In this topic you will learn about how living things depend on other living things for food.

All food comes from plants. Plants are producers. A producer is an organism that makes its own food. Thomson's gazelle, the zebra, and the wildebeest are grazing animals. They all eat the same grass for food. These three grazing animals are consumers. Consumers are organisms that eat producers or other consumers. Producers and consumers make up a food chain. A food chain is a series of organisms that depend on one another for food. Food chains start with producers. Consumers eat those producers. Other consumers eat the first consumers.

As living things go through their life cycles, new organisms are produced. Old organisms die. The dead plant and animal materials in an ecosystem are cleaned up by decomposers. A decomposer is an organism that breaks down dead plant and animal material. Decomposers include bacteria and fungi. Fungi are organisms that take in chemicals from dead material. Producers, consumers, and decomposers work together to recycle materials through an ecosystem.

An ecosystem contains more than one food chain. It also contains food webs. Food webs are made up of several food chains that are connected. A desert ecosystem food web is made of many food chains.

An ecosystem has many different kinds of organisms. Each type of organism has its own level on an energy pyramid. An energy pyramid is a diagram that shows how energy is used in an ecosystem. Each level in a food pyramid has more members than the level above it. There are more producers than plant eaters. There are more plant eaters than meat eaters.