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Analogy: Jaws versus Flipper

Shark/dolphin similarities

Although their differences are certainly substantial (e.g., sharks are cold-blooded and dolphins are warm-blooded), sharks and dolphins have some undeniable similarities: side fins, a dorsal fin, and a torpedo-shaped body. These similarities are analogies — traits the two lineages evolved independently as adaptations for moving swiftly in the water. Sharks were gliding through the oceans long before dolphins descended from land-dwelling mammals. Dolphins evolved flippers, a dorsal fin, and a torpedo-shaped body as natural selection shaped them for the life of an ocean predator.

Shark/dolphin tree

Whitetip Reef Shark photo by Dong Lin © California Academy of Sciences; Dolphin photo by M. Winning © California Academy of Sciences.

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