How does energy flow in a food chain?

Energy flows in a food web from primary producers to many consumers. The food chain is the organization of organisms in a single direction from producer to high level consumers. The food chain (and energy flow) follows this order:

Producers > Primary Consumer > Secondary Consumer > Tertiary Consumer

At the bottom of the food web are producers, which have a unique ability to transform sunlight into ATP energy units. Autotrophs such as green algae and plants convert sunlight into energy and serve as food sources for primary consumers.

Primary consumers are organisms that eat the primary producers, thereby transferring the energy and nutrients from the produce level to the consumer level. One example of a primary consumer is a mouse, which eats things like fruit, seeds, and grains.

A secondary level consumer is an organism that eats a primary consumer. In this case, a secondary level consumer may be a snake. In this example, a snake that eats a mouse will transfer the energy and nutrients from the mouse (originally from the fruits, seeds, and grains) to the secondary level.

Finally, the tertiary level consumers are the highest stop on the food chain. These organisms eat secondary level consumers. In this example, a tertiary level consumer may be a hawk who eats a snake, thereby transferring the energy from the secondary level to the tertiary level.

This entire example shows how the energy from the sun was converted by primary producers (plants) and moved through the food chain from a mouse to a snake to a hawk - thus, the energy moved from the sun to the primary producer, to the primary consumer, to the secondary consumer, and to the final tertiary consumer.

It is important to note that, when the tertiary consumer dies, the energy and nutrients will be returned to the ecosystem through decomposition. At this level, decomposers (such as worms and fungi) will break down the organic matter to the chemical level. The chemicals from this process will be returned into the soil and will support the growth of primary producers to begin the process all over again.