Trophic Levels

Trophic levels describe the various stages within ecological food chains or webs. Examples of trophic levels, all of which will be described below, are primary producers, primary consumers or herbivores, and secondary and higher-level consumers, or predators.

Food webs are based on the productivity of photosynthetic organisms, such as blue-green bacteria, algae, and plants. These are autotrophic organisms, which are capable of fixing some of the diffuse energy of solar radiation into simple organic compounds. This fixed energy can then be utilized by the primary producers to metabolically synthesize a diverse array of biochemicals and to support the growth of these organisms.

The solar energy fixed by photosynthesis is the energetic base that all heterotrophic organisms utilize to achieve their own productivity. Heterotrophic organisms include any animals and microorganisms that feed on the living or dead biomass of plants, or that of other heterotrophs. Heterotrophs include herbivores that feed directly on autotrophs, carnivores that feed on other animals, detritivores that feed on dead biomass, and omnivores that feed on any or all of the above.

Therefore, the food web is a diverse assembly of organisms that are ecologically linked through their feeding relationships, and is ultimately based on the fixation of solar radiation through photosynthesis.

All organisms eventually die, and detritivores are a class of organisms that feed on their dead bodies. Actually, detritivores can themselves be divided into a food web, based on the feeding relationships among the species. In this sense, primary detritivores feed directly on the dead biomass, while secondary detritivores feed on these direct consumers of detritus.