Editing Polymorphism (biology) (section)

== Terminology ==

Monomorphism means having only one form. Dimorphism means having two forms.
* Polymorphism does not cover characteristics showing continuous variation (such as weight), though this has a heritable component. Polymorphism deals with forms in which the variation is discrete (discontinuous) or strongly [[bimodal]] or polymodal.<ref name="Ford 1975" />
* Morphs must occupy the same habitat at the same time; this excludes geographical races and seasonal forms.<ref name="Sheppard 1975">[[Philip Sheppard (biologist)|Sheppard, Philip M.]] 1975. ''Natural Selection and Heredity'' (4th ed.) London: Hutchinson.</ref> The use of the words "morph" or "polymorphism" for what is a visibly different geographical race or variant is common, but incorrect. The significance of geographical variation is that it may lead to [[allopatric speciation]], whereas true polymorphism takes place in [[panmictic]] populations.
* The term was first used to describe visible forms, but it has been extended to include cryptic morphs, for instance [[blood types]], which can be revealed by a test.
* Rare variations are not classified as polymorphisms, and mutations by themselves do not constitute polymorphisms. To qualify as a polymorphism, some kind of balance must exist between morphs underpinned by inheritance. The criterion is that the frequency of the least common morph is too high simply to be the result of new [[mutation]]s<ref name="Ford 1975" /><ref name="Ford 1940">{{cite book |last=Ford |first=E. B. |year=1940 |title=The New Systematics |chapter=Polymorphism and Taxonomy | editor=Julian Huxley | editor-link=Julian Huxley |publisher=[[Clarendon Press|Clarendon Pr.]] |location=Oxford | pages=493–513 |isbn=978-1-930723-72-6}}</ref> or, as a rough guide, that it is greater than 1% (though that is far higher than any normal mutation rate for a single [[allele]]).<ref name="Sheppard 1975" />{{rp|ch. 5}}

=== Nomenclature ===

Polymorphism crosses several discipline boundaries, including ecology, genetics, evolution theory, taxonomy, cytology, and biochemistry. Different disciplines may give the same concept different names, and different concepts may be given the same name. For example, there are the terms established in ecological genetics by [[E.B. Ford]] (1975),<ref name="Ford 1975">Ford, E. B. 1975. ''Ecological Genetics'' (4th ed.). London: Chapman & Hall</ref> and for classical genetics by [[John Maynard Smith]] (1998).<ref name="Smith 1998">Smith, John Maynard. 1998. ''Evolutionary Genetics'' (2nd ed.). Oxford: Oxford U. Pr.</ref> The shorter term morphism was preferred by the evolutionary biologist [[Julian Huxley]] (1955).<ref>{{cite journal | last=Huxley |first=Julian S. | year=1955 | title=Morphism and Evolution | journal=Heredity | volume=9 | issue=1| pages=1–52 | doi=10.1038/hdy.1955.1 | doi-access=free |bibcode=1955Hered...9....1H }}</ref>

Various synonymous terms exist for the various polymorphic forms of an organism. The most common are morph and morpha, while a more formal term is morphotype.  Form and [[gametic phase|phase]] are sometimes used, but are easily confused in zoology with, respectively, [[Form (zoology)|"form"]] in a population of animals, and "phase" as a color or other change in an organism due to environmental conditions (temperature, humidity, etc.). [[Phenotypic trait]]s and characteristics are also possible descriptions, though that would imply just a limited aspect of the body.{{cn|date=December 2024}}

In the [[Taxonomy (biology)|taxonomic nomenclature]] of [[zoology]], the word "morpha" plus a Latin name for the morph can be added to a [[binomial nomenclature|binomial]] or [[trinomial nomenclature|trinomial]] name. However, this invites confusion with geographically variant [[ring species]] or [[subspecies]], especially if polytypic. Morphs have no formal standing in the [[International Code of Zoological Nomenclature|ICZN]]. In [[Botany|botanical taxonomy]], the concept of morphs is represented with the terms "[[Variety (botany)|variety]]", "[[Subvariety (botany)|subvariety]]" and "[[Form (botany)|form]]", which are formally regulated by the [[ICBN|ICN]]. Horticulturists sometimes confuse this usage of "variety" both with [[cultivar]] ("variety" in [[viticultural]] usage, rice agriculture jargon, and informal [[gardening]] lingo) and with the legal concept "[[Plant variety (law)|plant variety]]" (protection of a cultivar as a form of [[intellectual property]]).{{cn|date=December 2024}}