CAIE A Level Biology 9700 · Cell structure
A student examines a photomicrograph of a dividing plant cell. The photomicrograph includes a scale bar labelled 10 µm, which measures 25 mm on the printed image. The student measures the length of a chromosome arm in the cell as 8 mm on the image.
Explain how the student can use the scale bar to determine the actual length of the chromosome arm. Describe each step, and state which measurements must be in the same unit before they can be compared.
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.
Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.