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Natural Selection With "Teddy Grahams"

By Lynn Marie Wartski



TYPE OF ACTIVITY:

Class lab activity

TARGET AUDIENCE:

  • Life Science
  • Biology
  • A.P. with optional Hardy-Weinberg adaptation.

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.

BACKGROUND INFORMATION:

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 considered.

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.


ACTIVITY:

Summary/Abstract:

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 pressure.

Materials:

Bears: Happy and Sad (Teddy Graham crackers)
Graph Paper

Procedure:

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 population results.

Story:

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 generation.

Hypothesis:

What do you expect to happen to the number of Happy and Sad Bears over time?

Results:

Number of bears at the start? ______. This is generation one.


Table 1: The number of bears for each generation
Generation Number of
Happy Bears
Number of
Sad Bears
Total Bears
1
2
3
4

Table 2: The percentage of bears for each generation
Generation Percentage of
Happy Bears
Percentage of
Sad Bears
1
2
3
4


Graph the data from table 2.

1) Graph what happens to the bear population over time.

Key:
Graph Percent of Happy Bears as: ________
Graph Percent of Sad Bears as: ........

Conclusion:

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?
  1. Happy?
  2. Sad?
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/Reinforcement:

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.


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