Q.Name the structures that first appear in Amphibia (among the chordate classes covered in this chapter).

[!TLDR] Amphibia is the first class (among those covered) to show a tongue, eyelids, a middle ear, and true lungs. …

[!ANSWER] Several structures make their first appearance, in this chapter's survey of chordate classes, specifically in Amphibia.

A functional tongue, often used by many frogs to capture prey, first appears here (fish generally have a much less mobile, non-protrusible tongue). Eyelids, together with a nictitating membrane (a translucent, protective inner eyelid), also appear for the first time, protecting the eye now that the animal spends time out of water. A middle ear, with a tympanic membrane (eardrum) capable of detecting airborne sound, likewise first appears in Amphibia, since fishes detect vibrations chiefly through water-based mechanisms rather than an aerial hearing structure. Finally, true, functional lungs appear for the first time as a dedicated organ for aerial respiration, used alongside the amphibian's continued ability to respire through its moist skin (cutaneous respiration). …

• Naming a structure (e.g. lungs) without noting that cutaneous (skin) respiration continues alongside it in Amphibia. …