A Fishy twist on Adaptations

Station 1
A Fishy Twist on Adaptations
Introduction
Does the coloration of an animal affect its chances for survival? Do feeding mechanisms alter an organism’s chance
of living? How could an organism’s reproductive strategy affect the individual? How could it affect the species?
Throughout time, people have marveled at the vast diversity found in nature. Adaptations have led to the vast array
of variation and have resulted in the enormous diversity among species. There are also pressures in the environment
which can select for those organisms best suited for survival. These are called selective pressures; the adaptations that
best help organisms in the environment will be favored and organisms possessing them would be favored for survival.
Procedure
•Design an underwater habitat. What sources of food are there? What color is the habitat? What hiding places
could there be? On poster paper, draw and color the habitat.
•Draw a fish to live in this habitat. Choose specific adaptations for body shape and structure, jaw shape and
structure, and coloration. Design, color, and cut out the fish. Tape it into its habitat. List and describe the fish’s
adaptations. How does it move around? How does it catch and eat its food? How does it hide from predators?
How does it signal to a mate of the same species?
•Assign your fish a scientific name, including a genus (first name, capitalized) and species (second name, lower
case). Both names should be italicized or underlined.
• Answer Analysis Questions 1 & 2
• Next, place your fish in another group’s habitat.
• Answer Analysis Questions 3–8
Analysis Questions
1) How is your fish adapted to the habitat in which it lives?
2) Which adaptations are most important to your fish’s survival in this habitat?
3) List and justify any adaptations that will limit the success of your fish in its new habitat.
4) List and justify any adaptations that will increase the success of your fish in its new habitat.
5) Using your answers from questions 3 and 4, predict what would happen over time to your fish species in the
new habitat. Predict what would happen over time to the population of this fish species in the new habitat.
6) Which adaptation is most important for the survival of the individual fish? Please explain your reasoning.
7) Which adaptation is most important for the survival of the fish species? Please explain your reasoning.
8) What role do adaptations play in Darwin’s theory of Natural Selection? Please be specific.
The Field Museum • Chicago Center for Systems Biology
Genes, Traits, and Individuals • Student Pages • Station 1 • Page 1
Station 2
Skull Morphology
Introduction
Over the course of evolutionary time, descendants become different from their ancestors. Animals that have a recent
common ancestor often share more characteristics than animals that have a more ancient common ancestor. Traits
that are similar to one another because they were inherited from a common ancestor are homologous traits. Your
nose is homologous to a dog’s nose, because the last common ancestor of humans and dogs had a nose that was
made of cartilage, located in the middle of its face, and was used for smelling. For the same reason, your nose is
homologous to an elephant’s nose, even though they look very different! However, your nose is not homologous to
a bird’s beak, because the last common ancestor of mammals and birds did not have a beak, and the bird’s beak and
our nose are derived from different ancestral structures (the upper and lower beak of a bird are homologous to our
jaws, as both structures are made up of the maxilla and mandible bones).
How do we know what traits an ancestor had, since it doesn’t exist today? We use a tool called parsimony, which
states that the simplest explanation is probably the correct one. Is it more likely that the last common ancestor of
birds and mammals evolved a beak, and then mammals lost their beaks (two assumptions), or that the last common
ancestor of birds evolved a beak (one assumption)?
By observing different traits of animal skulls, homology can be inferred and used to make hypotheses about
common ancestry.
Procedure
•Examine the skulls and categorize them in terms of similarity. Determine which traits you will examine, and the
criteria for placing the skulls in each category.
• Form a hypothesis about common ancestry.
Analysis Questions
1) What criteria did your group use for categorizing the skulls? Make a list.
2) D
escribe the habitat you think each group of organisms (skull category) would be best adapted to living in and
explain your reasoning.
3) Respond to the following questions for each skull category; you may also draw sketches to support your written
explanations: What do you think the ancestor species of each group might have looked like? What do you think
the ancestor species’ habitat was like? List the major differences there might be in skull morphology between
the modern species and their ancestor species.
The Field Museum • Chicago Center for Systems Biology
Genes, Traits, and Individuals • Student Pages • Station 2 • Page 2
© Kornilovdream | Dreamstime.com
The Field Museum • Chicago Center for Systems Biology
Genes, Traits, and Individuals • Student Pages • Station 2 • Page 3
© Mularczyk | Dreamstime.com
The Field Museum • Chicago Center for Systems Biology
Genes, Traits, and Individuals • Student Pages • Station 2 • Page 4
© Michael Kitchin | Dreamstime.com
The Field Museum • Chicago Center for Systems Biology
Genes, Traits, and Individuals • Student Pages • Station 2 • Page 5
© Molli66 | Dreamstime.com
The Field Museum • Chicago Center for Systems Biology
Genes, Traits, and Individuals • Student Pages • Station 2 • Page 6
© Kornilovdream | Dreamstime.com
The Field Museum • Chicago Center for Systems Biology
Genes, Traits, and Individuals • Student Pages • Station 2 • Page 7
© Kornilovdream | Dreamstime.com
The Field Museum • Chicago Center for Systems Biology
Genes, Traits, and Individuals • Student Pages • Station 2 • Page 8
Station 3
DNA Sequence Evolution
Introduction
DNA is important to the study of evolution for two related reasons. First, DNA contains all of the information that is
required to make an organism, and that information is organized into units called genes. So an organism with a long
beak has genes for making a long beak that are distinct in some ways from the genes for making a short beak. This
hints at the second important quality of DNA—DNA is passed from parents to their offspring, and it changes over
evolutionary time. The reason that long-beaked parents have long-beaked offspring is because they pass their longbeak genes to the next generation through the DNA in their sperm and eggs.
Recall that in order for evolution to occur, variation among organisms must be heritable, or passed from parents to
their offspring. Therefore, in order for evolution of morphological (body shape) and physiological (body chemistry)
traits to occur, the DNA encoding those traits has to evolve as well.
When a DNA sequence changes between a parent and its offspring, a mutation is said to have occurred. Mutations
are mistakes that are made when DNA is being copied. Mutations can have three fates:
1.First, if a mutation is bad for the function of the gene, natural selection will prevent the organisms that have that
mutation from successfully reproducing and passing along the mutation to future generations. Many mutations
that are selected against in this way will never be seen by scientists, because the organisms that had them were
sick or died very quickly without leaving offspring. We won’t look at this type of mutation today.
2.Second, if a mutation is neutral for the function of the gene, it may be passed along to future generations but
will not be a special advantage. Neutral mutations arise and accumulate in DNA at an extremely slow rate.
3.Third, if a mutation is advantageous for an organism because it changes the function of the gene in a way that
helps the organism to better adapt to its environment, it will be passed along to more members of future
generations compared to a neutral mutation. When a gene accumulates a number of mutations that change
its function, we have evidence that those are helpful mutations, and that the gene’s function is adapting in the
species.
By looking at the sequence of genes, we can infer the history of their adaptive changes to the environment. In this
exercise, we are going to perform a McDonald-Kreitman Test in order to answer the question: Is the Adh gene of the
fruit fly Drosophila evolving in an adaptive manner?
The Field Museum • Chicago Center for Systems Biology
Genes, Traits, and Individuals • Student Pages • Station 3 • Page 9
Procedure
•Look at the DNA sequences of the Adh gene from two species of Drosophila—one individual of Drosophila
simulans (DsimC) and 5 individuals of Drosophila yakuba (DyakL, J, I, G, A). The sequences are divided into triplet
codons.
•Cross off all triplet codons where the sequence is the same in every individual in both DsimC and all of the Dyak
sequences. These unchanged parts of the gene cannot tell us anything about how the gene evolved.
•You should have 32 codons left where there are differences among the sequences. Next, sort these differences
into this 2x2 matrix following these instructions:
1. Differences in the FIRST POSITION of a codon change the function of the gene. Differences in the LAST
POSITION of a codon do not change the function of the gene.
2. Differences between the DsimC sequence and ALL of the Dyak sequences represent divergences between
the two species that have been selected for by natural selection. Differences among the Dyak sequences
represent new mutations that have not yet stood the test of time.
Among Dyak
Between Dsim and Dyak
Total
No change to function
Change to function
Total
• Now, add up the totals for the rows and columns of this matrix. What proportion of the total number of
differences that change the function of the gene are divergences between Drosophila simulans and Drosophila
yakuba? What proportion of the total number of differences that do not change the function of the gene are
divergences between Drosophila simulans and Drosophila yakuba? IF YOU HAVE STATISTICS, YOU CAN PERFORM
A G-TEST FOR INDEPENDENCE HERE.
Analysis Questions
1) W
hat does it mean that a greater proportion of the differences that change the function of the gene have stood
the test of time, compared to the proportion of differences that don’t change the function of the gene?
2) T he gene Adh encodes the enzyme alcohol dehydrogenase, which is necessary for organisms to extract
chemical energy from alcohol in their food. Fruit flies, as their name implies, live on rotting fruit, which produces
alcohol when fermented by bacteria or yeast. What natural selective pressures might act on the gene Adh to
favor changes in its function? What might you guess is different about the food of Drosophila simulans and
Drosophila yakuba?
The Field Museum • Chicago Center for Systems Biology
Genes, Traits, and Individuals • Student Pages • Station 3 • Page 10
110203036
DsimC ATGGCGTTTACTTTGACCAACAAGAACGTGATTTTC
DyakL ATGGCGTTTACCTTGACCAACAAGAACGTGGTTTTC
DyakJ ATGGCGTTTACCTTGACCAACAAGAACGTGGTTTTC
DyakI ATGGCGTTTACCTTGACCAACAAGAACGTGGTTTTC
DyakG ATGGCGTTTACCTTGACCAACAAGAACGTGGTT TTC
DyakA ATGGCGTTTACCTTGACCAACAAGAACGTGGTTTTC
374050607072
DsimC GTTGCCGGTCTGGGAGGCATTGGTCTGGACACCAGC
DyakL GTGGCCGGT C TGGGAGGCAT TGGT C TGGACACCAGC
DyakJ GTGGCCGGT C TGGGAGGCAT TGGT C TGGACACCAGC
DyakI GTGGCCGGT C TGGGAGGCAT TGGT C TGGACACCAGC
DyakG GTGGCCGGT C TGGGAGGCAT TGGT C TGGACACCAGC
DyakA GTGGCCGGT C TGGGAGGCAT TGGT C TGGACACCAGC
738090
100
108
DsimC AAGGAGCTGCTCAAGCGCGACCTGAAGAACCTGGTG
DyakL AAGGAGCTGGTCAAGCGGGACCTGAAGAACCTGGTG
DyakJ AAGGAGCTGGTCAAGCGGGACCTGAAGAACCTGGTG
DyakI AAGGAGCTGGTCAAGCGGGACCTGAAGAACCTGGTG
DyakG AAGGAGCTGGTCAAGCGGGACCTGAAGAACCTGGTG
DyakA AAGGAGCTGGTCAAGCGGGACCTGAAGAACCTGGTG
109
120
130
140
144
DsimC ATCCTCGACCGCAT TGAGAACCCTGCTGCCAT TGCC
DyakL ATCCTCGACCGCAT TGAGAACCCGGCTGCCATCGCC
DyakJ ATCCTCGACCGCAT TGAGAACCCGGCTGCCATCGCC
DyakI ATCCTCGACCGCAT TGAGAACCCGGCTGCCATCGCC
DyakG ATCCTCGACCGCAT TGAGAACCCGGCTGCCATCGCC
DyakA ATCCTCGACCGCAT TGAGAACCCGGCTGCCATCGCC
145
150
160
170
180
DsimC GAGCTGAAGGCAATCAATCCAAAGGTGACCGTCACC
DyakL GAGCTGAAGGCAATCAATCCAAAGGTGACCGTCACC
DyakJ GAGCTGAAGGCAATCAATCCAAAGGTGACCGTCACC
DyakI GAGCTGAAGGCAATCAATCCAAAGGTGACCGTCACC
DyakG GAGCTGAAGGCAATCAATCCAAAGGTGACCGTCACC
DyakA GAGCTGAAGGCAATCAATCCAAAGGTGACCGTCACC
181
190
200
210
216
DsimC TTCTACCCCTATGATGTGACCGTGCCCATTGCCGAG
DyakL TTCTACCCCTACGATGTGACCGTGCCCATTGCCGAG
DyakJ TTCTACCCCTATGATGTGACCGTGCCCATTGCCGAG
DyakI TTCTACCCATACGATGTGACCGTGCCCATTGCCGAG
DyakG TTCTACCCCTATGATGTGACCGTGCCCATTGCCGAG
DyakA TTCTACCCCTATGATGTGACCGTGCCCATTGCCGAG
The Field Museum • Chicago Center for Systems Biology
Genes, Traits, and Individuals • Student Pages • Station 2 • Page 11
217
220
230
240
250
252
DsimC ACCACCAAGCTGCTGAAGACCATCTTCGCCAAGCTG
DyakL ACCACCAAGCTGCTGAAGACCATCTTCGCCCAGCTG
DyakJ ACCACCAAGCTGCTGAAGACCATCTTCGCCCAGCTG
DyakI ACCACCAAGCTGCTGAAGACCATCTTCGCCCAGCTG
DyakG ACCACCAAGCTGCTGAAGACCATCTTCGCCCAGCTG
DyakA ACCACCAAGCTGCTGAAGACCATCTTCGCCCAGCTG
253
260
270
280
288
DsimC AAGACCGTCGATGTCCTGATCAACGGAGCTGGTATC
DyakL AAGACCATCGATGTCCTGATCAACGGAGCTGGCATC
DyakJ AAGACCATCGATGTCCTGATCAACGGAGCTGGCATC
DyakI AAGACCATCGATGTCCTGATCAACGGAGCTGGCATC
DyakG AAGACCATCGATGTCCTGATCAACGGAGCTGGCATC
DyakA AAGACCATCGATGTCCTGATCAACGGAGCTGGCATC
289
300
310
320
324
DsimC CTGGACGATCACCAGATCGAGCGCACCAT TGCCGTC
DyakL CTGGACGATCACCAGATCGAGCGCACCATCGCCGTC
DyakJ CTGGACGATCACCAGATCGAGCGCACCATCGCCGTC
DyakI CTGGACGATCACCAGATCGAGCGCACCATCGCCGTC
DyakG CTGGACGATCACCAGATCGAGCGCACCATCGCCGTC
DyakA CTGGACGATCACCAGATCGAGCGCACCATCGCCGTC
325
330
340
350
360
DsimC AACTACACTGGCCTGGTCAACACCACGACGGCCATT
DyakL AACTACACCGGCCTGGTGAACACCACGACGGCCATC
DyakJ AACTACACCGGCCTGGTGAACACCACGACTGCCATC
DyakI AACTACACCGGCCTGGTGAACACCACGACGGCCATC
DyakG AACTACACCGGCCTGGTGAACACCACGACTGCCATC
DyakA AACTACACCGGCCTGGTGAACACCACGACTGCCATC
361
370
380
390
396
DsimC T TGGAC T T C TGGGACAAGCGCAAGGGTGGT CCCGGT
DyakL C TGGAC T T C TGGGACAAGCGCAAGGGTGGACCCGGT
DyakJ C TGGAC T T C TGGGACAAGCGCAAGGGTGGACCCGGT
DyakI C TGGAC T T C TGGGACAAGCGCAAGGGTGGACCCGGT
DyakG C TGGAC T T C TGGGACAAGCGCAAGGGTGGACCCGGT
DyakA C TGGAC T T C TGGGACAAGCGCAAGGGTGGACCCGGT
397
400
410
420
430
432
DsimC GGTATCATCTGCAACATTGGATCCGTCACTGGATTC
DyakL GGTATCATCTGCAACATTGGATCCGTGACTGGATTC
DyakJ GGTATCATCTGCAACATTGGATCCGTGACTGGATTC
DyakI GGTATCATCTGCAACATTGGATCCGTGACTGGATTC
DyakG GGTATCATCTGCAACATTGGATCCGTGACTGGATTC
DyakA GGTATCATCTGCAACATTGGATCCGTGACTGGATTC
The Field Museum • Chicago Center for Systems Biology
Genes, Traits, and Individuals • Student Pages • Station 2 • Page 12
433
440
450
460
468
DsimC AATGCCATCTACCAGGTGCCCGTCTACTCCGGCACC
DyakL AACGCCATCTACCAGGTGCCCGTTTACTCCGGCACC
DyakJ AACGCCATCTACCAGGTGCCCGTTTACTCCGGCACC
DyakI AACGCCATCTACCAGGTGCCCGTTTACTCCGGCACC
DyakG AACGCCATCTACCAGGTGCCCGTTTACTCCGGCACC
DyakA AACGCCATCTACCAGGTGCCCGTTTACTCCGGCACC
469
480
490
500
504
DsimC AAGGCTGCCGTGGTCAACTTCACCAGCTCCCTGGCG
DyakL AAGGCTGCCGTGGTCAACTTCACCAGCTCCCTGGCG
DyakJ AAGGCTGCCGTGGTCAACTTCACCAGCTCCCTGGCG
DyakI AAGGCTGCCGTGGTCAACTTCACCAGCTCCCTGGCG
DyakG AAGGCTGCCGTGGTCAACTTCACCAGCTCCCTGGCG
DyakA AAGGCTGCCGTGGTCAACTTCACCAGCTCCCTGGCG
505
510
520
530
540
DsimC AAACTGGCCCCCATTACCGGCGTGACCGCTTACACC
DyakL AAACTGGCCCCCATCACCGGCGTGACCGCTTACACC
DyakJ AAACTGGCCCCCATCACCGGCGTGACCGCTTACACC
DyakI AAACTGGCCCCCATCACCGGCGTGACCGCTTACACC
DyakG AAACTGGCCCCCATCACCGGCGTGACCGCTTACACC
DyakA AAACTGGCCCCCATCACCGGCGTGACCGCTTACACC
541
550
560
570
576
DsimC GTGAACCCCGGCATCACCCGCACCACCCTGGTGCAC
DyakL GTGAACCCCGGCATCACCCGCACCACCCTGGTGCAC
DyakJ GTGAACCCCGGCATCACCCGCACCACCCTGGTGCAC
DyakI GTGAACCCCGGCATCACCCGCACCACCCTGGTGCAC
DyakG GTGAACCCCGGCATCACCCGCACCACCCTGGTGCAC
DyakA GTGAACCCCGGCATCACCCGCACCACCCTGGTGCAC
577
580
590
600
610612
DsimC AAGTTCAACTCCTGGCTGGATGTTGAGCCCCAGGTT
DyakL AAGTTCAACTCCTGGCTGGATGTTGAGCCCCAGGTG
DyakJ AAGTTCAACTCCTGGCTGGATGTTGAGCCCCAGGTG
DyakI AAGTTCAACTCCTGGCTGGATGTTGAGCCCCAGGTG
DyakG AAGTTCAACTCCTGGCTGGATGTTGAGCCCCAGGTG
DyakA AAGTTCAACTCCTGGCTGGATGTTGAGCCCCAGGTG
613
620
630
640
648
DsimC GCCGAGAAGCTCCTGGCTCATCCCACCCAGCCCTCG
DyakL GCCGAGAAGCTCCTGGCTCACCCCACCCAGCCCTCG
DyakJ GCCGAGAAGCTCCTGGCTCACCCCACCCAGCCCTCG
DyakI GCCGAGAAGCTCCTGGCTCACCCCACCCAGCCCTCG
DyakG GCCGAGAAGCTCCTGGCTCACCCCACCCAGCCCTCG
DyakA GCCGAGAAGCTCCTGGCTCACCCCACCCAGCCCTCG
The Field Museum • Chicago Center for Systems Biology
Genes, Traits, and Individuals • Student Pages • Station 2 • Page 13
649
660
670
680
684
DsimC T TGGCCTGCGCCGAGAACT TCGTCAAGGCTATCGAG
DyakL T TGGCCTGCGCCCAGAACT T TGTCAAGGCCATCGAG
DyakJ T TGGCCTGCGCCCAGAACT T TGTGAAGGCCATCGAG
DyakI T TGGCCTGCGCCCAGAACT T TGTGAAGGCCATCGAG
DyakG T TGGCCTGCGCCCAGAACT T TGTGAAGGCCATCGAG
DyakA T TGGCCTGCGCCCAGAACT T TGTGAAGGCCATCGAG
685
690
700
710
720
DsimC CTGAACCAGAACGGAGCCATCTGGAAACTGGACT TG
DyakL CTGAACCAGAACGGTGCCATCTGGAAACTGGACTTG
DyakJ CTGAACCAGAACGGTGCCATCTGGAAACTGGACTTG
DyakI CTGAACCAGAACGGTGCCATCTGGAAACTGGACTTG
DyakG CTGAACCAGAACGGTGCCATCTGGAAACTGGACTTG
DyakA CTGAACCAGAACGGTGCCATCTGGAAACTGGACTTG
721
730
740
750
756
DsimC GGCACCCTGGAGGCCATCCAGTGGACCAAGCACTGG
DyakL GGCACCCTGGAGGCCATCCAGTGGTCCAAGCACTGG
DyakJ GGCACCCTGGAGGCCATCCAGTGGTCCAAGCATTGG
DyakI GGCACCCTGGAGGCCATCCAGTGGTCCAAGCACTGG
DyakG GGCACCCTGGAGGCCATCCAGTGGTCCAAGCACTGG
DyakA GGCACCCTGGAGGCCATCCAGTGGTCCAAGCACTGG
757
760
771
DsimC GACTCCGGCATCTAA
DyakL GACTCCGGCATCTAA
DyakJ GACTCCGGCATCTAA
DyakI GACTCCGGCATCTAA
DyakG GACTCCGGCATCTAA
DyakA GACTCCGGCATCTAA
The Field Museum • Chicago Center for Systems Biology
Genes, Traits, and Individuals • Student Pages • Station 2 • Page 14
Station 4
Analogous and Homologous Structures
Introduction
Structural evidence supports evolution. Skeletal structures that are similar suggest common ancestry. Those
structures that are less similar suggest a more distant ancestry. Quadrupeds are animals that walk on four legs. The
back legs and feet are called hindlimbs. Humans are bipedal (walk on two legs). By observing the skeletal structure
and photos of various animal groups, one can identify what traits of the hind limbs might be adaptations of the
animal to its particular mode of locomotion. The front legs are called forelimbs/forelegs. Since humans are bipeds
their forelimbs are called arms and hands. Animals use their forelimbs for many different tasks, such as grasping,
holding, digging, climbing, and running. In evolutionary terms, form fits function.
Procedure
•Observe the various animal skeletons and/or photographs.
•Look for any similarities and differences in structure.
Analysis Questions
1) Define the word homologous.
2) Define the word analogous.
3) List three similarities between the foot of a human and the foot of a bird.
4)For each of the following animals, describe the structure of the hindlimb and/or the forelimb and the function
they serve: lion, hawk, horse, wolf, frog and mole. Example: Describe the foot of a red fox. The foot helps the
animal to run, because it has pads on the feet and to hunt because it has sharp claws for digging and holding
onto its prey. The bones are long and provide support for the animal’s body, helping it to run fast.
5) How are the wings of the bat, insect, and bird similar? How are they different?
6) Would you classify the wings of a bat, insect, and bird analogous or homologous? Explain your answer.
7) Besides the tasks listed in the introduction, for what other activities can animals use their forelimbs?
8) Compare the skeletal structure of all of the animals at this table. List five similarities between the animals.
9)For each animal, describe the main function of the forelimb and the hindlimb. What are they used for?
10) F or each forelimb, describe one feature that makes the hand well suited for its function. In other words, relate
the structure to the function of the forelimb. Do the same for the hindlimb.
11) Do fish have forelimbs? Explain why or why not.
12) What can be said about the genomes of animals that have homologous structures?
The Field Museum • Chicago Center for Systems Biology
Genes, Traits, and Individuals • Student Pages • Station 4 • Page 15
© Shirell Delaney | Dreamstime.com
The Field Museum • Chicago Center for Systems Biology
Genes, Traits, and Individuals • Student Pages • Station 4 • Page 16
© argonaut
The Field Museum • Chicago Center for Systems Biology
Genes, Traits, and Individuals • Student Pages • Station 4 • Page 17
© Mularczyk | Dreamstime.com
The Field Museum • Chicago Center for Systems Biology
Genes, Traits, and Individuals • Student Pages • Station 4 • Page 18
Station 5
Natural Selection Changes Populations Over Time
Introduction
Evolution is the process by which living things change over many generations. Evolution requires only three simple
things in order to occur. First, individuals of a species must have variation, which means they are different from one
another. Second, these differences must be heritable (inherited by offspring from their parents). Third, some of these
differences must make certain individuals more likely than others to survive and reproduce (the ability to survive well
enough to reproduce is called fitness). When individuals with greater fitness have more offspring than those with
lower fitness, natural selection has occurred.
That’s it! As long as there are heritable differences among individuals, and these differences make some individuals
more successful at survival and reproduction than others, evolution by natural selection will occur.
At this station, you will observe how differences in reproductive success cause populations to become different over time.
Procedure
• Decide what kind of organism you are going to be as a class. e.g. “We are birds.”
•Split into two equal teams. With your team, choose an adaptation you will have that will improve your fitness over
the other team in some environment. e.g. “Team A can fly longer distances to find food,” and “Team B has a stronger
beak to crack hard nuts.” Identify your teams with two different colored chips, blocks, cards, etc., ~50 per team.
• Flip a coin. Heads means the environment favors Team A. Tails favors Team B.
•After every coin toss, the winning team puts 3 chips into a box. The losing team puts only one chip into the box.
This represents the next generation.
•Empty the box and count. Write down how many individuals from your team made it into the next generation. Flip
the coin again. For each individual who made it into the next generation, put either 1 or 3 chips into the box.
• What is the proportion of colors in the box after this generation? Repeat the coin toss.
•ADDITIONAL STEP: At the teacher’s discretion, the environment can stay steady through multiple turns (favoring
one team over the other).
•ADDITIONAL STEP: At the teacher’s discretion, a natural disaster can remove half of the chips in the box at random.
•ADDITIONAL STEP: At the teacher’s discretion, the “carrying capacity of the environment”, that is the total number
of chips in the box, can be set. Once the population grows to that size, the team that wins the toss gets to replace
1/3 of the losing team’s chips with their own chips, keeping the total number the same. Does a team go extinct?
Analysis Questions
1)
2)
3)
4)
5)
How
does this proportion of colors change in every generation?
H
ow did the proportion change when the environment consistently favored one team over the other?
How did the random disaster change the proportion?
How was the game different when the “carrying capacity” of the environment was set?
How does this game help you to understand the process of evolution?
The Field Museum • Chicago Center for Systems Biology
Genes, Traits, and Individuals • Student Pages • Station 5 • Page 19