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Resources
Chapter Presentation
Transparencies
Visual Concepts
Standardized Test Prep
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Chapter 20
Community Ecology
Table of Contents
Section 1 Species Interactions
Section 2 Patterns in Communities
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Chapter 20
Section 1 Species Interactions
Objectives
• Identify two types of predator adaptations and two
types of prey adaptations.
• Identify possible causes and results of interspecific
competition.
• Compare parasitism, mutualism, and commensalism,
and give one example of each.
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Chapter 20
Section 1 Species Interactions
Predation
• Predation is an interaction in which one organism
(the predator) captures and eats all or part of another
individual organism (the prey).
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Chapter 20
Section 1 Species Interactions
Predation
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Chapter 20
Section 1 Species Interactions
Predation, continued
• Predator Adaptations
– Predators have adaptations to efficiently capture
prey, whereas prey species have adaptations to
avoid capture.
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Chapter 20
Section 1 Species Interactions
Predation, continued
• Adaptations in Animal Prey
– Mimicry is an adaptation in which a species gains
an advantage by resembling another species or
object.
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Chapter 20
Section 1 Species Interactions
Predation, continued
• Adaptations in Plant Prey
– Many plants produce secondary compounds as a
chemical defense.
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Chapter 20
Section 1 Species Interactions
Competition
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Chapter 20
Section 1 Species Interactions
Competition
• Competitive Exclusion
– Competition may cause competitive exclusion,
the elimination of one species in a community.
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Chapter 20
Section 1 Species Interactions
Effect of Competition on Two Species of
Barnacles
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Chapter 20
Section 1 Species Interactions
Niche
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Chapter 20
Section 1 Species Interactions
Competition, continued
• Character Displacement
– Competition may drive the evolution of niche
differences among competitors. This evolution of
differences in a characteristic due to competition is
called character displacement.
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Chapter 20
Section 1 Species Interactions
Competition, continued
• Resource Partitioning
– Differential resource use to avoid competition is
called resource partitioning.
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Chapter 20
Section 1 Species Interactions
Warbler Foraging
Zones
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Chapter 20
Section 1 Species Interactions
Symbiosis
• Parasitism
– In parasitism, one species (the parasite) feeds
on, but does not always kill, another species (the
host).
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Chapter 20
Section 1 Species Interactions
Symbiosis
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Chapter 20
Section 1 Species Interactions
Symbiosis, continued
• Mutualism
– In mutualism, both interacting species benefit.
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Chapter 20
Section 1 Species Interactions
Symbiosis, continued
• Commensalism
– In commensalism, one species benefits, and the
other is not affected.
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Chapter 20
Section 2 Patterns in Communities
Objectives
• Describe the factors that affect species richness in a
community.
• Explain how disturbances affect community stability.
• Distinguish between types of succession, and
explain why succession may not be predictable.
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Chapter 20
Section 2 Patterns in Communities
Species Richness
• Species richness is the number of species in a
community.
• Species evenness is the relative abundance of each
species.
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Chapter 20
Section 2 Patterns in Communities
Species Richness, continued
• Latitude and Species Richness
– In general, species richness is greatest near the
equator, and larger areas support more species.
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Chapter 20
Section 2 Patterns in Communities
Species Richness, continued
• Species Interactions and Species Richness
– Species interactions such as predation can
promote species richness.
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Chapter 20
Section 2 Patterns in Communities
Species Richness, continued
• Community Stability and Species Richness
– Disturbances can alter a community by
eliminating or removing organisms or altering
resource availability.
– Species richness may improve a community’s
stability.
– Areas of low species richness may be less stable
in the event of an ecological disturbance.
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Chapter 20
Section 2 Patterns in Communities
Successional Changes in Communities
• Ecological succession is a change in the species
composition of a community over time.
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Chapter 20
Section 2 Patterns in Communities
Pioneer Species
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Chapter 20
Section 2 Patterns in Communities
Successional Changes in Communities,
continued
• Primary Succession
– Primary succession is the assembly of a
community on newly created habitat.
– Primary succession occurs in areas that have
been recently exposed to the elements and lack
soil.
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Chapter 20
Section 2 Patterns in Communities
Successional Changes in Communities,
continued
• Secondary Succession
– Secondary succession is the change in an
existing community following a disturbance.
– Secondary succession occurs in areas where the
original ecosystem has been cleared by a
disturbance.
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Chapter 20
Section 2 Patterns in Communities
The Complexity of Succession
• The traditional description of succession is that the
community proceeds through a predictable series of
stages until it reaches a stable end point, called the
climax community.
• Primary succession typically proceeds from lichens
and mosses to a climax community.
• Secondary succession typically proceeds from weeds
to a climax community.
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Chapter 20
Section 2 Patterns in Communities
Ecological Succession at Glacier Bay
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Chapter 20
Section 2 Patterns in Communities
Ecological Succession
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Chapter 20
Standardized Test Prep
Multiple Choice
1. A certain tropical tree has a fruit that is eaten by only
one species of bats. As the bat digests the fruit, the
seeds are made ready to sprout. When the bat
excretes the wastes of the fruit, it drops seeds in new
locations. Which of the following is the correct term
for the relationship between the bat and the tree?
A. predation
B. mutualism
C. competition
D. commensalism
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Chapter 20
Standardized Test Prep
Multiple Choice, continued
1. A certain tropical tree has a fruit that is eaten by only
one species of bats. As the bat digests the fruit, the
seeds are made ready to sprout. When the bat
excretes the wastes of the fruit, it drops seeds in new
locations. Which of the following is the correct term
for the relationship between the bat and the tree?
A. predation
B. mutualism
C. competition
D. commensalism
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Chapter 20
Standardized Test Prep
Multiple Choice, continued
2. Which of the following is a parasite?
F. a lion hunting a zebra
G. a deer grazing on grass
H. a tick sucking blood from a dog
J. a snake swallowing a bird’s egg
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Chapter 20
Standardized Test Prep
Multiple Choice, continued
2. Which of the following is a parasite?
F. a lion hunting a zebra
G. a deer grazing on grass
H. a tick sucking blood from a dog
J. a snake swallowing a bird’s egg
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Chapter 20
Standardized Test Prep
Multiple Choice, continued
3. Three species of birds forage for insects in the same
tree. However, each species tends to forage in
different parts of the tree. This pattern of foraging is
best explained as an adaptation to which of the
following relationships?
A. predation
B. mutualism
C. competition
D. commensalism
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Chapter 20
Standardized Test Prep
Multiple Choice, continued
3. Three species of birds forage for insects in the same
tree. However, each species tends to forage in
different parts of the tree. This pattern of foraging is
best explained as an adaptation to which of the
following relationships?
A. predation
B. mutualism
C. competition
D. commensalism
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Chapter 20
Standardized Test Prep
Multiple Choice, continued
Use the map below to answer question 4. The map
shows two islands.
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Chapter 20
Standardized Test Prep
Multiple Choice, continued
4. What can you infer about the number of species on
each of these islands?
F. Island A has more species.
G. Island B has more species.
H. Island A and Island B will have the same number
of species.
J. Both islands will have fewer species than islands
that are located farther north.
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Chapter 20
Standardized Test Prep
Multiple Choice, continued
4. What can you infer about the number of species on
each of these islands?
F. Island A has more species.
G. Island B has more species.
H. Island A and Island B will have the same number
of species.
J. Both islands will have fewer species than islands
that are located farther north.
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Chapter 20
Standardized Test Prep
Multiple Choice, continued
Complete the following analogy:
5. predator : prey :: herbivore :
A. carnivore
B. plant
C. parasite
D. predation
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Chapter 20
Standardized Test Prep
Multiple Choice, continued
Complete the following analogy:
5. predator : prey :: herbivore :
A. carnivore
B. plant
C. parasite
D. predation
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Chapter 20
Standardized Test Prep
Multiple Choice, continued
Use the graph below to answer question 6. The shading
in the graph indicates the frequency with which a
certain bird species obtains prey, by prey size and
location.
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Chapter 20
Standardized Test Prep
Multiple Choice, continued
6. Which of the following statements is best supported
by this graph?
F. Most often, the bird eats insects.
G. Most often, the bird nests above ground.
H. Most often, the bird finds prey at ground level.
J. Most often, the bird eats prey that is between 3
and 5 mm long.
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Chapter 20
Standardized Test Prep
Multiple Choice, continued
6. Which of the following statements is best supported
by this graph?
F. Most often, the bird eats insects.
G. Most often, the bird nests above ground.
H. Most often, the bird finds prey at ground level.
J. Most often, the bird eats prey that is between 3
and 5 mm long.
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Chapter 20
Standardized Test Prep
Short Response
Some plants produce chemicals that are irritating or
poisonous to some animals.
Explain the role of these adaptations in an
ecological community.
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Chapter 20
Standardized Test Prep
Short Response, continued
Some plants produce chemicals that are irritating or
poisonous to some animals.
Explain the role of these adaptations in an
ecological community.
Answer: Secondary compounds are defensive
chemicals synthesized by plants to prevent
plants from being eaten. Strychnine and nicotine
are two examples.
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Chapter 20
Standardized Test Prep
Extended Response
Base your answers to parts A & B on the
information below.
The gradual, sequential change in species in an
area is called ecological succession.
Part A Describe the stages of primary succession.
Part B Compare primary succession and secondary
succession.
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Chapter 20
Standardized Test Prep
Extended Response, continued
Answer:
Part A Primary succession starts with the exposure of bare
land. Lichens colonize the rock. Decaying lichens as well
as minerals from the rock lead to soil formation. Soil leads
to colonization by pioneer species, such as moss and
weeds. Large plants, such as shrubs and trees, replace
pioneer species. Various trees become dominant, and
succession ends with a mature forest.
Part B Primary succession occurs when bare rock is
exposed by geological events, such as island formation or
glacier retreat. Secondary succession occurs after a
disturbance clears away an existing community, but the
soil remains intact.
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