In Charles Darwin’s theory of natural history, selection is the principal mechanism that is responsible for the evolution of life on Earth. Three conditions must be met if natural selection shall occur in an ecological system. First, organisms living in the system must show phenotypic variations that bear upon their survival. Second, those variations must
Our understanding of several communication phenomena has benefited extensively from informative reports of “natural” experiments. Natural experiments are infrequently detailed in the social and behavioral sciences, however, because they result only when naturally arising circumstances make it possible to separate and examine typically confounded phenomena. Like field experiments, natural experiments occur in venues where the
The agriculture cluster is large and diverse, with careers ranging from the farm to the laboratory to the corporate office. This industry is made up of the farmers who cultivate the land, raise livestock, and grow plants; the businesses that purchase, process, distribute, and transport farm products and farm supplies; and the organizations that supply