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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.