B3.1 Gas Exchange - written task
This structured extension question is in the style of the IB exam questions. It has a particular focus on the concept of gas exchange in a leaf.
The "describe" command term invites exam candidates to form more detailed answers than the “outline” command term.
To create a concise yet detailed answer phrases should focus on specific details but ensure that they connect a structure with its function or a cause with its effect.
- Describe - "Give a detailed account" usually needs more points and is worth more marks.
- Outline - "Give a brief account or summary" is often shorter and worth fewer points.
This image shows a dicotyledon leaf in cross section, at 400x magnification under a light microscope.
The leaf carries out photosynthesis, gas exchange and transpiration.
Gas exchange surfaces have several adaptations to promote the exchange of carbon dioxide and oxygen between the environment and the leaf.
Describe the adaptations of the dicotyledon leaf that make it an efficient gas exchange surface.
(6 marks)
Teacher note - an annotated diagram could be used here
The model answer point reflect the content of the guide in topic B3.1 - other valid points may also be correcct.
- This could be a classroom task, a revision moment or a homework activity.
- There is a hidden model answer which appears when the answer is submitted.
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