ECOLOGY
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Symbiotic Relationships:

Fungi differ from plants in that they do not contain chlorophyll and therefore cannot photosynthesize. Instead, they rely on organic matter for nutrition. Being heterotrophs, fungi are, in fact, more similar to animals, both evolutionary and physically, than they are to plants. Fungi can be found “eating” everything from soil and wood to live plants and live animals. The underground, vegetative part of fungi called the mycelium extracts nutrients from the matter. They do this in three ways: as saprophytes, as parasites, and as mutualistic organisms (including mycorrhizae). Although some species of fungi stick to one category, others will switch depending on their situation.

Fungi play an extremely important role in decomposing organic materials to make soil. Included in this phenomenon is fungi's role in rebuilding the ecosystem of forests after a wildfire. The fungi (called "after-fire fungi") quickly re-inhabit a forest after a fire and clean up the remains to make a newly revitalized environment for other organisms.

Saprophytes

Saprophytes live on dead organic matter, including dead wood, dung, and fallen leaves. Most fungi commonly called mushrooms are saprophytes, such as the extremely common Agaricus genus. Perhaps their most important function is the decomposition of organic matter into soil. Without them, wood, leaves and dung would take much longer to be broken down into a soil that can be inhabited by future plants.

Most mushrooms that have a stalk and cap are saprophytes. Additionally, some molds and other major decomposers feed on organic waste.

 



Above: The halucenegenic mushroom Amonita Muscaria, or as its more commonly know as 'fly aggeric' lives off the dead oraganic material in the soil
Below : S. Spectabilis shares the nutrients of a fallen tree with mosses and lichens



Below
: While most shelf fungi share mutualistic bonds with the trees they live on, some can abusively suck the nutrients from their hosts

Parasitic Fungi

Parasitic fungi attack living plants or animals. They take nutrients from their host and thereby hurt them. Polypores, or shelf fungi, grow on the sides of trees and feed off of the live wood. Cyttaria fungi grow on trees and often cause them to grow galls. Though they live off of trees, the trees are not necessarily killed. The fungus just continually takes some of what the tree creates through photosynthesis. When they are killed, though, the fungus will frequently stay alive as a saprophyte, living off of the now-dead wood. Parasitic fungi can grow on (and in) animals as well. Thrush, athlete’s foot and ringworm are all examples of microfungi that affect humans.

Left: Ringworm is a fungus that parasitically lives on the surface of human skin; it's common in tropical climates and is very difficult to rid of



Mutualistic Fungi

Mutualistic fungi form relationships with organisms in which both sides benefit (or, at least, are not harmed). It is important, though, to point out that “mutualistic” does not mean that each party benefits equally from the ralationship. Lichens are a common example of a mutualistic relationship between fungi and algae. As is often grows on rock (Crustose Lichen), the fungus has no source of nutrients from its surroundings. And so it receives them from the photosynthesizing algae. In return, the fungus offers the algae structure and protection. Lace Lichens (falsely nicknamed Irish Moss) are an example of a lichen that incorporate yet another partner. It hangs from trees for support. Perhaps the most important of the mutualistic fungi are mycorrhizae. Another interesting relationship is with achlorophyllous (non-photosynthesizing) plants. in this case, fungi extract all the nutrients from the soil that the plant needs. The fungi, on the other hand, does not nessecarily benefit.

Mycorrhizare are a relationships between the roots of plants and fungi in which the plant receives nutrients that the fungus derives from the soil and the fungus sometimes receives photosynthesized compounds. The mycelium of a mycorrhizal fungus sheaths the roots of the plant, offering several advantages to the plant. Mycelium around the root ends helps the roots expand farther while protecting them against other pathogenic fungi and toxins. More importantly perhaps is that the mycelium extracts nutrients from the soil, leaving them to be absorbed by the plant. Many plants would not survive without this mycorrhizal relationship. Eucalycptus trees are among countless plants that depend on mycorrzae.




Above: Lichen evolved to live in corralation with algea - mycelium, which is wrapped around algal cells, offers key minerals such as derived nitrogen to the algea as the the algea contributes sugar to sustain the fungus
Below: Mushrooms living in a mutualistic relationship with a tree



 

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ECOLOGICAL OVERVIEW

At 1 we have an achlorophyllous plant (in black) using a parasitic fungus (in red) as its source of carbon. Notice that the red hyphae have penetrated a tree and some red mushrooms have been formed at the base of the trunk.

At 2 there are some mushrooms that have arisen from a mycorrhizal fungus. Note how the associated mycelium is linking several plants.

At 3 the mycelium of yet another mycorrhizal fungus is decomposing some fallen twigs.


 

Sources:

All photographs acquired using google image search
All diagrams and illustrations are hand drawn by Jon, Chuck and Jesslyn
Info adapted from:
http://www.anbg.gov.au/fungi/index.html
All text written / website design done by Chuck Goldhaber, Jonathan Wachter and Jesslyn Jamison



ECOLOGY
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