Darwin’s mechanism of evolution
To complete this section of the problem set, you will need the software application EvoDots. You can
downloadEvoDots from Jon Herron’s website at the following URL:
http://faculty.washington.edu/~herronjc/SoftwareFolder/software.html
There is a version of EvoDots for Windows, and a version for MacOS.
EvoDots lets you explore evolution by simulating natural selection in a population of dots. The
EvoDots window contains three white areas, three buttons, and three check boxes. Look to make sure that all three check boxes are checked.
Under the File menu, select Options. Click to select size as the characteristic in which the dots vary, then click Okay. Now click on the New Population button. This creates a new population of 50 dots, scattered at random across the white area on the left. Note also that the white area on the upper right now contains a graph, showing how many dots of each color (and size) there are in your population.
In the EvoDots simulation, you will be a predator on the dots. You will eat the dots by chasing them
and clicking on them with the mouse.
1.Predict how the population of dots will evolve in response to predation. Explain your reasoning.
Now click on the Run button and try to kill a few dots. To play your role correctly, you must act like a
hungry predator. Don’t just wait for the dots to come to you. Go after them! When you click on a dot successfully, it first turns red, then disappears. Eat 25 dots as fast as you can, then click on the Stop button.
When you click the Stop button, the dots stop moving and the white area on the lower right displays a
histogram showing the distribution of colors among the survivors.
2. Compare the survivors to the staring population. Has the distribution of colors changed? How?
Now click on the Reproduce button. Each of the survivor dots splits into two daughter dots. Note that each mother dot splits to become two daughter dots that are identical in color and size to each other and to their mother (who now no longer exists). This is analogous to the asexual reproduction of organisms like bacteria and paramecia.
3. Click on the Run button again, and eat 25 more dots as fast as you can. Again, compare the survivors to the starting population. Has the distribution of colors changed again? How?
4. Was the prediction you made in question 1 correct? Why or why not?
Try playing with the boxes that say Selection is: Variable, Heritable, and Selective.
5. Explain why each of these characteristics is necessary for evolution.