"Biogeography is the study of the distributions of plants and animals over the surface of the Earth in both space and time. The spatial component of biogeography attempts to describe and explain the distributions of one or more species over the world." ~ http://www.nearctica.com/ecology/habitats/biogeo.htm
Biogeography allows scientist to discover what species of animals lived together, and in what are of the world they lived together. This is important for scientist to know because they could lead it back to the current day relations among the species of today. Since biogeography lets one view the relations of animals, they could also discover which animals lived in which time period.
Another benefit of biogeography is the ability for a scientist to view the stages of evolution among the animals of the past and animals of the present. This can help of think of an origin of a animal as well as what it evolved from in its time. ~KP
Biogeography deals with patterns. Embryology also has a lot of patterns assoseated with it. Both subjects also bring up alot of questions in each of there fields.
The question of why species in a nearby area are closely related. Darwins thought that this was because of inheritance. They are the same because they came from the same ancestors.
Example of Biogeography - "Every other remote island has its own examples. In the Galapagos, the role of woodpecker is taken by a finch. Or rather, it's mostly a finch, but it has a beak specialized for the woodpecker role. Apparently, the only land bird which got to the Galapagos was a finch, so all the land birds there are modified finches"
(http://www.don-lindsay-archive.org/creation/biogeography.html)
