Many sharks gradually lost physical structures necessary for buccal pumping as they evolved. The spiracles of large, fast sharks shrank and disappeared as they evolved into sleek, modern predators. Ram ventilation is more energy-efficient than buccal breathing. The water flow as a shark swims uses less energy than pumping water into the mouth. Most modern shark species can alternate between buccal pumping and ram ventilation. The sand tiger shark alternates between breathing methods frequently because it hunts prey on the ocean floor and swimming through water.

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