Guppies are small fish that live in streams in Trinidad and other areas in the Caribbean and some parts of South America. Within their native range, guppies are subject to predation by some types of...

Guppies are small fish that live in streams in Trinidad and other areas in the Caribbean and some parts of South America. Within their native range, guppies are subject to predation by some types of larger, predatory fish. Guppy females prefer to mate with brightly colored males over less brightly colored, inconspicuous males. In the wild, male coloration varies strikingly between different streams: populations in streams with high predator densities tend to have drab, inconspicuous males with very little coloring, whereas streams with few or no predatory fish tend to have very brightly colored males (for an example of the difference between these males see the picture below).

Explain how, in an evolutionary context, this particular example neatly illustrates the following concepts:

a) Organisms cannot achieve perfection (i.e. organisms can never be perfect).

b) Fitness depends on the environment.