There's too much focus on the "what we know" like Kreb's cycle, which is easily examinable. The focus should actually be "how we found out", something like what the book A Brief History of Everything traces out. Things like "we used isotopes with different masses to figure out this thing about phosphorous in DNA".

In general, the "what" makes no sense without the history. Why were we searching for DNA in the mid 20th century? What did we already know? Retracing science as an investigation would be much more beneficial to kids than making them remember the conclusions. It's much more portable as a skill to understand the path of investigation than some facts about organelles that they aren't likely to use.

But the real reason I dropped biology when the choice came (and why did it come, dear IB organisation?) is that biology is not seen as the smart kid subject, when compared to physics and chemistry. Part if this is that you can grind your way through memorizing the biochemical cycles, probably easier for most than learning calculus that you need for physics. But part of it is simply reputation, and it's not reasonable.

I have a friend who is a postdoc stats guy in the biology field. There's actually a deep need for numeracy in biology, people just don't seem to know it when they're in school.