The sentence depicts how dolphins are different than porpoise due to the nature of the animals with the dolphin being a mammal and a porpoise being a fish. I believe that the sentence in this compare and contrast essay was organized by subject by subject. There are two subjects, the dolphin and the porpoise which was differentiated with each other even though they both swim in the sea, the creatures are not alike since mammals are warm-blooded animals while fishes are cold blooded animals which was pointed out in a subject to subject manner.