ecology (n.) Look up ecology at Dictionary.com
1873, oecology, "branch of science dealing with the relationship of living things to their environments," coined in German by German zoologist Ernst Haeckel (1834-1919) as Ökologie, from Greek oikos "house, dwelling place, habitation" (see villa) + -logia "study of" (see -logy). In use with reference to anti-pollution activities from 1960s.
eco- Look up eco- at Dictionary.com
word-forming element referring to the environment and man's relation to it, abstracted from ecology, ecological; attested from 1969.
ecologist (n.) Look up ecologist at Dictionary.com
1893, see ecology + -ist.
ecological (adj.) Look up ecological at Dictionary.com
1899, see ecology + -ical. Related: Ecologically.
freak (n.1) Look up freak at Dictionary.com
1560s, "sudden and apparently causeless turn of mind," of unknown origin. Perhaps it is from a dialectal survival of a word related to Middle English friken "to move nimbly or briskly," from Old English frician "to dance" [OED, Barnhart]. There is a freking attested in mid-15c., apparently meaning "capricious behavior, whims." Or perhaps from Middle English frek "eager, zealous, bold, brave, fierce" (see freak (n.2)).

Sense of "capricious notion" (1560s) and "unusual thing, fancy" (1784) preceded that of "abnormally developed individual or production" (first in freak of nature, 1839, which was later popular in variety show advertisements for bearded ladies, albinos, etc.; compare Latin lusus naturæ, which was used in English from 1660s). As "drug user," attested from 1945. The sense in health freak, ecology freak, etc. is attested from 1908 (originally Kodak freak, a camera buff). Freak show attested from 1887.
mesic (adj.) Look up mesic at Dictionary.com
1926, in ecology sense, from Greek mesos "middle" (see meso-) + -ic. From 1939 in physics (from meson).
hydric (adj.) Look up hydric at Dictionary.com
1796 as a term in chemistry, "of or containing hydrogen." From 1918 in ecology, "having plentiful water;" see hydro- + -ic.
bionomics (n.) Look up bionomics at Dictionary.com
"science of organic evolution; ecology," 1888, coined by Scottish biologist Patrick Geddes (1854-1932) from Greek bio- (see bio-) + nomos "managing," from nemein "manage" (see numismatic).
environment (n.) Look up environment at Dictionary.com
c. 1600, "state of being environed" (see environ (v.) + -ment); sense of "the aggregate of the conditions in which a person or thing lives" first recorded 1827 (used by Carlyle to render German Umgebung); specialized ecology sense first recorded 1956.
greens (n.) Look up greens at Dictionary.com
c. 1400, "vegetables;" 1690s, "freshly cut branches used for decoration," from green (n.). Meaning "ecology political party" first recorded 1978, from German die Grünen (West Germany), an outgrowth of Grüne Aktion Zukunft "Green Campaign for the Future," a mainly anti-nuclear power movement, and/or grüne Listen "green lists" (of environmental candidates). Green (adj.) in the sense of "environmental" is attested in English from 1971; Greenpeace, the international conservation and environmental protection group, is from 1971.
sustainability (n.) Look up sustainability at Dictionary.com
1907, in reference to a legal objection, from sustainable + -ity. General sense (in economics, agriculture, ecology) by 1972.
Sustainability is defined as a requirement of our generation to manage the resource base such that the average quality of life that we ensure ourselves can potentially be shared by all future generations. ... Development is sustainable if it involves a non-decreasing average quality of life. [Geir B. Asheim, "Sustainability," The World Bank, 1994]