Cambridge IGCSE Biology practice

Paper 3 structured question: Sense organs

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Paper

Marks

Topic

Sense organs

Exam-style question

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Paper 3Theory (Core)3 marks

The pupil reflex involves changes in pupil size controlled by muscles in the iris in response to light intensity.

Diagram Description

The diagram shows the iris with circular muscles and radial muscles around the pupil.

a
Identify which muscles contract to make the pupil larger in dim light.
Your answer
Aim for approximately 1 distinct marking point.
[1]
b
Explain why the pupil changes size in response to light intensity.
Your answer
Aim for approximately 2 distinct marking points.
[2]

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Paper 3Theory (Core)3 marks

Description

When a person moves from a dark room to a bright room, the pupil size changes automatically.

a
State what happens to the pupil size when light intensity increases?
Your answer
Aim for approximately 1 distinct marking point.
[1]
b
Explain how the pupil reflex protects the eye when moving into bright light.
Your answer
Aim for approximately 2 distinct marking points.
[2]