Population growth and limiting factors

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Population growth and limiting factors 4 factors
that can effect population growth Births
Deaths Immigration Emigration Most new
populations have a time of rapidly increasing
growth.
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2 Major types of population growth 1.
Exponential Growth when a population has no
resource limitations Produces a J
curve 2. Logistic Growth when a population
has resource limitations. Produces a S
curve
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Exponential Growth

• Population size expands by ever increasing
  increments during successive intervals
• The larger the population gets, the more
  individuals there are to reproduce

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Exponential Growth Equation

• G rN
• G is population growth per unit time
• r is net reproduction per individual per unit
  time
• N is population size

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Exponential growth
Click to view animation.
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Logistic Growth

• As size of the population increases, rate of
  reproduction decreases
• When the population reaches carrying capacity,
  population growth ceases

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Logistic Growth Graph
initial carrying capacity
new carrying capacity
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Logistic growth
Click to view animation.
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Limiting Factors

• Any essential resource that is in short supply
• All limiting factors acting on a population
  dictate sustainable population size

The size of a population can be limited based on
2 different types of factors Density
Dependent Density Independent
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Density-Dependent Controls

• Logistic growth equation deals with
  density-dependent controls
• Limiting factors become more intense as
  population size increases
• Disease, competition, parasites, toxic
  effects of waste products

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Density-Independent Controls

• Factors unaffected by population density
• Natural disasters or climate changes affect large
  and small populations alike

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Human Population Growth

• Population now exceeds 6 billion
• Rates of increase vary among countries
• Average annual increase is 1.26
• Population continues to increase exponentially

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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

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Side-Stepping Controls

• Expanded into new habitats
• Agriculture increased carrying capacity use of
  fossil fuels aided increase
• Hygiene and medicine lessened effects of
  density-dependent controls

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Future Growth

• Exponential growth cannot continue forever
• Breakthroughs in technology may further increase
  carrying capacity
• Eventually, density-dependent factors will slow
  growth

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Human Population Problems

• Over 6 billion people alive
• About 2 billion live in poverty
• Most resources are consumed by the relatively few
  people in developed countries

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Resource Consumption

• United States has 4.6 of the worlds population
• Americans have a disproportionately large effect
  on the worlds resources
• Per capita, Americans consume more resources and
  create more pollution than citizens of less
  developed nations