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Lecture 5 The Age of Stupid. http://www.youtube.com/watch?v=u7StWHQCakI&feature=related • Don't miss this important, one-time-only U.S. screening of the global warming docudrama, The Age of Stupid. September 21, 2009 6:30 p.m. Hollywood USA - CollegeStation 1401 Earl Rudder Fwy S College Station, TX, 77845 • • Click Here to Purchase Tickets http://www.ncm.com/Fathom/Upcoming/Locations.aspx?eventid=809&zip=77845&eventdate=9/21/2009 Immediately following the film will be a special event simulcast from New York, featuring a performance by Radiohead's Thom Yorke and comments from Kofi Annan, James Hansen, Moby, as well as leading climate experts and activists. On Monday, September 21, MoveOn members in the College Station area have a special opportunity to watch the onenight-only premiere of an important new film called The Age of Stupid. The film is a powerful "docudrama" set in the year 2055, after global warming has done massive damage to humanity. Oscar-nominated actor Pete Postlethwaite stars as a historian who "looks back" on real footage from 2008 to try to answer the question, "why didn't we stop climate change while we had the chance?" Assignment for Tues: Do Study Quiz for Chapter 4. Read Chapter 6 Chapter 6: Principles of Ecology Self-Sustaining Mechanisms in Ecosystems Homeostasis • Like organisms, ecosystems possess many mechanisms that either resist change or help them recover from change. • These mechanisms help keep natural systems in a state of relative constancy. FIGURE 1: Water hyacinth in a Florida waterway Courtesy of Nancy Mayberry/U.S. Army Corps of Engineers The Resilience of Ecosystems • In ecosystems, changes in biotic and abiotic conditions lead to a cascade of effects, but the systems tend to return to normal over time. • The ability to resist change is called resilience. FIGURE 2: Ecosystem balance FIGURE 4: Regaining balance in a polluted stream Species Diversity and Stability Ecologists still debate the reasons why some ecosystems are stable and some are not. We do know that reductions in species diversity can destabilize ecosystems. FIGURE 6: Diversity vs. latitude 6.2 Natural Succession: Establishing Life on Lifeless Ground • Ecosystems can form on barren or relatively lifeless ground by a process called natural succession. FIGURE 07a: Lichens (the dark blotches) are fungi that grow on rocks and slowly erode their surface Courtesy of Dan Chiras FIGURE 07b: Primary succession FIGURE 9: Secondary succession FIGURE 08a (left): Mount St. Helens in southwest Washington was surrounded by a scenic northern coniferous forest prior to its eruption in 1980. FIGURE 08b (below): The aftermath of the eruption. Copyright © Weyerhaeuser. Used with permission. Copyright © Weyerhaeuser. Used with permission. FIGURE 08c: Secondary succession on Mt. St. Helens Copyright © Weyerhaeuser. Used with permission. FIGURE 08d: The Mount St. Helens area in 2007 © EdBookPhoto/Alamy Images FIGURE 11: The evolution of life on Earth Evolution By Natural Selection • Natural selection is the driving force behind evolution. • It consists of natural forces that select for those members of a population that are superior in one or more features. • These advantages increase chances of surviving and reproducing. • Natural selection weeds out the less fit organisms of a population, leaving behind the fittest. Genetic Variation: The Raw Material of Evolution • Genetic differences in organisms of a population are called genetic variation. • Genetic variation of organisms in a population may give some members of a population an advantage over others. • Genetic variation comes from: – mutations – sexual reproduction – “crossing over,” a process that occurs during the formation of sperm and ova • Genetic variation produces variation in populations in structure, function, and behavior. “London” smog and the English peppered moth Air Pollution, M. Jacobson London smog and the English peppered moth Natural selection 6.4 Human Impact on Ecosystems • Human activities alter the environment by changing its biotic and abiotic components–– directly or indirectly. FIGURE S01_1: Restored wetland in the southeastern United States Courtesy of Gary Kramer/NRCS USDA Altering Biotic Factors • Introduction of foreign species – These species may proliferate without control, causing major economic and environmental damage. FIGURE 14: Zebra mussel Courtesy of U.S. Fish & Wildlife Services FIGURE 13: The current range of Africanized Honey Bees in the United States (in grey) Adapted from Carl Hayden Bee Research Center/USDA ARS, Africanized Honey Bees, http://ars.usda.gov/Research/docs.htm?docid=11059. Simplifying Ecosystems • Tampering with abiotic and biotic factors tends to reduce species diversity and thus simplify ecosystems. • This makes them considerably more vulnerable to natural forces. FIGURE 15: Fomer range of the American chestnut (now almost extinct) Why Study Impacts? • Being able to predict impacts permits us to select the least harmful and most sustainable development options.