1. Chapter 7
Community Ecology

2. Core Case Study: Why Should We Care about the American Alligator?
Hunters wiped out population to the point of near extinction.
Their nesting grounds are easy targets, skins used to make shoes and such, meat is exotic
Alligators have important ecological role.
Figure 7-1

3. Core Case Study: Why Should We Care about the American Alligator?
Dig deep depressions (gator holes).
Hold water during dry spells, serve as refuges for aquatic life.
Build nesting mounds.
provide nesting and feeding sites for birds.
Keeps areas of open water free of vegetation.
Alligators are a keystone species:
Help maintain the structure and function of the communities where it is found.

5. COMMUNITY STRUCTURE AND SPECIES DIVERSITY
Biological communities differ in their structure and physical appearance.
Figure 7-2

6. Tropical rain forest Coniferous forest Deciduous forest Thorn forest
Figure 7.2
Natural capital: generalized types, relative sizes, and stratification of plant species in various terrestrial communities.
Tropical
rain forest
Coniferous
forest
Deciduous
forest
Thorn
forest
Thorn
scrub
Tall-grass
prairie
Short-grass
prairie
Desert
scrub
Fig. 7-2, p. 144

7. Of the following, ecosystem structure is least likely to include
a. species abundance.
b. species diversity.
c. physical appearance.
d. biochemical reactions in the intestines of detritus feeders.
e. niche structure.

8. Species Diversity and Niche Structure: Different Species Playing Different Roles
Species diversity: the number of different species it contains (species richness) combined with the abundance of individuals within each of those species (species evenness).

9. Species Diversity and Niche Structure
Niche structure: how many potential ecological niches occur, how they resemble or differ, and how the species occupying different niches interact.
Geographic location: species diversity is highest in the tropics and declines as we move from the equator toward the poles.

10. Animation: Species Diversity By Latitude
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11. TYPES OF SPECIES
Native, nonnative, indicator, keystone, and foundation species play different ecological roles in communities.
Native: those that normally live and thrive in a particular community.
Nonnative species: those that migrate, deliberately or accidentally introduced into a community.
snakehead

12. Zebra Mussel

13. A toad
                                                                                                  

14. The Dingo-Australia

15. Eastern Hemlock

16. Elephant

17. Animation: Area and Distance Effects
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18. Indicator Species: Biological Smoke Alarms
Species that serve as early warnings of damage to a community or an ecosystem.
Presence or absence of trout species because they are sensitive to temperature and oxygen levels.

19. Keystone Species: Major Players
Keystone species help determine the types and numbers of other species in a community thereby helping to sustain it.
Figures 7-4 and 7-5

20. Foundation Species: Other Major Players
Expansion of keystone species category.
Foundation species can create and enhance habitats that can benefit other species in a community.
Elephants push over, break, or uproot trees, creating forest openings promoting grass growth for other species to utilize.

21. Case Study: Why are Amphibians Vanishing?
Frogs serve as indicator species because different parts of their life cycles can be easily disturbed.
Figure 7-3

22. Adult frog (3 years) Young frog Sperm Tadpole develops into frog
Sexual
Reproduction
Tadpole
Figure 7.3
Typical life cycle of a frog. Populations of various frog species can decline because of the effects of harmful factors at different points in their life cycle. Such factors include habitat loss, drought, pollution, increased ultraviolet radiation, parasitism, disease, overhunting for food (frog legs), and nonnative predators and competitors.
Eggs
Fertilized egg
development
Egg hatches
Organ formation
Fig. 7-3, p. 147

23. Case Study: Why are Amphibians Vanishing?
Habitat loss and fragmentation.
Prolonged drought.
Pollution.
Increases in ultraviolet radiation.
Parasites.
Viral and Fungal diseases.
Overhunting.
Natural immigration or deliberate introduction of nonnative predators and competitors.

24. Video: Frogs Galore From ABC News, Biology in the Headlines, 2005 DVD.
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From ABC News, Biology in the Headlines, 2005 DVD.

25. SPECIES INTERACTIONS: COMPETITION AND PREDATION
Species can interact through competition, predation, parasitism, mutualism, and commensalism.
Some species evolve adaptations that allow them to reduce or avoid competition for resources with other species (resource partitioning).

26. Animation: How Species Interact
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27. Resource Partitioning
Each species minimizes competition with the others for food by spending at least half its feeding time in a distinct portion of the spruce tree and by consuming somewhat different insect species.
Figure 7-7

28. Niche Specialization
Niches become separated to avoid competition for resources.
Figure 7-6

29. Animation: Gause’s Competition Experiment
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30. SPECIES INTERACTIONS: COMPETITION AND PREDATION
Species called predators feed on other species called prey.
Organisms use their senses to locate objects and prey and to attract pollinators and mates.
Some predators are fast enough to catch their prey, some hide and lie in wait, and some inject chemicals to paralyze their prey.
Predator vs. Prey Videos -- National Geographic

31. PREDATION
Some prey escape their predators or have outer protection, some are camouflaged, and some use chemicals to repel predators.
Figure 7-8

32. (a) Span worm Fig. 7-8a, p. 153 Figure 7.8
Natural capital: some ways in which prey species avoid their predators: (a, b) camouflage, (c–e) chemical warfare, (d, e) warning coloration, (f) mimicry, (g) deceptive looks, and (h) deceptive behavior.
(a) Span worm
Fig. 7-8a, p. 153

33. (b) Wandering leaf insect
Figure 7.8
Natural capital: some ways in which prey species avoid their predators: (a, b) camouflage, (c–e) chemical warfare, (d, e) warning coloration, (f) mimicry, (g) deceptive looks, and (h) deceptive behavior.
(b) Wandering leaf insect
Fig. 7-8b, p. 153

34. (c) Bombardier beetle Fig. 7-8c, p. 153 Figure 7.8
Natural capital: some ways in which prey species avoid their predators: (a, b) camouflage, (c–e) chemical warfare, (d, e) warning coloration, (f) mimicry, (g) deceptive looks, and (h) deceptive behavior.
(c) Bombardier beetle
Fig. 7-8c, p. 153

35. (d) Foul-tasting monarch butterfly
Figure 7.8
Natural capital: some ways in which prey species avoid their predators: (a, b) camouflage, (c–e) chemical warfare, (d, e) warning coloration, (f) mimicry, (g) deceptive looks, and (h) deceptive behavior.
(d) Foul-tasting monarch butterfly
Fig. 7-8d, p. 153

36. (e) Poison dart frog Fig. 7-8e, p. 153 Figure 7.8
Natural capital: some ways in which prey species avoid their predators: (a, b) camouflage, (c–e) chemical warfare, (d, e) warning coloration, (f) mimicry, (g) deceptive looks, and (h) deceptive behavior.
(e) Poison dart frog
Fig. 7-8e, p. 153

37. (f) Viceroy butterfly mimics monarch butterfly
Figure 7.8
Natural capital: some ways in which prey species avoid their predators: (a, b) camouflage, (c–e) chemical warfare, (d, e) warning coloration, (f) mimicry, (g) deceptive looks, and (h) deceptive behavior.
(f) Viceroy butterfly mimics
monarch butterfly
Fig. 7-8f, p. 153

38. (g) Hind wings of Io moth resemble eyes of a much larger animal.
Figure 7.8
Natural capital: some ways in which prey species avoid their predators: (a, b) camouflage, (c–e) chemical warfare, (d, e) warning coloration, (f) mimicry, (g) deceptive looks, and (h) deceptive behavior.
(g) Hind wings of Io moth
resemble eyes of a much
larger animal.
Fig. 7-8g, p. 153

39. Figure 7.8
Natural capital: some ways in which prey species avoid their predators: (a, b) camouflage, (c–e) chemical warfare, (d, e) warning coloration, (f) mimicry, (g) deceptive looks, and (h) deceptive behavior.
(h) When touched, snake caterpillar changes shape to look like head of snake.
Fig. 7-8h, p. 153

40. SPECIES INTERACTIONS: PARASITISM, MUTUALISM, AND COMMENSALIM
Parasitism occurs when one species feeds on part of another organism.
In mutualism, two species interact in a way that benefits both.
Commensalism is an interaction that benefits one species but has little, if any, effect on the other species.

41. Parasites: Sponging Off of Others
Although parasites can harm their hosts, they can promote community biodiversity.
Some parasites live in host (micororganisms, tapeworms).
Some parasites live outside host (fleas, ticks, mistletoe plants, sea lampreys).
Some have little contact with host (dump-nesting birds like cowbirds, some duck species)

42. Mutualism: Win-Win Relationship
Two species can interact in ways that benefit both of them.
Figure 7-9

43. (a) Oxpeckers and black rhinoceros
Figure 7.9
Natural capital: examples of mutualism. (a) Oxpeckers (or tickbirds) feed on parasitic ticks that infest large, thick-skinned animals such as the endangered black rhinoceros. (b) A clownfish gains protection and food by living among deadly stinging sea anemones and helps protect the anemones from some of their predators. (c) Beneficial effects of mycorrhizal fungi attached to roots of juniper seedlings on plant growth compared to (d) growth of such seedlings in sterilized soil without mycorrhizal fungi.
(a) Oxpeckers and black rhinoceros
Fig. 7-9a, p. 154

44. (b) Clownfish and sea anemone
Figure 7.9
Natural capital: examples of mutualism. (a) Oxpeckers (or tickbirds) feed on parasitic ticks that infest large, thick-skinned animals such as the endangered black rhinoceros. (b) A clownfish gains protection and food by living among deadly stinging sea anemones and helps protect the anemones from some of their predators. (c) Beneficial effects of mycorrhizal fungi attached to roots of juniper seedlings on plant growth compared to (d) growth of such seedlings in sterilized soil without mycorrhizal fungi.
(b) Clownfish and sea anemone
Fig. 7-9b, p. 154

45. (c) Mycorrhizal fungi on juniper seedlings in normal soil
Figure 7.9
Natural capital: examples of mutualism. (a) Oxpeckers (or tickbirds) feed on parasitic ticks that infest large, thick-skinned animals such as the endangered black rhinoceros. (b) A clownfish gains protection and food by living among deadly stinging sea anemones and helps protect the anemones from some of their predators. (c) Beneficial effects of mycorrhizal fungi attached to roots of juniper seedlings on plant growth compared to (d) growth of such seedlings in sterilized soil without mycorrhizal fungi.
(c) Mycorrhizal fungi on juniper seedlings in normal soil
Fig. 7-9c, p. 154

46. (d) Lack of mycorrhizal fungi on juniper seedlings in sterilized soil
Figure 7.9
Natural capital: examples of mutualism. (a) Oxpeckers (or tickbirds) feed on parasitic ticks that infest large, thick-skinned animals such as the endangered black rhinoceros. (b) A clownfish gains protection and food by living among deadly stinging sea anemones and helps protect the anemones from some of their predators. (c) Beneficial effects of mycorrhizal fungi attached to roots of juniper seedlings on plant growth compared to (d) growth of such seedlings in sterilized soil without mycorrhizal fungi.
(d) Lack of mycorrhizal fungi on juniper seedlings
in sterilized soil
Fig. 7-9d, p. 154

47. Video: Clownfish with Anemone
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48. Commensalism: Using without Harming
Some species interact in a way that helps one species but has little or no effect on the other.
Figure 7-10

49. ECOLOGICAL SUCCESSION: COMMUNITIES IN TRANSITION
New environmental conditions allow one group of species in a community to replace other groups.
Ecological succession: the gradual change in species composition of a given area
Primary succession: the gradual establishment of biotic communities in lifeless areas where there is no soil or sediment.
Secondary succession: series of communities develop in places containing soil or sediment.

50. Animation: Succession
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51. Primary Succession: Starting from Scratch
Primary succession begins with an essentially lifeless are where there is no soil in a terrestrial ecosystem
Figure 7-11

52. Lichens and mosses Exposed rocks
Balsam fir,
paper birch, and
white spruce
forest community
Figure 7.11
Natural capital: primary ecological succession over several hundred years of plant communities on bare rock exposed by a retreating glacier on Isle Royale, Michigan (USA) in northern Lake Superior. The details vary from one site to another.
Jack pine,
black spruce,
and aspen
Heath mat
Small herbs
and shrubs
Time
Fig. 7-11, p. 156

53. Secondary Succession: Starting Over with Some Help
Secondary succession begins in an area where the natural community has been disturbed.
Figure 7-12

54. Time Mature oak-hickory forest Young pine forest with developing
Figure 7.12
Natural capital: natural ecological restoration of disturbed land. Secondary ecological succession of plant communities on an abandoned farm field in North Carolina (USA). It took 150–200 years after the farmland was abandoned for the area to become covered with a mature oak and hickory forest. A new disturbance such as deforestation or fire would create conditions favoring pioneer species such as annual weeds. In the absence of new disturbances, secondary succession would recur over time, but not necessarily in the same sequence shown here.
Young pine forest
with developing
understory of oak
and hickory trees
Shrubs
and pine
seedlings
Perennial
weeds and
grasses
Annual
weeds
Time
Fig. 7-12, p. 157

55. Can We Predict the Path of Succession, and is Nature in Balance?
The course of succession cannot be precisely predicted.
Previously thought that a stable climax community will always be achieved.
Succession involves species competing for enough light, nutrients and space which will influence it’s trajectory.

56. ECOLOGICAL STABILITY AND SUSTAINABILITY
Living systems maintain some degree of stability through constant change in response to environmental conditions through:
Inertia (persistence): the ability of a living system to resist being disturbed or altered.
Constancy: the ability of a living system to keep its numbers within the limits imposed by available resources.
Resilience: the ability of a living system to bounce back and repair damage after (a not too drastic) disturbance.

57. ECOLOGICAL STABILITY AND SUSTAINABILITY
Having many different species appears to increase the sustainability of many communities.
Human activities are disrupting ecosystem services that support and sustain all life and all economies.

58. Video: Bald Eagles
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59. Video: Bees Pollinating
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60. Video: Cliff Nesters
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61. Video: Eagle Fishing
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62. Video: Grizzly Bear Feeding
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63. Video: Migratory Birds
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64. Video: Owl Hunting
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65. Video: Pelican Colony
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66. Video: Saguaros
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67. Video: Wolf Pack
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