SubjectScout
ENAR
Sign inGet matched
Get matched

Cambridge practical and extended reasoning

Start questions

AI-assisted English content review; independent teacher approval pending.

Practice scope and review

Original, AI-authored English practice with worked guidance. Selected topics only; independent teacher review is pending. This is not a complete syllabus, official past-paper collection or predicted exam score. Check your own exam-board specification: these concepts are not certified against a particular board or exam year.

92 original questions across 17 selected topic areas. No account or payment required to practise.

Cambridge International AS & A Level Biology (9700), examination year 2027: AI-assisted conceptual alignment to official sources, not teacher or exam-board certification. Syllabus mapping and remaining coverage.

4 questions in this topic

This is a limited practice preview and is not submitted for search indexing.

All topics

Original multi-stage supplied-data practice. Partial written support only, not complete syllabus coverage, official results or practical certification.

Subtopics in this topic (4)
  • Osmotic change and a bounded zero crossing
  • Endpoint rates, controls and interval resolution
  • Sampling density and confounded comparisons
  • Calibration, resolution and biological inference

4 of 4 questions shown

Loading saved responses

Question 1Fictional potato-group mean masses are: concentration / mol/dm^3 0.20: initial 2.00 g, final 2.12 g; 0.30: 2.00 g, 2.04 g; 0.40: 2.00 g, 1.96 g. Calculate percentage changes and estimate zero mass change by local linear interpolation. Explain the water-potential inference and its limitations. Design written controls, independent replication and a display that would test this estimate; no plant cutting or soaking is requested. Give a connected worked response with calculations, justified conclusions and limitations. All datasets are original fictional practice, not official experiment results. Written/supplied-data work only; any actual laboratory or field activity requires teacher approval, risk assessment and supervision. No human trials. Primary reading: https://www.cambridgeinternational.org/Images/664560-2025-2027-syllabus.pdf5 indicative marks
Calculate, analyse and evaluate5 indicative marksCalculator allowed

Fictional potato-group mean masses are: concentration / mol/dm^3 0.20: initial 2.00 g, final 2.12 g; 0.30: 2.00 g, 2.04 g; 0.40: 2.00 g, 1.96 g. Calculate percentage changes and estimate zero mass change by local linear interpolation. Explain the water-potential inference and its limitations. Design written controls, independent replication and a display that would test this estimate; no plant cutting or soaking is requested. Give a connected worked response with calculations, justified conclusions and limitations. All datasets are original fictional practice, not official experiment results. Written/supplied-data work only; any actual laboratory or field activity requires teacher approval, risk assessment and supervision. No human trials. Primary reading: https://www.cambridgeinternational.org/Images/664560-2025-2027-syllabus.pdf

Cambridge 2027: Partial conceptual match

Osmotic change and a bounded zero crossing: selected written evidence only. Signed percentages and linear zero crossing independently checked; ratios of means, water potential and replication qualifications retained. Science practical-N and computing rN rows are internal identifiers, not official numbered leaf syllabus codes. Aggregate rows are only partially supported. Actual apparatus use, candidate coding execution and practical attainment are not demonstrated here. Independent teacher review remains required.

AI-assisted placement. Independent teacher approval pending.

Show indicative guidance

Worked guidance

  1. For each group use 100(final - initial)/initial: 100(0.12/2.00)=6.0%, 100(0.04/2.00)=2.0%, and 100(-0.04/2.00)=-2.0%. The zero lies halfway between the latter two concentrations: 0.30 + (2/(2 - (-2))) x 0.10 = 0.350 mol/dm^3. More decimal places would imply unsupported precision.
  2. Plot concentration horizontally and percentage mass change vertically, with individual observations and clearly defined variation bars when available. The supplied ratios of group means need not equal the mean of individual percentage changes when initial masses differ; the underlying paired records are needed for that analysis.
  3. Net mass can be altered by surface liquid, incomplete equilibration or solute leakage, so the zero is a conditional water-potential estimate, not a direct assay of intracellular sucrose. Standardise blotting without squeezing tissue, use independent tubers as biological replicates and balance pieces from each tuber across treatments. Add concentrations near the crossing and report uncertainty rather than declaring an exact isotonic value. SAPS provides the teaching context; every mass here is invented. Actual preparation needs school risk assessment and supervised cutting, not home trials.

Self-marking points

View marking points
  1. Changes are +6.0%, +2.0% and -2.0% relative to initial mass.
  2. The interpolated zero is 0.350 mol/dm^3, sensibly about 0.35.
  3. At zero net change the bathing solution and tissue have approximately matching water potentials under equilibration assumptions, not necessarily matching solute concentrations.
  4. Use individual paired percentage changes, independent tubers and clear biological replication; group means alone supply no uncertainty.
  5. Standardise tissue geometry, timing, temperature and blotting; teacher approval and supervised handling are required for actual work.

Examiner tip

Indicative original worked practice, independent teacher approval pending. Explain assumptions and alternatives; do not equate a correct written answer with observed practical performance.

Question 2Fictional independent enzyme-tube endpoint times are pH 6: 48, 50, 52 s; pH 7: 28, 30, 32 s. Treat reciprocal endpoint time as a rate proxy only when initial substrate amount and detection threshold are identical. Calculate the mean of individual reciprocal times at each pH and their ratio. Endpoint checks occur every 2 s. Design matched controls and explain why neither an exact optimum nor irreversible denaturation follows. Use supplied data only, no saliva, human material or other trials. Give a connected worked response with calculations, justified conclusions and limitations. All datasets are original fictional practice, not official experiment results. Written/supplied-data work only; any actual laboratory or field activity requires teacher approval, risk assessment and supervision. No human trials. Primary reading: https://www.cambridgeinternational.org/Images/664560-2025-2027-syllabus.pdf5 indicative marks
Calculate, analyse and evaluate5 indicative marksCalculator allowed

Fictional independent enzyme-tube endpoint times are pH 6: 48, 50, 52 s; pH 7: 28, 30, 32 s. Treat reciprocal endpoint time as a rate proxy only when initial substrate amount and detection threshold are identical. Calculate the mean of individual reciprocal times at each pH and their ratio. Endpoint checks occur every 2 s. Design matched controls and explain why neither an exact optimum nor irreversible denaturation follows. Use supplied data only, no saliva, human material or other trials. Give a connected worked response with calculations, justified conclusions and limitations. All datasets are original fictional practice, not official experiment results. Written/supplied-data work only; any actual laboratory or field activity requires teacher approval, risk assessment and supervision. No human trials. Primary reading: https://www.cambridgeinternational.org/Images/664560-2025-2027-syllabus.pdf

Cambridge 2027: Partial conceptual match

Endpoint rates, controls and interval resolution: selected written evidence only. Individual reciprocals, their means and ratio recomputed; censoring, proxy units and bounded mechanistic conclusion checked. Science practical-N and computing rN rows are internal identifiers, not official numbered leaf syllabus codes. Aggregate rows are only partially supported. Actual apparatus use, candidate coding execution and practical attainment are not demonstrated here. Independent teacher review remains required.

AI-assisted placement. Independent teacher approval pending.

Show indicative guidance

Worked guidance

  1. Calculate each tube's proxy before averaging: (1/48 + 1/50 + 1/52)/3 = 0.0200214 s^-1 and (1/28 + 1/30 + 1/32)/3 = 0.0334325 s^-1. Dividing gives 1.66984. Reciprocal mean times would instead be 0.0200 and 0.0333333 s^-1; the distinction matters when spread is larger.
  2. A check every 2 s only brackets disappearance; for an endpoint reported at 30 s, it lies after the 28 s check and by the 30 s check, subject to detection reliability. A higher-frequency measurement may narrow that bracket but does not fix an inconsistent threshold or mixing delay. Do not label these proxies substrate amount consumed per second without a calibrated conversion.
  3. In a written plan use matched buffers and verify final pH, hold temperature and final concentrations fixed, randomise independent tubes, and include no-enzyme and appropriate reagent blanks to test background change. More pH settings around the faster condition are required to locate a possible optimum; a recovery comparison after returning to common pH could distinguish reversible inhibition from lasting activity loss. Any actual assay requires teacher-approved non-human materials and supervision; these records justify only a conditional faster proxy at pH 7.

Self-marking points

View marking points
  1. Mean reciprocal times are 0.02002 s−1s^{-1} at pH 6 and 0.03343 s−1s^{-1} at pH 7.
  2. The ratio pH7/pH6 is 1.670, approximately 1.67.
  3. Mean(1/t) is not generally 1/mean(t); the proxy is not automatically mol/s.
  4. The true endpoint is interval-censored between the last positive check and first negative one, not timed exactly.
  5. Keep temperature, substrate/enzyme amounts, final volume and detection constant; two pH values cannot locate the optimum or prove denaturation.

Examiner tip

Indicative original worked practice, independent teacher approval pending. Explain assumptions and alternatives; do not equate a correct written answer with observed practical performance.

Question 3Supplied fictional counts in four 0.25 m^2 quadrats at each site are A: 2, 4, 6, 8 and B: 5, 7, 9, 11. Calculate mean counts, sample SD using n-1, and densities per m^2. A is shaded and ungrazed; B is sunny and grazed. Evaluate 'sunlight caused the difference'. Propose unbiased sampling and an appropriate conditional means comparison, stating null hypothesis, independence assumptions and why quadrats are not replicated sites. No fieldwork or organism manipulation is requested. Give a connected worked response with calculations, justified conclusions and limitations. All datasets are original fictional practice, not official experiment results. Written/supplied-data work only; any actual laboratory or field activity requires teacher approval, risk assessment and supervision. No human trials. Primary reading: https://www.cambridgeinternational.org/Images/664560-2025-2027-syllabus.pdf5 indicative marks
Calculate, analyse and evaluate5 indicative marksCalculator allowed

Supplied fictional counts in four 0.25 m^2 quadrats at each site are A: 2, 4, 6, 8 and B: 5, 7, 9, 11. Calculate mean counts, sample SD using n-1, and densities per m^2. A is shaded and ungrazed; B is sunny and grazed. Evaluate 'sunlight caused the difference'. Propose unbiased sampling and an appropriate conditional means comparison, stating null hypothesis, independence assumptions and why quadrats are not replicated sites. No fieldwork or organism manipulation is requested. Give a connected worked response with calculations, justified conclusions and limitations. All datasets are original fictional practice, not official experiment results. Written/supplied-data work only; any actual laboratory or field activity requires teacher approval, risk assessment and supervision. No human trials. Primary reading: https://www.cambridgeinternational.org/Images/664560-2025-2027-syllabus.pdf

Cambridge 2027: Partial conceptual match

Sampling density and confounded comparisons: selected written evidence only. Means, sample SD, area scaling and percentage difference checked independently; site-level pseudoreplication and causal confounding explicit. Science practical-N and computing rN rows are internal identifiers, not official numbered leaf syllabus codes. Aggregate rows are only partially supported. Actual apparatus use, candidate coding execution and practical attainment are not demonstrated here. Independent teacher review remains required.

AI-assisted placement. Independent teacher approval pending.

Show indicative guidance

Worked guidance

  1. Sum A to 20 and B to 32, then divide each by four. Each squared-deviation sum is 9 + 1 + 1 + 9 = 20, so s = sqrt(20/3) = 2.58199 counts per quadrat. Divide counts and SD by 0.25 m2m^{2}, giving 20 and 32 organisms/m2m^{2} with SD about 10.3 organisms/m2m^{2}.
  2. The difference is 32 - 20 = 12 organisms/m^2, or 100(32 - 20)/20 = 60%. Grazing, soil and site history also differ; multiple quadrats within one site do not create independent replicated sunlight treatments. Plot all counts by site and label SD rather than calling it a confidence interval.
  3. Specify random coordinates over a defined sampling frame, a consistent boundary rule and additional independent sites spanning crossed light/grazing conditions. A two-sample means test could test equal population mean quadrat counts if random independent sampling and appropriate distribution assumptions were defensible; these small potentially spatially dependent counts do not establish them. Even a valid site comparison would not identify sunlight as cause. Any field access or handling needs school approval and ecological protection, not intervention based on this task.

Self-marking points

View marking points
  1. Mean counts are 5 and 8 per quadrat; densities are 20 and 32 organisms/m^2.
  2. Both sample SDs are sqrt(20/3) = 2.58 organisms per quadrat, or 10.3 organisms/m2m^{2} after scaling.
  3. Observed density difference is 12 organisms/m^2, 60% relative to A; no causal attribution is established.
  4. Random coordinates and consistent counting rules reduce placement bias; spatial dependence and one site per condition limit inference.
  5. An independent means test is conditional on suitable independent samples and distribution assumptions; no invented p-value can overcome site-level confounding.

Examiner tip

Indicative original worked practice, independent teacher approval pending. Explain assumptions and alternatives; do not equate a correct written answer with observed practical performance.

Question 4Fictional microscope calibration at one objective: 40 reticle divisions span 100 micrometres. Cell lengths are 12, 14, 13, 15 divisions. Compute their mean length and range. If the 100 micrometre calibration span has a maximum error of 2 micrometres and reticle counts are exact for this calculation, estimate the common length bound on the mean. Evaluate 'enlarging the photograph will reveal ribosomes'. Specify a representative sampling improvement and explain what a labelled drawing may legitimately include from this measurement-only record. Give a connected worked response with calculations, justified conclusions and limitations. All datasets are original fictional practice, not official experiment results. Written/supplied-data work only; any actual laboratory or field activity requires teacher approval, risk assessment and supervision. No human trials. Primary reading: https://www.cambridgeinternational.org/Images/664560-2025-2027-syllabus.pdf5 indicative marks
Calculate, analyse and evaluate5 indicative marksCalculator allowed

Fictional microscope calibration at one objective: 40 reticle divisions span 100 micrometres. Cell lengths are 12, 14, 13, 15 divisions. Compute their mean length and range. If the 100 micrometre calibration span has a maximum error of 2 micrometres and reticle counts are exact for this calculation, estimate the common length bound on the mean. Evaluate 'enlarging the photograph will reveal ribosomes'. Specify a representative sampling improvement and explain what a labelled drawing may legitimately include from this measurement-only record. Give a connected worked response with calculations, justified conclusions and limitations. All datasets are original fictional practice, not official experiment results. Written/supplied-data work only; any actual laboratory or field activity requires teacher approval, risk assessment and supervision. No human trials. Primary reading: https://www.cambridgeinternational.org/Images/664560-2025-2027-syllabus.pdf

Cambridge 2027: Partial conceptual match

Calibration, resolution and biological inference: selected written evidence only. Four calibrated lengths, mean/range and shared 2% bound independently checked; image enlargement not conflated with resolution. Science practical-N and computing rN rows are internal identifiers, not official numbered leaf syllabus codes. Aggregate rows are only partially supported. Actual apparatus use, candidate coding execution and practical attainment are not demonstrated here. Independent teacher review remains required.

AI-assisted placement. Independent teacher approval pending.

Show indicative guidance

Worked guidance

  1. Divide physical span by reticle span: 100/40 = 2.50 micrometres per division. Multiplication gives 30.0, 35.0, 32.5, 37.5; mean = 135/4 = 33.75 micrometres and range = 37.5 - 30.0 = 7.5. Keep the unrounded mean for the bound calculation.
  2. All lengths share the same scale. Its 2/100 = 2.0% bound therefore contributes 33.75 x 0.02 = 0.675 micrometres to the mean; dividing by sqrt(4) would incorrectly treat a common calibration error as independent. Under only this error model a rounded statement is approximately 33.8 +/- 0.7 micrometres, but counting and sampling uncertainties were excluded.
  3. Recalibrate after changing objective. Choose predefined random fields and an unbiased cell-selection rule across independent specimens, retaining awkward but valid cells. More pixels or a larger print cannot recover spatial detail absent from the original image; a different resolving instrument would require new evidence. A length table alone supports a measurement table, not invented nuclei or organelles. Real microscopy and specimen preparation remain supervised, unobserved skills.

Self-marking points

View marking points
  1. Scale is 2.50 micrometres/division; lengths are 30.0, 35.0, 32.5 and 37.5 micrometres.
  2. Mean is 33.75 micrometres, sensibly 33.8; range is 7.5 micrometres.
  3. The shared calibration contribution is 2.0%, giving a mean-length bound of 0.675 micrometres, approximately 0.7.
  4. Enlargement increases displayed size, not the resolving power of the original optical record.
  5. No structures or tissue boundaries were supplied, so a cellular drawing cannot be invented; actual observations and scale provenance are needed.

Examiner tip

Indicative original worked practice, independent teacher approval pending. Explain assumptions and alternatives; do not equate a correct written answer with observed practical performance.

All AS & A Level subjects