Examination of the major reservoirs, fluxes, and processes controlling the distribution of biologically active chemical constituents of the earth. The importance of these biogeochemical cycles in the geologic past and the effects of human perturbation of these cycles. Three lecture hours a week for one semester. Geological Sciences 388G and 391 (Topic: Global Biogeochemical Cycles) may not both be counted. Prerequisite: Graduate standing in geological sciences, or graduate standing and consent of instructor.