Community Ecology

Community Ecology

Table of Contents

Section 1 Species Interactions

Section 2 Patterns in Communities

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.

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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Visual Concept

Predation

Section 1 Species Interactions

Section 1 Species Interactions

Predation, continued

• Predator Adaptations– Predators have adaptations to efficiently capture

prey, whereas prey species have adaptations to avoid capture.

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.

Section 1 Species Interactions

Predation, continued

• Adaptations in Plant Prey– Many plants produce secondary compounds as a

chemical defense.

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Visual Concept

Competition

Section 1 Species Interactions

Section 1 Species Interactions

Competition

• Competitive Exclusion– Competition may cause competitive exclusion,

the elimination of one species in a community.

Effect of Competition on Two Species of Barnacles

Section 1 Species Interactions

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Visual Concept

Niche

Section 1 Species Interactions

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.

Section 1 Species Interactions

Competition, continued

• Resource Partitioning– Differential resource use to avoid competition is

called resource partitioning.

Warbler Foraging Zones

Section 1 Species Interactions

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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Visual Concept

Symbiosis

Section 1 Species Interactions

Section 1 Species Interactions

Symbiosis, continued

• Mutualism– In mutualism, both interacting species benefit.

Section 1 Species Interactions

Symbiosis, continued

• Commensalism– In commensalism, one species benefits, and the

other is not affected.

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.

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.

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.

Section 2 Patterns in Communities

Species Richness, continued

• Species Interactions and Species Richness– Species interactions such as predation can

promote species richness.

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.

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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Visual Concept

Pioneer Species

Section 2 Patterns in Communities

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.

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.

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.

Ecological Succession at Glacier Bay

Section 2 Patterns in Communities