The first year tutorial, taken in the fall semester, is Grinnell College's only general academic course requirement. The college intends the tutorial to assist students in further developing their critical thinking skills and in improving their written and oral communication skills. Each of the tutorials offered in a given fall semester is based around a particular subject matter, which provides the vehicle by which the above goals are accomplished. The arrival of European Americans in the Upper Midwest in the middle of the nineteenth century led to dramatic changes in the region's ecology. In what was perhaps the most rapid and extensive degradation of a natural ecosystem in human history, in the space of 50 years settlers plowed under millions of acres of the native tallgrass prairie and replaced it with a diversified agricultural ecosystem on what proved to be some of the best farmland in the world. As agriculture expanded, the prairie diminished.