As you ponder why the flowers, birds, and trees of the midwest and the rocky mountains are very different you remember that such differences in the distribution of species are part of the field of biogeography, which studies of the geographic distribution of plants and animals, but also the distributions of organisms in time. Biogeography explains how as species adapted to new conditions, members of the same species that had been separated geographically diverge, result in the eventual formation of distinct species.