This course focuses on the impact of infectious disease on the biology of plants, animals and humans at the individual and population levels. Emphasis is placed on unifying principles of transmission modes, resistance mechanisms, and population consequences. The course covers the following subjects: the history of the study of disease; examples of pathogens of humans, crops, and wild populations; pathogen life histories; transmission modes; physiological and genetic basis of pathogenicity and host resistance; the evolution of resistance and virulence; population dynamics of disease; disease and the origin of genetic systems; disease and conservation; molecular phylogeny and epidemiology of disease.