... The Americas are independent from the rest of the world by the surrounding oceans however are to some extent currently biogeographically separate from each other. However when the Panama Isthmus first united them there was a great interchange of species, which will be discussed later. Although the plates move very slowly, only about 5 - 10 cm a year (Cox and Moore 1993), over geologic time, life would be greatly affected. At one point in geologic history all the continents were united as one super-continent known as Pangaea about 260 million years ago. This came from the uniting of Euramerica, Siberia, Gondwana and two portions of what is now China. At this point all land flora and fauna were joined by land and could potentially colonise the entire world causing the spread of certain species and extinction of other species by competition. However there would have be a massive dry area ...

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