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Candy Fly Evolution
Introduction
Life has evolved on our planet for billions of years and evolution has created incredibly interesting, quirky, and
unique creatures. But how does life evolve? This activity will take us through the evolution of a make-believe insect, the
Candy Fly. Through only three generations we will see how nature can ‘select’ for certain genes to start the Candy Fly
Evolution.
But, before we begin, we need to describe the Candy Fly. The Candy Fly has a gene that makes it tasty to certain
predators. This gene can have two different versions of DNA that come from the parents (or alleles), the fruity allele (F)
and the chocolaty allele (C). If the Candy Fly has two fruity alleles, then it will taste fruity; if it has two chocolaty alleles,
then it will taste chocolaty; and if it has one of each, then it will taste like a chocolate covered fruit, or frucolaty. We are
going to model the fruity allele with Skittles and the chocolaty allele with M&Ms.
Complete the chart below to show the different alleles that make up each type of Candy Fly.
Taste of Candy Fly (Phenotype)
Alleles Present (Genotype)
Fruity Fly
Chocolaty Fly
Frucolaty Fly
Directions for each experiment
1. Make sure that you have 20 Skittles and 20 M&Ms in your brown paper bag.
2. Without looking, randomly pull out 2 candies (alleles) from the bag and record the taste of the Candy Fly in the
table for each experiment. Do this until all candies are used. This is your initial population.
3. For each generation, predators will eat some of the Candy Flies following certain selection rules (see the
experiments below).
4. Put the remaining Candy Flies back in the bag, and repeat steps 2-3 for a total of 3 generations. Record the data
in the tables.
Experiment 1
When a predator eats the fruity allele, it has an allergic reaction because of the protein that the allele makes. Since both
the Fruity Fly and Frucolaty Fly have the fruity allele, the predator will not eat these flies and will only eat the Chocolaty
Fly.
Write a hypothesis predicting how the Candy Fly heterozygotes and allele frequencies will change. Remember, a good
hypothesis has the format ‘If… then… because.’
Pull out 2 candies at a time and record the type of Candy Fly that these alleles make for the initial generation. Make sure
that you keep the candies together because you’ll need to act like a predator and eat them! After each round, the
predator (YOU!!) will eat every other Chocolaty Fly (half of the Chocolaty Flies) and these alleles will be removed from
the population. Record the surviving flies and alleles in the table and return them to the bag. Repeat this for a total of 3
generations.
Generation
Fruity
Candy Fly Genotypes
Frucolaty Chocolaty
Total
Fruity
Alleles
Chocolaty
Total
Initial
population
Surviving Candy Flies after predation (eating)
Surviving alleles after predation
1
2
3
Graph your data for the Surviving Candy Flies and Surviving Alleles for each generation below.
Experiment 1 Data Analysis
1. Calculate the frequency of Candy Flies and alleles in the initial generation and generation 3.
(Frequency = number of type of Candy Fly / total Candy Flies)
Generation
Initial
population
Frequency of Surviving Candy Flies
Fruity
Frucolaty
Chocolaty
Frequency of Surviving Alleles
Fruity
Chocolaty
3
2. Was your hypothesis supported? Why or why not.
3. How did the frequency of the different Candy Flies change over the 3 generations?
4. How did the allele frequency change over the 3 generations?
5. If you were to do this experiment to 100 generations (assuming you had enough Candy Flies), what would you
predict to be the frequency of surviving alleles?
Experiment 2
In this experiment, predators find out that the Frucolaty Flies are super tasty!! As a result, they only eat the Frucolaty
Flies.
Write a hypothesis predicting how the Candy Fly heterozygotes and allele frequencies will change. Remember, a good
hypothesis has the format ‘If… then… because.’
Pull out 2 candies at a time and record the type of Candy Fly that these alleles make for the initial generation. Make sure
that you keep the candies together because you’ll need to act like a predator and eat them! After each round, the
predator (YOU!!) will eat every other Frucolaty Fly (half of the Frucolaty Flies) and these alleles will be removed from the
population. Record the surviving flies and alleles in the table and return them to the bag. Repeat this for a total of 3
generations.
Generation
Fruity
Candy Fly Genotypes
Frucolaty Chocolaty
Total
Fruity
Alleles
Chocolaty
Total
Initial
population
Surviving Candy Flies after predation (eating)
Surviving alleles after predation
1
2
3
Graph your data for the Surviving Candy Flies and Surviving Alleles for each generation below.
Experiment 2 Data Analysis
1. Calculate the frequency of Candy Flies and alleles in the initial generation and generation 3.
(Frequency = number of type of Candy Fly / total Candy Flies)
Generation
Initial
population
Frequency of Surviving Candy Flies
Fruity
Frucolaty
Chocolaty
Frequency of Surviving Alleles
Fruity
Chocolaty
3
2. Was your hypothesis supported? Why or why not.
3. How did the frequency of the different Candy Flies change over the 3 generations?
4. How did the allele frequency change over the 3 generations?
5. If you were to do this experiment to 100 generations (assuming you had enough Candy Flies), what would you
predict to be the frequency of surviving alleles?
Experiment 3
Here, let’s pretend that the Frucolaty Flies are camouflaged from the predators. As a result, the Fruity Flies and
Chocolaty Flies are easier to find and the predators will eat them instead.
Write a hypothesis predicting how the Candy Fly heterozygotes and allele frequencies will change. Remember, a good
hypothesis has the format ‘If… then… because.’
Pull out 2 candies at a time and record the type of Candy Fly that these alleles make for the initial generation. Make sure
that you keep the candies together because you’ll need to act like a predator and eat them! After each round, the
predator (YOU!!) will eat every other Fruity Fly (half of the Fruity Flies) and every other Chocolaty Fly (half of the
Chocolaty Flies) and these alleles will be removed from the population. Record the surviving flies and alleles in the table
and return them to the bag. Repeat this for a total of 3 generations.
Generation
Fruity
Candy Fly Genotypes
Frucolaty Chocolaty
Total
Fruity
Alleles
Chocolaty
Total
Initial
population
Surviving Candy Flies after predation (eating)
Surviving alleles after predation
1
2
3
Graph your data for the Surviving Candy Flies and Surviving Alleles for each generation below.
Experiment 3 Data Analysis
1. Calculate the frequency of Candy Flies and alleles in the initial generation and generation 3.
(Frequency = number of type of Candy Fly / total Candy Flies)
Generation
Initial
population
Frequency of Surviving Candy Flies
Fruity
Frucolaty
Chocolaty
Frequency of Surviving Alleles
Fruity
Chocolaty
3
2. Was your hypothesis supported? Why or why not.
3. How did the frequency of the different Candy Flies change over the 3 generations?
4. How did the allele frequency change over the 3 generations?
5. If you were to do this experiment to 100 generations (assuming you had enough Candy Flies), what would you
predict to be the frequency of surviving alleles?
F/F (Fruity/Fruity)
F/C (Fruity/Chocolaty)
C/C (Chocolaty/Chocolaty)