food chain

In ecology, a sequence showing the feeding relationships between organisms in a habitat or ecosystem. It shows who eats whom. An organism in one food chain can belong to other food chains. This can be shown in a diagram called a food web.

One of the most important aspects of food is that it provides energy for an organism. So a food chain shows where each organism gets its energy. The arrow in a food chain represents the direction of energy flow. Not all of the energy in all of the organisms at one step of a food chain is available to the organisms later in the chain. In general, fewer organisms are found at each step, or trophic level, of the chain. A pyramid of numbers shows this clearly. Some organisms may be small but very numerous, so population size may not be a good measure of how much of an organism there is in a habitat. Biomass – the total mass of organisms in an area – may be a more useful measure.