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The Ecosystem : An Inter-acting Community
An animal which depends upon one type of food will use energy in finding its food. Also, if its food becomes scarce for some reason, the animal may starve. Animals such as the koala bear, which only feeds on the bark and leaves of one type of eucalyptus tree, and the cinnabar moth caterpillars, which only eat the leaves of the ragwort plant, are restricted to the areas where these plants grow.
Most animals are able to eat a variety of foods. A successful herbivore or carnivore is an animal which is able to change its diet and eat what is available at any particular time.
A successful predator will also hunt prey which is easy to catch, such as an old or injured animal. It would be a waste of energy to hunt and chase a prey for a long time.
An Antarctic Food Web
Since most animals eat a variety of food, a food chain does not really give us enough information about an ecosystem. Ecologists often show the feeding relationships between animals as food webs. A food web is a better way of showing the feeding relationships between all of the organisms living in the community.