| Words | Definitions |
| biosphere | the part of the earth's crust, waters, and atmosphere that supports life |
| carrying capacity | The maximum population of a particular organism that a given environment can support |
| commensalism | A symbiotic relationship between two organisms of different species in which one derives some benefit while the other is unaffected. |
| community | A group of plants and animals living and interacting with one another in a specific region under relatively similar environmental conditions. |
| consumer | A heterotrophic organism that feeds on other organisms in a food chain. |
| ecology | the branch of biology dealing with the relations and interactions between organisms and their environment, including other organisms. |
| ecosystem | a system formed by the interaction of a community of organisms with their environment |
| habitat | the natural environment of an organism |
| limiting factor | an environmental factor that tends to limit population size |
| mutualism | a relationship between two species of organisms in which both benefit from the association. |
| niche | The function or position of an organism or population within an ecological community. |
| parasitism | A symbiotic relationship in which one organism (the parasite) benefits and the other is harmed |
| population | All the organisms that constitute a specific group or occur in a specified habitat. |
| producer | an organism, as a plant, that is able to produce its own food from inorganic substances. |
| symbiosis | the living together of two dissimilar organisms, as in mutualism, commensalism, amensalism, or parasitism. |
| predator | An organism that lives by preying on other organisms |
| prey | an animal hunted or seized for food |
| competition | the struggle among organisms, both of the same and of different species, for food, space, and other vital requirements |
| chemosyntesis | the synthesis of organic compounds within an organism, with chemical reactions providing the energy source. |
| food web | a series of organisms related by predator-prey and consumer-resource interactions; the entirety of interrelated food chains in an ecological community. |
| energy pyramid | a depiction of the amount of energy in each trophic level of an ecosystem |
| food chain | a series of organisms interrelated in their feeding habits, the smallest being fed upon by a larger one, which in turn feeds a still larger one |
