Transcript chapter_47_powerpoint_l

Chapter 47
Community
Ecology
Community Ecology
Outline
The Concept of the Community
Diversity and Composition Models
The Structure of Communities
Island Biogeography
Habitat and Ecological Niche
Competition Between Populations
Predator-Prey Interactions
Symbiotic Relationships
Community Development
Community Biodiversity
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Community Ecology
Community Concept
An assemblage of populations interacting with
one another within the same environment
Composition is a listing of various species in the
community
Diversity includes both species richness and
species diversity
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Community Structure
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Community Ecology
Diversity and Composition Models
Gleason - Individualistic Model
Each population is there because its abiotic
requirements are met
Clements - Interactive Model
Community is the highest level of organization
Dependent on biotic interactions
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Species Richness of Communities
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Community Ecology
Island Biogeography
MacArthur and Wilson
Developed a general model of island
biogeography
Explains and predicts how the community
diversity of an island is affected by
- Distance from the mainland, and
- Size of the island
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Model of Island Biogeography
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Community Ecology
Community Structure
Competition
When two species compete, the abundance of
both species is negatively impacted
Predation (or parasitism)
- Expected to increase the abundance of the
predator (or parasite)
- And reduce the abundance of the prey (or host)
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Community Ecology
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Habitat and Ecological Niche
Habitat
The area an organism lives and reproduces in
Ecological niche
The role a species plays in its community
- Includes its habitat, and
- Its interactions with other organisms
Fundamental niche - All conditions under which
the organism can survive
Realized niche - Set of conditions under which it
exists in nature
Feeding niches for Wading Birds
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Community Ecology
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Competition Between Populations
Interspecific competition
Members of different species require the same
resource
The supply of the resource is limited
Competitive Exclusion Principle
No two species can occupy the same niche at the
same time
Resource Partitioning decreases competition
Can lead to character displacement
Competition Between
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Two Laboratory Populations of Paramecium
Character Displacement in Finches
on the Galápagos Islands
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Niche Specialization Among
Five Species of Coexisting Warblers
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Competition Between
Two Species of Barnacles
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Community Ecology
Predator-Prey Interactions
Predation
One living organism, the predator, feeds on
another, the prey
- Predator is larger
- Predator has lower reproductive rate
- Prey usually entirely consumed
Presence of predators can decrease prey
densities, and vice-versa
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Predator-prey Interaction Between
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Paramecium caudatum and Didinium nasutum
Predator-prey Interaction
Between a Lynx and a Snowshoe Hare
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Community Ecology
Prey Defenses
Prey defenses
Mechanisms that thwart the possibility of being
eaten by a predator
- Spines
- Tough Epidermis
- Poisonous Chemicals
- Camouflage
- Bright Coloration
- Flocking Behavior
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Camouflage in the Anglerfish
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Anti-predator Defenses
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Community Ecology
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Mimicry
Mimicry
One species resembles another species
Mimicked species possesses an overt
antipredator defense
Batesian Mimicry - Mimic lacks defense of the
organism it resembles
Müllerian Mimicry - Mimic shares same protective
defense
Mimicry Among Insects with
Yellow and Black Stripes
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Community Ecology
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Symbiotic Relationships
Symbiosis
Interactions in which there is a close relationship
between members of two species
Parasitism
- Parasite derives nourishment from a host, and may
use host as habitat and mode of transmission
 Endoparasites
 Ectoparasites
The Life Cycle of a Deer Tick
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Community Ecology
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Commensalism
Symbiosis, cont.
Commensalism
- A symbiotic relationship in which one species
benefits and the other is indifferent
 Remoras
and Sharks
- Many supposed examples may turn out to be
mutualism or parasitism
- Inferred amount of harm or benefit two species do
to one another is subject to investigator bias
Clownfish Among
Sea Anemone’s Tentacles
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Community Ecology
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Mutualism
Symbiosis, cont.
Mutualism
- A symbiotic relationship in which both members of
the association benefit
- Need not be equally beneficial to both species
 Cleaning
Symbiosis
- Often help each other obtain food or avoid
predation
 Bacteria
in human intestinal tract
Mutualism Between
the Bullhorn Acacia Tree and Ants
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Cleaning Symbiosis
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Community Ecology
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Community Development
Ecological Succession
A predictable pattern of change in species
replacements following a disturbance
- Primary Succession occurs in areas where there is
no soil formation
- Secondary Succession begins in areas where soil
is present
 Pioneer
Species
Secondary Succession
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Secondary Succession
in a Forest
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Community Ecology
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Succession Models
Facilitation Model
Each stage facilitates invasion and replacement
by organisms of the next stage
Succession in a particular area will always lead to
the same type of community
Climax Community
Community Ecology
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Succession Models
Inhibition Model
Colonists remain and inhibit growth of other
plants until the colonists are damaged or die
Tolerance Model
Different types of plants can colonize an area at
the same time
Chance determine which seeds arrive first
Community Ecology
Community Diversity
Community stability can be recognized in three
ways
Persistence through time
Resistance to change
Recovery once a disturbance has occurred
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Community Ecology
Intermediate Disturbance Hypothesis
If widespread disturbances occur frequently,
diversity will be limited
If diversity is high, only moderate disturbances
have been occurring with moderate frequency
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The Intermediate Disturbance Hypothesis 39
Community Ecology
Predation, Competition, and Biodiversity
Predation by a particular species may reduce
competition and increases diversity
Such predators are referred to as keystone
predators
Exotic species
May lead to unbridled competition
Resultant reduction in biodiversity
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Effect of a Keystone Species
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Community Ecology
Review
The Concept of the Community
Diversity and Composition Models
The Structure of Communities
Island Biogeography
Habitat and Ecological Niche
Competition Between Populations
Predator-Prey Interactions
Symbiotic Relationships
Community Development
Community Biodiversity
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Ending Slide Chapter 47
Community
Ecology