Draw a diagram showing a normal iris and what happens to the iris when a light in shined into the human eye. (1 mark). What causes this to happen? (2 marks)
(Any diagram showing an iris that has constricted) 1 mark
In high light levels (1 mark) Accept reflex action due to increased photoreceptor action or words to that effect
circular muscles relax and radial muscles contract to constrict the iris (1 mark)
JP
Related Biology GCSE answers
All answers ▸Name and describe the features of the type of blood vessel which takes high pressure blood from the heart to other parts of the body
Explain the process of eutrophication.
How can temperature affect an enzymes activity?
Name three non-specific human defences against diseases