Step 3: Independent evolution of isolated populations and speciation

Once reproductive isolation has occurred, the separate strings add and discard beads independently of each other. Over evolutionary time they become different species, different from each other and different from their common ancestor, Ancestor Species A (see Step 1).

With another two units of evolutionary time having passed, our strings of beads may look like this:

Species BSpecies C

   

   

   

   

   

   

   

   

   

   

   

   

   

   

   

   

   

   

   

   

   

   

   

   

Notice that you can still see the beads derived from the prototype common ancestor A0, as well as those from the more immediate common ancestor, Ancestor Species A. Hence the beads (representing bundles of genetic information) predict characteristics or properties that will be shared between Species B and Species C and help you track their evolutionary history (phylogeny) back to a common ancestor.

Return to Step 1: Evolution in prototype common ancestor species, A0.

Return to Step 2. Reproductive isolation occurs between two populations of Ancestor Species A.

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