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Human Populations and Demographics

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Human Populations and Demographics Age Structure Diagrams Shows age distribution of a population Pre-reproductive, reproductive and post-reproductive groups ... – PowerPoint PPT presentation

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Title: Human Populations and Demographics


1
Human Populations and Demographics
2
Age Structure Diagrams
  • Shows age distribution of a population
  • Pre-reproductive, reproductive and
    post-reproductive groups

SLOW GROWTH
ZERO GROWTH
NEGATIVE GROWTH
RAPID GROWTH
3
Demographic Transition Model
  • Based on historical data from western Europe
  • Postulates that as countries become
    industrialized, first death rates drop, then
    birth rates drop

4
Demographic Transition Model
Stage 1 Preindustrial
Stage 2 Transitional
Stage 3 Industrial
Stage 4 Postindustrial
relative population size
births
deaths
low
increasing
very high
decreasing
low
zero
negative
5
Population Momentum
  • Lowering fertility rates cannot immediately slow
    population growth rate
  • Why? There are already many future parents alive
  • If every couple had just two children, population
    would still keep growing for another 60 years

6
Population Size
  • N1 N0 (B D I E)
  • where
  • N0 initial population
  • N1 population at a later time
  • B birth rate
  • D death rate
  • I immigration
  • E emigration

7
Population Doubling Time
  • Rule of 70
  • 70 divided by net growth rate
  • or
  • Dt 70 / R0

8
So Whats Net Growth Rate?
  • Net Growth Rate
  • Pop size at a later time / Pop size at initial
    time
  • or
  • R0 N1 / N0

9
Notes on Birth and Death Rates
  • B births per 1000
  • D deaths per 1000
  • Remember to multiply by 1/10 if you want
  • Intrinsic rate of increase
  • r B D
  • This will give of new people per 1000 per year

10
Rate of change of population size
  • dN change in population (N1-N0)
  • dt time period
  • rN change of population in of people
  • dN/dt rN

11
Example 1
  • In 1950, the population of a small town was
    20,000. The birth rate was measured at 25 / 1000
    per year, while death rate was 7 / 1000 per year.
    The immigration rate was 600 while the emigration
    rate was 200.
  • What was the population size in 1951?
  • What was the intrinsic rate of increase?
  • What was the rate of change of the population?
  • What is the Net Growth rate?
  • What would be its Doubling time if the pattern
    continued?

12
A population size
  • N1 N0 (B D I E)
  • N1 20,000 25(20) -7 (20) 600 200
  • N1 20,760

13
A Intrinsic Rate of Increase
  • r B D
  • r 25 7
  • r 18 new people per year per 1000 population

14
A Rate of Change
  • dN/dt rN
  • (20,760 20,000) / 1 year 760 people per year

15
A Net Growth Rate
  • R0 N1 / N0
  • R0 20,760 / 20,000 1.038

16
A Doubling time
  • Dt 70 / R0
  • Dt 70 / 1.038 67 years

17
Example 2
  • If a population doubles in about 70 years, it is
    showing what net growth rate?

18
A
  • Dt 70 / R0
  • 70 70 / R0
  • R0 70 / 70 1 net growth rate
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