Natural Selection Lab

This hands-on laboratory exercise is a highly simplified model that attempts to simulate evolution by means of natural selection. Predators will act as agents of selection on their prey, a species whose members vary in color. We will assume that color is an inherited trait. Small squares of paper will represent the prey, which will be spread out of a piece of printed colored fabric that will serve as the habitat. The predators (you) will prey upon the population, with the surviving members reproducing and passing along the genes for color.

Problem:

How does a population change as a result of natural selection?

Materials:

  • 5 different colors of paper cut into 1 cm × 1 cm squares (at least 100 squares of each color)
  • Multicolored fabric or newspaper, approximately 1 meter × 1 meter
  • 1 or 2 partners (friends or family)

Procedure:

  • The prey will be represented by the small 1 cm × 1 cm squares of paper and the habitat is represented by the 1 meter × 1 meter piece of fabric. Hypothesize which color prey you think is most likely to be captured by the predator and which color prey is most likely to survive, and then record your hypothesis. Be sure that your hypothesis includes explanations for your predictions.
  • Have the two partners (prey) stand with their backs to the habitat while you scatter 20 squares of each color randomly on the fabric. Try to achieve a uniform distribution, and be sure to separate any that are clumped together.
  • Have the partner(s) randomly pick up the prey as fast as they can. Have them stop when they have collected a total of 75 prey, leaving the other 25 remaining in the habitat.
  • Count the number of survivors of each color. Each surviving prey has three offspring of the same color, bringing the total population back up to 100. Record the number of each color in the next generation in your data table.
  • Count out the correct number of each colored prey and scatter them on the fabric. Repeat the process two more times, for a total of three generations.

Data and Observations:

Create a data table containing a tally of the number of each color of prey in each generation:

Color 1._________ 2._________ 3._________ 4._________ 5._________
Generation 0 20 20 20 20 20
Generation 1
Generation 2
Generation 3

Record any observations.

Data Analysis:

Create a graph that tracks the changes in the prey population’s colors.

Conclusion:

Be sure to answer the following reflection questions in the conclusion of your lab report:

Reflection questions need to be answered using complete sentences. Some questions may require a longer explanation in paragraph form.

  • How do the original and surviving prey populations compare?
  • How did the colors of each type of prey affect its population size over time?
  • What color(s) seemed to camouflage the best in this habitat? What color(s) seemed to stand out the most?
  • How do you predict the data would change if you continued? Explain your answer.
  • How would these results change if the colors or patterns of the habitat were to change?
  • Identify at least two things that are unrealistic and two things that are realistic about this exercise.
  • What traits could help a predator be more “fit” in this model environment?
  • Describe other adaptations besides color that could affect an individual’s survival.

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