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1. There is only one ocean. It is divided into five different parts: the Pacific, Atlantic, Indian, Antarctic, and Arctic Oceans. There are also many other smaller seas, gulfs and bays which form part of them. Altogether they cover 75 percent of the earth′s surface. For centuries, people have been challenged by the mysteries that lie beneath the ocean. However, today′s   have overcome many of the challenges of the depth by using modern devices. They send submarines to investigate the seabed and bring samples of   life back to the surface for further study. Satellite photographs provide a wide range of information, including water temperature, depth and the undersea populations. If modern technology did not exist, we would never have such precious information.
Marine plants and animals fall into three major groups. Some of them live on or depend on the bottom like the starfish. Some are swimming animals such as fishes and   that move independently of water currents while others are tiny   that are carried along by the currents like the jellyfish. Plants and animals of the sea, however small or oversized, all contribute to its biodiversity. Unless this biodiversity were maintained, marine life would be at  .