Download Natural Selection Bean Muncher Activity

Simulation of Evolution by Natural Selection: “Bean Munchers”
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The theory of evolution by natural selection is based on three important conditions which are described below:
Condition 1: There is variation in the traits of characters amongst the individuals in a population.
Look around you at the other students in your class. Everyone looks different, don’t they? It probably comes as
no surprise to you that in a human population there is a certain amount of variation in the traits. That is to say
that people have differences; no two people (except identical twins) look exactly alike – some might have longer
arms, some might have longer legs, some might have broader shoulders, more pointed teeth, etc. The same is true
in all populations of animals and plants – there is a certain amount of variation in traits.
Condition 2: Many traits or characteristics are heritable. This means they can be passed on from parents
to offspring.
Now think of your parents. You are definitely NOT exactly the same as either one of them. But, you probably
resemble each of them in quite a few ways. Similarly, your parents probably resemble your grandparents, and your
children will probably resemble you. This is also true in all animals and plants – although offspring are no exact
copies of parents, they do resemble them in quite a few ways. Traits that can be passed from parents to offspring
are called heritable. Most traits that are heritable are genetic – for this reason, many scientists who study
evolution today use genetics and DNA as their primary tools.
Condition 3: There is reproductive success based on those heritable variations. This means that those
individuals who have traits that are better adapted to their environment not only survive better, but they
also have more offspring.
You probably have heard the phrase “survival of the fittest” as an explanation of Darwin’s theory of evolution, but
that is not exactly an accurate description. It is true that according to the theory of natural selection, those
organisms that are better adapted to their environment do survive better than those who are not as well adapted.
But that is not enough. According to the theory of natural selection, there must be reproductive success- the
individuals that are best adapted to the environment survive better AND have more offspring than those that
were not as well adapted. For this reason, fitness is defined as an individual organism’s ability to survive AND
reproduce.
Putting it all together: The theory of evolution based on natural selection states that organisms with traits that
are better adapted to their environment are better able to survive and reproduce. When they reproduce, they
pass their beneficial traits on to their offspring, and over many generations, this causes the traits in a population
to change. These changes in populations eventually lead to changes in the species – evolution.
Materials:
Small cups – 1 per student
Plastic spoon – 1 per student
Plastic fork – 1 per student
Plastic knife – 1 per student
Beans – 1 to 2 pounds
Procedure:
You are all members of a single species of voracious predators known as the Bean Munchers. You eat beans. In
your world, if you eat enough beans, you will survive. If you don’t eat enough beans, you will die. Those who eat the
most beans will survive and reproduce. Here are the rules of the game:
1) Although you are all members of the same species (Bean Munchers), some of you have different mouths
than others. Some of you will have spoon mouths, some of you will have fork mouths, and some of you will
have knife mouths. We will start with equal numbers of spoon mouths, fork mouths, and knife mouths.
Record the numbers (Starting Population Size) in the data table for Generation 1.
2) You each will have a cup stomach. Your stomach must stay upright at all times. If your stomach tips to one
side, you automatically must empty the contents of your stomach and you will die.
3) In order to eat your prey (beans), you must use your mouth to put the bean into your stomach. During each
generation, you will have 40 seconds to eat.
4) At the end of each generation, each bean muncher will count the number of prey caught and record their
data in the table.
5) Results will be tabulated for each feeding adaptation (mouth) and the average number of prey will caught
will be calculated using the formula: SHOW YOUR WORK!
Formula for calculating Average:
Total Prey from: forks + spoons + knives
# of Bean Munchers
6) All individuals below the average “die” without reproducing, and must turn in their utensil.
7) Record the number or survivors for each mouth part.
8) Survivors (those individuals above the average) produce an “offspring.” The survivors keep their mouth and
receive an identical mouth that they “pass on” to their offspring (a student they choose from the nonsurvivors).
9) The “Final Population Size” (survivors and offspring) for each mouth part is recorded.
10) You will again have 40 seconds to feed for the second generation. Tabulate the results, calculate the
average, determine the number of survivors, and arrive at the final population size. The game will end after
three generations.
Simulation of Evolution by Natural Selection: “Bean Munchers”
Name: ______________________
DATA TABLE 1:_____________________________________________________________
Mouth Types
Starting Population Size
Surviving Population Size
Final Population Size
(post reproduction)
Forks
Spoons
Knives
DATA TABLE 2:______________________________________________________________
Mouth Types
Forks
Spoons
Knives
Starting Population Size
Surviving Population Size
Final Population Size
DATA TABLE 3:______________________________________________________________
Mouth Types
Forks
Spoons
Knives
Starting Population Size
Surviving Population Size
Final Population Size
Total Prey Caught For Each Generation
1
Total
PreyForks
Total
PreySpoon
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
Total
Generation 1
Ave Prey: ______
Total
PreyKnives
2
Total
PreyForks
Total
PreySpoon
Total
PreyKnives
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
Total
3
Total
PreyForks
Total
PreySpoon
Total
PreyKnives
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
Total
Generation 2
Ave Prey: ______
Generation 3
Ave Prey: ______
Discussion
1) What is Condition 1 of natural selection? Describe how the Bean Munchers met this condition?
2) What is Condition 2 of natural selection? Describe how the Bean Munchers met this condition?
3) What is condition 3 of natural selection? Describe how the Bean Munchers met this condition?
4) What is fitness? In our Bean Munchers world, which Bean Munchers were most fit? Which were the least
fit?
5) Explain how natural selection occurred amongst the Bean Munchers.
6) According to the theory of evolution based on natural selection, individuals do not evolve, but populations
and species do. Explain what this means.
7) Due to ozone depletion and global warming, the weather patterns of the Earth have shifted, causing
BeanMuncherLand to become very tropical. Now the beans (prey) are long and stringy, very similar to
spaghetti. Predict how this will affect the survival of the Bean Munchers and explain why it is important to
have variation in populations when environmental conditions change.
8) In the Bean Munchers lab, explain why the average number of prey caught keeps going up.
9) Does having the best suited adaptation guarantee your survival? Explain in terms of the lab.
10) Does having an adaptation that may not be best suited for the environment guarantee you don’t survive?
Explain why this might be.