Introduction: You learned in activity B that fit individuals have a better chance of surviving and reproducing than individuals that are less fit. In this activity, you will observe how natural selection affects a population over time.
Question: How does a population change over time?
1. Experiment: Set the Background color to
Red = 100
Green = 255
Blue = 50
Record the Average fitness of generation 1 in the second column of the table. Move your cursor over the insects and find the individual with the greatest fitness. (In the first generation, all the insects will have the same fitness). Record that individual’s phenotype (physical trait) in the table’s third column.
Move the Sim. speed one notch to the right. Run the Gizmo, and complete the table for each listed generation. (The generation number does not have to be exact.)
(chart is on the screenshot)
2. Describe: Examine the data collected for trends.
A. How did the phenotype (physical trait- body color) of the fittest individual change over time? __________________________________________________________
B. How did the population’s fitness change over time? __________________________________________________________________________________________________________________________________________
The process by which populations change over time is known as evolution. This Gizmo only demonstrates how one trait—body color—can evolve.

3. Predict: Based on what you have just seen, how do you think the population will evolve if you made the Background color purple?
_________________________________________________________________________
4. Test: Set Red to 120, Green to 0, and Blue to 160 to make a purple background. Click Play. After 300 more generations have passed, click Pause.
Was your prediction correct? Explain. ___________________________________________ _________________________________________________________________________