polymorphism

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polymorphism

polymorphism of minerals, property of crystallizing in two or more distinct forms. Calcium carbonate is dimorphous (two forms), crystallizing as calcite or aragonite. Titanium dioxide is trimorphous; its three forms are brookite, anatase (or octahedrite), and rutile. Polymorphism of an element is called allotropy . The process was discovered (1821) by Eilhard Mitscherlich. See isomorphism ; mineral ; crystal .

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polymorphism

A Dictionary of Ecology | 2004 | | Â© A Dictionary of Ecology 2004, originally published by Oxford University Press 2004. (Hide copyright information) Copyright

polymorphism
1. In genetics, the existence of two or more forms that are genetically distinct from one another but contained within the same interbreeding population. The polymorphism may be transient or it may persist over many generations, when it is said to be balanced. Classical examples of polymorphisms are the presence or absence of banding in Cepaea snails, the number of spots on the wings of ladybirds, and eye colour in humans. All these are visible polymorphism that can readily be seen in nature. Some polymorphism, however, is cryptic and requires biochemical techniques to identify phenotypic differences.

2. In social insects, the presence of different castes within the same sex. See also polytypism.

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