PhET Activity for MS-LS4-4: Natural Selection Lab

DIRECTIONS:
1. You are starting on the 'Lab' tab with a single white rabbit in a brown, temperate environment ('Equator').
2. In the center of the environment, click the 'Add a Mate' button to introduce a second rabbit and enable reproduction.
3. On the left side of the graph, check the boxes for 'Brown Fur', 'Floppy Ears', 'Short Teeth', 'Long Teeth', and 'Data Probe'. This will ensure all traits are tracked on the graph.
4. At the bottom right, press the play button to start the simulation. Watch the rabbits reproduce for a few generations.
5. Press the pause button to stop the simulation.
Spend 2-3 minutes exploring the simulation. Click the play/pause button and observe the rabbits. Look at the graph at the bottom of the screen. Do not add any mutations or environmental factors yet.

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

DIRECTIONS:
1. Click the circular orange reset button at the bottom right to start over.
2. Click 'Add a Mate'.
3. In the 'Add Mutations' panel on the right, click the 'Fur' button to introduce a mutation for brown fur. You will see a 'Mutation Coming...' notification.
4. Press the play button and let the simulation run for 5 generations. You can track the generation number on the x-axis of the graph. Pause the simulation.

QUESTION: Describe what happens to the population of brown-furred rabbits over the first 5 generations. Does the trait disappear, or does it spread? Is there a clear pattern, or does it seem random? Explain your observation.

DIRECTIONS:
1. Continue from the previous slide (paused at generation 5).
2. In the 'Environmental Factors' panel on the right, check the box for 'Wolves' to introduce predators.
3. Press the play button and let the simulation run for at least 5 more generations (to generation 10 or beyond).

QUESTION: Now that wolves are present in this brown environment, which fur color trait provides a clear survival advantage?

DIRECTIONS:
1. Let the simulation continue to run with wolves present until one fur color is clearly dominating the population (e.g., to generation 15).

QUESTION: As generations pass with wolves present, the population of ___ rabbits increases, while the population of ___ rabbits decreases, demonstrating natural selection.

(a)  

DIRECTIONS:
1. Reset the simulation by clicking the orange circular button.
2. Click 'Add a Mate'.
3. In the 'Add Mutations' panel, click the 'Teeth' button to introduce the mutation for long teeth.
4. Press play and let the simulation run for 5-7 generations. Keep the 'Environmental Factors' all unchecked.

QUESTION: Without any environmental pressure related to food, the long teeth trait spreads through the population (a)   .

DIRECTIONS:
1. Continue from the previous slide's state (paused after 5-7 generations with the long teeth mutation present).
2. In the 'Environmental Factors' panel, check the box for 'Tough Food'.
3. Press play and observe for 2-3 generations.

QUESTION: What is the primary effect of introducing 'Tough Food' as a selection pressure?

DIRECTIONS:
1. Let the simulation from the previous slide continue to run until the population is almost entirely composed of long-toothed rabbits.

QUESTION: Put the following events in the correct order to explain why long-toothed rabbits became more common.

DIRECTIONS:
1. Reset the simulation.
2. Click 'Add a Mate'.
3. Let the rabbit population grow for about 5 generations without any mutations or other pressures.
4. In the 'Environmental Factors' panel, check the box for 'Limited Food'.
5. Press play and observe for another 5-7 generations.

QUESTION: When food is limited, ___ among the rabbits increases, which causes the total rabbit population to ___.

(a)  

DIRECTIONS:
1. Reset the simulation.
2. At the top right of the simulation environment, click the snowflake icon to select the 'Arctic' environment.
3. Click 'Add a Mate'. Note that the rabbits are now in a white, snowy environment.
4. In the 'Add Mutations' panel, click the 'Fur' button to introduce the brown fur mutation.
5. Press play and let the simulation run for 5 generations.

QUESTION: In the Arctic environment, the default white fur is better for (a)   , making it an advantageous trait if predators were present.

DIRECTIONS:
1. Continue from the previous slide (paused at generation 5 in the Arctic).
2. In the 'Environmental Factors' panel, check the box for 'Wolves'.
3. Press play and let the simulation run for 5-7 more generations.

QUESTION: Explain why the brown fur mutation, which was advantageous in the 'Equator' environment, is disadvantageous in the 'Arctic' environment. Use the concept of camouflage in your answer.