Download Natural Selection Lab

Jolly Rancher® Evolution Lab
Purpose: to illustrate how populations can change in response to natural selection and other
evolutionary mechanisms.
Background: You have been the unwitting predators in an experimental model of how natural
selection affects populations. Evolution, at its most basic level, can be defined as any change in
the frequency of alleles in a population of organisms from generation to generation. During the
class period, your benevolent teacher has been offering you pieces of Jolly Rancher® candy in
class. This was an experiment to see if students (predators) had a preference for certain
flavors/colors of Jolly Rancher®, and whether such preferences could influence the relative
frequencies of the flavors over time.
The initial population consisted of equal frequencies of four flavors: 25% grape, 25%
watermelon, 25% Green Apple and 25% blue raspberry. Following each offering, the survivors
of the feasting (by YOU, the predators) reproduced, each spawning one offspring of the same
color (example: if there were 8 watermelon survivors, then there would be 16 watermelons at the
beginning of the next offering). Thus, color/flavor was passed from parent to offspring.
Instructions: Your group is being provided with the raw data from this experiment. Each
column of data shows the numbers of each flavor BEFORE being eaten by ravenous students.
1. Convert the raw data from your class into percentages by dividing each flavor amount by
the sum of all flavors on that day and multiplying by 100.
Example (from initial time t=0): 8 grape/32 total = 0.25 x 100 = 25%
Change in Jolly Rancher Flavor Population Percentage Over Time
t=0
t=1
t=2
t=3
Grape
8
12
24
46
Green Apple
8
12
20
36
Watermelon
8
10
10
14
Blue Raspberry
8
10
12
18
t=0
t=1
t=2
t=3
Grape
Green Apple
Watermelon
Blue Raspberry
25%
2. Make a line graph of the percentage data for each flavor on graph paper (use different
colors to represent the different flavors). Be sure to label your axes and title your graph!
3. Answer the questions below IQIA on a separate piece of notebook paper) (use scientific
definitions of terms). Attach your answers to the graph and hand in.
Questions:
1. Describe the variability in the initial population of Jolly Ranchers® (what colors/flavors
were present in the beginning of the experiment?). In our simulation, is this variability
heritable?
2. Describe, in words, what you observe about the relative frequencies (% of total
population) of each of the Jolly Rancher® flavors in your class over time.
3. According to your class’ data, rank the popularity of each of the Jolly Rancher® flavors:
Most Popular:
Second:
Third:
Least Popular:
4. What is an adaptation or adaptive trait (evolutionary definition)?
5. Which trait(s) could you conclude to be an adaptation for Jolly Rancher® in your class?
Explain.
6. Look at data from previous years. Do you think the adaptation(s) from your answer to
question #5 would be considered an adaptation in all other classes as well? Explain your
answer.
7. Has evolution by natural selection occurred in our simulation? Why or why not?
8. What would you expect would happen over time if a [insert most popular flavor here]
Jolly Rancher mutated in the beginning to look like a [insert least popular flavor here]
one? Explain.
9. Given the exact same experimental parameters (your teacher doubling Jolly Ranchers by
color, etc..), describe in detail how you could have simulated artificial selection
assuming that you knew what was going on at the start of the experiment. In other
words, how could you have selected for the trait(s) that you wanted.
10. This is a simulation of how natural selection drives changes in actual organisms.
a. Describe TWO sources of genetic variation in organisms for natural selection to
act upon.
b. Identify and describe ONE example of an organism that has a NEGATIVE impact
on humans that is being selected for in an analogous way to this simulation.