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Polymorphism is common in nature; it is related to biodiversity, genetic variation, and adaptation. Polymorphism usually functions to retain a variety of forms in a population living in a varied environment. [3]: 126 The most common example is sexual dimorphism, which occurs in many organisms.
An example of a botanical genetic polymorphism is heterostyly, in which flowers occur in different forms with different arrangements of the pistils and the stamens. The system is called heteromorphic self-incompatibility , and the general 'strategy' of stamens separated from pistils is known as herkogamy .
A genetic polymorphism means that different forms of particular genes, and hence of the proteins that they produce, are co-existing within a species. Selectionists claimed that such polymorphisms are maintained by balancing selection, while neutralists view the variation of a protein as a transient phase of molecular evolution. [1]
One example is the gene CD14, which is known to have a polymorphism that is associated with increased amounts of CD14 protein as well as reduced levels of IgE serum. [30] A study was conducted on 624 children looking at their IgE serum levels as it related to the polymorphism in CD14.
A rare example of sympatric speciation in animals is the divergence of "resident" and "transient" orca forms in the northeast Pacific. [26] Resident and transient orcas inhabit the same waters, but avoid each other and do not interbreed. The two forms hunt different prey species and have different diets, vocal behaviour, and social structures.
Polymorphism can be distinguished by when the implementation is selected: statically (at compile time) or dynamically (at run time, typically via a virtual function). This is known respectively as static dispatch and dynamic dispatch, and the corresponding forms of polymorphism are accordingly called static polymorphism and dynamic polymorphism.
Phase transitions (phase changes) that help describe polymorphism include polymorphic transitions as well as melting and vaporization transitions. According to IUPAC, a polymorphic transition is "A reversible transition of a solid crystalline phase at a certain temperature and pressure (the inversion point) to another phase of the same chemical composition with a different crystal structure."
Incomplete lineage sorting (ILS) [1] [2] [3] (also referred to as hemiplasy, deep coalescence, retention of ancestral polymorphism, or trans-species polymorphism) is a phenomenon in evolutionary biology and population genetics that results in discordance between species and gene trees.