Key term
AQA A-Level Biology 7402
Biological Molecules
Topic overviewMonomers, polymers, condensation and hydrolysisMonosaccharides, disaccharides and glycosidic bondsAlpha and beta glucose, amylose and amylopectinHow starch, glycogen and cellulose suit their functionsCellulose microfibrils and tests for sugars and starchTriglycerides, fatty acids and phospholipid structureProperties of lipids and the emulsion testThe general structure of amino acidsPeptide bonds, polypeptides and bonds in proteinsLevels of protein structure, the biuret test and chromatographyActivation energy, induced fit and enzyme specificityEnzyme and substrate concentration and inhibitionpH, temperature, initial rates and measurement uncertaintyDNA, RNA and the components of a nucleotideBase pairing in DNA and RNAPhosphodiester bonds and the DNA double helixDoubts about DNA, base ratios and RNA structureSemi-conservative replication, helicase and DNA polymeraseSteps of replication and the Meselson-Stahl experimentATP structure, hydrolysis and resynthesisWater as a metabolite, solvent and coolantHydrogen, iron, sodium and phosphate ions
Cells
Topic overviewCell-surface membrane, nucleus and mitochondriaChloroplasts, Golgi apparatus and lysosomesRibosomes, endoplasmic reticulum, cell walls and vacuolesCell specialisation, levels of organisation and organelle rolesProkaryotic cell structure and virus particlesOptical and transmission electron microscopesScanning electron microscopes, magnification and graticulesCell fractionation, homogenisation and ultracentrifugationOrder of sedimentation, artefacts and fractionation conditionsThe cell cycle, interphase and the stages of mitosisSpindle fibres, cytokinesis and uncontrolled cell divisionBinary fission, viral replication and root tip squashesMitotic index, mitosis stages and size calculationsThe fluid-mosaic model and cholesterolSimple diffusion, facilitated diffusion and membrane proteinsOsmosis, water potential and active transportCo-transport in the ileum and adaptations for rapid transportTransport rates, dilution series and membrane permeabilityAntigens, cell recognition and phagocytosisAntigen-presenting cells, T cells and clonal selectionAntibody structure, agglutination and antigen-antibody complexesMemory cells, vaccination and active and passive immunityHIV structure and replicationAIDS, monoclonal antibodies, ELISA and clinical trials
Organisms Exchange Substances with Their Environment
Topic overviewSurface area to volume ratio, metabolic rate and calculationsGas exchange in single-celled organisms, insects and fishLeaf gas exchange, insect water loss and xerophytesTrachea, bronchi, alveoli and lung dissectionInspiration, expiration and pulmonary ventilation rateLung disease, correlation, insect tracheae and Spearman's rankDigestion of carbohydrates and lipidsEndopeptidases, exopeptidases and dipeptidasesCo-transport of amino acids, micelles and chylomicronsHaemoglobin, red blood cells and the dissociation curveCooperative binding, the Bohr effect and different haemoglobinsDouble circulation and the major blood vesselsHeart chambers, the cardiac cycle and heart dissectionArteries, arterioles, veins and capillariesTissue fluid, cardiovascular risk factors and semilunar valvesXylem structure and the cohesion-tension theoryPhloem structure, companion cells and translocationMass flow from source to sink, tracers and ringingEvaluating mass flow, potometers and transpiration rate
Genetic Information, Variation and Relationships Between Organisms
Topic overviewProkaryotic and eukaryotic DNA, chromosomes and histonesDNA in mitochondria and chloroplasts, genes and lociFeatures of the genetic code, exons and intronsGenome, proteome, mRNA and tRNATranscription, RNA polymerase and splicingTranslation at the ribosome and the role of tRNAGene mutations, mutagens and chromosome non-disjunctionMeiosis, independent segregation and crossing overMeiosis compared with mitosis and random fertilisationGenetic diversity and the spread of advantageous allelesDirectional and stabilising selectionDefining adaptations and how antibiotic resistance spreadsSelection on birth weight, aseptic technique and antimicrobialsClassifying anatomical, physiological and behavioural adaptationsDefining a species, courtship and phylogenetic classificationThe taxonomic hierarchy, binomial names and molecular evidenceSpecies richness, the index of diversity and farmingComparing genetic diversity, standard deviation and the t-test
Energy Transfers in and Between Organisms
Topic overviewPhotoionisation and ATP from the light-dependent reactionChemiosmosis, photolysis and products for the Calvin cycleCarbon fixation, triose phosphate and limiting factorsGlasshouse conditions, pigment chromatography and DCPIPGlycolysis and its productsAnaerobic respiration and the oxidation of pyruvateAcetylcoenzyme A and the Krebs cycleOxidative phosphorylation, other substrates and respirometersBiomass and gross and net primary productionNet production of consumers and productivityFarming practices, transfer efficiency and the production equationsSaprobionts and the phosphorus cycleMycorrhizae, ammonification and nitrificationNitrogen fixation, denitrification and fertilisersLeaching, eutrophication and nutrient cycles reviewed
Organisms Respond to Changes in Their Internal and External Environments
Topic overviewIAA, gravitropism and phototropismTaxes, kineses, reflex arcs and choice chambersThe Pacinian corpuscle and generator potentialsRods, cones, colour vision and visual acuityThe SAN, AVN, bundle of His and Purkyne tissueChemoreceptors, baroreceptors and cardiac outputMotor neurone structure and the resting potentialDepolarisation, action potentials and saltatory conductionThe refractory period and speed of conductionSynapse structure and the neuromuscular junctionTransmission at a cholinergic synapseAcetylcholinesterase, summation and inhibitory synapsesNeuromuscular junctions compared, agonists and antagonistsDrug effects and potassium channels in hyperpolarisationAntagonistic muscle pairs and muscle fibre structureSarcomere bands, actin, myosin and tropomyosinThe sliding filament cycle, ATP and phosphocreatineSlow twitch and fast twitch muscle fibresControl systems and why temperature, pH and glucose matterNegative and positive feedbackGlycogenesis, glycogenolysis and gluconeogenesisHow insulin, glucagon and adrenaline actThe second messenger model, diabetes and the sugar debateGlucose calibration curves and hormones affecting blood glucoseOsmoregulation, osmoreceptors and ADHNephron structure and ultrafiltrationThe proximal convoluted tubule and the loop of HenleThe distal tubule, collecting duct and urine concentration
Genetics, Populations, Evolution and Ecosystems
Topic overviewGenotype, phenotype and types of alleleMonohybrid and dihybrid crosses, sex linkage and autosomal linkageEpistasis, genetic diagrams and the chi-squared testGene pools, allele frequency and Hardy–WeinbergSources of variation and selection pressuresTypes of selection and allopatric and sympatric speciationGenetic drift, founder effects and the route to speciationCommunities, ecosystems, niches and carrying capacityCompetition, predation, quadrats and mark-release-recaptureMark-release-recapture assumptions and successionSuccession, conservation and evaluating the evidence
The Control of Gene Expression
Topic overviewTypes of gene mutation and mutagenic agentsSilent, frameshift, missense and nonsense mutationsTotipotent, pluripotent and induced pluripotent stem cellsTranscription factors, oestrogen, epigenetics and twin studiesDNA methylation, histone acetylation and cancerRNA interference and epigenetic drug targetsBenign and malignant tumours, suppressor genes and oncogenesAbnormal methylation, oestrogen and evidence on causes of cancerGenome projects, the proteome and sequencing methodsTransgenic organisms and making DNA fragmentsThe polymerase chain reactionPromoters, restriction endonucleases, sticky ends and ligaseTransformation, marker genes and uses of recombinant DNAThe humanitarian debate, cDNA and in vivo cloningDNA probes, hybridisation and screening for allelesGenetic counselling, personalised medicine and screening ethicsVNTRs, PCR and gel electrophoresisUsing and interpreting genetic fingerprints
Genetics, Populations, Evolution and Ecosystems
- 11 subtopics
- 33 things to know
- Papers 2 and 3
What Genetics, Populations, Evolution and Ecosystems covers
Genetics, Populations, Evolution and Ecosystems is examined on Paper 2 of AQA Biology, which covers topics 5 to 8, and on Paper 3, which can draw on any topic. 144 recall questions across 11 subtopics.
Where it is assessed
Papers 2 and 3
Topics 5 to 8, then the synoptic paper.
Check the AQA specification ↗The 11 subtopics
Each one has its own page.
- Genotype, phenotype and types of alleleRecall questions on genotype and phenotype, multiple alleles, dominant, recessive and codominant alleles, homozygous and heterozygous, and the locus of a gene.Open →
- Monohybrid and dihybrid crosses, sex linkage and autosomal linkageRecall questions on monohybrid and dihybrid crosses and their expected ratios, why X-linked recessive conditions are commoner in males, autosomal linkage, and multiple alleles.Open →
- Epistasis, genetic diagrams and the chi-squared testRecall questions on epistasis and its ratios, setting out a genetic diagram with gametes and a Punnett square, using the chi-squared test on crosses, and the probability of inheriting alleles.Open →
- Gene pools, allele frequency and Hardy–WeinbergRecall questions on populations, gene pools and allele frequency, the conditions for the Hardy–Weinberg principle, and using its equations to find allele, genotype and carrier frequencies.Open →
- Sources of variation and selection pressuresRecall questions on how mutation, independent assortment, crossing over and random fertilisation cause genetic variation, and how predation, disease and competition act as selection pressures.Open →
- Types of selection and allopatric and sympatric speciationRecall questions on how differential reproductive success changes allele frequencies, stabilising, directional and disruptive selection, reproductive isolation, and allopatric and sympatric speciation.Open →
- Genetic drift, founder effects and the route to speciationRecall questions on genetic drift and why it matters in small populations, the founder and bottleneck effects, and how natural selection and reproductive isolation together lead to new species.Open →
- Communities, ecosystems, niches and carrying capacityRecall questions on communities and ecosystems of different sizes, the niche and the abiotic and biotic factors that govern it, carrying capacity, and abiotic factors that affect population size.Open →
- Competition, predation, quadrats and mark-release-recaptureRecall questions on interspecific and intraspecific competition and predation, estimating population size with quadrats and belt transects, and the Lincoln index for mark-release-recapture.Open →
- Mark-release-recapture assumptions and successionRecall questions on the assumptions behind mark-release-recapture estimates, ecosystems as dynamic, and primary succession from pioneer species to a climax community.Open →
- Succession, conservation and evaluating the evidenceRecall questions on how succession changes the environment and biodiversity, managing succession to conserve habitats, measuring abundance, and judging evidence on conservation such as the badger culling trial.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Process
How does genetic drift differ from natural selection, and what allows speciation?
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What is a gene pool, and what does the Hardy-Weinberg principle assume?
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What is meant by the term genotype?
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What is a monohybrid cross?
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Define dihybrid cross.
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Give two examples of phenotypic ratios that can result from epistasis in a dihybrid cross.
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Why must gametes be shown separately in a genetic diagram?
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Can a single species exist as more than one population, or must it always form a single continuous group?
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How do genetic factors contribute to phenotypic variation within a population?
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What is the primary source of genetic variation in a population?
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What causes changes in allele frequencies within a gene pool over generations?
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Define the term gene pool.
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Define genetic drift.
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Define an ecosystem.
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Give one example of a very small ecosystem and one example of a very large ecosystem.
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What is interspecific competition?
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What is intraspecific competition?
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What would happen to the population estimate if marks rubbed off between sampling occasions?
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What assumption about capture probability must be met for mark-release-recapture to be valid?
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Why do some species decline during succession even though they helped establish the community?
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Explain why biodiversity typically increases during succession.
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Define phenotype.
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Why are X-linked recessive conditions more frequently observed in males than females?
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What tool is used in a genetic diagram to show all possible combinations of gametes?
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What is meant by the gene pool of a population?
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How does independent assortment during meiosis generate genetic variation?
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What is directional selection?
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Why does genetic drift have a more significant effect in small populations?
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What is meant by the term 'niche' in ecology?
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Explain how predation affects prey population size.
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Define primary succession.
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What conflict must be managed to achieve sustainability of natural resources?
Take Genetics, Populations, Evolution and Ecosystems further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Allopatric speciation vs Sympatric speciation
Allopatric speciation: the formation of a new species after a population is divided by a geographical barrier. Sympatric speciation: the formation of a new species within one population sharing the same area.
Genetic drift vs Genetic drift
Genetic drift: a change in allele frequency caused by chance rather than by selection, greatest in a small population. Genetic drift: a change in allele frequency caused by chance rather than by selection, greatest in a small population.
Genotype vs Phenotype
Genotype: the genetic constitution of an organism. Phenotype: the observable characteristics produced by genes and environment.
Questions from this topic
Each one with the model answer underneath.
- 1
What is meant by the term genotype?
Model answer
The genetic constitution of an organism.
- 2
Define phenotype.
Model answer
The expression of the genetic constitution and its interaction with the environment.
- 3
Is a single gene limited to only two alleles?
Model answer
No, a single gene may have many alleles.
- 4
What is a dominant allele?
Model answer
An allele that is expressed in the phenotype when present in either homozygous or heterozygous form.
- 5
Under what condition is a recessive allele expressed in the phenotype?
Model answer
Only when present in homozygous form.
- 6
What are codominant alleles?
Model answer
Alleles that are both expressed in the phenotype when present together in a heterozygote.
What is inside Levo
Six ways to work the same material.
Genetics, Populations, Evolution and Ecosystems revision questions
- What does Genetics, Populations, Evolution and Ecosystems cover in AQA A-Level Biology?
- 11 subtopics: genotype, phenotype and types of allele, monohybrid and dihybrid crosses, sex linkage and autosomal linkage, epistasis, genetic diagrams and the chi-squared test, gene pools, allele frequency and hardy–weinberg, sources of variation and selection pressures, types of selection and allopatric and sympatric speciation, genetic drift, founder effects and the route to speciation, communities, ecosystems, niches and carrying capacity, competition, predation, quadrats and mark-release-recapture, mark-release-recapture assumptions and succession and succession, conservation and evaluating the evidence. Each one has its own page with questions and model answers.
- How is Genetics, Populations, Evolution and Ecosystems organised?
- By the AQA 7402 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Genetics, Populations, Evolution and Ecosystems, on a schedule.
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