Some schools do insist that you score at least a C on all of their requirements. A C- in a class like General Biology is gonna look really bad, and I honestly hope that your GPA is fairly strong and that it's the only blemish on your application.
As for an exemption from such schools, you could ask them, but with the sheer number of applicants I wouldn't hold my breath.
I think I would probably retake and get a better grade. I know at my undergrad school if you got below a C in any class for your major, you were forced to retake. Being that Bio is a prereq, you want a decent grade. I know this probably isn't what you want to hear. You could always call a few schools you are interested in and ask their opinion.
If you take upper division bio classes that rely on your Bio II knowledge and get good grades in them, its unlikely that you will be disqualified from being considered because of the C-. This is the same philosophy that applies if you AP out of intro bio classes, you just need to take upper division ones, and the general bio req will be considered to be fulfilled.
However, if you are not a bio major, or if your school will replace the C-, or recalculate your GPA with a better grade if you retake, it might be in your best interest to redo the class and get an A.
At some schools the C- might be equivalent to a C and therefore acceptable; you probably want to ask before submitting your secondary. Re-taking is always an option as well. I got a D in calc I my first semester of college and repeated the next semester to get a high B even though it was not mandatory for that particular class (all bio, chem, orgo, and physics course you needed a C or better in each course, plus a BCPM average of 2.0+). I think I wouldn't have gotten as many interviews if I had not made the effort to retake.. just a thought, good luck!
I had three Cs my first semester of college and ended up getting into med school during the first "round," as a non-science major in a more competetive year than current. So no, you're not disqualified. Rather than re-taking the course, take more advanced courses and do better. Make sure you calculate your science GPA and see how it's hurting, especially if you are a non-science major (less sciences classes, a C "hurts you more" in your average).
At my school you are not allowed to have below a C in your major, I'm not sure if that's ur major or not. But I do know that what's in intro bio is like the first few cahpters in each upper level class and that u are going to need to know this information. If you don't feel u have a grasp on the material then take it over and get a good grade. If the C was due to other reasons, then move on and do well in the upper level science courses.