User:TedE/Natural selection

Working Definition
The biological characteristics of an organism can give relative advantages or disadvantages in that organism's ability to survive and reproduce. These differences lead to differences in reproductive success (including survival), which Charles Darwin termed natural selection in The Origin of Species (1859). The result of natural selection is that the genotypic frequencies of favorable genotypes increase, moderated by the genetics involved and other factors, such as mutation. Natural selection forms a solid foundation for Darwin's Theory of Evolution. As such, it also holds a prominent place in modern biology.

Darwin's Argument

 * Population sizes are stable
 * Reproductive output is greater than needed to maintain the population
 * Some physical characteristics are favored and others are disfavored wrt survival and reproduction (Natural Selection)
 * These physical characteristics are inherited

==> Evolution

Definition 1
Natural selection is the process in which individual organisms that possess favourable traits are more likely to survive and reproduce. Natural selection works on the phenotype, the outward form determined by genes (the genotype), the environment and the interaction between them. Only heritable variations in a trait will be passed on to the next generation and the frequency of favourable heritable traits will increase in subsequent generations. The underlying genetic variation in traits is the result of genetic processes, such as mutations and recombinations, and can undo the effect of natural selection if strong enough relative to the effect of natural selection. Natural selection, together with other mechanisms such as genetic drift and mutations, is an important component of evolution, a cornerstone of modern biological and medical research.

The term was introduced by Charles Darwin in 1859 in his book "The Origin of Species", as an analogy with a farmer choosing individuals that possess desired characteristics for his breeding stock, which Darwin called artificial selection.

Definition 2
Natural selection is the phrase used in evolutionary biology to describe the fact that individual organisms should tend to differ in reproductive output when they differ from each other in their ability to tackle the challenges posed by their biological and physical environment. The ability of individual organisms to tackle such challenges is determined by their biological traits and by the way these differ from those of other individuals. When trait differences resulting in higher reproductive output are heritable, the frequency of the superior trait(s) will tend to increase over the generations, i.e., adaptive evolution will take place. Natural selection is the main non-random force driving evolution and therefore plays a central role in the structure of biological thought and research.

The phrase was introduced by Charles Darwin in 1859 in his book The Origin of Species, in analogy to how farmers breed individuals that display desirable characteristics with the hope of improving crops or livestock (see artificial selection).

Definition 3
In evolutionary biology, natural selection is the process by which a species adapts to its environment over successive generations. It is commonly described as survival of the fittest. The phrase was introduced by Charles Darwin in 1859 in his book The Origin of Species.

Individual organisms should tend to differ in reproductive output when they differ from each other in their ability to tackle the challenges posed by their biological and physical environment. The ability of individual organisms to tackle such challenges is determined by their biological traits and by the way these differ from those of other individuals. When trait differences resulting in higher reproductive output are heritable, the frequency of the superior trait(s) will tend to increase over the generations, i.e., adaptive evolution will take place. Natural selection is the main non-random force driving evolution and therefore plays a central role in the structure of biological thought and research. Darwin coined the term as a analogous to the methods farmers use to breed improved crops or livestock (see artificial selection).

Charles Darwin, On the Origin of Species
"HOW will the struggle for existence, discussed too briefly in the last chapter, act in regard to variation? Can the principle of selection, which we have seen is so potent in the hands of man, apply in nature? I think we shall see that it can act most effectually. Let it be borne in mind in what an endless number of strange peculiarities our domestic productions, and, in a lesser degree, those under nature, vary; and how strong the hereditary tendency is. Under domestication, it may be truly said that the whole organisation becomes in some degree plastic. Let it be borne in mind how infinitely complex and close-fitting are the mutual relations of all organic beings to each other and to their physical conditions of life. Can it, then, be thought improbable, seeing that variations useful to man have undoubtedly occurred, that other variations useful in some way to each being in the great and complex battle of life, should sometimes occur in the course of thousands of generations? If such do occur, can we doubt (remembering that many more individuals are born than can possibly survive) that individuals having any advantage, however slight, over others, would have the best chance of surviving and of procreating their kind? On the other hand, we may feel sure that any variation in the least degree injurious would be rigidly destroyed. This preservation of favourable variations and the rejection of injurious variations, I call Natural Selection. Variations neither useful nor injurious would not be affected by natural selection, and would be left a fluctuating element, as perhaps we see in the species called polymorphic."