“What is an Amphibian?” Discovery Education Video Transcript
But no matter what kind they are, all amphibians are alike in some important ways. For one thing, they're all... They are all cold blooded their body temperature stays close to that of their surroundings. And here's another key feature most amphibians share-- A strong, sturdy skeleton such skeletons help amphibians function on land. As you know, the bodies of fish, And other creatures that live in water, are buoyant. They're largely supported by the water in which they live. Things are different, however, for land animals. There's no water to help hold them up. Instead, they rely on skeletons to help support their bodies and to give them form and shape. Along with being cold-blooded and having skeletons, something else amphibians share, be they frogs, toads, or salamanders, is their need for water And that's because amphibians are caught in the middle. They're transition creatures-- Part water animals and part land animals. Millions of years ago, Ancient amphibians were the first vertebrates to leave the water and spend much of their time on land. However they didn’t quite go all the way. Take for example, salamanders, such as those for which these amphibian specialists are searching. The salamander life cycle is typical of amphibians. Most of adult salamanders spent most of their time on land. When its time to breed however, they return to the water. That’s where the females lay their eggs and the males fertilize them. Here’s what the eggs look like in the water, their metamorphosis or change into adult salamanders is typical of most amphibians. As you can see salamander eggs are protected by a thick protective layer of jelly. The coating has one potential fatal flaw; it isn’t water proof that means the jelly can’t stop the eggs from shriveling up and dying if the water in which they are laid dries up. Here’s a salamander larva in its immature form that hatched from such eggs and notice the gills growing from the back of its head. These provide the larva with oxygen in which the water it lives. Over the next for weeks however the larva will mature into an adult such as this critter shown here with lungs to breathe air and sturdy legs to move around on land.