Class Amphibia (phylum Chordata)
Examples and Traits
There is about 4800 species in Class Amphibia. They have two pairs of appendages (arms and legs), meaning they are tetrapods. They have thin, moist skin, lacking scales like their predecessors. They go through metamorphosis when developing. They respire across their skin and lungs. They are ectotherms, meaning that they get their body warmth from outside conditions. They have external fertilization with separate sexes. They have a digestive tract with specialized organs. They have a Cloaca; an opening at the butt end which is the opening for the intestinal, urinary and reproductive tracts. They have kidneys for excretion, and a three chambered heart. There are three groups/orders; frogs and toads, Salamanders and newts, and caecilians. Frogs and toads have no tail, strong back legs for jumping great distances in comparison to their body size, and use calls to signal things like mating. The difference between frogs and toads is that frogs have wetter, smoother skin and move through jumping, while toads have drier, bumpier skin and move through walking more than jumping. Salamanders and newts have a tail and legs on the side of their body. Newts are aquatic, while salamanders are found in moist environments. Caecilians are both legless and blind. They like moist soil, and are tropical. They eat worms and insects. They perform internal fertilization with separate sexes.