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Natural selection is the differential survival and reproduction of individuals due to differences in phenotype.It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations.
Evolution is the change in the heritable characteristics of biological populations over successive generations. [1] [2] 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. [3]
Professor of biology Jerry Coyne sums up biological evolution succinctly: [3]. Life on Earth evolved gradually beginning with one primitive species – perhaps a self-replicating molecule – that lived more than 3.5 billion years ago; it then branched out over time, throwing off many new and diverse species; and the mechanism for most (but not all) of evolutionary change is natural selection.
It defines evolution as the change in allelic frequencies within a population caused by genetic drift, gene flow between sub populations, and natural selection. Natural selection is emphasised as the most important mechanism of evolution; large changes are the result of the gradual accumulation of small changes over long periods of time. [39] [40]
Charles Darwin in 1868. Darwinism is a term used to describe a theory of biological evolution developed by the English naturalist Charles Darwin (1809–1882) and others. The theory states that all species of organisms arise and develop through the natural selection of small, inherited variations that increase the individual's ability to compete, survive, and reproduce.
Darwin's theory of evolution by natural selection, with its tree-like model of branching common descent, has become the unifying theory of the life sciences. The theory explains the diversity of living organisms and their adaptation to the environment.
The idea of evolution by natural selection was proposed by Charles Darwin in 1859, but evolutionary biology, as an academic discipline in its own right, emerged during the period of the modern synthesis in the 1930s and 1940s. [19] It was not until the 1980s that many universities had departments of evolutionary biology.
Fisher's fundamental theorem of natural selection is an idea about genetic variance [1] [2] in population genetics developed by the statistician and evolutionary biologist Ronald Fisher. The proper way of applying the abstract mathematics of the theorem to actual biology has been a matter of some debate, however, it is a true theorem.