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 biotechnology
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 reproductionContraceptionPlant hormones and their uses
Infection and Response
Inheritance, Variation and Evolution
Topic overviewSexual and asexual reproductionMeiosisAdvantages and disadvantages of sexual and asexual reproductionDNA and the genomeDNA as a polymer of four nucleotidesGenetic 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
Ecology
Decomposition
- 3 things to know
- Paper 2
Overview
How temperature, water and oxygen set the rate of decay, compost heaps and biogas generators, and the milk decay investigation with its pH and rate calculations.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Explain why the rate of decay slows again if the temperature rises well above the optimum.
Key term
Explain why biological material decays very slowly in a hot, dry desert.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Explain why waste decays faster at 30 °C than at 5 °C.
Model answer
The enzymes of the decomposers work faster at the warmer temperature, so the material is broken down more quickly.
- 2
Explain why the rate of decay slows again if the temperature rises well above the optimum.
Model answer
The enzymes of the decomposers are denatured, so they can no longer break the material down.
- 3
Explain why biological material decays very slowly in a hot, dry desert.
Model answer
Decomposers need water to grow and to release their enzymes, so with almost no water they are inactive.
- 4
Explain why waste decays slowly at the bottom of a tightly packed landfill site.
Model answer
There is very little oxygen there, so aerobic decomposers cannot respire quickly and decay is slow.
- 5
Name three conditions a gardener provides in a compost heap to speed up decay.
Model answer
Warmth, moisture and a good supply of oxygen from turning the heap.
- 6
Why is compost useful to a gardener or a farmer?
Model answer
It acts as a natural fertiliser, returning mineral ions to the soil for the plants or crops to absorb.
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