Did you know that on the earth there are more than 50 million species of organisms? We call the regions of the earth where living organisms can live the biosphere. In this activity, you will learn more about how energy is passed from one living thing to another.

Food Chains

Many relationships in ecosystems are based on feeding. Energy and matter from feeding passes through an ecosystem by way of food chains. A food chain is a model that shows how energy is passed, in the form of food, from one living thing to another.

• Food chains begin with plants. These organisms are able to make their own food and are called producers.

• Next in the chain are consumers. Consumers are animals that cannot make their own food. They eat either producers or other consumers.

In the image above, grass is a producer, while the rabbit and fox are consumers.

Energy flows from the producer to the consumer (the animal that eats the plant). You will notice that the flow of energy (shown by the arrows in the image above) only flows one way. An animal cannot give energy back to the plant.

Decomposers are part of the food chain as well. They are unable to make their own food. They break down waste products and dead organisms for food and then return them to the soil so they can be used again by plants.

Food Webs

Very few consumers eat only one type of food. Most organisms have more than one predator. Knowing this, a simple food chain can become a more complex food web.

A food web is a set of interconnected food chains that show how energy circulates (moves round and round) within an ecosystem.

In the image above, the grasshopper is the primary producer when it eats plants.

A secondary consumer eats animals that eat plants. The spider is a secondary consumer when it eats the grasshopper. The shrew is a secondary consumer when it eats the grasshopper.

A tertiary (or third) consumer eats animals that eat other animals. The owl is a tertiary consumer when it eats the weasel or shrew.