A hospital sends its wastewater to a treatment works. Some bacteria in the wastewater can cause communicable diseases. The treated water is released into a river used for swimming.
Low concentrations of antibiotic X remain in the wastewater. A scientist kept a sample of the wastewater at an antibiotic X concentration of 0.25 mg/dm³ for 12 days. The scientist measured the total number of living bacteria and the percentage resistant to antibiotic X.
A local council is monitoring the river because it is used for swimming.
| Time in days | Number of living bacteria per cm³ | Bacteria resistant to antibiotic X in % |
|---|---|---|
| 0 | 1 200 000 | 3 |
| 4 | 430 000 | 20 |
| 8 | 500 000 | 61 |
| 12 | 860 000 | 88 |
Suggest how exposure to antibiotic X caused the changes in the bacterial population shown in the table.
The council measures only the total number of living bacteria in the river. Explain why this measurement alone would not show whether antibiotic-resistant bacteria were becoming a larger proportion of the population.
The hospital can install one of two additional wastewater treatment systems. Bacteria released into the river can reproduce.
The table gives data for the two systems when treating the same volume of wastewater.
| Treatment system | Resistant bacteria released per dm³ | Concentration of antibiotic X released in mg/dm³ | Annual cost in £ |
|---|---|---|---|
| P | 2 000 | 0.18 | 70 000 |
| Q | 6 000 | 0.01 | 120 000 |
Evaluate which treatment system the hospital should install.
252 exam-style questions on AQA GCSE Biology 3.1 Communicable diseases, covering 3.1.1 Communicable (infectious) diseases, 3.1.2 Viral diseases, 3.1.3 Bacterial diseases, 3.1.4 Fungal diseases, 3.1.5 Protist diseases, 3.1.6 Human defence systems, 3.1.7 Vaccination, 3.1.8 Antibiotics and painkillers, and 3.1.9 Discovery and development of drugs. Each one has a worked solution and a mark scheme showing where the marks go.