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Topic – Describing Populations
• Recall from your notes what a
“population” is.
• How is a population
different from a
community?
• What factors affect
a population?
Studying the Population
Why is it important to study populations
of creatures?
Why are humans be concerned about the
decreasing
population of
bees?
Studying the Population
Population size describes the number of
individual organisms in a given
population at a given time.
When the population increases, this is a
sign of a healthy population.
What factors would lead to a population
increasing?
Studying the Population
When the population decreases rapidly,
this can be an indicator that the species
may become extinct.
Golden Toad
Dodo
Determining Population Size
How could you go about determining the
population size of a species in an area?
If we wanted to determine the number of
blades of grass in the football field, how
could we do this?
Assume that the
field is 120 yds
long.
Determining Population Size
The current population of the United
States is approximately 320,132,000
people (3rd highest population in the
world)
The population of China is about
1,367,510,000 (1st in the world)
How do you think these populations are
determined?
Population Density
Population density describes the
number of individuals within a population
per unit area.
The population of Verona is 12,411
residents (as of 2010) and the total area
is 4.378 sq. mi. What is
the population density
of Verona in
residents/sq. mi.?
Population Density
Why would a high population density be
beneficial for a species?
Why would it be detrimental for a
species?
Population Density
Why would a low population density be
beneficial for a species?
Why would it be detrimental for a
species?
Population Distribution
Depending on the species, populations
may organize themselves into different
arrangements.
Population distribution describes how
organisms are arranged within an area.
The three distribution types are:
Random
Uniform
Clumped
Random Distribution
In a random distribution, there is no
particular order to the distribution of the
species.
Uniform Distribution
In a uniform distribution, organisms
organize themselves evenly in an area.
This occurs when individuals hold
territories or compete for space.
Clumped Distribution
In a clumped distribution, organisms
organize themselves according to the
availability of resources.
Age Structure
Populations are made up of varying
proportions of age, as well as males and
females present in the population.
Age structure describes the relative
number of organisms of each age within
a population.
It is often very helpful to graphically show
this information using an…
Age Structure Diagram
An Age structure diagram is a tool used
to show the age structure of populations.
Age Structure Diagram
Populations with a large young
population are capable of creating many
offspring.
Age Structure Diagram
These diagrams are helpful in predicting
future population growth.
China’s A.S. Diagram
France’s A.S. Diagram
Germany’s A.S. Diagram
India’s A.S. Diagram
Japan’s A.S. Diagram
Nigeria’s A.S. Diagram
United State’s A.S. Diagram
Sex Ratios
A population’s sex ratio is the proportion
of males to females.
A population needs a proper number of
males to females in order to ensure their
population does not dwindle.
To ensure proper survival of a species, a
ratio of 50:50 is ideal.