Understand Biology
Cambridge AS & A Level Biology course and assessment guide
Cambridge AS & A Level Biology combines secure subject knowledge with application, analysis and clear communication. This guide groups the official syllabus content into a readable learning journey and explains the usual assessment progression.
Know the papers.
Prepare with purpose.
The AS route can be taken as a qualification or as the first part of the full A Level. The final paper combination depends on the subject and entry route.
AS theory
AS candidates demonstrate knowledge, application and interpretation across the AS content.
Practical skills
Sciences include a timetabled practical paper; mathematics assesses technique and problem solving through written papers.
A Level theory
A Level adds more demanding content and unfamiliar applications, requiring linked reasoning across topics.
Planning, analysis and evaluation
Science candidates plan investigations and evaluate evidence; mathematics candidates choose methods and communicate complete solutions.
Every area,
explained clearly.
AS Level cellular and organism biology
The course moves from molecules and cells to transport, disease and immunity.
Cell structure and microscopyProkaryotic and eukaryotic cells are compared through organelles and ultrastructure.＋
Prokaryotic and eukaryotic cells are compared through organelles and ultrastructure. Magnification, resolution and image interpretation make microscopy quantitative.
Biological molecules and enzymesCarbohydrates, lipids, proteins, water and nucleic acids are linked to biological roles.＋
Carbohydrates, lipids, proteins, water and nucleic acids are linked to biological roles. Enzyme kinetics and experimental variables connect structure to reaction rate.
Membranes and cell divisionMembrane organization explains transport and cell signalling.＋
Membrane organization explains transport and cell signalling. The cell cycle, mitosis and chromosome behaviour support growth and genetic continuity.
Nucleic acids and protein synthesisDNA replication and gene expression explain how information is stored and used.＋
DNA replication and gene expression explain how information is stored and used. The genetic code links nucleotide sequence to protein structure.
Transport in plantsXylem, phloem, transpiration and translocation move water and assimilates.＋
Xylem, phloem, transpiration and translocation move water and assimilates. Adaptations and experiments connect tissues to whole-plant transport.
Transport in mammalsThe heart, circulation, blood and tissue fluid deliver materials and maintain exchange.＋
The heart, circulation, blood and tissue fluid deliver materials and maintain exchange. Pressure changes and vessel structure explain efficient flow.
Gas exchange, disease and immunityExchange surfaces support diffusion while infectious disease challenges body systems.＋
Exchange surfaces support diffusion while infectious disease challenges body systems. Immune responses, vaccination and antibiotics are analysed through evidence.
A Level extension
Energy transfer, coordination, inheritance, evolution and ecology build a connected account of living systems.
Energy and respirationATP links energy-releasing pathways to cellular work.＋
ATP links energy-releasing pathways to cellular work. Glycolysis, aerobic respiration and anaerobic pathways are compared.
PhotosynthesisLight-dependent reactions and carbon fixation convert light energy into organic molecules.＋
Light-dependent reactions and carbon fixation convert light energy into organic molecules. Limiting factors and practical investigations connect biochemistry to productivity.
HomeostasisNervous, hormonal and kidney mechanisms maintain internal conditions through feedback.＋
Nervous, hormonal and kidney mechanisms maintain internal conditions through feedback. Blood glucose and water balance provide major case studies.
Coordination and responseNerve impulses, synapses, muscles, hormones and plant responses coordinate behaviour.＋
Nerve impulses, synapses, muscles, hormones and plant responses coordinate behaviour. Molecular mechanisms are connected to organism-level outcomes.
Genetics and selectionMeiosis, inheritance, gene control and variation generate patterns across generations.＋
Meiosis, inheritance, gene control and variation generate patterns across generations. Natural and artificial selection explain changing allele frequencies.
Biodiversity, classification and conservationPhylogeny, taxonomy and molecular evidence organize diversity.＋
Phylogeny, taxonomy and molecular evidence organize diversity. Conservation decisions combine ecological data, genetics and human priorities.
Genetic technologyPCR, sequencing, electrophoresis, gene editing and recombinant DNA enable analysis and modification.＋
PCR, sequencing, electrophoresis, gene editing and recombinant DNA enable analysis and modification. Applications are evaluated for evidence, risk and ethics.
A student-friendly summary of the Cambridge International AS & A Level syllabus. Centres should confirm the syllabus version and component option for their examination series.
Content is presented as an original student-friendly explanation. Always use the official syllabus for the examination year as the final authority.