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Community EcologyChapter 20
Table of Contents
Section 1 Species Interactions
Section 2 Patterns in Communities
Section 1 Species InteractionsChapter 20
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.
Section 1 Species InteractionsChapter 20
Predation
• Predation is an interaction in which one organism (the predator) captures and eats all or part of another individual organism (the prey).
Chapter 20
Click below to watch the Visual Concept.
Visual Concept
Predation
Section 1 Species Interactions
Section 1 Species InteractionsChapter 20
Predation, continued
• Predator Adaptations– Predators have adaptations to efficiently capture
prey, whereas prey species have adaptations to avoid capture.
Section 1 Species InteractionsChapter 20
Predation, continued
• Adaptations in Animal Prey– Mimicry is an adaptation in which a species gains
an advantage by resembling another species or object.
Section 1 Species InteractionsChapter 20
Predation, continued
• Adaptations in Plant Prey– Many plants produce secondary compounds as a
chemical defense.
Chapter 20
Click below to watch the Visual Concept.
Visual Concept
Competition
Section 1 Species Interactions
Section 1 Species InteractionsChapter 20
Competition
• Competitive Exclusion– Competition may cause competitive exclusion,
the elimination of one species in a community.
Chapter 20
Effect of Competition on Two Species of Barnacles
Section 1 Species Interactions
Chapter 20
Click below to watch the Visual Concept.
Visual Concept
Niche
Section 1 Species Interactions
Section 1 Species InteractionsChapter 20
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.
Section 1 Species InteractionsChapter 20
Competition, continued
• Resource Partitioning– Differential resource use to avoid competition is
called resource partitioning.
Chapter 20
Warbler Foraging Zones
Section 1 Species Interactions
Section 1 Species InteractionsChapter 20
Symbiosis
• Parasitism– In parasitism, one species (the parasite) feeds
on, but does not always kill, another species (the host).
Chapter 20
Click below to watch the Visual Concept.
Visual Concept
Symbiosis
Section 1 Species Interactions
Section 1 Species InteractionsChapter 20
Symbiosis, continued
• Mutualism– In mutualism, both interacting species benefit.
Section 1 Species InteractionsChapter 20
Symbiosis, continued
• Commensalism– In commensalism, one species benefits, and the
other is not affected.
Section 2 Patterns in CommunitiesChapter 20
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.
Section 2 Patterns in CommunitiesChapter 20
Species Richness
• Species richness is the number of species in a community.
• Species evenness is the relative abundance of each species.
Section 2 Patterns in CommunitiesChapter 20
Species Richness, continued
• Latitude and Species Richness– In general, species richness is greatest near the
equator, and larger areas support more species.
Section 2 Patterns in CommunitiesChapter 20
Species Richness, continued
• Species Interactions and Species Richness– Species interactions such as predation can
promote species richness.
Section 2 Patterns in CommunitiesChapter 20
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.
Section 2 Patterns in CommunitiesChapter 20
Successional Changes in Communities
• Ecological succession is a change in the species composition of a community over time.
Chapter 20
Click below to watch the Visual Concept.
Visual Concept
Pioneer Species
Section 2 Patterns in Communities
Section 2 Patterns in CommunitiesChapter 20
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.
Section 2 Patterns in CommunitiesChapter 20
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.
Section 2 Patterns in CommunitiesChapter 20
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.
Chapter 20
Ecological Succession at Glacier Bay
Section 2 Patterns in Communities