NATURAL SELECTION OF POPULATIONS
Thanks to Steve Dyche of the ASU Math Science Education Center for this Lab
Purpose
To illustrate the importance of natural selection as the chief mechanism of population
change and to show the importance of color to the survival of certain populations.
Materials
500 paper chips (50 each of 10 , different colors)
Plastic vials to house the paper chips (1 per color)
Pieces of fabric 3' X 6' each of various designs and differing in basic colors
Graph paper
Several small bowls
Procedure
In this lab activity you are to work in groups of 5 (if possible). Your team should remove
10 chips from each of the ten vials and create a population of 100 animals of 10 different
colors. If there are 5 persons on your team each one might be responsible for counting out
and taking care of two of the colors (also be responsible for putting the chips back at the
end of the exercise). Place all the chips in a single container and mix well by shaking.
Your teacher will now spread the chips out over the piece of colored fabric. Team
members should stand with their backs toward the habitat to prevent locating particular
chips in advance. At a signal, each predator (person) picks up one chip at a time. After
each chip is grasped the predator should place it in a nearby container. This forces the
person to simulate common predatory behavior in which attention is centered on the prey
as it is killed or carried off. Chips may be taken from any part of the habitat, but they
must be detected by SIGHT ONLY and NOT sought by SLIDING the HANDS over the
habitat. Only 75% of the chips should be captured. Therefore 25 of the chips should
remain on the fabric. Thus, if you are working in teams of 5 each person should capture
15 chips. When you catch your 15 chips, STOP!
Remove the surviving 25 chips try carefully folding and lifting the fabric then pour the
chips into an empty container. Do not mix the 25 survivors with the 75 captured chips.
Next, arrange the survivors in a horizontal row, about one half inch apart, placing those
of each color type together. Each surviving chip produces 3 offspring. Place the offspring
in a vertical column below each parent, using chips from the reserve supply. When all
survivors have reproduced, mix them and their offspring thoroughly and have your
teacher distribute theta as before throughout the habitat. Repeat the entire process until
you have only 25 survivors. Before continuing, make a graph of your 2nd generation
results. Place the color names on the bottom of the graph (horizontal axis) and place the
number of survivors on the vertical axis. Keep your graph for future reference. . Now
your team should move to a different habitat (piece of fabric) and repeat the entire
process through 2 generations, again making a graph of your final results. Before
carrying out the activity the 2nd time you should make some predictions (scientists call
them hypotheses) about what the population of this second habitat will be like after it has
been preyed upon for 2 generations. Based on your results of the first habitat, predict
which color chip you think will have the greatest population in this new habitat after 2
generations. Which chip will have the 2nd greatest population? Which chip or chips do
you think will have the lowest population after 2 generations?
Data
In addition to your 2 graphic and predictions fur the second habitat you should answer the
following questions.
1. What color chips attained the greatest. population after 2 generations in the first
habitat? In the 2nd habitat'.
2. What color chips had the smallest population after 2 generations in the first habitat? In
the 2nd habitat!
3. Were you able to correctly predict the 2 most successful as well as the most
unsuccessful chip color in the second habitat? If not, what color or colors surprised you?
4. Were the populations of the 2 habitats at the end of 2 generations similar or not?
Explain. Can you offer a hypothesis which might explain why some chips were found (or
not fond) as frequently as other chips?
Conclusion
Write a paragraph or 2 that will explain the importance of color to the survival of prey
organisms. (Does one color always have the advantage?)