Community Ecology

Community Ecology

Table of Contents

Section 1 Species Interactions

Section 2 Patterns in Communities


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.


Predation

• Predation is an interaction in which one organism (the predator) captures and eats all or part of another individual organism (the prey).

Click below to watch the Visual Concept.

Visual Concept

Predation



Predation, continued

• Predator Adaptations– Predators have adaptations to efficiently capture

prey, whereas prey species have adaptations to avoid capture.



• Adaptations in Animal Prey– Mimicry is an adaptation in which a species gains

an advantage by resembling another species or object.



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

chemical defense.


Visual Concept

Competition



Competition

• Competitive Exclusion– Competition may cause competitive exclusion,

the elimination of one species in a community.

Effect of Competition on Two Species of Barnacles



Visual Concept

Niche



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.


Competition, continued

• Resource Partitioning– Differential resource use to avoid competition is

called resource partitioning.

Warbler Foraging Zones



Symbiosis

• Parasitism– In parasitism, one species (the parasite) feeds

on, but does not always kill, another species (the host).


Visual Concept

Symbiosis



Symbiosis, continued

• Mutualism– In mutualism, both interacting species benefit.


Symbiosis, continued

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

other is not affected.


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.


Species Richness

• Species richness is the number of species in a community.

• Species evenness is the relative abundance of each species.


Species Richness, continued

• Latitude and Species Richness– In general, species richness is greatest near the

equator, and larger areas support more species.



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

promote species richness.



• 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.


Successional Changes in Communities

• Ecological succession is a change in the species composition of a community over time.


Visual Concept

Pioneer Species



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.


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.


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


Education

Community Ecology