Zoology · Ch 2 — Kingdom Animalia
Class Amphibia
Class Amphibia
Amphibia (Greek amphi, both; bios, life) were the first vertebrates, and the first tetrapods, to live in both aquatic and terrestrial habitats — the class's name reflects this dual life. They remain poikilothermic (cold-blooded). The body is divided into a head and trunk, with most species bearing two pairs of limbs; a tail may or may not be present depending on the group. The skin is smooth or rough, moist, pigmented and glandular — an important respiratory surface in this class.
Eyes are protected by eyelids, and the tympanum (visible externally) represents the ear. Respiration is carried out through three surfaces: gills (in larvae and some adults), lungs, and directly through the moist skin. The heart is three-chambered, and the kidneys are mesonephric. …
What this figure shows. Four amphibian body forms: Frog (Rana), a tailless body with long, powerful hind limbs adapted for jumping and swimming, smooth moist skin, and prominent bulging eyes with a visible tympanum behind each; Toad (Bufo), a similar tailless body but with drier, warty, rough skin and shorter hind limbs adapted for walking rather than leaping; Salamander, an elongated body retaining a long tail into adulthood with four roughly equal-sized limbs; and Icthyophis, a limbless, elongated, worm-like caecilian body wit …