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THE CHIPS ARE DOWN:
A NATURAL SELECTION SIMULATION

 

Adapted by Nick DiGiovanni
ENSI 89

Selected by Science Teachers
From NSTA

 

EVOLUTION

Variation and Natural Selection
 NEW ARTICLE: Common Misconceptions about Natural Selection. Go to our Evolution Introduction page, scroll down to bottom of page for "A Few Very Common Misconceptions" and a link to the excellent article that exposes a number of widely held misconceptions, with clues for correcting them (June 2009).
CLICK HERE
For several STEM Applications of Natural Selection

 SYNOPSIS

Demonstrate how natural selection operates, using different colored paper chips to represent prey and a piece of fabric as a background (the environment). The predator (student) will hunt (select chips) to show that the best adapted, by color, are NOT chosen, and others which are poorly adapted (by standing out) ARE chosen (removed). Thus, the best adapted survive and reproduce to pass on their traits. Survivors then "reproduce", and subsequent generations are preyed upon.

 PRINCIPAL CONCEPT

Variation is random. Selection is not.

 ASSOCIATED CONCEPTS

1. Environmental pressures determine the "fitness" of a variation.

2. Traits that are selected for (are "fitter") will be passed on to the offspring.

ASSESSABLE OBJECTIVES

   Students will....

use models to explain how various traits may increase the ability of organisms to survive.

 MATERIALS

Student handout sheet

Different types of colorful floral fabrics (one uniform type for the entire class may be preferred); wall paper, or Hawaiian shirts may also be used.

Containers with paper chips of assorted colors.

These chips can easily be made by using a hole punch and a variety of colored construction paper or acetate sheets. 100 chips is the easiest number to work with mathematically. Depending on your fabrics and construction paper, you may start with 25 chips of 4 different colors, 20 of 5 different colors, or 10 of 10. There should be 100 chips of each color available to each group. You may save the chips to be used again next year. Zip-type bags or envelopes make good storage containers.

 TIME

One 45-60 minute period.
STUDENT HANDOUTS

   (see end of lesson for the formatted handouts).

Student Handout Sheet

 TEACHING STRATEGY

See student handout. The number of chips and colors has been left blank for you to fill in. Feel free to use the data sheet and questions or change them as you desire. Students should work in groups of 3-5.

PROCEDURES

See Student Handout

ASSESSMENT

See Objectives for ideas from which to build a test.

EXTENSIONS

& VARIATIONS   

NOTICE: for STEM:
PRACTICAL APPLICATIONS
of NATURAL SELECTION

A. Other variations for this lab are to use different colored toothpicks (Natural Selection of Stick-Worms") which will be spread out on the grass, colored acetate chips which are spread out on the classroom floor, or colored straws which are mixed into a bale of straw and spread out on the classroom floor. All procedures are fun and inventive. Use what works for you.

B. This simulation procedure can be used to demonstrate other phenomena. For instance:

1) the "predators" could be viewed as "pollinators" and only the remaining flowers (chips) could reproduce; or...

2) two characteristics could be selected together by using chips varying in size or texture as well as color; or...

3) the color vision of predators could be reduced by putting red cellophane shades on them; or...

4) mutants could be added to an already adapted population by adding a new color chip.

If time permits, you may try one of these (for extra credit), or students can make up their own version.

If at all possible, be sure to have your students experience the cumulative aspect of natural selection, and how this creates a high probability for new traits to appear which fit the current selection constratins, and prevail. Try the Natural Selection: A Cumulative Process lesson.

For a good overview of Natural Selection, and an alert to some common misconceptions about it, take a look at the handy summary: "Comparing Evolution Mechanisms" near the bottom of the "Introduction to Evolution" page. Darwin's and Lamarck's essential elements are compared, and a few common misconceptions are clarified. Scroll down to download the PDF file of this information.

 OTHER RESOURCES

National Academy of Sciences. 1998. Teaching About Evolution and the Nature of Science. Activity 3: Investigating Natural Selection. Pages 78-80. This is a well-presented multi-generation lesson, using petri dishes, zip-type bags, pieces of patterned fabric, paper dots, graph paper, colored pencils, and forceps. It also recommends use of computer spreadsheet to facilitate data handling. See the "Resources Section" (Books) on this site for details on getting this excellent resource.

William F. McComas, ed. Investigating Evolutionary Biology in the Laboratory. 1994. NABT. There are several exercises which provide experiences for students to explore natural selection.

NEW ARTICLE: Common Misconceptions about Natural Selection. Go to our Evolution Introduction page, scroll down to bottom of page for "A Few Very Common Misconceptions" and a link to the excellent article that exposes a number of widely held misconceptions, with clues for correcting them (June 2009).

 ATTRIBUTION

Some of the ideas in this lesson may have been adapted from earlier, unacknowledged sources without our knowledge. If the reader believes this to be the case, please let us know, and appropriate corrections will be made. Thanks.

1. Original Source: BSCS Green, 6th Edition

2. Modified by: Nick DiGiovanni (ENSI 89)

3. Reviewed / Edited by: Martin Nickels, Craig Nelson, Jean Beard:

4. Edited / Revised for website by L. Flammer 3/2/99
......Additional minor revisions: 1/6/01


 The following is the Student Handout (2 sides), with background info, procedure, data table, and questions. To get a printout, "select" it then "copy" it (onto your invisible clipboard), then you can shift to your word processor, open a new file, and "paste" it onto that page. Later, you can make changes to fit your circumstances. Alternatively, go to the separate pages linked here, then print each page directly:
"Chips.Introduction.Procedure", and "Chips.Worksheet". In each case, return to this page with the "BACK" key at top of your browser.

Name_________________________________ Date___________ Per.____

THE CHIPS ARE DOWN: A NATURAL SELECTION SIMULATION

INTRODUCTION

The process of natural selection occurs because organisms vary in their heritable characteristics, and because some variants survive and reproduce better than others. As a result, the genetic structure of a population changes through time, which is a factor in evolution. Although evolution may be defined in terms of genetic change, natural selection occurs by the interaction of the environment and whole organisms, and not directly on their genome. The genome is affected by mutations.

In this exercise, we want to reinforce the concept with a demonstration of how natural selection works. It is far too time-consuming to observe natural selection at work in natural populations, so we will use artificial populations consisting of paper chips.

PROCEDURE
1. Spread out the fabric or paper habitat given to you by your teacher on the table top.

2. Count out ____ chips of each of the ____ colors for a total of 100 as your initial population.

3. Appoint one person as the prey (chip) distributor. That person should spread the chips out randomly over the entire fabric, making sure the chips do not stick together. The other members of the group should have their backs turned during this procedure.

4. The predators (other members) should turn around and take turns picking off the prey (chips) one by one until only 25% remain. COUNT CAREFULLY. Predators are to take the first chip they see and follow each chip to the discard area with their eyes so as not to see more chips, and keep track of the number of chips they get.

5. Carefully shake off the fabric to remove survivors (remaining 25 chips).

6. Group the survivors according to color. Count and record these numbers.

7. Assume each survivor produces three offspring. Using the reserve chips, place three chips of the same color with the survivors (i.e., take the number of survivors multiplied by 4).

8. Mix these chips together and re-distribute them as in step 3.

9. Repeat the entire process two more times, making a total of three generations of prey being preyed upon.

(OPTIONAL) The teacher may require students to do a population growth lab of each of the colored chips to show quantitative results and search for a pattern in survival.

 Name_________________________________ Date___________ Per.____

CHIPS ARE DOWN....Data Sheet

PURPOSE:

 

DATA:
 

COLORS
         

 Number at start-->

         

 # after 1st predation-->

         

 # after 1st reproduction-->

         

 # after 2nd predation-->

         

 # after 2nd reproduction-->

         

 # after 3rd predation-->

         

REVIEW QUESTIONS:

1. Study your survivor populations.

a) Was 1 color of paper chip represented more than others in the first generation of survivors? _____

b) Were shades of that color or similar colors also present? ______

c) What, if any, change occurred between the 1st and 2nd, and again between the 2nd and 3rd generation of survivors?

 

 

 

2. Compare the original and survivor populations. Is there any color from the original population that is NOT represented in the survivor population? _____ If so, what color (or colors)?

 

 

3. Examine your survivor chips and the fabric from which you took them. How do you think the colors of the survivors are related to their habitat?

 

 

4. Write a conclusion as to which colors survived in the habitat and which did not, and why. Try to extrapolate this to a natural situation.

 

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