Chemistry and Biology
While teaching both as a private tutor and as a TA at UC Davis I noticed that many introductory biology classes no longer have a chemistry prerequisite. My understanding is that they want to expedite/consolidate the learning process and thus offer biology earlier on, but I think this is a mistake.
When I was a student you were not permitted to take introductory biology until you completed at least two quarters of general chemistry (with at least a C-). See, a solid understanding of chemistry is very helpful when learning many fundamentals of biology - charge-charge interactions, thermodynamics, nonpolar and polar substances, enzyme kinetics, etc. You almost always get a crash course in chemistry in the first chapter of biology textbooks, but this is meant to refresh your memory, not introduce new concepts. It's too much for many students to absorb at once and makes an already difficult subject even harder.
My advice? If your school doesn't have chemistry as a prerequisite for biology, take it anyways before you start biology.
All this is probably old news to many biology teachers, but I just wanted to give my two cents on the topic.