| Term | Definition |
| ecology | the study of all interrelatonships between organisms and their environment |
| biosphere | the portion of earth that supports life |
| biotic factor | any living factor in an organism's environment |
| abiotic factor | any nonliving factor in an organism's environment |
| population | all the organisms of the same species that live in a given area |
| biological community | a group of interacting populations in a given area |
| ecosystem | a biological community and all the abiotc factors that affect it |
| biome | a large group of ecosystems that share the same climate |
| habitat | an area where an organism lives |
| niche | the role an organism plays in its environment |
| predation | one organisms that kill and eat other organisms |
| symbiosis | the close relationship that exists when two or more species live together |
| mutualism | when two or more species live together and benefit from each other |
| commensalism | a relationship where one organism benefits and the other is neither helped or harmed |
| parasitism | a relationship where one organism benefits and the other is harmed |