Understand Biology
Life explored through scale, form, interaction and transformation
IB DP Biology connects molecular processes, cells, organisms and ecosystems. The course is organized through four themes and four levels of biological organization, with experimental design and data interpretation integrated throughout.
Know the papers.
Prepare with purpose.
Paper 1A combines multiple choice with Paper 1B data analysis; Paper 2 uses data, short answers and extended responses. Together the examinations are 80%, while an individual scientific investigation is 20%.
Paper 1A
Short questions test knowledge, application and efficient reasoning. It is completed without a calculator and forms part of the combined Paper 1 weighting.
Paper 1B
Students interpret unfamiliar data, graphs and experimental evidence. Clear scientific reasoning matters as much as reaching a numerical result.
Paper 2
Structured and extended questions combine calculation, explanation and evaluation. The paper rewards connected reasoning across more than one part of the course.
Scientific investigation
Students design and carry out an individual investigation, process evidence and evaluate their method in a report of up to 3,000 words.
Every area,
explained clearly.
Unity and diversity
Common chemistry and shared ancestry sit alongside the extraordinary diversity of living systems.
MoleculesWater, nucleic acids, carbohydrates, lipids and proteins provide common molecular foundations.＋
Water, nucleic acids, carbohydrates, lipids and proteins provide common molecular foundations. Students relate molecular structure to biological function and evidence for common ancestry.
CellsCell structure, membranes, organelles and specialization show unity with variation.＋
Cell structure, membranes, organelles and specialization show unity with variation. Microscopy and cell theory connect observation to claims about living systems.
OrganismsClassification, biodiversity and evolutionary relationships organize biological variety.＋
Classification, biodiversity and evolutionary relationships organize biological variety. Students use evidence to distinguish homologous features and construct relationships.
EcosystemsSpecies diversity and ecological structure emerge from interactions within communities.＋
Species diversity and ecological structure emerge from interactions within communities. Sampling and measures of diversity support evidence-based comparisons.
Form and function
Biological structures are examined as adaptations that perform particular functions at different scales.
MoleculesProtein shape, enzyme action and membrane components illustrate structure-function relationships.＋
Protein shape, enzyme action and membrane components illustrate structure-function relationships. Changes in conditions can alter molecular behaviour and biological performance.
CellsMembranes, transport, organelles and cell specialization enable controlled exchange and division of labour.＋
Membranes, transport, organelles and cell specialization enable controlled exchange and division of labour. Surface-area-to-volume relationships constrain cell form.
OrganismsGas exchange, transport, movement and communication depend on specialized tissues and organs.＋
Gas exchange, transport, movement and communication depend on specialized tissues and organs. Comparative examples reveal how form suits environment and lifestyle.
EcosystemsAdaptations affect where organisms live and how they obtain resources.＋
Adaptations affect where organisms live and how they obtain resources. Niches and limiting factors connect individual form to community structure.
Interaction and interdependence
Living systems depend on communication, exchange and relationships within and between levels of organization.
MoleculesEnzymes, receptors and signalling molecules coordinate biochemical interactions.＋
Enzymes, receptors and signalling molecules coordinate biochemical interactions. Feedback and specificity make these systems responsive yet controlled.
CellsCell signalling, defence and coordinated tissue behaviour depend on recognition and communication.＋
Cell signalling, defence and coordinated tissue behaviour depend on recognition and communication. Students connect molecular events to whole-organism responses.
OrganismsNervous, hormonal, immune and reproductive systems coordinate internal and external interactions.＋
Nervous, hormonal, immune and reproductive systems coordinate internal and external interactions. Homeostasis demonstrates how feedback maintains stability.
EcosystemsFood webs, competition, predation and mutualism transfer matter and energy.＋
Food webs, competition, predation and mutualism transfer matter and energy. Population change is interpreted through biotic and abiotic interactions.
Continuity and change
Inheritance, reproduction, evolution and ecological change explain persistence and transformation through time.
MoleculesDNA replication, gene expression and mutation transmit information while generating variation.＋
DNA replication, gene expression and mutation transmit information while generating variation. Molecular evidence helps reconstruct evolutionary histories.
CellsCell division supports growth, repair and reproduction.＋
Cell division supports growth, repair and reproduction. Control of the cell cycle links continuity to development and disease.
OrganismsInheritance, reproduction, natural selection and speciation explain continuity and diversity.＋
Inheritance, reproduction, natural selection and speciation explain continuity and diversity. Students analyse crosses, variation and evolutionary evidence.
EcosystemsSuccession, climate change and human activity alter communities over time.＋
Succession, climate change and human activity alter communities over time. Conservation decisions require interpreting evidence, uncertainty and competing priorities.
The guide paraphrases the current IB subject framework; official teaching sequences and examples may vary by school.
Content is presented as an original student-friendly explanation. Always use the official syllabus for the examination year as the final authority.