Key term
AQA GCSE Combined Science Biology 8464
Bioenergetics
Cell Biology
Topic overviewEukaryotes and prokaryotesAnimal and plant cellsCell specialisation and differentiationMicroscopyChromosomes, 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 cycledWaste management and biodiversityLand use, deforestation and global warmingMaintaining biodiversity
Homeostasis and Response
Infection and Response
Inheritance, Variation and Evolution
Topic overviewSexual and asexual reproductionMeiosisDNA and the genomeGenetic 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 processEvidence 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
Cell Biology
Surface area to volume ratio and exchange surfaces
- 3 things to know
- Biology Paper 1
Overview
Why single-celled organisms rely on their outer surface, surface area to volume ratios of cubes, why large organisms need exchange surfaces and transport systems, adaptations of the small intestine, lungs, gills, roots and leaves, and the features that make exchange effective.
What you need to know
Answer each one before you reveal it.
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Key term
What happens to the surface area to volume ratio of an organism as it gets larger?
Key term
A cube has sides of 1 cm. What is its surface area to volume ratio?
Questions from this subtopic
Each one with the model answer underneath.
- 1
Why can a single-celled organism rely on its outer surface alone for exchange?
Model answer
It has a relatively large surface area to volume ratio, so enough molecules can move in and out to meet its needs.
- 2
What happens to the surface area to volume ratio of an organism as it gets larger?
Model answer
The ratio gets smaller, because volume increases faster than surface area.
- 3
A cube has sides of 1 cm. What is its surface area to volume ratio?
Model answer
6 to 1, from a surface area of 6 cm² and a volume of 1 cm³.
- 4
A cube has sides of 2 cm. What is its surface area to volume ratio?
Model answer
3 to 1, from a surface area of 24 cm² and a volume of 8 cm³.
- 5
A cube has sides of 3 cm. What is its surface area to volume ratio?
Model answer
2 to 1, from a surface area of 54 cm² and a volume of 27 cm³.
- 6
Explain why a large multicellular organism needs specialised exchange surfaces.
Model answer
Its surface area to volume ratio is small, so its outer surface cannot take in and remove enough substances for all its cells.
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