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). Addresses kill mechanisms (e.g. glaciations, impacts, large igneous provinces) and the subsequent environmental perturbations and ecological ramifications. Covers biotic crises in the past, with an eye to future ecosystem collapse, as well as the environmental and paleobiological responses to these events. Three lecture hours a week for one semester. Geological Sciences 322J and 371T (Topic: Transitions in the History of Life) may not both be counted. May be repeated for credit. Prerequisite: Upper-division standing; Geological Sciences 405 with a grade of at least C-, or consent of instructor.