Biogeography often leads us to infer process from pattern . Biogeography is the study of the distributions of organisms in space and time . It can be studied with a focus on ecological factors that shape the distribution of organisms, or with a focus on the historical factors that have shaped the current distributions. These sorts of observations were made by early biogeographers who recognized certain types of distributions of organisms. Some species are restricted to a certain region and are referred to as endemic species .
Cosmopolitan species have a world wide distribution.
They may be restricted to specific habitats, but occur on most continents. Marsupials are found in Australia and South America. Wallace worked primarily in Malaysian region and had noticed a clear break between Australian fauna and the fauna on the islands to the northwest. These patterns described long before continental drift was an issue. See table 18.1, pg 511.