E5aTeddy

NATURAL SELECTION WITH TEDDY GRAHAMS

INTRODUCTION

Many people erroneously believe that animals conscientiously change, or adapt, to fit their environment. A common example is the color change of certain animals to mimic others or to blend in with its environment. Animals cannot actively change to fit their environment. Natural selection is the process that acts to produce animals that are better adapted in their environment by eliminating individuals that do not have the characteristics needed for survival and reproduction. Characteristics then that do help an individual to survive and reproduce in a particular environment are adaptations. The end result of natural selection is adaptation to the environment.

PURPOSE

To demonstrate the concept of natural selection using Teddy Graham crackers

SAFETY

Observe standard rules of laboratory safety.

MATERIALS

Teddy Grahams

Paper towels or napkins

Calculators

PROCEDURE

  1. Read the following story before beginning the lab, and follow directions carefully:

You are a bear-eating monster. You like happy-bears because they taste sweet and are easy to catch. Sad bears are not part of your diet because they are bitter, sneaky, and impossible to catch. For this reason, you eat only Happy bears.

New bears are born every ‘year’ (during hibernation) and the birth rate is one new bear for every old bear left from last year.

  1. Form a hypothesis about what you expect to happen to the number of Happy and

Sad bears over time. Write your hypothesis in the space provided on the student data sheet.

  1. Obtain a population of bears from your teacher.
  1. Record in Table 1 the number of Happy bears, the number of Sad bears, and the Total Population of bears you have.
  1. Eat three Happy bears. If you don’t have three Happy bears, then eat the number of Happy bears you have.
  1. Determine the number of Happy bears and Sad bears that will be produced during hibernation (each remaining bear will produce one new bear), and then get the new generation from the teacher.
  1. Repeat step 3-5 for the second generation.
  1. Repeat for two more generations (total of four).
  1. Determine the percentage of Happy and Sad bears for each generation and record the percentages in Table 2. To determine the percentage take the number of happy or Sad bears and divide by the total number of bears for that generation and multiply the answer by 100. For example, if there were 12 Sad bears and 4 Happy bears in a generation, then there were 16 bears total. To obtain the percentage of Sad bears you would divide 12 by 16 and then multiply the answer by 100. To obtain the percentage of Happy bears you would divide 4 by 16 and then multiply the answer by 100.
  1. Graph what happens to the bear population over time. Graph the percentage data for both the Happy and Sad bears on the same graph.
  1. Answer the questions after completing the graph.

Revised RDB July 2006ASIM:EvolutionPage 1 of 4

E5aTeddy

STUDENT DATA SHEET NAME______

NATURAL SELECTION DATE______

WITH TEDDY GRAHAMS

HYPOTHESIS

______

DATA

Table 1. The number of bears for each generation

Generation / Number of
Happy bears / Number of
Sad bears / Total Population
of 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

QUESTIONS

  1. What was the total number of bears at the start (i.e., generation 1)?
  1. Did the total bear population bears increase or decrease over time (generations)?
  1. What happened to the percentage of each type of bear over time?

a)Happy?

b)Sad?

  1. How does this compare with your hypothesis?

Revised RDB July 2006ASIM:EvolutionPage 4 of 4