Speciation is the evolutionary process by which populations evolve to become distinct species. The biologist Orator F. Cook coined the term in 1906 for cladogenesis, the splitting of lineages, as opposed to anagenesis, phyletic evolution within lineages. Charles Darwin was the first to describe the role of natural selection in speciation in his 1859 book On the Origin of Species. He also identified sexual selection as a likely mechanism, but found it problematic.
African pygmy kingfisher, showing coloration shared by all adults of that species to a high degree of fidelity.
Cichlids such as Haplochromis nyererei diversified by sympatric speciation in the Rift Valley lakes.
Rhagoletis pomonella, the hawthorn fly, appears to be in the process of sympatric speciation.
Gaur (Indian bison) can interbreed with domestic cattle.
Evolution is the change in the heritable characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, resulting in certain characteristics becoming more or less common within a population over successive generations. The process of evolution has given rise to biodiversity at every level of biological organisation.
White peppered moth
Black morph in peppered moth evolution
Male moor frogs become blue during the height of mating season. Blue reflectance may be a form of intersexual communication. It is hypothesised that males with brighter blue coloration may signal greater sexual and genetic fitness.
The common garter snake has evolved resistance to the defensive substance tetrodotoxin in its amphibian prey.
