Habitat and the food chain - Sea

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The sea, the world ocean, or simply the ocean, is the connected body of salty water that covers 70.8% of the Earth's surface. The sea moderates the Earth's climate and has important roles in the water cycle, carbon cycle, and nitrogen cycle. Although the sea has been travelled and explored since prehistory, the modern scientific study of the sea—oceanography—dates broadly to the British Challenger expedition of the 1870s.The sea is conventionally divided into four or five large sections, such as the Pacific, called oceans while smaller sections, such as the Mediterranean, are known as seas.The sea is an essential aspect of human trade, travel, mineral extraction, and power generation. This has also made it essential to warfare and left major cities exposed to earthquakes and volcanoes from nearby faults; powerful tsunami waves; and hurricanes, typhoons, and cyclones produced in the tropics. This importance and duality has affected human culture, from early sea gods to the epic..