In this talk I will give an overview of how statistical mechanical models may be brought to bear on the study of populations of organisms (e.g. microbes) that may switch between different phenotypical states. At the microscopic level one may consider the dynamics that lead to the switching on or off of certain genes. At the macroscopic level one can consider how heterogeneity within a population is maintained through switching and what is the best switching strategy for the population in the face of a changing environment. I will focus on two simple models, one for a genetic switch and one for the growth of a population in an environment which produces catastrophic events, both of which may be solved exactly.