I've just done my first year of geography A-level, (I got full marks on both papers), and I'd say that the stepup is probably the smallest one like other people have said, but don't underestimate some of the topics you have never studied. Rivers and Population were easy for me, because I'd been doing them for the last 2 years before a level. However, Health and glaciation were harder, but being a physical geographer glaciation turned out to be my favourite one. I hated health with a passion and definately got complacent towards the end. Just make sure your notes are up to date and organised and you'll be fine. One massive, massive point is to get your terminology down to a tee. It's one of those things you pick up going along, but make sure you cram as much topic-specific vocab into everything as you can, especially when doing practice question because once you get used to it, it becomes second nature and it's very hard to forget. Just please remeber this because terminology is a huge deal-breaker and will mean the difference between a C and an A, quite literally. One more thing, always include located examples or examples in your 7 and 15 marks answers!
Enjoy Geography A-level and well done on your results!