CAIE A Level Biology 9700 · Transport in plants
A student prepared a transverse section of a stem from a young sunflower plant (a herbaceous dicotyledon) and observed the phloem under a light microscope. The student focused on the two types of cells that make up the phloem: companion cells and sieve tube elements.
Compare the structural features of companion cells and sieve tube elements, and explain how each cell type is adapted to its role in phloem transport.
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.
Compare means: Give similarities or differences between two things, and say which side each point belongs to. Write each point as a pair, for example: A is X, whereas B is Y. Two separate descriptions rarely earn the marks.
Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.