The Undergraduate Calendar--you should have it. If you have the pre-reqs for the bio courses listed, then you should be able to talk to the Associate Dean of Science about taking it. If you don't have the undergrad calendar, the pre-reqs are also listed here:
http://registrar.mcmaster.ca /calen...nt/pg1982.html
From what you've said, here are the second year bio courses that you would be able to take:
2A03: Integrative Physiology of Animals
Pre-reqs: Bio 1A03 and M03, (which you have) and credit or registration in Physics 1B03 or 1SCI 1A24. There are currently no seats open for 1B03 in Term 2, so this option would only be open to you if you're already registered for it this term or next term.
2F03: Fundamental and Applied Ecology
Pre-reqs: Bio 1M03 (which you have0 or ISCI 1A24
You couldn't take any of the others during Term 2 unless you're currently taking the pre-req Chem 1AA3, which would only be possible if you were in International Baccalaureate during high school who took higher level chem and got a high enough mark, and thus got a credit for Chem 1A03.