I actually wrote this in a college science class after hearing the history of the Peppered Moth. I failed the class and had to retake it.

http://en.wikipedia.org/wiki/Peppered_moth_evolution

The moth whose color does not match
Stands out from the rest of the batch
He is easily seen from the sky
By the bird’s watchful eye
The bird dives through the air
And snatches the only moth that’s there
But what he does not see
Is the moth that matches the tree
And so the moth can live in the dark
Until smog changes the color of the bark