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Modes of Speciation. Modes of speciation. There are different modes that can lead to the formation of new species: Sympatric and Allopatric speciation. Sympatric speciation. A single population divides suddenly into two reproductively isolated groups within the same geographical area .

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modes of speciation1
Modes of speciation
  • There are different modes that can lead to the formation of new species:
  • Sympatric and Allopatric speciation
sympatric speciation
Sympatric speciation
  • A singlepopulation divides suddenly into two reproductively isolated groups within the samegeographical area.
  • Plants are best example – due to changes in chromosome number (polyploidy) doubling of chromosome number during cell division.
  • These plants can no longer breed with the plants around them.
sympatric speciation1
Sympatric speciation

Many plants are able to reproduce both sexually and asexually. If an individual plant has a mutation that prevents successful sexual reproduction, it may be

able to reproduce asexually.

allopatric speciation
Allopatric speciation
  • New species are formed once populations are physically separated. Once separated, they can no longer exchange genetic information. Over generations the two population become less and less alike. Any mutations that arise in one population are not shared with the other population. Different environments lead to different forms of natural selection.
pace of speciation
Pace of speciation
  • Phyletic gradualism
  • Change is very slow but steady within a lineage before or after a divergence (splitting of a line of descent)
  • Could explain the lack of transitional species, because the changes are subtle
pace of speciation1
Pace of speciation
  • Punctuated equilibrium
  • Speciation occurs rapidly during periods of stasis (limited change)

This could also explain the lack of transitional species, because the changes are significant

is speciation smooth or jerky
Is speciation smooth or jerky?
  • Gradualism model Punctuated equilibrium model