From Citizendium, the Citizens' Compendium
- Biology : The science of life — of complex, self-organizing, information-processing systems living in the past, present or future.
- Ecosystem : A space in which multiple biological species interact.
- Carrying capacity : Add brief definition or description
- Ecological footprint : The sum of all resource-using or waste-producing activities of a biological unit, if converted to units of biologically productive land.
- Urban ecology : The study of ecological relationships between humans and other organisms in urban environments.
- Economy : (i) A complex interactive system that is engaged in the production and distribution of goods and services.; (ii) the careful use of money or other resources.
- Metabolism : The modification of chemical substances by living organisms.
- Natural environment : A term that encompasses all living and non-living things occurring naturally on Earth or some region of Earth.