How to use this series; How to use this resource; Introduction; 1 Characteristics and classification of living organisms; 2 Cells; 3 Movement into and out of cells; Past paper practice 1; 4 Biological molecules; 5 Enzymes; 6 Plant nutrition; 7 Human nutrition; Past paper practice 2; 8 Transport in plants; 9 Transport in animals; 10 Diseases and immunity; Part paper practice 3; 11 Respiration and gas exchange; 12 Coordination and response; 13 Excretion and homeostasis; Past paper practice 4; 14 Reproduction in plants; 15 Reproduction in humans; 16 Chromosomes, genes and proteins; 17 Variation and selection; Past paper practice 5; 18 Organisms and their environment; 19 Human influences on ecosystems; 20 Biotechnology and genetic modification; Past paper practice 6; Practical guidance (online only).