...Food chains

All living things need food to be active and healthy, and to grow and reproduce. Almost all plants make their own food. Animals must eat other living things to get the food they need. As we learned in Special Feature, animals are called herbivores, carnivores or omnivores based on what they eat.
Plants and animals make up links in different food chains. A food chain is made up of plants and animals that are connected because they either eat or get eaten by each other. Every plant and animal belongs to at least one food chain.
Here is an example of a wetland food chain:

The water lily is the first link. The snail eats the water lily. The crayfish eats the snail. The bullfrog eats the crayfish. The Northern water snake, which is the last link, eats the bullfrog. As each link in the food chain gets eaten, it passes some of the energy stored in its body to the next link in the chain.
Plants are the first link in every food chain, because they make their own food. The next link in a food chain is an herbivore or omnivore. These animals feed the next link in the chain, which may be another omnivore or a carnivore. The rest of the links are formed by carnivores.
The last link in a food chain is filled by an animal called a top predator. This animal usually is large and powerful. It doesn't have any natural enemies. In a wetland food chain, a top predator might be a bald eagle. In other food chains, it might be a wolf or a grizzly bear. Can you think of any others?
Very few animals eat just one kind of food. With each type of food an animal eats, it becomes a link in a different food chain. Food chains connect to form what scientists call a food web. A food web contains many plants and animals.
The picture below shows how a mallard duck can be linked to many wetland food chains. The links that form the top half of the circle are animals that might eat a mallard sometime during its life. The links that form the bottom half of the circle are plants and animals a mallard might eat sometime during its life. Each of the links around the mallard also connects to other food chains. In this way, the chains make up part of a wetland food web.