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SPECIATION
The 5th Idea of Natural Selection
SPECIATION
 Formation of a new species
 Most new species are formed through a three-stage
process called ALLOPATRIC SPECIATION
Allop. Spec. – STEP #1
 A genetic or physical barrier separates a population
into two groups that are isolated from each other.
 Isolated groups do not mate with each other, ensuring
that mutations within one group are not passed to the
other.
 Physical barriers between groups could be natural
(mountain ranges, ocean, canyons, rivers) or manmade (dams, canal, cities)
Allop. Spec. – STEP #1
 Another barrier that can occur is DNA mutation
changing the number of chromosomes an organism
has.
Allop. Spec. – STEP #2
 Natural selection works on both groups independently
resulting in differences in two groups.
 The larger the differences in their environments, the
more differences will be visible between the two
species.
Allop. Spec. – STEP #3
 The two species are formed due to an increase in the
physical and behavioral differences accumulated by
each species.
 Both groups will no longer be sexually compatible an
unable to produce fertile offspring…
 TWO NEW SPECIES HAVE BEEN FORMED
Example! Darwin’s Finches
 Darwin discovered 13 different finch species when
travelling in the Galapagos Islands.
 All species were approximately the same size (15-20
cm) and are brownish/black in color.
BUT EACH SPECIES HAS….
 beaks of different size and shape.
 different mating behaviors.
 different song melodies.
Wood Bison & Plains Bison
 Originally shared one common ancestor before
population was split into two groups.
 Wood bison live in woods of Northern Canada
(population focused around Wood Buffalo National
Park).
 Plains Bison are found in Southern Prairie provinces
and majority of the US.