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Biological Environment > Sharks |
Earth Earlier Earlier 390 Million Years ago Later Earth After Animals Later |
This site tells the story of the history of the universe. Click Earlier and Later to follow the story. Note: Many facts have been simplified to make them easier to understand. |
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Sharks, skates and rays evolved from jawless fish about 390 million years ago. Although their ancestors had bone, the shark group at some stage lost the ability to make bone, and their skeletons are made of cartilage. Cartilage is what we call "gristle" and in humans it makes the ears, nose and much of the skeletons of babies.
Sharks have no swim bladder and must swim perpetually to keep from sinking to the bottom. |
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Earth Earlier Earlier 390 Million Years ago Later Earth After Animals Later |
Biological Environment > Sharks |
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Basic Information |
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