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Did you know that amphibians were the first animals to become terrestrial and live on land? Well, it is so.
Almost all amphibians have two live cycles: they begin their life in (fresh) water and then finish it mainly on land.
This is the origin of the word amphibian, which means “both sides of life”. As young amphibians evolve first in water, adult amphibians have to lay their eggs in lakes and rivers;
only a few amphibians can survive in seawater (though not thrive), but they are no true marine amphibians.
Their eggs hatch into an aquatic larva (tadpole) that resembles a fish with tail and likewise breathes with gills.
Then the tadpole goes through metamorphosis and the tadpole grows into its adult air-breathing form with lungs and legs and moves to live on land.
Depending on the structure of their body, amphibians will jump, climb or crawl; they dive and swim when in the water.
Adult amphibians have a thin smooth skin that is moist. They breathe with lungs and are cold-blooded animals, which means that the temperature of their body depends on the temperature of the environment they live in.
Like reptiles, amphibians have a three-chambered heart - two atria and one ventricle – and a mixture of oxygenated and deoxygenated blood goes through their blood stream.
Common amphibians include frogs, toads and salamanders and also a limbless species that resembles a snake.
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