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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]
Fourth, the modern evolutionary synthesis involved agreement about which forces contribute to evolution, but not about their relative importance. [36] Current research seeks to determine this. Evolutionary forces include natural selection, sexual selection, genetic drift, genetic draft, developmental constraints, mutation bias and biogeography.
In biology, evolution is the process of change in all forms of life over generations, and evolutionary biology is the study of how evolution occurs. Biological populations evolve through genetic changes that correspond to changes in the organisms ' observable traits .
Darwinian evolution by natural selection is pervasive in literature, whether taken optimistically in terms of how humanity may evolve towards perfection, or pessimistically in terms of the dire consequences of the interaction of human nature and the struggle for survival.
For example, if a population includes allele A with frequency equal to 20%, and allele a with frequency equal to 80%, there is an 80% chance that after an infinite number of generations a will be fixed at the locus (assuming genetic drift is the only operating evolutionary force).
Other evolutionary forces outside of mutation and natural selection can also play a role or be incorporated into experimental evolution studies, such as genetic drift and gene flow. [3] The organism used is decided by the experimenter, based on the hypothesis to be tested.
[32] [33] [34] Constructive neutral evolution is a theory which suggests that complex structures and processes can emerge through neutral transitions. Although a separate theory altogether, the emphasis on neutrality as a process whereby neutral alleles are randomly fixed by genetic drift finds some inspiration from the earlier attempt by the ...
Molecular evolution describes how inherited DNA and/or RNA change over evolutionary time, and the consequences of this for proteins and other components of cells and organisms. Molecular evolution is the basis of phylogenetic approaches to describing the tree of life .