Below are the links to the exam specification. The specification is invaluable in telling you what you need to know, it doesn't however contain any detail.
Separate Scientists: https://www.aqa.org.uk/subjects/science/gcse/biology-8461
Trilogy Combined Scientists: https://www.aqa.org.uk/subjects/science/gcse/combined-science-trilogy-8464
BBC Bitesize is finally back, and now aimed specifically at new specifications. Definately worth checking out:
Separate scientists: https://www.bbc.com/bitesize/examspecs/zpgcbk7
Trilogy combined scientists: https://www.bbc.com/bitesize/examspecs/z8r997h
BBC Bitesize has also created some awesome podcasts on key content. Find them here: https://www.bbc.co.uk/bitesize/articles/zdrk7v4
https://www.youtube.com/user/AmoebaSisters - Detailed videos explaining core principles in a fun illustrated way.
https://www.youtube.com/channel/UCqbOeHaAUXw9Il7sBVG3_bw - A more informative youtube channel explaining concepts.
There is obviously a lot more revision material out than what appears on this webpage. Listed below are a couple of great resources available on AMAZON that could really boost your exam performance:
https://www.amazon.co.uk/GCSE-Biology-Revision-Question-Cards/dp/1789080525/ref=pd_sbs_14_1/260-2179590-8010442?_encoding=UTF8&pd_rd_i=1789080525&pd_rd_r=f06ed3d6-4281-11e9-9a1d-8580058e4491&pd_rd_w=MO7Gt&pd_rd_wg=wnhSq&pf_rd_p=18edf98b-139a-41ee-bb40-d725dd59d1d3&pf_rd_r=EXTGC9JQNNSZD22JEBND&psc=1&refRID=EXTGC9JQNNSZD22JEBND - CGP Separate science flashcards that go alongside your revision guide.
https://www.amazon.co.uk/New-9-1-GCSE-Combined-Science/dp/178908055X/ref=sr_1_3?ie=UTF8&qid=1552146139&sr=8-3&keywords=aqa+revision+combined+science+cards - CGP Combined Trilogy science flashcards that go alongside your revision guide.
https://www.amazon.co.uk/Biology-Combined-Science-Foundation-Workbook/dp/0008189544/ref=sr_1_17?ie=UTF8&qid=1552145872&sr=8-17&keywords=foundation+biology+aqa - Foundation support workbook.
https://www.amazon.co.uk/Biology-Grade-Booster-Workbook-Science/dp/000819436X/ref=sr_1_11?ie=UTF8&qid=1552145913&sr=8-11&keywords=grade+5+booster - Grade 5 booster support workbook.
https://www.amazon.co.uk/Biology-Grade-Booster-Workbook-Science/dp/0008322546/ref=sr_1_4?ie=UTF8&qid=1552146003&sr=8-4&keywords=grade+9+booster+biology - Grade 6-7 booster support workbook.
https://www.amazon.co.uk/Biology-Grade-Booster-Workbook-Science/dp/0008194335/ref=pd_sbs_14_1/260-2179590-8010442?_encoding=UTF8&pd_rd_i=0008194335&pd_rd_r=b97aaea2-4281-11e9-8899-45d38b264d2b&pd_rd_w=S8SQt&pd_rd_wg=fywpf&pf_rd_p=18edf98b-139a-41ee-bb40-d725dd59d1d3&pf_rd_r=ZDKPAPXJ4Y77SMQ73SPY&psc=1&refRID=ZDKPAPXJ4Y77SMQ73SPY - Grade 8-9 booster support workbook.