The Energy Cycle
Could you survive on only water and vitamins? Eating food satisfies your hunger because it provides two things you cannot live without—energy and nutrients. All organisms need energy and matter, or nutrients, to survive. For example, black-tailed prairie dogs, which live in the grasslands of North America, eat grass and seeds to get the energy they need. Like all organisms, prairie dogs require energy to carry out all life processes.
The Energy Connection
Organisms in every community can be divided into three groups based how they function in that community. These groups are producers, consumers, and decomposers. These groups also explain how organisms get the energy and nutrients they need. Examine Figure 1 to see how energy and nutrients flow through an ecosystem.
Figure 1 Most living things get their energy either from the sun or from eating other organisms.
Organisms that change the energy in sunlight into chemical energy or food are called producers. Producers do this through the process ofphotosynthesis. Most producers are green plants, but algae and some bacteria are also producers. Grasses are the main producers in a prairie ecosystem. Examples of pro ducers in other ecosystems include cordgrass and algae in a salt marsh and trees in a forest.