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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]
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 modern evolutionary synthesis is the outcome of a merger of several different scientific fields to produce a more cohesive understanding of evolutionary ...
Research in evolutionary biology covers many topics and incorporates ideas from diverse areas, such as molecular genetics and mathematical and theoretical biology. Some fields of evolutionary research try to explain phenomena that were poorly accounted for in the modern evolutionary synthesis.
The rate of evolution is quantified as the speed of genetic or morphological change in a lineage over a period of time. The speed at which a molecular entity (such as a protein, gene, etc.) evolves is of considerable interest in evolutionary biology since determining the evolutionary rate is the first step in characterizing its evolution. [1]
Over time these evolutionary processes lead to formation of new species , changes within lineages , and loss of species . "Evolution" is also another name for evolutionary biology, the subfield of biology concerned with studying evolutionary processes that produced the diversity of life on Earth.
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.
Evolutionists expected one part to change at a time, one change to follow another. In Cuvier's view, evolution was impossible, as any one change would unbalance the whole delicate system. [11] Louis Agassiz's 1856 "Essay on Classification" exemplified German philosophical idealism. This held that each species was complex within itself, had ...
The traditional view is that developmental biology played little part in the modern synthesis, [45] but in his 1930 book Embryos and Ancestors, the evolutionary embryologist Gavin de Beer anticipated evolutionary developmental biology [46] by showing that evolution could occur by heterochrony, [47] such as in the retention of juvenile features ...