Process
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
Inheritance, Variation and Evolution
Meiosis
- 3 things to know
- Paper 2
Overview
How meiosis halves the chromosome number and fertilisation restores it, where it happens, copying then two divisions giving four different gametes, and mitosis in the growing embryo.
What you need to know
Answer each one before you reveal it.
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Key term
What is the first thing that happens in a cell that is about to divide to form gametes?
Key term
How many sets of chromosomes does each gamete contain?
Questions from this subtopic
Each one with the model answer underneath.
- 1
How does meiosis change the number of chromosomes in a cell?
Model answer
It halves the chromosome number, so each gamete has half the number found in a body cell.
- 2
How is the full number of chromosomes restored after gametes have been formed?
Model answer
Two gametes fuse at fertilisation, so their two half sets combine to give the full number.
- 3
A body cell of an organism contains 24 chromosomes. How many chromosomes will one of its gametes contain?
Model answer
12 chromosomes.
- 4
In which organs of the body does meiosis take place?
Model answer
In the reproductive organs.
- 5
What is the first thing that happens in a cell that is about to divide to form gametes?
Model answer
Copies of the genetic information are made.
- 6
How many times does a cell divide when it forms gametes, and how many gametes result?
Model answer
It divides twice and four gametes are formed.
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