PhET Activity for MS-LS4-6: Natural Selection

DIRECTIONS:
1. Click the 'Intro' button on the main selection screen to enter the first part of the simulation.
2. To start the population, click the 'Add a Mate' button that appears in the environment.
3. Press the 'Play' button located at the bottom center of the screen to start the passage of time.
4. Observe the rabbits as they reproduce and the population grows.
Spend 2-3 minutes exploring the simulation. Observe the rabbits and the graph at the bottom of the screen. Try pausing and playing the simulation. Do not change any other settings yet.

QUESTION: Are you acquainted with the tools in this simulation?

DIRECTIONS:
1. Click the orange 'Reset All' button in the bottom right corner.
2. Click the 'Intro' button to return to the main intro screen.
3. Click the 'Add a Mate' button.
4. Press the 'Play' button and let the simulation run for about 5-6 generations. Observe the 'Total' population line on the graph.

QUESTION: What generally happens to the rabbit population over time when there are no mutations or environmental pressures like wolves or food shortages?

DIRECTIONS:
1. Click the orange 'Reset All' button.
2. Click the 'Intro' button.
3. Click 'Add a Mate' and press 'Play'. Let the population grow for one or two generations, then press 'Pause'.
4. In the 'Add Mutation' panel on the right, click the 'Fur' button. A 'Mutation Coming...' notification will appear.
5. Press the 'Play' button again and watch the environment closely until a rabbit with brown fur is born.

QUESTION: A ___ is a random change in an organism's genetic material that can introduce new ___ into a population, which is the raw material for natural selection.

(a)  

DIRECTIONS:
1. Reset the simulation by clicking the orange 'Reset All' button.
2. Click the 'Intro' button.
3. Click 'Add a Mate'.
4. Before starting, add the brown 'Fur' mutation from the panel on the right.
5. Also before starting, add a selection pressure by checking the 'Wolves' box in the 'Environmental Factors' panel.
6. Press the 'Play' button and let the simulation run for at least 10 generations.

QUESTION: In the temperate environment with wolves, the proportion of rabbits with brown fur will (a)   over time.

DIRECTIONS:
1. Pause the simulation and look at the graph from your experiment on the previous slide.

QUESTION: Explain why the brown fur trait became more common when wolves were introduced into the temperate environment. Use the word 'camouflage' in your answer.

DIRECTIONS:
1. Reset the simulation.
2. Click the 'Intro' button.
3. At the top center, click the 'Environment Toggle' (sun icon) to switch to the arctic (snowflake) environment.
4. Click 'Add a Mate'.
5. Add the brown 'Fur' mutation.
6. Add 'Wolves' as a selection pressure.
7. Press 'Play' and observe for at least 10 generations.

QUESTION: What is the most likely outcome for the rabbit populations in the arctic environment with wolves?

DIRECTIONS:
1. From your previous experiment in the arctic, pause the simulation.
2. To the right of the graph, click the 'Proportions' radio button to change the data display.
3. Use the slider that appears below the bar charts to move through the generations and see how the percentages change.

QUESTION: The 'Proportions' view is useful because it shows the ___ of a trait within the population, which is a clearer indicator of ___ than the raw population number.

(a)  

DIRECTIONS:
1. Reset the simulation.
2. At the bottom of the screen, click the 'Lab' tab to enter the advanced simulation.
3. Click 'Add a Mate'.
4. In the 'Add Mutation' panel, click the 'Fur' button.
5. A pop-up will appear. Select 'Dominant' to make the brown fur allele dominant.
6. Press 'Play' and observe how the brown fur trait appears and spreads in the population (without any selection pressure yet).

QUESTION: Arrange the steps to set up an experiment to test a dominant brown fur mutation in the Lab.

DIRECTIONS:
1. Reset the simulation.
2. Click the 'Lab' tab.
3. Click 'Add a Mate'.
4. In the 'Add Mutation' panel, click 'Fur'.
5. This time, select 'Recessive' in the pop-up menu.
6. Press 'Play' and observe how the recessive brown fur trait appears and spreads in the population.

QUESTION: Even if it is beneficial, a new recessive allele will initially spread through the population (a)   than a beneficial dominant allele.

DIRECTIONS:
1. Reset the simulation.
2. Go to the 'Lab' tab.
3. Click 'Add a Mate'.
4. In the 'Add Mutation' panel, click 'Teeth' to introduce the long teeth mutation (you can choose dominant or recessive).
5. In the 'Environmental Factors' panel, check the 'Tough Food' box.
6. Press 'Play' and observe how the populations change over several generations.

QUESTION: When 'Tough Food' is the selection pressure, what happens to rabbits with the long teeth trait?