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wcs
Geographic IsolationMadagascar didn't always sit isolated in the Indian Ocean. For about 520 million years, it was attached to the other landmasses of Earth as part of a supercontinent called Gondwana. About 150 million years ago, Gondwana began to split apart into the continents of the southern hemisphere. Look at the animation and timeline below to see how it split apart. 
What factor do you think is mainly responsible for the diversity on islands that were never connected to land, like Hawaii or the Galapagos? 
What factor do you think is mainly responsible for the diversity on islands once connected to continents, like Borneo or Papua New Guinea?  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? Look at the map below to see where you might find large flightless birds related to ostriches. 
How could you explain this pattern of distribution? |