Kenneth G. Wilson (1923). The Columbia Guide to Standard American English. 1993.
ecology, environment (nn.)
Ecology (pronounced ee-KAHL-uh-jee) is the system of relationships between biological organisms and their environment; it also means the study of such matters. The ecology of a particular plant or animal is an account of its relationships with the physical environment in which it occurs. The environment is the full range of conditions and circumstances in which biological organisms live. So, ideally at least, ecology is both the system itself (ecosystempronounced EE-ko-sis-temis the blend coined to make explicit this meaning) and the study of it, and environment is the detailed locus in which such a system operates. Lately, however, the vogue of these subjects increasingly has caused the two words to be used interchangeably to mean the full range of circumstances in which organisms, especially human beings, exist. Such uses are now Standard, but much Edited English still tries to preserve the distinction between ecology and environment, particularly in technical contexts; you would do well to try to preserve it too. See also GOVERNMENT.