I think bio only gets scaled up a bit when they calculate your uai (Im pretty sure it doesnt get scaled down), but its not like if u do 4u maths or something like that where it scales heaps. I got 85 without having to be a bio nerd
Its not that hard to go well in bio, its mainly just memorise stuff and be able to answer questions the way the BOS wants u to. Which means pay attention to the words they use in the question, like evaluate, analyse, assess, etc. If you know the material well you'll be fine