What is a food web?

A food web is a diagram made up of many of the food chains in an ecosystem. Let us review the terms ecosystem and food chain.

Ecosystem: An ecosystem is a community of living things which interact with each other and their environment. An ecosystem is made up of all the living and non-living things in an area. An ecosystem may be as small as your back yard or as large as an ocean.

Food chain: A food chain is a diagram which shows how energy flows from one living thing to another. Look at the food chain below.

grass → grasshopper → bird → snake

This food chain shows that a grasshopper ate some grass. Then the grasshopper was eaten by a bird which was later eaten by a snake. However, in the same ecosystem there may also be other food chains such as the one below.

grass → grasshopper → lizard → cat

We can see that in this same ecosystem, both birds and lizards eat grasshoppers.

_{Some birds eat grasshoppers. (Photo by Haraneeya Pankaj and used under this creative commons license.)}

_{Some lizards eat grasshoppers as well. (Photo by M. Purves an used under this creative commons license)}

In most ecosystems there are living things that are eaten by several animals. For instance, grasshoppers may be eaten by birds, lizards and frogs. Also, many living things eat more than one thing. For instance, a bird may eat grasshoppers, caterpillars and beetles.

A food chain shows only one way in which energy flows in an ecosystem. However, we can use a food web to show many of the ways that energy flows in an ecosystem.