Q.Mention eight features of class Amphibia.

[!TLDR] Amphibia shows a dual aquatic-larval/terrestrial-adult life cycle, moist glandular skin, a three-chambered heart, lungs plus cutaneous respiration, and the first tongue/eyelids/middle ear among the classes covered. …

[!ANSWER] Class Amphibia shows a defined set of features marking its transitional position between aquatic fishes and fully terrestrial reptiles.

1. Amphibians typically show a biphasic life cycle: an aquatic, gill-breathing larval stage (e.g. the tadpole) that metamorphoses into a largely terrestrial, air-breathing adult. 2. The skin is moist, glandular, and highly permeable, permitting cutaneous (skin) respiration, but making the animal vulnerable to water loss away from moist habitats. 3. The heart is three-chambered (two atria, one undivided ventricle). 4. Adults typically possess true lungs, used alongside cutaneous respiration, for aerial gas exchange. 5. A tympanic middle ear, with an eardrum for detecting airborne sound, appears for the first time in this class. 6. Eyelids, with a protective nictitating membrane, likewise appear for the first time. 7. Fertilisation is typically external, and eggs are laid in water or moist environments, lacking the protective extra-embryonic membranes (amnion) of the more fully terrestrial reptilian egg. 8. Locomotion is often by a di …

• Describing the amphibian egg as amniotic (having protective extra-embryonic membranes) — that feature first appears in Reptilia, not Amphibia. …