In a field grass is eaten by mice that are eaten by owls. This represents a food chain with 3 trophic levels. The number of trophic levels is limited because energy in the form of heat is lost at each transfer. After four or five transfers only a fraction of the energy is available. Food chains illustrate the flow of energy in an ecosystem, but do not show the complex relationship that really exits.
Organisms feed on more than one species.
A food web shows all the feeding relationships at each trophic level. Food webs are a more realistic picture of what actual happens in the ecosystem. Within this food web there are several different food chains. Some organisms will be at different trophic levels in different food chains. Use the food web above to answer the following questions.