Tree squirrels can have different fur colors. Squirrels live in forests where foxes also live. Foxes hunt squirrels for food. Squirrels that have fur the same color as the trees are harder for the foxes to see and catch.

After a couple of generations, scientists found black squirrels living in the trees. How did the color of the trees in the squirrels’ environment change? Explain what happened to the squirrels over many generations.