Structure:
Amphibians are vertebrates that stand between
fishes and four-legged animals (later tetrapods); most live in moist environments
which allows respiration through
the skin. They have paired lungs,
pedicellate teeth with a suture dividing the tooth base from the tip, have
an auricular opericulum, an extra ear bone, and eggs
without shells and extraembryonic membranes. Salamanders
have tails, and caecilians have scales and
are without feet or girdles, rather, burrowing in the soil of damp habitats.
They also have a solid, compact skull. The gross
features of vertebrates vary greatly from Class to Class. Young frogs,
tadpoles, loose their tails during metamorphosis as they become adults.
Toads are frogs with a ?warty? skin and parotoid gland swellings behind
the eyes; most live in dry climates.
Function:
As the Class of vertebrates interposed between
fishes and four-legged animals, amphibians represent transitional animals
originating from the Jurassic Period that exist between sea and land. Instead
of external gills, they have internal
lungs, and a much better, about 20 percent, source of oxygen than in
water. Frogs and toads jump or hop, but salamanders walk, and caecilians
burrow. Salamanders have no ear drum (typmanium) nor vocalizations, but
frogs, especially males, use this organ for establishing territorial areas
and courtship activities.
