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The Food Web

posted Nov 15, 2014, 1:52 PM by Fleur Parker

All organisms, dead or alive, are potential food sources for other organisms. A caterpillar eats a leaf, a robin eats the caterpillar, a hawk eats the robin. Eventually, the tree and the hawk also die and are consumed by decomposers.

Organisms in an ecological community are related to each other through their dependence on other organisms for food. In a food chain a producer is eaten by a herbivore that is in turn eaten by a carnivore. Eventually, the carnivore dies and is eaten by a decomposer. For example, in a lake, phytoplankton are eaten by zooplankton and zooplankton are eaten by small fish. The small fish are eaten by large fish. The large fish eventually die and decompose. Nothing goes to waste. Food chains are channels for the oneway flow of solar energy captured by photosynthesis through the living components of ecosystems. Food chains are also pathways for the recycling of nutrients from producers, through herbivores, carnivores, omnivores, and decomposers, finally returning to the producers.

The perfectly linear relations represented by food chains are almost never found in natural ecosystems. Although all organisms have somewhat specialized diets, most can eat a variety of different foods. Thus, each trophic level appears as part of several different interconnected food chains. These food chains combine into highly complex food webs.

As with food chains, a food web's source of energy is the sun. The solar energy is harvested by producers such as green plants or algae. 

Each step in a food web or food chain involves a transfer of matter and energy (in the form of chemical bonds stored in food) from organism to organism. 

A diagram depicting those organisms that eat other organisms in the same ecosystem. In some cases, the organisms may already be dead. Thus, a food web is a network of energy flows in and out of the ecosystem of interest. Such flows can be very large, and some ecosystems depend almost entirely on energy that is imported. A food chain is one particular route through a food web.