Amphibians have a juvenile stage and an adult stage, and the circulatory systems of the two are distinct.
æmfˈɪbiənz hæv ɐ dʒˈuːvənˌaɪl stˈeɪdʒ ænd ɐn ɐdˈʌlt stˈeɪdʒ, ænd ðə sˈɜːkjʊlətˌoːɹi sˈɪstəmz ʌvðə tˈuː ɑːɹ dɪstˈɪŋkt.