GEOS 101(F) Biodiversity in Geologic Time (Same as Environmental Studies 105)

Is planet Earth now undergoing the most severe mass extinction of species ever to have occurred during its 4.5-billion-year history? By some calculations, the expanding population of a single species is responsible for the demise of 74 species per day. This provocative question is addressed by way of the rock and fossil record as it relates to changes in biodiversity through deep geologic time before the appearance of Homo sapiens only 250,000 years ago. Long before human interaction, nature conducted its own experiments on the complex relationship between evolving life and changes in the physical world. This course examines ways in which wandering continents, shifting ocean basins, the rise and fall of mountains, the wax and wane of ice sheets, fluctuating sea level, and even crashing asteroids all shaped major changes in global biodiversity. Particular attention is drawn to the half dozen most extensive mass extinctions and what factors may have triggered them. Equal consideration is given to how the development of new ecosystems forever altered the physical world. How and when did the earliest microbes oxygenate the atmosphere? Do the earliest multicellular animals from the late Precambrian portray an architectural experiment doomed to failure? What factors contributed to the explosive rise in biodiversity at the start of the Cambrian Period? What explanation is there for the sudden appearance of vertebrates? How and when did plants colonize the land? What caused the demise of the dinosaurs? Is the present dominance of mammals an accident of nature? The answers to these and other questions are elusive, but our wise stewardship of the planet and its present biodiversity may depend on our understanding of the past. Concepts of plate tectonics and island biogeography are applied to many aspects of the puzzle. Format: lecture; one laboratory per week (some involving field work); plus one all-day field trip to the Helderberg Plateau and Catskill Mountains of New York, and a half-day trip to the Geology Museum at Amherst College. Evaluation will be based on weekly quizzes and lab work, a midterm exam, and a final exam. Enrollment limit: 35 (expected:20). This course satisfies "The Natural World" requirement for the Environmental Studies concentration.

Hour: M. JOHNSON