At convergent plate boundaries, oceanic crust is often forced down into the mantle where it begins to melt. Magma rises into and through the other plate, solidifying into granite, the rock that makes up the continents. Thus, at convergent boundaries, continental crust is created and oceanic crust is destroyed.
Meiosis. Sexual recombination. Crossing over. Independent assortment. Mutations.
The two MAIN sources would be genetic(sexual) recombination and mutations. Mutations allow for genetic variation, while genetic recombination allows for genetic shuffling. :)
Some have been noted to live as long as 6 days without there head.
Persipitation and geographic layout