1 Important Points Midterm 2 is Tuesday the 3 rd (this coming Tuesday)
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Important PointsMidterm 2 is Tuesday the 3rd (this coming Tuesday)
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Main Points1) Factors controlling population growth and size
2) Top-down versus bottom-up regulation of populations--Serengeti example--the phenomenon of migration--northern BC example
3) Competition--intra vs. interspecific--apparent vs. exploitative vs. interference--ecological vs. evolutionary effects--null models and limitations of experiments
4) Terms: Allee effect, apparent competition, experiment (press vs. pulse), fundamental niche, realized niche
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Population Growth Review
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Negative vs. Positive Density-Dependence
population size
# ki
ds s
urvi
ving
/ in
d
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Negative vs. Positive Density-Dependence
population size
# ki
ds s
urvi
ving
/ in
d
population size
6
Negative vs. Positive Density-Dependence
population size
Allee effect = positive correlation between populationdensity and the per capita rate of population growth
# ki
ds s
urvi
ving
/ in
d
population size
7
Density-Dependent Factors 1) Competition
2) Predation
3) Disease/Parasites
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Density-Dependent Factors 1) Competition
2) Predation
3) Disease/Parasites
Density-Independent
1) Natural disasters
(rain, drought, etc.)
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Experiments in EcologyExperiment = a test under controlled conditions
made to examine the validity of a hypothesis.
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Experiments in EcologyExperiment = a test under controlled conditions
made to examine the validity of a hypothesis.
Pulse experiment = manipulation is applied once, then the response of the system (e.g., abundance, distribution, diversity) is measured.
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Experiments in EcologyExperiment = a test under controlled conditions
made to examine the validity of a hypothesis.
Press experiment = manipulation is applied continually, then the response of the system (e.g., abundance, distribution, diversity) is measured.
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Top-down versus bottom-up control
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Top-down versus bottom-up control• Example: increased mortality of Serengeti ungulates (Sinclair et
al. 2003)
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Top-down versus bottom-up control
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= 1967-1980 (predators not poached)
= 1981-1987 (predators poached)
= 1988-2001 (predators not poached)
Top-down versus bottom-up control
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= 1967-1980 (predators not poached)
= 1981-1987 (predators poached)
= 1988-2001 (predators not poached)
Top-down versus bottom-up control
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= 1967-1980 (predators not poached)
= 1981-1987 (predators poached)
= 1988-2001 (predators not poached)
Top-down versus bottom-up control
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= 1967-1980 (predators not poached)
= 1981-1987 (predators poached)
= 1988-2001 (predators not poached)
Top-down versus bottom-up control
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Migration Systems
Characterized by:
1) Resources that varyin time
2) Synchronized births
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Synthesis: top-down control, Allee effects, and apparent competition
From Wittmer et al. 2007
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Synthesis: top-down control, Allee effects, and apparent competition
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Synthesis: top-down control, Allee effects, and apparent competition
_ _
_
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CompetitionInterference competition = negative interaction
between pairs of species, where one species directly inhibits another from consuming a resource
_
_
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CompetitionExploitative competition = negative interaction
between pairs of species, routed through a resource
_ _
_
_
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