Activity: Candy Dish Selection

return to
Lines of Evidence
for Past Change

Classroom activity:
Candy Dish Selection

Carol Tang, California Academy of Sciences

Materials:

A variety of candies- has to include popular ones and unpopular ones (try Circus Peanuts or black licorice). You should have at least two candies per person plus plenty of unpopular ones. Possibly include candies with different colors, sizes, brand names, etc. (Avoid candies with nuts for kids who are allergic.)

Preparation:

Prepare a list of the candies and their initial abundance in the candy dish. The candy dish either can be made accessible in advance so students can pick candies over a period of time, or the dish can be passed around the room a couple times. You can avoid commenting about it at all, or you can make very innocent remarks about providing a treat for the students.

Debriefing:

After more than half of the candy has been removed, gather the class together. Start the discussion by pointing out that there is often great variation among individuals of animal species. For example, students can look around the room and list the characteristics that vary among humans. Then, ask the students why variation is significant.

One reason variation is important is that variation allows for differential survival of individuals. Show them the candy bowl and the remaining candies. Count what candies remain and list them on the board. Ask them if they remember which candies were originally available. Make a list on the board of the original set of candy.

Now ask them to list the traits of the candy they selected from the candy dish. (examples include: chocolate flavor, large size, favorite brand, etc). These are the traits that led to the removal of certain candies.

Make a list now of the traits of the candies that were not selected (examples: bad flavor, small size). These are the traits that allowed the candies to survive being passed around the room.

So, the fact that there were different candies with different traits resulted in some candies being eaten and others surviving. This is what natural selection does with individuals in a population. Each individual has unique traits; some traits will help an individual survive and some traits do not.

Extension:

A teacher could continuously add candy into the candy bowl according to the proportions left in the candy bowl. For example, if after the first round all the Hershey kisses disappeared but there were a lot of green Starbursts, add more green Starbursts but do not add any more kisses. This will accentuate the loss of favorite candies and the proliferation of the remaining ones. In addition, this extension will simulate the production of new generations, similar to the evolution of populations over time.

Another possibility is that you will see students taking their second choice of candies, simulating the natural situation where predators will start consuming another prey item when their favorite prey item is eliminated.