Biogeography is the study of the spatial distribution of plants and animals, both today and in the past. Developed during the course of nineteenth century efforts to explore, map, and describe the earth, biogeography asks questions about regional variations in the numbers and kinds of species: Where do various species occur and why? What physical and biotic factors limit or extend the range of a species? In what ways do species disperse (expand their ranges), and what barriers block their dispersal? How has species distribution changed over centuries or millennia, as shown in the fossil record? What controls the makeup of a biotic community (the combination of species that occur together)? Biogeography is an interdisciplinary science: many other fields, including paleontology, geology, botany, oceanography, and climatology, both contribute to biogeography and make use of ideas developed by biogeographers.

Because physical and biotic environments strongly influence species distribution, the...