Chapter 28, Problem 20A

Summary Introduction

To write:

The correct term by replacing the italicized word in the given sentence.

Introduction:

Amphibians include frogs, toads, salamanders, newts, and legless caecilians. Most amphibians are distinguished by moist skin without scales, four legs, exchange of gases through skin, a circulatory system with double loop, lungs, and aquatic larvae.

Explanation of Solution

For most amphibians, vision is an essential feature. They use sight to find and catch the prey that is traveling at high speeds and to avoid predators. Frog's eyes have structures called nictitating membranes. The nictitating membrane is a translucent eyelid that can pass around the eye to shield it underwater and prevent it from drying out on the land.

Conclusion

Thus, the amphibians have nictitating membrane to protect their eyes from drying out. This membrane can move across the eye.