The Number of Different Species - In Total

Modern science has catalogued about two million different species. This by no means represents the totality of all living species. It has been estimated that the total number of different species on Earth today ranges from about six to ten million.

This of course still does not measure the totality of life that has been produced on Earth. Many species that once called Earth home are no longer in existence. Numbers for these extinct species are more difficult to estimate. But scientists believe that there must have been at least as many millions of species in the past, if not more.