It is always best and safer to cover all chapters while doing your revision.
However, you might want to pay more attention to the following chapters:
Form 4:
Chapter 2: organelles and their function/s. eg: mitochondrion, chloroplast, rough ER, Golgi apparatus. Chapter 3: Plasma membrane, the type of transport, ie: osmosis, facilitated diffusion, simple diffusion, active transport.
Chapter 4: production of extracellular enzyme, enzyme & its characteristics, lock-and-key hypothesis, enzyme & its uses in industries.
Chapter 5: cell cycle & cell division, formation of cancer cells.
Chapter 6: healthy food pyramid, digestion and assimilation, balance diet, photosynthesis
Chapter 7: Respiration in plant, respiratory structure and gaseous exchange in human, insect, fish, frog.
Chapter 8: food chains and food web, colonisation and succession in a pond.
Chapter 9: deforestation, thinning of the ozone, acid rain.
Form 5:
Chapter 1: lymphatic system, immunity
Chapter 3: transmission of nerve impulses across the synapse
Chapter 4: menstrual cycle and hormones related to this cycle, family planning.
Chapter 5/6: drawing of a genetic cross diagram (Mendel's first law and second law), drawing of Punnet square. causes of variation.
All the best!
