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IB Diploma Biology HL

IB Diploma Biology HL is sat as two written papers (2 hours and 2 hours 30 minutes) and an internal assessment worth 20%. Here are all 16 topics, with free revision notes, exam questions with mark schemes, flashcards and mind maps.

Biology SLBiology HL

What do you want to do?

Revision notesShort notes for every spec point, with diagrams272 notesExam questionsExam-style questions with mark schemes314 questionsFlashcardsFlip, mark and practise what you don't know855 cardsMind mapsEach topic on one page16 mind mapsTopic testsPrintable tests with the mark scheme16 printable testsPracticalsMethod, variables and safety for each one37 practicals

Topics

All papers

Any topic can come up on any paper · Paper 1: 2 hours · Paper 2: 2 hours 30 minutes · Internal assessment: About 10 hours, written up in at most 3,000 words
  1. A1Molecules (Unity and diversity)Water · Nucleic acids2 subtopics
  2. A2Cells (Unity and diversity)Origins of cells · Cell structure · Viruses3 subtopics
  3. A3Organisms (Unity and diversity)Diversity of organisms · Classification and cladistics2 subtopics
  4. A4Ecosystems (Unity and diversity)Evolution and speciation · Conservation of biodiversity2 subtopics
  5. B1Molecules (Form and function)Carbohydrates and lipids · Proteins2 subtopics
  6. B2Cells (Form and function)Membranes and membrane transport · Organelles and compartmentalization · Cell specialization3 subtopics
  7. B3Organisms (Form and function)Gas exchange · Transport · Muscle and motility3 subtopics
  8. B4Ecosystems (Form and function)Adaptation to environment · Ecological niches2 subtopics
  9. C1Molecules (Interaction and interdependence)Enzymes and metabolism · Cell respiration · Photosynthesis3 subtopics
  10. C2Cells (Interaction and interdependence)Chemical signalling · Neural signalling2 subtopics
  11. C3Organisms (Interaction and interdependence)Integration of body systems · Defence against disease2 subtopics
  12. C4Ecosystems (Interaction and interdependence)Populations and communities · Transfers of energy and matter2 subtopics
  13. D1Molecules (Continuity and change)DNA replication · Protein synthesis · Mutation and gene editing3 subtopics
  14. D2Cells (Continuity and change)Cell and nuclear division · Gene expression · Water potential3 subtopics
  15. D3Organisms (Continuity and change)Reproduction · Inheritance · Homeostasis3 subtopics
  16. D4Ecosystems (Continuity and change)Natural selection · Stability and change · Climate change3 subtopics

What the labels mean

HL only
Additional Higher Level content, only for HL students. SL students can skip it.

Anything without a label is for everyone taking IB Diploma Biology HL.

About IB Diploma Biology HL

IB Diploma Biology (first assessment 2025) has four themes (Unity and diversity, Form and function, Interaction and interdependence, Continuity and change), each studied at four levels: molecules, cells, organisms and ecosystems. That gives the 16 topics A1 to D4. HL students learn all the Standard Level content plus the additional higher level content, labelled HL only on this site: six whole topics (A2.1, A2.3, A3.2, B3.3, C2.1 and D2.2) and extra points in many others. Both papers can test any theme. Paper 1 has multiple-choice questions (1A) and data-based questions (1B). Paper 2 has data-based and short-answer questions (2A) and extended-response questions (2B). The internal assessment is a scientific investigation of your own.

Paper 1

Time
2 hours
Marks
36% of the grade: 75 marks
Topics
Paper 1A: 40 multiple-choice questions, with no marks taken off for wrong answers. Paper 1B: four data-based questions on experimental work and the syllabus. Any theme can come up.

Paper 2

Time
2 hours 30 minutes
Marks
44% of the grade: 80 marks
Topics
Section A: a data-based question and short-answer questions. Section B: two extended-response questions from a choice of three. Any theme can come up.

Internal assessment

Time
About 10 hours, written up in at most 3,000 words
Marks
20% of the grade: 24 marks
Topics
A scientific investigation of your own research question, marked by your teacher and moderated by the IB