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| Our planet is made up of five great oceans — the Atlantic, the
Pacific, the Indian, the Arctic, and the Southern. They're all linked together, creating a huge body of
saltwater called the World Ocean that surrounds the continents and islands and covers about two-thirds of the Earth's surface.
Scientists know — from studying tiny fossils — that life on Earth probably started in the oceans nearly 4 billion years ago. For
most of Earth's history, life stayed and thrived in the oceans. About 500 million years ago, some living things, like our
ancestors, moved out of the water and on to land, but most life stayed in the oceans. |
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