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Many species of sharks give birth to a few dozen live young, others lay a similarly small number of eggs; these are often washed ashore and are known as [[mermaid]]'s purses.

Many species of sharks give birth to a few dozen live young, others lay a similarly small number of eggs; these are often washed ashore and are known as [[mermaid]]'s purses.

Sharks are reputed to be able to detect minute amounts of blood in water, and to be able to follow blood trails for miles. In fact, although sharks can detect blood at concentrations of as little as a few parts per billion, a very considerable quantity must be split before it is detectable amongst billions of gallons of seawater. Sharks actually use sounds and vibrations to locate most of their prey.

Sharks are reputed to be able to detect minute amounts of blood in water, and to be able to follow blood trails for miles. In fact, although sharks can detect blood at concentrations of as little as a few parts per billion, a very considerable quantity must be spilt before it is detectable amongst billions of gallons of seawater. Sharks actually use sounds and vibrations to locate most of their prey.

==Classification==

==Classification==