A fish farm has not used antibiotic Y before. Bacteria are causing disease in the fish.
Scientists measure the number of bacteria in the water before and after antibiotic Y is used. Some surviving bacteria are then grown for 10 generations in water without antibiotic Y.
| Stage | Total number of bacteria per cm³ | Number of bacteria per cm³ able to survive antibiotic Y |
|---|---|---|
| Before antibiotic Y is used | 8.0 × 107 | 1.6 × 104 |
| Three days after antibiotic Y is used | 1.6 × 104 | 1.6 × 104 |
| After 10 generations without antibiotic Y | 1.6 × 107 | 1.6 × 107 |
Calculate the percentage of bacteria able to survive antibiotic Y before the antibiotic was used.
Explain the change in the bacterial population after antibiotic Y was used and why resistance was still present after 10 generations without the antibiotic.
71 exam-style questions on AQA GCSE Biology 6.3 The development of understanding of genetics and evolution, covering 6.3.1 Theory of evolution, 6.3.2 Speciation, 6.3.3 The understanding of genetics, 6.3.4 Evidence for evolution, 6.3.5 Fossils, 6.3.6 Extinction, and 6.3.7 Resistant bacteria. Each one has a worked solution and a mark scheme showing where the marks go.