Biology HL

The complete IB Biology HL path, including shared SL/HL material and every additional higher level extension.

Core material and HL extensions in one reading order, with each extension marked. For first assessment 2025.

Switch to SL
  1. 1Elements, Molecules and WaterBegin molecular biology with the elements shared by living systems, the dose-dependent roles of trace elements, and the molecular explanation for water's life-supporting properties.8 sections, about 585 minIncludes HL extensions
  2. 2Metabolism, Respiration and PhotosynthesisFollow energy and matter through enzyme-controlled pathways, ATP production in respiration, and carbon fixation in photosynthesis—from active-site collisions to chemiosmotic membranes.10 sections, about 425 minIncludes HL extensions
  3. 3DNA and Protein SynthesisFollow genetic information from faithful DNA copying through transcription, RNA processing and translation, then investigate mutation, gene editing and epigenetic control.12 sections, about 525 minIncludes HL extensions
  4. 4GeneticsConnect chromosome organization to inheritance, predict simple and complex crosses, infer family genotypes, and test linkage models with recombination and chi-squared evidence.10 sections, about 509 minIncludes HL extensions
  5. 5Cell StructureBuild cell biology from origin-of-life evidence through prokaryotic and eukaryotic organization, endosymbiosis, microscopy, viruses and rapid viral evolution.12 sections, about 662 minIncludes HL extensions
  6. 6Cell FunctionExplain how membranes control exchange, organelles coordinate cellular work, geometry constrains size, and cell division preserves or reshuffles genetic information.10 sections, about 647 minIncludes HL extensions
  7. 7Cell Control and CommunicationExplain how cells detect, transmit and integrate information through receptors, neurons, synapses, hormones, feedback systems and plant growth regulators.11 sections, about 881 minIncludes HL extensions
  8. 8PhysiologyBuild a connected account of multicellular organization, animal and plant transport, gas exchange, reproduction and homeostasis through structure, gradients and feedback.9 sections, about 1060 minIncludes HL extensions
  9. 9Coordination, Muscles and MotilityConnect nervous coordination to reflexes, enteric movement, skeletons and joints, sliding-filament contraction, motor-unit recruitment and whole-animal locomotion.6 sections, about 645 minIncludes HL extensions
  10. 10Defence against DiseaseBuild disease defence from skin and clotting through innate and adaptive immunity, then connect HIV, antibiotics, zoonoses, allergy and vaccination to population health.7 sections, about 813 min
  11. 11Evolution, Speciation and EcosystemsReconstruct ancestry with classification and cladistics, model how gene pools evolve and split, and connect adaptation, niches and competition to biodiversity.6 sections, about 738 minIncludes HL extensions
  12. 12Ecological RelationshipsTrace nutrition, energy, matter and population change through ecosystems, then evaluate succession, biodiversity loss, conservation and climate-driven disruption.8 sections, about 1080 minIncludes HL extensions