All organisms are discrete entities that interact and disperse locally.
Space unavoidably causes individuals to differ in both the intra- and interspecific interactions and the resource levels they experience. Although detailed spatially explicit models of population growth and interaction can be cumbersome, three simple approaches can abstract different aspects of the essence of spatial ecology. The Levins' model is only implicitly spatial because its assumes global dispersal, but this makes it analytically tractable. It often provides a reasonable approximation to explicitly spatial simulators, such as cellular automata. One of its interesting predictions is that no species living in a spatial habitat can occupy all sites at equilibrium, which has profound implications for biodiversity.