Pupil sheet · The eye

The eye — final check

Name ______________________ Date ____________

Work alone, with the lesson closed. Answer every question; there are no hints.

1. identify

The diagram shows a cross-section of an eye drawn with the light arriving from the right. Identify the parts labelled A to G.

A cross-section of an eye, drawn with light arriving from the right, with seven parts lettered. A: a clear oval part behind the gap in the coloured ring. B: the layer lining the back of the eye. C: the clear curved window at the very front. D: the thick cord leaving the back of the eye. E: the coloured ring of muscle, seen as two halves. F: the place where the cord leaves, where the lining has no light-sensitive cells. G: the gap between the two halves of the coloured ring.

2. state

State the function of (a) the cornea, (b) the iris and (c) the optic nerve.

(a) Cornea

(b) Iris

3. identify / state

For each event, identify the sense organ that detects it and state the stimulus its receptors respond to: (a) you hear thunder; (b) you feel the warmth of the sun on your face.

(a) Thunder

(b) The sun's warmth

4. state / explain

The drawings show the same person's eye, P, Q and R, in three different lights. (a) State the order of the eyes from the dimmest light to the brightest. (b) Explain how you decided.

Three eyes of the same person, P, Q and R, seen from the front, each photographed in a different light. The pupil of P is middle-sized, about 4.5 mm across; the pupil of Q is the widest, about 7.5 mm; the pupil of R is the narrowest, about 3 mm.

(a) Dimmest to brightest

(b) How you decided

5. explain

There is a power cut at night, and a kitchen suddenly goes dark. Explain the pupil reflex that follows in the eyes of a person in the kitchen. Use the words stimulus, receptors, effector and response.

6. describe / explain

Supplement: describe how the muscles of the iris change the pupil when the light becomes bright, and explain why these muscles are described as antagonistic.

7. identify / state

Supplement: the diagram shows a cross-section of an eye, with the light arriving from the right and four places lettered. (a) Identify the letter that shows the fovea. (b) State the function of the fovea. (c) Identify the letter that shows the place on the retina with no rods and no cones.

A cross-section of an eye, with light arriving from the right and four places lettered. S: a small pit in the lining at the back of the eye, straight behind the middle of the clear oval part. T: the place on the back lining where the thick cord leaves, below the middle. U: the back lining, part way round from the pit, above the middle. V: the clear oval part behind the gap in the coloured ring.

(a) Fovea

(b) Function

8. predict / explain

Supplement: after an injury, the ciliary muscles in one of a patient's eyes cannot contract. Predict whether that eye sees near objects or distant objects clearly, and explain your prediction.

9. explain

Supplement: a person has only two of the three kinds of cone. In bright daylight they cannot tell a red tomato from a green one, although they can see both tomatoes clearly. Explain this.

10. describe

Supplement: describe the distribution of rods and cones across the human retina.