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Figure 4 shows a reflex in the iris of the human eye in response to changes in light levels - AQA - GCSE Biology - Question 5 - 2018 - Paper 1
Question 5
Figure 4 shows a reflex in the iris of the human eye in response to changes in light levels. Describe the changes in the pupil and iris going from A to B in Figure ... show full transcript
Worked Solution & Example Answer:Figure 4 shows a reflex in the iris of the human eye in response to changes in light levels - AQA - GCSE Biology - Question 5 - 2018 - Paper 1
Step 1
Describe the changes in the pupil and iris going from A to B in Figure 4.
Answer
In Figure 4, as we move from A to B, we see that the pupil has dilated. This means that more light is allowed to enter the eye. The iris also shows changes, as its structure adjusts in response to light levels.
Step 2
Explain how these changes occur.
Answer
These changes occur due to the contraction and relaxation of the muscles in the iris. In lower light levels, the circular muscles of the iris relax, allowing the radial muscles to contract, resulting in pupil dilation. This reflex helps to adjust the amount of light entering the eye to improve vision.