Microscopy · cell structure
Magnification and image size
Calculate magnification, actual size and image size, then practise using a scale bar. Get new values, clues and worked solutions.
Practise this skillRead the method and examples17 study tools
Cell sizes · osmosis · measurements
Units and standard form
Practise mm, μm and nm conversions, standard form and percentage changes using biological measurements. Check each answer and see the working.
Practise this skillRead the method and examplesEnzymes · photosynthesis · practical data
Rates and graph gradients
Practise mean rates, reciprocal time and tangent gradients with enzyme and photosynthesis contexts. Use original labelled graphs and worked solutions.
Practise this skillRead the method and examplesInheritance · ecology · comparing treatments
Statistical tests and conclusions
Choose chi-squared, Spearman’s rank or a t-test for suitable data. Interpret supplied critical values, null hypotheses and statistical significance.
Practise this skillRead the method and examplesExchange surfaces · cell size
Surface area to volume ratio
Calculate surface area, volume and surface area to volume ratios for cubes and spheres. Practise rearranging a ratio into x:1.
Practise this skillRead the method and examplesGlucose standards · practical preparation
Dilutions and solution concentrations
Practise stock volumes, final concentrations and serial dilutions. Use C₁V₁ = C₂V₂ and keep track of the final volume.
Practise this skillRead the method and examplesReplicates · microscopy · data interpretation
Averages, spread and mitotic index
Calculate means, medians, ranges and mitotic index. Interpret supplied standard deviations, with sample standard-deviation calculation in OCR mode.
Practise this skillRead the method and examplesApparatus readings · practical evaluation
Measurement uncertainty
Convert a supplied absolute uncertainty into a percentage and combine uncertainties for the difference between two readings.
Practise this skillRead the method and examplesQuadrats · population estimates
Ecological sampling calculations
Estimate abundance from quadrats, calculate species frequency and use a simple mark–release–recapture estimate with its assumptions stated.
Practise this skillRead the method and examplesSpecies counts · richness and evenness
Biodiversity index calculations
Calculate biodiversity indices from original species-count data, using the stated AQA or OCR formula. Compare values calculated with the same formula.
Practise this skillRead the method and examplesEcosystems · trophic levels
Energy transfers and productivity
Calculate net primary production, consumer production, transfer efficiency and production per unit area from biological energy budgets.
Practise this skillRead the method and examplesGas exchange · respirometer data
Respiration measurements and RQ
Calculate respiratory quotient, volume changes in a capillary and respiration rates per gram from supplied measurements and assumptions.
Practise this skillRead the method and examplesGenetic diagrams · independent outcomes
Inheritance probabilities and genetic ratios
Use Punnett tables, independent dihybrid probabilities, sex-linked reference groups and expected phenotype counts. Each question states its genetic assumptions.
Practise this skillRead the method and examplesAlleles · genotype frequencies · populations
Hardy–Weinberg calculations
Calculate allele frequencies, heterozygote frequencies and expected genotype counts from a stated two-allele Hardy–Weinberg model.
Practise this skillRead the method and examplesObserved counts · expected ratios · goodness of fit
Chi-squared calculations
Calculate chi-squared contributions and total goodness-of-fit statistics from original count tables, then choose degrees of freedom for a fully specified ratio.
Practise this skillRead the method and examplesPigment separation · distances · ratios
Chromatography and Rf calculations
Calculate Rf, pigment spot distance and solvent-front distance. Use matching units and distances measured from the same origin.
Practise this skillRead the method and examplesMicrobial growth · doubling time · logarithmic axes
Exponential growth and logarithmic scales
Calculate populations, generations and doubling times. Read base-ten logarithmic scales and explain why exponential growth can appear as a straight line.
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