apes ch. 6, part 2
TRANSCRIPT
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Understanding Understanding Population GrowthPopulation Growth
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Age Structure
Pre-reproductive ReproductivePost-reproductive
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This group has a large economic impact
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Mostly older people
Declining quickly
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Is a declining population a problem?
YES!
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Problems
Decreased economic growth
Labor shortage – so more immigrant labor
Less taxes – fewer workers
health care costs
pension costs – burden to taxpayers
retirement age
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Other countries with these problems
Germany
Russia
Poland
Italy
Spain
Greece
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AIDS
25 million people dead as of 2008
Kills adults
8 African countries have 16-39% of their adults infected with HIV
Loss of workers
Loss of people to raise kids and care for elderly
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How Does Industrialization How Does Industrialization Affect Population Size?Affect Population Size?
The The
Demographic Demographic
TransitionTransition
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Overall
Shows what happens to countries as they move from developing to developed nations
Economic development and family planning are key factors
Overall: first the death rate goes down, then the birth rate
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FactorsFactorsInfant Mortality Infant Mortality
RateRate number number of babies per of babies per 1000 that 1000 that don’t don’t make it to make it to their 1st yrtheir 1st yrreflect reflect quality of lifequality of life
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Average Average Crude Birth Crude Birth & Crude & Crude Death Death RatesRates
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Stage 1: Pre-Stage 1: Pre-IndustrialIndustrial
High birth rate (high IMR)High birth rate (high IMR)High death rateHigh death rateLow pop growthLow pop growth
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Stage 2: TransitionalStage 2: TransitionalIndustrialization Industrialization food availabilityfood availability Health careHealth careBirth rate stays Birth rate stays
highhighDeath rate Death rate
begins to fallbegins to fallPop grows Pop grows
quicklyquickly
Some countries get stuck here
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Stage 3: Stage 3: IndustrialIndustrial
Birth rate falls to near Birth rate falls to near death ratedeath rate
better jobs and better jobs and education for womeneducation for women
Decline in IMRDecline in IMRPop growth rate Pop growth rate
continues, but is lowcontinues, but is low
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Stage 4: Stage 4: Post-IndustrialPost-Industrial
Birth rate falls Birth rate falls moremore
birth rate = birth rate = death ratedeath rate
ZPGZPG
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Stage 4: Post-IndustrialStage 4: Post-IndustrialThen, birth rate declines Then, birth rate declines
more; less than death more; less than death rate, negative pop growthrate, negative pop growth
UnUnsustainability to sustainability to sustainabilitysustainability
Very fewVery few countries have countries have made it heremade it here
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Calculations
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Population DensityPopulation Density
# of indiv. of a species # of indiv. of a species
unit of areaunit of area
A better way to describe the A better way to describe the size of a populationsize of a population
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Dependent on:Dependent on:
Birth rate (Birth rate (bb ))
Death rate (Death rate (d d ))
Immigration (Immigration (i i ))
Emigration (Emigration (ee ) )
What Causes Populations to What Causes Populations to Change in Size?Change in Size?
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Rate of change ( Rate of change ( r r ) =) =
birth rate (birth rate (bb)-death rate ()-death rate (d d ) x 100) x 100
r = 40 - 20r = 40 - 20
1000 10001000 1000
r r =0.04 - 0.02 x 100 = 2% per year=0.04 - 0.02 x 100 = 2% per year
What Causes Populations to What Causes Populations to Change in Size?Change in Size?
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Rule of 70
A way to estimate the number of years it takes for a certain variable to double.
The rule of 70 states that in order to estimate the number of years for a variable to double, take the number 70 and divide it by the growth rate of the variable.
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Time to take for a population with Time to take for a population with a stable growth rate to double in a stable growth rate to double in sizesize
Doubling Time ( Doubling Time ( ttd d ) =) =
ttd d = 70= 70
rr
Doubling TimeDoubling Time
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Doubling TimeDoubling Time
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Growth Rate of a Pop.Growth Rate of a Pop.
rr = ( = (b - db - d ) + ( ) + (i - ei - e ) )b = .01b = .01 d = .005d = .005
i = .001i = .001 e = .01e = .01
Calculate growth rateCalculate growth rate
Calculate doubling timeCalculate doubling time
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Proportion of a population to Proportion of a population to survive to survive to breeding agebreeding age
Type Type II= = survival survival decreasesdecreases with age with age
Type Type IIII = = survival survival doesn’t changedoesn’t change with with age age
Type Type IIIIII = = survival survival increasesincreases with age with age
SurvivorshipSurvivorship
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Questions to consider
1. What kind of survivorship do humans have? Explain why you think this.
2. How does parental care affect the survivorship curves?
3. What kind of curve for a redwood tree? A sea turtle? A squirrel? Why?