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1Repair Windows errors before they cause bigger problems2Fix the driver behind crashes, sound loss and screen glitches3Clear out junk files and repair common Windows errorsSharks are fish, not mammals. More precisely, they are cartilaginous fish: their skeletons are made primarily of cartilage, and they take oxygen from water through gills.
What kind of fish is a shark?
Sharks belong to the cartilaginous-fish group, along with skates and rays. NOAA distinguishes cartilaginous fish from bony fish by the material of their skeletons: sharks have skeletons made primarily of cartilage rather than true bone. Cartilage is the flexible tissue found in places such as the human nose and ears. NOAA Fisheries explains the difference between bony and cartilaginous fish, and its shark classification guide places sharks in class Chondrichthyes and subclass Elasmobranchii. NOAA’s shark taxonomy guide
How do sharks breathe?
Sharks use gills to extract oxygen from water; they do not breathe air with lungs as mammals do. Most have five gill slits on each side, though some species have six or seven, according to Smithsonian Ocean’s shark overview. NOAA also states directly that “Sharks are fish” and describes their gill breathing in its shark facts page, updated August 20, 2025.
Why is a whale shark still a fish?
“Whale shark” is the common name of a shark species, not evidence that it is a whale or a mammal. The animal is classified by its biology, including its cartilaginous skeleton and gills—not by a name that contains “whale.” The Smithsonian National Museum of Natural History webinar transcript discusses the whale shark as a fish.
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Does giving birth to live young make a shark a mammal?
No. Shark reproduction varies: some species lay eggs, some hatch from eggs retained inside the mother, and others give birth to live young. Live birth alone does not define a mammal; sharks remain fish. Smithsonian Ocean describes these reproductive strategies.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Sharks and mammals: what is the difference?
Sharks and dolphins both live in the ocean, but habitat does not determine whether an animal is a fish or mammal. Sharks breathe underwater with gills. Dolphins are mammals that breathe air with lungs. NOAA Ocean Service explains why dolphins are mammals, not fish.
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