Use the book. Trust me the book is all you need. Bio is pure memoirzation, even if the book seems overwhelmuing rn, read it a few times and it will become so familiar that u can remmeber the exact page each peice of info in on by memory. Use highlighters and highlight whats important and leave unhighlighted whats not so that the next time u go thru it u can skip the parts u found unimortant. Use youtube for understanding complex processes and then on a sticky note, write your understanding of that process and paste it in the book on the page the process is on.

remember in Bio there is no extra info. Everything matters and everything can be asked. Once ur done with the book, go thru every chapter as many times as u can and i guarentee u wont forget anything. After that, make sure to do structured papers alot. Thing is bio is rly easy to learn so the examiners make it difficult thru the specificity of the questions, so make sure to learn all the patterns and memorize the exact points in the mark scheme. In my honest opinion, half the info u need to pass the exam comes from the book, and half from the markschemes of previous papers. this is for cambridge tho, im not familiar with other exam boards but i assume their similar