Date Published: September 22, 2004
Publisher: Public Library of Science
Partial Text: Strictly defined, evolution is a change in the gene pool, or total set of genes, of a given population over time. Genetic changes that increase the fitness of an organism—that is, increase survival or fertility—are more likely to be retained, through natural selection, and passed on to succeeding generations. In the classic case of Darwin’s finches, different ecological niches exerted different selective pressures on an original population, and resulted in 14 different species, each sporting a beak uniquely adapted to harvesting particular available food sources.