Community EcologyChapter 54

Community

• An assemblage of populations of various species living close enough for potential interactions

Learning Targets

• I can describe the following interspecific interactions and explain how they impact the community:• Competition

• Competitive exclusionary avoidance through: resource partitioning, fundamental and realized niches, character displacement

• Predation • Predation effects: aposematic coloration, cryptic coloration, Batesian and Mullerian mimicry

• Herbivory• Symbiosis

• Distinguishing between: parasitic, commensal, mutualistic

• Facilitation• I can quantitatively demonstrate the diversity of a community.• I can explain the relationship between community diversity and stability, including the impact keystone and

dominant species have on stability.• I can describe how disturbance can impact a community.

• I can explain how ecological succession works• I can distinguish between primary and secondary succession• I can describe a climax community.

• I can describe how human and natural disturbances can alter succession.

Types of Interactions

• Interspecific Interactions• Interactions with other species

• Intraspecific Interactions• Interactions within one species

Ecological Niche• Every species survives and reproduces utilizing a range of

chemical and biological conditions

Competitive Exclusion Principle• Direct interspecific competition will always lead to the

extinction of one species• One species will have a slight competitive edge in surviving

and reproducing

Interspecific Species Interactions

Predation (+/-)

Predation Defense Strategies

• Cryptic coloration – camouflage • Aposematic coloration – warning coloration• Batesian mimicry – a harmless species mimics a harmful

one• Mullerian mimicry – two harmful species mimic each

other

(a) Cryptic coloration (b) Aposematic coloration

Canyon tree frog Poison dart frog

(c) Batesian mimicry: A harmless species mimics a harmful one. (d) Müllerian mimicry: Two unpalatable species mimic each other.

HawkmothLarva (harmless) Cuckoo bee

Yellow jacket

Green parrot snake (harmful)

Herbivory (+/-)

Parasitism (+/-)

Commensalism (+/0)

Mutualism (+/+)

Facilitation (+/+ or 0/+)• One species influences the survival and reproduction of

another species• Ex: plant species that make soil hospitable for other

species to thrive

Learning Targets

• I can describe the following interspecific interactions and explain how they impact the community:• Competition

• Competitive exclusionary avoidance through: resource partitioning, fundamental and realized niches, character displacement

• Predation • Predation effects: aposematic coloration, cryptic coloration, Batesian and Mullerian mimicry

• Herbivory• Symbiosis

• Distinguishing between: parasitic, commensal, mutualistic

• Facilitation• I can quantitatively demonstrate the diversity of a community.• I can explain the relationship between community diversity and stability, including the impact keystone and

dominant species have on stability.• I can describe how disturbance can impact a community.

• I can explain how ecological succession works• I can distinguish between primary and secondary succession• I can describe a climax community.

• I can describe how human and natural disturbances can alter succession.

Species Diversity

• Species richness: • Total amount of species in a community

• Relative abundance:• Total amount of one species in a community

• Diversity is key to a healthy, stable ecosystem

Learning Targets

• I can describe the following interspecific interactions and explain how they impact the community:• Competition

• Competitive exclusionary avoidance through: resource partitioning, fundamental and realized niches, character displacement

• Predation • Predation effects: aposematic coloration, cryptic coloration, Batesian and Mullerian mimicry

• Herbivory• Symbiosis

• Distinguishing between: parasitic, commensal, mutualistic

• Facilitation• I can quantitatively demonstrate the diversity of a community.• I can explain the relationship between community diversity and stability, including the impact keystone and

dominant species have on stability.• I can describe how disturbance can impact a community.

• I can explain how ecological succession works• I can distinguish between primary and secondary succession• I can describe a climax community.

• I can describe how human and natural disturbances can alter succession.

Keystone Species• Organism with a pivotal role in an ecosystem• The removal of a keystone species results in the collapse of

the ecosystem• Ex: sea otter (Enhydra lutris)

Learning Targets

• I can describe the following interspecific interactions and explain how they impact the community:• Competition

• Competitive exclusionary avoidance through: resource partitioning, fundamental and realized niches, character displacement

• Predation • Predation effects: aposematic coloration, cryptic coloration, Batesian and Mullerian mimicry

• Herbivory• Symbiosis

• Distinguishing between: parasitic, commensal, mutualistic

• Facilitation• I can quantitatively demonstrate the diversity of a community.• I can explain the relationship between community diversity and stability, including the impact keystone and

dominant species have on stability.• I can describe how disturbance can impact a community.

• I can explain how ecological succession works.• I can distinguish between primary and secondary succession.• I can describe a climax community.

• I can describe how human and natural disturbances can alter succession.

Disturbance & Succession

• Disturbance – event that changes the dynamics of a community

• Succession – recovery of that community after a disturbance

Primary vs. Secondary Succession• Primary – begins with rock• Ex: glacier, volcano

• Secondary – begins with soil• Ex: forest fire, flood

• Climax community – recovered, long term stability

Learning Targets

• I can describe the following interspecific interactions and explain how they impact the community:• Competition

• Competitive exclusionary avoidance through: resource partitioning, fundamental and realized niches, character displacement

• Predation • Predation effects: aposematic coloration, cryptic coloration, Batesian and Mullerian mimicry

• Herbivory• Symbiosis

• Distinguishing between: parasitic, commensal, mutualistic

• Facilitation• I can quantitatively demonstrate the diversity of a community.• I can explain the relationship between community diversity and stability, including the impact keystone and

dominant species have on stability.• I can describe how disturbance can impact a community.

• I can explain how ecological succession works• I can distinguish between primary and secondary succession• I can describe a climax community.

• I can describe how human and natural disturbances can alter succession.

Human vs. Natural Disturbance

• Humans – clearing land for own uses• Ex: logging,

agriculture• Generally, no recovery

to climax community