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Expedition Evolution
Activity 1. Identifying Adaptations
Following are some pictures of organisms that Dr. Mike has worked with or seen in his travels around
the world.
Look closely at the picture of each species and think about the kind of environment it lives in,
what it might eat, what might eat it, and how it reproduces. Brainstorm ideas with your table
group. Then, fill out the tables with details about each adaptation.
Species: Sally lightfoot crab (Grapsus grapsus)
Adaptation
How This Adaptation
Helps Survival Or
Reproduction
Adaptation
How This Adaptation
Helps Survival Or
Reproduction
Species: Galapagos hawk (Buteo galapagoensis)
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Species: Lava cactus (Brachycereus nesioticus)
Adaptation
How This Adaptation
Helps Survival Or
Reproduction
Adaptation
How This Adaptation
Helps Survival Or
Reproduction
Adaptation
How This Adaptation
Helps Survival Or
Reproduction
Species: Bottlenose dolphin (Tursiops truncates)
Species: American elk (Cervus elaphus)
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Activity 2. Modeling Natural Selection
Predators are important agents of natural selection. Why? Prey that are killed by predators before they have
the chance to reproduce don’t leave any offspring. Individuals that can escape more easily are more likely to
reproduce and leave more offspring. Over time, the traits of individuals that survive and reproduce will
become more common in the population.
Let’s think about traits some prey species may have to defend themselves from predators. Use
the Internet or library resources to investigate three examples of “animal predator defenses”
and two examples of “plant defenses.”
1. For each of the three animals you researched, list their defenses and how they help protect the animal
from predators.
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2. Describe two examples of defenses that help prevent plants from being eaten by herbivores.
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Activity 3. Developing Hypotheses
Use what you have learned about evolution, predators, and mosquitofish to predict how populations of
mosquitofish might differ between blue holes with predators and those without predators. There are a few
things you need to know about mosquitofish before you get started.

Mosquitofish find food in the shallows and in open water.

Having good endurance helps mosquitofish move around and get more food.

Eating more food and growing bigger increases mosquitofish reproduction.

A mosquitofish can’t be both a good sprinter and good endurance swimmer.

Mosquitofish that are good sprinters are more successful at avoiding predators.
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Table 1. Traits of Mosquitofish Living in Blue Holes With and Without Predators.
Trait
Time spent in open
water
No predators
With predators
If different, why?
Sprint speed
Endurance
Reproductive age
1.
Now you have made predictions about how mosquitofish should respond evolutionarily to predators.
How would you test your hypotheses?
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Activity 4. Analyzing Data
Let’s test your hypotheses! We’ll start with the behavior of mosquitofish.
Calculate the average proportion of fish that are found in open habitats and shallow habitats
and record them in each table below.
Table 2. Proportion of Mosquitofish in Shallow and Open Water Habitats With Predators.
Proportion in open
water (%)
1
Proportion in
shallow water (%)
99
Blue hole
Deep Blue
Predators present?
Yes
Gracie’s
Yes
0
100
Sooner’s
Yes
2
98
Cousteau’s
Yes
0
100
Billy’s Leap
Yes
2
98
Average
--
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Table 3. Proportion of Mosquitofish in Shallow and Open Water Habitats Without Predators.
Proportion in open
water (%)
29
Proportion in
shallow water (%)
71
No
20
80
Pagreeps
No
38
62
Hansen’s
No
35
65
Little Blue
No
28
72
Average
--
Blue hole
Wolfpack
Predators present?
No
Rainbow
1. Make a double bar graph of the average proportion of mosquitofish in open water and shallow water
habitats in blues holes with and without predators.
2. Was your hypothesis from activity 3 supported? Why or why not?
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It is really hard to measure the swimming speeds of mosquitofish, but we can look at the shape of their
bodies. Fish that accelerate well—the sprinters that can escape predators more easily—have bigger caudal
peduncles than those fish that are not good accelerators (see Figure 1). Fish that have better endurance have
smaller caudal peduncles.
Figure 1. This is an X-ray image of two mosquitofish. The caudal peduncle is circled in each fish. The fish on
top is from a blue hole with many predators. The bottom fish is from a blue hole with few predators.
Use the information and images above to answer the following question.
3. In terms of caudal peduncle areas, state your predictions about how fish should differ in their sprint
speeds and endurance in blue holes with and without predators.
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Fill out the averages in the table below.
Table 4. Caudal Peduncle Areas (mm2) of Mosquitofish in Various Blue Holes.
Rainbow
Fish number
1
Wolfpack
No predators
Cousteau’s
Billy’s Leap
39.8
40.9
Predators present
44.9
46.0
2
35.5
40.8
46.1
45.8
3
36.4
39.4
45.7
46.1
4
36.4
40.2
49.2
44.6
5
40.1
39.5
47.4
46.4
6
39.8
49.0
47.4
47.9
7
39.1
41.5
43.6
48.9
8
40.9
38.1
47.0
44.1
9
39.3
39.9
46.6
47.5
10
38.7
38.8
44.5
44.4
Average
4. Make a bar graph of the caudal peduncle areas of mosquitofish in the four blue holes. Be sure the graph
groups together the blue holes with predators and the blue holes without predators.
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5. Suppose that a bird flew to Rainbow blue hole with eggs of sleeper gobies attached to its feet. After many
years, a large population of these predatory fish is established in Rainbow blue hole. You explore the blue
hole after many generations of mosquitofish have lived with these predators. How do you think these
mosquitofish would differ from the ones that are there today? Why?
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Humans are changing ecosystems all over the world. In some places, predators are being driven to near
extinction. For example, large sharks are disappearing from many oceans. In other places, new predators are
being introduced. For example, pythons from Asia are now slithering around the Florida Everglades. Humans
are also agents of evolutionary change. Human fishing and hunting can cause natural selection just as
predators do.
6.
Based on what you have learned, what do you think would happen to the reproduction age and total body
sizes of fish species that are heavily fished by people? Why?
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