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A food web is an ecological concept which represents the relationships between producers and consumers in an ecosystem. It is normally represented graphically, where each species in a community is connected to all other species it consumes (or which consume it). In more modern conceptions, the strength of the trophic transfer (read: the amount of biomass consumed) is indicated by the thickness of the link in the graphic. The strength of the trophic transfer is normally determined by bioenergetic modelling or by radiotracers.

From the concept of the food web, biologists have classified organisms based on their relative position into four categories:

An example of a food web (highly simplified) in a lake might be as follows:

        Walleye
^ ^
/ \
/ \
/ \
minnow yellow perch
|\ /|
| \ / |
| \ / |
| \ / |
| * |
| /\ |
| / \ |
| / \ |
| / \|
Daphnia Copepods
\ /
\ /
\ /
\ /
\/
algae
|
|
dissolved nutrients

Where the walleye is a tertiary consumer, the minnows and perch secondary consumers, the zooplankton primary consumers and the algae the primary producers.

There are some problems with the concept of the food web, and as a result it has fallen out of favour in recent years. The entire microbial loop is ignored by this model. Also, the decomposition cycle, critical to the maintenance of plant biomass, is exluded. Scientists have tried to include these two important compartment, but the result is invariably a god-awful mess.

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