The trophic structure in a community is the feeding relationships between species in the community. It determines how energy is passed from organism to organism, like from plants to herbivores to carnivores.

Trophic structure is organized in levels. The organisms of the first trophic level are called producers. They exist at the very bottom of the trophic structure and they support all following trophic levels. They are also called autotrophs, meaning they make their own food and do not need to eat other organisms.

The organisms of all the levels after producers are called consumers, or heterotrophs, meaning they cannot make their own food and they have to eat other organisms. The first trophic level after the producers is the primary consumer. These organisms are herbivores that eat plants, algae, or autotrophic bacteria. The next trophic level is composed of secondary consumers. Secondary consumers feed on primary consumers. They are often small mammals or fish. The next level is composed of tertiary consumers. Tertiary consumers feed on secondary consumers and is often composed of larger carnivorous mammals and snakes.

Detritovores, or organisms that derive energy from dead material like animal wastes, plant litter, or dead organisms, fit in at the bottom of the trophic structure.

Trophic levels can be shown by food webs, which are more accurate than food chains because feeding relationships in an ecosystem are rarely simple. The following is an example of a food web:
external image soil_food_web%5BHR%5D.jpg
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