SAT or ACT?

<p>I'm in the class of 2006 and right now i'm really starting to get ancy about all these college entrance exams. I want to get started on some of them. so....</p>

<p>Which one should I take first, ACT or SAT? Which one is harder? Is the ACT changing like the SAT is? Does the ACT have an essay? </p>

<p>also, I'm currently in AP biology and I want to take the SAT II in bio as well. When is the best time for me to take it? I've looked at a few practice tests and they seem SO easy compared to the stuff I'm doing in AP bio so far, so would it be OK for me to take it now?</p>