Medical Education US

I'm a junior in college and I've just decided to major in biology. During my first 2 yrs of school I only took general requirements and I had no idea I was going to want to go to medical school and did not do as well as I should have b/c I didn't take school seriously. Will this effect me getting into medical school if Im doing very well now?

I'm assuming the overall application process is not dramatically different from when I applied over 10 years ago (although it is probably more automated and computerized), and on the applications, I was required to put my GPA for both science and non-science courses separated out. I also had to include a current transcript. Obviously, your lower grades your first two years will reflect negatively on your overall GPA. If you are now taking the science classes and you are doing well, that will reflect positively on you. If, however, your science GPA is low, that will make things more difficult.