Revision guides
AQA Biology, explained clearly.
Free guides that teach the content, topic by topic, written by an AQA Biology specialist. When you are ready to test yourself, Phlo AI and the flashcards take you from knowing it to proving it in the exam.
A-Level
Topic 1Biological Molecules8 guides
AQA A-Level Biology: Biological Molecules overviewAn overview of AQA A-Level Biology Topic 1: monomers and polymers, carbohydrates, lipids, proteins, enzymes, nucleic acids, ATP, water and inorganic ions, with a guide to each.
AQA A-Level Biology: Monomers and PolymersA clear revision guide to monomers and polymers for AQA A-Level Biology: condensation and hydrolysis reactions, the bonds each group of molecules forms, and why the same two reactions build them all.
AQA A-Level Biology: CarbohydratesA clear revision guide to carbohydrates for AQA A-Level Biology: alpha and beta glucose, glycosidic bonds, starch, glycogen and cellulose, and the Benedict's and iodine tests.
AQA A-Level Biology: LipidsA clear revision guide to lipids for AQA A-Level Biology: triglycerides and ester bonds, saturated and unsaturated fatty acids, phospholipids and the bilayer, and the emulsion test.
AQA A-Level Biology: ProteinsA clear revision guide to proteins for AQA A-Level Biology: amino acid structure, peptide bonds, the four levels of protein structure and the bonds that hold each one, and the Biuret test.
AQA A-Level Biology: EnzymesA clear revision guide to enzymes for AQA A-Level Biology: how enzymes work, the induced fit model, and how temperature, pH and concentration affect the rate of reaction.
AQA A-Level Biology: Nucleic AcidsA clear revision guide to nucleic acids for AQA A-Level Biology: nucleotide structure, the DNA double helix, complementary base pairing, how DNA and RNA differ, and semi-conservative replication.
AQA A-Level Biology: ATP, Water and Inorganic IonsA clear revision guide to ATP, water and inorganic ions for AQA A-Level Biology: the structure and hydrolysis of ATP, why cells use it, the properties of water, and the roles of four key ions.
Topic 2Cells6 guides
AQA A-Level Biology: Eukaryotic Cell StructureA clear revision guide to eukaryotic cell structure for AQA A-Level Biology: the organelles, what each one does, and how their structure fits their function.
AQA A-Level Biology: Prokaryotic Cells and VirusesA clear revision guide to prokaryotic cells and viruses for AQA A-Level Biology: prokaryote structure, how prokaryotes compare with eukaryotes, and why viruses are acellular.
AQA A-Level Biology: Microscopy and Studying CellsA clear revision guide to studying cells for AQA A-Level Biology: magnification and resolution, optical, TEM and SEM microscopes, magnification calculations and cell fractionation.
AQA A-Level Biology: Mitosis and the Cell CycleA clear revision guide to the cell cycle and mitosis for AQA A-Level Biology: interphase, the stages of mitosis, why cancer forms, and how prokaryotes and viruses replicate.
AQA A-Level Biology: Transport Across Cell MembranesA clear revision guide to membrane transport for AQA A-Level Biology: the fluid mosaic model, diffusion, facilitated diffusion, osmosis, active transport and co-transport.
AQA A-Level Biology: The Immune SystemA clear revision guide to the immune system for AQA A-Level Biology: antigens, phagocytosis, T and B lymphocytes, antibodies, vaccines, HIV, and monoclonal antibodies.
Topic 4Genetic Information and Variation8 guides
AQA A-Level Biology: DNA, RNA and ChromosomesA clear revision guide to DNA, RNA and chromosomes for AQA A-Level Biology: how DNA differs between eukaryotes and prokaryotes, the structure of mRNA and tRNA, and chromosomes.
AQA A-Level Biology: Genes and the Genetic CodeA clear revision guide to genes and the genetic code for AQA A-Level Biology: the triplet code, its features, coding and non-coding DNA, and the genome, proteome and alleles.
AQA A-Level Biology: Protein Synthesis (Transcription and Translation)A clear revision guide to protein synthesis for AQA A-Level Biology: transcription, the splicing of pre-mRNA, and translation, including the roles of tRNA, ribosomes and ATP.
AQA A-Level Biology: Gene MutationsA clear revision guide to gene mutations for AQA A-Level Biology: substitution and deletion mutations, frameshifts, how they change proteins, and mutagenic agents.
AQA A-Level Biology: Meiosis and Genetic VariationA clear revision guide to meiosis for AQA A-Level Biology: how it halves the chromosome number, how crossing over and independent segregation create variation, and non-disjunction.
AQA A-Level Biology: Genetic Diversity and Natural SelectionA clear revision guide to genetic diversity and natural selection for AQA A-Level Biology: genetic bottlenecks, the founder effect, genetic drift, evolution and types of selection.
AQA A-Level Biology: Species and TaxonomyA clear revision guide to species and taxonomy for AQA A-Level Biology: defining a species, phylogenetic classification, binomial naming, and clarifying evolutionary relationships.
AQA A-Level Biology: Biodiversity and Investigating VariationA clear revision guide to biodiversity and variation for AQA A-Level Biology: the index of diversity, how farming affects biodiversity, measuring genetic diversity, and types of variation.
GCSE
Topic 1Cell Biology8 guides
AQA GCSE Biology: Cell StructureA clear GCSE Biology revision guide to cell structure: eukaryotic and prokaryotic cells, the sub-cellular structures in animal and plant cells, and orders of magnitude.
AQA GCSE Biology: Specialised Cells and DifferentiationA clear GCSE Biology revision guide to specialised cells and differentiation: how sperm, nerve, muscle, root hair, xylem and phloem cells are adapted, and how cells differentiate.
AQA GCSE Biology: MicroscopyA clear GCSE Biology revision guide to microscopy: magnification and resolution, light and electron microscopes, the magnification formula, and converting units.
AQA GCSE Biology: Culturing MicroorganismsA clear GCSE Biology revision guide to culturing microorganisms: binary fission, calculating bacterial population size, growing cultures, and aseptic technique.
AQA GCSE Biology: Chromosomes and the Cell CycleA clear GCSE Biology revision guide to chromosomes and the cell cycle: what chromosomes are, why mitosis matters, and the three stages of the cell cycle.
AQA GCSE Biology: Stem CellsA clear GCSE Biology revision guide to stem cells: embryonic and adult stem cells, therapeutic cloning, the medical uses and the issues, and stem cells in plants.
AQA GCSE Biology: Diffusion and Exchange SurfacesA clear GCSE Biology revision guide to diffusion and exchange surfaces: what diffusion is, what affects its rate, surface area to volume ratio, and how exchange surfaces are adapted.
AQA GCSE Biology: Osmosis and Active TransportA clear GCSE Biology revision guide to osmosis and active transport: how water moves across a partially permeable membrane, and how cells move substances against a concentration gradient.
Topic 2Organisation9 guides
AQA GCSE Biology: Principles of OrganisationA clear GCSE Biology revision guide to the principles of organisation: the levels from cells to organ systems, and the organs of the digestive system.
AQA GCSE Biology: Enzymes and DigestionA clear GCSE Biology revision guide to enzymes and digestion: the lock and key model, the digestive enzymes, bile, the effect of temperature and pH, and food tests.
AQA GCSE Biology: The Heart and Blood VesselsA clear GCSE Biology revision guide to the heart and blood vessels: the double circulatory system, the path of blood through the heart, the pacemaker, and arteries, veins and capillaries.
AQA GCSE Biology: BloodA clear GCSE Biology revision guide to blood: why blood is a tissue, and the roles of plasma, red blood cells, white blood cells and platelets.
AQA GCSE Biology: Coronary Heart DiseaseA clear GCSE Biology revision guide to coronary heart disease: its cause, how it leads to a heart attack, stents and statins, faulty heart valves, and heart failure.
AQA GCSE Biology: Health and Non-Communicable DiseaseA clear GCSE Biology revision guide to health and non-communicable disease: what health means, how diseases interact, risk factors, and correlation versus causation.
AQA GCSE Biology: CancerA clear GCSE Biology revision guide to cancer: how tumours form, the difference between benign and malignant tumours, and the risk factors for cancer.
AQA GCSE Biology: Plant TissuesA clear GCSE Biology revision guide to plant tissues: the structure of a leaf and the job of each tissue, and the detail of xylem and phloem.
AQA GCSE Biology: Plant TransportA clear GCSE Biology revision guide to transport in plants: transpiration and the transpiration stream, guard cells and stomata, the factors affecting transpiration, and translocation.
Topic 3Infection and Response7 guides
AQA GCSE Biology: Communicable DiseaseA clear GCSE Biology revision guide to communicable disease: what pathogens are, how bacteria and viruses make us ill, how diseases spread, and how spread can be reduced.
AQA GCSE Biology: Diseases Caused by PathogensA clear GCSE Biology revision guide to the diseases caused by pathogens: measles, HIV and TMV (viral), Salmonella and gonorrhoea (bacterial), rose black spot (fungal) and malaria (protist).
AQA GCSE Biology: Human Defence SystemsA clear GCSE Biology revision guide to human defence systems: the non-specific barriers that keep pathogens out, and how white blood cells destroy pathogens that get in.
AQA GCSE Biology: VaccinationA clear GCSE Biology revision guide to vaccination: how a vaccine makes you immune, how it reduces the spread of disease, and the antibody response after vaccination.
AQA GCSE Biology: Medicines and Drug DevelopmentA clear GCSE Biology revision guide to medicines and drug development: antibiotics and painkillers, antibiotic resistance, where drugs come from, and how new drugs are tested.
AQA GCSE Biology: Monoclonal AntibodiesA Higher tier GCSE Biology revision guide to monoclonal antibodies: what they are, how they are made using hybridoma cells, and their uses in diagnosis, research and treatment.
AQA GCSE Biology: Plant Disease and DefencesA Triple award GCSE Biology revision guide to plant disease and defences: causes of plant disease, mineral deficiencies, detecting and identifying disease, and physical, chemical and mechanical defences.
Topic 4Bioenergetics5 guides
AQA GCSE Biology: PhotosynthesisA clear GCSE Biology revision guide to photosynthesis: the reaction and its equations, why it is endothermic, and how plants use the glucose they make.
AQA GCSE Biology: Rate of PhotosynthesisA clear GCSE Biology revision guide to the rate of photosynthesis: limiting factors including temperature, light, carbon dioxide and chlorophyll, the inverse square law, and using limiting factors in farming.
AQA GCSE Biology: RespirationA clear GCSE Biology revision guide to respiration: aerobic and anaerobic respiration, their equations, how they compare, and fermentation in yeast.
AQA GCSE Biology: Response to ExerciseA clear GCSE Biology revision guide to the body's response to exercise: how heart and breathing rate change, anaerobic respiration and lactic acid, oxygen debt, and the role of the liver.
AQA GCSE Biology: MetabolismA clear GCSE Biology revision guide to metabolism: what metabolism means, and examples of reactions that build up and break down molecules in the body.
Topic 5Homeostasis and Response12 guides
AQA GCSE Biology: HomeostasisA clear GCSE Biology revision guide to homeostasis: what it is, why it matters, the conditions the body regulates, and the automatic control systems that keep them steady.
AQA GCSE Biology: The Nervous SystemA clear GCSE Biology revision guide to the nervous system: the CNS, neurones and synapses, the pathway from stimulus to response, and reflex actions.
AQA GCSE Biology: The BrainA Triple award GCSE Biology revision guide to the brain: the cerebral cortex, cerebellum and medulla, how brain function is mapped, and why the brain is hard to study and treat.
AQA GCSE Biology: The EyeA Triple award GCSE Biology revision guide to the eye: its structures, the pupil reflex, accommodation, and the correction of short and long sight.
AQA GCSE Biology: Control of Body TemperatureA Triple award GCSE Biology revision guide to the control of body temperature: the thermoregulatory centre, and the body's responses when it is too hot or too cold.
AQA GCSE Biology: The Endocrine SystemA clear GCSE Biology revision guide to the endocrine system: what hormones are, the main endocrine glands, why the pituitary is the master gland, and how it compares with the nervous system.
AQA GCSE Biology: Blood Glucose and DiabetesA clear GCSE Biology revision guide to blood glucose control and diabetes: the role of the pancreas, insulin and glucagon, and Type 1 and Type 2 diabetes.
AQA GCSE Biology: Water and Nitrogen BalanceA Triple award GCSE Biology revision guide to water and nitrogen balance: why balance matters, how the kidneys make urine, control by ADH, and treatments for kidney failure.
AQA GCSE Biology: Hormones in ReproductionA clear GCSE Biology revision guide to hormones in human reproduction: puberty, the main reproductive hormones, and the hormonal control of the menstrual cycle.
AQA GCSE Biology: Contraception and Fertility TreatmentA clear GCSE Biology revision guide to controlling fertility: hormonal and non-hormonal contraception, and fertility treatments including fertility drugs and IVF.
AQA GCSE Biology: Adrenaline, Thyroxine and Negative FeedbackA Higher tier GCSE Biology revision guide to adrenaline, thyroxine and negative feedback: what each hormone does, and how thyroxine is controlled by negative feedback.
AQA GCSE Biology: Plant HormonesA Triple award GCSE Biology revision guide to plant hormones: tropisms, how auxin controls phototropism and gravitropism, and the uses of auxins, ethene and gibberellins.
Topic 6Inheritance and Evolution12 guides
AQA GCSE Biology: Sexual and Asexual ReproductionA clear GCSE Biology revision guide to sexual and asexual reproduction: how each works, why sexual reproduction produces variation, and the advantages of each.
AQA GCSE Biology: MeiosisA clear GCSE Biology revision guide to meiosis: how it produces gametes, why it halves the chromosome number, and what happens after fertilisation.
AQA GCSE Biology: DNA and the GenomeA clear GCSE Biology revision guide to DNA and the genome: what DNA, genes and the genome are, the structure of DNA, how genes code for proteins, and mutations.
AQA GCSE Biology: Genetic InheritanceA clear GCSE Biology revision guide to genetic inheritance: the key genetic terms, and how to use Punnett squares to predict the outcome of a genetic cross.
AQA GCSE Biology: Inherited Disorders and Sex DeterminationA clear GCSE Biology revision guide to inherited disorders and sex determination: polydactyly, cystic fibrosis, embryo screening, and how the sex chromosomes determine sex.
AQA GCSE Biology: Variation and EvolutionA clear GCSE Biology revision guide to variation and evolution: the causes of variation, evolution by natural selection, and how new species form.
AQA GCSE Biology: Selective Breeding and Genetic EngineeringA clear GCSE Biology revision guide to selective breeding and genetic engineering: how humans breed organisms for chosen traits, how genes are transferred between organisms, and the concerns raised.
AQA GCSE Biology: CloningA Triple award GCSE Biology revision guide to cloning: plant cloning by cuttings and tissue culture, animal cloning by embryo transplant and adult cell cloning, and the risks.
AQA GCSE Biology: The Theory of Evolution and SpeciationA Triple award GCSE Biology revision guide to the theory of evolution and speciation: Darwin and Wallace, Lamarck, Mendel, and how new species form.
AQA GCSE Biology: Fossils and Evidence for EvolutionA clear GCSE Biology revision guide to the evidence for evolution: the main lines of evidence, how fossils form, and why the fossil record is incomplete.
AQA GCSE Biology: Extinction and Antibiotic ResistanceA clear GCSE Biology revision guide to extinction and antibiotic resistance: the causes of extinction, how antibiotic-resistant bacteria develop, and how to slow resistance.
AQA GCSE Biology: ClassificationA clear GCSE Biology revision guide to classification: the Linnaean system and binomial names, the three-domain system, and evolutionary trees.