How does the teaching of biology differ from teaching physics?
See Eric Lander's introductory biology OCW course lecture videos for a refreshing take on biology from someone who was trained as a mathematician. The way Prof. Lander (and likely many others) teaches biology is similar to the 'hard sciences' (chemistry and physics), but the history of the science takes a larger role than it usually does in (say traditional introductory) physics and math courses. 

Maybe a reason for this is that the ways that important biological processes take place are way too complicated for us to easily derive them from Newton's laws and some calculus, and so to bring people to speed in basic cell biology, one really needs to rely on a large amount of collected observations on non-intuitive, less widely observed phenomena than one does in classical physics to begin doing meaningful studies. One way to do this, is to just say such-and-such is the way things happen, now memorize it. Another approach however, is to explain how the existing models came to be. The second takes (much) more work.

At the most basic level, in either case one tests whether the conclusions/predictions that come from the models are consistent with what is observed, so the distinguishing of intro biology and intro physics on this point seems artificial. A real fundamental difference between the two again is that the type of things which are discussed in the intro biology course are much more complicated than those covered in a basic physics course, and so one must rely on more 'hand-waving' or historical references at certain points. To quote the famous mathematician von Neumann, 'If people do not believe that mathematics is simple, it is only because they do not realize how complicated life is.'