Science 9 - Population Growth

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POPULATIONS
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What is Population Size?

• Total number of 1 species in an ecosystem.
• You can select the ecosystem
• Example
• Population of people in Dante
• Population of people in Toronto

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What is a Population?

• An ecosystem is made of several populations
• Imagine High Park

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Populations
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Population Growth

• The rate at which a population size changes.
• Populations can increases or decrease, but most
  populations remain stable

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World Population Growth
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Factors Controlling Population Growth

• Natality
• Number of births
• Immigration
• Individuals entering an ecosystem
• Mortality
• Number of deaths from diseases, being eaten, etc.
• Emigration
• Individuals leaving an ecosystem

Population Increases
Population Decreases
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Factors Controlling Population Growth
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Factors Controlling Population Growth

• To measure if how a population grows, we
  calculate population growth using the following
  formula

POPULATIONGROWTH
(NATALITY IMMIGRATION) (MORTALITY
EMIGRATION)
Population Increases
Population Decreases
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Closed Population

• These are populations in which individuals can
  NOT enter (immigration) or leave (emigration)
• Populations change because of births and deaths.
• Example Zoo or Fishtank

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Open Populations

• These are populations affected by all four
  factors (birth, death, immigration, and
  emmigration)
• Example natural ecosystem, park

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Population Histograms

• These provide information about the number of
  people at different ages
• Allow us to decide if a population is growing,
  stable, or on the decline.

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Population Histograms

• Growing Populations
• More individuals at younger ages
• Shaped like a pyramid, with a wide base

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Population Histograms

• Stable Populations
• About the same number of individuals at every age
• Straight shaped

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Population Histograms

• Declining Populations
• Wider portions found toward the middle of the
  population
• Smaller base

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J-Curve

• A population with unlimited resources grows in
  the form of a J-Curve
• In the natural world, J-Curve does not occur
  because resources are LIMITED

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Human Population Growth