As airsimon stated, the bio questions on the DAT are from a very wide range. I felt as though there wasnt one class in particular that helped. It seems as though each class (bio 120, 220, 340, 350, 360, 420, biochem, animal diversity, physiology, and anatomy) helped out equally. There were questions from each of those classes and if you havent taken any one of those then there will be questions you will have to guess on and move on. If you have the time, I would take all of those classes, and then take the DAT! Your bio score would be extremely high.