A technician carried out a trial to decide where to inoculate agar plates. Eight sterile nutrient agar plates were not inoculated. The lid of each plate was lifted slightly for 10 seconds at the stated distance from a flame. All the plates were then incubated under the same conditions.
| Distance from flame in cm | Colonies on plate 1 | Colonies on plate 2 | Colonies on plate 3 | Colonies on plate 4 |
|---|---|---|---|---|
| 15 | 0 | 1 | 1 | 2 |
| 80 | 5 | 6 | 6 | 7 |
Calculate the mean number of colonies at each distance from the flame.
The technician will inoculate 12 agar plates. Use the means to predict how many fewer unwanted colonies would grow in total if the plates were opened 15 cm from the flame instead of 80 cm from the flame.
The technician decides to open the plates 15 cm from the flame. Evaluate this decision. Use the results and your knowledge of aseptic technique.
282 exam-style questions on AQA GCSE Biology 1.1 Cell structure, covering 1.1.1 Eukaryotes and prokaryotes, 1.1.2 Animal and plant cells, 1.1.3 Cell specialisation, 1.1.4 Cell differentiation, 1.1.5 Microscopy, and 1.1.6 Culturing microorganisms. Each one has a worked solution and a mark scheme showing where the marks go.