Evolution of Skittlelicious delicious
The phenotypic alterations of a terrestrial animal can be followed within the context of a
classroom simulation activity. The frequency of carapace (covering) colors may vary in
response to environmental selection pressures. In this simulation, a predator hunts for
Skittlelicious delicious (S.d.) within a given multi-colored environment. After 3 rounds
(generations), carapace color frequencies can be compared to the original frequencies to
determine the effects of selection pressure on the trait of carapace color.
Materials:
2’ x 2’ Fabrics (colorful floral designs are recommended, provide different patterns and
especially colors so that teams can “see” how the environment can select phenotype),
Skittles (colored paper cutouts or other candy would also work), paper cups (or other
suitable containers), forks and spoons (optional).
Procedure:
1. Assign the following roles to each member of your team: predator, placer, and
recorder.
2. Separate the five different color S.d. into five separate cups. Place at least 20 in
each cup.
3. With the predator turned away from the cloth “environment,” recorder and placer
should place 5 of each S.d. on the cloth (be sure to have the characteristic “S”
design on the carapace facing down). Be sure to hide the S.d. as effectively as
possible.
4. At a given signal, the predator turns to face the environment and collects the first
S.d. seen. The predator must immediately turn away from the environment,
choosing to either eat the S.d. or store in a capture cup.
5. The predator proceeds to repeat step 4 until 13 of the 25 total S.d. are collected.
6. At this point, the team counts and records the total number of each color
remaining.
7. To conclude the round (generation), the team doubles the population of S.d. by
adding the same amount of given color as remains. For example, if 3 red remain,
3 more red are added to the environment. This reproduction is a vital part of the
natural process.
8. Members of the team now switch roles and repeat steps 3-7 for two more rounds
(generations).
9. The exercise can be continued by providing a different cloth environment to the
team, followed by a repeat of steps 1-8. This allows the students to assess the
effects of background environment on the carapace color frequency of S.d.
10. Student teams should present the data in the form of a histogram (bar graph), with
associated text explaining the results in the context of evolutionary language.
Options:
- Provide feeding tools for predator, such as spoons, forks, or knives.
- Alter the feeding tools of the predator over time, simulating the co-evolution of
the predator in this predator-prey relationship.
-
Have the predator wear goggles with various color filters. Alter these over time
(or between groups) to again simulate co-evolutionary responses.
Have a particular color of S.d. alter orientation by placing them with “S” side up.
This behavioral variation can be investigated for predator response.
Before you begin your experiment.
1. Predict the populations of each color at the end of the experiment based on your
background environment.
Start Round 1
End round 1
Start Round 2
End round 2
Start Round 3
End round 3
Red
Orange
Yellow
Green
Purple
Red
Orange
Yellow
Green
Purple
Red
Orange
Yellow
Green
Purple
Please answer the following questions using chapter 16 from your book
1. What is the purpose of this lab?
2. Define gene pool
3. What would you describe as the gene pool of skittlicious delicious?
4. How did the gene pool change as the activity proceeded?
5. Define phenotypic frequency
6. How is phenotypic frequency computed?
7. What is the Red phenotypic frequency at the beginning of each round? Show work.
Round 1
Round 2
Round 3
8. What happens to a population at Hardy-Weinberg Equilibrium?
9. Why does this experiment deviate from Hardy-Weinberg Equilibrium?
10. Which of the 5 assumptions of Hardy-Weinberg Equilibrium is broken in this
experiment?
11. Which type of Natural Selection is the population of Skittlicious Delicious
undergoing; Stabilizing selection, Disruptive selection, or Directional selection? and
why?
12. How is gene flow different from genetic drift?
13. Is there any example of gene flow in this activity?
14. How could you simulate gene flow in this activity?
15. How could you simulate mutation in this activity?
16. Define speciation.
17. What type of environment might lead to speciation of Skittlicious Delicious?
18. Describe the morphology of Skittlicious Delicious?
19. How could you simulate geographic isolation in this activity?
20. Estimate the generation time of Skittlicious Delicious.
21. How might generation time affect the speciation of Skittlicious Delicious into 2 new
species?