Transcript Community Ecology Chapter 56

Biological Communities
• Community: all the organisms that live together in a
specific place
– ______________________
– _______________________
– _______________________
– ______________________
• Communities can be characterized either by their
constituent species or by their properties
– Species richness: the number of species present
– Primary productivity: the amount of energy
produced
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Biological Communities
• Two views of structure and functioning of
communities
– Individualistic concept: H.A. Gleason;
a community is nothing more than an
_____________________________that
happen to occur together at one place
– Holistic concept: F.E. Clements: a
community is an integrated unit;
_______________________________more than the sum of its parts
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Biological Communities
Most ecologists today
favor ______________
_________________
• In communities, species
respond independently
to changing
environmental
conditions
• Community composition
changes gradually
across landscapes
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Biological Communities
• Abundance of tree
species along a moisture
gradient in the Santa
Catalina Mountains of
Southeastern Arizona
• Each line represents the
abundance of a different
tree species
• Community composition
____________________
____________________
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Biological Communities
• Sometimes the
abundance of species
in a community does
change
geographically in a
synchronous pattern
• ________________:
places where the
environment changes
abruptly
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Ecological Niche
• Niche: the total of all the ways an organism uses the
resources of its environment
– _______________________________
– _______________________________
_______________________________
________________________________
• Fundamental niche: the entire niche that a species is
____________________________________, based on
physiological tolerance limits and resource needs
• Realized niche: __________________ set of
environmental conditions, _____________________or
_____________________of other species, in which the
species can establish a stable population
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Billock
Ecological Niche
• Interspecific
competition: occurs __________________
______________________________ and
there is not enough resource to satisfy both
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Ecological Niche
• Other causes of niche
restriction
– ____________________
absence or presence
• Plant species
– Absence of pollinators
– Presence of herbivores
Billock
Billock
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Ecological Niche
Principle of competitive exclusion: ___
__________________________________
__________________________________
__________________________________
__________________________________
• G.F. Gause’s classic experiment on
competitive exclusion using three
Paramecium species shows this principle
in action
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Ecological Niche
• Niche overlap and coexistence
• Competitive exclusion redefined: no two
species can occupy the same niche
indefinitely _________________________
• Species may divide up the resources, this
is called _____________________
• Gause found this occurring with two of his
Paramecium species
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• Resource partitioning
is often seen in
_________________
_________________
that occupy the same
geographic area
• Thought to result from
the process of
_________________
_________________
Resource partitioning
among sympatric
lizard species
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• Character
Ecological Niche
displacement: differences in
morphology evident between sympatric
species
– May play a role in adaptive radiation
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Ecological Niche
• Detection of interspecific competition
can be difficult
– If resources not limited there may be
no competition
– Small versus large population size
– May be environmental conditions that
cause the decline of a species, not
competition
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Ecological Niche
Detecting interspecific competition
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