Unit 2 is messed, it's all over the place. Genetics is fairly easy, just have to memorise the mitosis/meiosis process. There's always something about down syndrome in the exam - something related to chromosomal disorders.
The adaptation and evolution thing is quite hard. I didn't really get around to learning that stuff...
I'm pretty sure there'll be a question on dating, remember! potassium-argon, and stratigraphy.