A student compared the number of stomata on the upper and lower surfaces of a leaf - Edexcel - GCSE Biology - Question 3 - 2018 - Paper 1
Question 3
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 5.
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Worked Solution & Example Answer:A student compared the number of stomata on the upper and lower surfaces of a leaf - Edexcel - GCSE Biology - Question 3 - 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 the leaf peel flat. This helps to prevent drying out and ensures that the leaf peel is in contact with the microscope slide for clear viewing.
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 is thinner than the whole leaf, allowing light to pass through more effectively. If the whole leaf were used, it would be too thick and opaque, preventing light from shining through and making it difficult to identify the stomata or cells.
Step 3
How many stomata are present in the section of the leaf peel that the student viewed?
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Answer
The section of the leaf peel that the student viewed contains 3 stomata.
Step 4
Describe how guard cells are involved in the opening and closing of stomata.
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Answer
Guard cells control the opening and closing of stomata by taking in water through osmosis. When guard cells absorb water, they become turgid, causing the stomata to open. Conversely, when they lose water, they become flaccid, and the stomata close.
Step 5
Explain why there are no stomata on the upper surface of the leaf.
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Answer
There are no stomata on the upper surface of the leaf to reduce water loss during transpiration. Stomata are typically located on the lower surface to facilitate gas exchange while minimizing water evaporation.
