An investigation was conducted to study the effect of water pH on the hatching success of Daphnia magna resting eggs (ephippia). Five replicate test tubes were set up for each of five pH levels: 4.0, 5.0, 6.0, 7.0, and 8.0. Each tube initially contained exactly 100 ephippia incubated in a controlled environmental chamber at 20 °C. After 10 days, the number of successfully hatched Daphnia in each tube was recorded.
The table shows the results of this investigation:
| pH | Tube 1 | Tube 2 | Tube 3 | Tube 4 | Tube 5 | Total number of hatched Daphnia |
|---|---|---|---|---|---|---|
| 4.0 | 3 | 4 | 2 | 5 | 1 | 15 |
| 5.0 | 18 | 19 | 17 | 21 | 20 | 95 |
| 6.0 | 45 | 42 | 48 | 44 | 46 | 225 |
| 7.0 | 78 | 12 | 81 | 79 | 82 | 332 |
| 8.0 | 28 | 32 | 30 | 29 | 31 | 150 |
Identify the anomalous result in the table and suggest a possible reason for this anomaly.
Explain why the results of this experiment can be considered reliable.
Describe the results shown in the table and state a conclusion for this experiment.
31 exam-style questions on Edexcel IGCSE Biology The organism in the environment. Each one has a worked solution and a mark scheme showing where the marks go.