Biology, Seventh Edition
Solomon • Berg • Martin
Chapter 52
Community Ecology
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 52 Community Ecology
• Ecological niche
• Distinctive lifestyle and role of an
organism in a community
• Takes into account all abiotic and
biotic aspects
• For example, an organism’s habitat
is one parameter used to describe
the niche
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 52 Community Ecology
Connections to the size of the acorn crop
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 52 Community Ecology
• Fundamental niche
• Potential ecological niche for an
organism
• Realized niche
• Niche an organism actually
occupies
• Limiting resources
• Environmental factors that restrict a
realized niche
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Biology, Seventh Edition
CHAPTER 52 Community Ecology
Effect of competition on an organism’s
realized niche
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Biology, Seventh Edition
CHAPTER 52 Community Ecology
• Competition
• Two or more individuals attempting
to use the same resource
• Intraspecific competition
–Among individuals within a population
• Interspecific competition
–Between different species
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Biology, Seventh Edition
CHAPTER 52 Community Ecology
Interspecific
competition
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 52 Community Ecology
• Competitive exclusion principle
• Two species cannot occupy the
same niche in the same community
for an indefinite period
• One species is excluded by
another as a result of competition
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 52 Community Ecology
• Some species reduce competition
by resource partitioning
• Competition among species is
reduced by character
displacement
• Structural ecological and
behavioral characteristics diverge
where ranges overlap
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Biology, Seventh Edition
CHAPTER 52 Community Ecology
Resource
partitioning
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Biology, Seventh Edition
CHAPTER 52 Community Ecology
• Predation
• Consumption of one species (the
prey) by another (the predator)
• Coevolution
• Predator and prey both evolve
more efficient ways to interact
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Biology, Seventh Edition
CHAPTER 52 Community Ecology
Ecological interactions among species
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Biology, Seventh Edition
CHAPTER 52 Community Ecology
• Defenses
• Mechanical defenses
• Associating in groups
• Cryptic coloration
• Warning coloration
• Müllerian mimicry
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Biology, Seventh Edition
CHAPTER 52 Community Ecology
Cryptic
coloration
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Biology, Seventh Edition
CHAPTER 52 Community Ecology
• Symbiosis
• Mutualism
–Both partners benefit
• Commensalism
–One partner benefits and the other is
unaffected
• Parasitism
–One partner benefits while the other is
harmed
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Biology, Seventh Edition
CHAPTER 52 Community Ecology
Mutualism
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Biology, Seventh Edition
CHAPTER 52 Community Ecology
Commensalism
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Biology, Seventh Edition
CHAPTER 52 Community Ecology
Parasitism
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Biology, Seventh Edition
CHAPTER 52 Community Ecology
• Keynote species
• Present in small numbers but are
crucial in determining the species
composition and ecosystem
functioning
• Dominant species
• Affect the community because they
are so common
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 52 Community Ecology
• Species richness
• Number of species within a
community
• Species diversity
• Relative importance of each
species within a community
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Biology, Seventh Edition
CHAPTER 52 Community Ecology
Effect of community complexity on
species richness
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Biology, Seventh Edition
CHAPTER 52 Community Ecology
• Ecological succession
• Primary succession
–Occurs in an area not previously
inhabited
• Secondary succession
–Occurs where there is a pre-existing
community and well-formed soil
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Biology, Seventh Edition
CHAPTER 52 Community Ecology
• Intermediate disturbance
hypothesis
• Disturbance affects succession and
species richness
• Species richness is greatest at
moderate levels of disturbance
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Biology, Seventh Edition
CHAPTER 52 Community Ecology
Intermediate disturbance hypothesis
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition
CHAPTER 52 Community Ecology
• The nature of communities
• Organismic model
–Views a community as a
superorganism that goes through
stages of development (succession)
• Individualistic model
–Abiotic environmental factors are
primary determinants of species
composition
–Organisms are independent
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