Natural Selection and Population Growth Lab-KellyBoulis.pdf

Natural Selection and Growth of Populations (20 points) Written by Dr. Kimberly Hill-Edwards [Part 2 adapted from HHMI Biointeractive] Part 1: Natural Selection Changes in the characteristics of a population occur through natural selection. Natural Selection occurs when an accidental mutation allows some members of a population to better survive, reproduce, and pass on their traits to their offspring. Using a computer simulation, you will investigate the impact of accidental mutations on a population of rabbits with and without a predator (wolves). 1. Open PHET Natural Selection simulation a. Select ‘Intro’ . You should now see one white rabbit on the screen. 2. Click on ‘Proportions’ in the bottom right corner.

Simulation 1 3. Click “Add a Mate” and let the simulation run for 2 generations. Then click ‘pause’ on the bottom right. a. You can tell how many generations have been born at the top of the screen (the area circled in orange). There is a legend on the left side that shows the distribution of color of the bunnies You should have 18 all white bunnies.

4. Click ‘Play’ and let the simulation run until you have 5 generations. Then click the ‘pause’ button. 5. (0.5 pts): Once the screen reads generation 5, how many bunnies are there, and what is the distribution of color? There are 480 bunnies and they are all white fur. Simulation 2 – Accidental Mutation 6. Click on the orange ‘reset’ button in the bottom right corner (See the orange arrow below).

7. Click on ‘Proportions’ in the bottom right corner. 8. Click “Add a Mate” and let the simulation run for 2 generations. Then click ‘pause’ on the bottom right. 9. Now we will add an accidental mutation. Click on “Dominant Fur” in the upper right- hand corner. 10. Click ‘play’ and wait 3 more generations. Then click the ‘pause’ button.

11. (0.5 pts) Once the screen reads generation 5, how many bunnies are there, and what is the distribution of color? There are 480 bunnies. The distribution of color is 91% white and 9% brown. 12. (1 pt) How did the accidental mutation of brown fur impact the size of the population? (Hint: Refer to questions 1 and 2 to help answer this question.) In generation 5, the total bunny population did not change. However, there was a change in color range. Bunnies are no longer all white. Simulation 3 – Accidental Mutation and a Predator 13. Click on the orange ‘reset’ button in the bottom right corner. 14. Click on ‘Proportions’ in the bottom right corner. 15. Add Dominant fur mutation and then click ‘Add a Mate’ . Wait until you have generation 3. Click ‘pause’ . 16. (0.5 pts) At generation 3, how many bunnies are there, and what is the distribution of color? There are 54 bunnies total. The distribution of color is 83% white and 17% brown. 17. Add a predator. Click the ‘ Wolves ’ button. 18. Click ‘play’ and let the simulation run until generation 4. Then click ‘pause.’ 19. (0.5 pts) At generation 4, how many bunnies are there, and what is the distribution of color? In generation 4, the total bunnies were 25. The distribution of color is 48% white and 52% brown. 20. Click ‘play’ again and let the simulation run until generation 6 . 21. (0.5 pts) At generation 6, how many bunnies are there, and what is the distribution of color? There are 48 bunnies in generation 6. The distribution of color is 19% white and 81% brown

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