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TRANSCRIPT
2004-20051
Half Hollow Hills High School Ms. FogliaAP Biology
2004-2005AP Biology
Population Ecology
Chapter 52
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Essential Questions How do we measure a population? How do populations change over time? What factors affect population density,
distribution & age structure? What are the limits to growth of a
population? How many humans can
the Earth support?
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Populations Population
group of individuals of same species insame general area
rely on sameresources
interact interbreed
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First measuredensity & dispersion
What environmentalfactors affect apopulation?
Population Ecology Population Ecology
study of populations in relation toenvironment
environmental influences on populationdensity & distribution, age structure,and variations in population size
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Population density How do we measure how many
individuals in a population? number of individuals in an area mark & recapture methodsHow does this work? Difficult to count a moving target
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Patterns of Dispersal Spacing patterns within a population
Provides insight into theenvironmental associations& social interactions ofindividuals in population
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Clumped Pattern (most common)
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Uniform
Clumped patternsmay result from directinteractions betweenindividuals in thepopulation
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Changes topopulation size Adding &
removingindividuals from apopulation birth death immigration emigration
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What doesthis tell youabout thepopulation?
Demography Factors that affect growth & decline of
populations vital statistics & how they change over
time
Life table
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Survivorship curves Graphic representation of life table
Belding ground squirrel
The relatively straight lines of the plots indicate relatively constant rates ofdeath; however, males have a lower survival rate overall than females.
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Survivorship curves What does this tell about survival & strategy
of a species
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Reproductive Table Fertility schedule
age-specific summary of reproductiverates for females
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maximum rate =intrinsic rate of increase
Population growthchange in population = births – deaths
Exponential model (ideal conditions)dN = rmaxNdt
N = # of individualsr = rate of growtht = time period
growth increasing at constant rate
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Exponential growth rate Characteristic of populations
introduced to a new environment orrebounding from a catastrophe
African elephantprotected from hunting
Whooping cranecoming back from near extinction
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Carrying capacity Can populations continue
to grow exponentially? Of course NOT! What sets limit?
Carrying Capacity (K) maximum population
size that environmentcan support with nodegradation of habitat
not fixed; varies withchanges in resources
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Logistic model of growth
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Logistic model of growth
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Life history traits K-selection = density dependent r-selection = maximize reproductive success
K-selection
r-selection
mortality constant
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Trade offsNumber & size of
offspringvs.
survival of offspringor parent
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Parental survivalThe cost of largerbroods to bothmale & femaleparents
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Regulation of population size Limiting factors
density independent environmental disturbances
density dependent food supply competition predators
Population cycles population
fluctuations Dungeness crabs
ocean currents & cannibalism
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Limits to growth Negative feedback prevents unlimited
growthDensity dependent death raterises as birth rate rises
Densityindependentdeath rate orbirth rate
What does it mean to be densitydependent or density independent?
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Population dynamics Complex interaction of biotic & abiotic
influencesDecline of Northern Pintail
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Isle Royale studiesMoose population on small island in Lake Superior
Why so unstable?
wolvesstarvation
winter loss
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Predator – prey interactions Population cycles
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Human population
What factors have contributed tothis exponential growth pattern?
1650→500 million
2005→6 billion
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Human population: rate of growth
Percent increase inglobal humanpopulation (to 2003).Dashed portion ofcurve indicatesprojected data. Sharpdip in 1960s is duemainly to a famine inChina in which ~ 60million people died.
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Demographic comparisonsWhat do the data implyabout population growthin these countries?
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Age structure Relative number of individuals of each age
What do the data imply about population growth inthese countries?
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Impact: Ecological FootprintIs the human populationnear carrying capacity?
Based on land & water areaappropriated to produce allresources it consumes & toabsorb all wastes it generates
deficit surplus
K = 10–15 billion? 2005 = ~6 billion