Geographic Isolation  Some things are not good at making ocean voyages. Still, parts of the world that are very distant from one another may have animals and plants that are genetically closely related. Scientists believe that this is the result of events that have isolated populations of these animals from one another over time. Over time, these populations often become new species, a process called vicariance. Did you know that despite the fact that ostriches can't swim, their relatives live all over the world? Mouse over the map below to see where you might find large flightless birds related to ostriches. 
How could you explain this pattern of distribution? 
What factor do you think is mainly responsible for the diversity on islands that was never connected to land, like Hawaii or the Galapagos? 
Dispersal - The only way for organisms could get to these islands was dispersal – they had to swim, float or fly there. 
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