Environmental Problems, Their Causes, and Sustainability 1

For example, people visit degraded coastal environmentssuch as a coral reef and call it beautiful becausethey are unaware how it used to look. Veterandivers say, “You should have seen it in the old days.”In this chapter we have seen that almost all naturalecosystems and the biosphere itself achieve long-termsustainability in two ways. First, they use renewable solarenergy as their energy source. Second, they recycle thechemical nutrients their organisms need for survival,growth, and reproduction.These two sustainability principles arise from thestructure and function of natural ecosystems (Figures4-8 and 4-17), the law of conservation of matter(p. 47), and the two laws of thermodynamics (p. 51).Thus the results of basic research in both the physicaland biological sciences provide us with the sameguidelines or lessons from nature on how we can livemore sustainably on the earth, as summarized in Figure3-19 (p. 53).All things come from earth, and to earth they all return.MENANDER (342–290 B.C.)CRITICAL THINKING1. (a) A bumper sticker asks, “Have you thanked a greenplant today?” Give two reasons for appreciating a greenplant. (b) Trace the sources of the materials that make upthe bumper sticker, and decide whether the sticker itselfis a sound application of the slogan.2. Explain why microbes are the real rulers of the earth.3. Explain how decomposers help keep you alive.4. (a) How would you set up a self-sustaining aquariumfor tropical fish? (b) Suppose you have a balanced aquariumsealed with a clear glass top. Can life continue in theaquarium indefinitely as long as the sun shines regularlyon it? (c) A friend cleans out your aquarium and removesall the soil and plants, leaving only the fish and water.What will happen? Explain.5. Make a list of the food you have eaten today and traceeach type of food back to a particular producer.6. Use the second law of thermodynamics (p. 51) to explainwhy there is such a sharp decrease in usable energyas energy flows through a food chain or web. Does anenergy loss at each step violate the first law of thermodynamics(p. 51)? Explain.7. Use the second law of thermodynamics (p. 51) to explainwhy many poor people in developing countries liveon a mostly vegetarian diet.8. Why do farmers not need to apply carbon to growtheir crops but often need to add fertilizer containing nitrogenand phosphorus?9. Carbon dioxide (CO 2 ) in the atmosphere fluctuatessignificantly on a daily and seasonal basis. Why are CO 2levels higher during the day than at night?10. What would happen to an ecosystem if (a) all its decomposersand detritus feeders were eliminated or (b) allits producers were eliminated? Are we necessary for thefunctioning of any natural ecosystem? Explain.PROJECTS1. Visit several types of nearby aquatic life zones andterrestrial ecosystems. For each site, try to determinethe major producers, consumers, detritivores, anddecomposers.2. Write a brief scenario describing the sequence of consequencesto us and to other forms of life if each of thefollowing nutrient cycles stopped functioning: (a) carbon,(b) nitrogen, (c) phosphorus, and (d) water.3. Use the library or the Internet to find out bibliographicinformation about G. Evelyn Hutchinson and Menander,whose quotes are found at the beginning and end of thischapter.4. Make a concept map of this chapter’s major ideas usingthe section heads, subheads, and key terms (in boldface).Look on the website for this book for informationabout making concept maps.LEARNING ONLINEThe website for this book contains study aids and manyideas for further reading and research. They include achapter summary, review questions for the entire chapter,flash cards for key terms and concepts, a multiple-choicepractice quiz, interesting Internet sites, references, and aguide for accessing thousands of InfoTrac ® CollegeEdition articles. Log on tohttp://biology.brookscole.com/miller14Then click on the Chapter-by-Chapter area, choose Chapter4, and select a learning resource.86 CHAPTER 4 Ecosystems: What Are They and How Do They Work?