All biogeographic patterns derive from these three processes, each is equally important. Later in the course we will look at the role of extinction in the distribution of species' populations.
Dispersal is the mechanism used in dispersal biogeography to explain distribution.
This is the traditional school of biogeography, i.e., species arise in a center of origin and spread out using corridors and other routes. Vicariance biogeography, i.e., the erection of barriers causing speciation is the other school. Although the argument continues, no doubt both schools have played roles. Dispersal is the tendency for an organism to move from its natal or breeding site. Don't confuse this with dispersion which is the spatial distribution of individual organisms within a population.