Download Population Biology - Bakersfield College

Population Biology
Professor Andrea Garrison
Biology 11
Illustrations ©2010 Pearson Education,
Inc. , unless otherwise noted
Population Biology
• Population biology = effects of all biotic and
abiotic interactions on a single population
• Population = ?
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Population Biology
• Population biology = effects of all biotic and
abiotic interactions on a single population
• Population = ?
– All members of a species within given geographic
area
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Population Biology
• Population biology = effects of all biotic and
abiotic interactions on a single population
• Population = ?
– All members of a species within given geographic
area
• Niche = ?
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Population Biology
• Population biology = effects of all biotic and
abiotic interactions on a single population
• Population = ?
– All members of a species within given geographic
area
• Niche = ?
• The resources used by a species and the
manner in which those resources are used (role
of a population in nature)
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Population Growth
• Biotic Potential = rate at which a population
will increase if there are no limits on its
growth rate
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Population Growth
• Biotic Potential = rate at which a population
will increase if there are no limits on its
growth rate
– Important aspect of a population
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Population Growth
• Biotic Potential = rate at which a population
will increase if there are no limits on its
growth rate
– Important aspect of a population
– Varies with reproductive strategy
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Reproductive Strategies for Survival
Opportunistic species
(r strategists)
Equilibrium species
(K strategists)
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Reproductive Strategies for Survival
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Population Growth
• Biotic Potential = rate at which a population
will increase if there are no limits on its
growth rate
– Important aspect of a population
– Varies with reproductive strategy
• Opportunistic species will reach biotic potential sooner
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Population Growth
• What inherently increases population size?
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Population Growth
• What inherently increases population size?
– Births
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Population Growth
• What inherently increases population size?
– Births
• What decreases population size?
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Population Growth
• What inherently increases population size?
– Births
• What decreases population size?
– Deaths
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Population Growth
• Population growth = births – deaths
– On world-wide scale
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Population Growth
• Population growth = births – deaths
– On world-wide scale
• Population growth = (births + immigration) –
(deaths + emigration)
– On regional scale
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Population Growth
Patterns over time
• Exponential growth
– Early periods of
population growth
– Plenty of resources
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Population Growth
Patterns over time
• Logistic growth
– Later stages of
population growth
– Resources become
limiting
– growth slows as it
approaches maximum
population the
environment can
sustain
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Population Growth
• Carrying capacity = maximum population the
environment can sustain indefinitely
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Population Growth
• Some populations overshoot the carrying
capacity more rapidly than others
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Population Growth
• When population overshoots, it will decline
and hover around carrying capacity OR . . .
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Population Growth
. . .crash
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Population Growth
• Carrying capacity is
determined by densitydependent limiting
factors
– Resources whose
availability decreases as
pop density increases
• Food, water, space
– Impact shown at A -- rate of
pop increase slows until
pop size is stable
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Density-Dependent Regulation of
Population Growth
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Density-Dependent Regulation of
Population Growth
• Density-dependent factors may also increase
death rates
– Disease transmission
– Accumulation of wastes
– Predation due to greater availability
• All these factors (& others) cause slowing and
leveling off of population growth
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Species Distribution
• Species have a geographic range
– North-south and east-west boundaries within
which the species may be found
• Distribution often varies within the geographic
range
– Species found in some areas and not others
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Species Distribution
• Distribution is determined by densityindependent factors
– Factors unrelated to population density which
limit the presence of the species
– Weather, soil type, other necessary biotic or
abiotic factors
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Species Distribution
• Geographic range
– Often determined by climate
• Many species limited by temperature and/or rainfall
• Genetic variability often plays large role in determining
the extremes of climate a species can survive
– Only a few individuals live at the extreme boundaries of the
range
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Species Distribution
• Distribution within the geographic range
– Abiotic factors
• You don’t find worms living on rocks! Or fish living on land!
– Soil factors (another abiotic factor)
• Nutrients present in soil play large factor in determining location
of plants species within their range
– Deciduous plant require more nutrients than evergreens
– Biotic factors
• Other species may play role in distribution of a species within its
range
– Herbivores cannot live where their plant food source doesn’t grow
– Predators cannot live where their prey are not found
– Plants cannot live where their pollinators are not found
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Disruption of Populations
• Many things can disrupt healthy population
growth
– Environmental disturbances
– Pollution
– Invasive species
– Etc.
– These things effect localized populations within
the geographic range
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