Communities and Ecosystems Chapter 20 Communities and Ecosystems

Biology and Society: Does Biodiversity Matter? The expanding human population threatens Biodiversity The loss of natural ecosystems Biological diversity, or biodiversity, includes Genetic diversity Species diversity Ecosystem diversity © 2010 Pearson Education, Inc.

Figure 20.00 Enjoying nature

Healthy ecosystems Wetlands Purify air and water Decompose wastes Recycle nutrients Wetlands Buffer coastal populations against hurricanes Reduce the impact of flooding rivers Filter pollutants It is estimated that the average annual value of ecosystem services each year in the United States is more than $33 trillion.

Genetic Diversity The genetic diversity within populations of a species is the raw material that makes microevolution and adaptation to the environment possible. Genetic resources for that species are lost if Local populations are lost The number of individuals in a species declines The present rate of species loss May be 1,000 times higher than at any time in the past 100,000 years May result in the loss of half of all living plant and animal species by the end of this century Student Misconceptions and Concerns 1. The value of biodiversity may not be obvious to many students. As this chapter notes, biodiversity is inherently valuable on many levels. Class discussions and short assignments that require students to investigate the importance of biodiversity can help to better relate its importance. 2. Frustration can overwhelm concerned students alarmed by the loss of biodiversity. One way to address this is to provide meaningful ways for students to respond to this information. Several related websites are noted in the Teaching Tips below. Teaching Tips 1. Consider referencing some of the following websites for basic ideas on what individuals can do to help address the loss of biodiversity. Conservation International: www.conservation.org/act/simplesteps/Pages/simplesteps.aspx www.biodiversityhotspots.org/ The Biodiversity Economics Site: www.biodiversityeconomics.org/index.html Biodiversity Support Program: www.worldwildlife.org/bsp/ 2. The bottleneck effect, a consequence of the loss of diversity within a species, is discussed in Chapter 13. 3. You might wish to note the mission of the Nature Conservancy, an organization devoted to the purchase and protection of land across the world. The Nature Conservancy’s web site is (www.nature.org/).

Figure 20.1 Einkorn wheat, one of the wild relatives of modern cultivated varieties

Two recent victims of human-caused extinctions are Chinese river dolphins Golden toads Student Misconceptions and Concerns 1. The value of biodiversity may not be obvious to many students. As this chapter notes, biodiversity is inherently valuable on many levels. Class discussions and short assignments that require students to investigate the importance of biodiversity can help to better relate its importance. 2. Frustration can overwhelm concerned students alarmed by the loss of biodiversity. One way to address this is to provide meaningful ways for students to respond to this information. Several related websites are noted in the Teaching Tips below. Teaching Tips 1. Consider referencing some of the following websites for basic ideas on what individuals can do to help address the loss of biodiversity. Conservation International: www.conservation.org/act/simplesteps/Pages/simplesteps.aspx www.biodiversityhotspots.org/ The Biodiversity Economics Site: www.biodiversityeconomics.org/index.html Biodiversity Support Program: www.worldwildlife.org/bsp/ 2. The bottleneck effect, a consequence of the loss of diversity within a species, is discussed in Chapter 13. 3. You might wish to note the mission of the Nature Conservancy, an organization devoted to the purchase and protection of land across the world. The Nature Conservancy’s web site is (www.nature.org/).

Ecosystem Diversity The local extinction of one species can have a negative effect on the entire ecosystem. The loss of ecosystems risks the loss of ecosystem services, including Air and water purification Climate regulation Erosion control Student Misconceptions and Concerns 1. The value of biodiversity may not be obvious to many students. As this chapter notes, biodiversity is inherently valuable on many levels. Class discussions and short assignments that require students to investigate the importance of biodiversity can help to better relate its importance. 2. Frustration can overwhelm concerned students alarmed by the loss of biodiversity. One way to address this is to provide meaningful ways for students to respond to this information. Several related websites are noted in the Teaching Tips below. Teaching Tips 1. Consider referencing some of the following websites for basic ideas on what individuals can do to help address the loss of biodiversity. Conservation International: www.conservation.org/act/simplesteps/Pages/simplesteps.aspx www.biodiversityhotspots.org/ The Biodiversity Economics Site: www.biodiversityeconomics.org/index.html Biodiversity Support Program: www.worldwildlife.org/bsp/ 2. The bottleneck effect, a consequence of the loss of diversity within a species, is discussed in Chapter 13. 3. You might wish to note the mission of the Nature Conservancy, an organization devoted to the purchase and protection of land across the world. The Nature Conservancy’s web site is (www.nature.org/).

Coral reefs are rich in species diversity, yet An estimated 20% of the world’s coral reefs have been destroyed by human activities 24% are in imminent danger of collapse Another 26% of coral reefs may succumb in the next few decades if they are not protected Student Misconceptions and Concerns 1. The value of biodiversity may not be obvious to many students. As this chapter notes, biodiversity is inherently valuable on many levels. Class discussions and short assignments that require students to investigate the importance of biodiversity can help to better relate its importance. 2. Frustration can overwhelm concerned students alarmed by the loss of biodiversity. One way to address this is to provide meaningful ways for students to respond to this information. Several related websites are noted in the Teaching Tips below. Teaching Tips 1. Consider referencing some of the following websites for basic ideas on what individuals can do to help address the loss of biodiversity. Conservation International: www.conservation.org/act/simplesteps/Pages/simplesteps.aspx www.biodiversityhotspots.org/ The Biodiversity Economics Site: www.biodiversityeconomics.org/index.html Biodiversity Support Program: www.worldwildlife.org/bsp/ 2. The bottleneck effect, a consequence of the loss of diversity within a species, is discussed in Chapter 13. 3. You might wish to note the mission of the Nature Conservancy, an organization devoted to the purchase and protection of land across the world. The Nature Conservancy’s web site is (www.nature.org/).

Figure 20.3 Coral reef, a colorful display of biodiversity

Causes of Declining Biodiversity Ecologists have identified four main factors responsible for the loss of biodiversity: Habitat destruction and fragmentation Invasive species Overexploitation Pollution Student Misconceptions and Concerns 1. The value of biodiversity may not be obvious to many students. As this chapter notes, biodiversity is inherently valuable on many levels. Class discussions and short assignments that require students to investigate the importance of biodiversity can help to better relate its importance. 2. Frustration can overwhelm concerned students alarmed by the loss of biodiversity. One way to address this is to provide meaningful ways for students to respond to this information. Several related websites are noted in the Teaching Tips below. Teaching Tips 1. Consider referencing some of the following websites for basic ideas on what individuals can do to help address the loss of biodiversity. Conservation International: www.conservation.org/act/simplesteps/Pages/simplesteps.aspx www.biodiversityhotspots.org/ The Biodiversity Economics Site: www.biodiversityeconomics.org/index.html Biodiversity Support Program: www.worldwildlife.org/bsp/ 2. The bottleneck effect, a consequence of the loss of diversity within a species, is discussed in Chapter 13. 3. You might wish to note the mission of the Nature Conservancy, an organization devoted to the purchase and protection of land across the world. The Nature Conservancy’s web site is (www.nature.org/).

Habitat Destruction Biodiversity is threatened by the destruction and fragmentation of habitats by Agriculture Urban development Forestry Mining Student Misconceptions and Concerns 1. The value of biodiversity may not be obvious to many students. As this chapter notes, biodiversity is inherently valuable on many levels. Class discussions and short assignments that require students to investigate the importance of biodiversity can help to better relate its importance. 2. Frustration can overwhelm concerned students alarmed by the loss of biodiversity. One way to address this is to provide meaningful ways for students to respond to this information. Several related websites are noted in the Teaching Tips below. Teaching Tips 1. Consider referencing some of the following websites for basic ideas on what individuals can do to help address the loss of biodiversity. Conservation International: www.conservation.org/act/simplesteps/Pages/simplesteps.aspx www.biodiversityhotspots.org/ The Biodiversity Economics Site: www.biodiversityeconomics.org/index.html Biodiversity Support Program: www.worldwildlife.org/bsp/ 2. The bottleneck effect, a consequence of the loss of diversity within a species, is discussed in Chapter 13. 3. You might wish to note the mission of the Nature Conservancy, an organization devoted to the purchase and protection of land across the world. The Nature Conservancy’s web site is (www.nature.org/).

Figure 20.4 Habitat destruction

Figure 20.5 Bluefin tuna ready for sale

Pollution Acid precipitation is a threat to Forest ecosystems and Aquatic ecosystems Aquatic ecosystems are polluted by toxic chemicals and nutrients Student Misconceptions and Concerns 1. The value of biodiversity may not be obvious to many students. As this chapter notes, biodiversity is inherently valuable on many levels. Class discussions and short assignments that require students to investigate the importance of biodiversity can help to better relate its importance. 2. Frustration can overwhelm concerned students alarmed by the loss of biodiversity. One way to address this is to provide meaningful ways for students to respond to this information. Several related websites are noted in the Teaching Tips below. Teaching Tips 1. Consider referencing some of the following websites for basic ideas on what individuals can do to help address the loss of biodiversity. Conservation International: www.conservation.org/act/simplesteps/Pages/simplesteps.aspx www.biodiversityhotspots.org/ The Biodiversity Economics Site: www.biodiversityeconomics.org/index.html Biodiversity Support Program: www.worldwildlife.org/bsp/ 2. The bottleneck effect, a consequence of the loss of diversity within a species, is discussed in Chapter 13. 3. You might wish to note the mission of the Nature Conservancy, an organization devoted to the purchase and protection of land across the world. The Nature Conservancy’s web site is (www.nature.org/).

Interspecific Interactions An organism’s biotic environment includes Other individuals in its own population Populations of other species living in the same area Interspecific interactions are interactions between species. Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. They can see ecosystems and art, but they do not understand the composition, the significance of the components, and the nature of their interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. 2. The concept of an ecological niche can be confusing. Ecologist Eugene Odum suggested that an ecological niche is like an organism’s habitat (address) and its occupation combined. 3. Students often mistakenly think that symbiosis is a synonym for mutualism. Mutualism is a form of symbiosis. 4. The expectation that ecosystems are relatively stable is common. Natural disturbances of any sort (fires, earthquakes, floods, or strong storms) are typically viewed as tragic and damaging to ecosystems. Before beginning the topic of ecological disturbances, consider asking your students to briefly respond to news that a state or federal park has a) been burned, b) been struck by high winds and/or lightning, or c) been temporarily flooded. In addition, consider asking what if anything should be done to prevent or repair this damage? Teaching Tips 1. For many students, their interactions with diverse ecosystems have been limited to videos and movies, 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 common experience of the students to which you can refer and relate the content of this chapter. 2. Alternately, you can relate some of the basics of this chapter to a local campus or regional example to which most students are familiar. Perhaps there is a distinct community on your campus: a pond, distinct wooded area, or other part of campus that students would know and could visit with new insight. 3. In human society, a community might be considered about the same as a local population, perhaps all the people living in a town or city. The definition of a biological community is more inclusive, comprising all of the populations of species living close enough together for potential interaction. 4. Examples of interspecific competition are as close as the nearest lawn. Although students may be more likely to think of animal examples, the various grasses and weeds in a lawn reveal different strategies in their competition for sunlight, moisture, and soil. 5. If your class includes students with business interests, they may enjoy the following analogy. To better understand competition, students might think about fast-food restaurants in your region, perhaps those that sell pizzas. Challenge your students to identify strategies employed by these restaurants to compete with each other. As each restaurant makes changes, how do the other restaurants respond? Restaurants changing strategies in response to each other is analogous to coevolution. 6. Students commonly have practice with food webs and food chains. Present a food web (perhaps Figure 20.18) to your class and challenge them to predict the consequences of a decrease or increase in the population of one of the organisms. This activity can help students understand how difficult it is to make precise predictions about these complex systems. 7. Many keystone species have been identified in ecosystems, including sea otters, elephants, freshwater bass, and Pisaster, a sea star noted in Figure 20.21. Challenge your class to explain how the concept of a keystone species relates to the efforts of conservation biologists. Why might some species be more important to conserve? 8. Before and after images of the impact and recovery of an ecosystem from a natural disaster can be as powerful as any explanation of the process. 9. Challenge your students to think through the adaptive advantage of a warning coloration in a toxic animal. Challenge your students to explain: What is gained if the predator dies? How can such systems evolve is the model is killed in the learning experience? 10. Students who are business-oriented might enjoy this analogy. Many corporate leaders might describe the best business deals as those that are mutualistic, fostering a win-win relationship.

Figure 20.6 Diverse species interacting in a Kenyan savanna community

Interspecific interactions can be classified according to the effect on the populations concerned. –/– interactions occur when two populations in a community compete for a common resource. +/+ interactions are mutually beneficial, such as between plants and their pollinators. +/– interactions occur when one population benefits and the other is harmed, such as in predation. In interspecific (between species) competition, the population growth of a species may be limited by The population densities of competing species By the density of its own population Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. They can see ecosystems and art, but they do not understand the composition, the significance of the components, and the nature of their interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. 2. The concept of an ecological niche can be confusing. Ecologist Eugene Odum suggested that an ecological niche is like an organism’s habitat (address) and its occupation combined. 3. Students often mistakenly think that symbiosis is a synonym for mutualism. Mutualism is a form of symbiosis. 4. The expectation that ecosystems are relatively stable is common. Natural disturbances of any sort (fires, earthquakes, floods, or strong storms) are typically viewed as tragic and damaging to ecosystems. Before beginning the topic of ecological disturbances, consider asking your students to briefly respond to news that a state or federal park has a) been burned, b) been struck by high winds and/or lightning, or c) been temporarily flooded. In addition, consider asking what if anything should be done to prevent or repair this damage? Teaching Tips 1. For many students, their interactions with diverse ecosystems have been limited to videos and movies, 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 common experience of the students to which you can refer and relate the content of this chapter. 2. Alternately, you can relate some of the basics of this chapter to a local campus or regional example to which most students are familiar. Perhaps there is a distinct community on your campus: a pond, distinct wooded area, or other part of campus that students would know and could visit with new insight. 3. In human society, a community might be considered about the same as a local population, perhaps all the people living in a town or city. The definition of a biological community is more inclusive, comprising all of the populations of species living close enough together for potential interaction. 4. Examples of interspecific competition are as close as the nearest lawn. Although students may be more likely to think of animal examples, the various grasses and weeds in a lawn reveal different strategies in their competition for sunlight, moisture, and soil. 5. If your class includes students with business interests, they may enjoy the following analogy. To better understand competition, students might think about fast-food restaurants in your region, perhaps those that sell pizzas. Challenge your students to identify strategies employed by these restaurants to compete with each other. As each restaurant makes changes, how do the other restaurants respond? Restaurants changing strategies in response to each other is analogous to coevolution. 6. Students commonly have practice with food webs and food chains. Present a food web (perhaps Figure 20.18) to your class and challenge them to predict the consequences of a decrease or increase in the population of one of the organisms. This activity can help students understand how difficult it is to make precise predictions about these complex systems. 7. Many keystone species have been identified in ecosystems, including sea otters, elephants, freshwater bass, and Pisaster, a sea star noted in Figure 20.21. Challenge your class to explain how the concept of a keystone species relates to the efforts of conservation biologists. Why might some species be more important to conserve? 8. Before and after images of the impact and recovery of an ecosystem from a natural disaster can be as powerful as any explanation of the process. 9. Challenge your students to think through the adaptive advantage of a warning coloration in a toxic animal. Challenge your students to explain: What is gained if the predator dies? How can such systems evolve is the model is killed in the learning experience? 10. Students who are business-oriented might enjoy this analogy. Many corporate leaders might describe the best business deals as those that are mutualistic, fostering a win-win relationship.

An ecological niche is the sum of an organism’s abiotic and biotic resources in its environment. The competitive exclusion principle states that if two species have an ecological niche that is too similar, the two species cannot coexist in the same place. Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. They can see ecosystems and art, but they do not understand the composition, the significance of the components, and the nature of their interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. 2. The concept of an ecological niche can be confusing. Ecologist Eugene Odum suggested that an ecological niche is like an organism’s habitat (address) and its occupation combined. 3. Students often mistakenly think that symbiosis is a synonym for mutualism. Mutualism is a form of symbiosis. 4. The expectation that ecosystems are relatively stable is common. Natural disturbances of any sort (fires, earthquakes, floods, or strong storms) are typically viewed as tragic and damaging to ecosystems. Before beginning the topic of ecological disturbances, consider asking your students to briefly respond to news that a state or federal park has a) been burned, b) been struck by high winds and/or lightning, or c) been temporarily flooded. In addition, consider asking what if anything should be done to prevent or repair this damage? Teaching Tips 1. For many students, their interactions with diverse ecosystems have been limited to videos and movies, 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 common experience of the students to which you can refer and relate the content of this chapter. 2. Alternately, you can relate some of the basics of this chapter to a local campus or regional example to which most students are familiar. Perhaps there is a distinct community on your campus: a pond, distinct wooded area, or other part of campus that students would know and could visit with new insight. 3. In human society, a community might be considered about the same as a local population, perhaps all the people living in a town or city. The definition of a biological community is more inclusive, comprising all of the populations of species living close enough together for potential interaction. 4. Examples of interspecific competition are as close as the nearest lawn. Although students may be more likely to think of animal examples, the various grasses and weeds in a lawn reveal different strategies in their competition for sunlight, moisture, and soil. 5. If your class includes students with business interests, they may enjoy the following analogy. To better understand competition, students might think about fast-food restaurants in your region, perhaps those that sell pizzas. Challenge your students to identify strategies employed by these restaurants to compete with each other. As each restaurant makes changes, how do the other restaurants respond? Restaurants changing strategies in response to each other is analogous to coevolution. 6. Students commonly have practice with food webs and food chains. Present a food web (perhaps Figure 20.18) to your class and challenge them to predict the consequences of a decrease or increase in the population of one of the organisms. This activity can help students understand how difficult it is to make precise predictions about these complex systems. 7. Many keystone species have been identified in ecosystems, including sea otters, elephants, freshwater bass, and Pisaster, a sea star noted in Figure 20.21. Challenge your class to explain how the concept of a keystone species relates to the efforts of conservation biologists. Why might some species be more important to conserve? 8. Before and after images of the impact and recovery of an ecosystem from a natural disaster can be as powerful as any explanation of the process. 9. Challenge your students to think through the adaptive advantage of a warning coloration in a toxic animal. Challenge your students to explain: What is gained if the predator dies? How can such systems evolve is the model is killed in the learning experience? 10. Students who are business-oriented might enjoy this analogy. Many corporate leaders might describe the best business deals as those that are mutualistic, fostering a win-win relationship.

(a) Virginia’s warbler (b) Orange-crowned warbler Figure 20.7 Species that use similar resources (a) Virginia’s warbler (b) Orange-crowned warbler Figure 20.7

Relative population density LM Separate cultures Relative population density Paramecium aurelia Combined cultures 2 4 6 8 10 12 14 16 LM Figure 20.8 Competitive exclusion in laboratoy populations of Paramecium Days P. aurelia P. caudatum Paramecium caudatum Figure 20.8

Mutualism (+/+) In mutualism, both species benefit from an interaction. One example is the mutualistic relationship of coral animals and the unicellular algae that live inside their cells. The coral gains energy from the sugars produced by the algae. The algae gain A secure shelter Access to light Carbon dioxide Ammonia, a valuable source of nitrogen Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. They can see ecosystems and art, but they do not understand the composition, the significance of the components, and the nature of their interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. 2. The concept of an ecological niche can be confusing. Ecologist Eugene Odum suggested that an ecological niche is like an organism’s habitat (address) and its occupation combined. 3. Students often mistakenly think that symbiosis is a synonym for mutualism. Mutualism is a form of symbiosis. 4. The expectation that ecosystems are relatively stable is common. Natural disturbances of any sort (fires, earthquakes, floods, or strong storms) are typically viewed as tragic and damaging to ecosystems. Before beginning the topic of ecological disturbances, consider asking your students to briefly respond to news that a state or federal park has a) been burned, b) been struck by high winds and/or lightning, or c) been temporarily flooded. In addition, consider asking what if anything should be done to prevent or repair this damage? Teaching Tips 1. For many students, their interactions with diverse ecosystems have been limited to videos and movies, 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 common experience of the students to which you can refer and relate the content of this chapter. 2. Alternately, you can relate some of the basics of this chapter to a local campus or regional example to which most students are familiar. Perhaps there is a distinct community on your campus: a pond, distinct wooded area, or other part of campus that students would know and could visit with new insight. 3. In human society, a community might be considered about the same as a local population, perhaps all the people living in a town or city. The definition of a biological community is more inclusive, comprising all of the populations of species living close enough together for potential interaction. 4. Examples of interspecific competition are as close as the nearest lawn. Although students may be more likely to think of animal examples, the various grasses and weeds in a lawn reveal different strategies in their competition for sunlight, moisture, and soil. 5. If your class includes students with business interests, they may enjoy the following analogy. To better understand competition, students might think about fast-food restaurants in your region, perhaps those that sell pizzas. Challenge your students to identify strategies employed by these restaurants to compete with each other. As each restaurant makes changes, how do the other restaurants respond? Restaurants changing strategies in response to each other is analogous to coevolution. 6. Students commonly have practice with food webs and food chains. Present a food web (perhaps Figure 20.18) to your class and challenge them to predict the consequences of a decrease or increase in the population of one of the organisms. This activity can help students understand how difficult it is to make precise predictions about these complex systems. 7. Many keystone species have been identified in ecosystems, including sea otters, elephants, freshwater bass, and Pisaster, a sea star noted in Figure 20.21. Challenge your class to explain how the concept of a keystone species relates to the efforts of conservation biologists. Why might some species be more important to conserve? 8. Before and after images of the impact and recovery of an ecosystem from a natural disaster can be as powerful as any explanation of the process. 9. Challenge your students to think through the adaptive advantage of a warning coloration in a toxic animal. Challenge your students to explain: What is gained if the predator dies? How can such systems evolve is the model is killed in the learning experience? 10. Students who are business-oriented might enjoy this analogy. Many corporate leaders might describe the best business deals as those that are mutualistic, fostering a win-win relationship.

Figure 20.9 Mutualism Figure 20.9

Predation (+/–) Predation refers to an interaction in which one species (the predator) kills and eats another (the prey). Numerous adaptations for predator avoidance have evolved in prey populations through natural selection. Cryptic coloration is Camouflage A way for prey to hide from predators A warning coloration is a Brightly colored pattern Way to warn predators that an animal has an effective chemical defense Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. They can see ecosystems and art, but they do not understand the composition, the significance of the components, and the nature of their interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. 2. The concept of an ecological niche can be confusing. Ecologist Eugene Odum suggested that an ecological niche is like an organism’s habitat (address) and its occupation combined. 3. Students often mistakenly think that symbiosis is a synonym for mutualism. Mutualism is a form of symbiosis. 4. The expectation that ecosystems are relatively stable is common. Natural disturbances of any sort (fires, earthquakes, floods, or strong storms) are typically viewed as tragic and damaging to ecosystems. Before beginning the topic of ecological disturbances, consider asking your students to briefly respond to news that a state or federal park has a) been burned, b) been struck by high winds and/or lightning, or c) been temporarily flooded. In addition, consider asking what if anything should be done to prevent or repair this damage? Teaching Tips 1. For many students, their interactions with diverse ecosystems have been limited to videos and movies, 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 common experience of the students to which you can refer and relate the content of this chapter. 2. Alternately, you can relate some of the basics of this chapter to a local campus or regional example to which most students are familiar. Perhaps there is a distinct community on your campus: a pond, distinct wooded area, or other part of campus that students would know and could visit with new insight. 3. In human society, a community might be considered about the same as a local population, perhaps all the people living in a town or city. The definition of a biological community is more inclusive, comprising all of the populations of species living close enough together for potential interaction. 4. Examples of interspecific competition are as close as the nearest lawn. Although students may be more likely to think of animal examples, the various grasses and weeds in a lawn reveal different strategies in their competition for sunlight, moisture, and soil. 5. If your class includes students with business interests, they may enjoy the following analogy. To better understand competition, students might think about fast-food restaurants in your region, perhaps those that sell pizzas. Challenge your students to identify strategies employed by these restaurants to compete with each other. As each restaurant makes changes, how do the other restaurants respond? Restaurants changing strategies in response to each other is analogous to coevolution. 6. Students commonly have practice with food webs and food chains. Present a food web (perhaps Figure 20.18) to your class and challenge them to predict the consequences of a decrease or increase in the population of one of the organisms. This activity can help students understand how difficult it is to make precise predictions about these complex systems. 7. Many keystone species have been identified in ecosystems, including sea otters, elephants, freshwater bass, and Pisaster, a sea star noted in Figure 20.21. Challenge your class to explain how the concept of a keystone species relates to the efforts of conservation biologists. Why might some species be more important to conserve? 8. Before and after images of the impact and recovery of an ecosystem from a natural disaster can be as powerful as any explanation of the process. 9. Challenge your students to think through the adaptive advantage of a warning coloration in a toxic animal. Challenge your students to explain: What is gained if the predator dies? How can such systems evolve is the model is killed in the learning experience? 10. Students who are business-oriented might enjoy this analogy. Many corporate leaders might describe the best business deals as those that are mutualistic, fostering a win-win relationship.

Figure 20.10 Cryptic coloration

Figure 20.11 Warning coloration of a poison dart frog

Mimicry is a form of defense in which one animal looks like another species. Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. They can see ecosystems and art, but they do not understand the composition, the significance of the components, and the nature of their interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. 2. The concept of an ecological niche can be confusing. Ecologist Eugene Odum suggested that an ecological niche is like an organism’s habitat (address) and its occupation combined. 3. Students often mistakenly think that symbiosis is a synonym for mutualism. Mutualism is a form of symbiosis. 4. The expectation that ecosystems are relatively stable is common. Natural disturbances of any sort (fires, earthquakes, floods, or strong storms) are typically viewed as tragic and damaging to ecosystems. Before beginning the topic of ecological disturbances, consider asking your students to briefly respond to news that a state or federal park has a) been burned, b) been struck by high winds and/or lightning, or c) been temporarily flooded. In addition, consider asking what if anything should be done to prevent or repair this damage? Teaching Tips 1. For many students, their interactions with diverse ecosystems have been limited to videos and movies, 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 common experience of the students to which you can refer and relate the content of this chapter. 2. Alternately, you can relate some of the basics of this chapter to a local campus or regional example to which most students are familiar. Perhaps there is a distinct community on your campus: a pond, distinct wooded area, or other part of campus that students would know and could visit with new insight. 3. In human society, a community might be considered about the same as a local population, perhaps all the people living in a town or city. The definition of a biological community is more inclusive, comprising all of the populations of species living close enough together for potential interaction. 4. Examples of interspecific competition are as close as the nearest lawn. Although students may be more likely to think of animal examples, the various grasses and weeds in a lawn reveal different strategies in their competition for sunlight, moisture, and soil. 5. If your class includes students with business interests, they may enjoy the following analogy. To better understand competition, students might think about fast-food restaurants in your region, perhaps those that sell pizzas. Challenge your students to identify strategies employed by these restaurants to compete with each other. As each restaurant makes changes, how do the other restaurants respond? Restaurants changing strategies in response to each other is analogous to coevolution. 6. Students commonly have practice with food webs and food chains. Present a food web (perhaps Figure 20.18) to your class and challenge them to predict the consequences of a decrease or increase in the population of one of the organisms. This activity can help students understand how difficult it is to make precise predictions about these complex systems. 7. Many keystone species have been identified in ecosystems, including sea otters, elephants, freshwater bass, and Pisaster, a sea star noted in Figure 20.21. Challenge your class to explain how the concept of a keystone species relates to the efforts of conservation biologists. Why might some species be more important to conserve? 8. Before and after images of the impact and recovery of an ecosystem from a natural disaster can be as powerful as any explanation of the process. 9. Challenge your students to think through the adaptive advantage of a warning coloration in a toxic animal. Challenge your students to explain: What is gained if the predator dies? How can such systems evolve is the model is killed in the learning experience? 10. Students who are business-oriented might enjoy this analogy. Many corporate leaders might describe the best business deals as those that are mutualistic, fostering a win-win relationship.

Herbivory (+/–) Herbivory is the consumption of plant parts or algae by an animal. Plants have evolved numerous defenses against herbivory, including Spines Thorns Chemical toxins Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. They can see ecosystems and art, but they do not understand the composition, the significance of the components, and the nature of their interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. 2. The concept of an ecological niche can be confusing. Ecologist Eugene Odum suggested that an ecological niche is like an organism’s habitat (address) and its occupation combined. 3. Students often mistakenly think that symbiosis is a synonym for mutualism. Mutualism is a form of symbiosis. 4. The expectation that ecosystems are relatively stable is common. Natural disturbances of any sort (fires, earthquakes, floods, or strong storms) are typically viewed as tragic and damaging to ecosystems. Before beginning the topic of ecological disturbances, consider asking your students to briefly respond to news that a state or federal park has a) been burned, b) been struck by high winds and/or lightning, or c) been temporarily flooded. In addition, consider asking what if anything should be done to prevent or repair this damage? Teaching Tips 1. For many students, their interactions with diverse ecosystems have been limited to videos and movies, 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 common experience of the students to which you can refer and relate the content of this chapter. 2. Alternately, you can relate some of the basics of this chapter to a local campus or regional example to which most students are familiar. Perhaps there is a distinct community on your campus: a pond, distinct wooded area, or other part of campus that students would know and could visit with new insight. 3. In human society, a community might be considered about the same as a local population, perhaps all the people living in a town or city. The definition of a biological community is more inclusive, comprising all of the populations of species living close enough together for potential interaction. 4. Examples of interspecific competition are as close as the nearest lawn. Although students may be more likely to think of animal examples, the various grasses and weeds in a lawn reveal different strategies in their competition for sunlight, moisture, and soil. 5. If your class includes students with business interests, they may enjoy the following analogy. To better understand competition, students might think about fast-food restaurants in your region, perhaps those that sell pizzas. Challenge your students to identify strategies employed by these restaurants to compete with each other. As each restaurant makes changes, how do the other restaurants respond? Restaurants changing strategies in response to each other is analogous to coevolution. 6. Students commonly have practice with food webs and food chains. Present a food web (perhaps Figure 20.18) to your class and challenge them to predict the consequences of a decrease or increase in the population of one of the organisms. This activity can help students understand how difficult it is to make precise predictions about these complex systems. 7. Many keystone species have been identified in ecosystems, including sea otters, elephants, freshwater bass, and Pisaster, a sea star noted in Figure 20.21. Challenge your class to explain how the concept of a keystone species relates to the efforts of conservation biologists. Why might some species be more important to conserve? 8. Before and after images of the impact and recovery of an ecosystem from a natural disaster can be as powerful as any explanation of the process. 9. Challenge your students to think through the adaptive advantage of a warning coloration in a toxic animal. Challenge your students to explain: What is gained if the predator dies? How can such systems evolve is the model is killed in the learning experience? 10. Students who are business-oriented might enjoy this analogy. Many corporate leaders might describe the best business deals as those that are mutualistic, fostering a win-win relationship.

Parasites and Pathogens (+/–) Plants and animals can be victims of Parasites, an animal that lives in or on a host from which it obtains nutrients Pathogens, disease-causing Bacteria Viruses Fungi Protists Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. They can see ecosystems and art, but they do not understand the composition, the significance of the components, and the nature of their interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. 2. The concept of an ecological niche can be confusing. Ecologist Eugene Odum suggested that an ecological niche is like an organism’s habitat (address) and its occupation combined. 3. Students often mistakenly think that symbiosis is a synonym for mutualism. Mutualism is a form of symbiosis. 4. The expectation that ecosystems are relatively stable is common. Natural disturbances of any sort (fires, earthquakes, floods, or strong storms) are typically viewed as tragic and damaging to ecosystems. Before beginning the topic of ecological disturbances, consider asking your students to briefly respond to news that a state or federal park has a) been burned, b) been struck by high winds and/or lightning, or c) been temporarily flooded. In addition, consider asking what if anything should be done to prevent or repair this damage? Teaching Tips 1. For many students, their interactions with diverse ecosystems have been limited to videos and movies, 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 common experience of the students to which you can refer and relate the content of this chapter. 2. Alternately, you can relate some of the basics of this chapter to a local campus or regional example to which most students are familiar. Perhaps there is a distinct community on your campus: a pond, distinct wooded area, or other part of campus that students would know and could visit with new insight. 3. In human society, a community might be considered about the same as a local population, perhaps all the people living in a town or city. The definition of a biological community is more inclusive, comprising all of the populations of species living close enough together for potential interaction. 4. Examples of interspecific competition are as close as the nearest lawn. Although students may be more likely to think of animal examples, the various grasses and weeds in a lawn reveal different strategies in their competition for sunlight, moisture, and soil. 5. If your class includes students with business interests, they may enjoy the following analogy. To better understand competition, students might think about fast-food restaurants in your region, perhaps those that sell pizzas. Challenge your students to identify strategies employed by these restaurants to compete with each other. As each restaurant makes changes, how do the other restaurants respond? Restaurants changing strategies in response to each other is analogous to coevolution. 6. Students commonly have practice with food webs and food chains. Present a food web (perhaps Figure 20.18) to your class and challenge them to predict the consequences of a decrease or increase in the population of one of the organisms. This activity can help students understand how difficult it is to make precise predictions about these complex systems. 7. Many keystone species have been identified in ecosystems, including sea otters, elephants, freshwater bass, and Pisaster, a sea star noted in Figure 20.21. Challenge your class to explain how the concept of a keystone species relates to the efforts of conservation biologists. Why might some species be more important to conserve? 8. Before and after images of the impact and recovery of an ecosystem from a natural disaster can be as powerful as any explanation of the process. 9. Challenge your students to think through the adaptive advantage of a warning coloration in a toxic animal. Challenge your students to explain: What is gained if the predator dies? How can such systems evolve is the model is killed in the learning experience? 10. Students who are business-oriented might enjoy this analogy. Many corporate leaders might describe the best business deals as those that are mutualistic, fostering a win-win relationship.

Trophic Structure Trophic structure is the feeding relationships among the various species in a community. A community’s trophic structure determines the passage of energy and nutrients from plants and other photosynthetic organisms To herbivores And then to predators The trophic level that supports all other trophic levels consists of autotrophs, also called producers. Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. They can see ecosystems and art, but they do not understand the composition, the significance of the components, and the nature of their interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. 2. The concept of an ecological niche can be confusing. Ecologist Eugene Odum suggested that an ecological niche is like an organism’s habitat (address) and its occupation combined. 3. Students often mistakenly think that symbiosis is a synonym for mutualism. Mutualism is a form of symbiosis. 4. The expectation that ecosystems are relatively stable is common. Natural disturbances of any sort (fires, earthquakes, floods, or strong storms) are typically viewed as tragic and damaging to ecosystems. Before beginning the topic of ecological disturbances, consider asking your students to briefly respond to news that a state or federal park has a) been burned, b) been struck by high winds and/or lightning, or c) been temporarily flooded. In addition, consider asking what if anything should be done to prevent or repair this damage? Teaching Tips 1. For many students, their interactions with diverse ecosystems have been limited to videos and movies, 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 common experience of the students to which you can refer and relate the content of this chapter. 2. Alternately, you can relate some of the basics of this chapter to a local campus or regional example to which most students are familiar. Perhaps there is a distinct community on your campus: a pond, distinct wooded area, or other part of campus that students would know and could visit with new insight. 3. In human society, a community might be considered about the same as a local population, perhaps all the people living in a town or city. The definition of a biological community is more inclusive, comprising all of the populations of species living close enough together for potential interaction. 4. Examples of interspecific competition are as close as the nearest lawn. Although students may be more likely to think of animal examples, the various grasses and weeds in a lawn reveal different strategies in their competition for sunlight, moisture, and soil. 5. If your class includes students with business interests, they may enjoy the following analogy. To better understand competition, students might think about fast-food restaurants in your region, perhaps those that sell pizzas. Challenge your students to identify strategies employed by these restaurants to compete with each other. As each restaurant makes changes, how do the other restaurants respond? Restaurants changing strategies in response to each other is analogous to coevolution. 6. Students commonly have practice with food webs and food chains. Present a food web (perhaps Figure 20.18) to your class and challenge them to predict the consequences of a decrease or increase in the population of one of the organisms. This activity can help students understand how difficult it is to make precise predictions about these complex systems. 7. Many keystone species have been identified in ecosystems, including sea otters, elephants, freshwater bass, and Pisaster, a sea star noted in Figure 20.21. Challenge your class to explain how the concept of a keystone species relates to the efforts of conservation biologists. Why might some species be more important to conserve? 8. Before and after images of the impact and recovery of an ecosystem from a natural disaster can be as powerful as any explanation of the process. 9. Challenge your students to think through the adaptive advantage of a warning coloration in a toxic animal. Challenge your students to explain: What is gained if the predator dies? How can such systems evolve is the model is killed in the learning experience? 10. Students who are business-oriented might enjoy this analogy. Many corporate leaders might describe the best business deals as those that are mutualistic, fostering a win-win relationship.

Primary consumers are called herbivores, which eat plants. All organisms in trophic levels above the producers are heterotrophs, or consumers. Primary consumers are called herbivores, which eat plants. Above the level of primary consumers are carnivores, which eat the consumers from the level below. Secondary consumers eat primary consumers. Tertiary consumers eat secondary consumers. Quaternary consumers eat tertiary consumers. Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. They can see ecosystems and art, but they do not understand the composition, the significance of the components, and the nature of their interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. 2. The concept of an ecological niche can be confusing. Ecologist Eugene Odum suggested that an ecological niche is like an organism’s habitat (address) and its occupation combined. 3. Students often mistakenly think that symbiosis is a synonym for mutualism. Mutualism is a form of symbiosis. 4. The expectation that ecosystems are relatively stable is common. Natural disturbances of any sort (fires, earthquakes, floods, or strong storms) are typically viewed as tragic and damaging to ecosystems. Before beginning the topic of ecological disturbances, consider asking your students to briefly respond to news that a state or federal park has a) been burned, b) been struck by high winds and/or lightning, or c) been temporarily flooded. In addition, consider asking what if anything should be done to prevent or repair this damage? Teaching Tips 1. For many students, their interactions with diverse ecosystems have been limited to videos and movies, 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 common experience of the students to which you can refer and relate the content of this chapter. 2. Alternately, you can relate some of the basics of this chapter to a local campus or regional example to which most students are familiar. Perhaps there is a distinct community on your campus: a pond, distinct wooded area, or other part of campus that students would know and could visit with new insight. 3. In human society, a community might be considered about the same as a local population, perhaps all the people living in a town or city. The definition of a biological community is more inclusive, comprising all of the populations of species living close enough together for potential interaction. 4. Examples of interspecific competition are as close as the nearest lawn. Although students may be more likely to think of animal examples, the various grasses and weeds in a lawn reveal different strategies in their competition for sunlight, moisture, and soil. 5. If your class includes students with business interests, they may enjoy the following analogy. To better understand competition, students might think about fast-food restaurants in your region, perhaps those that sell pizzas. Challenge your students to identify strategies employed by these restaurants to compete with each other. As each restaurant makes changes, how do the other restaurants respond? Restaurants changing strategies in response to each other is analogous to coevolution. 6. Students commonly have practice with food webs and food chains. Present a food web (perhaps Figure 20.18) to your class and challenge them to predict the consequences of a decrease or increase in the population of one of the organisms. This activity can help students understand how difficult it is to make precise predictions about these complex systems. 7. Many keystone species have been identified in ecosystems, including sea otters, elephants, freshwater bass, and Pisaster, a sea star noted in Figure 20.21. Challenge your class to explain how the concept of a keystone species relates to the efforts of conservation biologists. Why might some species be more important to conserve? 8. Before and after images of the impact and recovery of an ecosystem from a natural disaster can be as powerful as any explanation of the process. 9. Challenge your students to think through the adaptive advantage of a warning coloration in a toxic animal. Challenge your students to explain: What is gained if the predator dies? How can such systems evolve is the model is killed in the learning experience? 10. Students who are business-oriented might enjoy this analogy. Many corporate leaders might describe the best business deals as those that are mutualistic, fostering a win-win relationship.

Figure 20.15-5 Figure 20.15 Examples of food chains (Step 5) Quaternary consumers Carnivore Carnivore Tertiary consumers Carnivore Carnivore Secondary consumers Carnivore Carnivore Figure 20.15 Examples of food chains (Step 5) Primary consumers Herbivore Zooplankton Producers Plant Phytoplankton A terrestrial food chain An aquatic food chain Figure 20.15-5

Detritivores, which are often called scavengers, consume detritus, the dead material left by all trophic levels. Decomposers are prokaryotes and fungi, which secrete enzymes that digest molecules in organic material and convert them into inorganic forms. Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. They can see ecosystems and art, but they do not understand the composition, the significance of the components, and the nature of their interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. 2. The concept of an ecological niche can be confusing. Ecologist Eugene Odum suggested that an ecological niche is like an organism’s habitat (address) and its occupation combined. 3. Students often mistakenly think that symbiosis is a synonym for mutualism. Mutualism is a form of symbiosis. 4. The expectation that ecosystems are relatively stable is common. Natural disturbances of any sort (fires, earthquakes, floods, or strong storms) are typically viewed as tragic and damaging to ecosystems. Before beginning the topic of ecological disturbances, consider asking your students to briefly respond to news that a state or federal park has a) been burned, b) been struck by high winds and/or lightning, or c) been temporarily flooded. In addition, consider asking what if anything should be done to prevent or repair this damage? Teaching Tips 1. For many students, their interactions with diverse ecosystems have been limited to videos and movies, 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 common experience of the students to which you can refer and relate the content of this chapter. 2. Alternately, you can relate some of the basics of this chapter to a local campus or regional example to which most students are familiar. Perhaps there is a distinct community on your campus: a pond, distinct wooded area, or other part of campus that students would know and could visit with new insight. 3. In human society, a community might be considered about the same as a local population, perhaps all the people living in a town or city. The definition of a biological community is more inclusive, comprising all of the populations of species living close enough together for potential interaction. 4. Examples of interspecific competition are as close as the nearest lawn. Although students may be more likely to think of animal examples, the various grasses and weeds in a lawn reveal different strategies in their competition for sunlight, moisture, and soil. 5. If your class includes students with business interests, they may enjoy the following analogy. To better understand competition, students might think about fast-food restaurants in your region, perhaps those that sell pizzas. Challenge your students to identify strategies employed by these restaurants to compete with each other. As each restaurant makes changes, how do the other restaurants respond? Restaurants changing strategies in response to each other is analogous to coevolution. 6. Students commonly have practice with food webs and food chains. Present a food web (perhaps Figure 20.18) to your class and challenge them to predict the consequences of a decrease or increase in the population of one of the organisms. This activity can help students understand how difficult it is to make precise predictions about these complex systems. 7. Many keystone species have been identified in ecosystems, including sea otters, elephants, freshwater bass, and Pisaster, a sea star noted in Figure 20.21. Challenge your class to explain how the concept of a keystone species relates to the efforts of conservation biologists. Why might some species be more important to conserve? 8. Before and after images of the impact and recovery of an ecosystem from a natural disaster can be as powerful as any explanation of the process. 9. Challenge your students to think through the adaptive advantage of a warning coloration in a toxic animal. Challenge your students to explain: What is gained if the predator dies? How can such systems evolve is the model is killed in the learning experience? 10. Students who are business-oriented might enjoy this analogy. Many corporate leaders might describe the best business deals as those that are mutualistic, fostering a win-win relationship.

Figure 20.16 Fungi decomposing a dead log

Biological Magnification Environmental toxins accumulate in consumers at higher concentrations up a trophic system in a process called biological magnification. Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. They can see ecosystems and art, but they do not understand the composition, the significance of the components, and the nature of their interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. 2. The concept of an ecological niche can be confusing. Ecologist Eugene Odum suggested that an ecological niche is like an organism’s habitat (address) and its occupation combined. 3. Students often mistakenly think that symbiosis is a synonym for mutualism. Mutualism is a form of symbiosis. 4. The expectation that ecosystems are relatively stable is common. Natural disturbances of any sort (fires, earthquakes, floods, or strong storms) are typically viewed as tragic and damaging to ecosystems. Before beginning the topic of ecological disturbances, consider asking your students to briefly respond to news that a state or federal park has a) been burned, b) been struck by high winds and/or lightning, or c) been temporarily flooded. In addition, consider asking what if anything should be done to prevent or repair this damage? Teaching Tips 1. For many students, their interactions with diverse ecosystems have been limited to videos and movies, 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 common experience of the students to which you can refer and relate the content of this chapter. 2. Alternately, you can relate some of the basics of this chapter to a local campus or regional example to which most students are familiar. Perhaps there is a distinct community on your campus: a pond, distinct wooded area, or other part of campus that students would know and could visit with new insight. 3. In human society, a community might be considered about the same as a local population, perhaps all the people living in a town or city. The definition of a biological community is more inclusive, comprising all of the populations of species living close enough together for potential interaction. 4. Examples of interspecific competition are as close as the nearest lawn. Although students may be more likely to think of animal examples, the various grasses and weeds in a lawn reveal different strategies in their competition for sunlight, moisture, and soil. 5. If your class includes students with business interests, they may enjoy the following analogy. To better understand competition, students might think about fast-food restaurants in your region, perhaps those that sell pizzas. Challenge your students to identify strategies employed by these restaurants to compete with each other. As each restaurant makes changes, how do the other restaurants respond? Restaurants changing strategies in response to each other is analogous to coevolution. 6. Students commonly have practice with food webs and food chains. Present a food web (perhaps Figure 20.18) to your class and challenge them to predict the consequences of a decrease or increase in the population of one of the organisms. This activity can help students understand how difficult it is to make precise predictions about these complex systems. 7. Many keystone species have been identified in ecosystems, including sea otters, elephants, freshwater bass, and Pisaster, a sea star noted in Figure 20.21. Challenge your class to explain how the concept of a keystone species relates to the efforts of conservation biologists. Why might some species be more important to conserve? 8. Before and after images of the impact and recovery of an ecosystem from a natural disaster can be as powerful as any explanation of the process. 9. Challenge your students to think through the adaptive advantage of a warning coloration in a toxic animal. Challenge your students to explain: What is gained if the predator dies? How can such systems evolve is the model is killed in the learning experience? 10. Students who are business-oriented might enjoy this analogy. Many corporate leaders might describe the best business deals as those that are mutualistic, fostering a win-win relationship.

Figure 20.17 Herring gull eggs 124 ppm Lake trout 4.83 ppm Increasing concentrations of PCBs Smelt 1.04 ppm Figure 20.17 Biological magnification of PCBs in a Great Lakes food chain in the early 1960s Zooplankton 0.123 ppm Phytoplankton 0.025 ppm Figure 20.17

Food Webs Few ecosystems are as simple as an unbranched food chain. Omnivores Eat producers and consumers Form woven ecosystems called food webs Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. They can see ecosystems and art, but they do not understand the composition, the significance of the components, and the nature of their interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. 2. The concept of an ecological niche can be confusing. Ecologist Eugene Odum suggested that an ecological niche is like an organism’s habitat (address) and its occupation combined. 3. Students often mistakenly think that symbiosis is a synonym for mutualism. Mutualism is a form of symbiosis. 4. The expectation that ecosystems are relatively stable is common. Natural disturbances of any sort (fires, earthquakes, floods, or strong storms) are typically viewed as tragic and damaging to ecosystems. Before beginning the topic of ecological disturbances, consider asking your students to briefly respond to news that a state or federal park has a) been burned, b) been struck by high winds and/or lightning, or c) been temporarily flooded. In addition, consider asking what if anything should be done to prevent or repair this damage? Teaching Tips 1. For many students, their interactions with diverse ecosystems have been limited to videos and movies, 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 common experience of the students to which you can refer and relate the content of this chapter. 2. Alternately, you can relate some of the basics of this chapter to a local campus or regional example to which most students are familiar. Perhaps there is a distinct community on your campus: a pond, distinct wooded area, or other part of campus that students would know and could visit with new insight. 3. In human society, a community might be considered about the same as a local population, perhaps all the people living in a town or city. The definition of a biological community is more inclusive, comprising all of the populations of species living close enough together for potential interaction. 4. Examples of interspecific competition are as close as the nearest lawn. Although students may be more likely to think of animal examples, the various grasses and weeds in a lawn reveal different strategies in their competition for sunlight, moisture, and soil. 5. If your class includes students with business interests, they may enjoy the following analogy. To better understand competition, students might think about fast-food restaurants in your region, perhaps those that sell pizzas. Challenge your students to identify strategies employed by these restaurants to compete with each other. As each restaurant makes changes, how do the other restaurants respond? Restaurants changing strategies in response to each other is analogous to coevolution. 6. Students commonly have practice with food webs and food chains. Present a food web (perhaps Figure 20.18) to your class and challenge them to predict the consequences of a decrease or increase in the population of one of the organisms. This activity can help students understand how difficult it is to make precise predictions about these complex systems. 7. Many keystone species have been identified in ecosystems, including sea otters, elephants, freshwater bass, and Pisaster, a sea star noted in Figure 20.21. Challenge your class to explain how the concept of a keystone species relates to the efforts of conservation biologists. Why might some species be more important to conserve? 8. Before and after images of the impact and recovery of an ecosystem from a natural disaster can be as powerful as any explanation of the process. 9. Challenge your students to think through the adaptive advantage of a warning coloration in a toxic animal. Challenge your students to explain: What is gained if the predator dies? How can such systems evolve is the model is killed in the learning experience? 10. Students who are business-oriented might enjoy this analogy. Many corporate leaders might describe the best business deals as those that are mutualistic, fostering a win-win relationship.

Quaternary, tertiary, and secondary consumers Tertiary and secondary consumers Secondary and primary consumers Primary consumers Figure 20.18 A simplified food web for a Sonoran desert community Producers (plants) Figure 20.18

Species Diversity in Communities Species diversity of a community consists of Species richness, the number of different species in the community Relative abundance of the different species, the proportional representation of a species in a community Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. They can see ecosystems and art, but they do not understand the composition, the significance of the components, and the nature of their interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. 2. The concept of an ecological niche can be confusing. Ecologist Eugene Odum suggested that an ecological niche is like an organism’s habitat (address) and its occupation combined. 3. Students often mistakenly think that symbiosis is a synonym for mutualism. Mutualism is a form of symbiosis. 4. The expectation that ecosystems are relatively stable is common. Natural disturbances of any sort (fires, earthquakes, floods, or strong storms) are typically viewed as tragic and damaging to ecosystems. Before beginning the topic of ecological disturbances, consider asking your students to briefly respond to news that a state or federal park has a) been burned, b) been struck by high winds and/or lightning, or c) been temporarily flooded. In addition, consider asking what if anything should be done to prevent or repair this damage? Teaching Tips 1. For many students, their interactions with diverse ecosystems have been limited to videos and movies, 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 common experience of the students to which you can refer and relate the content of this chapter. 2. Alternately, you can relate some of the basics of this chapter to a local campus or regional example to which most students are familiar. Perhaps there is a distinct community on your campus: a pond, distinct wooded area, or other part of campus that students would know and could visit with new insight. 3. In human society, a community might be considered about the same as a local population, perhaps all the people living in a town or city. The definition of a biological community is more inclusive, comprising all of the populations of species living close enough together for potential interaction. 4. Examples of interspecific competition are as close as the nearest lawn. Although students may be more likely to think of animal examples, the various grasses and weeds in a lawn reveal different strategies in their competition for sunlight, moisture, and soil. 5. If your class includes students with business interests, they may enjoy the following analogy. To better understand competition, students might think about fast-food restaurants in your region, perhaps those that sell pizzas. Challenge your students to identify strategies employed by these restaurants to compete with each other. As each restaurant makes changes, how do the other restaurants respond? Restaurants changing strategies in response to each other is analogous to coevolution. 6. Students commonly have practice with food webs and food chains. Present a food web (perhaps Figure 20.18) to your class and challenge them to predict the consequences of a decrease or increase in the population of one of the organisms. This activity can help students understand how difficult it is to make precise predictions about these complex systems. 7. Many keystone species have been identified in ecosystems, including sea otters, elephants, freshwater bass, and Pisaster, a sea star noted in Figure 20.21. Challenge your class to explain how the concept of a keystone species relates to the efforts of conservation biologists. Why might some species be more important to conserve? 8. Before and after images of the impact and recovery of an ecosystem from a natural disaster can be as powerful as any explanation of the process. 9. Challenge your students to think through the adaptive advantage of a warning coloration in a toxic animal. Challenge your students to explain: What is gained if the predator dies? How can such systems evolve is the model is killed in the learning experience? 10. Students who are business-oriented might enjoy this analogy. Many corporate leaders might describe the best business deals as those that are mutualistic, fostering a win-win relationship.

Woodland A Woodland B Figure 20.19 Figure 20.19 Which woodland is more diverse? Woodland B Figure 20.19

Relative abundance of tree species (%) 80 Key Woodland A 60 Woodland B 40 Relative abundance of tree species (%) 20 Figure 20.20 Relative abundance of tree species in woodlands A and B Tree species Figure 20.20

A keystone species is a species whose impact on its community is much larger than its total mass or abundance indicates. Experiments in the 1960s demonstrated that a sea star functioned as a keystone species in intertidal zones of the Washington coast. Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. They can see ecosystems and art, but they do not understand the composition, the significance of the components, and the nature of their interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. 2. The concept of an ecological niche can be confusing. Ecologist Eugene Odum suggested that an ecological niche is like an organism’s habitat (address) and its occupation combined. 3. Students often mistakenly think that symbiosis is a synonym for mutualism. Mutualism is a form of symbiosis. 4. The expectation that ecosystems are relatively stable is common. Natural disturbances of any sort (fires, earthquakes, floods, or strong storms) are typically viewed as tragic and damaging to ecosystems. Before beginning the topic of ecological disturbances, consider asking your students to briefly respond to news that a state or federal park has a) been burned, b) been struck by high winds and/or lightning, or c) been temporarily flooded. In addition, consider asking what if anything should be done to prevent or repair this damage? Teaching Tips 1. For many students, their interactions with diverse ecosystems have been limited to videos and movies, 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 common experience of the students to which you can refer and relate the content of this chapter. 2. Alternately, you can relate some of the basics of this chapter to a local campus or regional example to which most students are familiar. Perhaps there is a distinct community on your campus: a pond, distinct wooded area, or other part of campus that students would know and could visit with new insight. 3. In human society, a community might be considered about the same as a local population, perhaps all the people living in a town or city. The definition of a biological community is more inclusive, comprising all of the populations of species living close enough together for potential interaction. 4. Examples of interspecific competition are as close as the nearest lawn. Although students may be more likely to think of animal examples, the various grasses and weeds in a lawn reveal different strategies in their competition for sunlight, moisture, and soil. 5. If your class includes students with business interests, they may enjoy the following analogy. To better understand competition, students might think about fast-food restaurants in your region, perhaps those that sell pizzas. Challenge your students to identify strategies employed by these restaurants to compete with each other. As each restaurant makes changes, how do the other restaurants respond? Restaurants changing strategies in response to each other is analogous to coevolution. 6. Students commonly have practice with food webs and food chains. Present a food web (perhaps Figure 20.18) to your class and challenge them to predict the consequences of a decrease or increase in the population of one of the organisms. This activity can help students understand how difficult it is to make precise predictions about these complex systems. 7. Many keystone species have been identified in ecosystems, including sea otters, elephants, freshwater bass, and Pisaster, a sea star noted in Figure 20.21. Challenge your class to explain how the concept of a keystone species relates to the efforts of conservation biologists. Why might some species be more important to conserve? 8. Before and after images of the impact and recovery of an ecosystem from a natural disaster can be as powerful as any explanation of the process. 9. Challenge your students to think through the adaptive advantage of a warning coloration in a toxic animal. Challenge your students to explain: What is gained if the predator dies? How can such systems evolve is the model is killed in the learning experience? 10. Students who are business-oriented might enjoy this analogy. Many corporate leaders might describe the best business deals as those that are mutualistic, fostering a win-win relationship.

Figure 20.21 A Pisaster sea star eating its favorite food, a mussel

Disturbances in Communities Disturbances are episodes that damage biological communities, at least temporarily, by Destroying organisms Altering the availability of resources such as mineral nutrients and water. Examples of disturbances are storms, fires, floods, and droughts Disturbances may cause The emergence of a previously unknown disease Opportunities for other organisms to grow Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. They can see ecosystems and art, but they do not understand the composition, the significance of the components, and the nature of their interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. 2. The concept of an ecological niche can be confusing. Ecologist Eugene Odum suggested that an ecological niche is like an organism’s habitat (address) and its occupation combined. 3. Students often mistakenly think that symbiosis is a synonym for mutualism. Mutualism is a form of symbiosis. 4. The expectation that ecosystems are relatively stable is common. Natural disturbances of any sort (fires, earthquakes, floods, or strong storms) are typically viewed as tragic and damaging to ecosystems. Before beginning the topic of ecological disturbances, consider asking your students to briefly respond to news that a state or federal park has a) been burned, b) been struck by high winds and/or lightning, or c) been temporarily flooded. In addition, consider asking what if anything should be done to prevent or repair this damage? Teaching Tips 1. For many students, their interactions with diverse ecosystems have been limited to videos and movies, 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 common experience of the students to which you can refer and relate the content of this chapter. 2. Alternately, you can relate some of the basics of this chapter to a local campus or regional example to which most students are familiar. Perhaps there is a distinct community on your campus: a pond, distinct wooded area, or other part of campus that students would know and could visit with new insight. 3. In human society, a community might be considered about the same as a local population, perhaps all the people living in a town or city. The definition of a biological community is more inclusive, comprising all of the populations of species living close enough together for potential interaction. 4. Examples of interspecific competition are as close as the nearest lawn. Although students may be more likely to think of animal examples, the various grasses and weeds in a lawn reveal different strategies in their competition for sunlight, moisture, and soil. 5. If your class includes students with business interests, they may enjoy the following analogy. To better understand competition, students might think about fast-food restaurants in your region, perhaps those that sell pizzas. Challenge your students to identify strategies employed by these restaurants to compete with each other. As each restaurant makes changes, how do the other restaurants respond? Restaurants changing strategies in response to each other is analogous to coevolution. 6. Students commonly have practice with food webs and food chains. Present a food web (perhaps Figure 20.18) to your class and challenge them to predict the consequences of a decrease or increase in the population of one of the organisms. This activity can help students understand how difficult it is to make precise predictions about these complex systems. 7. Many keystone species have been identified in ecosystems, including sea otters, elephants, freshwater bass, and Pisaster, a sea star noted in Figure 20.21. Challenge your class to explain how the concept of a keystone species relates to the efforts of conservation biologists. Why might some species be more important to conserve? 8. Before and after images of the impact and recovery of an ecosystem from a natural disaster can be as powerful as any explanation of the process. 9. Challenge your students to think through the adaptive advantage of a warning coloration in a toxic animal. Challenge your students to explain: What is gained if the predator dies? How can such systems evolve is the model is killed in the learning experience? 10. Students who are business-oriented might enjoy this analogy. Many corporate leaders might describe the best business deals as those that are mutualistic, fostering a win-win relationship.

Figure 20.22 A small-scale disturbance

Remember an ecosystem is all biotic and abiotic factors in an area. A simple terrarium is a microcosm that exhibits the two major processes that sustain all ecosystems: Energy flow, the passage of energy through the components of the ecosystem Chemical cycling, the use and reuse of chemical elements such as carbon and nitrogen within the ecosystem Student Misconceptions and Concerns 1. Without an understanding of the inefficiency of aerobic metabolism and basic physics, students might not understand how chemical energy in food is lost as heat. Consider expanding upon these explanations in the book. 2. The environmental impact of eating farm animals is little appreciated by most students. This chapter section helps explain the basis for the increased environmental costs associated with a high meat diet. 3. Except for prior classes in science, students are unlikely to have understood biogeochemical cycles. Although some transfers between the biotic and abiotic components may be known, such as the benefits of fertilizing plants, the broader concept of the biosphere as a self-cycling system is not appreciated by most students. Pretesting your students over their knowledge can confirm this expectation or reveal levels of understanding not appreciated. Consider asking your students to explain how carbon, nitrogen, and water cycle through the biosphere. For each substance, create a complete cycle. Teaching Tips 1. Why do food chains and webs typically have only three to five levels? This question is not often considered by students but is addressed directly in this chapter section. This question makes a good discussion before lecturing on the topic of food chains and food webs. 2. The heat generated as a by-product of metabolism is quite evident during strenuous exercise. It is much like the heat produced by a running automobile engine. In both circumstances, heat is a by-product of the fuel burning process. 3. Energy flow through an ecosystem is analogous to the flow of fuel through a car or electricity through a vacuum cleaner. The 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 NASA systems. 4. Some students might be interested in eating more proteins and fewer carbohydrates because of some special sort of diet (or fad). Does such a high protein diet require the consumption of more meat? The many sources of plant proteins might be surprising to students. The following Vegetarian Society website describes some of the high protein vegetarian options: www.vegsoc.org/info/protein.html#diet. 5. As you discuss the importance of the biogeochemical cycles, you might consider explaining the basic label information provided on a container of plant fertilizer. Typically, plant fertilizers contain various forms of nitrogen and phosphorus, essential chemicals to growth. 6. Challenge students to explain why the areas of greatest primary production are near the equator. Primary production is a consequence of photosynthesis. Regions near the equator receive the highest levels of solar input. 7. A discussion of the movements of water through your local community might help students better relate to the concepts of biogeochemical cycling at a local level. Students could be asked to consider all of the possible inputs of water into your community and the possible routes of exit. 8. The nitrogen-fixing bacteria living in the roots of soybeans add nitrogen to the soil. Corn does not enjoy this same relationship. By rotating corn and soybean crops, corn crops can use some of the nitrogen fixed by the soybean crop in the previous year. Corn and soybean crop rotation has other benefits. Corn is a monocot and soybeans are dicots. Few pests attack corn and soybeans. Thus, crop rotation also helps to control the pest populations characteristic of each type of plant.

Figure 20.25 Ch e m i c al cy cl in g Energy flow Light energy Heat energy Figure 20.25 A terrarium ecosystem Chemical elements Bacteria, protists, and fungi Figure 20.25

Energy flows through ecosystems. Chemicals are recycled within and between ecosystems. All organisms require energy for Growth Maintenance Reproduction In many species, locomotion Each day, the Earth receives about 1019 kcal of solar energy, the energy equivalent of about 100 million atomic bombs. About 1% is converted to chemical energy by photosynthesis. Student Misconceptions and Concerns 1. Without an understanding of the inefficiency of aerobic metabolism and basic physics, students might not understand how chemical energy in food is lost as heat. Consider expanding upon these explanations in the book. 2. The environmental impact of eating farm animals is little appreciated by most students. This chapter section helps explain the basis for the increased environmental costs associated with a high meat diet. 3. Except for prior classes in science, students are unlikely to have understood biogeochemical cycles. Although some transfers between the biotic and abiotic components may be known, such as the benefits of fertilizing plants, the broader concept of the biosphere as a self-cycling system is not appreciated by most students. Pretesting your students over their knowledge can confirm this expectation or reveal levels of understanding not appreciated. Consider asking your students to explain how carbon, nitrogen, and water cycle through the biosphere. For each substance, create a complete cycle. Teaching Tips 1. Why do food chains and webs typically have only three to five levels? This question is not often considered by students but is addressed directly in this chapter section. This question makes a good discussion before lecturing on the topic of food chains and food webs. 2. The heat generated as a by-product of metabolism is quite evident during strenuous exercise. It is much like the heat produced by a running automobile engine. In both circumstances, heat is a by-product of the fuel burning process. 3. Energy flow through an ecosystem is analogous to the flow of fuel through a car or electricity through a vacuum cleaner. The 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 NASA systems. 4. Some students might be interested in eating more proteins and fewer carbohydrates because of some special sort of diet (or fad). Does such a high protein diet require the consumption of more meat? The many sources of plant proteins might be surprising to students. The following Vegetarian Society website describes some of the high protein vegetarian options: www.vegsoc.org/info/protein.html#diet. 5. As you discuss the importance of the biogeochemical cycles, you might consider explaining the basic label information provided on a container of plant fertilizer. Typically, plant fertilizers contain various forms of nitrogen and phosphorus, essential chemicals to growth. 6. Challenge students to explain why the areas of greatest primary production are near the equator. Primary production is a consequence of photosynthesis. Regions near the equator receive the highest levels of solar input. 7. A discussion of the movements of water through your local community might help students better relate to the concepts of biogeochemical cycling at a local level. Students could be asked to consider all of the possible inputs of water into your community and the possible routes of exit. 8. The nitrogen-fixing bacteria living in the roots of soybeans add nitrogen to the soil. Corn does not enjoy this same relationship. By rotating corn and soybean crops, corn crops can use some of the nitrogen fixed by the soybean crop in the previous year. Corn and soybean crop rotation has other benefits. Corn is a monocot and soybeans are dicots. Few pests attack corn and soybeans. Thus, crop rotation also helps to control the pest populations characteristic of each type of plant.

Algal beds and coral reefs Open ocean Estuary Algal beds and coral reefs Desert and semidesert scrub Tundra Temperate grassland Cultivated land Northern coniferous forest (taiga) Savanna Figure 20.26 Primary production of different ecosystems Temperate broadleaf forest Tropical rain forest 500 1,000 1,500 2,000 2,500 Average primary productivity (g/m2/yr) Figure 20.26

Ecological Pyramids When energy flows as organic matter through the trophic levels of an ecosystem, much of it is lost at each link in the food chain. Consider the example of a caterpillar. Student Misconceptions and Concerns 1. Without an understanding of the inefficiency of aerobic metabolism and basic physics, students might not understand how chemical energy in food is lost as heat. Consider expanding upon these explanations in the book. 2. The environmental impact of eating farm animals is little appreciated by most students. This chapter section helps explain the basis for the increased environmental costs associated with a high meat diet. 3. Except for prior classes in science, students are unlikely to have understood biogeochemical cycles. Although some transfers between the biotic and abiotic components may be known, such as the benefits of fertilizing plants, the broader concept of the biosphere as a self-cycling system is not appreciated by most students. Pretesting your students over their knowledge can confirm this expectation or reveal levels of understanding not appreciated. Consider asking your students to explain how carbon, nitrogen, and water cycle through the biosphere. For each substance, create a complete cycle. Teaching Tips 1. Why do food chains and webs typically have only three to five levels? This question is not often considered by students but is addressed directly in this chapter section. This question makes a good discussion before lecturing on the topic of food chains and food webs. 2. The heat generated as a by-product of metabolism is quite evident during strenuous exercise. It is much like the heat produced by a running automobile engine. In both circumstances, heat is a by-product of the fuel burning process. 3. Energy flow through an ecosystem is analogous to the flow of fuel through a car or electricity through a vacuum cleaner. The 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 NASA systems. 4. Some students might be interested in eating more proteins and fewer carbohydrates because of some special sort of diet (or fad). Does such a high protein diet require the consumption of more meat? The many sources of plant proteins might be surprising to students. The following Vegetarian Society website describes some of the high protein vegetarian options: www.vegsoc.org/info/protein.html#diet. 5. As you discuss the importance of the biogeochemical cycles, you might consider explaining the basic label information provided on a container of plant fertilizer. Typically, plant fertilizers contain various forms of nitrogen and phosphorus, essential chemicals to growth. 6. Challenge students to explain why the areas of greatest primary production are near the equator. Primary production is a consequence of photosynthesis. Regions near the equator receive the highest levels of solar input. 7. A discussion of the movements of water through your local community might help students better relate to the concepts of biogeochemical cycling at a local level. Students could be asked to consider all of the possible inputs of water into your community and the possible routes of exit. 8. The nitrogen-fixing bacteria living in the roots of soybeans add nitrogen to the soil. Corn does not enjoy this same relationship. By rotating corn and soybean crops, corn crops can use some of the nitrogen fixed by the soybean crop in the previous year. Corn and soybean crop rotation has other benefits. Corn is a monocot and soybeans are dicots. Few pests attack corn and soybeans. Thus, crop rotation also helps to control the pest populations characteristic of each type of plant.

Plant material eaten by caterpillar 100 kilocalories (kcal) Figure 20.27 What becomes of a caterpillar's food? 35 kcal Cellular respiration 50 kcal Feces 15 kcal Growth Figure 20.27

The energy level available to the next higher level A pyramid of production illustrates the cumulative loss of energy with each transfer in a food chain. The energy level available to the next higher level Ranges from 5–20% Is illustrated here as 10% Student Misconceptions and Concerns 1. Without an understanding of the inefficiency of aerobic metabolism and basic physics, students might not understand how chemical energy in food is lost as heat. Consider expanding upon these explanations in the book. 2. The environmental impact of eating farm animals is little appreciated by most students. This chapter section helps explain the basis for the increased environmental costs associated with a high meat diet. 3. Except for prior classes in science, students are unlikely to have understood biogeochemical cycles. Although some transfers between the biotic and abiotic components may be known, such as the benefits of fertilizing plants, the broader concept of the biosphere as a self-cycling system is not appreciated by most students. Pretesting your students over their knowledge can confirm this expectation or reveal levels of understanding not appreciated. Consider asking your students to explain how carbon, nitrogen, and water cycle through the biosphere. For each substance, create a complete cycle. Teaching Tips 1. Why do food chains and webs typically have only three to five levels? This question is not often considered by students but is addressed directly in this chapter section. This question makes a good discussion before lecturing on the topic of food chains and food webs. 2. The heat generated as a by-product of metabolism is quite evident during strenuous exercise. It is much like the heat produced by a running automobile engine. In both circumstances, heat is a by-product of the fuel burning process. 3. Energy flow through an ecosystem is analogous to the flow of fuel through a car or electricity through a vacuum cleaner. The 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 NASA systems. 4. Some students might be interested in eating more proteins and fewer carbohydrates because of some special sort of diet (or fad). Does such a high protein diet require the consumption of more meat? The many sources of plant proteins might be surprising to students. The following Vegetarian Society website describes some of the high protein vegetarian options: www.vegsoc.org/info/protein.html#diet. 5. As you discuss the importance of the biogeochemical cycles, you might consider explaining the basic label information provided on a container of plant fertilizer. Typically, plant fertilizers contain various forms of nitrogen and phosphorus, essential chemicals to growth. 6. Challenge students to explain why the areas of greatest primary production are near the equator. Primary production is a consequence of photosynthesis. Regions near the equator receive the highest levels of solar input. 7. A discussion of the movements of water through your local community might help students better relate to the concepts of biogeochemical cycling at a local level. Students could be asked to consider all of the possible inputs of water into your community and the possible routes of exit. 8. The nitrogen-fixing bacteria living in the roots of soybeans add nitrogen to the soil. Corn does not enjoy this same relationship. By rotating corn and soybean crops, corn crops can use some of the nitrogen fixed by the soybean crop in the previous year. Corn and soybean crop rotation has other benefits. Corn is a monocot and soybeans are dicots. Few pests attack corn and soybeans. Thus, crop rotation also helps to control the pest populations characteristic of each type of plant.

Tertiary consumers Secondary consumers Primary consumers Producers 10 kcal Secondary consumers 100 kcal Primary consumers 1,000 kcal Figure 20.28 An idealized pyramid of production Producers 10,000 kcal 1,000,000 kcal of sunlight Figure 20.28

The energy available to top-level consumers is small compared to the energy available to lower-level consumers. This explains why Top-level consumers require more geographic area Most food chains are limited to three to five levels The dynamics of energy flow apply to the human population, when humans eat Plants, we are primary consumers Beef or other meat from herbivores, we are secondary consumers Fish like trout or salmon, we are tertiary consumers Student Misconceptions and Concerns 1. Without an understanding of the inefficiency of aerobic metabolism and basic physics, students might not understand how chemical energy in food is lost as heat. Consider expanding upon these explanations in the book. 2. The environmental impact of eating farm animals is little appreciated by most students. This chapter section helps explain the basis for the increased environmental costs associated with a high meat diet. 3. Except for prior classes in science, students are unlikely to have understood biogeochemical cycles. Although some transfers between the biotic and abiotic components may be known, such as the benefits of fertilizing plants, the broader concept of the biosphere as a self-cycling system is not appreciated by most students. Pretesting your students over their knowledge can confirm this expectation or reveal levels of understanding not appreciated. Consider asking your students to explain how carbon, nitrogen, and water cycle through the biosphere. For each substance, create a complete cycle. Teaching Tips 1. Why do food chains and webs typically have only three to five levels? This question is not often considered by students but is addressed directly in this chapter section. This question makes a good discussion before lecturing on the topic of food chains and food webs. 2. The heat generated as a by-product of metabolism is quite evident during strenuous exercise. It is much like the heat produced by a running automobile engine. In both circumstances, heat is a by-product of the fuel burning process. 3. Energy flow through an ecosystem is analogous to the flow of fuel through a car or electricity through a vacuum cleaner. The 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 NASA systems. 4. Some students might be interested in eating more proteins and fewer carbohydrates because of some special sort of diet (or fad). Does such a high protein diet require the consumption of more meat? The many sources of plant proteins might be surprising to students. The following Vegetarian Society website describes some of the high protein vegetarian options: www.vegsoc.org/info/protein.html#diet. 5. As you discuss the importance of the biogeochemical cycles, you might consider explaining the basic label information provided on a container of plant fertilizer. Typically, plant fertilizers contain various forms of nitrogen and phosphorus, essential chemicals to growth. 6. Challenge students to explain why the areas of greatest primary production are near the equator. Primary production is a consequence of photosynthesis. Regions near the equator receive the highest levels of solar input. 7. A discussion of the movements of water through your local community might help students better relate to the concepts of biogeochemical cycling at a local level. Students could be asked to consider all of the possible inputs of water into your community and the possible routes of exit. 8. The nitrogen-fixing bacteria living in the roots of soybeans add nitrogen to the soil. Corn does not enjoy this same relationship. By rotating corn and soybean crops, corn crops can use some of the nitrogen fixed by the soybean crop in the previous year. Corn and soybean crop rotation has other benefits. Corn is a monocot and soybeans are dicots. Few pests attack corn and soybeans. Thus, crop rotation also helps to control the pest populations characteristic of each type of plant.

Eating meat of any kind is expensive economically and environmentally. The two energy pyramids that follow compare the amount of food available to humans if we are strictly either: Vegetarians or Carnivores Eating meat of any kind is expensive economically and environmentally. Student Misconceptions and Concerns 1. Without an understanding of the inefficiency of aerobic metabolism and basic physics, students might not understand how chemical energy in food is lost as heat. Consider expanding upon these explanations in the book. 2. The environmental impact of eating farm animals is little appreciated by most students. This chapter section helps explain the basis for the increased environmental costs associated with a high meat diet. 3. Except for prior classes in science, students are unlikely to have understood biogeochemical cycles. Although some transfers between the biotic and abiotic components may be known, such as the benefits of fertilizing plants, the broader concept of the biosphere as a self-cycling system is not appreciated by most students. Pretesting your students over their knowledge can confirm this expectation or reveal levels of understanding not appreciated. Consider asking your students to explain how carbon, nitrogen, and water cycle through the biosphere. For each substance, create a complete cycle. Teaching Tips 1. Why do food chains and webs typically have only three to five levels? This question is not often considered by students but is addressed directly in this chapter section. This question makes a good discussion before lecturing on the topic of food chains and food webs. 2. The heat generated as a by-product of metabolism is quite evident during strenuous exercise. It is much like the heat produced by a running automobile engine. In both circumstances, heat is a by-product of the fuel burning process. 3. Energy flow through an ecosystem is analogous to the flow of fuel through a car or electricity through a vacuum cleaner. The 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 NASA systems. 4. Some students might be interested in eating more proteins and fewer carbohydrates because of some special sort of diet (or fad). Does such a high protein diet require the consumption of more meat? The many sources of plant proteins might be surprising to students. The following Vegetarian Society website describes some of the high protein vegetarian options: www.vegsoc.org/info/protein.html#diet. 5. As you discuss the importance of the biogeochemical cycles, you might consider explaining the basic label information provided on a container of plant fertilizer. Typically, plant fertilizers contain various forms of nitrogen and phosphorus, essential chemicals to growth. 6. Challenge students to explain why the areas of greatest primary production are near the equator. Primary production is a consequence of photosynthesis. Regions near the equator receive the highest levels of solar input. 7. A discussion of the movements of water through your local community might help students better relate to the concepts of biogeochemical cycling at a local level. Students could be asked to consider all of the possible inputs of water into your community and the possible routes of exit. 8. The nitrogen-fixing bacteria living in the roots of soybeans add nitrogen to the soil. Corn does not enjoy this same relationship. By rotating corn and soybean crops, corn crops can use some of the nitrogen fixed by the soybean crop in the previous year. Corn and soybean crop rotation has other benefits. Corn is a monocot and soybeans are dicots. Few pests attack corn and soybeans. Thus, crop rotation also helps to control the pest populations characteristic of each type of plant.

Figure 20.29 Trophic level Human meat-eaters Secondary consumers Human vegetarians Cattle Primary consumers Producers Corn Corn Figure 20.29 Food energy available to the human population at different trophic levels Figure 20.29

Chemical Cycling in Ecosystems Life depends on the recycling of chemicals. Nutrients are acquired and waste products are released by living organisms. At death, decomposers return the complex molecules of an organism to the environment. The pool of inorganic nutrients is used by plants and other producers to build new organic matter. Student Misconceptions and Concerns 1. Without an understanding of the inefficiency of aerobic metabolism and basic physics, students might not understand how chemical energy in food is lost as heat. Consider expanding upon these explanations in the book. 2. The environmental impact of eating farm animals is little appreciated by most students. This chapter section helps explain the basis for the increased environmental costs associated with a high meat diet. 3. Except for prior classes in science, students are unlikely to have understood biogeochemical cycles. Although some transfers between the biotic and abiotic components may be known, such as the benefits of fertilizing plants, the broader concept of the biosphere as a self-cycling system is not appreciated by most students. Pretesting your students over their knowledge can confirm this expectation or reveal levels of understanding not appreciated. Consider asking your students to explain how carbon, nitrogen, and water cycle through the biosphere. For each substance, create a complete cycle. Teaching Tips 1. Why do food chains and webs typically have only three to five levels? This question is not often considered by students but is addressed directly in this chapter section. This question makes a good discussion before lecturing on the topic of food chains and food webs. 2. The heat generated as a by-product of metabolism is quite evident during strenuous exercise. It is much like the heat produced by a running automobile engine. In both circumstances, heat is a by-product of the fuel burning process. 3. Energy flow through an ecosystem is analogous to the flow of fuel through a car or electricity through a vacuum cleaner. The 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 NASA systems. 4. Some students might be interested in eating more proteins and fewer carbohydrates because of some special sort of diet (or fad). Does such a high protein diet require the consumption of more meat? The many sources of plant proteins might be surprising to students. The following Vegetarian Society website describes some of the high protein vegetarian options: www.vegsoc.org/info/protein.html#diet. 5. As you discuss the importance of the biogeochemical cycles, you might consider explaining the basic label information provided on a container of plant fertilizer. Typically, plant fertilizers contain various forms of nitrogen and phosphorus, essential chemicals to growth. 6. Challenge students to explain why the areas of greatest primary production are near the equator. Primary production is a consequence of photosynthesis. Regions near the equator receive the highest levels of solar input. 7. A discussion of the movements of water through your local community might help students better relate to the concepts of biogeochemical cycling at a local level. Students could be asked to consider all of the possible inputs of water into your community and the possible routes of exit. 8. The nitrogen-fixing bacteria living in the roots of soybeans add nitrogen to the soil. Corn does not enjoy this same relationship. By rotating corn and soybean crops, corn crops can use some of the nitrogen fixed by the soybean crop in the previous year. Corn and soybean crop rotation has other benefits. Corn is a monocot and soybeans are dicots. Few pests attack corn and soybeans. Thus, crop rotation also helps to control the pest populations characteristic of each type of plant.

Figure 20.30 Plant growth on fallen tree

The General Scheme of Chemical Cycling Biogeochemical cycles involve Biotic components Abiotic components from an abiotic reservoir where a chemical accumulates or is stockpiled outside of living organisms Biogeochemical cycles can be local or global Three important biogeochemical cycles are Carbon Phosphorus Nitrogen Student Misconceptions and Concerns 1. Without an understanding of the inefficiency of aerobic metabolism and basic physics, students might not understand how chemical energy in food is lost as heat. Consider expanding upon these explanations in the book. 2. The environmental impact of eating farm animals is little appreciated by most students. This chapter section helps explain the basis for the increased environmental costs associated with a high meat diet. 3. Except for prior classes in science, students are unlikely to have understood biogeochemical cycles. Although some transfers between the biotic and abiotic components may be known, such as the benefits of fertilizing plants, the broader concept of the biosphere as a self-cycling system is not appreciated by most students. Pretesting your students over their knowledge can confirm this expectation or reveal levels of understanding not appreciated. Consider asking your students to explain how carbon, nitrogen, and water cycle through the biosphere. For each substance, create a complete cycle. Teaching Tips 1. Why do food chains and webs typically have only three to five levels? This question is not often considered by students but is addressed directly in this chapter section. This question makes a good discussion before lecturing on the topic of food chains and food webs. 2. The heat generated as a by-product of metabolism is quite evident during strenuous exercise. It is much like the heat produced by a running automobile engine. In both circumstances, heat is a by-product of the fuel burning process. 3. Energy flow through an ecosystem is analogous to the flow of fuel through a car or electricity through a vacuum cleaner. The 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 NASA systems. 4. Some students might be interested in eating more proteins and fewer carbohydrates because of some special sort of diet (or fad). Does such a high protein diet require the consumption of more meat? The many sources of plant proteins might be surprising to students. The following Vegetarian Society website describes some of the high protein vegetarian options: www.vegsoc.org/info/protein.html#diet. 5. As you discuss the importance of the biogeochemical cycles, you might consider explaining the basic label information provided on a container of plant fertilizer. Typically, plant fertilizers contain various forms of nitrogen and phosphorus, essential chemicals to growth. 6. Challenge students to explain why the areas of greatest primary production are near the equator. Primary production is a consequence of photosynthesis. Regions near the equator receive the highest levels of solar input. 7. A discussion of the movements of water through your local community might help students better relate to the concepts of biogeochemical cycling at a local level. Students could be asked to consider all of the possible inputs of water into your community and the possible routes of exit. 8. The nitrogen-fixing bacteria living in the roots of soybeans add nitrogen to the soil. Corn does not enjoy this same relationship. By rotating corn and soybean crops, corn crops can use some of the nitrogen fixed by the soybean crop in the previous year. Corn and soybean crop rotation has other benefits. Corn is a monocot and soybeans are dicots. Few pests attack corn and soybeans. Thus, crop rotation also helps to control the pest populations characteristic of each type of plant.

The Carbon Cycle The cycling of carbon between the biotic and abiotic worlds is accomplished mainly by the reciprocal metabolic processes of Photosynthesis Cellular respiration Student Misconceptions and Concerns 1. Without an understanding of the inefficiency of aerobic metabolism and basic physics, students might not understand how chemical energy in food is lost as heat. Consider expanding upon these explanations in the book. 2. The environmental impact of eating farm animals is little appreciated by most students. This chapter section helps explain the basis for the increased environmental costs associated with a high meat diet. 3. Except for prior classes in science, students are unlikely to have understood biogeochemical cycles. Although some transfers between the biotic and abiotic components may be known, such as the benefits of fertilizing plants, the broader concept of the biosphere as a self-cycling system is not appreciated by most students. Pretesting your students over their knowledge can confirm this expectation or reveal levels of understanding not appreciated. Consider asking your students to explain how carbon, nitrogen, and water cycle through the biosphere. For each substance, create a complete cycle. Teaching Tips 1. Why do food chains and webs typically have only three to five levels? This question is not often considered by students but is addressed directly in this chapter section. This question makes a good discussion before lecturing on the topic of food chains and food webs. 2. The heat generated as a by-product of metabolism is quite evident during strenuous exercise. It is much like the heat produced by a running automobile engine. In both circumstances, heat is a by-product of the fuel burning process. 3. Energy flow through an ecosystem is analogous to the flow of fuel through a car or electricity through a vacuum cleaner. The 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 NASA systems. 4. Some students might be interested in eating more proteins and fewer carbohydrates because of some special sort of diet (or fad). Does such a high protein diet require the consumption of more meat? The many sources of plant proteins might be surprising to students. The following Vegetarian Society website describes some of the high protein vegetarian options: www.vegsoc.org/info/protein.html#diet. 5. As you discuss the importance of the biogeochemical cycles, you might consider explaining the basic label information provided on a container of plant fertilizer. Typically, plant fertilizers contain various forms of nitrogen and phosphorus, essential chemicals to growth. 6. Challenge students to explain why the areas of greatest primary production are near the equator. Primary production is a consequence of photosynthesis. Regions near the equator receive the highest levels of solar input. 7. A discussion of the movements of water through your local community might help students better relate to the concepts of biogeochemical cycling at a local level. Students could be asked to consider all of the possible inputs of water into your community and the possible routes of exit. 8. The nitrogen-fixing bacteria living in the roots of soybeans add nitrogen to the soil. Corn does not enjoy this same relationship. By rotating corn and soybean crops, corn crops can use some of the nitrogen fixed by the soybean crop in the previous year. Corn and soybean crop rotation has other benefits. Corn is a monocot and soybeans are dicots. Few pests attack corn and soybeans. Thus, crop rotation also helps to control the pest populations characteristic of each type of plant.

Figure 20.32 CO2 in atmosphere Burning Photosynthesis Cellular respiration Higher-level consumers Plants, algae, cyanobacteria Wood and fossil fuels Primary consumers Figure 20.32 The carbon cycle Decomposition Wastes; death Plant litter; death Decomposers (soil microbes) Detritus Figure 20.32

The Phosphorus Cycle Organisms require phosphorus as an ingredient of Nucleic acids Phospholipids ATP Phosphorus is also required as a mineral component of vertebrate bones and teeth. The phosphorus cycle does not have an atmospheric component. Student Misconceptions and Concerns 1. Without an understanding of the inefficiency of aerobic metabolism and basic physics, students might not understand how chemical energy in food is lost as heat. Consider expanding upon these explanations in the book. 2. The environmental impact of eating farm animals is little appreciated by most students. This chapter section helps explain the basis for the increased environmental costs associated with a high meat diet. 3. Except for prior classes in science, students are unlikely to have understood biogeochemical cycles. Although some transfers between the biotic and abiotic components may be known, such as the benefits of fertilizing plants, the broader concept of the biosphere as a self-cycling system is not appreciated by most students. Pretesting your students over their knowledge can confirm this expectation or reveal levels of understanding not appreciated. Consider asking your students to explain how carbon, nitrogen, and water cycle through the biosphere. For each substance, create a complete cycle. Teaching Tips 1. Why do food chains and webs typically have only three to five levels? This question is not often considered by students but is addressed directly in this chapter section. This question makes a good discussion before lecturing on the topic of food chains and food webs. 2. The heat generated as a by-product of metabolism is quite evident during strenuous exercise. It is much like the heat produced by a running automobile engine. In both circumstances, heat is a by-product of the fuel burning process. 3. Energy flow through an ecosystem is analogous to the flow of fuel through a car or electricity through a vacuum cleaner. The 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 NASA systems. 4. Some students might be interested in eating more proteins and fewer carbohydrates because of some special sort of diet (or fad). Does such a high protein diet require the consumption of more meat? The many sources of plant proteins might be surprising to students. The following Vegetarian Society website describes some of the high protein vegetarian options: www.vegsoc.org/info/protein.html#diet. 5. As you discuss the importance of the biogeochemical cycles, you might consider explaining the basic label information provided on a container of plant fertilizer. Typically, plant fertilizers contain various forms of nitrogen and phosphorus, essential chemicals to growth. 6. Challenge students to explain why the areas of greatest primary production are near the equator. Primary production is a consequence of photosynthesis. Regions near the equator receive the highest levels of solar input. 7. A discussion of the movements of water through your local community might help students better relate to the concepts of biogeochemical cycling at a local level. Students could be asked to consider all of the possible inputs of water into your community and the possible routes of exit. 8. The nitrogen-fixing bacteria living in the roots of soybeans add nitrogen to the soil. Corn does not enjoy this same relationship. By rotating corn and soybean crops, corn crops can use some of the nitrogen fixed by the soybean crop in the previous year. Corn and soybean crop rotation has other benefits. Corn is a monocot and soybeans are dicots. Few pests attack corn and soybeans. Thus, crop rotation also helps to control the pest populations characteristic of each type of plant.

Figure 20.33 Uplifting of rock Weathering of rock Phosphates in rock Animals Runoff Plants Assimilation Phosphates in soil (inorganic) Detritus Figure 20.33 The phosphorus cycle Phosphates in solution Solid phosphates Decomposition Rock Decomposers in soil Figure 20.33

The Nitrogen Cycle Nitrogen is Nitrogen has two abiotic reservoirs: An ingredient of proteins and nucleic acids Essential to the structure and functioning of all organisms Nitrogen has two abiotic reservoirs: The atmosphere The soil The process of nitrogen fixation converts gaseous N2 to ammonia and nitrates, which can be used by plants. Most of the nitrogen available in natural ecosystems comes from biological fixation performed by two types of nitrogen-fixing bacteria. Student Misconceptions and Concerns 1. Without an understanding of the inefficiency of aerobic metabolism and basic physics, students might not understand how chemical energy in food is lost as heat. Consider expanding upon these explanations in the book. 2. The environmental impact of eating farm animals is little appreciated by most students. This chapter section helps explain the basis for the increased environmental costs associated with a high meat diet. 3. Except for prior classes in science, students are unlikely to have understood biogeochemical cycles. Although some transfers between the biotic and abiotic components may be known, such as the benefits of fertilizing plants, the broader concept of the biosphere as a self-cycling system is not appreciated by most students. Pretesting your students over their knowledge can confirm this expectation or reveal levels of understanding not appreciated. Consider asking your students to explain how carbon, nitrogen, and water cycle through the biosphere. For each substance, create a complete cycle. Teaching Tips 1. Why do food chains and webs typically have only three to five levels? This question is not often considered by students but is addressed directly in this chapter section. This question makes a good discussion before lecturing on the topic of food chains and food webs. 2. The heat generated as a by-product of metabolism is quite evident during strenuous exercise. It is much like the heat produced by a running automobile engine. In both circumstances, heat is a by-product of the fuel burning process. 3. Energy flow through an ecosystem is analogous to the flow of fuel through a car or electricity through a vacuum cleaner. The 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 NASA systems. 4. Some students might be interested in eating more proteins and fewer carbohydrates because of some special sort of diet (or fad). Does such a high protein diet require the consumption of more meat? The many sources of plant proteins might be surprising to students. The following Vegetarian Society website describes some of the high protein vegetarian options: www.vegsoc.org/info/protein.html#diet. 5. As you discuss the importance of the biogeochemical cycles, you might consider explaining the basic label information provided on a container of plant fertilizer. Typically, plant fertilizers contain various forms of nitrogen and phosphorus, essential chemicals to growth. 6. Challenge students to explain why the areas of greatest primary production are near the equator. Primary production is a consequence of photosynthesis. Regions near the equator receive the highest levels of solar input. 7. A discussion of the movements of water through your local community might help students better relate to the concepts of biogeochemical cycling at a local level. Students could be asked to consider all of the possible inputs of water into your community and the possible routes of exit. 8. The nitrogen-fixing bacteria living in the roots of soybeans add nitrogen to the soil. Corn does not enjoy this same relationship. By rotating corn and soybean crops, corn crops can use some of the nitrogen fixed by the soybean crop in the previous year. Corn and soybean crop rotation has other benefits. Corn is a monocot and soybeans are dicots. Few pests attack corn and soybeans. Thus, crop rotation also helps to control the pest populations characteristic of each type of plant.

Nitrogen (N2) in atmosphere Plant Animal Organic compounds Organic compounds Assimilation by plants Nitrogen fixation Death; wastes Denitrifying bacteria Nitrogen-fixing bacteria in root nodules Nitrates In soil (NO3–) Detritus Figure 20.34 The nitrogen cycle Decomposers Free-living nitrogen-fixing bacteria Nitrifying bacteria Decomposition Nitrogen fixation Ammonium (NH4+) in soil Figure 20.34

Nutrient Pollution The growth of algae and cyanobacteria in aquatic ecosystems is limited by low nutrient levels, especially of phosphorus and nitrogen. Nutrient pollution occurs when human activities add excess amounts of these chemicals to aquatic ecosystems. Student Misconceptions and Concerns 1. Without an understanding of the inefficiency of aerobic metabolism and basic physics, students might not understand how chemical energy in food is lost as heat. Consider expanding upon these explanations in the book. 2. The environmental impact of eating farm animals is little appreciated by most students. This chapter section helps explain the basis for the increased environmental costs associated with a high meat diet. 3. Except for prior classes in science, students are unlikely to have understood biogeochemical cycles. Although some transfers between the biotic and abiotic components may be known, such as the benefits of fertilizing plants, the broader concept of the biosphere as a self-cycling system is not appreciated by most students. Pretesting your students over their knowledge can confirm this expectation or reveal levels of understanding not appreciated. Consider asking your students to explain how carbon, nitrogen, and water cycle through the biosphere. For each substance, create a complete cycle. Teaching Tips 1. Why do food chains and webs typically have only three to five levels? This question is not often considered by students but is addressed directly in this chapter section. This question makes a good discussion before lecturing on the topic of food chains and food webs. 2. The heat generated as a by-product of metabolism is quite evident during strenuous exercise. It is much like the heat produced by a running automobile engine. In both circumstances, heat is a by-product of the fuel burning process. 3. Energy flow through an ecosystem is analogous to the flow of fuel through a car or electricity through a vacuum cleaner. The 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 NASA systems. 4. Some students might be interested in eating more proteins and fewer carbohydrates because of some special sort of diet (or fad). Does such a high protein diet require the consumption of more meat? The many sources of plant proteins might be surprising to students. The following Vegetarian Society website describes some of the high protein vegetarian options: www.vegsoc.org/info/protein.html#diet. 5. As you discuss the importance of the biogeochemical cycles, you might consider explaining the basic label information provided on a container of plant fertilizer. Typically, plant fertilizers contain various forms of nitrogen and phosphorus, essential chemicals to growth. 6. Challenge students to explain why the areas of greatest primary production are near the equator. Primary production is a consequence of photosynthesis. Regions near the equator receive the highest levels of solar input. 7. A discussion of the movements of water through your local community might help students better relate to the concepts of biogeochemical cycling at a local level. Students could be asked to consider all of the possible inputs of water into your community and the possible routes of exit. 8. The nitrogen-fixing bacteria living in the roots of soybeans add nitrogen to the soil. Corn does not enjoy this same relationship. By rotating corn and soybean crops, corn crops can use some of the nitrogen fixed by the soybean crop in the previous year. Corn and soybean crop rotation has other benefits. Corn is a monocot and soybeans are dicots. Few pests attack corn and soybeans. Thus, crop rotation also helps to control the pest populations characteristic of each type of plant.

Figure 20.35 Algal growth resulting from nutrient pollution

Nitrogen runoff from Midwestern farm fields has been linked to an annual summer dead zone in the Gulf of Mexico. Student Misconceptions and Concerns 1. Without an understanding of the inefficiency of aerobic metabolism and basic physics, students might not understand how chemical energy in food is lost as heat. Consider expanding upon these explanations in the book. 2. The environmental impact of eating farm animals is little appreciated by most students. This chapter section helps explain the basis for the increased environmental costs associated with a high meat diet. 3. Except for prior classes in science, students are unlikely to have understood biogeochemical cycles. Although some transfers between the biotic and abiotic components may be known, such as the benefits of fertilizing plants, the broader concept of the biosphere as a self-cycling system is not appreciated by most students. Pretesting your students over their knowledge can confirm this expectation or reveal levels of understanding not appreciated. Consider asking your students to explain how carbon, nitrogen, and water cycle through the biosphere. For each substance, create a complete cycle. Teaching Tips 1. Why do food chains and webs typically have only three to five levels? This question is not often considered by students but is addressed directly in this chapter section. This question makes a good discussion before lecturing on the topic of food chains and food webs. 2. The heat generated as a by-product of metabolism is quite evident during strenuous exercise. It is much like the heat produced by a running automobile engine. In both circumstances, heat is a by-product of the fuel burning process. 3. Energy flow through an ecosystem is analogous to the flow of fuel through a car or electricity through a vacuum cleaner. The 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 NASA systems. 4. Some students might be interested in eating more proteins and fewer carbohydrates because of some special sort of diet (or fad). Does such a high protein diet require the consumption of more meat? The many sources of plant proteins might be surprising to students. The following Vegetarian Society website describes some of the high protein vegetarian options: www.vegsoc.org/info/protein.html#diet. 5. As you discuss the importance of the biogeochemical cycles, you might consider explaining the basic label information provided on a container of plant fertilizer. Typically, plant fertilizers contain various forms of nitrogen and phosphorus, essential chemicals to growth. 6. Challenge students to explain why the areas of greatest primary production are near the equator. Primary production is a consequence of photosynthesis. Regions near the equator receive the highest levels of solar input. 7. A discussion of the movements of water through your local community might help students better relate to the concepts of biogeochemical cycling at a local level. Students could be asked to consider all of the possible inputs of water into your community and the possible routes of exit. 8. The nitrogen-fixing bacteria living in the roots of soybeans add nitrogen to the soil. Corn does not enjoy this same relationship. By rotating corn and soybean crops, corn crops can use some of the nitrogen fixed by the soybean crop in the previous year. Corn and soybean crop rotation has other benefits. Corn is a monocot and soybeans are dicots. Few pests attack corn and soybeans. Thus, crop rotation also helps to control the pest populations characteristic of each type of plant.

Figure 20.36 Mississippi River G u l f o M e x i co Light blue lines represent rivers draining into the Mississippi River (shown in dark blue) Figure 20.36 The Gulf of Mexico dead zone G u l f o M e x i co G u l f o M e x i co Summer Winter Figure 20.36

CONSERVATION AND RESTORATION BIOLOGY Ecologists have discovered many environmental problems caused by human enterprises. Ecological research is the foundation for Finding solutions to these problems Reversing the negative consequences of ecosystem alteration Student Misconceptions and Concerns 1. Although likely sympathetic to the conservation of species, students often do not understand the complexity of the issues. This final chapter section helps to describe some of the recent efforts and challenges of sustainable development. A class discussion about the challenges of conservation might help students realize that there are no simple solutions. Teaching Tips 1. In some ways, highways are types of movement corridors between populations of people living in cities. 2. Sometimes students would like to learn more about conservation but are not aware of professional organizations that study these issues. The Society for Conservation Biology has a web address of: http://www.conbio.org/. 3. If a short field trip is possible, you might wish to take students into a wooded area to generally compare the diversity of life at the edge and deep within the woods. Even the edge of some campus ecosystems might be worthwhile. 4. Consider having your students update the progress of the Kissimmee River Restoration Project.

Biodiversity “Hot Spots” Conservation efforts are often focused on biodiversity hot spots, relatively small areas that have A large number of endangered and threatened species An exceptional concentration of endemic species, those that are found nowhere else Student Misconceptions and Concerns 1. Although likely sympathetic to the conservation of species, students often do not understand the complexity of the issues. This final chapter section helps to describe some of the recent efforts and challenges of sustainable development. A class discussion about the challenges of conservation might help students realize that there are no simple solutions. Teaching Tips 1. In some ways, highways are types of movement corridors between populations of people living in cities. 2. Sometimes students would like to learn more about conservation but are not aware of professional organizations that study these issues. The Society for Conservation Biology has a web address of: http://www.conbio.org/. 3. If a short field trip is possible, you might wish to take students into a wooded area to generally compare the diversity of life at the edge and deep within the woods. Even the edge of some campus ecosystems might be worthwhile. 4. Consider having your students update the progress of the Kissimmee River Restoration Project.

Equator Figure 20.37 Earth's terrestrial biodiversity hot spots (purple) Figure 20.37

A movement corridor Corridors Is a narrow strip or series of small clumps of suitable habitat Connects otherwise isolated patches Corridors Can promote dispersal and help sustain populations Are especially important to species that migrate between different habitats seasonally Student Misconceptions and Concerns 1. Although likely sympathetic to the conservation of species, students often do not understand the complexity of the issues. This final chapter section helps to describe some of the recent efforts and challenges of sustainable development. A class discussion about the challenges of conservation might help students realize that there are no simple solutions. Teaching Tips 1. In some ways, highways are types of movement corridors between populations of people living in cities. 2. Sometimes students would like to learn more about conservation but are not aware of professional organizations that study these issues. The Society for Conservation Biology has a web address of: http://www.conbio.org/. 3. If a short field trip is possible, you might wish to take students into a wooded area to generally compare the diversity of life at the edge and deep within the woods. Even the edge of some campus ecosystems might be worthwhile. 4. Consider having your students update the progress of the Kissimmee River Restoration Project.

Figure 20.39 An artificial corridor

Restoring Ecosystems Bioremediation uses living organisms to detoxify polluted ecosystems. Researchers are investigating the use of plants to remove toxic substances from contaminated soil. Student Misconceptions and Concerns 1. Although likely sympathetic to the conservation of species, students often do not understand the complexity of the issues. This final chapter section helps to describe some of the recent efforts and challenges of sustainable development. A class discussion about the challenges of conservation might help students realize that there are no simple solutions. Teaching Tips 1. In some ways, highways are types of movement corridors between populations of people living in cities. 2. Sometimes students would like to learn more about conservation but are not aware of professional organizations that study these issues. The Society for Conservation Biology has a web address of: http://www.conbio.org/. 3. If a short field trip is possible, you might wish to take students into a wooded area to generally compare the diversity of life at the edge and deep within the woods. Even the edge of some campus ecosystems might be worthwhile. 4. Consider having your students update the progress of the Kissimmee River Restoration Project.

Figure 20.41 Bioremediation using plants

The Goal of Sustainable Development As the world population grows and becomes more affluent, the demand increases for the provisioning services of ecosystems, such as Food Wood Water Sustainable development aims to Conserve biodiversity Improve the human condition Student Misconceptions and Concerns 1. Although likely sympathetic to the conservation of species, students often do not understand the complexity of the issues. This final chapter section helps to describe some of the recent efforts and challenges of sustainable development. A class discussion about the challenges of conservation might help students realize that there are no simple solutions. Teaching Tips 1. In some ways, highways are types of movement corridors between populations of people living in cities. 2. Sometimes students would like to learn more about conservation but are not aware of professional organizations that study these issues. The Society for Conservation Biology has a web address of: http://www.conbio.org/. 3. If a short field trip is possible, you might wish to take students into a wooded area to generally compare the diversity of life at the edge and deep within the woods. Even the edge of some campus ecosystems might be worthwhile. 4. Consider having your students update the progress of the Kissimmee River Restoration Project.

Figure 20.44 Biophilia Figure 20.44