Sample Student Edition CHAPTER 6 For Review Purposes Only 2 BiologyMiller & Levine ogy Student Edition Sampler Biol Chapter 6 Communities and Ecosystem Dynamics Miller & Levine & Miller Chapter Opener/Case Study .......................................... 4 Lesson 6.1 Habitats, Niches, and Species Interactions .................... 6 Lesson 6.2 Succession .................................................................... 14 Lesson 6.3 Biodiversity, Ecosystems, and Resilience ..................... 18 Case Study Wrap-Up ................................................... .22 Study Guide .................................................................. 24 Performance-Based Assessment ................................. .26 Assessment ................................................................... 28 End-of-Course Assessment .......................................... 31 3 Communities and CHAPTER 6 Ecosystem Dynamics CASE STUDY 6.1 6.2 6.3 Habitats, Niches, and Succession Biodiversity, Ecosystems, How do species interactions shape Go Online to Species Interactions and Resilience access your digital course. ecosystems? VIDEO As dusk falls over Yellowstone National Park, elk emerge from dense woods to browse on ten- Beavers build dams that der willows along a stream. Suddenly, they freeze. An instant later, wolves dash from the forest, AUDIO shape river ecosystems. aiming for a kill. The elk react in the nick of time, bolting out of reach. This hunt, like most, has INTERACTIVITY failed. But those elk have been attacked here before. Will they now decide to graze elsewhere? This dramatic encounter offers a window into In an effort to restore these habitats, biol- eTEXT community ecology, the study of interactions ogists reintroduced wolves in the late 1990s, among species in a food web. As it turns and have been monitoring the situation ever ANIMATION out, human disturbance of this web set the since. After so many changes spread through stage for experiments that have improved our the ecosystem, could returning wolves to the VIRTUAL LAB understanding of both wild ecosystems and system “reboot” it? those affected by human activity. In some places, the answer seems to be ASSESSMENT The story began during the 1800s, as yes. As wolf populations grew, elk populations ranchers started shooting and poisoning fell, and willows grew back. Beavers returned, wolves that preyed on livestock. By the built dams, and the ecosystem was restored. 1920s, they had eliminated all wolves in the But elsewhere, willows didn’t recover after elk region. Elk populations boomed, and they populations dropped. Beavers didn’t return. overgrazed willows along streambeds. The system seemed stuck in an altered state. The overgrazing affected beavers, which It turns out that this complex community is eat willows and also use them to build dams hard to understand and rebuild. Yellowstone is that create ponds. Those dams create marshy home to more than 60 other mammal species, areas, keeping the water table close to the some of which prey on elk, while others are surface and providing good growing condi- alternate prey for wolves. Also, in some parts of tions for willows. Streams with dams and wil- Yellowstone, the loss of beavers changed stream lows also offer homes to fishes and birds. structure in ways that couldn’t easily be reversed. By the 1950s, elk overgrazing caused bea- This case raises many questions. How do ver populations to collapse. Dams and marshy predators and prey affect each other? How do areas disappeared. Streams flowed faster, community structure and complexity affect spe- carving deeper channels. The water table fell. cies diversity? Why is this diversity important? Fishes and birds suffered. These changes, all What factors change an ecosystem? What do HS-LS2-2, HS-LS2-6, HS-LS2-7, resulting from removal of one key predator, those changes look like? Can they be reversed? HS-LS4-6, HS-ETS1-3, HS-ESS3-4 are called a trophic cascade. In this cascade, Throughout this chapter, look for con- CCSS.MATH.CONTENT.MP4, CCSS.MATH.CONTENT.HSS.IC.A.1, wolf removal reshaped both the biological nections to the CASE STUDY to help you CCSS.ELA-LITERACY.WHST.9-10.2, community and its physical environment. answer these questions. CCSS.ELA-LITERACY.RST.9-10.1 172 Chapter 6 Communities and Ecosystem Dynamics Unit 2 Ecology 173 4 Communities and CHAPTER 6 Ecosystem Dynamics CASE STUDY 6.1 6.2 6.3 Habitats, Niches, and Succession Biodiversity, Ecosystems, How do species interactions shape Go Online to Species Interactions and Resilience access your digital course. ecosystems? VIDEO As dusk falls over Yellowstone National Park, elk emerge from dense woods to browse on ten- Beavers build dams that der willows along a stream. Suddenly, they freeze. An instant later, wolves dash from the forest, AUDIO shape river ecosystems. aiming for a kill. The elk react in the nick of time, bolting out of reach. This hunt, like most, has INTERACTIVITY failed. But those elk have been attacked here before. Will they now decide to graze elsewhere? This dramatic encounter offers a window into In an effort to restore these habitats, biol- eTEXT community ecology, the study of interactions ogists reintroduced wolves in the late 1990s, among species in a food web. As it turns and have been monitoring the situation ever ANIMATION out, human disturbance of this web set the since. After so many changes spread through stage for experiments that have improved our the ecosystem, could returning wolves to the VIRTUAL LAB understanding of both wild ecosystems and system “reboot” it? those affected by human activity. In some places, the answer seems to be ASSESSMENT The story began during the 1800s, as yes. As wolf populations grew, elk populations ranchers started shooting and poisoning fell, and willows grew back. Beavers returned, wolves that preyed on livestock. By the built dams, and the ecosystem was restored. 1920s, they had eliminated all wolves in the But elsewhere, willows didn’t recover after elk region. Elk populations boomed, and they populations dropped. Beavers didn’t return. overgrazed willows along streambeds. The system seemed stuck in an altered state. The overgrazing affected beavers, which It turns out that this complex community is eat willows and also use them to build dams hard to understand and rebuild. Yellowstone is that create ponds. Those dams create marshy home to more than 60 other mammal species, areas, keeping the water table close to the some of which prey on elk, while others are surface and providing good growing condi- alternate prey for wolves. Also, in some parts of tions for willows. Streams with dams and wil- Yellowstone, the loss of beavers changed stream lows also offer homes to fishes and birds. structure in ways that couldn’t easily be reversed. By the 1950s, elk overgrazing caused bea- This case raises many questions. How do ver populations to collapse. Dams and marshy predators and prey affect each other? How do areas disappeared. Streams flowed faster, community structure and complexity affect spe- carving deeper channels. The water table fell. cies diversity? Why is this diversity important? Fishes and birds suffered. These changes, all What factors change an ecosystem? What do HS-LS2-2, HS-LS2-6, HS-LS2-7, resulting from removal of one key predator, those changes look like? Can they be reversed? HS-LS4-6, HS-ETS1-3, HS-ESS3-4 are called a trophic cascade. In this cascade, Throughout this chapter, look for con- CCSS.MATH.CONTENT.MP4, CCSS.MATH.CONTENT.HSS.IC.A.1, wolf removal reshaped both the biological nections to the CASE STUDY to help you CCSS.ELA-LITERACY.WHST.9-10.2, community and its physical environment. answer these questions. CCSS.ELA-LITERACY.RST.9-10.1 172 Chapter 6 Communities and Ecosystem Dynamics Unit 2 Ecology 173 5 Microhabitats Many small organisms live only in very small parts Habitats, Niches, and of the larger habitats we humans see. To understand where these organisms live and why, we must examine environmental conditions Figure 6-1 LESSON 6.1 Species Interactions on the much smaller scale that matters to those organisms. Look under Microenvironments leaves on a forest floor, or under the bark of a rotting log, and you will discover many different smaller microenvironments or microhabitats. Each part of a tree, including Many different microhabitats can exist within short distances fallen branches, provides various microhabitats with microclimates. KEY QUESTIONS of each other, as shown in Figure 6-1. From worm tunnels in the The microhabitat of moths is dry • What factors ground, to beetle burrows under tree bark, each microhabitat has and exposed to sun, whereas the determine and its own set of environmental conditions called its microclimate. For salamander lives in moist, shel- describe habitats and example, fungi that live on tree roots are affected mainly by the tered spaces. What other micro- niches? microclimatic conditions within a few millimeters of their location. habitats do you see? • How does competition shape communities? Moray eels hide in rocky • How does herbivory crevices and coral reefs. shape communities? • How do keystone species shape communities? • What are the three If you ask someone where an organism lives, they might answer Moth and its primary ways that “the Caribbean” or “the west coast.” That kind of answer doesn’t tell caterpillar organisms depend on you very much. To learn more about a person, you need more data. each other? Answers like “Miami” or “the Bay Area” still don’t tell