This is where you can really get screwed by focusing on some things and neglecting others. I had a plant question and no embryology, so it's the luck of the draw. Anything in Campbell's is essentially fair game if you look at the ADA outline, but you only get a 40 question sample so it could vary substantially from person to person. Good news is that the detail level is VERY shallow. You absolutely have to cover everything, but not in that much depth.