environment

In ecology, the sum of conditions affecting a particular organism, including physical surroundings, climate, and influences of other living organisms. Areas affected by environmental issues include the biosphere and habitat. In biology, the environment includes everything outside body cells and fluid surrounding the cells. This means that materials enclosed by part of the body surface that is ‘folded in’ are, in fact, part of the environment and not part of the organism. So the air spaces in human lungs and the contents of the stomach are all part of the environment and not the organism, using these terms correctly. Ecology is the study of the way organisms and their environment interact with each other. Important processes in biology involve the transfer of material between an organism and its environment in exchanges of gases and food, for example during nutrition, photosynthesis, or respiration.

In common usage, ‘the environment’ often means the total global environment, without reference to any particular organism. In genetics, it is the external influences that affect an organism's development, and thus its phenotype.