In “Eye to Eye” (p. 20), you learned how animals’ eyes are adapted to their lifestyles. In this passage, you’ll learn how a reliance on the ocean for food may have led to changes in the vision of a small population of people in Asia. ADAPTED TO DIVE

For centuries, a small population of Moken people has lived a seminomadic life along the coasts of Myanmar

and Thailand. They spend most of their time on boats and use traditional methods to gather food from the ocean.

Even children can dive meters beneath the surface without masks to pluck tiny shellfish from the seabed. One

reason they’re so good at this: Scientists have discovered that the Moken are adapted to have clearer-than-average

underwater vision.

Normally, when you open your eyes underwater, your vision is blurry. That’s because clear vision depends on the

fact that light waves refract when they travel from one material into another, such as from the air into your eye. This

bending helps focus an image on the eye’s light-detecting retina. Light waves that travel from water into the eye

don’t refract as much, because the fluids in the eye have properties similar to those of water.

Researchers have discovered that the Moken have developed an adaptation that solves this problem. Their eyes’

lenses change shape when they dive. The shape change increases refraction, helping to create a focused image.

The size of their pupils also constricts. That further improves their ability to focus on objects at different distances.

Most people don’t normally have these adaptations. Eye tests revealed that European children see as well as

Moken kids on land, but the Moken children’s eyesight underwater was twice as sharp.

Which of the following BEST represents the central idea of the passage?

A Moken people have better eyesight than Europeans under all conditions.
B Your vision depends on how light waves bend.
C Living near the ocean will improve your underwater vision.
D Moken people have developed superior underwater vision.

Why is vision normally blurry underwater?
A Light waves don’t refract as much when they travel into the eyes underwater.
B Pupils don’t open wide enough underwater to let in light.
C Light waves bend too much when they move from water into the eye.
D The retina can’t detect light waves underwater.

Explain how the Moken people’s environment
played a role in the development of their adaptations.
What evidence supports the idea that they wouldn’t
have the adaptation if they lived in a different
environment?

Please Hep