Introduction to major perturbations in the history of life; specifically, mass extinctions and carbon-cycle perturbations (e.g. ocean anoxic events, hyperthermals, and acidification events). Examine kill mechanisms (e.g. glaciations, impacts, large igneous provinces) and the subsequent environmental perturbations and ecological ramifications. Explore biotic crises in the past, with an eye to future ecosystem collapse, as well as the environmental and paleobiological responses to these events. Geological Sciences 391 (Topic: Transitions in the History of Life) and 397L may not both be counted. Three lecture hours a week for one semester.