Everything Eats Something

A food web is the network of feeding relationships in an ecosystem. Unlike the simple food chains taught in school — grass to rabbit to fox — real ecosystems are tangled webs where most species eat multiple things and are eaten by multiple predators.

At the base of every food web are primary producers — organisms that convert sunlight or chemical energy into biological matter. On land, these are plants. In oceans, phytoplankton fill this role, generating roughly half of Earth's oxygen while feeding the entire marine food chain.