1. Communities and Ecosystems
Chapter 37
Communities and Ecosystems

2. Introduction Natural ecosystems are valuable because they
Natural ecosystems are valuable because they
provide natural resources,
support outdoor recreation, and
provide natural services including
buffering against hurricane damage,
recycling nutrients,
preventing erosion, and
pollinating crops.
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3. Community Structure and Dynamics Ecosystem Structure and Dynamics
Figure 37.0_1
Chapter 37: Big Ideas C h e m i c a l y n g
Energy flow
Figure 37.0_1 Chapter 37: Big Ideas
Community Structure
and Dynamics
Ecosystem Structure
and Dynamics 3

4. Figure 37.0_2
Figure 37.0_2 Only about a quarter of Earth’s land surfaces remain untouched by human alterations. 4

5. COMMUNITY STRUCTURE AND DYNAMICS
COMMUNITY STRUCTURE AND DYNAMICS
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6. 37.1 A community includes all the organisms inhabiting a particular area
Community ecology is concerned with factors that
influence species composition and distribution of communities and
affect community stability.
Student Misconceptions and Concerns
For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems.
Teaching Tips
1. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights.
2. In human society, a community might be roughly equivalent to a local population, perhaps all the people living in a town or city. The definition of a biological community is more inclusive, comprising all of the populations of organisms living close enough together for potential interaction.
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7. 37.1 A community includes all the organisms inhabiting a particular area
A biological community is
an assemblage of all the populations of organisms living close enough together for potential interaction and
described by its species composition.
The boundaries of a community vary with the research question to be investigated. For example, the boundaries of a community could be defined as
a pond or
the intestinal microbes of a pond organism.
Student Misconceptions and Concerns
For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems.
Teaching Tips
1. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights.
2. In human society, a community might be roughly equivalent to a local population, perhaps all the people living in a town or city. The definition of a biological community is more inclusive, comprising all of the populations of organisms living close enough together for potential interaction.
© 2012 Pearson Education, Inc. 7

8. 37.2 Interspecific interactions are fundamental to community structure
Interspecific interactions
are relationships with individuals of other species in the community,
greatly affect population structure and dynamics, and
can be categorized according to their effect on the interacting populations.
Student Misconceptions and Concerns
For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems.
Teaching Tips
1. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights.
2. Examples of interspecific competition are as close as the nearest lawn. Although students may be more likely to think of animal examples, the various grasses and weeds in a lawn reveal different strategies in their competition for sunlight, moisture, and soil.
3. If your class includes students with business interests, they may enjoy the following analogy. To better understand competition, students might think about fast-food restaurants in your region. Challenge your students to identify the strategies employed by these restaurants to compete with each other. As each restaurant makes changes, does the other restaurant respond? Restaurants changing strategies in response to each other is analogous to coevolution.
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9. 37.2 Interspecific interactions are fundamental to community structure
Interspecific competition occurs when populations of two different species compete for the same limited resource.
In mutualism, both populations benefit.
In predation, one species (the predator) kills and eats another (the prey).
In herbivory, an animal consumes plant parts or algae.
In parasitism, the host plants or animals are victimized by parasites or pathogens.
Student Misconceptions and Concerns
For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems.
Teaching Tips
1. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights.
2. Examples of interspecific competition are as close as the nearest lawn. Although students may be more likely to think of animal examples, the various grasses and weeds in a lawn reveal different strategies in their competition for sunlight, moisture, and soil.
3. If your class includes students with business interests, they may enjoy the following analogy. To better understand competition, students might think about fast-food restaurants in your region. Challenge your students to identify the strategies employed by these restaurants to compete with each other. As each restaurant makes changes, does the other restaurant respond? Restaurants changing strategies in response to each other is analogous to coevolution.
© 2012 Pearson Education, Inc. 9

10. Table 37.2
Table 37.2 Interspecific Interactions 10

11. 37.3 Competition may occur when a shared resource is limited
An ecological niche is the sum of an organism’s use of the biotic and abiotic resources in its environment.
Interspecific competition occurs when the niches of two populations overlap.
Competition lowers the carrying capacity of competing populations because the resources used by one population are not available to the other population.
Student Misconceptions and Concerns
1. For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems.
2. The concept of an ecological niche can be confusing. Ecologist Eugene Odum has suggested that an ecological niche is like an organism’s habitat (address) and its occupation combined.
Teaching Tips
1. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights.
2. If your class includes students with business interests, they may enjoy the following analogy. To better understand competition, students might think about fast-food restaurants in your region. Challenge your students to identify the strategies employed by these restaurants to compete with each other. As each restaurant makes changes, does the other restaurant respond? Restaurants changing strategies in response to each other is analogous to coevolution.
© 2012 Pearson Education, Inc. 11

12. Figure 37.3A
Figure 37.3A A Virginia’s warbler (Vermivora virginiae) 12

13. Figure 37.3B
Figure 37.3B An orange-crowned warbler (Vermivora celata) 13

14. 37.4 Mutualism benefits both partners
Reef-building corals and photosynthetic dinoflagellates illustrate the win/win nature of mutualism. Photosynthetic dinoflagellates
gain shelter in the cells of each coral polyp,
produce sugars used by the polyps, and
provide at least half of the energy used by the coral animals.
Student Misconceptions and Concerns
For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems.
Teaching Tips
1. Students who are business-oriented may also enjoy this analogy. Many corporate leaders describe the best business deals as mutualistic, fostering a win-win relationship. For example, perhaps a new company creates a marketable product from another company’s wastes.
2. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights.
Video: Clownfish and Anemone
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15. Figure 37.4
Figure 37.4 Coral polyps 15

16. Video: Seahorse Camouflage
37.5 EVOLUTION CONNECTION: Predation leads to diverse adaptations in prey species
Predation benefits the predator but kills the prey.
Prey adapt using protective strategies that include
camouflage,
mechanical defenses, and
chemical defenses.
Student Misconceptions and Concerns
For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems.
Teaching Tips
1. Rattlesnakes are a good example of a highly specialized predator. Since they are unable to move fast enough to catch their prey, rattlesnakes typically ambush them, a process facilitated by their camouflaged bodies. Rattlesnakes often feed during the cooler parts of the day, using heat-detecting facial pits to identify prey before injecting them with fast-acting venom. The prey is immediately released (perhaps to avoid damage to the snake from struggling prey), but is disabled by the venom within seconds. The rattlesnake then uses a variety of senses to track the prey the short distance to where it has collapsed.
2. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights.
Video: Seahorse Camouflage
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17. Figure 37.5A
Figure 37.5A Camouflage: a gray tree frog on bark 17

18. Figure 37.5B
Figure 37.5B Chemical defenses: the monarch butterfly 18

19. 37.6 EVOLUTION CONNECTION: Herbivory leads to diverse adaptations in plants
Herbivores and plants undergo coevolution,
a series of reciprocal evolutionary adaptations in two species,
in which change in one species acts as a new selective force on another.
Student Misconceptions and Concerns
For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems.
Teaching Tips
1. If your class includes students with business interests, they may enjoy the following analogy. To better understand competition, students might think about fast-food restaurants in your region. Challenge your students to identify the strategies employed by these restaurants to compete with each other. As each restaurant makes changes, does the other restaurant respond? Restaurants changing strategies in response to each other is analogous to coevolution.
2. Coevolution is illustrated by organisms that exhibit reciprocal evolutionary adaptations. Challenge students to explain how rewarding a pollinator with nectar has benefited some plants. Why would plants that have adaptations for only certain pollinators have an advantage? In many cases, pollinators that are restricted to certain species are more likely to transport pollen between members of that species instead of wasting pollen by taking it to other species.
3. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights.
© 2012 Pearson Education, Inc. 19

20. 37.6 EVOLUTION CONNECTION: Herbivory leads to diverse adaptations in plants
A plant whose body parts have been eaten by an animal must expend energy to replace the loss.
Thus, numerous defenses against herbivores have evolved in plants.
Plant defenses against herbivores include
spines and thorns and
chemical toxins.
Student Misconceptions and Concerns
For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems.
Teaching Tips
1. If your class includes students with business interests, they may enjoy the following analogy. To better understand competition, students might think about fast-food restaurants in your region. Challenge your students to identify the strategies employed by these restaurants to compete with each other. As each restaurant makes changes, does the other restaurant respond? Restaurants changing strategies in response to each other is analogous to coevolution.
2. Coevolution is illustrated by organisms that exhibit reciprocal evolutionary adaptations. Challenge students to explain how rewarding a pollinator with nectar has benefited some plants. Why would plants that have adaptations for only certain pollinators have an advantage? In many cases, pollinators that are restricted to certain species are more likely to transport pollen between members of that species instead of wasting pollen by taking it to other species.
3. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights.
© 2012 Pearson Education, Inc. 20

21. Eggs Sugar deposits Figure 37.6
Figure 37.6 Coevolution: Heliconius and the passionflower vine (Passiflora) 21

22. Figure 37.6_1
Figure 37.6_1 Coevolution: Heliconius and the passionflower vine (Passiflora) (part 1) 22

23. Figure 37.6_2
Eggs
Figure 37.6_2 Coevolution: Heliconius and the passionflower vine (Passiflora) (part 2) 23

24. Sugar deposits Figure 37.6_3
Figure 37.6_3 Coevolution: Heliconius and the passionflower vine (Passiflora) (part 3) 24

25. 37.7 Parasites and pathogens can affect community composition
A parasite lives on or in a host from which it obtains nourishment.
Internal parasites include nematodes and tapeworms.
External parasites include mosquitoes, ticks, and aphids.
Pathogens are disease-causing microscopic parasites that include
bacteria,
viruses,
fungi, or
protists.
Student Misconceptions and Concerns
For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems.
Teaching Tips
1. Pathogens are probably what most people refer to as germs. Students might believe that this general term refers to some specific type of organism.
2. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights.
© 2012 Pearson Education, Inc. 25

26. Figure 37.7
Figure 37.7 Aphids parasitizing a plant 26

27. 37.7 Parasites and pathogens can affect community composition
Non-native pathogens can have rapid and dramatic impacts.
The American chestnut was devastated by the chestnut blight protist.
A fungus-like pathogen is currently causing sudden oak death on the West Coast.
Non-native pathogens can cause a decline of the ecosystem.
Student Misconceptions and Concerns
For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems.
Teaching Tips
1. Pathogens are probably what most people refer to as germs. Students might believe that this general term refers to some specific type of organism.
2. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights.
© 2012 Pearson Education, Inc. 27

28. 37.8 Trophic structure is a key factor in community dynamics
The trophic structure of a community is a pattern of feeding relationships consisting of several different levels.
The sequence of food transfer up the trophic levels is known as a food chain.
The transfer of food moves chemical nutrients and energy from producers up through the trophic levels in a community.
Student Misconceptions and Concerns
For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems.
Teaching Tips
1. Students have often had prior exposure to the concepts of food webs and food chains. Present a food web (perhaps Figure 37.9) to your class and challenge them to predict the consequences of a decrease or increase in the population of one of the organisms. This activity can help students understand how difficult it is to make precise predictions about these complex systems.
2. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights.
© 2012 Pearson Education, Inc. 28

29. 37.8 Trophic structure is a key factor in community dynamics
Producers
are autotrophs and
support all other trophic levels.
Consumers are heterotrophs.
Herbivores are primary consumers.
Secondary consumers typically eat herbivores.
Tertiary consumers typically eat secondary consumers.
Quaternary consumers typically eat tertiary consumers.
Student Misconceptions and Concerns
For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems.
Teaching Tips
1. Students have often had prior exposure to the concepts of food webs and food chains. Present a food web (perhaps Figure 37.9) to your class and challenge them to predict the consequences of a decrease or increase in the population of one of the organisms. This activity can help students understand how difficult it is to make precise predictions about these complex systems.
2. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights.
© 2012 Pearson Education, Inc. 29

30. 37.8 Trophic structure is a key factor in community dynamics
Detritivores derive their energy from detritus, the dead material produced at all the trophic levels.
Decomposers
are mainly prokaryotes and fungi and
secrete enzymes that digest molecules in organic materials and convert them into inorganic forms, in the process called decomposition.
Student Misconceptions and Concerns
For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems.
Teaching Tips
1. Students have often had prior exposure to the concepts of food webs and food chains. Present a food web (perhaps Figure 37.9) to your class and challenge them to predict the consequences of a decrease or increase in the population of one of the organisms. This activity can help students understand how difficult it is to make precise predictions about these complex systems.
2. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights.
Video: Shark Eating a Seal
© 2012 Pearson Education, Inc. 30

31. A terrestrial food chain An aquatic food chain
Figure 37.8_s1
Trophic level
Figure 37.8_s1 Two food chains (step 1)
Producers
Plant
Phytoplankton
A terrestrial food chain
An aquatic food chain 31

32. A terrestrial food chain An aquatic food chain
Figure 37.8_s2
Trophic level
Figure 37.8_s2 Two food chains (step 2)
Primary
consumers
Grasshopper
Zooplankton
Producers
Plant
Phytoplankton
A terrestrial food chain
An aquatic food chain 32

33. Secondary consumers Primary consumers
Figure 37.8_s3
Trophic level
Secondary
consumers
Mouse
Herring
Figure 37.8_s3 Two food chains (step 3)
Primary
consumers
Grasshopper
Zooplankton
Producers
Plant
Phytoplankton
A terrestrial food chain
An aquatic food chain 33

34. Tertiary consumers Secondary consumers Primary consumers
Figure 37.8_s4
Trophic level
Tertiary
consumers
Snake
Tuna
Secondary
consumers
Mouse
Herring
Figure 37.8_s4 Two food chains (step 4)
Primary
consumers
Grasshopper
Zooplankton
Producers
Plant
Phytoplankton
A terrestrial food chain
An aquatic food chain 34

35. A terrestrial food chain An aquatic food chain
Figure 37.8_s5
Trophic level
Quaternary
consumers
Hawk
Killer whale
Tertiary
consumers
Snake
Tuna
Secondary
consumers
Mouse
Herring
Figure 37.8_s5 Two food chains (step 5)
Primary
consumers
Grasshopper
Zooplankton
Producers
Plant
Phytoplankton
A terrestrial food chain
An aquatic food chain 35

36. 37.9 Food chains interconnect, forming food webs
A food web is a network of interconnecting food chains.
Notice that
consumers may eat more than one type of producer and
several species of consumers may feed on the same species of producer.
Student Misconceptions and Concerns
For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems.
Teaching Tips
1. Students have often had prior exposure to the concepts of food webs and food chains. Present a food web (perhaps Figure 37.9) to your class and challenge them to predict the consequences of a decrease or increase in the population of one of the organisms. This activity can help students understand how difficult it is to make precise predictions about these complex systems.
2. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights.
© 2012 Pearson Education, Inc. 36

37. Figure 37.9 Figure 37.9 A food web 37 Quaternary, tertiary,
and secondary
consumers
Tertiary
and
secondary
consumers
Secondary
and
primary
consumers
Primary
consumers
Figure 37.9 A food web
Producers
(plants) 37

38. Primary consumers Producers (plants) Figure 37.9_1
Figure 37.9_1 A food web (part 1) 38

39. Quaternary, tertiary, and secondary consumers Tertiary and secondary
Figure 37.9_2
Quaternary,
tertiary,
and secondary
consumers
Tertiary
and
secondary
consumers
Secondary
and
primary
consumers
Figure 37.9_2 A food web (part 2)
Primary
consumers 39

40. 37.10 Species diversity includes relative abundance and species richness
Species diversity is defined by two components:
Species richness, the number of species in a community, and
Relative abundance, the proportional representation of a species in a community.
Student Misconceptions and Concerns
For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems.
Teaching Tips
1. Diversity within a species has some of the same advantages as diversity within a community. In both situations, diversity limits the damage from a pathogen or predator specialized to attack one variation within a species or one species in a community.
2. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights.
© 2012 Pearson Education, Inc. 40

41. 37.10 Species diversity includes relative abundance and species richness
Plant species diversity in a community affects the species diversity of animals.
Species diversity has consequences for pathogens.
Low species diversity is characteristic of most modern agricultural ecosystems.
Student Misconceptions and Concerns
For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems.
Teaching Tips
1. Diversity within a species has some of the same advantages as diversity within a community. In both situations, diversity limits the damage from a pathogen or predator specialized to attack one variation within a species or one species in a community.
2. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights.
© 2012 Pearson Education, Inc. 41

42. Woodlot A Figure 37.10A Figure 37.10A Species composition of woodlot A42

43. Woodlot B Figure 37.10B Figure 37.10B Species composition of woodlot B43

44. Table 37.10
Table Relative Abundance of Tree Species in Woodlots A and B 44

45. 37.11 Keystone species have a disproportionate impact on diversity
A keystone species
is a species whose impact on its community is larger than its biomass or abundance indicates and
occupies a niche that holds the rest of its community in place.
Examples of keystone species in marine ecosystems include
Pisaster sea stars and
long-spined sea urchins.
Student Misconceptions and Concerns
For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems.
Teaching Tips
1. Many keystone species have been identified in ecosystems, including sea otters, elephants, freshwater bass, and Pisaster, a sea star noted in Figure 37.11B. Challenge your class to explain how the concept of keystone species impacts the efforts of conservation biologists. Why might some species be more important to conserve?
2. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights.
© 2012 Pearson Education, Inc. 45

46. Keystone Keystone absent Figure 37.11A
Figure 37.11A Arch collapse with removal of keystone 46

47. Figure 37.11B
Figure 37.11B A Pisaster sea star, a keystone species, eating a mussel 47

48. Figure 37.11C
Figure 37.11C Diadema sea urchins grazing on a reef 48

49. Figure 37.11D
Figure 37.11D A reef overgrown by fleshy seaweeds 49

50. 37.12 Disturbance is a prominent feature of most communities
Disturbances
are events that damage biological communities and
include storms, fires, floods, droughts, overgrazing, or human activity.
The types, frequency, and severity of disturbances vary from community to community.
Student Misconceptions and Concerns
1. For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems.
2. The idea that ecosystems are relatively stable is common. Natural disturbances of any sort (fires, earthquakes, floods, or strong storms) are typically viewed as tragic and damaging to ecosystems. Before beginning the topic of ecological disturbances, consider asking your students to briefly respond to news that a state or federal park has (a) been burned, (b) been struck by high winds and/or lightning, or (c) been temporarily flooded. In addition, consider asking what, if anything, should be done to prevent or repair this damage?
Teaching Tips
1. Before and after images of the impact and recovery of an ecosystem from a natural disaster can be more powerful than any verbal explanation of the process. Consider locating before and after images of ecosystems damaged by hurricanes, fire, or the 1980 eruption of Mt. St. Helens, to show recovery.
2. Depending upon your location and its circumstances, consider a short field trip on or near your campus to show disturbed regions and signs of recovery.
3. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights.
© 2012 Pearson Education, Inc. 50

51. 37.12 Disturbance is a prominent feature of most communities
Communities change drastically following a severe disturbance that
strips away vegetation and
removes significant amounts of soil.
Ecological succession results from colonization by a variety of species, which are replaced by a succession of other species.
Student Misconceptions and Concerns
1. For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems.
2. The idea that ecosystems are relatively stable is common. Natural disturbances of any sort (fires, earthquakes, floods, or strong storms) are typically viewed as tragic and damaging to ecosystems. Before beginning the topic of ecological disturbances, consider asking your students to briefly respond to news that a state or federal park has (a) been burned, (b) been struck by high winds and/or lightning, or (c) been temporarily flooded. In addition, consider asking what, if anything, should be done to prevent or repair this damage?
Teaching Tips
1. Before and after images of the impact and recovery of an ecosystem from a natural disaster can be more powerful than any verbal explanation of the process. Consider locating before and after images of ecosystems damaged by hurricanes, fire, or the 1980 eruption of Mt. St. Helens, to show recovery.
2. Depending upon your location and its circumstances, consider a short field trip on or near your campus to show disturbed regions and signs of recovery.
3. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights.
© 2012 Pearson Education, Inc. 51

52. 37.12 Disturbance is a prominent feature of most communities
Primary succession begins in a virtually lifeless area with no soil.
Secondary succession occurs when a disturbance destroys an existing community but leaves the soil intact.
Student Misconceptions and Concerns
1. For many students, understanding ecosystems is like appreciating art. Although both are visible to the naked eye, some background is required to understand the method of composition, the significance of components, and the nature of interactions. The fundamentals introduced in this chapter are new ways to see generally familiar systems.
2. The idea that ecosystems are relatively stable is common. Natural disturbances of any sort (fires, earthquakes, floods, or strong storms) are typically viewed as tragic and damaging to ecosystems. Before beginning the topic of ecological disturbances, consider asking your students to briefly respond to news that a state or federal park has (a) been burned, (b) been struck by high winds and/or lightning, or (c) been temporarily flooded. In addition, consider asking what, if anything, should be done to prevent or repair this damage?
Teaching Tips
1. Before and after images of the impact and recovery of an ecosystem from a natural disaster can be more powerful than any verbal explanation of the process. Consider locating before and after images of ecosystems damaged by hurricanes, fire, or the 1980 eruption of Mt. St. Helens, to show recovery.
2. Depending upon your location and its circumstances, consider a short field trip on or near your campus to show disturbed regions and signs of recovery.
3. Many students have been exposed to diverse ecosystems only through television and movies, which have likely focused on a few species. Before discussing this chapter, consider showing the class a good video (it need not be long) about an ecosystem. The video can then serve as a shared recent experience to which you can relate the content of this chapter. Alternately, you can relate some of the basics of this chapter to a local or regional example with which most students are familiar. There may even be a distinct community on your campus, such as a pond, wooded area, etc., that students could visit and return from with new insights.
© 2012 Pearson Education, Inc. 52