Lesson Plan on Competition
Entry Title: Competition
Lesson Focus: Individual organisms with certain traits are more likely to survive and have
offspring than individuals without those traits.
Connection:
Changes in environmental conditions can affect the survival of individual organisms with a particular
trait
Students know variation within a species increases the likelihood that at least some members of a
species will survive under changed environmental conditions.
Mini-lesson:
Competition is an interaction between living things, most especially between species by which the
capability of an organism is reduced by the presence (maybe introduced) of another. This is caused by
the reduction of a need (e.g. air, food, space).
Intraspecific Competition = Competition among members of the same species
Interspecific Competition = competition between individuals of different species
Competition is not always straightforward, and can occur in both a direct and indirect fashion.
According to the competitive exclusion principle, species less suited to compete for resources should
either adapt or die out. According to evolutionary theory, this competition within and between species for
resources plays a critical role in natural selection, however, competition may play less of a role than
expansion among larger groups such as families. 1
1 Sahney, S., Benton, M.J. and Ferry, P.A. (2010). "Links between global taxonomic diversity, ecological diversity and
the expansion of vertebrates on land" (PDF). Biology Letters 6(4): 544–547.
Work Period:
A. Do Now : Which organism do you think will survive better in a polluted
environment? Why?
B. Activity
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.
C. Explain: 1. Discuss per group your observations and answers to the
questions. 2. A representative in each group will share to the whole class
the main observation you had. 3. Ask a question or clarification
D. Reading for further understanding
Competitive exclusion in ecology
http://www.sciencedaily.com/articles/c/competitive_exclusion_principle.htm
E. Looking back at your answer to the DO NOW, has your response
changed? Why or why not?
Closing/Assessment: Exit Slip
Explain in detail why USA does not allow fresh fruits and vegetables and animals
to be brought to the country without proper documents?
Homework: Research laws that are implemented in the state of NY that
safeguards the native species of plants and animals . Summarize each in your
own words
Resources:
Activity: http://www.indiana.edu/~ensiweb/lessons/ns.chips.html
Worksheet
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.