Practical skills and essay
Practical techniques in biology
Serial dilution: dilute by the same factor each time (e.g. 1 cm³ + 9 cm³ water = ×10). Colorimetry: measure absorbance or transmission; use a calibration curve of known concentrations to read unknowns. Osmosis practical: measure % change in mass of tissue in different solutions; where the line crosses zero, the solution's ψ equals the tissue's. Enzyme rates: rate = 1/t or gradient of the initial slope; control temperature with a water bath and pH with buffers. Biological drawings: clear lines, no shading, proportions correct, labels with ruled lines. Data processing: means (exclude anomalies), % change, standard deviation (spread around the mean), error bars; overlapping SD bars suggest the difference may not be significant. Aseptic technique for microbes: flame loops, work near a Bunsen, tape lids, incubate at 25 °C.
≈ 50 minPlanning, analysis and evaluation
Planning: state the independent, dependent and standardised (controlled) variables, how each is changed, measured or kept constant, and the range and intervals of the IV. Include a control (e.g. boiled enzyme) and repeats (at least 3). Assess risks. Statistical tests (with a null hypothesis of no difference/association): t-test compares two means; χ² compares observed with expected frequencies; Spearman's rank or Pearson's test correlation. If the calculated value is greater than the critical value at p = 0.05, reject the null hypothesis. Evaluation: validity (measures what it should, all other variables controlled), reliability/repeatability (consistent repeats), accuracy, precision; identify anomalies; suggest specific improvements (e.g. use a thermostatically controlled water bath).
≈ 50 min