  The science of ecology studies interactions between individual organisms and their environments, including interactions with both conspecifics and members of other species. Though ecology emerged in the 19th century much of its theoretical structure only emerged in the twentieth century. Though ecology includes a wide variety of sub-fields, philosophical analysis of ecology has so far been restricted to population, community, and ecosystem ecology. Central philosophical problems include explication of relevant notions of ecological diversity and stability the relation between diversity and stability. Other debated questions are the nature of laws and theories in ecology, strategies of model-building, and reductionism. Contemporary ecology is undergoing a conceptual upheaval because of increased computational power. The recent emphasis on individual-based models, which embrace methodological individualism, should be viewed as a return of reductionism in ecology. Other important developments include widespread interest in spatially explicit models and the advent of Geographical Information Systems.