Technically it doesn't have to be there. I had one uni. prof. who murdered anyone who didn't put a comma before and and, but I also had two in my senior year who thought it was better to not to have one. They said the flow was disturbed. Since it could go either way, I felt no need in changing it. It personally makes no difference to me.
But I don't know, I didn't major in English. Perhaps the modern proper way is with the comma. I would love to know, so I could have gotten a perfect score on my term paper instead of 1 point off.