Biological termEasy0.5 marks
5(b)
Give appropriate biological / technical terms for the following:
Structure which helps in the adjustment of the size of the pupil.
Topic: Iris
Previous-year question practice database
Answer
Exam answer
IRIS.
Explanation
The iris is the coloured muscular curtain in front of the lens. Its muscles alter the size of the PUPIL — constricting it in bright light and dilating it in dim light — and so control how much light enters the eye.
DO NOT CONFUSE this with ACCOMMODATION, which is the adjustment of FOCUS by the CILIARY MUSCLES changing the shape of the lens. The iris controls the AMOUNT of light; the ciliary muscles control the FOCUS.
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