0 OCEAN LITERACY Essential Principles & Fundamental Concepts of Ocean Science PRINCIPLE 4

1 REVISION HISTORY DateVersionRevised ByDescription Aug 25, VLOriginal

2 ESSENTIAL PRINCIPLE 4 4 The ocean makes Earth habitable.

3 4 | THE OCEAN MAKES EARTH HABITABLE 4(a) Most of the oxygen in the atmosphere originally came from the activities of photosynthetic organisms in the ocean. Atmospheric Oxygen From Oceanic Organisms Most of the atmospheric oxygen originally came from photosynthetic organisms in the ocean such as the blue-green bacteria and other plant life. Photosynthesis is the process by which organisms (e.g. blue-green bacteria, green algae, and plants) use carbon dioxide, water and sunlight to produce carbohydrates and oxygen.

4 4 | THE OCEAN MAKES EARTH HABITABLE 4(b) The first life is thought to have started in the ocean. The earliest evidence of life is found in the ocean. Pre-Cambrian – 4,500 MYA To 543 MYA By examining some of the oldest sedimentary rocks on Earth, scientists have concluded that life on Earth started in the ocean. The oldest fossils date to roughly 3,500 MYA and consist of blue- green bacteria. In fact, all life on Earth for the next 1,000 million years was probably bacterial. By about 2,500 MYA, abundant fossils of living organisms, mostly blue-green bacteria, can be found. Then, about 1,800 MYA, simple eukaryotic cells (cells with a nucleus) started appearing.