Modes of Speciation

Modes of speciation

1. Biological species concept defines a species as a population or group of

populations whose members have the potential to interbreed to produce viable, fertile offspring, but cannot produce viable, fertile offspring with members of other species

2. There are 2 main types of speciation: Allopatric and Sympatric Speciation.

-Allopatric Speciation - is when species divergence happens in geographically isolated areas

I. Geographic barriers may include mountain ranges, islands, etc. that split a population.

II. Geographic isolation is not necessarily reproductive isolation.

III. Likelyhood of allopatric speciation increases when a population is both small and isolated.

IV. Usually may lead to adaptive radiation, especially on island chains.

-Sympatric Speciation- when speciation occurs in the same area without a geographic barrier

I. In plants, speciation occurs through the condition Polyploidy

II. Polyploid speciation in animals is far less common than in plants.

III. In animals, sympatric speciation can result from a small part of population becoming reproductively isolated due to switch of habitat, food source, or other resources not used by the parent population.

IV. Or, it can result from emergence of a rigid mating preferences for a specific form in a polymorphic population.

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