A student investigated how temperature affects the growth of a bacterium. She spread a sample of a bacterial suspension onto each of five agar plates. She incubated each plate at a different temperature and then counted the colonies on each plate.
Table: The number of colonies on each agar plate after incubation at five different temperatures
| Temperature / °C | Number of colonies |
|---|---|
| 5 | 4 |
| 10 | 12 |
| 15 | 31 |
| 20 | 58 |
| 25 | 96 |
Name the independent variable in this investigation.
Give two variables the student should have controlled.
Use the Table. Describe the pattern shown by these results.
Explain why the student should not have incubated one of the plates at 37 °C.
The student repeated the investigation using three plates at each temperature. Explain how this improves her results.
139 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.