Natural Selection With "Teddy Grahams"
TYPE OF ACTIVITY:
Class lab activity
Lab will help student/groups to answer the question of how natural selection can effect
the frequency of a single trait in a population through successive generations.
- Life Science
- A.P. with optional Hardy-Weinberg adaptation.
Teddy Grahams (now Dizzy Grizzleys) are little graham crackers that come in the shape
of bears. On close inspection one will notice that
the crackers in the box come in two shapes: with their hands up, and
with their hands down.(or on wheels or without wheels) They crackers
present themselves as a population with members possess one of two
possible observable forms of a trait. This makes them very convenient
to use in a natural selection activity.
Preparation for Natural Selection with Teddy Grahams requires either
the purchase of Teddy Graham crackers, or photocopying and cut out of
paper bears to simulate the crackers. Amount of crackers is dependant
on number of students in class, average about two - three boxes per
class. Preparation of a lab involving food consumption should also be
Students need only a writing instrument and graph paper to complete lab.
Class time needed is one hour class period with possible additional time for completion
of graphs and questions.
This lesson provides student/groups with insight into the effect on a population from
the process of natural selection. Data is gathered on the appearance of two phenotypes
over successive generations as a specific selective force is applied. Students graph phenotype
percentages to provide a visual representation of data collected during procedure.
Story set-up and cracker "prey" place student in the center of activity as the selection
Bears: Happy and Sad (Teddy Graham crackers)
1) Read the story and follow directions.
2) Obtain a population of bears, and record in table 1 the number of each: The Total
Population, the Happy Bears, and the Sad Bears.
3) Eat three Happy Bears. If you don't have three Happy Bears, then eat what you
have in Happy Bears.
4) Get a new generation from the teacher. Repeat steps one and two.
5) Repeat for two more generations (total of four).
6) Determine the percentage of sad and happy bears for each generation
(devide the number of that type of bear by the total number in that
generation), record the percentages in table 2, and graph the
You are a bear-eating monster. There are two kinds of bears: Happy
Bears and Sad Bears. You can tell the difference between them by the
way they hold their hands. Happy Bears hold their hands high in the
air, and Sad Bears hold their hands down low. Happy Bears taste sweet
and are easy to catch. Sad Bears taste bitter, are sneaky, and hard
to catch. Because of this, you eat only Happy Bears. New bears are
born every 'year' (during hibernation) obtain another handful of bears
if two or more are left in your population from the previous
What do you expect to happen to the number of Happy and Sad Bears over time?
Number of bears at the start? ______. This is generation one.
|Table 1: The number of bears for each generation
|Table 2: The percentage of bears for each generation
|Percentage of |
Graph the data from table 2.
1) Graph what happens to the bear population over time.
Graph Percent of Happy Bears as: ________
Graph Percent of Sad Bears as: ........
1) How many new bears did you get for each generation?
- Generation 2 ____
- Generation 3 ____
- Generation 4 ____
2) What happened to the percentage of each type of bear over time?
3) How does this compare with your hypothesis?
Method of Evaluation:
Students are graded on completion of lab, accuracy of data collection
and manipulation, graphing, and response to conclusion questions.
Extension of this activity can include the application of the
Hardy-Weinberg equilibrium in mapping gene frequencies over the
successive generations of bears using the same data. The same
experimental results can be used. The graphing of the gene
frequencies rather than phenotype percentages in this case, provides
students with an illustration of the effect on the equilibrium when
natural selection occurs.