Compare and contrast a food chain and a food web.

Both a food chain and a food web show the transfer of energy through an ecosystem, from autotrophs to final consumers. However, they have a number of differences. A food chain only shows one path of energy transfer, whereas a food web shows the interactions of all the energy pathways in the ecosystem. Moreover, a food chain only has one specie occupying each trophic level, compared to a food web where each trophic level can have multiple organisms and each organism can occupy multiple trophic levels.For example, in a food chain a primary consumer may be earthworms, however in a food web the primary consumers can be earthworms and birds, where birds also feed on earthworms and therefore are a secondary consumer too.