Final answer:
Hagfish, lampreys, sharks, and tuna are all part of the phylum Chordata and can be classified into the overarching group of fish.
Step-by-step explanation:
Classification of Hagfish, Lampreys, Sharks, and Tuna
Hagfish, lampreys, sharks, and tuna are all chordates that share the characteristic feature of a notochord, making them part of the large and diverse phylum Chordata. When considering the specific group these animals can be classified into, we must look at their unique characteristics. Hagfish and lampreys are known as jawless fish, which means they are part of the superclass Agnatha within the phylum Chordata. Sharks, on the other hand, along with rays and skates, are part of the class Chondrichthyes, which consists of cartilaginous fish. Tuna are classified as ray-finned fish within the clade Osteichthyes, which is known for bony fish. However, the question seems to be asking which overarching group includes all these organisms, and the answer is fish.