Biology A.S Exam - Help needed!!

Hey, I missed out on doing Biology A.S (Edexcel) this June as I had mumps and have to do it in January. My teacher is making me doing Units 1+2 though this week as a "practise" but basically she will do my predicted grade from it. I really need to do well in it - even though just starting proper revision! Was just wondering if anyone could help me out, and tell me key things that I need to learn or could miss out! I know it was a long time ago, but any details would be very much appreciated!