1. Chapter 8
Community Ecology
Importance of Biodiversity

2. Question of the Day
The best example of a tertiary consumer would be a/an
mouse
grasshopper
sheep
cactus
coyote

3. How does community structure affect species diversity?
Section 8-1
Community Structure &
Species Diversity
Question to Consider
How does community structure affect species diversity?

4. COMMUNITY STRUCTURE
Figure 7.2
Natural capital: generalized types, relative sizes, and stratification of plant species in various terrestrial communities.
Biological communities differ in their structure and physical appearance.
Figure 8-2

5. Physical Characteristics
Physical appearance: the relative sizes, stratification, and distribution of its populations and species
Transition occurs around the edges, where two community types interact.
Increased edge area may be harmful due to habitat fragmentation; many species become more vulnerable to predators and loss of colonization ability.

6. Species Diversity
Biological communities differ in the types and numbers of species they contain and the ecological roles those species play.
Species diversity: the number of different species it contains (species richness) combined with the abundance of individuals within each of those species (species evenness).

7. 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.

8. Species Diversity on Islands
MacArthur and Wilson proposed the species equilibrium model or theory of island biogeography in the 1960’s.
Model projects that at some point the rates of immigration and extinction should reach an equilibrium based on:
Island size
Distance to nearest mainland
Why?
Conserving Biodiversity

9. How does a species’ role affect biological communities?
Section 8-2
Types of Species
Question to Consider
How does a species’ role affect biological communities?

10. Question of the Day
Q: Which of the following best illustrates the concept of the tragedy of the commons?
A. Destruction of landscape by surface mining on private land
B. Selective harvesting of trees by a timber company in a national forest
C. Legislation of catch limits to avoid depletion of fish stocks in a shared lake
D. Inadvertent destruction of beneficial species while attempting to control pests
E. Depletion of an aquifer by regional farmers

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.
Kudzu

12. 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.

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

14. 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.

15. Case Study: Why are Amphibians Vanishing?
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.
Frogs serve as indicator species because different parts of their life cycles can be easily disturbed.
Figure 8-3

16. Adult frog (3 years) Young frog Sperm Tadpole develops into frog
Sexual
Reproduction
Tadpole
Eggs
Fertilized egg
development
Egg hatches
Organ formation
Fig. 7-3, p. 147

17. 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.

18. Species Interactions: Competition & Predation
Section 8-3
Species Interactions:
Competition & Predation
Lion vs. Wildebeest

19. Question of the Day
Which of the following is the best example of a keystone species?
Sea otter
Sea urchin
Spotted owl
Snail darter
E. Condor

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

21. Competition: Resource Partitioning
Each species minimizes competition with the others for food by
1. Spending at least half its feeding time in a distinct portion of the spruce tree and
2. By consuming somewhat different insect species.
Figure 7-7

22. Competition: Niche Specialization
Niches become separated to avoid competition for resources
Grizzlies & Wolves
Figure 7.6
Natural capital: resource partitioning and niche specialization as a result of competition between two species. The top diagram shows the overlapping niches of two competing species. The bottom diagram shows that through natural selection the niches of the two species become separated and more specialized (narrower) so they avoid competing for the same resources.
Figure 7-6

23. PREDATION Species called predators feed on other species called prey.
Organisms use their senses 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.

24. Prey adaptations 1. Some prey escape their predators
Cheetah vs. Gazelle
2. Have outer protection
3. Some are camouflaged
4. Some use chemicals to repel predators.
Figure 7-8

25. (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

26. (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

27. (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

28. (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

29. (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

30. (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

31. (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

32. 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

33. Section 8-3
Summary
Competition
Predation

34. SPECIES INTERACTIONS: PARASITISM, MUTUALISM, AND COMMENSALIM
Section 8-4
SPECIES INTERACTIONS: PARASITISM, MUTUALISM, AND COMMENSALIM
Tongue Eaters

35. Question of the Day Zero population growth is associated with
Phase I only
Phase II only
Phase III only
Phase IV only
Phase I and IV

36. 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.

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

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

39. (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

40. (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

41. (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

42. (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

43. 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

44. Section 8-4 Summary
Parasitism
Mutualism
Commensalism

45. Ecological Succession & Stability
Section 8-5 & 8-6
Ecological Succession
& Stability
Essential Question:
How do communities undergo natural change?
Mt St Helens

46. Question of the Day
Which of the following elements is most likely to limit primary production in freshwater lakes?
A. Oxygen
B. Calcium
C. Phosphorus
D. Carbon
E. Iron

47. 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.

48. Primary Succession: Starting from Scratch
Primary succession begins with an essentially lifeless area, where there is no soil in a terrestrial ecosystem
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.
Figure 7-11

49. Typical Changes
Community changes during succession include increases in species diversity and changes in species composition
Characteristics of Pioneer Species:
Ecosystem changes during succession include increases in biomass, primary production, respiration, and nutrient retention.
Modification of soil and other environmental changes lead to changes in species.

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

51. Can We Predict the Path of Succession
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.

52. 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.

53. 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.

54. Chapter Overview Questions
What determines the number of species in a community?
How can we classify species according to their roles in a community?
How do species interact with one another?
How do communities respond to changes in environmental conditions?
Does high species biodiversity increase the stability and sustainability of a community?