Figure 37.12A Figure 37.12A Primary succession on a lava flow 1

Annual plants Perennial plants and grasses Shrubs Softwood trees Figure 37.12B Annual plants Perennial plants and grasses Shrubs Softwood trees such as pines Hardwood trees Figure 37.12B Stages in the secondary succession of an abandoned farm field Time 2

37.13 CONNECTION: Invasive species can devastate communities Invasive species are organisms that have been introduced into non-native habitats by human actions and have established themselves at the expense of native communities. The absence of natural enemies often allows rapid population growth of invasive species. Student Misconceptions and Concerns For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. Teaching Tips 1. The United States Department of Agriculture sponsors the National Invasive Species Information Center, which maintains a website at www.invasivespeciesinfo.gov. 2. Students who are interested in wildlife may collect an animal to keep as a pet, or to admire for a few days. This might be a good time to remind them that if they hope to return a wild animal to its natural environment, they should do so quickly and return it to within a few feet of the spot of its collection. Reintroducing an organism to a nearby environment may spread disease and potentially extend the organism’s natural range. Further, the introduction of commercial specimens from fish tanks, such as the marine algae Caulerpa dumped into the ocean, has had devastating consequences. The following web site addresses this example www.invasivespeciesinfo.gov/aquatics/caulerpa.shtml. 3. The accidental introduction of the Brown Tree Snake into Guam during World War II has had a devastating impact on the ecology and economy of Guam. Extensive details can be found at www.fort.usgs.gov/Resources/Education/BTS/. 4. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights. © 2012 Pearson Education, Inc. 3

37.13 CONNECTION: Invasive species can devastate communities Examples of invasive species include the deliberate introduction of rabbits into Australia and cane toads into Australia. Student Misconceptions and Concerns For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. Teaching Tips 1. The United States Department of Agriculture sponsors the National Invasive Species Information Center, which maintains a website at www.invasivespeciesinfo.gov. 2. Students who are interested in wildlife may collect an animal to keep as a pet, or to admire for a few days. This might be a good time to remind them that if they hope to return a wild animal to its natural environment, they should do so quickly and return it to within a few feet of the spot of its collection. Reintroducing an organism to a nearby environment may spread disease and potentially extend the organism’s natural range. Further, the introduction of commercial specimens from fish tanks, such as the marine algae Caulerpa dumped into the ocean, has had devastating consequences. The following web site addresses this example www.invasivespeciesinfo.gov/aquatics/caulerpa.shtml. 3. The accidental introduction of the Brown Tree Snake into Guam during World War II has had a devastating impact on the ecology and economy of Guam. Extensive details can be found at www.fort.usgs.gov/Resources/Education/BTS/. 4. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights. © 2012 Pearson Education, Inc. 4

Frontier of rabbit spread 1860 Figure 37.13A 600 km 1980 1910 1910 1900 1910 1920 1920 1910 1890 1900 Figure 37.13A The spread of rabbits in Australia 1910 1880 1920 1920 1890 1870 1880 Key 1870 Frontier of rabbit spread 1860 5

Figure 37.13B Figure 37.13B A familiar sight in early 20th-century Australia 6

Figure 37.13C Figure 37.13C A cane toad (Bufo marinus) 7

ECOSYSTEM STRUCTURE AND DYNAMICS ECOSYSTEM STRUCTURE AND DYNAMICS © 2012 Pearson Education, Inc. 8

37.14 Ecosystem ecology emphasizes energy flow and chemical cycling An ecosystem consists of all the organisms in a community and the abiotic environment with which the organisms interact. In an ecosystem, energy flow moves through the components of an ecosystem and chemical cycling is the transfer of materials within the ecosystem. Student Misconceptions and Concerns Without an understanding of basic physics and the inefficiency of aerobic metabolism, students might not understand how chemical energy in food is lost as heat. Consider expanding upon the explanations given in the book. Teaching Tips 1. The heat generated as a by-product of metabolism, which is quite evident during strenuous exercise, is much like the heat produced by a running automobile engine. In both circumstances, heat is a by-product of the fuel-burning process. 2. Energy flow through an ecosystem is analogous to the flow of fuel through a car or electricity through a vacuum cleaner. These systems will not work without a steady input. NASA, however, must rely upon some closed systems for its spacecrafts. Students might enjoy investigating the recycling of gases and fluids in these systems. © 2012 Pearson Education, Inc. 9

37.14 Ecosystem ecology emphasizes energy flow and chemical cycling A terrarium represents the components of an ecosystem and illustrates the fundamentals of energy flow. Student Misconceptions and Concerns Without an understanding of basic physics and the inefficiency of aerobic metabolism, students might not understand how chemical energy in food is lost as heat. Consider expanding upon the explanations given in the book. Teaching Tips 1. The heat generated as a by-product of metabolism, which is quite evident during strenuous exercise, is much like the heat produced by a running automobile engine. In both circumstances, heat is a by-product of the fuel-burning process. 2. Energy flow through an ecosystem is analogous to the flow of fuel through a car or electricity through a vacuum cleaner. These systems will not work without a steady input. NASA, however, must rely upon some closed systems for its spacecrafts. Students might enjoy investigating the recycling of gases and fluids in these systems. © 2012 Pearson Education, Inc. 10

Light energy Chemical energy Chemical elements Figure 37.14 C h e m i c a l y n g Energy flow Light energy Chemical energy Heat energy Figure 37.14 A terrarium ecosystem Chemical elements Bacteria, protists, and fungi 11

37.15 Primary production sets the energy budget for ecosystems Primary production is carried out by producers, is the amount of solar energy converted to chemical energy by an ecosystem’s producers for a given area and during a given time period, and produces biomass, the amount of living organic material in an ecosystem. Different ecosystems vary in their primary production and contribution to the total production of the biosphere. Teaching Tips Challenge students to explain why the areas of greatest primary production are near the equator. (Answer: Primary production is a consequence of photosynthesis. Regions near the equator receive the highest levels of solar input.) © 2012 Pearson Education, Inc. 12

Algal beds and coral reefs Figure 37.15 Open ocean Estuary Algal beds and coral reefs Desert and semidesert scrub Tundra Temperate grassland Cultivated land Boreal forest (taiga) Savanna Temperate deciduous forest Figure 37.15 Net primary production of various ecosystems Tropical rain forest 500 1,000 1,500 2,000 2,500 Average net primary productivity (g/m2/yr) 13

37.16 Energy supply limits the length of food chains A caterpillar represents a primary consumer. Of the organic compounds a caterpillar ingests, about 50% is eliminated in feces, 35% is used in cellular respiration, and 15% is used for growth. Teaching Tips Why do food chains and webs typically have only three to five levels? This question, which is seldom considered by students, is addressed directly in this section of the chapter. It can spark a good opening discussion before a lecture on food chains and food webs. © 2012 Pearson Education, Inc. 14

Plant material eaten by caterpillar 100 kilocalories (kcal) 35 kcal Figure 37.16A Plant material eaten by caterpillar 100 kilocalories (kcal) Figure 37.16A The fate of leaf biomass consumed by a caterpillar 35 kcal Cellular respiration 50 kcal Feces 15 kcal Growth 15

37.16 Energy supply limits the length of food chains A pyramid of production shows the flow of energy from producers to primary consumers and to higher trophic levels. Only about 10% of the energy stored at each trophic level is available to the next level. Teaching Tips Why do food chains and webs typically have only three to five levels? This question, which is seldom considered by students, is addressed directly in this section of the chapter. It can spark a good opening discussion before a lecture on food chains and food webs. © 2012 Pearson Education, Inc. 16

Tertiary consumers Secondary consumers Primary consumers Producers Figure 37.16B Tertiary consumers 10 kcal Secondary consumers 100 kcal Primary consumers 1,000 kcal Producers Figure 37.16B An idealized pyramid of production 10,000 kcal 1,000,000 kcal of sunlight 17

37.17 CONNECTION: A pyramid of production explains the ecological cost of meat When humans eat grain or fruit, we are primary consumers, beef or other meat from herbivores, we are secondary consumers, and fish like trout or salmon, we are tertiary or quaternary consumers. Student Misconceptions and Concerns The environmental impact of eating farm animals is little appreciated by most students who otherwise may be concerned about global climate change and the conservation of natural ecosystems. This chapter section helps explain the basis of the increased costs associated with a diet that includes meat. Teaching Tips Some students might be interested in eating more proteins and fewer carbohydrates because of popular diet plans. But do high-protein diets always require the consumption of more meat? The many sources of plant proteins might be surprising to students. Some high-protein vegetarian options are described by the Vegetarian Society at its website, http://www.vegsoc.org/page.aspx?pid=783. © 2012 Pearson Education, Inc. 18

Eating meat of any kind is expensive 37.17 CONNECTION: A pyramid of production explains the ecological cost of meat Only about 10% of the chemical energy available in a trophic level is passed to the next higher trophic level. Therefore, the human population has about ten times more energy available to it when people eat plants instead of the meat of herbivores. Eating meat of any kind is expensive economically and environmentally. Student Misconceptions and Concerns The environmental impact of eating farm animals is little appreciated by most students who otherwise may be concerned about global climate change and the conservation of natural ecosystems. This chapter section helps explain the basis of the increased costs associated with a diet that includes meat. Teaching Tips Some students might be interested in eating more proteins and fewer carbohydrates because of popular diet plans. But do high-protein diets always require the consumption of more meat? The many sources of plant proteins might be surprising to students. Some high-protein vegetarian options are described by the Vegetarian Society at its website, http://www.vegsoc.org/page.aspx?pid=783. © 2012 Pearson Education, Inc. 19

Secondary consumers Primary consumers Figure 37.17 Trophic level Secondary consumers Meat-eaters Primary consumers Vegetarians Cattle Producers Corn Corn Figure 37.17 Food energy available to people eating at different trophic levels 20

Secondary consumers Primary consumers Figure 37.17_1 Trophic level Secondary consumers Primary consumers Vegetarians Figure 37.17_1 Food energy available to people eating at different trophic levels (part 1) Producers Corn 21

Secondary consumers Primary consumers Figure 37.17_2 Trophic level Secondary consumers Meat-eaters Primary consumers Cattle Figure 37.17_2 Food energy available to people eating at different trophic levels (part 2) Producers Corn 22

Ecosystems are supplied with a continual influx of energy from the 37.18 Chemicals are cycled between organic matter and abiotic reservoirs Ecosystems are supplied with a continual influx of energy from the sun and Earth’s interior. Except for meteorites, there are no extraterrestrial sources of chemical elements. Thus, life also depends on the recycling of chemicals. Student Misconceptions and Concerns Students are unlikely to have any prior knowledge of biogeochemical cycles. Although some transfers between the biotic and abiotic components of ecosystems, such as the use of fertilizer on plants, may be known to them, the broader fact that the biosphere is a self-cycling system is not appreciated by most students. Before you lecture, consider asking your students to explain how carbon, phosphorus, and nitrogen cycle through the atmosphere. Pre-testing your students on their knowledge can confirm both what they understand and what they may need explained to them in more detail. Teaching Tips As you discuss the importance of the biogeochemical cycles, consider explaining the basic label information provided on a container of plant fertilizer. Consider an example that might be used on houseplants, and therefore more likely to be familiar to students. Typically, plant fertilizers contain various forms of nitrogen and phosphorus, which are essential chemicals for growth. © 2012 Pearson Education, Inc. 23

Biogeochemical cycles include 37.18 Chemicals are cycled between organic matter and abiotic reservoirs Biogeochemical cycles include biotic components, abiotic components, and abiotic reservoirs, where a chemical accumulates or is stockpiled outside of living organisms. Biogeochemical cycles can be local or global. Student Misconceptions and Concerns Students are unlikely to have any prior knowledge of biogeochemical cycles. Although some transfers between the biotic and abiotic components of ecosystems, such as the use of fertilizer on plants, may be known to them, the broader fact that the biosphere is a self-cycling system is not appreciated by most students. Before you lecture, consider asking your students to explain how carbon, phosphorus, and nitrogen cycle through the atmosphere. Pre-testing your students on their knowledge can confirm both what they understand and what they may need explained to them in more detail. Teaching Tips As you discuss the importance of the biogeochemical cycles, consider explaining the basic label information provided on a container of plant fertilizer. Consider an example that might be used on houseplants, and therefore more likely to be familiar to students. Typically, plant fertilizers contain various forms of nitrogen and phosphorus, which are essential chemicals for growth. © 2012 Pearson Education, Inc. 24

Consumers Producers Decomposers Nutrients available to producers Figure 37.18 Consumers 3 2 Producers Decomposers 1 Nutrients available to producers 4 Figure 37.18 A general model of the biogeochemical cycling of nutrients Abiotic reservoirs Geologic processes 25

37.19 The carbon cycle depends on photosynthesis and respiration Carbon is the major ingredient of all organic molecules and found in the atmosphere, fossil fuels, and dissolved in carbon compounds in the ocean. The return of CO2 to the atmosphere by respiration closely balances its removal by photosynthesis. The carbon cycle is affected by burning wood and fossil fuels. Student Misconceptions and Concerns Students are unlikely to have any prior knowledge of biogeochemical cycles. Although some transfers between the biotic and abiotic components of ecosystems, such as the use of fertilizer on plants, may be known to them, the broader fact that the biosphere is a self-cycling system is not appreciated by most students. Before you lecture, consider asking your students to explain how carbon, phosphorus, and nitrogen cycle through the atmosphere. Pre-testing your students on their knowledge can confirm both what they understand and what they may need explained to them in more detail. Teaching Tips 1. As you discuss the importance of the biogeochemical cycles, consider explaining the basic label information provided on a container of plant fertilizer. Consider an example that might be used on houseplants, and therefore more likely to be familiar to students. Typically, plant fertilizers contain various forms of nitrogen and phosphorus, which are essential chemicals for growth. 2. As rising atmospheric carbon dioxide levels affect global climate, carbon cycling has become an increasingly important issue. If your course will not cover Module 38.5, on global warming, consider including a brief discussion of the topic here. © 2012 Pearson Education, Inc. 26

CO2 in atmosphere Burning Photosynthesis Cellular respiration Figure 37.19 CO2 in atmosphere 5 Burning 3 Photosynthesis Cellular respiration 1 Plants, algae, cyanobacteria Higher-level consumers 2 Wood and fossil fuels Primary consumers Figure 37.19 The carbon cycle Decomposition Wastes; death Plant litter; death 4 Decomposers (soil microbes) Detritus 27

37.20 The phosphorus cycle depends on the weathering of rock Organisms require phosphorus for nucleic acids, phospholipids, and ATP. Student Misconceptions and Concerns Students are unlikely to have any prior knowledge of biogeochemical cycles. Although some transfers between the biotic and abiotic components of ecosystems, such as the use of fertilizer on plants, may be known to them, the broader fact that the biosphere is a self-cycling system is not appreciated by most students. Before you lecture, consider asking your students to explain how carbon, phosphorus, and nitrogen cycle through the atmosphere. Pre-testing your students on their knowledge can confirm both what they understand and what they may need explained to them in more detail. Teaching Tips 1. As you discuss the importance of the biogeochemical cycles, consider explaining the basic label information provided on a container of plant fertilizer. Consider an example that might be used on houseplants, and therefore more likely to be familiar to students. Typically, plant fertilizers contain various forms of nitrogen and phosphorus, which are essential chemicals for growth. 2. Discussing the movements of water through your local community can help students better understand the concept of biogeochemical cycling. You may want to ask students to consider all of the possible inputs of water into your community as well as the possible routes of exit. 3. As noted in Module 37.20, phosphate contamination of aquatic systems typically leads to increased algal growth and potentially disastrous fish kills. © 2012 Pearson Education, Inc. 28

37.20 The phosphorus cycle depends on the weathering of rock The phosphorus cycle does not have an atmospheric component. Rocks are the only source of phosphorus for terrestrial ecosystems. Plants absorb phosphate ions in the soil and build them into organic compounds. Phosphates are returned to the soil by decomposers. Phosphate levels in aquatic ecosystems are typically low enough to be a limiting factor. Student Misconceptions and Concerns Students are unlikely to have any prior knowledge of biogeochemical cycles. Although some transfers between the biotic and abiotic components of ecosystems, such as the use of fertilizer on plants, may be known to them, the broader fact that the biosphere is a self-cycling system is not appreciated by most students. Before you lecture, consider asking your students to explain how carbon, phosphorus, and nitrogen cycle through the atmosphere. Pre-testing your students on their knowledge can confirm both what they understand and what they may need explained to them in more detail. Teaching Tips 1. As you discuss the importance of the biogeochemical cycles, consider explaining the basic label information provided on a container of plant fertilizer. Consider an example that might be used on houseplants, and therefore more likely to be familiar to students. Typically, plant fertilizers contain various forms of nitrogen and phosphorus, which are essential chemicals for growth. 2. Discussing the movements of water through your local community can help students better understand the concept of biogeochemical cycling. You may want to ask students to consider all of the possible inputs of water into your community as well as the possible routes of exit. 3. As noted in Module 37.20, phosphate contamination of aquatic systems typically leads to increased algal growth and potentially disastrous fish kills. © 2012 Pearson Education, Inc. 29

Uplifting of rock Weathering of rock Phosphates in rock Animals Plants Figure 37.20 6 Uplifting of rock 3 Weathering of rock Phosphates in rock Animals Plants Runoff 1 Assimilation Figure 37.20 The phosphorus cycle 2 Phosphates in soil (inorganic) Detritus Phosphates in solution 5 Precipitated (solid) phosphates 4 Decomposers in soil Rock Decomposition 30

37.21 The nitrogen cycle depends on bacteria Nitrogen is an ingredient of proteins and nucleic acids, essential to the structure and functioning of all organisms, and a crucial and often limiting plant nutrient. Nitrogen has two abiotic reservoirs: 1. the atmosphere, of which about 80% is nitrogen gas, and 2. soil. Student Misconceptions and Concerns Students are unlikely to have any prior knowledge of biogeochemical cycles. Although some transfers between the biotic and abiotic components of ecosystems, such as the use of fertilizer on plants, may be known to them, the broader fact that the biosphere is a self-cycling system is not appreciated by most students. Before you lecture, consider asking your students to explain how carbon, phosphorus, and nitrogen cycle through the atmosphere. Pre-testing your students on their knowledge can confirm both what they understand and what they may need explained to them in more detail. Teaching Tips The nitrogen-fixing bacteria living in the roots of soybeans add nitrogen to the soil. Corn does not enjoy this same relationship with bacteria. However, by rotating corn and soybean crops, farmers can allow corn crops to use some of the nitrogen fixed by the soybean crop in the previous year. Such rotation has other benefits. Since corn is a monocot and soybeans are dicots, few pests attack both corn and soybeans. Thus, crop rotation also helps to control the pest populations that target each type of plant, reducing the need for other pest-fighting strategies. © 2012 Pearson Education, Inc. 31

37.21 The nitrogen cycle depends on bacteria Nitrogen fixation converts N2 to compounds of nitrogen that can be used by plants and is carried out by some bacteria. Student Misconceptions and Concerns Students are unlikely to have any prior knowledge of biogeochemical cycles. Although some transfers between the biotic and abiotic components of ecosystems, such as the use of fertilizer on plants, may be known to them, the broader fact that the biosphere is a self-cycling system is not appreciated by most students. Before you lecture, consider asking your students to explain how carbon, phosphorus, and nitrogen cycle through the atmosphere. Pre-testing your students on their knowledge can confirm both what they understand and what they may need explained to them in more detail. Teaching Tips The nitrogen-fixing bacteria living in the roots of soybeans add nitrogen to the soil. Corn does not enjoy this same relationship with bacteria. However, by rotating corn and soybean crops, farmers can allow corn crops to use some of the nitrogen fixed by the soybean crop in the previous year. Such rotation has other benefits. Since corn is a monocot and soybeans are dicots, few pests attack both corn and soybeans. Thus, crop rotation also helps to control the pest populations that target each type of plant, reducing the need for other pest-fighting strategies. © 2012 Pearson Education, Inc. 32

Nitrogen (N2) in atmosphere Figure 37.21 Nitrogen (N2) in atmosphere 8 Plant Animal 6 Assimilation by plants 1 5 Denitrifiers 3 Nitrogen-fixing bacteria in root modules Nitrates in soil (NO3) Detritus Figure 37.21 The nitrogen cycle Decomposers Free-living nitrogen-fixing bacteria Nitrifying bacteria 4 7 Ammonium (NH4) in soil 2 33

Over time, standing water ecosystems 37.22 CONNECTION: A rapid inflow of nutrients degrades aquatic ecosystems In aquatic ecosystems, primary production is limited by low nutrient levels of phosphorus and nitrogen. Over time, standing water ecosystems gradually accumulate nutrients from the decomposition of organic matter and fresh influx from the land, and primary production increases in a process known as eutrophication. Student Misconceptions and Concerns Students are unlikely to have any prior knowledge of biogeochemical cycles. Although some transfers between the biotic and abiotic components of ecosystems, such as the use of fertilizer on plants, may be known to them, the broader fact that the biosphere is a self-cycling system is not appreciated by most students. Before you lecture, consider asking your students to explain how carbon, phosphorus, and nitrogen cycle through the atmosphere. Pre-testing your students on their knowledge can confirm both what they understand and what they may need explained to them in more detail. Teaching Tips The studies of the Hubbard Brook Experimental Forest (described well at www.hubbardbrook.org/ and in the previous edition of this Concepts textbook) provide an opportunity to explain how basic principles of scientific investigation are applied to ecological studies. Consider discussing the difficulties of conducting these broad experiments in other locations, where water cycling may not be so restricted and other biogeochemical cycles not as well defined. © 2012 Pearson Education, Inc. 34

Eutrophication of lakes, rivers, and coastal waters 37.22 CONNECTION: A rapid inflow of nutrients degrades aquatic ecosystems Eutrophication of lakes, rivers, and coastal waters depletes oxygen levels and decreases species diversity. In many areas, phosphate pollution leading to eutrophication comes from agricultural fertilizers, pesticides, sewage treatment facilities, and runoff of animal waste from feedlots Student Misconceptions and Concerns Students are unlikely to have any prior knowledge of biogeochemical cycles. Although some transfers between the biotic and abiotic components of ecosystems, such as the use of fertilizer on plants, may be known to them, the broader fact that the biosphere is a self-cycling system is not appreciated by most students. Before you lecture, consider asking your students to explain how carbon, phosphorus, and nitrogen cycle through the atmosphere. Pre-testing your students on their knowledge can confirm both what they understand and what they may need explained to them in more detail. Teaching Tips The studies of the Hubbard Brook Experimental Forest (described well at www.hubbardbrook.org/ and in the previous edition of this Concepts textbook) provide an opportunity to explain how basic principles of scientific investigation are applied to ecological studies. Consider discussing the difficulties of conducting these broad experiments in other locations, where water cycling may not be so restricted and other biogeochemical cycles not as well defined. © 2012 Pearson Education, Inc. 35

Video: Cyanobacteria (Oscillatoria) 37.22 CONNECTION: A rapid inflow of nutrients degrades aquatic ecosystems Eutrophication of aquatic systems may also result from increased levels of nitrogen from feedlots and applications of large amounts of fertilizer. Student Misconceptions and Concerns Students are unlikely to have any prior knowledge of biogeochemical cycles. Although some transfers between the biotic and abiotic components of ecosystems, such as the use of fertilizer on plants, may be known to them, the broader fact that the biosphere is a self-cycling system is not appreciated by most students. Before you lecture, consider asking your students to explain how carbon, phosphorus, and nitrogen cycle through the atmosphere. Pre-testing your students on their knowledge can confirm both what they understand and what they may need explained to them in more detail. Teaching Tips The studies of the Hubbard Brook Experimental Forest (described well at www.hubbardbrook.org/ and in the previous edition of this Concepts textbook) provide an opportunity to explain how basic principles of scientific investigation are applied to ecological studies. Consider discussing the difficulties of conducting these broad experiments in other locations, where water cycling may not be so restricted and other biogeochemical cycles not as well defined. Video: Cyanobacteria (Oscillatoria) © 2012 Pearson Education, Inc. 36

Figure 37.22A Figure 37.22A Algal growth on a pond resulting from nutrient pollution 37

Winter Summer G u l f o M e x i c G u l f o M e x i c Figure 37.22B Figure 37.22B Concentrations of phytoplankton in winter and summer. Red and orange indicate highest concentrations. Winter Summer 38

Winter x i c M e o f l u G Figure 37.22B_1 Figure 37.22B_1 Concentrations of phytoplankton in winter. Red and orange indicate highest concentrations. (part 1) Winter 39

Summer x i c M e o f l u G Figure 37.22B_2 Figure 37.22B_2 Concentrations of phytoplankton in summer. Red and orange indicate highest concentrations. (part 2) Summer 40

37.23 CONNECTION: Ecosystem services are essential to human well-being Although agricultural and other managed ecosystems are necessary to supply our needs, we also depend on services provided by natural ecosystems. Healthy ecosystems supply fresh water and some foods, recycle nutrients, decompose wastes, and regulate climate and air quality. Student Misconceptions and Concerns Students are unlikely to have any prior knowledge of biogeochemical cycles. Although some transfers between the biotic and abiotic components of ecosystems, such as the use of fertilizer on plants, may be known to them, the broader fact that the biosphere is a self-cycling system is not appreciated by most students. Before you lecture, consider asking your students to explain how carbon, phosphorus, and nitrogen cycle through the atmosphere. Pre-testing your students on their knowledge can confirm both what they understand and what they may need explained to them in more detail. Teaching Tips Most human communities include at least one golf course where heavy chemical applications of fertilizers occur. Discuss with your students the environmental impact of replacing a natural prairie or forested ecosystem with a golf course, noting the change in species diversity and broader ecological impacts of applications of fertilizers and pesticides and the related increase in fossil fuel consumption. Examples from your local community help students immediately relate to the topics of this chapter. © 2012 Pearson Education, Inc. 41

Figure 37.23A Figure 37.23A A dust storm in Changling, China 42

37.23 CONNECTION: Ecosystem services are essential to human well-being Enormous increases in food production have come at the expense of natural ecosystems and the services they provide. Human activities also threaten many forest ecosystems and the services they provide. Student Misconceptions and Concerns Students are unlikely to have any prior knowledge of biogeochemical cycles. Although some transfers between the biotic and abiotic components of ecosystems, such as the use of fertilizer on plants, may be known to them, the broader fact that the biosphere is a self-cycling system is not appreciated by most students. Before you lecture, consider asking your students to explain how carbon, phosphorus, and nitrogen cycle through the atmosphere. Pre-testing your students on their knowledge can confirm both what they understand and what they may need explained to them in more detail. Teaching Tips Most human communities include at least one golf course where heavy chemical applications of fertilizers occur. Discuss with your students the environmental impact of replacing a natural prairie or forested ecosystem with a golf course, noting the change in species diversity and broader ecological impacts of applications of fertilizers and pesticides and the related increase in fossil fuel consumption. Examples from your local community help students immediately relate to the topics of this chapter. © 2012 Pearson Education, Inc. 43

Figure 37.23B Figure 37.23B A woman in Haiti gathering wood to process into charcoal 44

You should now be able to Define a biological community. Explain why the study of community ecology is important. Define interspecific competition, mutualism, predation, herbivory, and parasitism, and provide examples of each. Define an ecological niche. Explain how interspecific competition can occur when the niches of two populations overlap. Describe the mutualistic relationship between corals and dinoflagellates. Define predation. Describe the protective strategies potential prey employ to avoid predators. © 2012 Pearson Education, Inc. 45

You should now be able to Explain why many plants have chemical toxins, spines, or thorns. Define coevolution and describe an example. Explain how parasites and pathogens can affect community composition. Identify and compare the trophic levels of terrestrial and aquatic food chains. Explain how food chains interconnect to form food webs. Describe the two components of species diversity. Define a keystone species. © 2012 Pearson Education, Inc. 46

You should now be able to Explain how disturbances can benefit communities. Distinguish between primary and secondary succession. Explain how invasive species can affect communities. Compare the movement of energy and chemicals within and through ecosystems. Compare the primary production of tropical rain forests, coral reefs, and open ocean. Explain why the differences between them exist. Describe the movement of energy through a food chain. © 2012 Pearson Education, Inc. 47

You should now be able to Explain how carbon, nitrogen, and phosphorus cycle within ecosystems. Explain how rapid eutrophication of aquatic ecosystems affects species diversity and oxygen levels. Explain how human activities are threatening natural ecosystems. © 2012 Pearson Education, Inc. 48

Quaternary consumers Tertiary consumers Secondary consumers Primary Figure 37.UN01 Quaternary consumers Tertiary consumers Secondary consumers Figure 37.UN01 Reviewing the Concepts, 37.8 Primary consumers Producers 49

Autotrophs Heterotrophs Producer Herbivore (primary consumer) Figure 37.UN02 Autotrophs Heterotrophs Producer Herbivore (primary consumer) Carnivore (secondary consumer) Energy Light Chemical elements Detritus Figure 37.UN02 Reviewing the Concepts, 37.14 Decomposer Inorganic compounds (chemical elements) 50

Approximately 90% loss of energy at each trophic level Energy Figure 37.UN03 Approximately 90% loss of energy at each trophic level Figure 37.UN03 Reviewing the Concepts, 37.16 Energy 51

Figure 37.UN04 Figure 37.UN04 Connecting the Concepts, question 1 52

Figure 37.UN05 Figure 37.UN05 Connecting the Concepts, question 2 53