Extinction is the state or process of a species, family, or larger group being or becoming extinct. In modern usage, the word refers to "a terminal event in the history of a population, species, or higher taxon" (Keller and Lloyd, 1992). Extinction of a species leaves an empty niche. It can happen if the niche or habitat vanishes or if the fitness is not high enough.
- Wikipedia link for extinction
- Evelyn Fox Keller and Elisabeth A. Lloyd, "Keywords in Evolutionary Biology", Harvard University Press, 1992