Extinction is the process by which a species, genus, or family, becomes extinct — no longer existing and living in the world. It is the abolition and annihilation of something that previously existed in the world. In the case of biology, it refers specifically to the end of an evolutionary line, or a branch on the tree of life.
The actual moment of extinction is considered to be when the last individual representative of a species or group is no longer living. But functional extinction can occur considerably earlier than that — as the result of loss of genetic diversity, range, and/or the ability for a population to breed and recover.
Most types of life, especially animals, are closely tied to their ecological niches and environments. With a loss of their living environment, and its accompanying species, extinction is almost inevitable for many types of life. Species diversification and emergence typically doesn’t occur in these circumstances, it usually happens within healthy ecosystems. The long-period of time that follows large extinction events when no new species emerge is referred to as a dead zone .