DIRECTIONS: Explore the PhET Natural Selection simulation. Begin by observing the default settings in the "Intro" tab and how the bunny population behaves over time. Familiarize yourself with the options for adding mutations, predators, and environmental conditions.

QUESTION: What happens to the bunny population over time when NO mutations or predators are introduced?

DIRECTIONS: Enable the "Add Mutations" option by clicking on the partial bunny below the word "Recessive." (see image to left). Next, click the "Add a Mate" button and watch what happens. Finally, click and hold the fast-forward button (towards the bottom right of the screen) to quickly pass a few generations.

QUESTION: What happened to the bunny population over time with the addition of a mutation?

DIRECTIONS: Reset the sim and once again select the recessive mutation option. Add a mate and then click and hold the fast-forward button to accelerate to the sixth generation. At this point you should get a message stating that "Bunnies have taken over the world!" Close the message and select the "Proportions" option found about halfway up from the fast-forward button.

QUESTION: Approximately what percentage of your world-dominating bunnies are brown?

DIRECTIONS: Reset the sim and repeat the steps from the previous question, but this time select the mutation option below "Dominant." Add a mate, and use the fast-forward button to let the bunnies once again achieve world domination.

QUESTION: Approximately what percentage of the bunnies were brown this time?

DIRECTIONS: Reset the sim and once again click the fur button below the word "Recessive," add a mate, fast forward to the third generation, and press the pause button. Next, check the box next to wolves to add predators and resume the sim by pressing play. Once again, fast forward and watch what happens.

QUESTION: How long did it take for the bunnies to reach world domination this time compared to last time without the wolves?

DIRECTIONS: Run the sim like you did on the previous question, but select the fur trait below the word "Dominant." Once again, add predators on generation 3 and fast forward until the bunnies achieve world domination.

QUESTION: This time it only took​ (a)   generations for the bunnies to dominate. This is because mutations that are​ (b)   become more common than mutations that are​ (c)   . In this case, ​ (d)   fur was dominant to​ (e)   fur, allowing the bunnies with the mutation to better camouflage in their environment, survive, reproduce, and pass on the more beneficial trait.

READ: Habitats can change over time or experience brief disruptions. Either way, having more genetic variety (traits) in a population usually means there are better chances of survival. An individual's ability to survive and reproduce is defined as their fitness. A population with more variety is considered to have greater fitness potential.

WRITE: Imagine that the warm, brown environment suddenly becomes cold and snowy. Explain how having greater genetic variety in this scenario would be beneficial and what the bunny population would look like before and after the change, including the role predators such as wolves play. Finally, test your prediction by adding the mutation, running the sim for a few generations, adding wolves, and then clicking the snowflake icon to change the environment.