Biology of Australian Flora & Fauna is really interesting, requires little logical thought and is well-coordinated and quite easy (and I have Dropbox-hosted online comprehensive notes I could send you).
Genetics & the Evolution of Life is a little harder but covers some really intriguing stuff about protists no other course at UoM will really teach you (sadly, protists are super-cool and everywhere :<), and genetics is really useful as a foundation for life sciences if you choose to go on with those.
Understanding Planet Earth opens up later-level geology subjects and has no exam component, and might help if you plan to major in a field biology or chemistry-type discipline, as well as physics-y type geomatics etc. From what I hear it's fairly easy and there's also an extended field trip.
From Solar System to the Cosmos is (according to my friend) an absolute joke if you have ever taken a science class beyond Year 9 and know how to do basic algebra.
I would suggest The Geography of Famine as another "keeping options open subject" even though it's apparently quite boring, but that only runs in Semester One :/
MBB2 is pretty manageable from what I hear as well? And the exam is all MCQ!