Q.Describe the special sense organs of the frog.

[!TLDR] The frog's special senses include a tympanic ear for hearing, protruding eyes with a nictitating membrane, and chemoreceptors in the skin/mouth for smell and taste. …

[!ANSWER] The frog's sense organs are adapted to its dual aquatic/terrestrial existence.

Hearing is detected through a tympanic membrane (eardrum), a flat, disc-shaped membrane visible on the surface of the head just behind each eye, which vibrates in response to airborne sound and transmits this vibration, via a middle-ear bone, to the inner ear — the first appearance of an aerial hearing structure among the chordate classes covered in this chapter.

The frog's eyes are large and positioned so that they protrude above the top of the head, allowing the frog to see above the water surface while the rest of the body remains submerged. Each eye is protected by an upper and lower eyelid and, additionally, by a nictitating membrane — a thin, translucent inner eyelid that can be drawn across the eye to protect and moisten it (including underwater) without fully blocking vision. …

• Forgetting the nictitating membrane specifically, treating the frog's eye protection as just ordinary eyelids. …