Calculus 6.5

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6.5
Logistic Growth Model
Bears
Years
Greg Kelly, Hanford High School, Richland,
Washington
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The exponential growth equation occurs when the
rate of growth is proportional to the amount
present.
If we use P to represent the population, the
differential equation becomes
The constant k is called the relative growth rate.
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However, real-life populations do not increase
forever. There is some limiting factor such as
food, living space or waste disposal.
There is a maximum population, or carrying
capacity, M.
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The equation then becomes
Our book writes it this way
We can solve this differential equation to find
the logistics growth model.
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Logistics Differential Equation
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Logistics Differential Equation
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Logistics Differential Equation
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Example
Logistic Growth Model
Ten grizzly bears were introduced to a national
park 10 years ago. There are 23 bears in the
park at the present time. The park can support a
maximum of 100 bears.
Assuming a logistic growth model, when will the
bear population reach 50? 75? 100?
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Ten grizzly bears were introduced to a national
park 10 years ago. There are 23 bears in the
park at the present time. The park can support a
maximum of 100 bears.
Assuming a logistic growth model, when will the
bear population reach 50? 75? 100?
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At time zero, the population is 10.
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After 10 years, the population is 23.
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We can graph this equation and use trace to
find the solutions.
y50 at 22 years
y75 at 33 years
y100 at 75 years
p