Candy Critter Genetic Variation Lab

Students will analyze data and identify patterns in how traits in a population can change over time in this activity. In nature, individuals of the same species are not alike. They will differ in some way genetically. We call these differences in appearance and behavior, genetic variations. The traits you see expressed in an organism is called the phenotype.

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In this activity, the phenotype being looked at closely is the color of the "candy critter". Some genetic traits help an organism survive in its environment and gives the organism some sort of advantage, while other traits do not offer any advantage or may even be a disadvantage.

Natural selection is the name of this process by which nature and its environment favor certain traits or behaviors over others. Some traits are helpful in an organism’s environment and so we see more of it in a particular species. The organisms with the advantageous trait are more likely to survive, reproduce, and pass this advantageous trait down to their offspring. Some traits offer a disadvantage and will be a factor that can, in time, lead to the extinction of a species.

In this easy set up lab, the candies will represent a species (candy critters) in a particular environment.  I like to use Skittles for this activity, but really any colored candy pieces will do so long as you have these five colors: green, yellow, blue, red, and purple.

Materials:

1. One regular size, original flavor Skittles package (one pack for two students, or one

pack for a table of four).

2. Construction paper-green, yellow, red, blue & purple, or aquarium rocks in these colors

3. One paper towel and one paper cup per table

4. Hand sanitizer

Personally, I prefer the colored aquarium rocks (Paid link) rather than colored paper for this lab because the candy pieces blend in better with the texture of the rocks. The candy that is the color of the rocks will be more camouflaged than when using a flat, colored paper. If you end up using the rocks, you can save them at the end of the day, store them in plastic bags to use again for the next year. Of course, if you are on a budget, and you want to spend less, go with the colored paper. It will cost you a lot less than the rocks.

Set Up:

Have students sit in groups of four, if possible. Each table will need one paper towel, a small tray with a colored background (This will be the organism’s environment), a pack of regular-sized Skittles, and one hand sanitizer or hand wipes. If you intend for students to eat the candy after the lab is finished, you can have them clean their hands before touching the candy.

*Each group will have a different color background in their tray. Some will have a green background, others will have red, others purple, blue or yellow. Remember, the background will be either gravel rocks or construction paper (whichever you choose to use).

Procedure:

1. First, have students empty the entire content of the candy bag on to the paper towel.

2. Next, have students separate the candies into groups based on color, like in the

picture:

3.  Students will now count the total number of skittles and record this number on the data chart (at the bottom where it says total # of candy).

4. Next, they will count the total number of each color of candy they have and record this information on the data chart (first column).

5.  After they have done that they will calculate the percentage of each color (second column). To calculate the percentage, take the number of each color and divide each by the total number of skittles that were in the bag. Example: If you had 10 red skittles out of 40 total skittles in the bag- 10/40=.25 or 25% 

6. Now a student in the group will place ALL the different colors of candy on the tray that is lined with either construction paper (or rocks). See the pictures below. You can see we used the aquatic rocks (my preference) in these trays.

You can see that the green Skittles blend in more with this background than the other Skittles.

Here, you can see that the red background makes it easier for the red Skittles to blend in. The other Skittles are much easier to spot.

7. Now that the setup is ready, students are ready for their “first attack”. The person in the group who will be quickly grabbing a skittle in each “attack” will be acting as the predator to the skittle organisms. You can have each student get a turn to do this. The predator will be asked to turn around and look away from the table for 4 seconds. Tell this person that they are visual predators meaning they eat the prey that stands out the most in their environment.

8. When the rest of the group is ready, someone will call out, “Attack!” at which point the “predator” will turn back to face the table and quickly grab some skittles at random. Make sure

to tell this person they can only pick up one skittle at a time and place it in a plastic cup.

9. Someone in the group will keep time. Give each attack no more than 3-4 seconds. Once the 3

seconds is up, the timer student will say stop and the predator will immediately stop collecting

candies.

10. Finally, students will count how many of each color is left and calculate the number and percentages of each color. They will record these numbers in the designated spots on the data sheet where it says, “First Attack”.’ Do not return the removed skittles to the tray. The collected candies will remain in the cup until the activity is finished (All four attacks completed).

11.  Students will then repeat steps #6-10 until they compete all 4 rounds of attack.

*For a free post-lab worksheet and two data table handouts for this activity, click HERE.