Curriculum & Content: What Order Do You Teach the Units?

First let's make it clear: There is no wrong order to teach biology. There are many curriculum schemes and each is justifiable by the teacher using it.

Usually when AP Biology teachers first start out teaching the course they follow the order of the chapters in the textbook they are using -- you seem to have enough to deal with just keeping your head above water on the content and the labs, who can possibly handle mixing up the units! And all the textbooks seem to organize the course the same way -- by domains of scale: Biomolecules, Cells, Organisms, Populations, Communities, Ecosystems, Biosphere. But many of us have broken away from this organization scheme in a variety of ways for a whole range of reasons. Let's hear from teachers about how they teach their course and why they use their unique organization scheme...