Evolution is a theory, the facts say that species suddenly appeared. Ok some change in a survival of the fittest sort of way but they remain the same. Look at dogs, thier "evolution" has been manipulated by breeding, but they are still dogs. None grew wings and decided to fly away.
For e.g if your a zebra with black skin and white stripes but the lions only eat the ones with white skin and black stipes then the ones with black skin and white stripes will become more.