Sex and the Single Guppy
The purpose of this activity is to analyze how guppy populations change over time. The
simulation activity allows you to start with a pool of guppies and your choice of predators; you
will see what happens to your guppy population and how the introduction of predators can
affect the guppy's appearance.
I​NTRO
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Click on the link to the Guppy Gallery. Look over the examples of the guppies shown
there. What gender are they? ​[females and males ]
After viewing the guppy gallery, view the predator gallery by clicking on “See common guppy predators” at the
bottom. What are the common names of the first three? ​[Pike cichlid ]​, [​ Blue acara ]​, and ​[ Rivulus]
Read the Introduction page and study the three pools at the bottom. Which pool has the most brightly colored
guppies?​ [pool 1 ]
H​YPOTHESES
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Predators are causing guppy populations to become more ​[ drab ]​ by preying on the most brightly colored
individuals and ​[eliminating ]​ them from the gene pool.
Guppy populations are ​[ evolving ]​ to more closely match – or stand out from – their ​[environment ]​.
Female guppies are ​[ choosing ]​ to mate with the most ​[ bright ]​ colored males, giving those males a higher ​[
probality ]​ of passing their genes on to the next ​[ generation ]​.
S​IMULATION​ 1
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How many guppies did you put in the pool? ​[100 ]
What color types were they? ​[mostly drab ]
What kind of predators did you add?​ [only the rivulus ]​ How many of those? ​[ 30 ]
A​NALYSIS​ 1
Use the information in the Analysis 1 page to complete this table.
% of Brightest Guppies % of Bright Guppies % of Drab Guppies % of Drabbest Guppies
Simulation 1
4 generations
42
7
18
34
12 generations
95
1
3
2
S​IMULATION​ 2
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How many guppies did you put in the pool? ​[100 ]
What color types were they? ​[ even mix ]
What kind of predators did you add?​ [ 3 ]​ How many of each? ​[30 ]
A​NALYSIS​ 2
Simulation 2
% of Brightest Guppies % of Bright Guppies % of Drab Guppies % of Drabbest Guppies
4 generations
15
9
26
50
7 generations
0
0
4
96
C​ONCLUSION
The answers to these questions are not “right there” on the conclusion page, but you should be able to put the information that is there
together with what you have learned already about sexual selection so you can answer these questions with thoughtful,
thorough responses. Please don’t believe that you will get full points for answers that are a few words… see the verbiage –
“describe… explain… what would happen…” I truly expect your five answers will take most of this page.
1. Describe how predators influence guppy coloration. ​[if the guppies are brighter they mostly to get eaten first by the
predators thats most of it is dark ]
2. What does it mean that “male guppies live in a crossfire between their enemies and their would-be mates”? ​[The
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"male guppies live in a crossfire between their enemies and their would be mates” means that they are torn
between passing on the gene that attracts females while also putting a spotlight on themselves for predators, and
not being able to attract females, but then again, also having the advantage of not being spotted so easily by
predators ]
Explain the two reasons guppies in different areas of the stream have different colorations.​ [This happens
because the drab guppies attract less predators and are easier to camouflage themselves in its surroundings.
When there are less predators, the number of bright colored males are more plentiful because the males' main
concern is to attract a female. ]
What would happen within a few generations to mostly drab guppies that were placed in a stream with very few
predators? ​[ The drab guppies would die out because they do not have the natural ability to attract female
guppies. Their drab coloring is only useful when trying to hide from predators. ]
What would happen within a few generations to brightly colored guppies that were placed in a stream with many
predators? ​[The brightly colored guppies would die out because they would't be able to pass on their gene, due to
natural selection. They are unable to conceal themselves in the water due to their vivid hues and patterns. ]