Trophic Levels

The living components of an ecosystem are divided into two classes the autotrophs and the heterotrophs. Autotrophs are mainly photosynthetic organisms such as plants, and algae, which use light energy to manufacture their own food. These organisms are known as primary producers and provide the organic material required by the heterotrophs. Heterotrophs are divided into several trophic levels, which describe how they feed. The first trophic level is the primary consumers or herbivores, these animals only eat living plants, and the primary consumers are eaten by the secondary consumers, which are the carnivores and parasites. When the organisms in an ecosystem die their bodies are fed on by the decomposers, which are bacteria, fungi and various small animals which break down the dead organic material.

These organisms in an ecosystem make up the food chain and their interactions regulate the flow of energy in the ecosystem. Since most organisms have more than one source of food the food chain is an inaccurate way to describe the feeding interactions in an ecosystem the more accurate way is a food web which shows how one organism may have many food sources and may be a food source to many different animals.

The suns energy is essential to all life in an ecosystem and is harnessed by the photosynthetic organisms, which are then eaten by the primary consumers and secondary consumers which are decomposed by the decomposers. At each trophic interaction energy is lost, usually in the form of heat, this energy is then radiated back into space. Plants are only able to harness about 1 percent of the energy which reaches their leaves from the sun, this energy is then stored until an animal eats the plant using the energy to maintain body heat and produce tissue, this loss of energy occurs each time an organism is eaten or decomposed by another organism.