QuestionQuestion

IB Biology HL

Follow the IB Biology HL syllabus from molecules to ecosystems, including higher-level extensions. Connect biological mechanisms, interpret unfamiliar data and practise precise explanations using the linked concepts and question bank.

Course
Biology
Level
HL

Explore the IB Biology HL syllabus

Explore the IB Biology HL topic map below. Open a theme to see its topics, connect ideas across biological scales, and choose a manageable focus for your next study session. This map shows syllabus structure; notes and questions are published separately.

4
syllabus groups
40
mapped topics
  1. A Unity and Diversity9 topics
  2. B Form and Function10 topics
  3. C Interaction and Interdependence9 topics
  4. D Continuity and Change12 topics

How to study IB Biology HL

Make each study session count: explain one idea, test it from memory, then use evidence to improve your answer.

Choose the right way to practise

Match the activity to the thinking demanded by the topic instead of using one revision technique across every part of the course.

  • Mechanisms at molecular and cellular scale

    Water, membranes, enzymes, respiration and photosynthesis

    Redraw structures and pathways from memory. Then change one condition or component and predict the effect, explaining each causal step rather than naming the final outcome only under exam conditions.

    Review the syllabus

  • Genetics, inheritance and change

    DNA replication, protein synthesis, inheritance and natural selection

    Separate the process from the evidence. Work through an example step by step, then use its result to justify a genetic or evolutionary conclusion with the correct level of biological organisation.

    Review the syllabus

  • Physiology and ecology

    Gas exchange, transport, homeostasis, populations and ecosystems

    Link adaptation to function, then function to a system-level consequence. For graphs, describe the measured pattern with comparative values before proposing a biological explanation or evaluating competing causes.

    Review the syllabus

  • Investigation and unfamiliar data

    Variables, uncertainty, graphical evidence, conclusions and evaluation

    Identify variables and units before interpreting a trend. For evaluation, name the limitation, explain its likely effect on the evidence and propose a specific improvement that addresses that limitation.

    Review the syllabus

Build a consistent study approach

Use the IB Biology HL syllabus map to choose one topic before opening your notes. Write down the question you want to answer: how does this structure support its function, what causes this change, or which evidence supports the explanation? After reading, close the page and reconstruct the answer in your own words. Sketch a labelled diagram when the relationship is easier to show than describe. Check the gaps against your source before moving on.

Build your revision around explanation and application. The exam format helps you plan a balance of recall, data interpretation and extended answers. When marking a practice response, identify exactly what was missing: a definition, a causal step, a comparison or a value from the data. Rewrite that part, then try a different question later. Keep a short error list and use the study methods to choose a more useful task than simply rereading the same page.

IB Biology HL assessment format

External assessment contributes 80% and the scientific investigation contributes 20%. Use the component differences to balance rapid retrieval, unfamiliar data, extended biological explanations and investigation skills for HL.

Paper / componentQuestionsTime% of grade
Paper 175 marksPaper 1A multiple-choice questions and Paper 1B compulsory data-based questions addressing the organising themes.How to prepare: Combine fast retrieval with regular interpretation of unfamiliar tables, graphs and experimental contexts; explain why rejected options conflict with biological evidence.2 hours36%
Paper 280 marksData-based and short-answer questions followed by extended-response questions.How to prepare: Practise complete causal chains under time pressure, using precise terminology and selecting evidence that directly answers the command term.2 hours 30 minutes44%
Scientific investigation24 marksOne individual open-ended scientific investigation, internally assessed and externally moderated.How to prepare: Develop a focused research question, controlled method, defensible data analysis, evidence-based conclusion and evaluation tied to specific limitations.10 recommended course hours20%

SourceInternational Baccalaureate Organization · IB Biology subject brief — first assessment 2025IB Biology · First assessment 2025

Frequently Asked Questions

Choose one topic from the syllabus map. Explain its main idea without looking at your notes, check what you missed, then answer a related question. Use the errors to decide what to revisit in your next session.

Read with a specific question in mind. Close the notes and explain the answer, label a diagram or reconstruct a sequence from memory. Reopen them to correct gaps, then check whether you can apply the idea in a new context.

Identify variables and units, describe the pattern with comparative values, then explain it biologically. Keep description and explanation separate, and when evaluating evidence state the limitation, its likely effect and a specific improvement.

Begin short timed sets once individual Topics can be explained without notes. Move to mixed Paper 1 and Paper 2 work after several Topics are secure, preserving unseen current-syllabus papers for full simulations where possible.