Light energy from the sun flows into an ecosystem and is used by organisms who occupy specific trophic levels defined by their energy source.

1. Producers capture sunlight and transform it into food by photosynthesis.

2. Primary consumers are herbivores that eat producers.

3. Secondary consumers are carnivores that eat herbivores.

4. Tertiary consumers are top carnivores, eating food at lower trophic levels.

Other consumers include decomposers and detritivores, as well as parasites.