Name: ________________________ Period: ______
EvoDots: What Makes Populations Evolve?
By John Herron, Software for Evolutionary Analysis
Access this on the Macintosh Hard Drive  Applications  Evodots
Part A
1.
2.
3.
4.
Click on EvoDots
Look to make sure that all three check boxes are selected. (Variable, Heritable, Selective)
Under the file menu, select options. Click to select size as the trait in which the dots vary. Click OK.
Now click the New Population button. This creates a new population of 50 dots. Note there is also a
graph on the upper right that shows how many dots of each color and size there are in your
population.
5. You are the predator of the dots. You will eat the dots by chasing them and clicking on them. Do not
begin yet.
A. Develop a hypothesis for how the population of dots will evolve in response to your predation.
If…
Then….
6. Now click on the Run button and “eat” the dots predator until you have eaten 25 dots.
7. Click the Stop button. Observe the histogram showing the distribution of colors among the
survivors.
B. How has the distribution of dots changed? Explain.
8. Now click the Reproduce button. Each survivor dot splits into two offspring dots that are identical
in color and size to each other and to their mother (who no longer exists). This is similar to how
bacteria reproduce, what do we call this type of reproduction? ____________________________________________
9. Click on the Run button again and eat 25 more dots as fast as you can. Click Stop. Again, compare
the survivors and the starting population.
C. Has the distribution of dot colors changed again? How? Does it match your prediction?
Explain.
10. Continue for 5 more rounds of reproduction and predation.
no
D. How many generations does it take for your population of dots to reach a point where there is
longer variation in size? (Does it take more or less than 5?)
11. Under the file menu, select options. Click to select visibility as the trait that varies in the dots.
12. Now click the New Population button.
E. Develop a hypothesis on which color has the best possibility of survival.
If….
Name: ________________________ Period: ______
Then….
13. Run the simulation until you catch 25 dots. Click Stop.
F. Describe what has happened to the population. Does your hypothesis need modification?
Explain.
14. Click the Reproduce button, Run through 25 more dots, then click Stop. Repeat for a total of 6
generations.
G. Describe what has happened to the population. Does this support your hypothesis? Explain.
Part B
Now we will modify our model to explore the requirements for natural selection by populations. The first
requirement we will explore is variation.
H. Note that each population of dots contains a variety of size and color. Do you think the
population of dots would evolve if there were no variation in the starting population? Write a
hypothesis.
If…..
Then….
15. Now test your hypothesis. Under the File menu select Options. Click to select size.
16. Next to the label “Size of dots is:” click on the check box labeled Variable. There should no longer
be a check in the box, this eliminates variation from the population.
17. Now create a new population. All the dots are the same size and color, there is no variation.
18. Go through 5 more rounds of predation and reproduction as you did in Part A.
I. Does the population evolve? Was your prediction correct? Explain your reasoning.
19. Before going on, click on the Variable check box to make the dots variable again.
Part C
Next we will explore inheritance. As noted above, each mother dot produces two offspring identical to each
other and to their mother. In other words, size is heritable: it passes from parents to offspring.
Name: ________________________ Period: ______
J. Do you think the population of dots would evolve if size were not heritable? Write a
hypothesis.
If….
Then…..
20. Test your hypothesis. Next to the label Size of Dots is: click on the check box labeled Heritable.
There should no longer be a check in the box.
21. Create a new (variable) population. Click on the Run button and eat 25 dots.
22. Now click on the reproduce button and watch closely what happens. They may or may not be
identical to the parent or to each other.
23. Go through 5 more rounds of predation and reproduction.
K. Does the population of dots evolve? If so, does it evolve in the same way as when size was
heritable?
Was your prediction correct? Explain.
24. Before going on, click on the Heritable check box to make the dots heritable again.
Part D
Next we explore selection. Because smaller dots were harder to catch the smaller dots were much more
likely to survive than the larger dots. If you were to eat dots at random instead of selectively do you think
the population would evolve?
L. Write your prediction and explain your reasoning.
25. Test your hypothesis. Next to the label Survival is: click on the checkbox labeled Selective. There
should no longer be a check in the box.
26. Create a new population, click on the run button and eat 25 dots. Notice that when you click on the
mouse you kill not the dot you are pointing at, but a dot selected at random. Go through 5 more
rounds of predation and reproduction.
M. Does the population evolve in the same way it does when survival is selective? Explain.
Name: ________________________ Period: ______
Conclusion
Reflect on your experiment with EvoDots and consider the following. Answer in complete sentences.
N. After they were born, did the individual dots ever change their size or color?
O. If the individuals didn’t change, how was it possible for the population to change?
P. What role did predators play in causing the population of dots to evolve? What mechanism of
evolution is this?
Q. Did the predators 1) create a need for the dots to change, or did they 2) simply determine
which dots
survived to reproduce and which did not? Explain which of the 2 statements is correct,
and which one is
incorrect and why.