Food Chain/Food Web

The interactions that take place among biotic and abiotic factors lead to transfers of energy and matter. Every species has a particular role, or niche, in an ecosystem. Autotrophs are organisms that use energy from the sun or chemical energy to produce their own food. Autotrophs are also known as producers.

Heterotrophs are organisms that depend on other organisms for food. Because they consume rather than make food, heterotrophs are also known as consumers. A heterotroph that eats only plants is known as an herbivore. Heterotrophs that eat meat other heterotrophs are called carnivores. Omnivores are heterotrophs that eat both plants and animals. Also,scavengers are heterotrophs that feed on animals that are already dead. For example, vultures clean up the bodies of dead animals. Decomposers are consumers that break down dead or decaying organisms and absorb nutrients such as carbon and nitrogen from them. Decomposers are mainly bacteria and fungi that convert dead matter into gases such as carbon and nitrogen to be released back into the air, soil, or water. Decomposers are necessary since they recycle the nutrients to be used again by producers. Without decomposers, the earth would be covered in trash.

Food chains and food webs are pictures that show relationships among organisms. Each link in a food chain or web represents a feeding step or trophic level. The arrows in food chains and food webs show the direction of energy flow. That is,arrows point to the organism that receives the energy. Only about 10% of energy passes to the next level of a food chain. At each level, the other 90% of energy is “lost” to the environment as heat. Most food chains are only 3-4 links long because by the last link, only a small portion of the original energy is left.

A food chain represents one possible path for the transfer of energy in an ecosystem. A food web shows many possible feeding relationships.