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community interactions.notebook
April 25, 2016
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Community Interactions
An ecological community consists of all the
interacting populations within an ecosystem
Community interactions help to limit the size of
populations
The interacting web of life tends to maintain a
balance between resources and the number of
individuals consuming them
These interactions can also serve as agents of
natural selection
May 2­10:07 AM
Community Interactions
Symbiosis-Literally means living together. It is a close
interaction between organisms of different species
for an extended time.
Mutualism-Symbiosis where both organisms benefit
Parasitism-Symbiosis where one benefits and one is
harmed and sometimes is killed. The parasite lives in
or on the host.
Commensalism-Symbiosis where one benefits and the
other is unharmed.
May 2­10:12 AM
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community interactions.notebook
April 25, 2016
COMMENSALISM
Barnacles live on
whales. they get a
free-ride through the
nutrient-rich water
and do not harm the
whales.
May 2­10:27 AM
This is a guinea worm.
You can drink water
containing water
fleas that have
ingested worm eggs.
The eggs hatch and
the larva live and
grow in you. Then,
when they want to
come out...
PARASITISM
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community interactions.notebook
April 25, 2016
WHY ARE COMMUNITY
INTERACTIONS
IMPORTANT
COMMUNITY INTERACTIONS SERVE AS AN AGENT OF EVOLUTION
WHEN POPULATIONS INTERACT, THEY INFLUENCE EACH OTHERS ABILITY TO SURVIVE AND REPRODUCE
THUS COMMUNITY INTERACTIONS LIMIT POPULATION SIZES AND SHAPE THE BODIES AND BEHAVIORS OF THE INTERACTING POPULATIONS
May 3­9:42 AM
THIS PROCESS IS KNOWN AS CO‐
EVOLUTION
INTERSPECIFIC COMPETITION
COMPETITION AMONG MEMBERS OF DIFFERENT SPECIES
IN THIS SITUATION, EACH SPECIES IS SAID TO BE HARMED BECAUSE ACCESS TO RESOURCES IS REDUCED
THE INTENSITY DEPENDS ON HOW SIMILAR THE REQUIREMENTS OF THE SPECIES ARE
May 8­11:15 AM
ECOLOGICAL NICHE- encompasses
all aspects of an organism's way of
life. The niche includes the physical
home or habitat and the
environmental factors necessary for
survival.
Competitive exclusion principlemembers of different species can
share many aspects of their niches
but no two species occupy the exact
same niche
May 8­11:25 AM
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community interactions.notebook
April 25, 2016
ADAPTATIONS REDUCE THE
OVERLAP OF ECOLOGICAL
NICHES
If two species with the same niche were placed together and forced to compete for limited resources, inevitably one would outcompete the other.
so....what happens in nature?
May 8­11:29 AM
RESOURCE PARTITIONING
When two species with similar requirements coexist, sometimes they occupy a smaller niches than either would by itself.
This reduces the harmful effects of interspecific competition.
It is the outcome of the coevolution of species with extensive but not total niche overlap
May 8­11:38 AM
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