Learning Goals for the Teachable Unit
• Understand that population growth is a
multiplicative process.
• Practice how to construct graphs and interpret
quantitative data.
• Understand that most population growth is
not exponential: factors may limit population
growth.
Learning Goals for the Teachable Tidbit
• Students will be able to construct and
interpret graphs related to population growth.
• Students will understand the difference
between population density and growth rates.
• Students will be able to calculate rates of
population growth and make predictions
about population size.
Teachable Unit: Population
Growth
Preclass
Learning Outcome(s)
1. Know how to define a population.
2. Know that density is one way of measuring
changes in a population.
Activity/assessment
1. Reading/lecture on population
2. Clicker question or online quiz for selfassessment
Density data for three populations (A, B, C) all
taken during the same time intervals.
Time
Pop. A
Pop. B
Pop. C
1
1
10
100
2
2
15
110
3
4
23
121
4
8
35
133
5
16
53
146
1. Graph DENSITY VS. TIME.
2. Calculate which population is growing the fastest.
Brainstorm how you might quantify population
growth rate.
3. Discuss among your groups how you determined
your answer.
4. Combine the graphs on one set of axes. (6 min)
Clicker Question:
Rank the population size at time 10.
A.
B.
C.
D.
E.
A>B>C
C>B>A
B>A>C
None of the above.
There is not enough
information to determine
the answer.
Density data for three populations (A, B, C) all
taken during the same time intervals.
Time
Pop. A
Pop. B
Pop. C
1
1
10
100
2
2
15
110
3
4
23
121
4
8
35
133
5
16
53
146
4. What is the proportional increase in population
size in a given time interval? Is it constant? (2 min)
Clicker Question:
Based on your calculation of the proportional
increase of population size per time interval,
rank the population size at time 10.
A.
B.
C.
D.
E.
A>B>C
C>B>A
B>A>C
None of the above.
There is not enough information to
determine the answer.
Time
1
2
3
4
5
6
7
8
9
10
Pop. A
1
2
4
8
16
32
64
128
256
512
Pop. B
10
15
23
35
53
80
120
180
270
405
Pop. C
100
110
121
133
146
160
176
193
212
233
At time 10: A > B > C
600
500
Number
400
A
300
B
C
200
100
0
0
5
10
Time
15
Clicker Question:
Population growth
A. is additive in all cases (Additive: a
constant number is added for each
time unit within a specific population).
B. is multiplicative in all cases.
(Multiplicative: the number of
individuals added to the population is a
function of the number of individuals
present; therefore, growth changes as
a function of density.)
C. may be additive or multiplicative but
varies by population.
A>B>C
Population A is growing by 100% (or
doubling) in each time interval.
Population B is growing by 50% in
each time interval.
Population C is growing by 10% in
each time interval.
Nt + 1 = Nt + [Nt• proportional change]
A: Nt + 1 = Nt + [Nt• (1.0)]
B: Nt + 1 = Nt + [Nt• (0.5)]
C: Nt + 1 = Nt + [Nt• (0.1)]
2500
multiplicative
Number
2000
additive
1500
Nt + 1 = Nt + [Nt• (1.0)]
Nt + 1 = Nt + (15)
1000
500
0
0
10
5
Time
15
Summative Question
Time
1
2
3
4
5
6
7
8
9
10
density
(number/m2)
10
14
20
28
39
55
77
108
What is the population growth rate?
Predict the population size at time 9 and 10.
Summative Question
Between time intervals 3 and 4, which population is
proportionally growing the fastest?
Between time intervals 8 and 9, which population is
proportionally growing the fastest?
600
500
Number
400
A
300
B
200
C
100
0
0
2
4
6
Time
8
10
12