Let's be clear on something: this is NOT required. But, some of you have asked for things you can do to maintain or improve skills over the summer, or to better prepare for the course. So, here are some optional practice assignments.
1: READ!!! I'll try not to rant, but reading really is the most beneficial thing you can do to prepare for an AP science course. In AP Biology, you will have to read and analyze several scientific passages. This is part of the AP exam as well. The better you are at picturing what you're reading, analyzing a text, and thinking and writing about it, the better you'll do. So read! Books, manga, essays, whatever. Just read.
2: Review graphs. You will see a lot of graphs and diagrams in AP biology. The exam includes at least one question where you have to create a graph. The better you are at analyzing and creating graphs, the better you'll do. Here's a link to a review packet to help you practice.
3: Review chemistry. Some people describe all of biology as applied chemistry. That's an oversimplification, but an adequate understanding of biology necessitates a foundation in chemistry, and we're going beyond an adequate understanding of biology. Go here for some practice on chemistry and an introduction to the biochemistry we'll use.
READ!!! Physics is full of descriptions of scenarios that you need to picture accurately to analyze correctly. So read my small rant in the AP Biology section above and then read the quote above. Finally, go read a book. Or manga. Just read.
Know how to manipulate equations. You need to be able to isolate variables. Sounds easy, but make sure that you can do it when there are exponents, radicands, fractions, and more in the equation. Go here for practice.
Be familiar with graphs and how to find slope. There's a lot of practice here. You need to know how to find the slope of a line from a graph or from a data table.