When it comes to creatures at the top of the food chain in the ocean , sharks are at the top. Sharks have a long history on Earth, dating back at least 420 million years, 100 to 200 million years earlier than dinosaurs! However, sharks have not changed much in appearance over the past few hundred million years, except for minor adjustments in their feeding structure and a more streamlined body shape, which have evolved to allow them to swim faster and hunt more efficiently. There are many types of sharks, and there are at least 440 species of sharks in the ocean. They vary greatly in shape and size. For example, the largest whale shark can be up to 18 meters long, as big as a bus, while the dwarf dogfish is only 20 centimeters long, about the same size as a crucian carp. Image source: National Maritime Museum official account |
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