4 Environment and Fitness

Before working on this section, click the Reset link at the upper-right corner of your Ducks & Gators window.

We have seen that in our virtual ducks, genotype determines color and color influences survival. But something else influences survival too: the number of gators in the pond.

Pick a color for your A1A1 ducks. Any color is fine for this exercise—except white or black. (A little experimentation should reveal why we want you to avoid these colors for now.)

Set the number of gators to zero, get a new set of ducks, and measure the survival rate of your A1A1 ducks. Repeat this experiment for 3, 6, 9, and 12 gators:

  1. Number of survivors with 0 gators:

    Number of survivors with 3 gators:

    Number of survivors with 6 gators:

    Number of survivors with 9 gators:

    Number of survivors with 12 gators:

  2. How does the number of gators influence survival in your ducks? Why?

This graph shows my results with the default color for A1A1 ducks and every possible number of gators from 0 to 12:

Environmental variation for survival in the default model.
Environmental variation for survival in the default model.

Note that the points don’t all fall right on the best-fit line. Why?

(Also note that a straight line may not be the best description of the pattern in the data—but that is beyond the scope of this exercise.)

These results demonstrate environmental variation for survival in our virtual duck population.

  1. Note that if you set the number of gators (to, for example, 4), then switch to a different number and back, the gators will be in different locations every time. Can the location of the four gators influence the survival of the ducks? Why or why not?