Introduction to major perturbations in the history of life; specifically, mass extinctions and carbon-cycle perturbations (hyperthermal, anoxic, and acidification events). Discuss kill mechanisms (impacts, large igneous provinces, glaciations) and the subsequent environmental perturbations and ecological ramifications. Examine biotic crises in the past, with an eye to future ecosystem collapse, as well as the environmental and paleobiological responses to these events.