Consumer (food chain)

A consumer obtains organic material by feeding on other organisms or their products. A consumer feeding on primary producers is a primary consumer; one feeding on primary consumers is a secondary consumer. These names describe positions in a food chain, rather than permanent labels for a species.

A decomposer breaks down dead organic material and absorbs products of that breakdown; many bacteria and fungi perform this role. Decomposers connect detritus from different trophic levels to material recycling, so placing all decomposers at one final step of every food chain is misleading. See Clark, Douglas and Choi, Biology 2e, 46.1: grazing and detrital food webs.

An omnivore feeds on both primary producers and consumers. Its mixed diet explains why a trophic level need not be a whole number or a fixed label throughout an organism's life.