| Adaptation | an alteration in the structure of an organism that results from natural selection and by which the organism becomes better fitted to survive in its environment. |
| Autotroph | An organism capable of producing its own food |
| Biosphere | The part of the planet that contains living organisms |
| Biotic factor | Living factor (organism’s influence on another organism) |
| Carnivore | An animal that feeds on animals only |
| Climatic | Factors relating to long term weather conditions |
| Competition | When two or more organisms fight or struggle for a resource that is in short supply. |
| Conservation | The wise management of the environment |
| Consumer | An organism that cannot make its own food |
| Contest competition | An active physical confrontation between two organisms in which only one wins the resource |
| Decomposers | Micro-organisms and other organisms that return nutrients to the environment by decay. |
| Denitrification | The conversion of nitrates into atmospheric nitrogen |
| Ecology | The study of the interaction between organisms and their environment |
| Ecosystem | A community of living organisms interacting with one another and their environment. |
| Edaphic | Factors relating to the soil [which affects the distribution of organisms in a (terrestrial) ecosystem] |
| Fauna | Animals |
| Food Chain | Feeding relationship between organisms in which energy is transferred. |
| Food Pyramid | Diagram showing the correct number of servings of different foods to have a balanced diet |
| Food Web | Two or more interconnected food chains or more than one species at each trophic level |
| Grazing Food Chain | Feeding relationship between organisms in which energy is transferred. |
| Habitat | The place where an animal or a plant lives |
| Herbivore | An animal that only eats plants |
| Heterotroph | An animal that obtains food from other organisms |
| Interdependence | |
| Niche | The functional role of an organism (in an ecosystem) |
| Nitrification | The process of converting ammonia into nitrites and/or nitrites to nitrates |
| Nitrogen fixing | The conversion of nitrogen into nitrates. |
| Omnivore | An animal that eats both animals and plants. |
| Parasitism | A situation in which one organism lives on or in a second species, feeding on it and causing it harm. |
| Pollution | The harmful addition to the environment (by humans) |
| Population | The numbers of a particular species [in a particular area or ecosystem] |
| Producer | An organism which makes its own food |
| Pyramid of Numbers | The numbers of organisms at each trophic level. |
| Scramble competition | A confrontation which results in each organism getting some of the resource |
| Tertiary Consumer | An organism which feeds on the secondary producer. |
| Trophic Level | The position of an organism in a food chain or feeding level |