This is called irreducible complexity. If the evolution process occurred so slow, most creatures wouldn't survive. What evolved first, the animals eyes to see the prey, teeth to chew the prey, stomach to digest the prey, ect.? and when did the prey evolve? Darwin's theory was inspired before he realized how complex cells are. It is outdated and should not be taught in school.
Irreducible Complexity is nothing new to anyone here. It has been widely refuted.
The evolution of the eye. http://en.wikipedia.org/wiki/Evolution_of_the_eye