| Term | Definition |
| Producer | An organism that makes its own food through photosynthesis |
| Consumer | An organism that eats other living things for energy |
| Ecology | The study of the relationship between living organisms and the physical environment |
| Cellular Respiration | The process of breaking down sugar in a cell to release energy |
| Decomposer | Organisms that eat dead organisms and waste, and recycle them back into the environment |
| Food Web | A diagram showing all feeding relationships in an ecosystem |
| Food Chain | A diagram showing one particular example of feeding relationships in an ecosystem |
| Trophic Level | A feeding level in a food chain |
| Organism | A living thing |
| Prey | An animal that is hunted for food |
| Predator | An animal that hunts and eats another animal |
| Fluctuate | To rise and fall |
| Population | A group of individuals of one species living in an area |
| Energy Pyramid | A diagram that shows the available energy at each feeding level in an ecosystem |
| Carrying Caapacity | The largest population an ecosystem can support over time |
| Limiting Factor | An environmental factor that prevents a population from increasing |
| Symbiosis | A close relationship between species where at least one organism benefits |
| Mutualism | A symbiotic relationship in which both organisms benefit |
| Commensalism | A symbiotic relationship in which one organism benefits and one is unaffected |
| parasitism | A symbiotic relationship in which one organism benefits and the other is harmed |
| Parasite | The organism in parasitism that benefits |
| Host | The organism in parasitism that is harmed |
