When the guppies were moved from the pools with cichlids to the pools with killifish, they longer have to worry about being preyed upon. Previously, they were drab in color because they had to avoid detection by the cichlids. However, with the killifish, the guppies can now display more color to attract females, for they do not have to worry about attracting the attention of the killifish. This is an example of natural selection at work where the guppies change the traits display to best adapt to the environment.
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