Natural Selection Simulation

Observe natural selection at work!

Adjust the predation pressure from None, Low, then High. Watch what happens.

Adjust to see the different types of trees from normal to sooty. What happens to the number of moths for each situation?

Predetory Pressure
Normal Trees
Sooty Trees
White Moths
Black Moths
Read Explanation

In this interactive, you are presented with a wooded scene with moths covering the trees. Some of the moths blend into the bark, while others stand out. You are asked to select between no predatory pressure, low predatory pressure, and high predatory pressure. When you select no predatory pressure, nothing happens. With light predatory pressure, birds come in at a slow rate and begin to pick off the moths. The moths that stand out are more vulnerable while the moths that blend into the tree bark are less visible and are picked off at a lower rate. When high predatory pressure is selected, birds come in at a higher rate, and while the moths that stand out are still more vulnerable and are picked off at a higher rate, even more of the moths that blend in are eaten. You are also asked to select between normal trees and sooty trees. When you select sooty trees, the color of the tree bark changes and the moths that once blended in now stand out, and the moths that stood out before, now blend in. The options of predatory pressure invoke the same response but for the opposite color of moths.