Population Growth

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Population Growth

• How Populations Grow

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Populations Growth

• Population Growth
• Three factors can affect population size
• number of births (Birth Rate)
• the number of deaths (Death Rate)
• the number of individuals that enter or leave the
  population.
• Simply put, a population will increase or
  decrease in size depending on how many
  individuals are added to it or removed from it

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Immigration Emmigration

• Immigration
• the movement of individuals into an area, is
  another factor that can cause a population to
  grow.
• Emigration
• the movement of individuals out of an area, can
  cause a population to decrease in size.

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The rise and fall of populations..

• Populations Increase
• A higher birthrate in comparison to death rate
• Immigration
• Populations Decrease
• A higher death rate in comparison to birth rate
• Emigration

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What if

• A population is provided with food, space,
  shelter, protection from predators and disease?
• The population will growbecause?

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Exponetial Growth

• Exponential Growth (J-shaped curve)
• If a population has abundant space and food, and
  is protected from predators and disease, then
  organisms in that population will multiply and
  the population size will increase.
• unlimited resources

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Exponential Growth

• Exponential growth occurs when
• the individuals in a population reproduce slowly
• Example bacteria
• A change in a new environment (for a time)
• Example invasive speciese
• Organisms reproduce slowly
• Example Elephants produce offspring 2-4 years

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Checkpoint

• Which of the following is NOT a condition for a
  population to reach exponential growth?
• A.) presence of unlimited resources
• B.) Absence of predation and disease
• C.) movement of individuals out of the
  population

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Logistic Growth

• Logistic growth occurs when a population's growth
  slows or stops following a period of exponential
  growth levels off at Carrying Capacity
•  
• As resources become less available, the growth of
  a population slows or stops. The general,
  S-shaped curve of this growth pattern, called
  logistic growth

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Carrying Capacity

• Carrying Capacity 
• The number or the largest number of individuals
  that a given environment can support.

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• Phases of a Logistic Growth
• I Exponential Growth unlimited resources
• II Growth Slows Down Population still grows,
  BUT rate of the growth is slowing down
• III Growth stops Population is stabilizing _at_
  its carrying capacity

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• Closure Question
• What shape population growth curve would you
  expect to see in a small town made up of Senior
  citizens? Why?
• What shape population growth curve would you
  expect to see in a small town made up of newly
  married couples in their twenties? Why?

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• Using Graphic Organizers
• Draw a concept map that shows how populations
  grow. Include the following terms exponential
  growth, logistic growth, birthrate, death rate,
  immigration, emigration. Add any other terms that
  you think are useful to complete the map

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Population Density

• Population density is the number of individuals
  per unit area.
• The population of saguaro cactus in the desert
  plant community has a low density, whereas other
  plants in that community have a relatively high
  density.

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What factors determine carrying capacity?

• Limiting Factors!
• A factor that controls the growth of a population
• Examples
• Competition
• Predation
• Disease
• Unusual Weather
• Disasters
• Limited nutrients (productivity)

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• Limiting Factors determine the CARRYING CAPACITY
  of an environment for a species!!!!

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Density-Dependent Factors

• Limiting factor is DEPENDENT on the population
  density
• Competition
• Predation
• Herbivory
• Disease
• Stress from overcrowding

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Real Life Examples
Competition
Predator/Prey
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Density-Independent Factors

• Limiting Factors that affect ALL populations in
  similar ways, REGARDLESS of population size and
  density
• Hurricanes
• Droughts
• Floods
• Natural disasters (wildfires)

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Real life examples
Drought
Hurricane Sandy
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Now..

• YOU COME UP WITH REAL LIFE EXAMPLES OF
  DENSITY-DEPENDENT AND DENSITY-INDEPENDENT FACTORS