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IB Biology SL and HL

38 lessons at SL. 65 at HL, with every HL-only topic. Five-minute lessons, exam-style questions and timed mock papers.

Start free See plans
Units
4
SL lessons
38
HL lessons
65
Questions
381
Key terms
180
Formulas
29

What you will study

Every lesson follows the current IB guide. Lessons marked HL are in the HL course only. The first unit is free.

Theme A · Unity and diversity7 SL · 13 HL lessons · free
  1. A1.1Water
  2. A1.2Nucleic acids
  3. A2.2Cells and microscopy
  4. A2.2Eukaryotic cells
  5. A3.1Diversity of organisms
  6. A4.1Evidence for evolution
  7. A4.2Conservation of biodiversity
  8. A1.2DNA structure in depthHL
  9. A2.1Origins of cellsHL
  10. A2.2Endosymbiosis and differentiationHL
  11. A2.3VirusesHL
  12. A3.2Classification and cladisticsHL
  13. A4.1Speciation in depthHL
Theme B · Form and function9 SL · 14 HL lessons
  1. B1.1Carbohydrates and lipids
  2. B1.2Proteins
  3. B2.1Membranes and transport
  4. B2.2Organelles and compartments
  5. B2.3Cell specialization
  6. B3.1Gas exchange
  7. B3.2Blood vessels and xylem
  8. B4.1Adaptation to environment
  9. B4.2Ecological niches
  10. B1.2Protein structureHL
  11. B2.1Membrane proteins in depthHL
  12. B3.1Oxygen transportHL
  13. B3.2The heart and phloemHL
  14. B3.3Muscle and motilityHL
Theme C · Interaction and interdependence9 SL · 15 HL lessons
  1. C1.1Enzymes and metabolism
  2. C1.2Cell respiration
  3. C1.3Photosynthesis
  4. C2.2Neurons and synapses
  5. C3.1Integration of body systems
  6. C3.2Defence against disease
  7. C4.1Populations and communities
  8. C4.2Energy flow in ecosystems
  9. C4.2The carbon cycle
  10. C1.1Controlling enzymesHL
  11. C1.2Respiration in depthHL
  12. C1.3Photosynthesis in depthHL
  13. C2.1Chemical signallingHL
  14. C2.2Action potentials in depthHL
  15. C3.1Plant hormonesHL
Theme D · Continuity and change13 SL · 23 HL lessons
  1. D1.1DNA replication
  2. D1.2Protein synthesis
  3. D1.3Mutations
  4. D2.1Mitosis
  5. D2.1Meiosis
  6. D2.3Water movement in cells
  7. D3.1Human reproduction
  8. D3.1Plant reproduction
  9. D3.2Inheritance
  10. D3.3Homeostasis
  11. D4.1Natural selection
  12. D4.2Stability and change
  13. D4.3Climate change
  14. D1.1Replication in depthHL
  15. D1.2Processing genes and proteinsHL
  16. D1.3Gene editingHL
  17. D2.1Cell cycle and cancerHL
  18. D2.2Gene expression and epigeneticsHL
  19. D2.3Water potentialHL
  20. D3.1Gametes and pregnancyHL
  21. D3.2Dihybrid crosses and linkageHL
  22. D3.3The kidneyHL
  23. D4.1Gene pools and selectionHL

Try a question

From “Water”.

Questions are in English, like the exam. Every answer comes with an explanation.

Which property of water allows a column of water to be pulled up the xylem of a tall tree?

  1. ALow density of ice
  2. BBeing a non-polar solvent
  3. CCohesion
  4. DHigh specific heat capacity
Show the answer

C. Cohesion

Hydrogen bonds between water molecules hold the column together under tension.

Start Biology today.

The first unit is free. No card needed.

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