Isolation results in speciation through many evolutionary factors. There are four main types of isolation mechanisms: geographical, anatomical, temporal, and behavioral. Geographical isolation occurs due to physical boundaries, such as mountain ranges or rivers. Anatomical isolation occurs when species cannot physically mate or their offspring cannot survive/infertile, for their genitalia/gametes are not compatible. Temporal isolation occurs when species do not interbreed because they breed at different times. Behavioral isolation occurs when there is a difference in courtship or other behavior prevents mating. Biogeographical isolation is a mechanisms for evolution. A single species can evolve into several different species. Species evolve in order to fill a unique niche, the role an organism plays in the environment in which it lives.