CAIE A Level Biology 9700 · Transport in plants
In a herbaceous dicotyledonous plant, phloem tissue contains two types of living cells: sieve tube elements and companion cells. These cells have distinct structures but work closely together. Compare the structure of sieve tube elements and companion cells, and explain why the sieve tube element requires a companion cell to function.
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.
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.