Name:
Pre-MacMods
1. When a population of mice experiences no change in the frequencies of alleles, the population is said to
be in genetic equilibrium. What is another name for this principle?
2. What are two of the five conditions that are required to maintain genetic equilibrium?
3. Which of the two graphs below demonstrates genetic equilibrium?
Frequencies of White and Black Mice
Percent of Population
Percent of Population
Frequencies of White and Black Mice
60
40
20
0
1
2
3
4
5
Years
80
60
40
20
0
1
2
3
4
5
Years
Name:
Post-MacMods
1. True or False: In order for the Hardy-Weinberg principle to apply to a population, there must be no
natural selection.
2. When the Hardy-Weinberg principle applies to a population, the population is said to be in genetic
equilibrium. What does genetic equilibrium mean?
3. Sketch a graph showing the frequencies of white moths and black moths if there was no natural
selection.
Percent of Population
Frequencies of White and Black Moths
100
80
60
40
20
0
1
2
3
Years
4
5
Name:
Fishy Frequencies
Introduction: Understanding how natural selection affects the phenotypes of a population can be difficult and
confusing. People often think that animals consciously adapt to their environments- that the peppered moth
changed its color, the giraffe can permanently stretch its neck, the polar bear can turn itself white- all so that
they can better survive in their environments.
In this lab, we will use fish crackers to investigate how natural selection influences phenotypic frequencies in a
population of lionfish.
Background: Facts about the “fish”
1. Invasive lionfish are thought to have no natural predators in their new environment so the only source of
death is natural.
2. However, some people have observed grouper eating lionfish.
3. Lionfish come with two phenotypes for color- bright red and dark brown
a. Bright red: this is recessive (rr)- represented by gold fish crackers
b. Dark brown: this is dominant (RR or Rr)- represented by brown fish crackers
4. New fish are born every year and the birth rate equals the death rate. We will simulate births by
reaching into the pool of “spare fish” and selecting randomly.
5. We will be completing two simulations to investigate how natural selection affects the frequency of
phenotypes over time.
Simulation 1: No grouper predation.
1.
2.
3.
4.
5.
6.
7.
Get a random population of 10 fish from the “ocean”. This will represent the population at Year 1.
Count the number of red and brown fish and record in the data table.
Close your eyes and randomly choose three fish that die.
Close your eyes and randomly choose three fish from the “ocean” to be born into the population.
Record the number of red and brown fish for Year 2.
Repeat steps 3-5 until you have completed 5 years.
Provide your results to the class and fill in the class results table.
Table 1: Partner data
Year
1
2
3
4
5
# of Red
Lionfish
# of Brown
Lionfish
% Red
Lionfish
% Brown
Lionfish
Simulation 2: With grouper predation. For this simulation, grouper will be providing the source of mortality
for the lionfish. Grouper are able to see the bright red lionfish better than the brown ones, so the red ones are
eaten first.
1. Get a random population of 10 fish from the “ocean”. This will represent the population at Year 1.
2. Count the number of red and brown fish and record in the data table.
3. Remove three red lionfish from the population to represent grouper predation (if there are no red
lionfish, then remove brown lionfish).
4. Close your eyes and randomly choose three fish from the “ocean” to be born into the population.
5. Record the number of red and brown fish for Year 2.
6. Repeat steps 3-5 until you have completed 5 years.
7. Provide your results to the class and fill in the class results table.
Table 2: Partner Data
Year
# of Red
Lionfish
# of Brown
Lionfish
% Red
Lionfish
% Brown
Lionfish
1
2
3
4
5
Table 3: Class Data
Year
1
2
3
4
5
# of Red
Lionfish
Simulation 1
# of Brown
Lionfish
% Red
Lionfish
% Brown
Lionfish
# of Red
Lionfish
Simulation 2
# of Brown
Lionfish
% Red
Lionfish
% Brown
Lionfish
Analysis
1. Create one bar graph of both sets of class data (Table 3) for both the red and brown lionfish.
2. In either situation, did the frequencies stay approximately the same over time? If yes, which situation?
3. Which situation demonstrated natural selection? What happened to the frequencies of lionfish over
time?
4. Did the red lionfish ever completely disappear from the population? Why or why not?
When there is no change in phenotypic frequencies within a species, the population is said to be in genetic
equilibrium. This concept is known as the Hardy-Weinberg principle. Five conditions are required to maintain
genetic equilibrium:





The population must be very large
There must be no movement into or out of the population (other than births or deaths)
There must be random mating
There must be no mutations within the gene pool
There must be no natural selection
5. Which simulation demonstrated the Hardy-Weinberg principle? How did you know?
6. Which simulation did NOT demonstrate the Hardy-Weinberg principle? Which of the five requirements
was violated in the simulation?