Courtship in Guppies

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Courtship in Guppies

• Lab 3

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Courtship in Guppies

• Guppies (Poecilia reticulata) are live-bearing
  fish from South America Trinidad.
• Sexual dimorphism occurs in guppies.
• Males are colorful and have fancy tails.
• Females are larger and very plain.

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Sexual Selection

• Two complementary mechanisms that may cause
  females males to look different.
• Competition between males for access to females.
  Males will often be large and have features that
  will intimidate other males.
• If one sex (ex. female) is choosy, the other (ex.
  male) may evolve bright coloration, fancy fins or
  tail feathers or elaborate courtship rituals.

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Sexual Selection

• Since females put so much energy into
  reproduction (eggs are costly to make), they are
  likely to be choosy about which male to mate
  with.
• If females vary in quality (reproductive output),
  males may also be choosy.
• In fish, often larger females produce a lot more
  eggs than smaller females.

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Courtship Experiment

• Ask a question
• Will a male prefer a larger female over a smaller
  one?
• Restate the question as a hypothesis
• A male will prefer a larger female over a smaller
  one.

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Courtship Experiment

• A null hypothesis usually suggests that there
  will be no effect
• Males will show no preference between females.
• Now come up with a way to test your hypothesis.

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Courtship Experiment

• Independent variables do not change with relation
  to the other variables.
• Usually plotted on the x-axis in a graph of the
  results.
• Dependent variables do change they are
  dependent on the independent variables.
• Usually plotted on the y-axis in a graph.

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Courtship Experiment

• Set up your data tables to record the information
  that you will gather during your experiments.
• Use this data to create tables and/or graphs to
  present your data in the results section of your
  lab write-up.

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Lab Write-Up

• Introduction include a small amount of
  background material. State your hypothesis.
• Methods Briefly describe the methods of your
  experiment that will address your hypothesis.

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Lab Write-Up

• Results this section presents your results in
  words and figures. Include short captions for
  your figures. Do not draw any conclusions about
  what your data may mean just present the facts.
• Conclusions now draw your conclusions and
  perhaps relate your new data to what has been
  found previously.

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Lab Write-Up

• Finally, the References section should include a
  list of any references that you used.