How to cram for biology to get an 8/9?

How can I cram for the biology exam and get an 8/9?

Make sure you understand the content for each paper. Most people have paper 1 Friday, so go through videos on the information you need to know for that paper. Then find your weak spots so that you can go over this content in more detail.
After you have a rough idea of each topic, do practise papers! These are crucial to know how to answer!
Also take a look at the core practicals- some people on Quizlet have flashcards for these. If you’re doing edexcel, 15% of your exam is core practicals. Hence 15 marks on Friday will be core practicals alone- so look through those too (I.e. what you do roughly, how to improve etc)
But my biggest recommendation:

Best of luck!

if 15 marks are just practicals, can i still get a 9 without knowing them or getting 0

To be completely honest, the core practicals are very quick for bio. If you don’t learn them, you’re going to end up with about 85% (this is if you get everything correct). Hence it would be super useful to- what exam board do you do, because it might be different for you? If it’s edexcel, there is a good core practical set on Quizlet I can share- there are only a handful or two you need to roughly know for paper 1. If you learn these and content, then you’re setting yourself up for a high grade- 8/9.

im aqa but i do have some basic knowledge of the practicals, like i know what to do. i think around 64% is an 8 for aqa. thats what im aiming for. ima go over some freesciencelessons videos on the practicals rn.

64% would be close to a 9 if past grade boundaries are similar to this year's - in 2023, 132/200 required for a 9, 118/200 for an 8 (overall). That's 66/paper and 59/paper respectively. And in other years they weren't much different. (This is for aqa)

How can I cram for the biology exam and get an 8/9?

This advice might be a bit basic and overused by try out Physics and Maths tutor! They have detailed notes and practice questions on each topic, plus past papers.
Assuming you’re taking AQA Biology, I’d also recommend memorising the practicals since there’s basically always a 6 marker on one or two of them. Good luck!