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
Biotic factors
- 3 things to know
- Paper 2
Overview
Food availability, new predators, new pathogens and competition as biotic factors, with red and grey squirrels, poor acorn crops, island prey, lost plant species and diseased ash trees, and interpreting population data on introduced species and disease.
What you need to know
Answer each one before you reveal it.
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Key term
Explain how a new pathogen can change a community.
Key term
Explain how one species outcompeting another can end a population altogether.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Name four biotic factors that can affect a community.
Model answer
Availability of food, new predators arriving, new pathogens, and one species outcompeting another.
- 2
Why is the arrival of a new predator described as a biotic factor rather than an abiotic one?
Model answer
It is a change caused by another living organism rather than by a physical or chemical condition of the environment.
- 3
Explain how a new pathogen can change a community.
Model answer
Species with no resistance to it die in large numbers, and species that depended on them for food or shelter are affected too.
- 4
Explain how one species outcompeting another can end a population altogether.
Model answer
The losing species obtains too little food or space, so its numbers fall until too few individuals remain to breed.
- 5
Grey squirrels are introduced into a wood containing red squirrels. Explain what may happen to the red squirrel population.
Model answer
Grey squirrels compete for the same food and shelter and carry a disease the reds cannot resist, so red squirrel numbers fall.
- 6
A cold spring is followed by a very poor acorn crop. Explain the effect on the mice that feed on acorns.
Model answer
Less food is available, so more mice starve and the mouse population falls.
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