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Community Ecology
Interactions within
communities of organisms
Outline
1. Key concepts
2. Ecosystems and communities
3. Competition, Predation,
Commensalism, Mutualism,
4. Key Terms
5. Conclusions
Key Concepts:
1.
A habitat is the type of place where individuals of a species
normally live
2.
A community is defined as an assemblage of species living
close enough together for potential interaction.
3.
Every species in the community has its own niche
4.
Interactions among species influence the structure of a
community
Dominant species are those in a community that have the
highest abundance or highest biomass (the sum weight of all
individuals in a population).
5.
6.
Keystone species exert an important regulating effect on other
species in a community.
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Ecosystems and
communities
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Ecosystem: all factors affecting an organism’s
survival: abiotic and biotic
Individuals of a species form populations living
in a given habitat
Several populations interact to form
communities within a habitat
Many communities + abiotic factors form an
ecosystem
Everything interacts!
Each organism plays a
special role within a
community
Competition
Predation
Commensalism
Mutualism
Competition
Interspecific competition for resources can
occur when resources are in short supply.
There is potential for competition between
any two species that need the same limited
resource.
The competitive exclusion principle: two
species with similar needs for same
limiting resources cannot coexist in the
same place.
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The ecological niche is the sum total of
an organism’s use of abiotic/biotic
resources in the environment.
An organism’s niche is its role in
the environment.
The competitive exclusion principle
can be restated to say that two species
cannot coexist in a community if their
niches are identical.
Competition
Resource Partitioning
Three annual plants in a plowed field
All require water
and minerals
but differ in
adaptations
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Niches and
competition
Predation
A predator eats prey.
Herbivory, in which animals eat plants.
In parasitism, predators live on/in a host and
depend on the host for nutrition.
Predator adaptations: many important feeding
adaptations of predators are both obvious
and familiar.
Claws, teeth, poison, speed, and agility.
Predation
Plant defenses against herbivores include
chemical compounds that are toxic.
Animal defenses against predators.
Behavioral defenses include fleeing, hiding,
self-defense, etc
Camouflage
Mechanical defenses include spines.
Chemical defenses include odors and toxins
Coloration is indicated by warning colors, and is
sometimes associated with other defenses (toxins).
Mimicry is when organisms resemble other
species.
4
Parasites and pathogens as predators.
A parasite derives nourishment from a
host, which is harmed in the process.
Endoparasites live inside the host and
ectoparasites live on the surface of the
host.
Pathogens are disease-causing organisms
that can be considered predators.
Predation
Ecosystem and Community
Lions and their preys
Camouflage
Biston
betularia
Color
Adaptation
Contrast
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Camouflage
Commensalism
Commensalism: an organism of one species
benefits from its interactions with another;
the other species neither benefits nor is
harmed
EX: epiphytes; barnacles; clownfish and
anemones
Mutualism
A relationship where two species live
together in close association, with benefits
for both
Frequently one species gets protection
and/or support while the other gets food or a
home or transportation
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Mutualism
Interspecific interactions
Dominant species are those in a
community that have the highest
abundance or highest biomass (the
sum weight of all individuals in a
population).
Keystone species exert an important
regulating effect on other species in
a community.
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Predation
Parasitism
Mutualism
Competition
Competitive exclusion
Mimicry
Niche
Camouflage
Community
Dominant species
Keystone species
In Conclusion
1. A habitat is the type of place where individuals of
a given species normally live
2. Each species has its own niche in the community
3.
Mutualism, commensalism, competition, and
predation are species interactions that directly or
indirectly link the populations in a community
4.
Species that require the same limited resource
tend to compete
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In Conclusion
5. Predator adaptations: Claws, teeth, poison, speed,
and agility.
6. Parasites and pathogens as predators.
7. Commensalism: an organism of one species
benefits from its interactions with another; the
other species neither benefits nor is harmed
8. Mutualism: A relationship where two species live
together in close association, with benefits for both
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