Taking ten extra bio classes may or may not help you answer those 1-2 "weird/random/out-there" questions on the DAT bio section, and I guess it's up to the individual to decide.
As for your question, I can imagine biochem helping if the class you are taking focuses on glycolysis, citric acid cycle, electron transport chain, etc... As bio majors we've all heard of those topics and know what they kind of do.. but it's amazing how much more you can learn and actually remember stuff by taking a actual biochem class. I wish I took biochem before my DAT, because it would be free points for me if the DAT asked questions on those topics.
Ecology could also help for BIO since the topic does get tested on the DAT. However, reading the Cliffs BIO may suffice.
One class that helped me for BIO was "Anatomy and physiology I and II", even though there's only a handful of questions on that topic on the DAT.