I advise my students to make sure that whatever you do, read Nature of Biology. One of the authors Marjory Martin, heads up the examination panel for Unit 3. At least she did until the end of 2008. Not sure about who is in charge of the 2009 panel?? She has headed up the panel for many years so I presume she is still there. I also give my students questions from past papers (not necessarily the whole paper) from as far back as 1995. The course has changed in 2006 but some of the questions in these papers are still relevant. Ask your teachers to show you which ones, that is their job!! The Unit 4 course in particular has not changed that much apart from the introduction of more Genetic Engineering. Make sure you do VCAA exams from at least 2000 for Unit 4.