A food chain is the sequence of who eats whom in a biological community to obtain nutrition.

1. A food chain starts with the primary ______________________________________ source, usually the sun or deep _______________________________ vents.
2. The next link in the chain is an organism that make its own food from the primary energy source -- an example is plants that make their own food from sunlight (using a process called ______________________________________). These organisms are called autotrophs or primary producers.
3. Next come organisms that eat autotrophs; these organisms are called herbivores or primary ______________________________________ -- an example is a rabbit that eats ______________________________________.
4. The next link in the chain is animals that eat herbivores; these are called secondary consumers -- an example is a snake that eats rabbits.
5. In turn, these animals are eaten by tertiary consumers -- an example is an owl that eats ______________________________________.
6. The tertiary consumers are are eaten by quaternary consumers -- an example is a hawk that eats owls.
7. Each food chain end with a ______________________________________ predator, an animal with no natural enemies (some examples are alligators, hawks, and polar ______________________________________).
8. When any organism dies, it is eventually eaten by ______________________________________ (like vultures, worms and crabs) and broken down by decomposers (mostly bacteria and fungi), and the exchange of energy continues.

The ______________________________________ in a food chain show the flow of energy, usually from the sun to a top predator. As the energy flows from organism to organism, energy is ______________________________________ at each step.

Some organisms' position in the food chain can vary as their diet differs. For example, when a bear eats berries, the bear is acting as a primary consumer. When a bear eats a plant-eating rodent, the bear is functioning as a secondary consumer. When the bear eats salmon, the bear is functioning as a tertiary consumer (this is because salmon is a secondary consumer, since salmon eat herring that eat zooplankton that eat phytoplankton, that make their own energy from sunlight). Think about how people's place in the food chain varies - often within a single ______________________________________.