The food chain illustrates how energy is transferred from one organism to another as a repeating cycle. Several food chains, in turn, compose a single food web for a community. A food chain is a simpler way to describe the steps energy takes as it flows through an ecosystem. The chain begins with producers, such as plants and photosynthetic bacteria. These organisms are able to produce a lot of food by using sunlight as fuel. Consumers occupy the next links of the chain. Unlike producers, they obtain energy by eating other organisms. Primary consumers, or herbivores, refer to organisms that mainly eat plants. Secondary, tertiary, and quaternary consumers either eat other consumers (carnivores) or a mixture of producers and consumers (omnivorous). An organism further along the chain eats the animals in preceding links. The top-level consumer is also called the apex predator. Regardless of which link an organism occupies, when it dies its decaying biomatter is used by decomposers, such as fungi and many invertebrates, to regain the last of its energy. By breaking down their dead matter and wastes, decomposers also return nutrients to the environment to be used by producers anew. If you’re curious about how the flow of energy passes from organism to organism, you can check out our food chain diagram and use it as a handy, detailed reference for your life science studies.