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In negative frequency-dependent selection, the fitness of a phenotype or genotype decreases as it becomes more common. This is an example of balancing selection. More generally, frequency-dependent selection includes when biological interactions make an individual's fitness depend on the frequencies of other phenotypes or genotypes in the ...
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]
The underlying theme of the essay is the need to teach biological evolution in the context of debate about creation and evolution in public education in the United States. [5] The fact that evolution occurs explains the interrelatedness of the various facts of biology, and so makes biology make sense. [ 6 ]
He wrote out his ideas in an 1842 "pencil sketch", then in an essay written in 1844. He discussed transmutation with his friend Joseph Dalton Hooker, [1] who read the essay in 1847. After turning his attention to biology and completing eight years of work on barnacles, Darwin intensified work on his theory of species in 1854.
Fisher's principle is an evolutionary model that explains why the sex ratio of most species that produce offspring through sexual reproduction is approximately 1:1 between males and females. A. W. F. Edwards has remarked that it is "probably the most celebrated argument in evolutionary biology". [1]
Beginning of animal evolution. [54] [55] 720–630 Ma Possible global glaciation [56] [57] which increased the atmospheric oxygen and decreased carbon dioxide, and was either caused by land plant evolution [58] or resulted in it. [59] Opinion is divided on whether it increased or decreased biodiversity or the rate of evolution. [60] [61] [62 ...
The evolution of biological complexity is one important outcome of the process of evolution. [1] Evolution has produced some remarkably complex organisms – although the actual level of complexity is very hard to define or measure accurately in biology, with properties such as gene content, the number of cell types or morphology all proposed as possible metrics.
Such a situation will lead to cyclic changes in allele frequency – as p increases in frequency, h will be disfavoured. In reality, there will be several genes involved in the relationship between hosts and parasites. In an asexual population of hosts, offspring will only have the different parasitic resistance if a mutation arises.