However, natural selection is "blind" in the sense that changes in phenotype can give a reproductive advantage regardless of whether or not the trait is heritable. Natural selection enhances the preservation of a group of organisms that are best adjusted to the physical and biological conditions of their Natural selection and may also result in their improvement in some cases.
If an organism lives half as long as others of its species, but has twice as many offspring surviving to adulthood, its genes become more common in the adult population of the next generation.
The concept of natural selection. A dark melanic morph of the peppered moth largely replaced the formerly usual light morph both shown here.
The balance Natural selection reversed by the effect of the Clean Air Actand the dark moths became rare again, demonstrating the influence of natural selection on peppered moth evolution. In broad terms, individuals that are more "fit" have better potential for survival, as in Natural selection well-known phrase " survival of the fittest ", but the precise meaning of the term is much more subtle.
Learn More in these related Britannica articles: Artificial selection is purposive where natural selection is not, though biologists often use teleological language to describe it. This principle of preservation, I have called, for the sake of brevity, Natural Selection.
After the publication of On the Origin of Species,  educated people generally accepted that evolution had occurred in some form. Fitness biology The concept of fitness is central to natural selection.
Darwin thought of natural selection by analogy to how farmers select crops or livestock for breeding, which he called " artificial selection "; in his early manuscripts he referred to a "Nature" which would do the selection.
Factors that disturb the natural equilibrium of gene frequencies include mutationmigration or gene flowrandom genetic driftand natural selection. A second synthesis was brought about at the end of the 20th century by advances in molecular geneticscreating the field of evolutionary developmental biology "evo-devo"which seeks to explain the evolution of form in terms of the genetic regulatory programs which control the development of the embryo at molecular level.
Migration is a local change in gene frequency when an individual moves from one population to another and then interbreeds. He was in the process of writing his "big book" to present his research when the naturalist Alfred Russel Wallace independently conceived of the principle and described it in an essay he sent to Darwin to forward to Charles Lyell.
Gene frequencies tend to remain constant from generation to generation when disturbing factors are not present. It struck him that as population outgrew resources, "favourable variations would tend to be preserved, and unfavourable ones to be destroyed. They are all random processes.
Herbert Spencer of the Survival of the Fittest is more accurate, and is sometimes equally convenient.
He defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved". If the traits that give these individuals a reproductive advantage are also heritablethat is, passed from parent to offspring, then there will be differential reproduction, that is, a slightly higher proportion of fast rabbits or efficient algae in the next generation.
Modern evolutionary theory defines fitness not by how long an organism lives, but by how successful it is at reproducing.Natural selection can only work on existing variation within a population. Such variations arise by mutation, a change in some part of the genetic code for a trait.
Mutations arise by chance and without foresight for the potential advantage or disadvantage of the mutation.
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. Charles Darwin popularised the term "natural selection".
Teach your students about natural selection: Clipbirds, a classroom activity for grades Breeding bunnies, a classroom activity for grades Find additional lessons, activities, videos, and articles that focus on natural selection.
Natural selection at work. Scientists have worked out many examples of natural selection, one of the basic mechanisms of evolution. Any coffee table book about natural history will overwhelm you with full-page glossies depicting amazing adaptations produced by natural selection, such as the examples below.
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Natural selection moderates the disorganizing effects of these processes because it multiplies the incidence of beneficial mutations over the generations and eliminates harmful ones, since their carriers leave few or no descendants.Download