Food Chains and Web
Last Review/Updated: May 31, 2002
Directly or indirectly, the sun supplies all plants and animals with the energy they require to live. A food chain shows some of the ways living organisms use and transfer this energy to each other. Green plants convert sunlight into food energy, and some of this energy is passed on to animals (herbivores) that feed on green plants. These animals in turn pass some of their energy on to other animals (carnivores) that feed on them. Carnivores may pass some of their energy on to other carnivores.
A food web combines several related food chains. It shows the many kinds of relationships that exist in a natural community. For example, in the first illustration, the angler may not only catch and eat pike, he may also take perch. Similarly, pike may feed on mosquito larvae and dragonfly larvae, as well as perch. Algae and many other aquatic plants are eaten by a variety of invertebrates and fish.
Invertebrates are important in the food webs of most water and land communities. Besides herbivores and carnivores, there are many species of decomposer invertebrates that help to break down animal wastes and bodies of dead plants and animals. Without decomposers, the minerals, gases and water that make up living things would not be returned to the soil and air, where green plants again use these materials to make food.
