Many species evolved over many years, two distinct process occurred simultaneously: speciation and extinction.
Speciation was happened when species diverges into two distinct speciation as a result of disparate natural selection. Geographic isolation fosters speciation. We have two kinds of fox. One of them is arctic with heavier fur to camouflage itself.
When species ceases to exist ,extinction happens: it is a catastrophic event.
Speciation kept ahead of extinction. There is clear evidence that extinction have been followed by dramatic increases in new species. It takes along time for a biological diversity to be rebuilt, for example, the evolution of mammals increased spectacularly over the millions of years that ensued.
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