What are Amphibians?
Amphibians are the oldest terrestrial* vertebrates* existing in the world today (even older than dinosaurs). In fact, it has been estimated that the first amphibian evolved approximately 360 million years ago. In contrast, Tyrannosaurus rex, one of the later Dinosaurs to evolve, lived approximately 67 million years ago. Furthermore, in a time when all vertebrates were fish (or similar to fish) amphibians were the first vertebrate animals to attempt a life on land. Because they were one of the first animals to live, at least, part of their life on land, most amphibians today still need to have a source of water nearby for survival. For example, their skin is incredibly thin, much more so than reptiles or mammals. So thin, in fact, that most amphibians do not drink water, but absorb it. On the same note, amphibians can loose water very easily though their skin as well. Therefore, if they do not have a source of water nearby, they will become desiccated (or dried-out) and may die. Likewis
The term “amphibian” is a catch-all for all non-amniotic (lacking eggs with a shell), ectothermic (“cold-blooded”) tetrapod animals that spend at least part of their time on land. Living examples include frogs, toads, salamanders, newts, and caecilians. There are only about 6,200 living species described by science, but there are many extinct amphibians in the fossil record. Of the three subclasses of amphibians (Labyrinthodonti, Lepospondyli, Lissamphibia), only one, Lissamphibia, is extant. Amphibians are much less successful today than in the geologic past, having been outcompeted by reptiles and mammals. Amphibians are animals that move in and out of the water. Lacking scales like reptiles, amphibians are more prone to dessication (drying out), and so most species require frequent dips to stay moist. Except for a few frog species, amphibians are dependent on pools of fresh water to lay their eggs in. These eggs sit in the water, with some entering into symbiotic relationships with
