Biodiversity ain't easy, folks. If you want to do well, you really have go through each of the lectures, learn the concepts, think through the implications of Melnick's concepts. While this class doesn't have homework, you do have to keep up with the lectures, which Melnick (thankfully) provides on Courseworks. The midterm was difficult in terms of time, but the final was perfectly fair: if you didn't study for either of these tests, however, you probably failed, so definitely study.
Hara Woltz was a fabulous TA for this course: she's always willing to meet and answer your e-mails about questions. If she's teaching it again, I recommend signing up for her section.
Melnick's lectures are oftentimes filled with incomprehensible graphs and a miasma of data: don't worry about the specifics too much: just go for MAIN IDEA. Keep asking yourselves, "What is the main idea of this graph? What is this picture trying to tell me about genetic/demographic variation, etc.?"
The course, all in all, was interesting, but it's not an automatic A by any means.