Communities and Ecosystems

Communities and Ecosystems
Chapter 37 Communities and Ecosystems Lecture by Brian R. Shmaefsky

Introduction: Hungry Hippos
All communities and ecosystems have certain features in common Each type of ecosystem has its own unique structure and dynamics Human activities can disrupt the balance of ecosystems Copyright © 2009 Pearson Education, Inc.

Hippopotamus.

Mzima Springs.

Hippo herd.

COMMUNITY STRUCTURE AND DYNAMICS
COMMUNITY STRUCTURE AND DYNAMICS Copyright © 2009 Pearson Education, Inc.

37.1 A community includes all the organisms inhabiting a particular area
Biological community An assemblage of populations living close enough together for potential interaction Described by its species composition Boundaries of the community vary with research questions Can be a pond Can be the intestinal microbes of a pond organism Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, in each case some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. Teaching Tips 1. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights. 2. In human society, a community might be roughly equivalent to 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 organisms living close enough together for potential interaction. Copyright © 2009 Pearson Education, Inc.

37.2 Interspecific interactions are fundamental to community structure
Interspecific interactions Relationships with other species in the community Interspecific competition Two different species compete for the same limited resource Squirrels and black bears Compete for acorns Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, in each case some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. Teaching Tips 1. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights. 2. In human society, a community might be roughly equivalent to 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 organisms living close enough together for potential interaction. Copyright © 2009 Pearson Education, Inc.

Table 37.2 Interspecific Interactions.

37.3 Competition may occur when a shared resource is limited
Ecological niche Sum of an organism’s use of biotic and abiotic resources Interspecific competition occurs when the niches of two populations overlap Competition lowers the carrying capacity of competing populations Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, in each case some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. 2. The concept of an ecological niche can be confusing. Ecologist Eugene Odum has suggested that an ecological niche is like an organism’s habitat (address) and its occupation combined. Teaching Tips 1. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights. 2. 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. Challenge your students to identify the strategies employed by these restaurants to compete with each other. As each restaurant makes changes, does the other restaurant respond? Restaurants changing strategies in response to each other is analogous to coevolution. Copyright © 2009 Pearson Education, Inc.

37.3 Competition may occur when a shared resource is limited
Interspecific competition between orange-crowned warbler and Virginia’s warbler Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, in each case some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. 2. The concept of an ecological niche can be confusing. Ecologist Eugene Odum has suggested that an ecological niche is like an organism’s habitat (address) and its occupation combined. Teaching Tips 1. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights. 2. 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. Challenge your students to identify the strategies employed by these restaurants to compete with each other. As each restaurant makes changes, does the other restaurant respond? Restaurants changing strategies in response to each other is analogous to coevolution. Copyright © 2009 Pearson Education, Inc.

Figure 37.3A Virginia’s warbler (Vermivora virginiae).

Figure 37.3B Orange-crowned warbler (Vermivora celata).

37.4 Mutualism benefits both partners
Reef-building corals require mutualism Photosynthetic dinoflagellates Live in the cells of each coral polyp Produce sugars used by the polyps Provide at least half of the energy used by the coral animals Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, in each case some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. Teaching Tips 1. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights. 2. Students who are business-oriented may also enjoy this analogy. Many corporate leaders describe the best business deals as mutualistic, fostering a win-win relationship. For example, perhaps a new company creates a marketable product from another company’s wastes. Video: Clownfish and Anemone Copyright © 2009 Pearson Education, Inc.

Figure 37.4 Coral polyps.

Video: Seahorse Camouflage
37.5 EVOLUTION CONNECTION: Predation leads to diverse adaptations in prey species Predation benefits the predator but kills the prey Prey adapt using protective strategies Camouflage Mechanical defenses Chemical defenses Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, in each case some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. Teaching Tips 1. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights. 2. Rattlesnakes are a good example of a highly specialized predator. Since they are unable to move fast enough to catch their prey, rattlesnakes typically ambush them, a process facilitated by their camouflaged bodies. They often feed during the cooler parts of the day, using heat-detecting facial pits to identify prey before injecting them with fast-acting venom. The prey is immediately released (perhaps to avoid damage to the snake from struggling prey), but is disabled by the venom within seconds. The rattlesnake then uses a variety of senses to track the prey the short distance to where it has collapsed. Video: Seahorse Camouflage Copyright © 2009 Pearson Education, Inc.

Figure 37.5A Camouflage: a gray tree frog on bark.

Figure 37.5B Chemical defenses: the poison-arrow frog.

37.6 EVOLUTION CONNECTION: Herbivory leads to diverse adaptations in plants
Herbivory is not usually fatal Plants must expend energy to replace the loss Plants have numerous defenses against herbivores Spines and thorns Chemical toxins Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, in each case some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. Teaching Tips 1. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights. 2. Coevolution is illustrated by organisms that exhibit reciprocal evolutionary adaptations. Challenge students to explain how rewarding a pollinator with nectar has benefited some plants. Why would plants that have adaptations for only certain pollinators have an advantage? In many cases, pollinators that are restricted to certain species are more likely to transport pollen between members of that species instead of wasting pollen by taking it to different species Copyright © 2009 Pearson Education, Inc.

37.6 EVOLUTION CONNECTION: Herbivory leads to diverse adaptations in plants
Herbivores and plants undergo coevolution A change in one species acts as a new selective force on another Poison-resistant caterpillars seem to be a strong selective force for Passiflora plants Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, in each case some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. Teaching Tips 1. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights. 2. Coevolution is illustrated by organisms that exhibit reciprocal evolutionary adaptations. Challenge students to explain how rewarding a pollinator with nectar has benefited some plants. Why would plants that have adaptations for only certain pollinators have an advantage? In many cases, pollinators that are restricted to certain species are more likely to transport pollen between members of that species instead of wasting pollen by taking it to different species Copyright © 2009 Pearson Education, Inc.

Eggs Sugar deposits Figure 37.6 Coevolution: Heliconius and the passionflower vine (Passiflora).

37.7 Parasites and pathogens can affect community composition
A parasite lives on or in a host from which it obtains nourishment Internal parasites include nematodes and tapeworms External parasites include mosquitoes and ticks Pathogens are disease-causing parasites Pathogens can be bacteria, viruses, fungi, or protists Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, in each case some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. Teaching Tips 1. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights. 2. Pathogens are probably what most people refer to as germs. Students might believe that these terms refer to some specific type of organism. Copyright © 2009 Pearson Education, Inc.

Figure 37.7 Aphids parasitizing a plant.

37.7 Parasites and pathogens can affect community composition
Non-native pathogens can have rapid and dramatic impacts American chestnut devastated by chestnut blight protist A fungus-like pathogen currently causing sudden oak death on the West Coast Non-native pathogens can cause a decline of the ecosystem Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, in each case some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. Teaching Tips 1. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights. 2. Pathogens are probably what most people refer to as germs. Students might believe that these terms refer to some specific type of organism. Copyright © 2009 Pearson Education, Inc.

37.8 Trophic structure is a key factor in community dynamics
Trophic structure A pattern of feeding relationships consisting of several different levels Food chain Sequence of food transfer up the trophic levels Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, in each case some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. Teaching Tips 1. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights. 2. Students have often had prior exposure to the concepts of food webs and food chains. Present a food web (perhaps Figure 37.9) 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. Copyright © 2009 Pearson Education, Inc.

Producers Support all other trophic levels Autotrophs Photosynthetic producers Plants on land Cyanobacteria in water Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, in each case some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. Teaching Tips 1. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights. 2. Students have often had prior exposure to the concepts of food webs and food chains. Present a food web (perhaps Figure 37.9) 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. Copyright © 2009 Pearson Education, Inc.

Consumers Heterotrophs Primary consumers Secondary consumers Tertiary consumers Quaternary consumers Detritivores and decomposers Derive energy from dead matter and wastes Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, in each case some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. Teaching Tips 1. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights. 2. Students have often had prior exposure to the concepts of food webs and food chains. Present a food web (perhaps Figure 37.9) 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. Video: Shark Eating a Seal Copyright © 2009 Pearson Education, Inc.

A terrestrial food chain An aquatic food chain
Figure 37.8 Two food chains. Plant Phytoplankton Producers A terrestrial food chain An aquatic food chain

Figure 37.8 Two food chains. Grasshopper Primary consumers Zooplankton Plant Phytoplankton Producers A terrestrial food chain An aquatic food chain

Secondary consumers Primary consumers
Mouse Secondary consumers Herring Figure 37.8 Two food chains. Grasshopper Primary consumers Zooplankton Plant Phytoplankton Producers A terrestrial food chain An aquatic food chain

Tertiary consumers Secondary consumers Primary consumers
Snake Tertiary consumers Tuna Mouse Secondary consumers Herring Figure 37.8 Two food chains. Grasshopper Primary consumers Zooplankton Plant Phytoplankton Producers A terrestrial food chain An aquatic food chain

Trophic level Quaternary consumers Hawk Killer whale Snake Tertiary consumers Tuna Mouse Secondary consumers Herring Figure 37.8 Two food chains. Grasshopper Primary consumers Zooplankton Plant Phytoplankton Producers A terrestrial food chain An aquatic food chain

37.9 Food chains interconnect, forming food webs
Food web A network of interconnecting food chains Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, in each case some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. Teaching Tips 1. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights. 2. Students have often had prior exposure to the concepts of food webs and food chains. Present a food web (perhaps Figure 37.9) 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. Copyright © 2009 Pearson Education, Inc.

Quaternary, tertiary, and secondary consumers Tertiary and secondary
primary consumers Primary consumers Figure 37.9 A food web. Producers (plants)

37.10 Species diversity includes relative abundance and species richness
Species diversity defined by two components Species richness Relative abundance Plant species diversity in a community affects the animals Species diversity has consequences for pathogens Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, in each case some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. Teaching Tips 1. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights. Copyright © 2009 Pearson Education, Inc.

Figure 37.10A Species composition of woodlot A.

Figure 37.10B Species composition of woodlot B.

Table 37.10 Relative Abundance of Tree Species in Woodlots A and B.

37.11 Keystone species have a disproportionate impact on diversity
Keystone species A species whose impact on its community is larger than its biomass or abundance indicates Occupies a niche that holds the rest of its community in place Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, in each case some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. Teaching Tips 1. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights. 2. Many keystone species have been identified in ecosystems, including sea otters, elephants, freshwater bass, and Pisaster, a sea star noted in Figure Challenge your class to explain how the concept of keystone species impacts the efforts of conservation biologists. Why might some species be more important to conserve? Copyright © 2009 Pearson Education, Inc.

Keystone Keystone absent
Figure 37.11A Arch collapse with removal of keystone.

Figure 37.11B A Pisaster sea star, a keystone species, eating a mussel.

Figure 37.11C Diadema sea urchins grazing on reef.

Figure 37.11D Reef overgrown by fleshy seaweeds.

37.12 Disturbance is a prominent feature of most communities
Disturbances Events that damage biological communities Storms, fire, floods, droughts, overgrazing, or human activity The types, frequency, and severity of disturbances vary from community to community Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, in each case some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. 2. The idea 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. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights. 2. Before and after images of the impact and recovery of an ecosystem from a natural disaster can be more powerful than any verbal explanation of the process. 3. Depending upon your location and its circumstances, consider a short field trip on or near your campus to show disturbed regions and signs of recovery. Copyright © 2009 Pearson Education, Inc.

Communities change drastically following a severe disturbance Ecological succession Colonization by a variety of species A success of change gradually replaces other species Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, in each case some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. 2. The idea 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. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights. 2. Before and after images of the impact and recovery of an ecosystem from a natural disaster can be more powerful than any verbal explanation of the process. 3. Depending upon your location and its circumstances, consider a short field trip on or near your campus to show disturbed regions and signs of recovery. Copyright © 2009 Pearson Education, Inc.

Primary succession Begins in a virtually lifeless area with no soil Secondary succession When a disturbance destroyed an existing community but left the soil intact Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, in each case some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. 2. The idea 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. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights. 2. Before and after images of the impact and recovery of an ecosystem from a natural disaster can be more powerful than any verbal explanation of the process. 3. Depending upon your location and its circumstances, consider a short field trip on or near your campus to show disturbed regions and signs of recovery. Copyright © 2009 Pearson Education, Inc.

Annual plants Perennial plants and grasses Shrubs Softwood trees
Figure Stages in secondary succession of abandoned farm field. Annual plants Perennial plants and grasses Shrubs Softwood trees such as pines Hardwood trees Time

37.13 CONNECTION: Invasive species can devastate communities
Introduction of rabbits in Australia Student Misconceptions and Concerns 1. For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, in each case some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems. Teaching Tips 1. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights. 2. The United States Department of Agriculture sponsors the National Invasive Species Information Center, which maintains a website at Copyright © 2009 Pearson Education, Inc.

Frontier of rabbit spread
600 Km 1980 1910 1910 1900 1910 1920 1920 Australia 1910 1890 1900 Figure 37.13A The spread of rabbits in Australia. 1910 1880 1920 1920 1890 1870 1880 Key 1870 Frontier of rabbit spread Origin: 1860

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

ECOSYSTEM STRUCTURE AND DYNAMICS
ECOSYSTEM STRUCTURE AND DYNAMICS Copyright © 2009 Pearson Education, Inc.

37.14 Ecosystem ecology emphasizes energy flow and chemical cycling
Ecosystem All the organisms in a community as well as the abiotic environment Components of ecosystems Energy flow Passage of energy through the ecosystem Chemical cycling Transfer of materials within the ecosystem Student Misconceptions and Concerns 1. Without an understanding of basic physics and the inefficiency of aerobic metabolism, students might not understand how chemical energy in food is lost as heat. Consider expanding upon the explanations given in the book. Teaching Tips 1. The heat generated as a by-product of metabolism, which is quite evident during strenuous exercise, is much like the heat produced by a running automobile engine. In both circumstances, heat is a by-product of the fuel-burning process. 2. Energy flow through an ecosystem is analogous to the flow of fuel through a car or electricity through a vacuum cleaner. These systems will not work without a steady input. NASA, however, must rely upon some closed systems for its spacecrafts. Students might enjoy investigating the recycling of gases and fluids in these systems. Copyright © 2009 Pearson Education, Inc.

37.14 Ecosystem ecology emphasizes energy flow and chemical cycling
A terrarium has the components of an ecosystem Student Misconceptions and Concerns 1. Without an understanding of basic physics and the inefficiency of aerobic metabolism, students might not understand how chemical energy in food is lost as heat. Consider expanding upon the explanations given in the book. Teaching Tips 1. The heat generated as a by-product of metabolism, which is quite evident during strenuous exercise, is much like the heat produced by a running automobile engine. In both circumstances, heat is a by-product of the fuel-burning process. 2. Energy flow through an ecosystem is analogous to the flow of fuel through a car or electricity through a vacuum cleaner. These systems will not work without a steady input. NASA, however, must rely upon some closed systems for its spacecrafts. Students might enjoy investigating the recycling of gases and fluids in these systems. For the BLAST Animation Energy Flow, go to Animation and Video Files. Copyright © 2009 Pearson Education, Inc.

Chemical cycling Energy flow Chemical energy Light energy Heat energy
Figure A terrarium ecosystem. Chemical elements Bacteria and fungi

37.15 Primary production sets the energy budget for ecosystems
Primary production The amount of solar energy converted to chemical energy Carried out by producers Produces biomass Amount of living organic material in an ecosystem Teaching Tips 1. Challenge students to explain why the areas of greatest primary production are near the equator. (Answer: primary production is a consequence of photosynthesis. Regions near the equator receive the highest levels of solar input.) Copyright © 2009 Pearson Education, Inc.

37.15 Primary production sets the energy budget for ecosystems
Primary production of different ecosystems Teaching Tips 1. Challenge students to explain why the areas of greatest primary production are near the equator. (Answer: primary production is a consequence of photosynthesis. Regions near the equator receive the highest levels of solar input.) Copyright © 2009 Pearson Education, Inc.

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

37.16 Energy supply limits the length of food chains
A pyramid of production Illustrates the cumulative loss of energy transfer in a food chain Teaching Tips 1. Why do food chains and webs typically have only three to five levels? This question, which is seldom considered by students, is addressed directly in this section of the chapter. It can spark a good opening discussion before a lecture on food chains and food webs. Copyright © 2009 Pearson Education, Inc.

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

37.17 CONNECTION: A production pyramid explains why meat is a luxury for humans
The dynamics of energy flow apply to the human population Student Misconceptions and Concerns 1. The environmental impact of eating farm animals is little appreciated by most students. This chapter section helps explain the basis of the increased costs associated with a high-meat diet. Teaching Tips 1. Some students might be interested in eating more proteins and fewer carbohydrates because of certain recently promoted diet plans. But do high protein diets always require the consumption of more meat? The many sources of plant proteins might be surprising to students. Some high-protein vegetarian options are described by the Vegetarian Society at its website, Copyright © 2009 Pearson Education, Inc.

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

37.18 Chemicals are cycled between organic matter and abiotic reservoirs
Ecosystems are supplied with a continual influx of energy Sun Earth’s interior Life also depends on the recycling of chemicals Organisms acquire chemicals as nutrients and lose chemicals as waste products Student Misconceptions and Concerns 1. Students are unlikely to have any prior knowledge of biogeochemical cycles. Although some transfers between the biotic and abiotic components of ecosystems, such as the use of fertilizer on plants, may be known to them, the broader fact that the biosphere is a self-cycling system is not appreciated by most students. Before you lecture, consider asking your students to explain how carbon, phosphorus, and nitrogen cycle through the atmosphere. Pre testing your students on their knowledge can confirm both what they understand and what they may need explained to them in more detail. Teaching Tips 1. As you discuss the importance of the biogeochemical cycles, consider explaining the basic label information provided on a container of plant fertilizer. Typically, plant fertilizers contain various forms of nitrogen and phosphorus, which are essential chemicals for growth. Copyright © 2009 Pearson Education, Inc.

37.18 Chemicals are cycled between organic matter and abiotic reservoirs
Biogeochemical cycles Cycle chemicals between organisms and the Earth Can be local or global Decomposers play a central role in biogeochemical cycles Student Misconceptions and Concerns 1. Students are unlikely to have any prior knowledge of biogeochemical cycles. Although some transfers between the biotic and abiotic components of ecosystems, such as the use of fertilizer on plants, may be known to them, the broader fact that the biosphere is a self-cycling system is not appreciated by most students. Before you lecture, consider asking your students to explain how carbon, phosphorus, and nitrogen cycle through the atmosphere. Pre testing your students on their knowledge can confirm both what they understand and what they may need explained to them in more detail. Teaching Tips 1. As you discuss the importance of the biogeochemical cycles, consider explaining the basic label information provided on a container of plant fertilizer. Typically, plant fertilizers contain various forms of nitrogen and phosphorus, which are essential chemicals for growth. Copyright © 2009 Pearson Education, Inc.

Consumers Producers Decomposers Nutrients available to producers
3 2 Producers Decomposers 1 Nutrients available to producers 4 Figure A general model of biogeochemical cycling of nutrients. Abiotic reservoir Geologic processes

37.19 The carbon cycle depends on photosynthesis and respiration
Carbon is the major ingredient of all organic molecules The return of CO2 to the atmosphere by respiration closely balances its removal by photosynthesis The carbon cycle is affected by burning wood and fossil fuels Student Misconceptions and Concerns 1. Students are unlikely to have any prior knowledge of biogeochemical cycles. Although some transfers between the biotic and abiotic components of ecosystems, such as the use of fertilizer on plants, may be known to them, the broader fact that the biosphere is a self-cycling system is not appreciated by most students. Before you lecture, consider asking your students to explain how carbon, phosphorus, and nitrogen cycle through the atmosphere. Pre testing your students on their knowledge can confirm both what they understand and what they may need explained to them in more detail. Teaching Tips 1. As you discuss the importance of the biogeochemical cycles, consider explaining the basic label information provided on a container of plant fertilizer. Typically, plant fertilizers contain various forms of nitrogen and phosphorus, which are essential chemicals for growth. 2. As rising atmospheric carbon dioxide levels affect global climate, carbon cycling has become an increasingly important issue. If your course will not cover Module 38.5, on global warming, consider including a brief discussion of the topic here. For the BLAST Animation Carbon Cycle, go to Animation and Video Files. For the Discovery Video Trees, go to Animation and Video Files. Copyright © 2009 Pearson Education, Inc.

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

37.20 The phosphorus cycle depends on the weathering of rock
Organisms require phosphorus for nucleic acids, phospholipids, and ATP Plants absorb phosphate ions in the soil and build them into organic compounds Phosphates are returned to the soil by decomposers Phosphate levels in aquatic ecosystems are typically low enough to be a limiting factor Student Misconceptions and Concerns 1. Students are unlikely to have any prior knowledge of biogeochemical cycles. Although some transfers between the biotic and abiotic components of ecosystems, such as the use of fertilizer on plants, may be known to them, the broader fact that the biosphere is a self-cycling system is not appreciated by most students. Before you lecture, consider asking your students to explain how carbon, phosphorus, and nitrogen cycle through the atmosphere. Pre testing your students on their knowledge can confirm both what they understand and what they may need explained to them in more detail. Teaching Tips 1. As you discuss the importance of the biogeochemical cycles, consider explaining the basic label information provided on a container of plant fertilizer. Typically, plant fertilizers contain various forms of nitrogen and phosphorus, which are essential chemicals for growth. 2. Discussing the movements of water through your local community can help students better understand the concept of biogeochemical cycling. You may want to ask students to consider all of the possible inputs of water into your community as well as the possible routes of exit. 3. As noted in Module 37.20, phosphate contamination of aquatic systems typically leads to increased algal growth and potentially disastrous fish kills. Copyright © 2009 Pearson Education, Inc.

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

37.21 The nitrogen cycle depends on bacteria
Nitrogen is an essential component of proteins and nucleic acids Nitrogen has two abiotic reservoirs Air Soil Nitrogen fixation converts N2 to nitrogen used by plants Carried out by some bacteria and cyanobacteria Student Misconceptions and Concerns 1. Students are unlikely to have any prior knowledge of biogeochemical cycles. Although some transfers between the biotic and abiotic components of ecosystems, such as the use of fertilizer on plants, may be known to them, the broader fact that the biosphere is a self-cycling system is not appreciated by most students. Before you lecture, consider asking your students to explain how carbon, phosphorus, and nitrogen cycle through the atmosphere. Pre testing your students on their knowledge can confirm both what they understand and what they may need explained to them in more detail. Teaching Tips 1. The nitrogen-fixing bacteria living in the roots of soybeans add nitrogen to the soil. Corn does not enjoy this same relationship with bacteria. However, by rotating corn and soybean crops, farmers can allow corn crops to use some of the nitrogen fixed by the soybean crop in the previous year. Such rotation has other benefits. Since corn is a monocot and soybeans are dicots, few pests attack both corn and soybeans. Thus, crop rotation also helps to control the pest populations that target each type of plant. For the BLAST Animation Nitrogen Cycle, go to Animation and Video Files. Copyright © 2009 Pearson Education, Inc.

Nitrogen (N2) in atmosphere
8 Plant Animal 6 Organic compounds Organic compounds Assimilation by plants Nitrogen fixation 1 5 Death; wastes Denitrifiers 3 Nitrogen-fixing bacteria in root nodules Nitrates in soil (NO3–) Detritus Figure The nitrogen cycle. Free-living nitrogen-fixing bacteria and cyanobacteria Decomposers Nitrifying bacteria 4 7 Decomposition Nitrogen fixation Ammonium (NH4+) in soil 2

37.22 CONNECTION: Ecosystem alteration can upset chemical cycling
Chemical cycling in an ecosystem depends on The web of feeding Relationships between plants, animals, and detritivores Geologic processes Altering an environment can cause severe losses in chemical cycling Erosion Acid rain Teaching Tips 1. The studies of the Hubbard Brook Experimental Forest provide an opportunity to explain how basic principles of scientific investigation are applied to ecological studies. Consider discussing the difficulties of conducting these broad experiments in other locations, where water cycling may not be so restricted and other biogeochemical cycles not as well defined. Copyright © 2009 Pearson Education, Inc.

Figure 37.22A A dam at the Hubbard Brook study site.

Figure 37.22B Logged watershed in the Hubbard Brook Forest.

Nitrate concentration in runoff (mg/L)
80.0 Deforested 60.0 40.0 20.0 Nitrate concentration in runoff (mg/L) Completion of tree cutting 4.0 3.0 Control Figure 37.22C The loss of nitrate from a deforested watershed. 2.0 1.0 1965 1966 1967 1968

37.23 TALKING ABOUT SCIENCE: David Schindler talks about the effects of nutrients on freshwater ecosystems Major changes in terrestrial ecosystems disrupt chemical cycling These changes can increase nutrients in aquatic ecosystems Algal and cyanobacteria blooms Eutrophication Teaching Tips 1. Dr. Schindler’s test of the effect of phosphorus pollution in a lake is a fine example of a carefully controlled environmental study. Consider presenting its design to students as a review of the basic process of science. Copyright © 2009 Pearson Education, Inc.

Video: Cyanobacteria (Oscillatoria)
37.23 TALKING ABOUT SCIENCE: David Schindler talks about the effects of nutrients on freshwater ecosystems The most serious current threats Acid precipitation Changes in land use Climate warming Teaching Tips 1. Dr. Schindler’s test of the effect of phosphorus pollution in a lake is a fine example of a carefully controlled environmental study. Consider presenting its design to students as a review of the basic process of science. Video: Cyanobacteria (Oscillatoria) Copyright © 2009 Pearson Education, Inc.

Figure 37.23A David Schindler.

Figure 37.23B Experimental eutrophication of part of a lake (phosphorus added to basin at bottom of photo).

Producer Herbivore (primary consumer) Carnivore (secondary consumer) Energy flow Decomposers Chemical cycling

involve the processes of
Ecosystems involve the processes of (a) (b) in which in which makes a chemical elements (c) one-way trip is converted by are incorporated by from from (d) (e) solar energy to chemical energy to heat to chemical energy of into components of organic molecules detritivores return elements to which pass through (f)

You should now be able to
Describe the characteristics of a community Explain how interspecific interactions affect the dynamics of populations Describe the trophic structure of a community Explain how species diversity is measured Describe the role of environmental disturbance on ecological succession Explain energy and nutrient cycling in ecosystems Copyright © 2009 Pearson Education, Inc.

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