Bio 100 Plus Hour Assignment
Name
Instructor
Lesson 3: Evolution and Selection
Lab Section
Introduction
How does evolution occur? Can we observe evolution occurring in natural populations? Charles
Darwin theorized that the primary mechanism for evolution is the process of natural selection, by
which certain individuals, having heritable traits that make then well-suited to their environment,
will be more successful at survival and reproduction than other individuals. These successful
individuals will then pass on the traits that made them successful to their offspring in the next
generation. Over time, the population will be largely made up of descendants of these successful
individuals, and the beneficial traits will be common.
Darwin himself never observed the process of natural selection in action. In fact, he imagined
that natural selection was so slow that we could not observe it over the course of our lifetimes.
This notion changed in the 1970’s when researchers Peter and Rosemary Grant began studying
populations of finches on the Galàpagos Islands. Through more than thirty years of study, the
Grants and other researchers measured changes in the average beak shape and size of finch
populations. These changes occurred in response to environmental variation from year to year,
with dramatically wet or dry years leading to the most obvious periods of selection. The Grants’
finch study has been joined by several other field studies to demonstrate how variation in local
environments can lead to changes in the population gene pool (evolution) through the process of
natural selection.
In this exercise, you will conduct simulated field studies on populations of small tropical fish
(guppies) to demonstrate natural selection in the wild. You will also explore how certain traits
that may be good for survival may not be beneficial when it comes to sexual reproduction. You
will consider how the forces of natural selection and sexual selection can interact to influence
evolution within populations.
Procedure:
1. If you are in the computer classroom, login to a CAL lab computer using ZULU/SIRS
2. Click on the Biology 100 Project (P) Course icon or go to the website:
http://www.biosbcc.net/bio100pcourse/index.htm
3. Choose the Evolution and Selection lesson.
4. Click the button labeled Begin Lesson to start the lesson. Begin Lesson will take you to:
http://www.pbs.org/wgbh/evolution/educators/lessons/lesson4/index.html
5. You should now be looking at a web page entitled “Online Lessons for Students:
Learning Evolution. Lesson 4: How Does Evolution Work”? This site is part of an
online series on evolution developed by the Public Broadcasting System (PBS).
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Bio 100 Plus Hour Assignment
Lesson 3: Evolution and Selection
Questions #
Using either the links provided on the right-hand column labeled “Scientific Terms”,
your textbook, or class notes, define the following terms:
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Evolution:
•
Population:
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Natural Selection:
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Sexual Selection:
6. Click on Activity 2: Flashy Fish.
This activity is based on the research of John Endler, Professor of Ecology, Evolution, and
Marine Biology at the University of California at Santa Barbara (UCSB). For years, Endler has
studied several populations of guppies in the mountain streams of Trinidad.
7. Read the introductory paragraph under Activity 2: Flashy Fish.
As you go through this activity, follow the procedures listed on these assignment
pages, rather than those listed on the website. This procedure is adapted from that
provided online.
8. Click on Sex and the Single Guppy (Flash) under the picture icon in the Procedures
section. Note: You will need Adobe Shockwave Player to successfully run this
simulation. If you are working the CAL lab, all computers should be equipped with
Shockwave. If you are working at your home computer, you can download Shockwave
from http://www.adobe.com/products/shockwaveplayer/.
9. Read the text and click on “check out the guppy gallery” at the bottom to see what male
guppies look like (note the variation in color).
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Bio 100 Plus Hour Assignment
Lesson 3: Evolution and Selection
10. Click on “Predators” and “Habitats”, in the lower right corner, to see the guppies’
predators and the habitats in which guppies live.
Question #
• Give the common and scientific names of three guppy predators.
11. Click on “Back to Simulation.”
12. Click on “I’m ready to find out.”
13. Read the text, and click on the pools to investigate the guppy stream more closely.
To return to the text page, simply click the X in the orange framed pool box.
Question #
• As you have seen, male guppies exhibit a wide variety of color and spot patterns. What
do you think causes this color variation? Click on “What causes guppy variation?” for
a list of potential hypotheses. You are to either come up with your own hypothesis, or
select one from those listed.
Your hypothesis:
14. After you have reviewed chosen your hypothesis, you will proceed with the simulation
by setting up an experiment to determine some influences on guppy coloration. Click on
“To start, choose how you want to set up your simulation pool.”
15. Read this page, and select your guppy types and predator species/numbers. (Note:
Rivulus is the least effective guppy predator). Record your initial settings here:
Guppy color types: __________________________________
Predator species and numbers: _________________________
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Bio 100 Plus Hour Assignment
Lesson 3: Evolution and Selection
16. Run your initial experiment/simulation for at least seven generations and record your
results here:
Number of guppies:
Number of generations:
Number of weeks:
Male color types:
Brightest male guppies: _____%
Bright male guppies:
_____%
Drab male guppies:
_____%
Drabbest male guppies: _____%
17. Click on “Results” to see an analysis of your results.
Questions #
• Do these results support your hypothesis? Explain why or why not.
•
If your initial hypothesis was not supported by your data, you may want to choose
another hypothesis to answer the question, “What causes color variation?”. If so, enter
your new hypothesis here:
Your new hypothesis (if applicable):
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Bio 100 Plus Hour Assignment
Lesson 3: Evolution and Selection
18. Click on “Run Another Simulation,” and select new settings. Do this even if your
hypothesis was supported by the results of your first run. Enter your new settings here:
Guppy color types: __________________________________
Predator species and numbers: __________________________
19. Run your new experiment/simulation for at least seven generations and record your
results here:
Number of guppies:
Number of generations:
Number of weeks:
Male color types:
Brightest male guppies: _____%
Bright male guppies:
_____%
Drab male guppies:
_____%
Drabbest male guppies: _____%
20. Click on “Results” to see an analysis of your results.
Question #
• Do these results support your hypothesis? Explain why or why not.
21. After you have completed your second simulation and reviewed the results, Click on
“Read Summary.”
22. Read this summary carefully, and if you desire, run more simulations putting to test
the knowledge you have just learned.
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Bio 100 Plus Hour Assignment
Lesson 3: Evolution and Selection
23. Use the information gained in the Summary to answer the discussion questions below:
# Discussion Questions:
•
Based on the results of your experiments/simulations, would you say that guppy
coloration is heritable (that is, is it genetically determined)? Why or why not?
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What role does color play in guppy survival?
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What role does color play in guppy reproduction?
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How are the forces of predation and sexual selection at odds in these guppy populations?
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Male guppies are often brightly colored, while females are always drab. How would you
explain this difference between males and females within this species?
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