The Origin of Species

understanding speciation video

• http://www.5min.com/Video/Understanding-Speciation-150610251 ???

Speciation

• Species – population sharing a gene pool - group of organisms which can interbreed

• Speciation – changes in a population so that it can no longer breed with other populations of the same original species.

• Due to Genetic drift (chance) or Natural selection (not chance) in a population

Macroevolution is the origin of new speciesMicroevolution is genetic variation within a species.  A species is a population or group of populations whose members have the potential to interbreed with one another and produce viable offspring, but who cannot produce viable offspring with other species.

Problems with this definitionBreeds? eg dogsExtinct species?Cryptic species? (appear identical, but

reproductively isolated) 

The biological species concept is based on inter-fertility, rather than physical similarity.

Modes of speciation            

1.  Allopatric speciation

populations geographically separate. Gene flow is interrupted.

2.  Sympatric speciation

geographically overlapping populations. 

Chromosomal changes / nonrandom mating reduce gene flow.

Species arise when individuals in a population become reproductively isolated one from the other.

Videos

• Wolfe: What is a species?• http://

www.youtube.com/watch?v=LEGQu3cm3CE