Palisade mesophyll cells are found in plant leaves. Explain why palisade mesophyll is described as a tissue rather than an organ.

Pearson Edexcel International GCSE Biology (4BI1) — 2.1 Levels of organisation · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

A tissue is a group of cells that have a similar structure and function.
Palisade mesophyll cells all have a similar structure – they are elongated and contain many chloroplasts.
They all carry out the same function – photosynthesis.
An organ is an aggregation of different tissues; palisade mesophyll is only one type of tissue, so it cannot be an organ.

Examiner tips

Use the definition of tissue first, then give the two specific features of palisade mesophyll cells, and finish with the definition of organ to show why it is not an organ.
Show the logical sequence: tissue definition → cell features → function → organ definition.
Keep the answer concise – 4 marks can be earned with 4 short sentences.

Common mistakes

Confusing the terms tissue and organ, or saying palisade mesophyll is an organ because it is part of a leaf.
Failing to mention that an organ contains multiple tissues, or omitting the function of the cells.

Mark scheme (4 marks)

A tissue is a group of cells with a similar structure and function
Palisade mesophyll cells all have a similar structure / all contain chloroplasts
Palisade mesophyll cells all carry out the same function / photosynthesis
An organ is an aggregation of different tissues / palisade mesophyll is only one type of tissue so cannot be an organ

Key terms in this question

tissue · organ · palisade mesophyll