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The overall sleek outlines of sharks' and dolphins' bodies might look pretty similar from a distance, but the differences between these two groups of animals are immense. The broad differences cover everything from body temperature to visual elements as basic as the shapes of their dorsal fins.
Dorsal Fin Basics
Dorsal fins are probably the most commonly seen parts of dolphins' and sharks' bodies. They're the conspicuous appendages that are situated on the upper backs of both animals. The vertical fins perform extremely crucial functions, helping them make quick turns and maintain their balance.
Dorsal Fins With Different Shapes
Sharks' dorsal fins are markedly straighter in appearance than those of dolphins. They have a pretty straightforward triangular shape. Dolphins' dorsal fins have more of a soft curl to their form, similar to a wave. The fins curl to the back, rather than to the front. Porpoises, as fellow cetaceans, are kin to dolphins, although their dorsal fins have similar triangular outlines to those of sharks.
Visual Differences Apart from Dorsal Fins
Although the dorsal fins might be enough to help some differentiate between dolphins and sharks, other physical differences also exist. Sharks have vertical tails, while dolphins' tails are flat. When sharks swim, their tails sway. When dolphins swim, their tails have a totally different reaction -- they continuously rise and fall.
An onlooker would never get close enough to notice, but dolphins, as mammals, are indeed equipped with hair. They even enter the world with some of it, right by their snouts. Sharks are fish and completely devoid of hair. Other physical differences between the species involve their skeletons, although they're not at all visible. Dolphins have bone skeletons, and sharks have cartilage ones.
Other Key Differences
Dolphin mothers have a totally different approach to caring for their youngsters than shark mothers do. The warm-blooded cetaceans nurse their offspring, just as humans, dogs and cats do. Mother sharks not only don't nurse their babies, they don't partake in any confirmed parental responsibilities in general.
Dolphins also breathe via their blowholes, while sharks utilize their gills.
As mammals, dolphins have consistent body temperatures. Sharks' body temperatures constantly shift because they adjust to the current temperatures of the water surrounding them.
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