The spread of antibiotic resistant bacteria in hospitals is best explained by
- A. bacteria learning to resist the drug during exposure
- B. the antibiotic causing the resistance mutation to occur
- C. each bacterium passing on resistance it acquired in its own lifetime
- D. survival and multiplication of resistant mutants already present in the population
Explanation
Resistance mutations arise at random before the drug is ever met, and the antibiotic then kills the sensitive majority, leaving the rare resistant cells to multiply without competition. Because bacteria divide every twenty minutes, natural selection is visible within days, which is why this is the standard modern demonstration of Darwin's mechanism. The other three options are all Lamarckian readings of the same observation.
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