A bacterial population contains 990 antibiotic-sensitive cells and 10 resistant cells. One antibiotic treatment kills 99% of the sensitive cells and none of the resistant cells. The survivors then reproduce.
Why can the resistant proportion increase even before reproduction starts?
Resistant cells become more numerous because the antibiotic increases their rate of cell division.
Sensitive cells become resistant because the antibiotic provides the mutation needed for their survival.
Resistant cells remain unchanged in number while most of the sensitive cells are removed.
Sensitive cells remain unchanged in number while resistant cells replace them through rapid reproduction.
37 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.