Key term
Edexcel GCSE Combined Science Biology 1SC0
Key Concepts in Biology
Topic overviewEukaryotic and prokaryotic cellsSpecialised cells and their adaptationsMicroscopes and magnification calculationsSize, scale and units in cell biologyEnzyme action and denaturationFactors affecting enzyme activityEnzymes in synthesis and digestion, and rate calculationsDiffusion, osmosis and active transportOsmosis in potatoes and percentage change in mass
Cells and Control
Genetics
Topic overviewMeiosis and the formation of gametesDNA structure, genes and the genomeExtracting DNA from fruitAlleles, genotype and phenotypeMonohybrid crosses and sex determinationProbability and ratios from genetic crossesCauses of variation: genes and environmentThe Human Genome ProjectGenetic variation and the effects of mutation
Natural Selection and Genetic Modification
Health, Disease and the Development of Medicines
Topic overviewHealth, disease and susceptibilityPathogens and common infectionsHow pathogens spread, and the virus life cycleSexually transmitted infectionsPhysical barriers and chemical defencesThe immune system, immunisation and herd immunityAntibiotics and developing new medicinesLifestyle factors and non-communicable diseaseTreatments for cardiovascular disease
Plant Structures and Their Functions
Animal Coordination, Control and Homeostasis
Exchange and Transport in Animals
Topic overviewWhy multicellular organisms need exchange surfacesAlveoli and gas exchangeThe blood and its componentsArteries, veins and capillariesThe heart and the circulatory systemCellular respiration as an exothermic reactionAerobic and anaerobic respiration comparedInvestigating the rate of respirationCardiac output, stroke volume and heart rate
Ecosystems and Material Cycles
Ecosystems and Material Cycles
Estimating population size from field data
- 3 things to know
- Paper 2
Overview
Scaling a quadrat mean up to a whole site, working the mean per square metre from quadrats of different sizes, why the result is only an estimate, and transect counts.
What you need to know
Answer each one before you reveal it.
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Key term
Ten quadrats of 1 m² placed in a 500 m² field contain 45 dandelions in total. Estimate the number of dandelions in the field.
Numbers
Twenty quadrats, each of area 0.25 m², contain 60 buttercup plants altogether. Calculate the mean number of buttercups per square metre.
Questions from this subtopic
Each one with the model answer underneath.
- 1
State the rule used to estimate the total number of plants in an area from quadrat data.
Model answer
Multiply the mean number of plants per square metre by the total area of the site in square metres.
- 2
Ten quadrats of 1 m² placed in a 500 m² field contain 45 dandelions in total. Estimate the number of dandelions in the field.
Model answer
The mean is 4.5 per m², so the estimate is 4.5 × 500 = 2250 dandelions.
- 3
Twenty quadrats, each of area 0.25 m², contain 60 buttercup plants altogether. Calculate the mean number of buttercups per square metre.
Model answer
The quadrats cover 20 × 0.25 = 5 m², so the mean is 60 ÷ 5 = 12 buttercups per m².
- 4
A meadow measures 40 m by 25 m and quadrat sampling gives a mean of 3 clover plants per square metre. Estimate the clover population of the meadow.
Model answer
The meadow covers 1000 m², so the estimate is 3 × 1000 = 3000 clover plants.
- 5
Five quadrats, each 0.5 m by 0.5 m, on a 200 m² lawn contain 2, 4, 3, 5 and 6 plantains. Estimate the number of plantains on the lawn.
Model answer
The mean is 4 per quadrat, which is 16 per m², so the estimate is 16 × 200 = 3200 plantains.
- 6
Explain why a population size worked out from quadrat data is only an estimate.
Model answer
Only a small fraction of the area is actually counted, and that sample may not exactly match the whole site.
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