Is it just me or is the topic title and the opening post completely unrelated?
Science or BioMed at Melbourne - that's a very broad question, especially given that you haven't told us anything else about what you want to do.
ATAR Requirements - you can find this out in the VTAC guide
From what I hear there is no preference, however most are taken from biomed, followed by monash biomed and then science at unimelb. (I saw on a thread here a while ago). What's the major out of curiosity?
I mean, if anything you can probably get easier H1s in science where you can choose your subjects :S
This is purely because BioMed tends to be a stronger cohort than Science - hence, more of them will get into MD