Populations 1

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Populations 1

• Mr. Shrout

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3 Important Characteristics to a Population

• Geographic Distribution- area inhabited by a
  population
• Cm3- km2
• Population Density- the number of individuals per
  unit of area
• Smaller organisms- higher densities
• Larger organisms- lower densities
• Ex. 25.1 deer/mi2 in PA
• Growth Rate- change in the number of individuals
  over time
• Positive growing
• Negative shrinking
• Zero constant

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Distribution Patterns
Even Dispersal Random Dispersal Clumped
Dispersal
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Population Size

• How can you change the size of a population?
• Add
• Births new individuals are added to the
  population through reproduction
• Immigration movement of individuals into an
  area
• Animals arrive in new habitat etc..
• Decrease
• Deaths old individual dies
• Emigration movement of individuals out of a
  population
• Young leave an area as they mature

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What determines population growth rate?

• Population growth rate change in population
  size per unit of time
• Births immigration ? increase population
• Deaths emigration ? decrease population
• Population growth rate ((birthimmigration
  rate) (deathemigration rate))/ time

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Growth Patterns

• Exponential Growth- individuals reproduce at a
  constant rate. This occurs under ideal
  conditions with unlimited resources
• No predation, unlimited food, unlimited space
• Ex. Organisms that reproduce asexually- bacteria
• This growth pattern creates a J-shaped curve

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Exponential Growth

• Remember- unlimited resources
• Reproducing at maximum rate

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Growth Patterns

• Exponential growth never lasts for very long- the
  environment cannot support it.
• Logistic Growth- populations growth slows or
  stops as resources become less abundant
• How Births decrease, deaths increase,
  immigrations decrease, emigrations increase
• This is the pattern most often observed

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Logistic Growth

• Creates an S-shaped curve
• Carrying Capacity (K) The point around which the
  growth line becomes flat (growth rate 0)
  represents the larges number of individuals that
  environment can support

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K is a hard thing to reach
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As Environment Changes, so does carrying capacity