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5-1 How Populations Grow
Biology
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5-1 How Populations Grow
Characteristics of Populations
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5-1 How Populations Grow
Characteristics of Populations
I. Characteristics of Populations
What characteristics are used to
describe a population?
Three important characteristics of a
population are its:
•  geographic distribution
•  density
•  growth rate
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5-1 How Populations Grow
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Characteristics of Populations
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5-1 How Populations Grow
Population Growth
Geographic distribution, or range, describes the
area inhabited by a population.
Population density is the number of individuals per
unit area.
What factors affect population size?
Growth rate is the increase or decrease of the
number of individuals in a population over time.
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5-1 How Populations Grow
Population Growth
5-1 How Populations Grow
II. Population Growth
Population Growth
Immigration, the movement of individuals into an
area, is another factor that can cause a population to
grow.
Three factors can affect population size:
Populations can increase by immigration as animals
in search of mates or food arrive from outside.
•  the number of births
•  the number of deaths
•  the number of individuals that enter or leave
the population
A population can grow when its birthrate is greater
than its death rate.
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5-1 How Populations Grow
Population Growth
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5-1 How Populations Grow
Exponential Growth
Emigration, the movement of individuals out of an
area, can cause a population to decrease in size.
Emigration can occur when animals leave to find
mates and establish new territories.
What are exponential growth and logistic
growth?
A shortage of food in one area may also lead to
emigration.
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5-1 How Populations Grow
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Exponential Growth
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5-1 How Populations Grow
Exponential Growth
III. Exponential Growth
Under ideal conditions with unlimited resources,
a population will grow exponentially.
Exponential Growth
Exponential growth occurs when the individuals in
a population reproduce at a constant rate.
The population becomes larger and larger until it
approaches an infinitely large size.
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5-1 How Populations Grow
Logistic Growth
5-1 How Populations Grow
IV. Logistic Growth
Logistic Growth
As resources become less available, the
growth of a population slows or stops.
In nature, exponential growth does not continue in
a population for very long.
Logistic growth occurs when a population's
growth slows or stops following a period of
exponential growth.
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Logistic Growth
5-1 How Populations Grow
Logistic Growth
Carrying Capacity
Logistic growth is characterized by an S-shaped
curve.
The largest number of individuals of a population
that a given environment can support is called its
carrying capacity.
When a population reaches the carrying capacity of
its environment, its growth levels off. The average
growth rate is zero.
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Population density is the number of individuals
a.  that are born each year.
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b.  per unit area.
- or -
c.  that immigrate.
d.  that emigrate.
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When the birthrate of a population exceeds its
death rate, the population
An S-shaped curve on a graph of population
growth is characteristic of
a.  decreases.
a.  exponential growth.
b.  increases.
b.  logistic growth.
c.  stays the same.
c.  carrying capacity.
d.  increases then decreases.
d.  delayed growth.
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Exponential growth rate means that each new
generation of a population
Exponential growth in a population slows down
or stops as
a.  adds the same number of new individuals as
the previous generation did.
a.  resources become limited.
b.  rate of immigration increases.
c.  rate of emigration decreases.
b.  increases at the same rate as the previous
generation.
d.  birth rate increases.
c.  is the same size as the generation before.
d.  increases by a varying amount.
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