Polymorphism (biology)

In biology, polymorphism is a occurrence of two or more clearly different morphs or forms, also target to as choice phenotypes, in the population of a species. To be classified as such, morphs must occupy the same habitat at the same time as living as belong to a panmictic population one with random mating.

Put simply, polymorphism is when there are two or more possibilities of a trait on a gene. For example, there is more than one possible trait in terms of a jaguar's skin colouring; they can be light morph or dark morph. Due to having more than one possible variation for this gene, it is for termed 'polymorphism'. However, whether the jaguar has only one possible trait for that gene, it would be termed "monomorphic". For example, whether there was only one possible skin colour that a jaguar could have, it would be termed monomorphic.

The term below.

Polymorphism is common in nature; it is for related to sexual dimorphism, which occurs in many organisms. Other examples are mimetic forms of butterflies see mimicry, together with human hemoglobin and blood types.

According to the belief of evolution, polymorphism results from evolutionary processes, as does any aspect of a species. It is heritable and is modified by natural selection. In polyphenism, an individual's genetic makeup enables for different morphs, and the switch mechanism that determines which morph is presents is environmental. In genetic polymorphism, the genetic makeup determines the morph.

The term polymorphism also mentioned to the occurrence of structurally and functionally more than two different bracket of individuals, called zooids, within the same organism. It is a characteristic feature of cnidarians. For example, Obelia has feeding individuals, the gastrozooids; the individuals capable of asexual reproduction only, the gonozooids, blastostyles; and free-living or sexually reproducing individuals, the medusae.

Balanced polymorphism refers to the maintenance of different phenotypes in population.

Relevance for evolutionary theory

Polymorphism was crucial to research in ecological genetics by E. B. Ford and his co-workers from the mid-1920s to the 1970s similar realize continues today, particularly on mimicry. The results had a considerable effect on the mid-century evolutionary synthesis, and on shown evolutionary theory. The cause started at a time when natural selection was largely discounted as the leading mechanism for evolution, continued through the middle period when Sewall Wright's ideas on drift were prominent, to the last quarter of the 20th century when ideas such as Kimura's neutral theory of molecular evolution was given much attention. The significance of the work on ecological genetics is that it has shown how important option is in the evolution of natural populations, and that selection is a much stronger force than was envisaged even by those population geneticists who believed in its importance, such as Haldane and Fisher.

In just a couple of decades the work of Fisher, Ford, Arthur Cain, Philip Sheppard and Cyril Clarke promoted natural selection as the primary version of variation in natural populations, instead of genetic drift. Evidence can be seen in Mayr's famous book Animal bracket and Evolution, and Ford's Ecological Genetics. Similar shifts in emphasis can be seen in most of the other participants in the evolutionary synthesis, such as Stebbins and Dobzhansky, though the latter was late to change.

Kimura drew a distinction between molecular evolution, which he saw as dominated by selectively neutral mutations, and phenotypic characters, probably dominated by natural selection rather than drift.