1/11/2011 1 Population Biology Population Biology Lecture Lecture Prepared by Prepared by Diana Wheat Diana Wheat LBCC LBCC Population Population All of the members of a particular All of the members of a particular species within an ecosystem, found species within an ecosystem, found in the in the same time same time and and place place and and actually or potentially can actually or potentially can interbreed interbreed . Factors that Change a Factors that Change a Population Size Population Size Increase Increase Births Births Immigration Immigration Decrease Decrease Deaths Deaths Emigration Emigration Change in Population: Change in Population: (births (births – deaths) + (immigrants deaths) + (immigrants –emigrants) emigrants) Growth Rate (r) Growth Rate (r) Growth rate (r) is a measure of change in Growth rate (r) is a measure of change in population size per individual population size per individual per unit of time. per unit of time. r = r = (birth rate) b (birth rate) b – (death rate) d (death rate) d Example Example If we wish to calculate the annual growth If we wish to calculate the annual growth rate of a human population for a given rate of a human population for a given community that initially begin at 10,000, community that initially begin at 10,000, where 1500 births occurred in a year and where 1500 births occurred in a year and 500 deaths occurred in a year. The 500 deaths occurred in a year. The calculation would be: calculation would be: 1500/10,000 1500/10,000 – 500/10,000 = 0.10 or 10% 500/10,000 = 0.10 or 10% Biotic Potential Biotic Potential The maximum rate at which the The maximum rate at which the population could increase, assuming ideal population could increase, assuming ideal conditions. conditions.
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1/11/2011
1
Population BiologyPopulation BiologyLectureLecture
Prepared by Prepared by
Diana WheatDiana Wheat
LBCCLBCC
PopulationPopulation
All of the members of a particular All of the members of a particular species within an ecosystem, found species within an ecosystem, found in the in the same timesame time and and place place and and actually or potentially can actually or potentially can interbreedinterbreed..
Factors that Change aFactors that Change aPopulation SizePopulation Size
IncreaseIncrease
BirthsBirths
ImmigrationImmigration
DecreaseDecrease
DeathsDeaths
EmigrationEmigration
Change in Population:Change in Population:
(births (births –– deaths) + (immigrants deaths) + (immigrants ––emigrants)emigrants)
Growth Rate (r)Growth Rate (r)
Growth rate (r) is a measure of change inGrowth rate (r) is a measure of change in
population size per individual population size per individual
per unit of time.per unit of time.
r =r = (birth rate) b (birth rate) b –– (death rate) d(death rate) d
ExampleExample
If we wish to calculate the annual growth If we wish to calculate the annual growth rate of a human population for a given rate of a human population for a given community that initially begin at 10,000, community that initially begin at 10,000, where 1500 births occurred in a year and where 1500 births occurred in a year and 500 deaths occurred in a year. The 500 deaths occurred in a year. The calculation would be:calculation would be:
1500/10,000 1500/10,000 –– 500/10,000 = 0.10 or 10%500/10,000 = 0.10 or 10%
Biotic PotentialBiotic Potential
The maximum rate at which the The maximum rate at which the population could increase, assuming ideal population could increase, assuming ideal conditions.conditions.
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Exponential Growth in Mice
Logistic Growth EquationLogistic Growth Equation
Population growth per unit time = Population growth per unit time =
Maximum per capita growth rate Maximum per capita growth rate x Number of individuals x x Number of individuals x
Proportion of resources not yet Proportion of resources not yet usedused
Logistic GrowthLogistic Growth
Environmental ResistanceEnvironmental Resistance
Limits set by the natural environment that Limits set by the natural environment that oppose biotic potential.oppose biotic potential.
FactorsFactors
Density dependentDensity dependent: Control measures that: Control measures that
are a reflection of population size.are a reflection of population size.
Density independentDensity independent: Control measures that are: Control measures that are
NOT dependent upon the size of the populationNOT dependent upon the size of the population
e.g. Weather conditionse.g. Weather conditions
Selection PressuresSelection Pressures
1) Availability of resources1) Availability of resources
FoodFood
WaterWater
SpaceSpace
2) Interactions with other species2) Interactions with other species
PredationPredation
ParisitismParisitism
CompetitionCompetition
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Carrying CapacityCarrying Capacity
The largest number of organisms of aThe largest number of organisms of a
particular species that an area can supportparticular species that an area can support
for an indefinite period of time.for an indefinite period of time.
Can a population increase indefinitely?Can a population increase indefinitely?
Exceeding carrying capacity can damage an Exceeding carrying capacity can damage an ecosystem, reducing its ability to support the ecosystem, reducing its ability to support the population. If the carrying capacity is exceeded population. If the carrying capacity is exceeded it may crash and could ultimately go extinct.it may crash and could ultimately go extinct.
A population can become A population can become stable.stable.
WhenWhen
�� birthsbirths (+ immigration) = deaths (+ emigration(+ immigration) = deaths (+ emigration))�� The average rate of reproduction replaces each individual.The average rate of reproduction replaces each individual.
Distribution of PopulationsDistribution of Populations
�� ClumpedClumped
�� RandomRandom
�� UniformUniform
AnimationAnimation
Life History Life History PatternsPatterns
TypesTypesI I –– High youth survivalHigh youth survivalII II –– Equal probabilityEqual probabilityIII III –– Low youth survivalLow youth survival
AnimationAnimation
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DemographicsDemographics
Statistics that describe:Statistics that describe:
-- Population sizePopulation size
-- DensityDensity
-- DistributionDistribution
-- Age structureAge structure
Shaped by ecological factors.Shaped by ecological factors.
..
Human PopulationsHuman Populations
Type I survivorship.Type I survivorship.
Populations tend to be clumped.Populations tend to be clumped.
Fig. 45-14, p. 809
Type I survivorship.Type I survivorship.Populations tend to be clumped.Populations tend to be clumped.Has not yet Peaked Has not yet Peaked –– carrying capacity not certain.carrying capacity not certain.
Human Population
Fig. 45-16a, p. 811
Fig. 45-16b, p. 811
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