| Term | Definition |
| Terrestrial | land |
| Aquatic | water |
| Freshwater Ecosystems | aquatic ecosystems with less than 1% salt content |
| Marine Ecosystems | aquatic ecosystems with at least 3.5% salt content |
| Food Chain | The path of food energy from the Sun, to the producer, then transferred to a series of consumers. |
| Food Web | Overlapping food chains with different pathways for the flow of food energy in an ecosystem. |
| Producer | An organism that is capable of performing photosynthesis, transforming energy from the Sun, and using carbon dioxide and water to make food. |
| Consumer | An organism that must consume other organisms for nutrients. |
| Herbivore | An organism that consumes only plants. |
| Carnivore | An organism that consumes other animals. |
| Omnivore | An organism that consumes both animals and plants. |
| Parasite | An organism that survives on a host organism and causes harm to the host. |
| Host | An organism that is used by another organism for nutrients, shelter, or transport; it is harmed by the relationship. |
| Predator | An organism that hunts for its food. |
| Prey | An organism that is hunted by other organisms for food. |
| Decomposer | Organisms such as bacteria and fungi that break down the remains of dead plants and animals, without need for internal digestion. |
| Detritivore | Organisms that do not kill their own food, but eat dead or decaying plants or animals. |
| -troph | an organism that gets nourishment from a (specified) source |
| Trophic Level | The position an organism occupies on the food web. |
| Autotroph | An organism that produces its own food, such as a plant. |
| Heterotroph | An organism that must use other organisms for food, such as animals. |
| Energy Pyramid | A diagram that shows the trophic levels of organisms in a food web. |
