개구리는 땅과 물 둘 다에서 살 수 있을까?
The word "amphibian" is derived from the Ancient Greek term ἀμφίβιος ("amphíbios"), which means "both kinds of life", "ἀμφί" meaning "of both kinds" and "βιος" meaning "life". The term was initially used as a general adjective for animals that could live on land or in water, including seals and otters. Traditionally, the class Amphibia includes all tetrapod vertebrates that are not amniotes. Amphibia in its widest sense ("sensu lato") was divided into three subclasses, two of which are extinct:
The actual number of species in each group depends on the taxonomic classification followed. The two most common systems are the classification adopted by the website AmphibiaWeb, University of California, Berkeley and the classification by herpetologist Darrel Frost and the American Museum of Natural History, available as the online reference database "Amphibian Species of the World". The numbers of species cited above follows Frost and the total number of known amphibian species is over 7,000, of which nearly 90% are frogs.
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