CAIE A Level Biology 9700 · Cell structure
A researcher isolates a microscopic particle from a hot spring. The particle is approximately 1.5 μm in diameter. It possesses a cell wall containing peptidoglycan, circular DNA, and 70S ribosomes. No nucleus or membrane-bound organelles are visible. The particle can replicate independently in a suitable nutrient medium.
Explain, using the evidence provided, why this particle is classified as a prokaryote and not as a eukaryote or a virus.
4 marks, so the mark scheme is looking for about 4 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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