IB Biology

The whole course. Four themes, each running from molecules to ecosystems. Find your topic; the page will tell you which parts of it you own.

IB Biology guide, first assessment 2025 (updated May 2026 for first assessment 2028).

Theme	1 Molecules	2 Cells	3 Organisms	4 Ecosystems
A Unity and diversity	A1.1 Water A1.2 Nucleic acids	A2.1 Origins of cells HL A2.2 Cell structure A2.3 Viruses HL	A3.1 Diversity of organisms A3.2 Classification and cladistics HL	A4.1 Evolution and speciation A4.2 Conservation of biodiversity
B Form and function	B1.1 Carbohydrates and lipids B1.2 Proteins	B2.1 Membranes and membrane transport B2.2 Organelles and compartmentalization B2.3 Cell specialization	B3.1 Gas exchange B3.2 Transport B3.3 Muscle and motility HL	B4.1 Adaptation to environment B4.2 Ecological niches
C Interaction and interdependence	C1.1 Enzymes and metabolism C1.2 Cell respiration C1.3 Photosynthesis	C2.1 Chemical signalling HL C2.2 Neural signalling	C3.1 Integration of body systems C3.2 Defence against disease	C4.1 Populations and communities C4.2 Transfers of energy and matter
D Continuity and change	D1.1 DNA replication D1.2 Protein synthesis D1.3 Mutation and gene editing	D2.1 Cell and nuclear division D2.2 Gene expression HL D2.3 Water potential	D3.1 Reproduction D3.2 Inheritance D3.3 Homeostasis	D4.1 Natural selection D4.2 Stability and change D4.3 Climate change