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Population Dynamics
Ecology
Chapter 4.1
Principles of Population Growth
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A population is a group of organisms of the
same species that live in a specific area.
Healthy populations will grow and die at a
relatively steady rate unless resources run out
or disease.
Population Growth
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Populations grow on a J-curve or exponential
curve.
Rates start slow and then rapidly increase.
Limits on Growth
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Can populations grow forever? NO.
Populations reach limiting factors like food,
disease, predators, lack of space.
This is depicted in a graph of population #’s as
a S-curve.
Carrying Capacity
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The number of organisms of one species that an
environment can support indefinitely is its
carrying capacity.
What is human’s carrying capacity?
Reproduction Patterns
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In nature, animals and plant populations
change in size- even at different times of the
year.
Reproductive patterns are known as lifehistory patterns.
There are two patterns- slow (humans) and
rapid (mosquitoes).
Slow and Fast life-history
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Rapid- usually small organisms in unpredictable
environments that rapidly mature and have a
short life.
Slow- live in stable environments and have a
long life span and mature slowly. They usually
live around the carrying capacity.
Density factors
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Density-dependent factors- factors that have an
increasing effect on a large, growing
population. Diseases, predators, food,
parasites.
Density-independent factors- factors that affect
populations regardless of size or density.
Abiotic factors like fires, floods, drought…
Populations are either randomly spread,
clumped, or uniform.
Dependent or Independent?
Dependent or Independent?
Uniform/Random/Clumped
Predation and Population Size
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Populations of predators and their prey
experience cycles or changes in their numbers
over periods of time.
Crowding and Stress
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When populations are crowded, organisms
exhibit symptoms of stress.
Populations exhibit aggression, decrease in
parental care and decreased resistance to
disease.