Ecology - A branch of science that deals with the relation of organisms to one another and their physical environment.⏎
Endemic - The baseline level of disease usually present in a community.⏎
Exoskeleton - An external skeleton that protects and supports an organism, in contrast to an internal endoskeleton.⏎
Epidemic - An often sudden increase in the level of disease in a specific population over a given period of time.⏎