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
Transfer of biomass
- 2 things to know
- Paper 2
Overview
The shape of a pyramid of biomass, the 1% of light used in photosynthesis, the 10% passed between trophic levels, where biomass is lost, and efficiency calculations.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Numbers
A field of grass contains 20 000 kg of biomass. Estimate the biomass of the cattle that this grass supports.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Describe the usual shape of a pyramid of biomass and explain why it has that shape.
Model answer
It is widest at the bottom and narrows towards the top, because biomass is lost at every transfer between trophic levels.
- 2
About what percentage of the light energy falling on plants and algae is transferred for photosynthesis?
Model answer
About 1 %.
- 3
Suggest why so little of the light falling on a leaf is transferred for photosynthesis.
Model answer
Much of the light is reflected, passes straight through the leaf, misses the chloroplasts, or is of a wavelength that is not absorbed.
- 4
Approximately what percentage of the biomass at one trophic level is transferred to the level above it?
Model answer
About 10 %.
- 5
A field of grass contains 20 000 kg of biomass. Estimate the biomass of the cattle that this grass supports.
Model answer
About 10 % of 20 000 kg is transferred, which is 2000 kg.
- 6
Name the two main ways in which biomass is lost between one trophic level and the next.
Model answer
Some ingested material is not absorbed and is egested as faeces, and some absorbed material is lost as waste products.
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