A leaf contains palisade mesophyll tissue and spongy mesophyll tissue. Explain how these tissues contribute to the leaf working as an organ.

AQA GCSE Biology (8461) — 4.2.1 Principles 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 with a similar structure and function.
Palisade mesophyll is specialised to carry out photosynthesis.
Spongy mesophyll is specialised for gas exchange.
An organ is an aggregation of tissues performing a specific function; different tissues work together so the leaf can perform its overall function.

Examiner tips

Use the exact terminology from the mark scheme – e.g. "tissue", "palisade mesophyll", "spongy mesophyll", "organ". Show the link between each tissue’s structure and its function. Keep the answer concise – one sentence per point will earn full marks.

Common mistakes

Mixing up the functions of palisade and spongy mesophyll. Using vague words such as "help" instead of specific functions like "photosynthesis" or "gas exchange". Omitting the definition of a tissue or an organ.

Mark scheme (4 marks)

A tissue is a group of cells with a similar structure and function
Palisade mesophyll is specialised to carry out photosynthesis
Spongy mesophyll is specialised for gas exchange
An organ is an aggregation of tissues performing a specific function / different tissues work together so the leaf can perform its overall function

Key terms in this question

tissue · organ · palisade mesophyll · spongy mesophyll