A community of interacting organisms and their physical environment.
A species that spreads widely and causes ecological or economic harm.
A species that is indigenous to a region: The species lives there or has lived there historically, but was not introduced there from elsewhere.
A species that has not historically occurred in an ecosystem, but does occur as a result of its introduction to that ecosystem. Also called alien species, exotic species, or introduced species.
The area naturally occupied by an individual, population, or species.
A group of individuals, usually identifiable by a set of distinctive features, with a unique evolutionary history. Classically, the members of a species can interbreed only with each other to produce fertile offspring.