5090_s26_qp_42 — 2026 May-June Biology 5090 Question Paper 4 Variant 2 · Cambridge CAIE O Level

Describing osmosis using vague concentration language instead of water potential

“When explaining osmosis, the best answers referred to the differences in water potential inside and outside the cell. Candidates should be encouraged to use this terminology, as stated in the syllabus. If they describe concentration differences, it is often unclear whether they are referring to water or solute concentration.”— 5090 Paper 2/21, May/June 2023

How to fix: Always use the term 'water potential' when explaining osmosis. The correct definition: osmosis is the net movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane. Saying 'high concentration to low concentration' is ambiguous and loses marks.

Data analysis errors — describing differences between groups instead of trends over time

“The main issue here was that candidates often commented on differences in numbers between males and females or between age groups, in the same time period. The question asked for changes in the percentages but this was often overlooked.”— 5090 Paper 2/21, May/June 2023

How to fix: Read the question command carefully. If it asks for 'changes' or 'trends', describe how values change over time (increased, decreased, stayed constant). If it asks for 'differences', compare between groups. Always use data from the table or graph with correct units. Quote specific figures to support your answer.

Graph drawing errors — non-linear scales, missing units on axes, joining points incorrectly

“Full marks could not be awarded where the graphs were too small or where the scales were not linear. A common error on this graph was to have a scale on the y-axis from -0.1(g) to +0.1(g), instead of -1.0(g) to +1.0(g).”— 5090 Paper 3/32, May/June 2023

How to fix: Graph checklist: (1) Use a linear scale — equal spacing for equal intervals, (2) Label both axes with the variable name AND units, (3) Use more than half the grid area, (4) Read the question — if it says 'ruled lines' join points with a ruler, do NOT draw a curve or line of best fit, (5) Plot all data points including zero values, (6) Show interpolation working as drawn lines from axis to graph line.