They also communicate via body language by leaping, breaching, smacking their tails against the water, butting heads, and jaw-snapping. Communication helps dolphins coordinate their hunting techniques so that the whole pod catches food. Dolphins living in the open ocean often swim in tight circles around a school of fish and take turns dashing in to catch a bite. Closer to shore, dolphins often herd fish into shallow water, keeping them trapped while other group members feed. Oceans host more varied life forms than dry land environments.
Scientists classify organisms using a series of hierarchical categories called taxa.
The hierarchical system moves upward into larger and larger groups of organisms. Thirty-two of the world's 33 animal phyla are found in the oceans, while only 12 are found on land. Twenty-one of these phyla exist exclusively in the oceans, while only 1 is exclusive to land. Seawater is pumped into these tube feet, hydrostatically extending the feet. Some animals may have more than 2,000 tube feet.