Name: ___________________________________________________
Period: ___
Natural Selection Simulation
Website:
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URL: https://phet.colorado.edu/en/simulation/legacy/natural-selection
Search: Google, “PhET Natural Selection” and it should be the first option
Instructions:
1) When you first open the simulation there will be a single white rabbit on a brown background.
a. If you don’t add any other rabbits, does the starting rabbit reproduce?
b. What kind of reproduction must rabbits use based on your answer to (a)?
c. If you let the simulation keep running what eventually happens to the rabbit?
2) Now add one other rabbit using the, “Add a friend” button. Let the simulation run.
a. What happens to the population every “generation” (every time it adds new rabbits)?
b. If you let the simulation keep running what eventually happens?
c. Obviously this doesn’t normally happen in nature. What stops it from happening? (There are several
possible answers)
Population
d. Do a sketch of what the graph when the simulation has come to an end. You will have to zoom out on the
graph to see how high it goes. Number the Y-axis (the simulation does not give numbers for the X-axis)
Time
3) Start the simulation over and add a friend. Click the, “Long Teeth” button under “Add Mutation.” This will make
it so that next generation a single individual will show up with long teeth.
a. Let the simulation run to the end again. On the graph did the long teeth population ever get higher than the
short teeth population?
b. Based on this, do you think having long teeth is a useful adaptation in this environment?
c. Restart the simulation with the same steps above. Wait until the rabbit population reaches about 20 and
then turn on “Food” under the “Selection Factor” area on the right. What starts happening to the
population?
Population
d. Sketch the graph of the short and long teeth rabbits (don’t graph the Total population line). Use a solid line
for short teeth and a dotted line for long teeth.
Time
e. On the graph did the long teeth population ever get higher than the short teeth population?
f.
Based on this, do you think having long teeth is a useful adaptation in an environment with this type of
food?
4) Press “Reset All” and add a friend. Add in a mutation for brown fur and then pause the simulation.
a. Do you think the white or brown furred rabbits will do better in the Equator (brown) environment?
b. Let the simulation run to the end. Which type of rabbit did you have more of? Was your hypothesis in (a)
correct?
c. Restart the simulation with the same settings as above. This time add in “Wolves” under the “Selection
Factor” after the population has reached about 20. Let the simulation run to the end. Which type of rabbit
did you have more of?
d. Repeat the steps in (c), but after a few generations switch the “Environment” to “Arctic.” What happens to
the number of brown rabbits versus the number of white rabbits?
e. In conclusion, what needs to be present in order for color to matter?
5) Design your own simulation and detail your procedure below. (Think of how the instructions are written above
and use those to guide your explanation).
a. Simulation design:
b. What do you predict will happen with your changes?
c. Was your hypothesis correct? Explain.
Analysis:
6) What happens to populations if there are no limits?
7) Did the same types of rabbits do well in all environments?
8) If there were never any mutations would the rabbit population survive?