The sphere of biogeography deals with the circulation of species considering both geography and location in relation to other species. Space and time are the primary factors of studies. It is to find out where the life forms live, in what quantity and for what reasons.
Biogeography consists of two disciplines: historical biogeography, which deals with the origins and evolutionary histories of species for a long time period, and ecological biogeography, which is about the modern connections between species with their surroundings and each other for a significantly shorter time period.
Biogeography is one more piece of evidence that serves as a proof of evolution. If evolution was indeed the case, you would normally expect species that are directly related to be found near each other except there was a decent reason for them not to be, for instance, outstanding mobility. On the whole, the biogeographic spreading of species assists evolution. Species are scattered around the globe mostly in relation to their associations to one another, with some unwritten omissions.
Darwin was the one who saw evidence for evolution in the geographic distribution of plants and animals, and future observations have strengthened his study. If there was such thing as evolution, you would normally suppose that species which are strongly related to be located near each other except for there were a realistic grounds for them not to be, such as huge mobility that, for example, sea animals, birds, and animals disseminated by men have. And truly, life forms are spread around the world greatly in dependence on their interaction with one another, with some explainable exceptions. “For example, marsupials are found almost exclusively in Australia, whereas placental mammals (not counting those brought there by humans) are very rare in Australia. The few exceptions are explainable by continental drift (remember that South America, Australia and Antarctica were once part of one continent)” (Lance). If species arise separately, it would be much more reasonable for them to survive wherever an environment could sustain them, as contrasting to being spread in accordance to their obvious relationship to other existing species.
“There are three main principles that sustain descent with modification” (Cox). The first principle states that environment cannot account for either similarity or dissimilarity, due to the fact that related environments can give refuge to totally diverse species groups. The second principle is based on the fact that “similarity of groups on the same continent is closer than between continents or seas” (Pears). The third principle states that geographical obstacles usually separate these diverse groups, and there is a connection between degree of differentiation and pace of migration or capability to scatter across the barriers.