Is it a bad idea to choose an HL bio optional topic not being taught?

[introspectivebeat]

At my school, the option of further Human Physiology (D) is traditionally taught in HL Bio. However, I would much prefer to study option C, Ecology and Conservation (it better pertains to what I think I want to pursue in the future). My teacher said that would leave me to teach myself as nobody else wants to study that option as well. Is choosing a different topic a bad decision in this case? I don't want to endanger my exam grade, but I also know that option c is much more interesting to me and would probably be more enjoyable. Thanks in advance