Hey lownyt,
What's your reasoning for studying "whenever you can?" Do you not have access to your course textbook or material? Once you get that you can study whenever, as long as you have them on you.
If you are searching for additional online bio courses to study for the course you are taking; I would suggest otherwise. For undergrad, your best efforts should be placed on learning your course material the best because that is what the exams will test, unlike medical school exams. You should only study additional online biology resources if 1) your class isn't taught well and you aren't learning or 2) you look up additional information for specific difficult concepts.
Good additional bio resources are Youtube and Khan academy. If this bio class turns out to be very difficult, you can try these articles: Studying Efficiently and Effectively:
The Repetition Method or
How Much Do I Need to Study to Earn Fantastic Grades (In-depth Analysis)
