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Palaeobiology

Parallel Evolution

The evolution of similar or identical characters independently in related lineages.

Parapatric

Populations that have contiguous but non-overlapping geographic distibutions. See also sympatric and allopatric.

 

Peripatric Speciation

A type of allopatric speciation in which a colony diverges from a parent population. Also known as founder effect speciation.

Phenotype

The observable physical or biochemical characteristics of an organism, as determined by both genetic makeup (genotype) and environmental influences.

Phylogenetic species concept

A species is the smallest monophyletic group of common ancestry. See also biological species concept and morphospecies concept.

Polyploidy

A major mechanism of speciation in plants. Caused by a failure of reduction of chromosome number during meiosis so 2n gametes are produced. Polyploid organisms have >2 sets of chromosomes. If new species are formed by polyploidy the polyploids must have higher fitness than the parental forms, they can achieve this by occupying new niches. Two types: autopolyploidy and allopolyploidy.

Reproductive character displacement

Where a character used in species recognition differs more greatly between sympatric than between allopatric populations/species.

Reproductive Isolation

The situation where two populations are prevented or restricted from interbreeding by isolating mechanisms.

Reproductive Reinforcement

Evolution of enhanced reproductive isolation between populations due to natural selection.

Resource Polymorphism

Where different morphs of an organism exploit different resources. Sometimes maintained by frequency-dependent selection, e.g. scale eating fish. Two morphs exist, one with the mouth on the left-hand side, the other with the mouth on the right-hand side. The side on which they approach their prey depends upon the side on which their mouth is located.

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