I'm not so sure I'm in a position to be giving class-studying advice, but I did well in my science courses (I'm a postbacc and probably took much fewer than you though). My friend (also a postbacc) did well, but she spent significantly more time on studying than I did. I tried to see what we were doing differently and what could be changed. Here's a few things that might help:
1. She took notes when reading and highlighted her text. That's great, but she took A LOT of notes and highlighted almost everything. That does not help. At that point, it's just copying. The information isn't processed. Notes/outlines should be succinct; take an entire page of information and put it in a few sentences. Better yet, diagram what you read and just write captions. Resist the urge to write all the details out. To draw/summarize, you need to understand the material. The outcome will be notes that you can study from later on for the final. You will fill in the details later when you're studying. Most exams test concepts more than they test the details.
2. Read the text before lecture. Professors say this all the time, but few people actually do it. It's actually very, very helpful. You don't have to understand everything. In lecture, any confusion should be clarified. If it's not, then you can ask questions. Your lecture notes will be of higher quality because you understand what you're taking down. If the professor focuses on some items and not others in the text, there's a good chance those items will be on the exam. If you read the text afterwards (or not at all), your lecture notes are all over the place because you had no clue what the professor was referring to and you'll forget what the professor had stressed.
3. In the text, particularly Biology text, the diagrams are as important as the reading material. Sometimes, it's more important. The diagrams and captions naturally summarize what was mentioned in the textbook. Spend extra time understanding the diagrams now and you'll be better off when you study for the exam. Try to redraw the diagram on your own (not copying).
4. Try to teach it to a friend/classmate. After reviewing your own work, explain it to a friend in the same class when you study together. Inevitably, you'll find holes in your understanding and you'll fill it in from text or from the professor. You'll gain confidence that you understand the material when you can answer a fellow classmate's questions. Your friend can teach the next lecture to you and you can try to poke holes in his/her understanding.
5. Try not to get frustrated and take breaks. After 3 hours of studying, take a 1 hour break. Watch TV. Exercise. Video games. Just make sure you go back to studying after that break is over.
I honestly think this helped me. It's hard to change study habits, but the pay-off is that you have a lot more time to relax.
