IB Biology HL study guide
IB Biology HL · Work through your exam, one topic at a time.
IB Biology HL is the higher-level biology course within the International Baccalaureate Diploma Programme, a two-year pre-university qualification taught in schools worldwide and recognised by universities for admission and credit. It suits students who want a rigorous, conceptually demanding biology foundation - typically those heading toward medicine, biomedical science, ecology, or biotechnology - and who are willing to combine strong content knowledge with statistical and experimental reasoning. The syllabus is organised into four broad themes: unity and diversity (molecules, cells, classification, evolution), form and function (transport, gas exchange, immunity, organ systems), interaction and interdependence (ecology, energy flow, populations, human impact), and continuity and change (genetics, molecular biology, reproduction, inheritance). Alongside these runs a practical and inquiry strand assessed through an individual scientific investigation and experimental-skills questions in the written papers. The IB Biology HL study guide has 5 sections and about 1,627 words.
01Unity and Diversity
This domain explores how life is simultaneously unified and diverse: shared molecules, membranes and genetic mechanisms recur across organisms, while variation and evolution generate biodiversity. The exam tests molecular evidence for common ancestry, cell structure, classification and cladistics, evolutionary processes, and biodiversity conservation.
357 words, about 2 min02Form and Function
This domain examines how biological structures at molecular, cellular and organ-system levels enable particular functions. The exam tests structure–function relationships, membrane transport, exchange surfaces, transport systems and organismal adaptations to physical constraints.
330 words, about 2 min03Interaction and Interdependence
This domain examines interactions from molecular reactions to ecosystems. The exam tests enzyme action and metabolic pathways, energy transformations, signalling and defence, population interactions, and the transfer of energy and matter through communities.
319 words, about 2 min04Continuity and Change
This domain examines how genetic information is maintained, expressed and changed, and how populations evolve. The exam tests DNA replication, protein synthesis, mutation, cell division, inheritance, gene expression, natural selection and speciation.
288 words, about 1 min05Experimental Skills and Internal Assessment
This domain tests practical design, data processing, statistical analysis and evaluation, including the internal assessment. The exam expects precise variables, appropriate controls, correct uncertainty, suitable graphs and justified statistical tests.
333 words, about 2 min