A dog rehoming centre investigated two policies for using the same antibiotic. The dogs in group 1 were given the antibiotic every day, including when they were healthy. The dogs in group 2 were given the antibiotic only when they had a bacterial infection.
The investigation lasted 12 weeks.
| Result | Group 1: antibiotic every day | Group 2: antibiotic only for a bacterial infection |
|---|---|---|
| dogs that developed a bacterial infection (%) | 5 | 13 |
| resistant bacteria at the start (% of bacteria sampled) | 6 | 7 |
| resistant bacteria after 12 weeks (% of bacteria sampled) | 42 | 11 |
Discuss whether the centre should continue giving the antibiotic every day. Use the results to support your answer and explain how the pattern in resistant bacteria could have developed.
85 exam-style questions on Edexcel GCSE Biology 4.1 Evolution and natural selection, covering 4.1.1 Work of Darwin and Wallace and 4.1.2 Resistant organisms and evolution. Each one has a worked solution and a mark scheme showing where the marks go.