Candy Dish Selection
Author: Carol Tang
Overview: In this lesson students become
unwitting subjects in a demonstration of natural selection. Students select
candies from a bowl and have an opportunity to think about what traits brought
about the survival of some candies.
- Not every feature is an adaptation.
- Adaptations often persist in a population
because they are in some way advantageous.
- Adaptations are preserved in a population
by natural selection.
- Depending on environmental conditions,
inherited characteristics may be advantageous, neutral, or detrimental.
- Random factors affect the survival of
individuals and of populations.
- Natural selection acts on individuals
and populations in a nonrandom way.
Grade Span: 912
- Variety of candieshas to include popular ones and unpopular ones (try 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).
- Large dish
Prepare a list of the candies and their initial abundance in the candy dish.
Time: 30 minutes
Grouping: Whole class
This activity provides a model for natural selection. It is, of course, artificial
both in the sense that the selecting is done by people and that the organisms
being selected are nonliving entities with no genetics and no ability to reproduce.
Charles Darwin, in modeling natural selection, used the artificial selection
of pigeons to illustrate how selection can, over time, modify populations
of living things. This activity is at least one additional step removed from
the reality of natural selection, but it provides one way to illustrate the
mechanism. The concept of natural selection should, of course, be pursued
in many other ways in order to help students understand its centrality to
Explore these links for additional information on the topics covered in this lesson:
Vocabulary: variation, selection, traits
- Make the candy dish 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.
- 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
- 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.
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.
This activity was first suggested to me by Jack Laws, associate at the
California Academy of Sciences, during an informal conversation.
Updated November 20, 2003
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