My school offers a variety of upper division biology classes, some easier than others. My question is would an adcom look down on upper division biology classes such as conservation biology in comparison to other upper divs such as micro and cell.
as was said, the harder classes may be more helpful in understanding your coursework later on, but also, the adcoms don't know that those other classes are easy and who are they to say that that isn't an actual interest of yours. i took several easy upper divisions (ecology, evolution, some sort of environmental class), and i still got in. it didn't hold me back in classes in med school either. while some of us may consider choir or piano "easy" courses, music majors still get into med school. what i mean by that is not everyone has the same interests in classes throughout undergrad, and taking 'different' courses than most pre-meds won't hurt you
med schools have their requirements. as long as you reach those, i don't think the majority of school scrutinize over every other class you've taken. yes, an interviewer may ask you about why you took it, but you come up with an answer and something good that came out of it
If you can handle it you are probably better off taking micro and cell as those are much more applicable to med school. The more exposure you've had to a topic, the easier it is to absorb the gallons of material that is thrown at you in med school.
My ecology course is, so far, in the top 3 of my most grueling classes. My teacher had us doing advanced ecological studies, and our semester-long project was to write a formal grant request for an ecological experiment of our original design. We had to present a powerpoint with our experiment plan, complete with a budget. I feel that my experience with the "softer" biology courses (invertebrate zoology, marine biology, ecology...) makes me a better scientist, and therefore will someday make me a better doctor. I learned a great deal from these classes--and how many med students can say that they stood around in Tennessee, in the snow, for 3 hours studying pond vegetation? I say, if it interests you, go for it.