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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.
Controversy exists as to whether Charles Darwin recognized a true geographical-based model of speciation in his publication On the Origin of Species. [5] In chapter 11, "Geographical Distribution", Darwin discusses geographic barriers to migration, stating for example that "barriers of any kind, or obstacles to free migration, are related in a close and important manner to the differences ...
On the Origin of Species (or, more completely, On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life) [3] is a work of scientific literature by Charles Darwin that is considered to be the foundation of evolutionary biology. It was published on 24 November 1859. [4]
However, speciation has also a macroevolutionary aspect, because it produces the interspecific variation species selection operates on. [4] Another macroevolutionary aspect of speciation is the rate at which it successfully occurs, analogous to reproductive success in microevolution. [2]
Polyploid speciation, which involves changes in chromosome number, is a more common phenomenon, especially in plant species. Polyploidy is a mechanism that has caused many rapid speciation events in sympatry because offspring of, for example, tetraploid x diploid matings often result in triploid sterile progeny. [257]
Genetics and the Origin of Species has two main points to make. The first is that speciation is a genuine problem that must be explained by the theory of evolution. In nature, there is not a single population of organisms separated from each other by small variations. Instead, the natural world is divided into species, each with its own limited ...
Origin of the prostate gland and a pair of holes opening to the columella and nearby shrinking jaw bones; new eardrums stand in front of the columella and Eustachian tube. The skin becomes hairy, glandular (glands secreting sebum and sweat ) and thermoregulatory.
A prerequisite for natural selection to result in adaptive evolution, novel traits and speciation is the presence of heritable genetic variation that results in fitness differences. Genetic variation is the result of mutations, genetic recombinations and alterations in the karyotype (the number, shape, size and internal arrangement of the ...