Practice question

Gills in amphibians appear predominantly during aquatic larval phase as external filamentous branched structures richly vascularized serving tadpole respiration in water, subsequently resorbed during metamorphic climax triggered by thyroxine surge inducing apoptosis of branchial tissue and maturation of lungs. Adult terrestrial frogs lack functional gills entirely, relying on skin, lungs and buccopharynx. Aquatic salamanders like Necturus and axolotl exhibit neoteny retaining larval external gills throughout life capable of reproduction. Embryonic gill grooves transient, not permanent, distinguishing typical biphasic development. This concept holds high importance for NEET, CBSE board, CUET and competitive examinations focusing on comparative