Sample Student Edition CHAPTER 6 for Review Purposes Only 2

Home , Climax community, Ecosystem diversity

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?

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 you all you’d like to know. Where in those cities? Miami Beach, or Downtown? San HS-LS2-2: Use mathematical Francisco, or Oakland? What street address? Is there an apartment representations to support and revise explanations based on evidence about number? What does he or she do for a living? That’s the kind of spe- factors affecting biodiversity and populations in ecosystems of different cific information ecologists seek about species and ecosystems. Emerald scales. Habitat and Niche ash borer Termites VOCABULARY Biomes, as you learned in Chapter 3, are large areas with broadly habitat • tolerance similar environmental conditions that can house a variety of different Bird louse Bioﬁlm niche • resource ecosystems. Within those ecosystems, the actual place an organism competitive exclusion lives is called its habitat. A habitat can be described as an area principle • keystone species symbiosis • commensalism with a particular combination of physical and biological environ- mutualism • parasitism mental factors that affect which organisms can live within it. You Spider can think of a habitat as an organism’s ecological “address.“ READING TOOL Knowing the habitat an organism lives in, however, doesn’t pro- Beetle Identify each main idea vide much more information than knowing the city a person lives in. and the supporting details Think about habitats like the Everglades, or a redwood forest, or a under each heading as coral reef. Large animals, such as Florida panthers, black bears, or you read. Complete the sharks, might roam through large parts of those habitats, and might Shelf fungi chart in your Biology also spend time in other habitats nearby. We can understand that Foundations Workbook. situation, because we easily recognize the kinds of environmental conditions that affect organisms our own size. But what about smaller Salamander animals, such as insects, birds, or eels? They might be found only Bacteria in certain parts of their habitats. To understand why, we need to Millipede look closely.

Earthworm

174 Chapter 6 Communities and Ecosystem Dynamics 6 Fungal hyphae 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 you all you’d like to know. Where in those cities? Miami Beach, or Downtown? San HS-LS2-2: Use mathematical Francisco, or Oakland? What street address? Is there an apartment representations to support and revise explanations based on evidence about number? What does he or she do for a living? That’s the kind of spe- factors affecting biodiversity and populations in ecosystems of different cific information ecologists seek about species and ecosystems. Emerald scales. Habitat and Niche ash borer Termites VOCABULARY Biomes, as you learned in Chapter 3, are large areas with broadly habitat • tolerance similar environmental conditions that can house a variety of different Bird louse Bioﬁlm niche • resource ecosystems. Within those ecosystems, the actual place an organism competitive exclusion lives is called its habitat. A habitat can be described as an area principle • keystone species symbiosis • commensalism with a particular combination of physical and biological environ- mutualism • parasitism mental factors that affect which organisms can live within it. You Spider can think of a habitat as an organism’s ecological “address.“ READING TOOL Knowing the habitat an organism lives in, however, doesn’t pro- Beetle Identify each main idea vide much more information than knowing the city a person lives in. and the supporting details Think about habitats like the Everglades, or a redwood forest, or a under each heading as coral reef. Large animals, such as Florida panthers, black bears, or you read. Complete the sharks, might roam through large parts of those habitats, and might Shelf fungi chart in your Biology also spend time in other habitats nearby. We can understand that Foundations Workbook. situation, because we easily recognize the kinds of environmental conditions that affect organisms our own size. But what about smaller Salamander animals, such as insects, birds, or eels? They might be found only Bacteria in certain parts of their habitats. To understand why, we need to Millipede look closely.

Earthworm

174 Chapter 6 Communities and Ecosystem Dynamics 7 Fungal hyphae BUILD VOCABULARY Microbiomes The discovery of microbial communities called The Niche The habitat of a species, or its ecological address, only READING TOOL Prefixes The prefix micro- microbiomes has dramatically changed our understanding of ecology. tells part of its story. Ecologists also study a species’ ecological occu- Make a concept map means “small” or “minute.” These communities inhabit places never before considered “habi- pation, or how it stays alive. A niche (nich) describes where an organ- to help understand an Microbiomes may be smaller tats,” and perform more important functions than anyone imagined. ism lives and what it does “for a living,” including they way it interacts organism’s niche. Use than what you can see with the For example, in addition to decomposing organic matter, soil micro- with biotic and abiotic factors. A species’ niche includes the range the terms abiotic, biotic, naked eye. biomes, like the ones shown in Figure 6-1, also affect plant health, of physical and biological conditions in which it can survive and ecological address, food, and the ability of roots to absorb water and nutrients. Some members reproduce, as well as the way it obtains resources it needs. habitat, light, niche, of the microbiome transfer carbon from plants to fungi, and from one reproduction, resources, plant to another. Others carry “messages“ between plants. Many Resources and the Niche The term resource can refer to any temperature, and water. ecological interactions, including several discussed in this chapter, are necessity of life. For plants, necessary resources include sunlight, regulated by microbiomes. Even your mouth, gut, and skin are home water, and soil nutrients. For animals, resources can include nesting to microbiomes whose inhabitants outnumber your own cells and space, shelter, types of food, and places to feed. powerfully influence your health! Physical Aspects of the Niche A species’ niche includes all the Tolerance Every species has its own range of tolerance, the physical, or abiotic, factors to which it is adapted. Most amphibians, variety of environmental conditions within which it can survive and for example, absorb and lose water through their skin, so they must reproduce, as shown in Figure 6-2. Within a species’ optimum range, live in moist places. If an area is too hot and dry for too long, most environmental conditions enable individuals to find enough energy amphibians cannot survive. In contrast, plants such as cacti, which and nutrients to maintain homeostasis, to grow and reproduce. are adapted to deserts will die if their roots stay wet for too long.

Biological Aspects of the Niche A species’ niche also involves Figure 6-2 Tolerance the biological, or biotic, factors it requires for survival. Examples of biological factors include the food an organism eats, the way it Tolerance Lower limit Zone of Zone of Upper limit of tolerance stress stress of tolerance obtains that food, and when and how it reproduces. Communities of The graph shows the response of a Optimum range seabirds on a remote island, for example, may all nest in the same hypothetical organism to a single envi- habitat. But each species may prey on fishes of different sizes and ronmental variable, such as sunlight or hunt in different places. Thus, each species occupies a distinct niche. temperature.  Interpret Graphs Why Figure 6-3 is the same graph useful for many differ- The warblers shown in each rely on a different physical ent environmental factors? space and biotic factors, and therefore occupy a distinct niche. Population Spruce Tree 18 Figure 6-3 Low Range of High Resource Sharing Environmental Variable Each of these warbler species has a different niche in its spruce tree habitat. By feeding If one or more environmental conditions, such as temperature, Cape May Warbler in different areas of the tree, rise above or fall below that optimum range then individuals experi- 12 the birds avoid competing ence stress. Why? Organisms under stress must expend more energy directly with one another for to maintain homeostasis and that leaves less energy for growth and food.  Infer What would reproduction. Individuals may survive and reproduce under slightly happen if two of the warbler stressful conditions, but they will typically produce fewer offspring, species tried to occupy the and fewer of those offspring survive. In more stressful conditions that same niche in the same tree at are beyond a species’ tolerance limits, individuals may survive but Feeding height (m) Bay-Breasted Warbler the same time? 6 not reproduce. Without reproducing, the species can’t survive.

 READING CHECK Infer What are the possible consequences to an organism when the temperature becomes colder than the optimum range for a species?

0 Yellow-Rumped Warbler

176 Chapter 6 Communities and Ecosystem Dynamics 6.1 Habitats, Niches, and Species Interactions 177 8 BUILD VOCABULARY Microbiomes The discovery of microbial communities called The Niche The habitat of a species, or its ecological address, only READING TOOL Prefixes The prefix micro- microbiomes has dramatically changed our understanding of ecology. tells part of its story. Ecologists also study a species’ ecological occu- Make a concept map means “small” or “minute.” These communities inhabit places never before considered “habi- pation, or how it stays alive. A niche (nich) describes where an organ- to help understand an Microbiomes may be smaller tats,” and perform more important functions than anyone imagined. ism lives and what it does “for a living,” including they way it interacts organism’s niche. Use than what you can see with the For example, in addition to decomposing organic matter, soil micro- with biotic and abiotic factors. A species’ niche includes the range the terms abiotic, biotic, naked eye. biomes, like the ones shown in Figure 6-1, also affect plant health, of physical and biological conditions in which it can survive and ecological address, food, and the ability of roots to absorb water and nutrients. Some members reproduce, as well as the way it obtains resources it needs. habitat, light, niche, of the microbiome transfer carbon from plants to fungi, and from one reproduction, resources, plant to another. Others carry “messages“ between plants. Many Resources and the Niche The term resource can refer to any temperature, and water. ecological interactions, including several discussed in this chapter, are necessity of life. For plants, necessary resources include sunlight, regulated by microbiomes. Even your mouth, gut, and skin are home water, and soil nutrients. For animals, resources can include nesting to microbiomes whose inhabitants outnumber your own cells and space, shelter, types of food, and places to feed. powerfully influence your health! Physical Aspects of the Niche A species’ niche includes all the Tolerance Every species has its own range of tolerance, the physical, or abiotic, factors to which it is adapted. Most amphibians, variety of environmental conditions within which it can survive and for example, absorb and lose water through their skin, so they must reproduce, as shown in Figure 6-2. Within a species’ optimum range, live in moist places. If an area is too hot and dry for too long, most environmental conditions enable individuals to find enough energy amphibians cannot survive. In contrast, plants such as cacti, which and nutrients to maintain homeostasis, to grow and reproduce. are adapted to deserts will die if their roots stay wet for too long.

 READING CHECK Infer What are the possible consequences to an organism when the temperature becomes colder than the optimum range for a species?

0 Yellow-Rumped Warbler

176 Chapter 6 Communities and Ecosystem Dynamics 6.1 Habitats, Niches, and Species Interactions 177 9 Competition Predation and Herbivory If you look at any community, you will probably find more than Recall that food webs involve numerous producers and many consum- one kind of organism attempting to use the same resources. When ers on several trophic levels. The lynx shown in Figure 6-5 will feed more than one organism attempts to use the same limited eco- on the snowshoe hare—if it catches it. However, organisms interact in logical resource in the same place at the same time, competition ways that are much more dynamic than you might guess from looking occurs. In a forest, for example, plant roots compete for water and at food web diagrams. Remember also that populations of preda- nutrients in the soil. Animals compete for resources such as food, tors and prey, and of herbivores and plants, powerfully influence each mates, and places to live and raise their young. Competition among other, and often cycle up and down over time. We review these inter- members of the same species is known as intraspecific competition. actions because they are important in shaping communities. Any natu- Competition between members of different species is known as ral or human-caused environmental change that affects a population of interspecific competition. a key species can dramatically change the structure of an ecosystem. Figure 6-5

Competitive Exclusion Competitive Exclusion Principle Direct competi- Predator-Prey Relationships In lesson 5.2, you learned Predator and Prey tion between species almost always produces a winner and a about predator-prey cycles, and the ways those populations affect Hares are the main prey of lynx. P. aurelia together loser—and the losing species dies out. One series of experi- each other. Now suppose that predators catch prey more easily in alone ments demonstrated this using two species of single-celled some parts of a habitat than in other parts. Over time, those preda-  Infer How do the popula- together tions of predator and prey affect organisms. The results of the experiment are summarized in tors can affect where prey spend most of their time. For example, if P. caudatum alone each other? the graph in Figure 6-4. When each species was grown in a wolves catch elk more often in open space, elk might spend more separate culture under the same conditions, each success- time hiding in the woods! fully survived. But when both species were grown together  INTERACTIVITY in the same culture, one species outcompeted the other. Herbivore-Plant Relationships Herbivores and plants have The less competitive species did not survive. the same sort of relationship as predators and prey—except that Analyze the population plants can’t move! Herbivores affect the size and distribution of dynamics in a coral reef Experiments like this one, along with observations in environment.

Population Density by Volume Measured plant populations in a community, and determine the places that nature, led to the recognition of an important ecological rule. 0 2 4 6 8 10 12 14 16 18 certain plants can survive and grow. For example, if elk spend a The competitive exclusion principle states that no two spe- Time (days) lot of time grazing in certain areas, they almost wipe out local willow cies can occupy exactly the same niche in exactly the same populations in those areas. habitat at exactly the same time. If two species attempt to Figure 6-4 do so, one species will be better at competing for limited HS-LS2-2 Competitive Exclusion resources and will eventually exclude the other species. CASE STUDY Analyzing Data The two species of paramecia P. aurelia Dividing Resources The competitive exclusion prin- Predator-Prey Dynamics and P. caudatum have similar require- ciple explains the observation that we rarely find more than ments. When grown in cultures sepa- Predator-Prey Dynamics Predator Prey rately (dashed lines), both populations one species in a habitat occupying exactly the same niche. The relationships between predator and prey That happens because competition for resources cre- are often tightly intertwined, particularly in an grow quickly and then level off. When A B C DE grown together under certain condi- ates pressure for each species to specialize the way that it environment in which each prey species has a tions (solid lines), however, P. aurelia obtains and uses resources. By causing species to divide single predator and vice versa. The graph here outcompetes P. caudatum and drives resources, competition helps determine the numbers and shows an idealized computer model of changes in predator and prey populations over time. it to extinction. kinds of species in a community and the niche each species occupies. 1. Use Computational Models Suppose a bacterial infection kills off most of the prey F

For instance, the three species of North American warblers shown at point B on the graph. Predict how this Population Size in Figure 6-3 all live in the same trees and feed on insects. But one would affect the predator and prey growth Time species feeds on high branches, another feeds on low branches, and curves on this computer model at point C? At point D? another feeds in the middle. The resources used by these species are 3. Develop Possible Solutions Suppose a viral similar, but not identical. Therefore, each species has its own niche. 2. Analyze Graphs Suppose a sudden infection kills all the prey at point D. What extended cold spell destroys almost the effect would this have on the predator and prey This division of resources was likely brought about by competition entire predator population at point F curves at point E? What will happen in future among the birds. on the graph. Predict how the next cycle years to the predator population? What solution of the prey population would appear on could ecologists develop to ensure the contin-  READING CHECK Predict What would happen if two species the graph? ued survival of the predators? occupy the same niche at the same time?

178 Chapter 6 Communities and Ecosystem Dynamics 6.1 Habitats, Niches, and Species Interactions 179 10 Competition Predation and Herbivory If you look at any community, you will probably find more than Recall that food webs involve numerous producers and many consum- one kind of organism attempting to use the same resources. When ers on several trophic levels. The lynx shown in Figure 6-5 will feed more than one organism attempts to use the same limited eco- on the snowshoe hare—if it catches it. However, organisms interact in logical resource in the same place at the same time, competition ways that are much more dynamic than you might guess from looking occurs. In a forest, for example, plant roots compete for water and at food web diagrams. Remember also that populations of preda- nutrients in the soil. Animals compete for resources such as food, tors and prey, and of herbivores and plants, powerfully influence each mates, and places to live and raise their young. Competition among other, and often cycle up and down over time. We review these inter- members of the same species is known as intraspecific competition. actions because they are important in shaping communities. Any natu- Competition between members of different species is known as ral or human-caused environmental change that affects a population of interspecific competition. a key species can dramatically change the structure of an ecosystem. Figure 6-5

178 Chapter 6 Communities and Ecosystem Dynamics 6.1 Habitats, Niches, and Species Interactions 179 11 READING TOOL Keystone Species Symbioses Read actively! Look for Sometimes, a single species has such a powerful influence on com- A particularly close, interdependent relationship between two in-text definitions of munity structure that changes in its population size can dramati- species is called symbiosis (sim by oh sis), which means “living any unfamiliar terms or cally change the structure of an entire ecosystem. As described in together.“ Three main types of symbiotic relationships are concepts. Figure 6-6, sea otters along the Pacific coast of North America are a mutualism, commensalism, and parasitism. prime example. Along much of that coast, giant algae called kelp can grow abundantly, creating complex ecosystems called kelp forests. Commensalism A relationship in which one organism benefits Kelp’s main “enemies” are herbivorous sea urchins. When this commu- and the other is neither helped nor harmed is called commensalism nity is in balance, sea otters eat enough urchins to control their popu- (kuh men sul iz um). For example, small marine animals called bar- lation, and kelp grow thickly. nacles often attach themselves to whales. The barnacles benefit from  INTERACTIVITY the movement of water full of food particles past their swimming A century ago, otters were nearly eliminated across much of their CASE STUDY hosts. Although barnacles perform no known service to whales, they Figure 6-7 range by hunting. Soon, kelp forests up and down the coast vanished. don’t harm them either. Many members of microbiomes have com- Visual Analogy What had happened? Without otters preying on sea urchins, urchin Symbiosis mensal relationships with each other and with larger organisms. Figure 6-6 populations skyrocketed. Armies of urchins devoured kelp. Without kelp forests as habitat, fishes, seabirds, and many other species disappeared. Mutualism is one type of symbi- Keystone Species Mutualism A relationship between two species in which both osis. Clownfish living among the In this community, otters function as what is called a species benefit is called mutualism. Sea anemones, for example, sea anemone tentacles are pro- A keystone is the stone at keystone species. A keystone species plays a vital and unique use stinging tentacles to protect themselves from predators and to tected from predators and the the top of an arch that holds role in maintaining structure, stability, and diversity in an ecosytem. capture prey. Despite those weapons, certain fishes still manage to clownfish chase away predators the the other stones in place. When otters were protected from hunting, their populations recov- snack on anemone tentacles. Some anemone species, however, have of the sea anemone. Recently, Similarly, a keystone species ered. Urchin populations dropped, and kelp forests began to thrive mutualistic partners called clownfishes, which are immune to anem- scientists have discovered that provides structure and stability anemones with clownfish part- again. But there are other species in that ecosystem. Recently, otter one stings. When a clownfish is threatened by a fish-eating predator, to an ecosystem. Sea otters ners are healthier. The move- are a keystone species in the populations have fallen again, possibly because of increased predation it seeks shelter by snuggling deep into tentacles that would kill or ment of the fish through the Pacific coast of North America. by killer whales. Note that once an ecosystem has been changed by paralyze most other fish, as shown in Figure 6-7. But if an anemone- anemone’s tentacles improves

s e s u a C n a m u H See the Understanding Global removal of a keystone species, it may or may not be possible to restore eating species tries to attack their living home, the spunky clownfish water circulation.

s Non-Human Cause Change diagram (p. 207) to learn how species interactions the original community by simply putting the keystone species back. dart out and fiercely chase away fish many times their size. Mutualism are affected by global change. is also very common in microbiomes, including both soil and human microbiomes. Many members of human gut microbiota, for example, help keep disease-causing microorganisms under control through competition and other interactions.  INTERACTIVITY

Parasitism A relationship in which one organism lives inside or Analyze the types of symbi- on another organism and harms it is called parasitism. The parasite otic relationships. obtains all or part of its nutritional needs from the host organism. Generally, parasites weaken but do not kill their host. Tapeworms, for example, live in the intestines of mammals, where they absorb large amounts of their hosts’ partially-digested food. Fleas, ticks, lice, and leeches live on the skin or hair of many animals. HS-LS2-2  LESSON 6.1 Review

KEY QUESTIONS CRITICAL THINKING 1. How can you describe the environment in which 5. Evaluate Claims In a forest ecosystem, both an organism lives? owls and hawks prey on small, ground-dwelling animals. A student claims that because the two 2. Explain why no two species can occupy the same birds prey on the same animals, they occupy the niche at the same time. same niche. Evaluate this claim, and include an 3. Why are predator-prey and herbivore-plant explanation to either support or refute it. relationships important in shaping communities? 6. Evaluate Models How is the model of a very small 4. List and describe the three main types of biome, or microbiome, useful for studying the symbiotic relationships. habitats of bacteria and other microorganisms?

180 Chapter 6 Communities and Ecosystem Dynamics 6.1 Habitats, Niches, and Species Interactions 181 12 READING TOOL Keystone Species Symbioses Read actively! Look for Sometimes, a single species has such a powerful influence on com- A particularly close, interdependent relationship between two in-text definitions of munity structure that changes in its population size can dramati- species is called symbiosis (sim by oh sis), which means “living any unfamiliar terms or cally change the structure of an entire ecosystem. As described in together.“ Three main types of symbiotic relationships are concepts. Figure 6-6, sea otters along the Pacific coast of North America are a mutualism, commensalism, and parasitism. prime example. Along much of that coast, giant algae called kelp can grow abundantly, creating complex ecosystems called kelp forests. Commensalism A relationship in which one organism benefits Kelp’s main “enemies” are herbivorous sea urchins. When this commu- and the other is neither helped nor harmed is called commensalism nity is in balance, sea otters eat enough urchins to control their popu- (kuh men sul iz um). For example, small marine animals called bar- lation, and kelp grow thickly. nacles often attach themselves to whales. The barnacles benefit from  INTERACTIVITY the movement of water full of food particles past their swimming A century ago, otters were nearly eliminated across much of their CASE STUDY hosts. Although barnacles perform no known service to whales, they Figure 6-7 range by hunting. Soon, kelp forests up and down the coast vanished. don’t harm them either. Many members of microbiomes have com- Visual Analogy What had happened? Without otters preying on sea urchins, urchin Symbiosis mensal relationships with each other and with larger organisms. Figure 6-6 populations skyrocketed. Armies of urchins devoured kelp. Without kelp forests as habitat, fishes, seabirds, and many other species disappeared. Mutualism is one type of symbi- Keystone Species Mutualism A relationship between two species in which both osis. Clownfish living among the In this community, otters function as what is called a species benefit is called mutualism. Sea anemones, for example, sea anemone tentacles are pro- A keystone is the stone at keystone species. A keystone species plays a vital and unique use stinging tentacles to protect themselves from predators and to tected from predators and the the top of an arch that holds role in maintaining structure, stability, and diversity in an ecosytem. capture prey. Despite those weapons, certain fishes still manage to clownfish chase away predators the the other stones in place. When otters were protected from hunting, their populations recov- snack on anemone tentacles. Some anemone species, however, have of the sea anemone. Recently, Similarly, a keystone species ered. Urchin populations dropped, and kelp forests began to thrive mutualistic partners called clownfishes, which are immune to anem- scientists have discovered that provides structure and stability anemones with clownfish part- again. But there are other species in that ecosystem. Recently, otter one stings. When a clownfish is threatened by a fish-eating predator, to an ecosystem. Sea otters ners are healthier. The move- are a keystone species in the populations have fallen again, possibly because of increased predation it seeks shelter by snuggling deep into tentacles that would kill or ment of the fish through the Pacific coast of North America. by killer whales. Note that once an ecosystem has been changed by paralyze most other fish, as shown in Figure 6-7. But if an anemone- anemone’s tentacles improves

180 Chapter 6 Communities and Ecosystem Dynamics 6.1 Habitats, Niches, and Species Interactions 181 13 In ecological succession, pioneer species have broad ranges of BUILD VOCABULARY tolerance for environmental factors. That’s how they manage to survive Word Origins The origin of Succession on bare rock, or in soil that lacks nutrients and a mature microbiome. the word succession is the

LESSON One ecological pioneer that grows on bare rock is lichen—a sym- Latin word succedre, meaning 6.2 “to come after.” Ecological biosis between a multicellular fungus, a yeast, and a photosynthetic succession involves changes organism. Mosses and certain grasses, like those that first colonized that occur one after the other on Krakatau, are also pioneer species. Pioneer species break down as species move into and out KEY QUESTIONS rock, synthesize organic material, and begin to form soil. of a community. • How do communities change over time? Secondary Succession When a disturbance affects an • How do communities existing community but doesn’t completely destroy it, a process of recover after a secondary succession occurs. Secondary succession proceeds faster disturbance? than primary succession, in part because bits of the old community  INTERACTIVITY survive and can regrow rapidly. Secondary succession is shown in Figure 6-8B. On land, secondary succession often follows a wildfire, Figure 6-8 hurricane, or other natural disturbance. We think of these events as Primary and HS-LS2-2: Use mathematical disasters, but many species are adapted to them. Although forest Secondary Succession representations to support and revise explanations based on evidence about fires kill some trees, for example, other trees are spared, and fire can factors affecting biodiversity and stimulate their seeds to germinate. Secondary succession can also In both types of succession, populations in ecosystems of different one group of species replaces scales. follow human activities like logging and farming. HS-LS2-6: Evaluate the claims, evidence, In 1883, the volcanic island of Krakatau in the Indian Ocean was another group. and reasoning that the complex interactions in ecosystems maintain destroyed by an eruption. The tiny island that remained was com- relatively consistent numbers and types pletely barren. Within two years, however, grasses were growing. of organisms in stable conditions, but changing conditions may result in a new Fourteen years later, there were 49 plant species, along with lizards, ecosystem. HS-LS2-7: Design, evaluate, and refine birds, bats, and insects. By 1929, a forest containing 300 plant spe- a solution for reducing the impacts of cies had grown. Today, the island is blanketed by mature rain forest. human activities on the environment and biodiversity. What events and processes changed the island’s populations and species diversity so dramatically? VOCABULARY ecological succession Primary and Secondary Succession primary succession The story of Krakatau after the eruption is just one example of pioneer species ecological succession, a series of somewhat predictable events that secondary succession Time occur in a community over time. Ecosystems change over time, 15 years 35 years 80 years 115+ years especially after disturbances, as new species move in, populations READING TOOL A. Primary succession occurs on newly exposed surfaces. In Glacier Bay, change, and some species die out. As the history of Krakatau shows, Alaska, a retreating glacier exposed barren rock. Over the course of Identify the sequence species diversity typically increases over the course of succession. 100 years, a series of changes has led to the hemlock and spruce forest. of events that occur in both types of succession, Primary Succession Volcanic explosions such as the ones and record them in the that destroyed Krakatau and blew the top off Mount Saint Helens graphic organizer in your in Washington State a century later, can create new land or sterilize Biology Foundations existing areas. Retreating glaciers can have the same effect, leav- Workbook. ing only exposed bare rock behind them. Succession that begins on newly formed rock or other areas that have no remnants of an older community is called primary succession, as shown in Figure 6-8A. Pioneer species are the first species to colonize barren areas. The term is named after rugged human pioneers who first settle wilderness areas. Human pioneers create the first settlements, and do Time the ground breaking work that makes an area habitable for subse- 3 years 5 years 40+ years quent settlers. B. Secondary succession occurs in disturbed areas where remnants of previous ecosystems remain. In both examples, changes will continue for years to come.

182 Chapter 6 Communities and Ecosystem Dynamics 6.2 Succession 183 14 In ecological succession, pioneer species have broad ranges of BUILD VOCABULARY tolerance for environmental factors. That’s how they manage to survive Word Origins The origin of Succession on bare rock, or in soil that lacks nutrients and a mature microbiome. the word succession is the

182 Chapter 6 Communities and Ecosystem Dynamics 6.2 Succession 183 15 HS-LS2-6 Why Succession Happens Succession Figure 6-9 can happen in different environments for sev- Recovery From  Guided Inquiry Quick Lab eral reasons. In most cases, each species alters a Natural Disaster its environment in ways that make it easier for How Does Succession Occur? other species to compete for resources and These photos show the coastline Procedure survive. For example, as lichens add organic of Banda Aceh, Indonesia, imme- diately following a tsunami in 1. Place a handful of dried plant material into matter and form soil, mosses and other small December, 2004 (left), and then a clean jar. plants can colonize and grow. When trees again in December, 2014 (right). arrive, their branches and leaves shade and 2. Fill the jar with boiled pond water (that has  Interpret Photos What kind cooled) or sterile spring water. Determine the protect the ground, and provide shelter and of succession occurred in this initial pH of the water with pH paper. food for animals. These processes increase the region? How do you know?

s e s u a C n a m u 3. Cover the jar and place it in an area that complexity of the environment, enabling more H See the Understanding Global

s receives indirect light. plant and animal species to find homes and Non-Human Cause Change diagram (p. 207) to learn how natural disasters affect global 4. Examine the jar every day for the next few days. food. As succession continues, species diversity Succession After Human-Caused Disturbances In North change. 5. When the water in the jar appears cloudy, usually increases. America, land cleared for farming and then abandoned often passes prepare microscope slides of water from various through succession that eventually produces a community that may levels of the jar. Use a pipette to collect the  READING CHECK Apply Concepts or may not resemble the original climax community. Ecosystems samples. How is primary succession different from may or may not recover from extensive human-caused disturbances. 6. Look at the slides under the low-power secondary succession? Secondary succession can take different paths, and produce objective lens of a microscope and record different communities, depending on the kind of disturbance, your observations. Climax Communities the season in which the disturbance occurs, and other factors. ANALYZE AND INTERPRET DATA Years ago, ecologists thought that succession in Clearing and farming of tropical rain forests, for example, can 1. Evaluate Your Plan Why did you use boiled a given area would always proceed through the change the physical structure of soil and the soil microbiome in ways or sterile water in this investigation? same stages to produce a specific, uniform, and that prevent regrowth of the original community. 2. Draw Conclusions Where did the organisms stable climax community like the spruce/hem- you observe come from? lock forest developing in Glacier Bay. But recent Studying Patterns of Succession Ecologists study succes-  INTERACTIVITY 3. Support Your Explanation with Evidence studies have shown that succession doesn’t sion by comparing different cases and looking for similarities and differences. For example, they learned that at both Mount Saint Helens Was ecological succession occurring? Cite always follow the same path, and that climax Simulate succession in a for- evidence from this investigation communities are often not uniform and stable. and Krakatau, primary succession proceeded through stages. Pioneer est ecosystem. to support your answer. species arrived via seeds, spores, or adult stages that traveled over 4. Evaluate Evidence Succession After Natural long distances. Check your results Disturbances Many communities regularly The pioneer species are important because they help stabilize loose against those of your classmates. experience natural events that disturb patches volcanic debris. This allowed later species to take hold. Historical studies Do they agree? of varying sizes. Healthy temperate forests and in Krakatau and ongoing studies on Mount Saint Helens confirm that How do you grasslands recover from wildfires. The photos early stages of primary succession are slow, and that chance can play a explain any in Figure 6-9 show how a shoreline in Indonesia large role in determining which species colonize at different times. differences? recovered from a tsunami. When natural HS-LS2-2, HS-LS2-6, HS-LS2-7 disturbances happen in healthy ecosystems, the events and processes that occur during  LESSON 6.2 Review secondary succession often, but not always, reproduce the origi- 4. Define the Problem After taking antibiotics for nal climax community. Powerful waves during storms can damage KEY QUESTIONS several weeks, a patient develops a severe bacte- 1. Explain why ecological succession occurs. portions of a coral reef. Windstorms can knock over rain forest trees, rial infection in his intestines. The doctor claims creating sunny breaks in the canopy. Fires can kill trees in parts of a 2. Describe the factors that affect the paths of the antibiotics changed the microbiome of the forest. Once the disturbance is over, each of these patches under- secondary succession? patient’s gut, causing the infection to develop. goes succession. So different patches within the larger community CRITICAL THINKING What evidence would the doctor need to support may be in a different stage of secondary succession at the same the claim. Explain how competition and succession  INTERACTIVITY 3. Construct an Explanation Provide evidence played a role in developing the bacterial infection. time. Some climax communities are disturbed so often that they look to support the claim that secondary succession 5. Synthesize Information A section of tropical rain Compare the types of like ecological “patchwork quilts” and can’t really be called either tends to occur faster than primary succession. forest is cleared for a farm. Why might the forest succession. uniform or stable. community never return in its original form, even if the farm is abandoned?

184 Chapter 6 Communities and Ecosystem Dynamics 6.2 Succession 185 16 HS-LS2-6 Why Succession Happens Succession Figure 6-9 can happen in different environments for sev- Recovery From  Guided Inquiry Quick Lab eral reasons. In most cases, each species alters a Natural Disaster its environment in ways that make it easier for How Does Succession Occur? other species to compete for resources and These photos show the coastline Procedure survive. For example, as lichens add organic of Banda Aceh, Indonesia, imme- diately following a tsunami in 1. Place a handful of dried plant material into matter and form soil, mosses and other small December, 2004 (left), and then a clean jar. plants can colonize and grow. When trees again in December, 2014 (right). arrive, their branches and leaves shade and 2. Fill the jar with boiled pond water (that has  Interpret Photos What kind cooled) or sterile spring water. Determine the protect the ground, and provide shelter and of succession occurred in this initial pH of the water with pH paper. food for animals. These processes increase the region? How do you know?

s e s u a C n a m u 3. Cover the jar and place it in an area that complexity of the environment, enabling more H See the Understanding Global

184 Chapter 6 Communities and Ecosystem Dynamics 6.2 Succession 185 17 Biodiversity Benefits Biodiversity, Ecosystems, You might not think of biodiversity as a natural resource, but it is a great treasure. Biodiversity’s benefits include offering invalu- LESSON 6.3 and Resilience able contributions to medicine and agriculture, and enabling organisms and ecosystems to adapt to environmental change.

Biodiversity and Medicine Many medicines, including pain- KEY QUESTIONS killers like aspirin and antibiotics like penicillin, were first discovered • What kinds of in wild species. Other plant compounds from wild species are used biodiversity exist? to treat diseases like depression and cancer. • What are the benefits of biodiversity? Most crop plants have wild Biodiversity and Agriculture Figure 6-10 • What are some relatives, like the potatoes in Figure 6-10. These wild plants may important ecosystem Potato Diversity services? carry genes that promote disease resistance, pest resistance, or other useful traits. These genes could be transferred to crop plants The genetic diversity of wild through plant breeding or genetic engineering. potatoes in South America can HS-LS2-6: Evaluate the claims, evidence, and reasoning that the complex be seen in the colorful varieties interactions in ecosystems maintain Biodiversity and Ecosystem Resilience The biological shown here. The International relatively consistent numbers and types of organisms in stable conditions, but diversity of an ecosystem can affect that ecosystem’s structure, stabil- Potato Center, based in Peru, changing conditions may result in a houses a “library” of more new ecosystem. From multicolored coral reefs to moss-draped forests, variety is “the ity, and function. Recall that the presence of a keystone species can HS-LS2-7: Design, evaluate, and refine increase community biodiversity. The removal of a keystone species than 4500 tuber varieties. a solution for reducing the impacts of spice of life.” But variety in the biosphere gives us more than inter- human activities on the environment and esting things to look at. Our well-being is closely tied to the health can decrease biodiversity and stability. biodiversity. HS-LS4-6: Create or revise a simulation of ecosystems, which in turn depends on community interactions In addition, several ecological models suggest that a decrease in BUILD VOCABULARY to test a solution to mitigate adverse among different organisms. an ecosystem’s species diversity can affect its resilience. Resilience impacts of human activity on biodiversity. Related Words The noun describes a natural or human system’s ability to recover after a resilience is the ability to VOCABULARY Types of Biodiversity disturbance. Resilient ecosystems also have some ability to adapt recover after a change. The biodiversity Biological diversity, or biodiversity, is the total of all genetically- over time to changes in their surroundings. How could biodiversity fit adjective resilient describes ecosystem diversity based variation in all organisms in the biosphere. Biodiversity can into a resilience model? The more species present in an ecosystem, something that is able to species diversity be defined as the variety and variability of animals, plants, and the more likely that some of those species have different tolerance adjust easily to change. genetic diversity microorganisms, including ecosystem diversity, species diversity, ranges for environmental conditions, such as temperature and rain- resilience and genetic diversity. fall. And if that is the case, populations of those species can rise and ecosystem services fall under different conditions, as modeled in Figure 6-11. Community/Ecosystem Biodiversity Ecosystem diversity READING TOOL refers to the variety of habitats, communities, and ecological Average Year Wet Year Dry Year Complete the chart in your processes in the biosphere. Visual Analogy Biology Foundations Diverse Ecosystem Figure 6-11 Workbook to record the Species Diversity The number of different species in the bio- main ideas and supporting sphere, or in a particular area, is called species diversity. To date, Resilience to Climate details of the lesson. biologists have identified and named more than 1.2 million eukary- Ecosystem In this model, the “red” species better toler- otic species, and they estimate that at least 9 million more are yet dominated by “red” species ate wet weather, while the “yellow” species to be discovered—and that estimate doesn’t include microbiomes! better tolerate dry weather. Ecosystems Much more diversity exists among single-celled organisms. containing just one of those species change Ecosystem more dramatically than an ecosystem con- dominated by Genetic Diversity The term genetic diversity usually refers to “gold” species taining both species.  Use Models What  INTERACTIVITY the total of all different forms of genes present in a particular spe- does this model suggest about biodiversity and ecosystem resilience? Learn about and explore cies. Genetic diversity can be invisible, but is responsible for within- Time biodiversity in different species variations among organisms, both in individual ecosystems Adapted from: Cleland, E. E. (2011) Biodiversity and Ecosystem Stability. ecosystems. and among different ecosystems. Genetic diversity is the raw mate- Nature Education Knowledge 3(10):14. rial that enables organisms to adapt to changing external factors.

186 Chapter 6 Communities and Ecosystem Dynamics 6.3 Biodiversity, Ecosystems, and Resilience 187 18 Biodiversity Benefits Biodiversity, Ecosystems, You might not think of biodiversity as a natural resource, but it is a great treasure. Biodiversity’s benefits include offering invalu- LESSON 6.3 and Resilience able contributions to medicine and agriculture, and enabling organisms and ecosystems to adapt to environmental change.

186 Chapter 6 Communities and Ecosystem Dynamics 6.3 Biodiversity, Ecosystems, and Resilience 187 19 HS-LS2-6 Services Provided and Examples  INTERACTIVITY  In Your Neighborhood Guided Inquiry Purifying water Figure 6-12 Biodiversity on the Forest Floor Wetlands and intact forests along rivers and around Ecosystem Services reservoirs filter and clean groundwater. Preserving buffer Problem How does biodiversity help leaves decompose? zones that perform these natural processes is significantly Healthy ecosystems provide In this lab, you will investigate the microorganisms that cheaper than building water-purification plants. many benefits to human break apart dead leaves on the forest floor, and evaluate their role in maintaining a healthy forest ecosystem. Buffering effects of weather society. The benefits are called ecosystem services. Mangrove forests protect tropical shorelines from

s e s u You can find this lab in your digital course. a C n a m u erosion by storm waves and runoff. Dune grasses and H See the Understanding Global

s Non-Human Cause Change diagram (p. 207) to salt marsh grasses do the same in temperate regions. learn how ecosystem services are affected by global change. READING TOOL Ecosystem Services and Biodiversity Pollinating Use the key idea sentence Human society depends on healthy ecosystems in a number of ways, Bees, flies, and butterflies pollinate crop plants, to help you predict the although many people don’t think much about that dependence. including fruit trees and vegetables. Beetles, bats and hummingbirds pollinate many other important plants. information that follows it. Ecosystem services are the benefits provided by ecosystems to humans as shown in Figure 6-12. Important ecosystem services include production of food, cycling of nutrients, purifying water, Regulating pests storing carbon, regulating pests, pollinating crops, and buffering Many species of birds and bats eat insects like mosquitoes that can spread disease. These and the effects of extreme weather events. other predators also eat crop-damaging insects.

Food Production Diverse ecosystems, such as prairies, can pro-  VIDEO vide a resilient mix of food for livestock. Wild species can preserve Food production genes that may improve related crops or livestock. Highly productive ocean areas provide large fishes, Learn how a loss of genetic such as tuna, with food and space to thrive. Many diversity in potatoes caused wild plants may also produce food for humans. famine in Ireland. Nutrient Cycling and Soil Structure Both carbon and nitrogen cycles depend, in part, on the activities of the soil microbiome. Nutrient cycling A resilient soil microbiome helps maintain soil fertility and structure Healthy, actively growing forests remove carbon dioxide under changing conditions. from the atmosphere. Bacteria and fungi also take up nitrogen and fix it into organic compounds. Purifying Water Soil microbiomes, along with algae and plants, play vital roles in filtering and purifying fresh water. Maintaining soil structure Healthy and actively growing terrestrial and Detritivores and other soil organisms aerate soil and prevent Storing Carbon it from becoming too compacted. Bacteria and fungi in soil marine ecosystems with high primary productivity remove carbon as well as leaf litter microbiomes produce humus. dioxide from the atmosphere and store it. Biodiverse ecosystems are generally more resilient and can provide this function under a wider range of environmental conditions. HS-LS2-6, HS-LS2-7, HS-LS4-6  Regulating Pests and Pollinating Crops Biologically diverse LESSON 6.3 Review and resilient ecosystems include predators that feed on herbivores KEY QUESTIONS 5. Construct an Argument A farmer decides to that might attack crop plants. Diverse terrestrial ecosystems offer use a pesticide on a cherry orchard. The pesti- 1. Describe three different types of biodiversity. food and shelter to vital pollinating insects. cide would kill nearly all insects, including those 2. Explain how biodiversity benefits medicine and that feed on cherries. Construct arguments both Buffering Effects of Extreme Weather Events Diverse and agriculture. in support of and against the farmer’s decision. resilient coastal wetlands protect against erosion and shield shore- 3. Explain how biodiversity affects ecosystem services. Research the use of pesticides in orchards to help you construct the arguments. lines against storms. Forests can protect mountainsides against CRITICAL THINKING erosion and landslides. 4. CASE STUDY Apply Scientific Reasoning Why does the biodiversity of an ecosystem affect its  READING CHECK Review How does biodiversity improve resilience? the resilience of an ecosystem?

188 Chapter 6 Communities and Ecosystem Dynamics 6.3 Biodiversity, Ecosystems, and Resilience 189 20 HS-LS2-6 Services Provided and Examples  INTERACTIVITY  In Your Neighborhood Guided Inquiry Purifying water Figure 6-12 Biodiversity on the Forest Floor Wetlands and intact forests along rivers and around Ecosystem Services reservoirs filter and clean groundwater. Preserving buffer Problem How does biodiversity help leaves decompose? zones that perform these natural processes is significantly Healthy ecosystems provide In this lab, you will investigate the microorganisms that cheaper than building water-purification plants. many benefits to human break apart dead leaves on the forest floor, and evaluate their role in maintaining a healthy forest ecosystem. Buffering effects of weather society. The benefits are called ecosystem services. Mangrove forests protect tropical shorelines from

s e s u You can find this lab in your digital course. a C n a m u erosion by storm waves and runoff. Dune grasses and H See the Understanding Global

188 Chapter 6 Communities and Ecosystem Dynamics 6.3 Biodiversity, Ecosystems, and Resilience 189 21 CASE STUDY WRAP-UP

Technology on the Case Follow that Wolf! How can researchers figure out where wolves spend their time? And how can rangers track wolves in a park as vast as Yellowstone? Technology provides the answers. Data about which animals live in certain places How do species interactions can be gathered by hidden cameras. If animals are active at night, infra-red light and special sen- sors allow pictures to be taken in the dark. shape ecosystems? Researchers also attach tracking devices onto animals. Some tracking devices are simple radio transmitters. Researchers locate these animals In some places, wolf populations are small and endangered. Careers on the Case using receivers equipped with directional anten- nae to home in on the signal. Other devices Yellowstone’s wolf packs are healthy—for now. Work Toward a Solution use satellite-based global positioning systems HS-ETS1-3, HS-ESS3-4, CCSS.ELA-LITERACY.WHST.9-10.1.B National parks help preserve biodiversity, and (GPS)—the same sort of technology used in cars they can provide useful evidence about the way and smart phones. Make Your Case ecosystems function. Park rangers work with sci- These devices must withstand outdoor condi- Scientists and park rangers agree that reintroducing wolves to entists and government officials to help manage tions, and should not interfere with subjects’ Yellowstone was a well-informed decision. Happily, the wolves these parks. natural behavior. Devices used to track ele- helped reverse many of the changes in parts of Yellowstone, restor- phants must stand up to being rubbed against ing biodiversity in certain areas. However, wolves weren’t the only Park Ranger tree trunks! Migratory birds can be tracked using cause of the improvements, and wolf reintroduction didn’t restore The U.S. National Park System much smaller and more lightweight devices. Still all areas. covers more than 84 million other tracking tools are so tiny and light that acres. Rangers help educate they can be carried by bumblebees! Apply Scientific Reasoning visitors, protect park land and In Yellowstone, scientists have been plac- wildlife, and enforce laws. Many 1. Conduct Research Compare the Yellowstone wolf story with a situ- ing radio collars on 25 to 30 wolves every year. rangers are experts in specific ation in your region where human activity that affected one species, These collars enable researchers to gather data or a couple of species, resulted in a trophic cascade. Which aspects fields of science, such as for- on the sizes of wolf home ranges, and how their are similar to the Yellowstone story, and which are different? Have estry, geology, and wildlife management. researchers offered and tested hypotheses to explain the changes? movements change from one season to another. Sometimes, a collar will reveal bad news about 2. Engage in Argument Develop an argument, supported by evidence, the individual wearing it. When the signal about ways to protect or restore the ecosystem that you researched.  VIDEO Do you think your solution will work throughout the ecosystem, or comes from the same place for several days, the just in certain parts of it? Compare and contrast your chosen system Learn more about park rangers and tagged animal has probably died. with Yellowstone. other related careers.

190 Chapter 6 Communities and Ecosystem Dynamics Case Study Wrap-Up 191 22 CASE STUDY WRAP-UP

190 Chapter 6 Communities and Ecosystem Dynamics Case Study Wrap-Up 191 23 CHAPTER 6 STUDY GUIDE

Lesson Review Go to your Biology Foundations Workbook for longer versions of these lesson summaries. Fishing and Freshwater Population Agricultural Deforestation/ Habitat loss/ Invasive hunting use growth activities reforestation restoration species Urbanization 6.1 Habitats, Niches, and 6.2 Succession Species Interactions Ecological succession is a series of somewhat predictable changes over time in a community. A habitat refers to the physical and biological envi- GLOBAL ronmental factors of an ecosystem that affect the Primary succession occurs on bare rock, where OF CH C Carbon ES AN organisms living there. Every species in a habitat has there are no remnants of an older community. The US G ARTH SYST E A E E EM its own range of tolerance, which are the environ- first species to colonize a barren area are called C TH WO W RK Fire pioneer species. Secondary succession occurs HO S mental conditions in which it can survive and repro- Climate e B G when some members of the older community t r E i duce. Within a habitat, a species occupies a niche, e e le o lo s g h m s b d p e p s n a e u s m t h l remain. It often occurs after human activities like s B o te a e E H which includes the range of physical and biological s l u y m y BLE CHA C r n s A N y e e u a g t o R G c farming and logging. In both types of succession, r c U l r Wind e m conditions in which it can survive and reproduce. e A E S TH S E g C AR YS S s n A E T y Populations E E E I a E M N B a series of new communities replace older ones. n H l M n T u a a Competition within and among species helps d b C g Clouds m o l e a

u When a natural disturbance occurs in a healthy t G determine the numbers and kinds of species in a u Species ranges

H e e s

g e ecosystem, secondary succession often, but not a WELL

community and the niche each species occupies. n

a s

i l

Precipitation h BEING C Populations of predators and prey, and of herbi- always, reproduces the original climax community. C Species However, secondary succession can also take dif- interactions vores and plants, powerfully influence each other, Temperature and often cycle up and down over time. ferent paths and produce different communities.

Weather/ E s • ecological succession • pioneer species H le m Symbiosis describes the interdependent relation- Extreme Events m te e Food availability y e s r n y d t s e & nutrition • primary succession • secondary succession r a co h ship between two species. In commensalism, one o l C E s y sp p cle o organism benefits and the other is neither helped he s e re Climate G nor harmed. In mutualism, both species benefit. A 6.3 Biodiversity, Ecosystems, parasitic relationship is one in which one organism lives inside or on another organism. and Resilience Soil formation Biodiversity is the total of all genetically-based vari- No es • habitat • keystone species n-h aus & quality ation in all organisms in the biosphere. Biodiversity uman C • tolerance • symbiosis includes ecosystem diversity, species diversity, and • niche • commensalism genetic diversity. Ecosystem diversity refers to the • resource • mutualism Freshwater quality Volcanism variety of habitats, communities, and ecological & availability • competitive exclusion • parasitism processes. Species diversity refers to the number of principle different species. Genetic diversity refers to the total  Use Models Use the Understanding Global Change diagram (p. 207) to discuss ways in which human of all different forms of genes present in a species. activity can affect species interactions, ecosystem structure and function, and biomass. Relate these Biodiversity is one of Earth’s greatest resources. phenomena to key concepts for this chapter, including keystone species, biodiversity, and resilience. Biodiversity contributes to medicine and agriculture and enables organisms and ecosystems to adapt to change. The more diverse an ecosystem is, the higher its resilience to natural and human disturbances. Organize Information Ecosystem services refer to the benefits provided Cite evidence for each statement from the text, investigations, and other to humans by ecosystems. Food production, activities you have completed. cycling of nutrients, water purification, carbon storage, pest regulation, crop pollination, and Statement Evidence buffering effects of extreme weather events are all important ecosystem services. Each species has tolerances for environ- 1. mental factors. • biodiversity • genetic diversity Lichen can act as a pioneer species. 2.  Apply Concepts What role does a keystone • ecosystem diversity • resilience species have in its ecosystem? • species diversity • ecosystem services Biodiversity can be valuable medically. 3.

192 Chapter 6 Communities and Ecosystem Dynamics Study Guide 193 24 CHAPTER 6 STUDY GUIDE

u When a natural disturbance occurs in a healthy t G determine the numbers and kinds of species in a u Species ranges

H e e s

g e ecosystem, secondary succession often, but not a WELL

community and the niche each species occupies. n

a s

i l

192 Chapter 6 Communities and Ecosystem Dynamics Study Guide 193 25 PERFORMANCE-BASED ASSESSMENT ENGINEERING PROJECT The Populations of Yellowstone

Construct a Solution HS-LS2-2, HS-LS2-7, HS-LS4-6

STEM As you have read in this chapter’s 2. Construct an Explanation Using the evidence Wolf Beaver Case Study, wolves were reintro- in the graph, construct an explanation for how 120 duced to Yellowstone National Park in the 1990s. the changes in wolf population might have 120 Ever since, scientists have been monitoring the affected other populations. Support your expla- 80 80 populations of wolves and other species in the nation with your knowledge of factors that affect 40 40 populations, such as competition, predation, 0 Population park. The graphs show some of their data. Population 0 (individuals) and herbivory. 1995 2000 2005 2010 (# of colonies) 1995 2000 2005 2010 Year As you analyze the data, remember that many 3. Identify Variables What factors other than the Year factors affect the Yellowstone ecosystem. Wolves wolf population could explain the trends in the data? Consider biotic factors, such as other spe- prey on elk, but so do other Yellowstone preda- Elk Aspen tors, such as coyotes and bobcats. Elk graze on cies that live in Yellowstone, as well as abiotic 120 a variety of trees that grow in Yellowstone, but factors, such as climate. 18 other factors that affect the trees include climate, 4. Construct a Simulation Work in a small group 12 80 6 40 diseases, and other herbivores. to plan, develop, and construct a simulation of (cm) the reintroduction of wolves to Yellowstone. The 0

Population 0 (in thousands) 1995 2000 2005 2010 Height Sprout In some parts of Yellowstone, wolf reintroduction simulation should model changes in the popula- 1995 2000 2005 2010 Year allowed willows to regrow, and significantly tions of other species upon the reintroduction of Year restored stream communities. In other places (still wolves into the ecosystem. You may choose to Credit, all graphs: National Park Service. U.S. Department of construct a physical simulation, in which students within the park) reintroduction did not have that the Interior model wolves and other species. Or if possible, full effect. Research studies both in Yellowstone prepare a computer simulation. • Identify how the initial conditions changed • Use the simulation to help predict the effects and in Banff National Park in Canada have pro- from year to year, which are the rates that the of possible changes to the Yellowstone vided data for scientists to propose hypotheses Follow these steps: populations increase or decrease. ecosystem. For example, simulate the effect to explain these differences. • Conduct additional research on factors that of a rapid decrease in the population of trees, • Begin the simulation by modeling the initial affect the populations of these species. or a rapid increase in the elk population. 1. Analyze Graphs Describe the trends in each of conditions. Then, model the changing • Identify the initial conditions, which are the the four populations shown in the graphs. What conditions, as well as the events—such as • Discuss the limitations of your simulation. sizes of the populations before the wolves data do the graphs provide? Describe any trends wolves preying on elk—that help explain Explain why any simulation may not accurately were reintroduced. in the data that you observe. these changes. predict the changes in a real ecosystem, such as Yellowstone.

194 Chapter 6 Communities and Ecosystem Dynamics Performance-Based Assessment 195 26 PERFORMANCE-BASED ASSESSMENT ENGINEERING PROJECT The Populations of Yellowstone

Construct a Solution HS-LS2-2, HS-LS2-7, HS-LS4-6

194 Chapter 6 Communities and Ecosystem Dynamics Performance-Based Assessment 195 27 CHAPTER 6  ASSESSMENT

KEY QUESTIONS AND TERMS 6.2 Succession 15. A salt marsh that helps prevent flooding of a 25. Construct an Explanation Years after a forest burns, the land is covered in tall grasses and some HS-LS2-2, HS-LS2-6, HS-LS2-7, HS-LS4-6 coastal town is an example of what ecosystem 6.1 Habitats, Niches, and service? young trees. Will the tall grasses eventually die 8. Place these stages of succession in order from a. nutrient cycling off? Explain why or why not. Species Interactions earliest to latest. b. buffering 26. Construct an Argument Choose an ecosystem HS-LS2-2 c. carbon storage near you, or another familiar ecosystem. Why is 1. Which species directly affects the size and distribu- d. pest regulation biodiversity important to the health of the eco- tion of the plant population in its community? 16. How is species diversity different from genetic system, or to the ecosystem services it provides? diversity? Support your argument with specific examples. 17. What is an ecosystem service? List three examples. The table describes the niches of wildebeests and 18. What describes the resilience of an ecosystem? zebras. Use the table to answer questions 27–29. Include an example of resilience. a. Wildebeest and Zebra a. Time Timeb. 3 years 3 years5 years 5 years40+ years 40+ years CRITICAL THINKING HS-LS2-2, HS-LS2-6, HS-LS2-7 19. Draw Conclusions A polar bear and a grizzly bear live in very different biomes. Based on this infor- b. mation, can you conclude that the microbiomes inside their intestines are also very different from each other? Explain your reasoning. 20. Analyze Text Structure Using the text from this chapter, analyze the relationships among the key c. Time d. Time terms habitat, niche, resource, and competitive Habitat Grassy plains and open woodlands of Africa c. 3 years 5 years 40+ years 3 years 5 years 40+ yearsexclusion principle. Diet Both graze on grasses. Wildebeests prefer 9. The first organisms to repopulate an area affected 21. Construct Graphs Banana plants are native to short grass with new growth. by a volcanic eruption are called tropical climates. In an experiment, a scientist Predators Lion, cheetah, hyena, wild dog raises two groups of banana plants. One group a. keystone species is kept at a temperature of 30°C (85°F). In the Behavior Both migrate in large herds. Wildebeests tend b. climax species to follow zebras from one area to the next. second group, the scientist decreases the tem- d c . . primary producers perature from 30°C by one 1° every day. Predict d. pioneer species 2. What of the following is most likely to occur if an the results of this experiment. Construct a graph 27. Summarize Describe and compare the niches of organism’s environment is outside the organism’s 10. What determines whether ecological succession to illustrate your prediction. the zebras and wildebeests. range of tolerance? is classified as primary succession or secondary 22. Plan an Investigation A scientist discovers a col- succession? 28. Apply Scientific Reasoning Why must the zebras a. The growth of the organisms increases. ony of bacteria growing on the roots of a peanut and wildebeests fill different niches on the open b. The organisms fail to reproduce. 11. What is often the end result of secondary plant. The scientist wonders if the bacteria are a plains and woodlands of Africa? Use your knowl- c. The organisms produce more offspring to succession? parasite of the plant, or if they live in a mutualistic edge of niches and the information in the table to increase the chance of survival. 12. What is the meaning of the word “pioneer” in the relationship. Outline the steps of an investiga- justify your answer. d. The organisms develop mutualistic term pioneer species? tion that could provide evidence to answer this question. 29. Gather Evidence What evidence would you relationships. 13. Describe the two major causes of ecological need to distinguish the niches of the zebras and 3. What is the difference between an organism’s succession. 23. Design a Solution There is growing concern over wildebeests? habitat and its niche? the decline in the U.S. honeybee population due to the use of pesticides. How could a reduced hon- 30. Summarize What type of events can lead to a loss 4. How can different species of insect-eating birds 6.3 Biodiversity, Ecosystems, eybee population affect biodiversity and ecosys- of biodiversity? After the event, how does biodi- live in the same tree? and Resilience tem services? Design a solution for this problem. versity recover? 5. How is commensalism different from mutualism? HS-LS2-6, HS-LS2-7, HS-LS4-6 24. Predict A developer plans to build a resort with 31. Construct an Explanation Describe the events that occur to shape an ecosystem after a cata- 6. What is the competitive exclusion principle? 14. Which term describes the variety of species in a golf courses, a shopping mall, and lots of paved strophic event. 7. How is parasitism different from other types certain area? parking lots on the shrubland and sand dunes of symbiosis? a. succession c. biodiversity beside a beach. Predict how this development will b. ecosystem d. genetic diversity affect ecosystem services in the area.

196 Chapter 6 Communities and Ecosystem Dynamics Chapter Assessment 197 28 CHAPTER 6  ASSESSMENT

196 Chapter 6 Communities and Ecosystem Dynamics Chapter Assessment 197 29 CHAPTER 6 CHAPTER 6  ASSESSMENT END-OF-COURSE TEST PRACTICE

CROSSCUTTING CONCEPTS 37. Predict How do you predict the carbon storage of 1. From 1970 to 2016, scientists were regularly 4. A community is concerned about the effect of a pro- the forest will change beyond the 300 years shown observing the Joshua County Nature Reserve. posed housing development on the biodiversity of a 32. Scale, Proportion, and Quantity Why is it useful in the graph? Their data show that a community of grasses and local pond. To mitigate the effect of the houses, the to describe the soil of a forest as a microbiome, other small plants was gradually replaced by a community is considering a ban on lawn fertilizer. and separate from the forest biome above it? Tolerance pine forest. Which claim or set of claims about the A computer simulation was used to predict the out- Lower limit Zone of Zone of Upper limit history of the nature reserve could be supported come of the ban. The results are shown in the table. 33. Stability and Change After a climax community is of tolerance stress stress of tolerance disturbed, such as by a fire or flood, will it always Optimum range by the data and logical reasoning? return to its original condition? Explain why or I. Several years before 1970, a forest fire Number of Species why not. burned down a pine forest. II. For several years until 1970, a pine forest Development, No Development with a

Population was gradually replaced by grasses and other Year development unregulated fertilizer ban MATH CONNECTIONS small plants. Low Range of High III. The land was used for farming or ranching 0 100 100 100 Analyze and Interpret Data Environmental Variable before 1970, but was then abandoned. 5 95 90 90 CCSS.MATH.CONTENT.MP4, CCSS.MATH.CONTENT.HSS.IC.A.1 A. I only B. II only C. III only 10 102 77 83 38. Analyze Data The graph shows the tolerance of a Scientists at Oregon State University developed a D E species to environmental variables. Draw a graph . I and III only . I, II, and II. 15 98 60 78 computer model to analyze the carbon storage of a that shows a species with greater tolerance to the 2. Modern farming practices often act to reduce 20 103 51 74 developing forest. The graph below describes the same variables. Draw a graph that shows a species biodiversity, such as when genetically-identical 25 99 50 75 carbon storage of a forest during primary succession. with lesser tolerance. crops are raised in large fields. Which of the Use the graph to answer questions 34–36. following proposed solutions would most likely improve the genetic diversity of a field of potato If the community decides to allow the housing Primary Succession LANGUAGE ARTS CONNECTION plants and increase the value of the potato crop? development, what is the strongest argument for banning the use of fertilizer that is supported by Soil Live A. Raise a variety of wild potatoes in the field Write About Science the results of the simulation? Detritus Total B. Reduce the use of pesticides and fertilizer 160 CCSS.ELA-LITERACY.WHST.9-10.2 C. Increase the use of pesticides and fertilizer A. Compared to no regulations, banning lawn fer- 140 39. Write Explanatory Texts The diagram below D. Transfer useful genes from wild potato plants tilizer increases species diversity by 50 percent 120 shows the changes to a plot of land over time. to the crop plants after 25 years. 100 Write a paragraph or a list of numbered captions B. Compared to initial conditions, banning 80 E. Allow some potatoes to remain in the field that describes these changes. Be sure to use the over winter lawn fertilizer decreases species diversity by 60 appropriate vocabulary terms from the chapter. 25 percent after 25 years. 40 3. Which of these events is MOST LIKELY to be fol- C. Compared to no housing development, ban- 20 Changes to a Plot of Land lowed by primary succession in the area where the

Carbon stores (MgC/ha) Carbon stores ning lawn fertilizer decreases species diversity 0 event occurs? 0 50 100 150 200 250 300 by 25 percent after 25 years. A. A fire burns most of the trees of a forest. Time (years) D. With no regulations, species diversity decreases B. Floodwaters cover and then drain away from from year to year. Source: HARMON, M. E. 2001. Carbon cycling in a valley. forests: simple simulation models. H. J. Andrews E. Without the housing development, species Research Report Number 2 C. A volcanic eruption covers a mountainside with diversity remains about the same from year molten rock. to year. 34. Interpret Graphs According to the model, how D. A farmer stops raising crops on a field. E. Snow covers a meadow during the winter. does the rate of carbon storage change during the Mosses Grasses Shrubs Softwood Hardwood first 300 years of primary succession? Trees Trees Time  ASSESSMENT 35. Construct an Explanation The graph shows when live plants, detritus, and soil each begin storing 40. Write Procedures For additional assessment carbon during primary succession. Explain why Science students are observing practice, Go Online to they begin storing carbon at different times. a population of pheasants in a wilderness area. Write a procedure for the students to follow to access your digital course. 36. Develop Models A student writes a quadratic help them identify the niche of the pheasants. equation to represent the curve in the graph for total carbon storage shown. The equation has the Read About Science 2 If You Have Trouble With… form C = –at + bt, in which C represents total car- CCSS.ELA-LITERACY.RST.9-10.1 bon storage, t is time, and a and b are constants. Question 1 2 3 4 41. Cite Textual Evidence Review the list of ecosys- How well does this equation model the curve? tem services presented at the end of Lesson 6.3. See Lesson 6.2 6.3 6.2 6.3 Is biodiversity necessary for ecosystems to supply Performance Expectation HS-LS2-6 HS-LS2-7 HS-LS2-6 HS-LS4-6 all of these services? Include statements from the 198 Chapter 6 Communities and Ecosystem Dynamics text to support your answer. End-of-Course Test Practice 199 30 CHAPTER 6 CHAPTER 6  ASSESSMENT END-OF-COURSE TEST PRACTICE

32 NOTES

33 NOTES

34 35 Western Honey Bees (Apis mellifera), like the one featured on the front cover, are experiencing large scale losses of their colonies. This syndrome is called Colony Collapse Disorder. Scientists don’t know what is causing it.

CASE STUDY A sizable decline in the Honeybee population can have a substantial impact on agriculture. Honeybees pollinate many of the foods you eat every day like almonds, apples, and cucumbers. Scientists are researching the causes of Colony Collapse Disorder through studies, experiments, and analysis.

CASE STUDY CONNECTIONS As a Miller and Levine Biology student, you will conduct similar research through Case Studies. Every chapter features a real-world example of a modern scientific problem. As you progress through the chapter you will find Case Study Connections that link hands- on labs, data analysis, and interactive visuals to help you gather evidence.

CASE STUDY WRAP UP Make Your Case will give you the opportunity to generate solutions o the Case Study problem, emphasizing STEM integration, Evidence-Based Reasoning, and Problem-Based Learning. So get ready to speak the language of Science!

Visit pearsonschool.com/millerlevine to read more about this case study and learn how scientists are approaching this problem.

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