I know people who teach science subjects in which they do not have a degree, but I can imagine that a few districts might have a rule about it. Bio is so close to Chem, though, and with the shortage of science teachers as it is, it would have to be a fairly bureaucratic district to DQ you!
Here's a suggestion from someone twenty years out of college this fall: why not stay the extra semester, take those two classes, and otherwise have the time of your life? Experiment. Take a photography class, or film studies. Sign up for coed intramural water polo. Date several sorority women. Whatever you personally have always dreamt about, do it. Because ...
... you will never have your college experience back again. Never. The working world can be harsh, and it is relatively much more structured and much more lonely. So make the most of your youth while you still can. You have the rest of your life to make a living. (And it's not as if you'd be graduating into a great economy.)
Good luck.