Food chain

From Palaeos

A food chain describes a single pathway that energy and nutrients may follow in an ecosystem. There is one organism per trophic level, and trophic levels are therefore easily defined. They usually start with a primary producer and end with a top predator. Here is an example of a food chain:

phytoplankton --> copepod --> fish --> squid --> seal --> orca

This "chain" can be described as follows: Orca (also known as "killer whales") feed upon seals, that feed upon squid, that eat small fish, that feed on copepods, that feed on microscopic algae. In this example, algae—autotrophs by virtue of their ability to photosynthesize—are the base of the food chain. It is always the case that numbers—or at least biomass—decreases from the base of the chain to the top. In other words, the number and mass of phytoplankton cells are much greater than the number and mass of copepods being supported by the phytoplankton. Viewed another way: to support one orca requires many seals, large numbers of squid, huge numbers of fish, and so on down the chain (see food pyramid). This is because, with each transfer, some of the energy is lost to the environment. On average, only 10% of the organism's energy is passed on to its predator.

Food chains are overly simplistic as representatives of what typically happens in nature. The food chain shows only one pathway of energy and material transfer. Most consumers feed on multiple species and are, in turn, fed upon by multiple other species. The relations of detritivores and parasites are seldom adequately characterized in such chains as well.

[edit] Links

• Science aid: Food chains Food chains, pyramids of number and biomass designed for teens
• Antarctic Food Web and Chains
• Example of a food chain
• Food Chains Quiz

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