Examining Population Density
and Dispersion
The following image shows a world map of
human population density. Discuss with your
group, the patterns that you see. Consider
- Where on the map do you see the greatest
population? The least population?
- What “pattern of spacing” – or dispersion - do
you notice?
- Why do you see this type of population
distribution and density?
Population Dynamics
Essential concept: Each population has a
a) density,
b) dispersion, and a
c) survival/reproductive strategy.
Examine this image below:
What density, dispersion, and reproductive
strategies do you notice?
Human Population Growth
What are the factors that affect human
population growth?
Watch the history of world population growth
in less than seven minutes
World Population
Dynamic Population Pyramids
The population pyramid is used by
demographers to study the distribution of
people across age categories. Why do you think
this is called a population pyramid?
Dynamic Population Pyramid
Understanding Exponentials
• Put your pens down for a minute & think about
this:
– An employer offers you two equal jobs for one hour
each day for fourteen days.
– The first pays $10 an hour.
– The second pays only 1 cent per hour, but the rate
doubles each hour.
– Which job will you accept?
Understanding Exponentials
Job 1
90
80
70
60
50
40
30
20
10
0
Job 2
Now, how much would
your employer owe you
if you stayed at this job
for another 2 weeks?
Job 2 lags for a long
time before
exponential growth
kicks in!
1
2
3
4
5
What would happen if this
type of growth took place
within a population?
6
7
8
9
10 11 12 13 14
Population Growth Models
1) Exponential growth model
• Also called geometric growth or J-shaped growth.
• First growth phase is slow and called the lag phase
• Second growth phase is rapid and called the exponential
growth phase
• Bacteria can grow at this rate, so why aren’t we up to our
ears in bacterial cells?
Population Growth Models (cont.)
• Limits to exponential growth
– As population density increases, competition follows
as nutrients and resources are used up
– The limit to population size that a particular
environment can support is called carrying capacity
(k)
– When you’re done writing, put your pens down…
What population do you think this is?