Speciation

Members of a species breed at a rate that produces more offspring than can be supported by a habitat. Some of the offspring do not reach maturity because of starvation, predation or disease. Those who inherit features that enable them to survive to breeding age are said to be better adapted and they are more likely to pass on the genes that have made them successful. This is the basis of natural selection and evolution.

The formation of a new species occurs very slowly through natural selection, where the best adapted individuals survive and the least well adapted ones die off. Over a very long time the founder species becomes extinct and a new one has evolved. The usual cause of speciation is geographic isolation but anything that can cause reproductive isolation would have the same effect.

Plate tectonics can create geographical barriers as a result of Earth movements such as an earthquake changing the course of a river. If this crosses the habitat of a species, the population can be split into two sub-groups, reproductively isolating them. Random mutations in the genes and slightly different environmental conditions cause each sub-group to evolve differently. Eventually, natural selection in the two groups can produce new genotypes and phenotypes. They eventually reach the point where it would be impossible for them to interbreed successfully, should the isolating feature ever disappear. Perhaps the ultimate isolation is continental drift which splits whole continents apart. There is plenty of evidence in the fossil record of speciation, including human evolution.

Take this quiz and test yourself on speciation - the formation of a new species from a founder species.