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Evolution by natural selection is the process by which traits that enhance survival and reproduction become more common in successive generations of a population. It embodies three principles: [7] Variation exists within populations of organisms with respect to morphology, physiology and behaviour (phenotypic variation).
The result of four billion years of evolution is the diversity of life around us, with an estimated 1.75 million different species in existence today. [71] [72] Usually the process of speciation is slow, occurring over very long time spans; thus direct observations within human life-spans are rare.
Also called functionalism. The Darwinian view that many or most physiological and behavioral traits of organisms are adaptations that have evolved for specific functions or for specific reasons (as opposed to being byproducts of the evolution of other traits, consequences of biological constraints, or the result of random variation). adaptive radiation The simultaneous or near-simultaneous ...
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.
Recent human evolution refers to evolutionary adaptation, sexual and natural selection, and genetic drift within Homo sapiens populations, since their separation and dispersal in the Middle Paleolithic about 50,000 years ago. Contrary to popular belief, not only are humans still evolving, their evolution since the dawn of agriculture is faster ...
Devolution, de-evolution, or backward evolution (not to be confused with dysgenics) is the notion that species can revert to supposedly more primitive forms over time. The concept relates to the idea that evolution has a divine purpose and is thus progressive (orthogenesis), for example that feet might be better than hooves, or lungs than gills.
Convergent evolution is the process in which related or distantly related organisms evolve similar characteristics independently. This type of evolution creates analogous structures which have a similar function, structure, or form between the two species. For example, sharks and dolphins look alike but they are not related.
Genome evolution – Process by which a genome changes in structure or size over time; Hologenome theory of evolution – Organism as host plus microbe community; Models of DNA evolution – Mathematical models of changing DNA; Molecular evolution – Process of change in the sequence composition of cellular molecules across generations