2. A student compared the number of stomata on the upper and lower surfaces of a leaf - Edexcel - GCSE Biology Combined Science - Question 2 - 2018 - Paper 1
Question 2
2. A student compared the number of stomata on the upper and lower surfaces of a leaf. She completed a leaf peel as shown in Figure 3.
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Worked Solution & Example Answer:2. A student compared the number of stomata on the upper and lower surfaces of a leaf - Edexcel - GCSE Biology Combined Science - Question 2 - 2018 - Paper 1
Step 1
State why a coverslip is placed on top of the leaf peel.
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Answer
A coverslip is placed on top of the leaf peel to keep it flat during observation and to protect the specimen.
Step 2
Explain why the leaf peel rather than the whole leaf was viewed with a microscope.
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Answer
The leaf peel was viewed rather than the whole leaf because the peel is thinner, allowing light to pass through. This enables the cells and guard cells to be identified and observed clearly.
Step 3
State the number of stomata visible on Figure 4.
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Answer
There are 3 stomata visible on Figure 4.
Step 4
Describe how stomata open.
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Answer
Stomata open when guard cells take in water through osmosis, becoming turgid. This change in shape leads to the swelling of the guard cells, causing the stomatal pore to open.
Step 5
Explain why it is an advantage to the plant to have this distribution of stomata in the upper and lower surfaces of the leaf.
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Answer
Having no stomata on the upper surface reduces water loss through evaporation, while stomata on the lower surface facilitate gas exchange, allowing for optimal photosynthesis.
