| Term | Definition |
| Abiotic | The nonliving part of the environment |
| Biotic | The living part of the environment |
| Biosphere | The part of Earth where life exists |
| Population | A group of organisms of the same species living in the same area |
| Community | All the populations of species that live and interact in the same habitat |
| Ecology | The study of the interactions of living organisms with each other and the environment |
| Ecosystem | A community of organisms and their abiotic environment |
| The Five Levels Of Environmental Organization | Organism, Population, Community, Ecosystem, Biosphere |