Speciation: how new species form

A species is usually defined as a group of organisms that can interbreed in nature and produce fertile offspring. Speciation, the formation of new species, happens when populations of one species become reproductively isolated, so that little or no gene flow passes between them. The populations then change independently through natural selection, genetic drift, and mutation, until they rarely or no longer interbreed successfully. The boundary is not always sharp: some closely related species can still occasionally produce hybrids. In allopatric speciation, a physical barrier such as a mountain range, a river, or an ocean separates populations; the many species of Galapagos finches descended from ancestors that reached the islands and adapted to different food sources. In sympatric speciation, new species form without a physical barrier, for example when some members of a population start breeding at a different time or in a different habitat, or, commonly in plants, when an error in cell division doubles the number of chromosomes. Reproductive barriers include differences in mating times, courtship behaviors, or body structures, and hybrids that are usually infertile, like the mule, the offspring of a horse and a donkey. Speciation can happen gradually over long periods, or in relatively quick bursts separated by long stable periods, a pattern called punctuated equilibrium.

This explanation is AI-generated and can occasionally be wrong. 🚩 Report