You can certainly postpone the bio if you choose. There are no rules (at least as far as AMCAS and med schools are concerned) about how science sequences can be arranged. You should, however, check with your academic advisor to make your school has no issues with your scheduling.
RE: science seminar. Whether or not a course has an associated lab is irrelevant as to its classification as a science course. It depends on the how the seminar is listed on your transcript. Does it have Bio, Chem, Math or Physics designation?
Here is the official AMCAS course classification guide: https://www.aamc.org/students/downlo...tion_guide.pdf