Final answer:
Frogs and turtles are in the same phylum (Chordata) but belong to different classes (Amphibia for frogs and Reptilia for turtles). The correct taxonomic levels are Phylum and Class.
Step-by-step explanation:
Frogs and turtles, though sharing the same phylum, exhibit distinct characteristics placing them in different classes. Frogs, encompassing both frogs and toads, fall under the class Amphibia, characterized by their amphibious lifestyle. Turtles, on the other hand, belong to the class Reptilia, defined by their terrestrial existence and protective shells. Both Amphibia and Reptilia are nested within the broader phylum Chordata, uniting organisms with a notochord at some stage of their development. This diverse phylum extends beyond frogs and turtles, encompassing various vertebrates such as fish, mammals, and birds, showcasing the vast array of life forms that share a common chordate ancestry.