Candy Critter Genetic Variation Lab

In this Candy Critter Genetic Variation lab, students will analyze data and identify patterns in how traits in a population can change over time. 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. 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; they give them some sort of advantage. While other traits do not offer any advantage and may instead 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 a lot of it in a particular population of species. These organisms 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 may ultimately 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

For #2 in materials-Personally, I prefer using aquarium rocks rather than colored paper because I think the candy pieces blend in better with the rough texture of the tiny rocks, and it looks neater. I bought my aquarium gravel on Amazon and loved the ones I got. I bought my rocks for about $15 a pack, so for five colors you are looking at around $75 total. You can reuse the rocks by having them collected at the end of the day and placed in plastic bags.

 But if you want to spend less money, go with the colored paper. It will cost you a lot less to buy this than colored aquarium rocks. 

Set Up:

Each table, preferably with groups of four students, 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, purple, blue or yellow background, which 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.

Candy critters in red background (aquarium rocks)

Candy critters in green background (aquarium rocks)

7. Now that the set up 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 their

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.