# Cambridge O Level Biology Study Notes > Cambridge O Level Biology is an internationally recognised school-level biology course and exam offered by Cambridge International for students usually aged... Canonical URL: https://biologynotesonline.com/cambridge-o-level-biology-study-notes/ Author: Sourav Pan Last updated: February 27, 2026 ![Cambridge O Level Biology Study Notes](https://biologynotesonline.com/wp-content/uploads/2026/02/Cambridge-O-Level-Biology-Study-Notes.jpg) Cambridge O Level Biology is an internationally recognised school-level biology course and exam offered by Cambridge International for students usually aged 14 to 16. It helps students understand the basic concepts of biology, such as cells, plants and animals, human body systems, genetics, and the environment. The course also teaches practical skills through experiments and observations, which improve scientific thinking and problem-solving ability. It prepares students for higher studies in science, especially for advanced-level biology courses. Overall, Cambridge O Level Biology builds a strong foundation in biology and is accepted by schools and colleges around the world. ## 1. Cells - [Cell structure and function](https://biologynotesonline.com/cell-structure-characteristics-types-size-and-shape-functions/) [Human Cell Structure and Functions](https://biologynotesonline.com/human-cell-structure-and-functions/) - [Cell – Definition, Structure, Types, Functions, Examples](https://biologynotesonline.com/cell-structure-characteristics-types-size-and-shape-functions/) - [Animal Cell – Diagram, Structure, Types, Functions](https://biologynotesonline.com/animal-cell-labeled-diagram-structure-types-functions/) - [Cell – Structure, Characteristics, Types, Size and Shape, Functions](https://biologynotesonline.com/cell-structure-characteristics-types-size-and-shape-functions/) - [Eukaryotic Cell – Definition, Structure, Functions, Examples](https://biologynotesonline.com/eukaryotic-cell/) - [Prokaryotic cells – Definition, Structure, Characteristics, Examples](https://biologynotesonline.com/prokaryotic-cells/) - [Prokaryotic Cell and Eukaryotic Cell](https://biologynotesonline.com/prokaryotic-vs-eukaryotic-cells/) - [Difference Between Prokaryotic and Eukaryotic Cells – Prokaryotic Vs Eukaryotic Cells](https://biologynotesonline.com/prokaryotic-vs-eukaryotic-cells/) - [Cell Compartmentalization – Definition, Types, Origins, Importance, Advantages](https://biologynotesonline.com/cell-compartmentalization-definition-types-origins-importance-advantages/) - [Cell Organelles – Structure, Functions, Diagram](https://biologynotesonline.com/cell-organelles-structure-and-their-functions/) - Specialised cells, tissues and organs ## 2. Classification - [Three-domain system – Carl Woese’s Classification](https://biologynotesonline.com/three-domain-system/) ## 3. Movement into and out of cells - [Diffusion – Definition, Causes, Significance, Examples](https://biologynotesonline.com/diffusion-definition-causes-significance-examples/) [Facilitated Diffusion](https://biologynotesonline.com/facilitated-diffusion/) - [Simple Diffusion – definition, principle, examples, applications](https://biologynotesonline.com/simple-diffusion/) - [Facilitated Diffusion vs Active transport](https://biologynotesonline.com/facilitated-diffusion-vs-active-transport/) - [Difference Between Simple Diffusion and Facilitated Diffusion ](https://biologynotesonline.com/simple-diffusion-vs-facilitated-diffusion/) - [Osmosis – Definition, Types, Mechanism, Significance, Examples](https://biologynotesonline.com/osmosis-definition-types-mechanism-significance-examples/) - [Active Transport – Definition, Types, Process, Functions, Examples](https://biologynotesonline.com/active-transport/) [Facilitated Diffusion vs Active transport](https://biologynotesonline.com/facilitated-diffusion-vs-active-transport/) - [Difference Between Active Transport and Passive Transport](https://biologynotesonline.com/active-transport-vs-passive-transport/) - [Passive Transport – Definition, Types, Examples](https://biologynotesonline.com/passive-transport/) ## 4. Biological molecules - [carbohydrates](https://biologynotesonline.com/carbohydrates/) [Carbohydrates – Monosaccharides, Disaccharides, Polysaccharides](https://biologynotesonline.com/carbohydrates-monosaccharides-disaccharides-polysaccharides/) - [lipids (fats and oils)](https://biologynotesonline.com/lipids/) - [proteins](https://biologynotesonline.com/proteins/) - [DNA](https://biologynotesonline.com/dna-definition-structure-properties-types-functions/) - Describe and be able to do chemical tests for: [starch (iodine solution)](https://biologynotesonline.com/iodine-test-principle-procedure/) [Starch Hydrolysis Test – Principle, Procedure, Results, Uses](https://biologynotesonline.com/starch-hydrolysis-test-principle-procedure/) - glucose and maltose (Benedict’s solution) - [Benedict’s Test – Principle, Reagents, Procedure, Result, Limitation](https://biologynotesonline.com/benedicts-test-principle-procedure-result/) - [protein (biuret test)](https://biologynotesonline.com/biuret-test-for-protein-principle-procedure-result-application/) - lipids (ethanol emulsion test) [Lipid Hydrolysis Test – Principle, Procedure, Result](https://biologynotesonline.com/lipid-hydrolysis-test/) ## 5. Enzymes - [Enzymes – Structure, Types, Mode of Action, Functions, Applications, Examples](https://biologynotesonline.com/enzymes/) - Enzyme action - [Effects of temperature and pH](https://biologynotesonline.com/factors-that-affects-enzyme-activity/) ## 6. Plant nutrition - [Photosynthesis](https://biologynotesonline.com/photosynthesis/) - [Leaf structure](https://biologynotesonline.com/leaf-structure-under-the-microscope/) - [Mineral nutrition](https://biologynotesonline.com/mineral-nutrition-in-plants-types-absorption-functions/) ## 7. Transport in flowering plants - [Uptake and transport of water and ions](https://biologynotesonline.com/water-transport-mechanism-in-plants/) [Nutrient Transport Mechanism in Plants](https://biologynotesonline.com/nutrient-transport-mechanism-in-plants/) - [](https://biologynotesonline.com/author/souravbno/)[Mode of Transport Across Plasma Membrane](https://biologynotesonline.com/mode-of-transport-across-plasma-membrane/) - [Mineral Nutrition in Plants – Types, Absorption, Functions](https://biologynotesonline.com/mineral-nutrition-in-plants-types-absorption-functions/)[](https://biologynotesonline.com/author/souravbno/) - [Transpiration](https://biologynotesonline.com/transpiration-types-mechanism-factors-significance/) - [translocation](https://biologynotesonline.com/translocation-in-phloem-structure-phloem-loading-and-unloading/) ## 8. Human nutrition - Diet - [Human digestive system](https://biologynotesonline.com/human-digestive-system-organs-structure-functions/) Describe the functions of the main regions of the digestive system, limited to: mouth – ingestion, physical digestion, chemical digestion of starch by amylase - salivary glands – secretion of saliva containing amylase - stomach – physical digestion, chemical digestion of protein by protease, presence of hydrochloric acid in gastric secretions - small intestine (duodenum and ileum) – chemical digestion of starch by amylase, maltose by maltase, protein by protease and lipids by lipase - liver – production of bile and storage of glycogen - gall bladder – storage of bile - pancreas – alkaline secretion containing amylase, protease and lipase - ileum and colon – absorption - rectum and anus – egestion - Describe the functions of amylase, maltase, protease and lipase, listing the substrates and end-products, limited to: amylase breaks down starch to maltose - maltase breaks down maltose to glucose - protease (pepsin and trypsin) breaks down protein to amino acids - lipase breaks down lipids to fatty acids and glycerol - [Absorption and assimilation in intestine](https://biologynotesonline.com/physiology-of-digestion-organs-mechanism-regulation-functions/) ## 9. Human gas exchange - [Human gas exchange](https://biologynotesonline.com/physiology-of-respiration-respiratory-system-breathing-gas-exchange-mechanism-regulation/) ## 10. Respiration - [Respiration](https://biologynotesonline.com/physiology-of-respiration-respiratory-system-breathing-gas-exchange-mechanism-regulation/#mechanism-of-respiration-in-human) - [Physiological control of respiration – Components, Methods](https://biologynotesonline.com/physiological-control-of-respiration-components-methods/) - [Difference Between Breathing and Respiration – Breathing vs Respiration](https://biologynotesonline.com/breathing-vs-respiration/) - [Aerobic respiration](https://biologynotesonline.com/cellular-respiration-equation/#a-aerobic-respiration) - [Anaerobic respiration](https://biologynotesonline.com/cellular-respiration-equation/#b-anaerobic-respiration) - [Difference between Aerobic and Anaerobic Respiration – Aerobic vs Anaerobic Respiration](https://biologynotesonline.com/aerobic-vs-anaerobic-respiration/) ## 11. Transport in humans - [Circulatory system](https://biologynotesonline.com/human-circulatory-system/) - [Heart](https://biologynotesonline.com/human-heart-definition-location-anatomy-structure-functions/) - Blood vessels - [Blood](https://biologynotesonline.com/blood-cells/) ## 12. Disease and immunity - Disease - [Antibiotics](https://biologynotesonline.com/antibiotics-definition-characteristics-classification-administration/) [Mode of action of antibiotics and classification.](https://biologynotesonline.com/antibiotics-definition-characteristics-classification-administration/) - [Effect of Antibiotics on the Cell Wall](https://biologynotesonline.com/antibiotics-classification-mode-of-action-examples/) - Immunity [Immunity – Definition, Types, Mechanism, Components, and Immunization](https://biologynotesonline.com/immunity/) - [Innate Immunity vs. Acquired Immunity (Adaptive immunity)](https://biologynotesonline.com/innate-immunity-vs-acquired-immunity/) - [Active Immunity – Definition, Characteristics, Types, Examples](https://biologynotesonline.com/active-immunity/) - [Passive Immunity – Definition, Types, Characteristics, Examples](https://biologynotesonline.com/passive-immunity/) - [Innate Immunity – Definition, Types, Mechanism](https://biologynotesonline.com/innate-immunity/) - [Adaptive (Acquired) Immunity](https://biologynotesonline.com/adaptive-acquired-immunity/) - [Humoral Immunity – Definition, Mechanism](https://biologynotesonline.com/humoral-immunity-definition-types-mechanism-functions-examples/) - [Autoimmunity – Definition, Types, Tolerance, Pathogenesis, Mechanisms](https://biologynotesonline.com/autoimmunity-definition-types-tolerance-pathogenesis-mechanisms/) - [Differences between Active Immunity and Passive Immunity](https://biologynotesonline.com/active-immunity-vs-passive-immunity/) - [Differences between Humoral Immunity and Cell mediated Immunity](https://biologynotesonline.com/humoral-immunity-vs-cell-mediated-immunity/) ## 13. Excretion - Excretion - [Urinary system](https://biologynotesonline.com/urinary-system-definition-anatomy-and-physiology/) ## 14. Coordination and control - [Mammalian nervous system](https://biologynotesonline.com/nervous-system/) [The Structure of the Nervous System](https://biologynotesonline.com/the-structure-of-the-nervous-system/) - [Mammalian Sense organs](https://biologynotesonline.com/sense-organs-classification-of-receptors-brief-account-of-visual-and-auditory-receptors-in-man/) - [Mammalian hormones](https://biologynotesonline.com/hormones-structure-types-functions-examples/) - [Homeostasis](https://biologynotesonline.com/homeostasis/) - [Temperature control](https://biologynotesonline.com/skin-definition-structure-disorders-functions/) - Blood glucose control ## 15. Coordination and response in plants - Coordination and response in plants - [Phototropism – Definition, Types, Mechanism, Importance, Examples](https://biologynotesonline.com/phototropism/) ## 16. Development of organisms and continuity of life - Nuclear division - [Asexual Reproduction](https://biologynotesonline.com/asexual-reproduction-definition-types-advantages-examples/) - [Asexual Reproduction in bacteria](https://biologynotesonline.com/asexual-reproduction-definition-types-advantages-examples/) - [Asexual Reproduction in Plants](https://biologynotesonline.com/asexual-reproduction-in-plants/) - [Sexual Reproduction – Stages, Types, Advantages, Examples](https://biologynotesonline.com/sexual-reproduction-stages-types-advantages-examples/) - Sexual reproduction in plants - Sexual reproduction in humans - [Difference Between Asexual and Sexual Reproduction](https://biologynotesonline.com/asexual-vs-sexual-reproduction/) ## 17. Inheritance - [Variation](https://biologynotesonline.com/genetic-variation-definition-types-causes-examples/) - [DNA](https://biologynotesonline.com/dna-definition-structure-properties-types-functions/) - Inheritance [Mendel’s Laws of Inheritance – Mendelian Inheritance](https://biologynotesonline.com/mendels-laws-of-inheritance/) - [Cytoplasmic or Extra-Nuclear Inheritance – Definition, Examples, Significance](https://biologynotesonline.com/cytoplasmic-inheritance-definition-examples-significance/) - [Sex-linked Inheritance – Definition, Characteristics, Examples](https://biologynotesonline.com/sex-linked-inheritance-definition-characteristics-examples/) - [Polygenic Inheritance (Quantitative inheritance) – Characteristics, Mechanism, Examples, Importance](https://biologynotesonline.com/polygenic-inheritance-definition-characteristics-examples-importance/) - [Chromosomal Theory of Inheritance](https://biologynotesonline.com/chromosomal-theory-of-inheritance/) - [Quantitative Inheritance in Plant Breeding](https://biologynotesonline.com/quantitative-inheritance-in-plant-breeding/) - [What is Non-Mendelian Inheritance?](https://biologynotesonline.com/what-is-non-mendelian-inheritance/) - Selection [Selection Methods For Self pollinated Plants – Breeding self-pollinated species](https://biologynotesonline.com/selection-methods-for-self-pollinated-plants/) - [Artificial Selection – Theory, Types, Advantages, Examples](https://biologynotesonline.com/artificial-selection-theory-types-advantages-examples/) - [Natural Selection – Definition, Theory, Types, Examples](https://biologynotesonline.com/natural-selection-definition-theory-types-examples/) - [Difference between Natural and artificial selection – Natural vs artificial selection](https://biologynotesonline.com/natural-vs-artificial-selection/) - [Differences Between Pureline Selection and Mass Selection](https://biologynotesonline.com/pureline-selection-vs-mass-selection/) - [Mass Selection Method – Procedure, Applications, Merits, Demerits](https://biologynotesonline.com/mass-selection-method-procedure-applications-merits-demerits/) - [Speciation – Definition, Causes, Types, Process](https://biologynotesonline.com/speciation-definition-causes-types-process/) - [Pureline Selection – Procedure, Applications, Advantages, Disadvantages](https://biologynotesonline.com/pureline-selection-procedure-applications-advantages-disadvantages/) ## 18. Biotechnology and genetic modification - Biotechnology - Genetic modification [Applications of Plant Biotechnology](https://biologynotesonline.com/applications-of-plant-biotechnology/) - [Agrobacterium-Mediated Gene Transfer in Plants](https://biologynotesonline.com/agrobacterium-mediated-gene-transfer/) - [Bacterial Transduction – Definition, Types, Steps, Examples](https://biologynotesonline.com/bacterial-transduction/) - [Bt Crops – Definition, Types, Advantages, Limitations](https://biologynotesonline.com/bt-crops-definition-types-advantages-limitations/) - [Bacterial Transformation – Definition, Principle, Steps, Examples](https://biologynotesonline.com/bacterial-transformation/) - [BT Cotton – Definition, Features, Development, Advantages, Limitations](https://biologynotesonline.com/bt-cotton-definition-features-development-advantages-limitations/) ## 19. Relationships of organisms with one another and with the environment - Energy flow [Models of Energy Flow in a Ecosystem – Linear and Y-shaped food chains](https://biologynotesonline.com/models-of-energy-flow/) - [Detritus Food Chain – Definition, Energy Flow, Examples](https://biologynotesonline.com/detritus-food-chain/) - [Energy Flow in Ecosystem](https://biologynotesonline.com/energy-flow-in-ecosystem/) - Nutrient cycles [Carbon cycle – Definition, Steps, Importance, Examples](https://biologynotesonline.com/carbon-cycle/) - [Carbon Fixation – Process, Pathways, Importance](https://biologynotesonline.com/carbon-fixation-process-pathways-importance/) - [Nitrogen Cycle – Definition, Steps, Importance, Examples](https://biologynotesonline.com/nitrogen-cycle-steps-and-significance/) - [Biogeochemical Cycle – Definition, Importance, Examples](https://biologynotesonline.com/biogeochemical-cycle/) - [Nitrogen Fixation – Definition, Importance, Processes](https://biologynotesonline.com/nitrogen-fixation/) - [Sulphur cycle – Definition, Steps, Types, Importance](https://biologynotesonline.com/sulphur-cycle/) - [Decomposition – Definition, Types, Process, Advantages](https://biologynotesonline.com/decomposition-definition-types-process-advantages/) - [Microbial degradation of Pectin – Enzymes, Steps, Mechanisms](https://biologynotesonline.com/microbial-degradation-of-pectin/) - [Microbial Degradation of Chitin – Microorganisms, Enzymes, Steps, Mechanisms](https://biologynotesonline.com/microbial-degradation-of-chitin/) - [Ecosystems](https://biologynotesonline.com/structure-and-function-of-ecosystems/) [Population – Definition, Characteristics, Growth, Regulation, Types](https://biologynotesonline.com/population/) - [Speciation – Definition, Causes, Types, Process](https://biologynotesonline.com/speciation-definition-causes-types-process/) - [Population genetics – Unitary and modular population, Hardy-Weinberg law](https://biologynotesonline.com/population-genetics-unitary-and-modular-population-hardy-weinberg-law/) - [Population Characteristics](https://biologynotesonline.com/population-characteristics/) - [Community – Definition, Types, Characterisitcs, Importance](https://biologynotesonline.com/community-definition-types-characterisitcs-importance/) - [Community Characteristics – Dominance, Diversity, Species richness, Abundance, Stratification](https://biologynotesonline.com/community-characteristics/) - [Climax Community – Definition, Characteristics, Theories](https://biologynotesonline.com/climax-community/) - [Biodiversity – Definition, Types, Importance, Conservation](https://biologynotesonline.com/biodiversity/) - [Biodiversity Hotspots – Definition, Criteria, Importance, Examples](https://biologynotesonline.com/biodiversity-hotspots-definition-criteria-importance-examples/) - [Effects of humans on ecosystems](https://biologynotesonline.com/disruptions-to-ecosystems-causes-consequences-preventions/#human-impacts-on-ecosystems) - Conservation [Biodiversity – Definition, Types, Importance, Conservation](https://biologynotesonline.com/biodiversity/) - [Germplasm conservation Methods](https://biologynotesonline.com/germplasm-conservation-methods/) - [Ecology in Wildlife Conservation and Management](https://biologynotesonline.com/ecology-in-wildlife-conservation-and-management/)