Unit 1 Defences against pathogens, the human immune system and vaccination Unit 2 Aerobic and anaerobic cellular respiration Unit 3 Maintaining biodiversity and human impacts Unit 5 Hormones and human reproduction Unit 7 Coordination and control: maintaining a constant internal environment Unit 9 Medicines and new treatments for disease Unit 10 Variation and natural selection at the genetic level Unit 11 Classification in modern biology