8C
Real
Population Growth
overall growth rate = birth rate -
death rate
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The average annual growth rate of the world population between 1950 and
2000 was about 1.8%. Find the approximate doubling time and predict the
world population in 2050.
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The average annual growth rate of the US population is about 0.7%.
Find the approximate doubling time and predict the US population in 2050
and 2100. Start from the 2000 population of about 280 million.
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Starting from the 6 billion population in 2000, assume that world population
maintains its current annula growth rate of 1.4%. What will be the world
population when you are 50 years old? 100 years old?
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14 in text.
carrying capacity = maximum sustainable
population.
Logistic Growth
when the population is small relative to the carrying capacity, logistic
growth is exponential.
when the population is approaches the carrying capacity, logistic growth
approaches 0.
growth rate = r * (1 - population/carrying
capacity)
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Consider a population that begins growing exponentially at a base rate
of 3% per year and then follows a logistic growth pattern . If the carrying
capacity is 100 million, find the actual growth rate when the population
is 10 million, 50 million, 90 million.
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Assume the carrying capacity of the world is 8 billion. Use the 1960's
peak annual growth rate of 2.1% and population of 3 billion to predict
the current growth rate with a logistic model. Assume a current world population
of 6 billion. How do the predicted growth rates compare to the actual growth
rate of about 1.4% per year? Is the given carrying capacity too high or
too low? Explain. Do the same for a carrying capacity of 20 billion.
Overshoot and Collapse
is another model of population growth. It predicts that growth will
be exponential until the carrying capacity is exceeded somewhat and then
the population collapses (within a few generations) to a level which is
a tiny fraction of the carrying capacity.
-> can be the cause of extinction.
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