the revision guide i'm using for science is the CGP one -mainly cus it isn't completely boring!
In B2 theres 4 main topics: Inside living cells (mainly respiration and making proteins), Divide and develop (cell division, cloning and plant stuff), Energy flow ( photosynthesis and the nitrogen and carbon cycle) and Interdependence (pollution, population and recycling)
It depends which board you're on for OCR gateway it's:
Ecosystems, classification, species,population,interactions between organisms, adaptation, photosynthesis,rate of photosynthesis,fossil and the Theory of evolution,humanimpact on the environment,endangered species,sustainable development.
Cgp definitely the information isn't too heavy they provide for foundation and higher, it's also funny little comments in it which make its kinda funny. Also bite size has the basics but if you want quick tests its useful also BBC class clips, if you wanna take a break from written work.