| Term | Definition |
| ecology | study of organisms and their interactions with the environment |
| biotic factors | all living things in an environment |
| abiotic factors | physical and chemical conditions in an environment |
| population | group of individual organisms of the same species living in the same area |
| community | All organisms living in the same area |
| ecosystem | all abiotic and biotic factors in a given area |
| biosphere | the total of all ecosystems together |
| habitat | specific environment in which an organism lives |
| tropics | region of Earth between 23.5 N and 23.5 S latitude |
| polar zones | above the Arctic circle and the Antarctic circle |
| temperate zones | area between the polar zones and tropics |
| biome | terrestrial ecosystem covering a large portions of Earth |
| tropical rain forest | wet and hot, highly diverse life, soil poor |
| savanna | grasslands with scattered trees |
| desert | less than 30 cm or rain |
| chaparral | temperate with dense evergreen shrubs, fire is important |
| temperate grasslands | rich soil, thick grass; prairies |
| temperate deciduous forest | trees often drop leaves in fall/winter |
| coniferous forest (taiga) | often cold winters, dense evergreen trees like firs |
| tundra | cold, permafrost, mostly mosses, short grasses |
| phytoplankton | microscopic algae and cyanobacteria in photic zone |
| zooplankton | microscopic animals in photic zone |
| photic zone | upper zone of water where light penetrates |
| aphotic zone | aquatic environment where there is no light |
| benthic zone | the bottom of any aquatic ecosystem (sand, rock) |
| estuary | where fresh and salt water mix; great breeding grounds |
| pelagic zone | all water above the benthic zone |
| intertidal zone | area between low and high tides |
| neritic zone | ocean area from shore to continental shelf |
| oceanic zone | vast ocean beyond continental shelf |
| coral reefs | most diverse aquatic ecosystem, in neritic zone |
| hydrothermal vents | hot water eruptions on ocean floor; exotic lifeforms |