Evolution and Design

We know design exists. What about in the biology class or in a popular magazine in a discussion about evolution? Why is design ruled out? Where does the evidence point?

Richard Dawkins in his book The Blind Watchmaker wrote, "Biology is the study of complicated things that give the appearance of having been designed for a purpose." If it looks like a duck, walks like a duck, quacks like a duck but to Dawkins, it can't possibly be a designed duck. The duck only looks designed for a purpose.