, you won't find a fungus that lives in the roots of a tree growing on dead wood or in an open treeless field.  (But because the mycelium lives invisibly in its food source, it may be difficult to tell where the fungus that produced a mushroom is living.   For example, you may find a mushroom growing out of the soil, but it may be growing out of a dead tree stump that is hidden under the dirt.)

Fungi that live amongst the roots of trees and other perennial plants are said to be "mycorrhyzal."  They feed on some of the plant's products from photosynthesis, and release nutrients that the plant can use.  The fungus mycelium also helps the area around the roots retain water, and may provide the plant some protection from disease.  Mycorrhyzal mushrooms are very common in natural ecosystems, but in places like cities where most of the trees are raised on nurseries and artificially placed as shade or landscape trees, they are less common.  It can be difficult to determine if a mushroom growing from the soil near a tree is mycorrhyzal, or if the fungus that produced it is simply surviving on the nutrients of the soil.

Some fungi form partnerships with animals to spread their spores, instead of relying on random air currents.  There are mushrooms called stinkhorns which bear their spores in a sticky foul-smelling mass that attracts flies.  The flies spread the spores far and wide, usually landing somewhere with rich organic material that may prove to be fertile ground for new fungus growth.  There are also mushrooms that grow underground and produce a strong odor that attracts burrowing rodents.  The rodents east these mushrooms, familiar to most everyone as truffles, and distribute the spores in their feces.  This permits the truffle fungus to be more economical with the production of spores;  studies have shown that in some species at least, the spores are not activated until they pass through a rodent digestive system.

...

(what next?)



 

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