Potencial for a specie to increase in number [by evolution]
Proliferation of organisms that are able to reproduce and survive [in any given environment]
Freeman, S., Quillin, K., & Allison, L. A. (2014). Biological science fifth edition. Harlow, UK: Pearson Education.
Nature Education. (2014). Genetic Mutation. Retrieved April 04, 2016, from http://www.nature.com/scitable/ebooks/genetic-variation-and-evolution-16553748/126455454#bookContentViewAreaDivID