Been awhile since i've had to look at courses anymore but from memory they either wanted almost any science (Like Bsc @ Melbourne) or VCE chemistry.
If you have chemistry i reckon you'll be fine but doing biology will help a lot if you plan to do biology at uni, because at melbourne and monash (dont know about anywhere else) they dont have separate streams for people who *have* done biology and for people who *have not*. It would be a great help to have done VCE biology prior to this and it would be one less subject you'd have to worry less about considering the break neck speed they cover this stuff at in uni. That said, if you don't do VCE biology im sure youll still manage, just wont be as easy.
(If you want to do any life science subject via science such as pharmacology, physiology, biochem, ect at melbourne and monash the 2nd and 3rd year subjects for those course majors usually require you to have 1st year biology as a prereq. 1st year biology is just titled "Biology" it doesn't really specialise down, its very general and pretty much like VCE bio with some extra things chucked in.)