Bacteria are exposed to an antibiotic. A few survive and multiply, and later the whole population is resistant. This is best explained by:
Answer and explanation
Correct answer: B. Natural selection
- Step 1: Variation in resistance existed before exposure, caused by mutation.
- Step 2: The antibiotic killed sensitive cells, so resistant ones reproduced more and passed on the allele.
Answer
natural selection.
Why not the others: Bacteria do not change on purpose; the survivors were not random; the antibiotic's aim is to kill, not to breed bacteria.
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