Download Ch 5 secc 3

Ecology CH 5
Section 3
Populations
Population Introduction
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Ecosystems evolve
Species evolve to fit a niche
As species evolve populations change
Population Growth
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1798 Thomas Malthus
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Economist
Stated the human population can outgrow the
environment’s ability to support it
Leads to famine and disease
More offspring are born than can survive
Frogs and other massive egg laying species
 Sheep twins
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Caught the eye of Charles Darwin
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Yes that Charles Darwin!
Population Growth
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Charles Darwin
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“There is no exception to the rule that every
organic being naturally increases at so high a
rate, that, if not destroyed, the earth would
soon be covered by the progeny of a single
pair”
Theorized that on pair of elephants could
produce 19,000,000 in 750 years with
unlimited resources Exponential Growth
•Only possible for a short time in real life
•Resources are always limited
Carrying Capacity
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As populations grow resources become
more limited
Decrease in resources leads to competition
Those who lose die and the death rate of
the population goes up
At the same time the birth rate goes down
When these two are equal the population
levels off
S-shaped
curve
parabola
Carrying Capacity- The number of individuals that can be
supported by an ecosystem
Limiting Factors
Forces that slow the growth of a population
Density-dependent limiting factors
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Depend on the population size
Food, water, space, disease, predation
S-shaped curve
Density-independent limiting factors
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Not linked to population size
Natural disaster, climate, human impact
Boom and bust curve
Boom and Bust Curve
Thrips
S-Shaped Curve
Rabbits
Human Population
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Still exponential
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Can’t continue forever
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Technology, agriculture, and medicine
Resources will become limited
Population will level off
Showing signs of strain
Activity 5.2
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Procedure steps 1&2
Analysis and Conclusion Questions
Homework
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MC 1-10
WC 1-5
CR 3-5
TC 1-4
GA 1-4
http://quickfacts.census.gov