CAIE A Level Biology 9700 · Selection and evolution
A new antibiotic, novamycin, is introduced to treat infections caused by the bacterium Staphylococcillus fictilis. Initially, novamycin is very effective, but after several years, some infections no longer respond to treatment. Using the principles of natural selection, explain how a population of S. fictilis can become resistant to novamycin.
5 marks, so the mark scheme is looking for about 5 separate creditworthy points. Making the same point twice in different words earns it once.
Explain means: Give the reasons or the mechanism: why or how something happens. Link each point to the next with because, so or which means. A list of facts with no links usually loses the reasoning marks.
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