Below is a list (by no means exhaustive!) of topics you are sure to encounter in A-level biology and are frequently big features in exam papers.
If you are a GCSE student soon to be starting A-level, it would be highly recommended that you have a good understanding of them.
- Size and surface area to volume ratio
- Condensation and hydrolysis
- Diffusion, osmosis and active transport
- The effect of temperature on the rates at which reactions and processes occur
- Enzymes and the factors affecting the rate of enzyme-controlled reactions
- The concept of a species
- DNA and complementary base pairing
Please note: Check your specification; different exam boards place different amounts of focus on certain topics. Your specification is your best friend! You should be referring to it regularly.