Key term
AQA GCSE Biology 8461
Bioenergetics
Cell Biology
Topic overviewEukaryotes and prokaryotesAnimal and plant cellsCell specialisation and differentiationMicroscopyGrowing bacteria and aseptic techniqueCalculating bacterial growth, and testing antiseptics and antibioticsChromosomes, mitosis and the cell cycleStem cells in embryos, adults and meristemsTherapeutic cloning, its risks, and cloning plantsDiffusion and the factors affecting its rateSurface area to volume ratio and exchange surfacesOsmosisActive transport
Ecology
Topic overviewLevels of organisation in an ecosystem, and what organisms needCompetition, interdependence and stable communitiesAbiotic factorsBiotic factorsAdaptationsProducers, food chains and sampling with quadrats and transectsPredators, prey and measuring population sizeHow materials are cycledDecompositionWaste management and biodiversityLand use, deforestation and global warmingMaintaining biodiversityTrophic levels and pyramids of biomassTransfer of biomassFactors affecting food securityFarming techniques and sustainable fisheriesRole of biotechnologyImpact of environmental change
Homeostasis and Response
Topic overviewHomeostasisThe nervous system and the reflex arcThe structure of the eye and accommodationMyopia, hyperopia and how they are correctedThe brain and the control of body temperatureHuman endocrine systemInsulin, glucagon and diabetesWater and ion loss, and the production of ureaThe kidneys, ADH and treating kidney failureHormones in human reproductionContraceptionThe use of hormones to treat infertilityNegative feedbackPlant hormones and their uses
Infection and Response
Topic overviewCommunicable (infectious) diseasesViral diseasesBacterial diseasesFungal and protist diseasesHuman defence systemsVaccinationAntibiotics and painkillersDiscovery and development of drugsProducing monoclonal antibodiesUses of monoclonal antibodiesDetection and identification of plant diseasesPlant defence responses
Inheritance, Variation and Evolution
Topic overviewSexual and asexual reproductionMeiosisAdvantages and disadvantages of sexual and asexual reproductionDNA and the genomeDNA as a polymer of four nucleotidesProtein synthesis and complementary base pairingMutations, protein shape and non-coding DNAGenetic terms, dominant and recessive allelesPunnett squares, probability and genetic crossesInherited disorders and sex determinationVariationEvolutionSelective breedingWhat genetic engineering is, and what it is used forGM crops, their risks, and the steps of the processCloningDarwin, Lamarck and the acceptance of evolutionSpeciationThe understanding of geneticsEvidence for evolution, and extinctionFossilsResistant bacteriaClassification of living organisms
Organisation
Topic overviewLevels of organisation, and how enzymes workAmylase, proteases and lipasesBile, food tests and the effect of pH on amylaseThe heart, the lungs and double circulationThe pacemaker, the blood vessels and the bloodCoronary heart disease: a non-communicable diseaseHealth issuesRisk factors and causal mechanisms in diseaseSampling, correlation and interpreting risk dataCancerPlant tissues, and transpiration and its rateRoot hair cells, xylem, phloem and stomata
Infection and Response
Plant defence responses
- 3 things to know
- Paper 1
Overview
Physical defences of cellulose cell walls, waxy cuticles and layers of dead cells, chemical defences of antibacterial chemicals and poisons, and mechanical adaptations such as thorns, hairs, drooping leaves and mimicry.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Name the three physical defences that resist the invasion of microorganisms.
Key term
Name the two kinds of chemical defence produced by plants.
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is meant by a physical defence in a plant?
Model answer
A structure that acts as a barrier to stop microorganisms invading the plant.
- 2
Is a poison made in a leaf a physical or a chemical defence, and what is it for?
Model answer
It is a chemical defence, and it deters herbivores from eating the plant.
- 3
Name the three physical defences that resist the invasion of microorganisms.
Model answer
Cellulose cell walls, a tough waxy cuticle on the leaves, and layers of dead cells around the stems.
- 4
How does a cellulose cell wall help to defend a plant?
Model answer
It forms a tough layer around each cell that microorganisms find hard to penetrate.
- 5
Explain how the waxy cuticle of a leaf defends the plant.
Model answer
It covers the leaf surface with a tough waterproof layer, so microorganisms cannot easily reach the living cells beneath.
- 6
Explain how the layers of dead cells around the stem of a tree protect it.
Model answer
They form a barrier around the living tissue, and because they fall off they carry away any microorganisms growing on them.
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