Only if your intention is to go to graduate school...It has been my experience that 80% of "graduate" courses are undergrad courses with a graduate project attached to them. The graduate project is generally a lengthy paper, presentation or some other BS that isnt really worth your time unless your career is research associated.
As for the other 20% of graduate level courses, many are research based, and unless you have a research background, wont do you any good and would probably be more difficult than its worth.
If your going to take any science classes, take upper division undergrad courses. Atleast they will be useful towards your sGPA (not saying yours needs to be improved or anything) for AMCAS..but graduate level courses wont do anything for you unless your working towards a graduate degree, though they are added into your undergrad GPA for AACOMAS...but still not worth the extra work.