Original: Ecozones represent large areas of the Earth 's surface where plants and animals developed in relative isolation over long periods of time , and are separated from one another by geologic features , such as oceans , broad deserts , or high mountain ranges , that formed barriers to plant and animal migration .
Simplified: The WWF scheme is broadly similar to Udvardys system , the chief difference being the delineation of the Australasian ecozone relative to the Antarctic , Oceanic , and Indomalayan ecozones .