Ecology (from Ancient Greek __ οἶκος ( _oîkos ) 'house', and __ -λογία
( -logía )_ 'study of') is the study of the relationships among living
organisms, including humans, and their physical environment. Ecology considers
organisms at the individual, population, community, ecosystem, and biosphere
level. Ecology overlaps with the closely related sciences of biogeography,
evolutionary biology, genetics, ethology, and natural history. Ecology is a
branch of biology, and it is not synonymous with environmentalism.