How much is enough?

I have an ecology test tomorrow. I am kind of stressed out because I got a 71 on the first test and this will be our last test until the final. There is so much to know for this test that I feel like no matter how much I study I won't know enough. I studied for it almost all weekend and I still feel unprepared. I'm considering staying up late. I'm not sure how much or if that will help. I've never pulled an all-nighter and i'm not sure if this case would warrant and all-nighter. I guess I'll just keep on studying and go to bed when I can't concentrate anymore. Ah, the life of a college student!