Cambridge O Level · 5090 · Data 2020–2025
Most-tested topics in O-Level Biology
Just 3 chapters — Plant nutrition, Enzymes, Relationships of organisms with one another and with the environment — carry about 32% of all the marks. Revise those first.
Based on 84 real Cambridge past papers and 8,477 tagged marks, 2020–2025. Ranked by marks, not guesswork.
Historical counts from past papers — not an exam prediction. Download the data (CSV)
Revise these first
The topics that carry the most marks, highest first. Each opens the free past-paper questions.
- 1Practise →5.2 Effects of temperature and pH6% of marksEnzymesEvery year
- 2Practise →5.1 Enzyme action5% of marksEnzymesEvery year
- 3Practise →6.1 Photosynthesis5% of marksPlant nutritionEvery year
- 4Practise →3.1 Diffusion and osmosis4% of marksMovement into and out of cellsEvery year
- 5Practise →6.2 Leaf structure4% of marksPlant nutritionEvery year
- 6Practise →4.1 Biological molecules4% of marksBiological moleculesEvery year
- 7Practise →1.1 Cell structure and function4% of marksCellsEvery year
- 8Practise →19.4 Effects of humans on ecosystems3% of marksRelationships of organisms with one another and with the environmentEvery year
See the full breakdown — all 52 topics across 19 chapters
Plant nutrition
11% of marks- 6.1 PhotosynthesisEvery year441 marks · 76 qs
- 6.2 Leaf structureEvery year333 marks · 44 qs
- 6.3 Mineral nutritionEvery year188 marks · 30 qs
Enzymes
11% of marks- 5.2 Effects of temperature and pHEvery year481 marks · 51 qs
- 5.1 Enzyme actionEvery year457 marks · 65 qs
Relationships of organisms with one another and with the environment
10% of marks- 19.4 Effects of humans on ecosystemsEvery year294 marks · 52 qs
- 19.3 Ecosystems and biodiversityEvery year206 marks · 26 qs
- 19.1 Energy flowEvery year204 marks · 48 qs
- 19.5 ConservationRecurring83 marks · 9 qs
- 19.2 Nutrient cyclesEvery year62 marks · 32 qs
Transport in humans
7% of marks- 11.1 Circulatory systemEvery year207 marks · 42 qs
- 11.4 BloodEvery year149 marks · 30 qs
- 11.3 Blood vesselsEvery year128 marks · 32 qs
- 11.2 HeartEvery year126 marks · 32 qs
Coordination and control
6% of marks- 14.1 Mammalian nervous systemEvery year159 marks · 43 qs
- 14.2 Mammalian sense organsEvery year93 marks · 33 qs
- 14.5 Temperature controlEvery year82 marks · 31 qs
- 14.3 Mammalian hormonesEvery year71 marks · 21 qs
- 14.4 HomeostasisRecurring66 marks · 13 qs
- 14.6 Blood glucose controlEvery year65 marks · 28 qs
Respiration
6% of marks- 10.2 Aerobic respirationEvery year172 marks · 26 qs
- 10.3 Anaerobic respirationEvery year165 marks · 40 qs
- 10.1 RespirationEvery year151 marks · 26 qs
Inheritance
5% of marks- 17.3 InheritanceEvery year157 marks · 47 qs
- 17.2 DNAEvery year132 marks · 22 qs
- 17.4 SelectionEvery year105 marks · 25 qs
- 17.1 VariationEvery year59 marks · 17 qs
Development of organisms and continuity of life
5% of marks- 16.3 Sexual reproduction in plantsEvery year182 marks · 38 qs
- 16.2 Asexual and sexual reproductionEvery year110 marks · 22 qs
- 16.4 Sexual reproduction in humansEvery year80 marks · 43 qs
- 16.1 Nuclear divisionEvery year79 marks · 24 qs
Disease and immunity
5% of marks- 12.1 DiseaseEvery year222 marks · 62 qs
- 12.3 ImmunityEvery year125 marks · 26 qs
- 12.2 AntibioticsEvery year78 marks · 25 qs
Movement into and out of cells
5% of marks- 3.1 Diffusion and osmosisEvery year360 marks · 68 qs
- 3.2 Active transportEvery year55 marks · 30 qs
Cells
5% of marks- 1.1 Cell structure and functionEvery year304 marks · 59 qs
- 1.2 Specialised cells, tissues and organsEvery year91 marks · 14 qs
Human nutrition
5% of marks- 8.2 Human digestive systemEvery year181 marks · 43 qs
- 8.1 DietEvery year141 marks · 29 qs
- 8.3 Absorption and assimilationEvery year73 marks · 29 qs
Transport in flowering plants
4% of marks- 7.2 Transpiration and translocationEvery year238 marks · 49 qs
- 7.1 Uptake and transport of water and ionsEvery year129 marks · 32 qs
Biological molecules
4% of marks- 4.1 Biological moleculesEvery year314 marks · 38 qs
Excretion
3% of marks- 13.1 ExcretionEvery year153 marks · 35 qs
- 13.2 Urinary systemEvery year127 marks · 24 qs
Classification
3% of marks- 2.2 Features of organismsEvery year155 marks · 28 qs
- 2.1 Concept and use of a classification systemRecurring94 marks · 13 qs
Biotechnology and genetic modification
2% of marks- 18.1 BiotechnologyEvery year109 marks · 23 qs
- 18.2 Genetic modificationEvery year22 marks · 13 qs
Human gas exchange
1% of marks- 9.1 Human gas exchangeEvery year123 marks · 42 qs
Coordination and response in plants
1% of marks- 15.1 Coordination and response in plantsRecurring96 marks · 19 qs
Turn the data into practice
Every topic above is drawn from real Cambridge O Level Biology papers, tagged to the syllabus. Students can drill the high-frequency topics in the free bank; teachers can turn any of them into a ready-to-print worksheet in seconds. Or explore the full six-year trends in the interactive records.