As a bio taker I feel your pain.
I think you gotta break down the syllabus into its parts and take it from there. And just writing notes will NOT help at all.
Instead, I would try this method where you revise a concept (e.g. cell organelles), then create a mind map or table writing everything about that topic that you know without checking notes. Then write down anything you missed in red.
You should really try to think about how a specific topic can be asked in a question (and how it relates to other topics), rather than just knowing about individual topics.
For example, a question I had in my bio yearly a few days ago was: Explain how Darwin's Theory of evolution supports the theory that eukaryotic cells emerged from prokaryotic cells? (5 marks)
This question relates mod 1 (what is different between pro and eukaryotic cells) and mod 3 (how traits of eukaryotic cells might be advantageous, causing divergent evolution).
For content heavy stuff like circulatory system and respiratory system in mammals/fish/insects I try to imagine BEING that animal and how I would carry out those processes (i knwo it sounds crazy). For example, for fish respiratory system, I LITERALLY imagine taking in a gulp of water, closing my operculem to prevent losing water, and the water travelling in countercurrent with bloodstream. Same with insects, (I think of Mantis from Kung Fu Panda for some reason) I imagine breathing through my skin (spiracles), and the branching of tracheoles.
You can apply this for other stuff like digestive system (imagine being an apple traveling down your body's digestive tract, how are you broken down along the way?)
Anyways, this is the fate of a bio taker, good luck!