![]() Microbial mat fossils have been found in 3.48 billion-year-old sandstone in Western Australia. The earliest undisputed evidence of life on Earth dates from at least 3.5 billion years ago, during the Eoarchean Era after a geological crust started to solidify following the earlier molten Hadean Eon. The Earth is about 4.54 billion years old. įurther information: Evolutionary history of life and Timeline of evolutionary history of life Enceladus, a small icy moon of Saturn, also has what appears to be an underground ocean which actively vents warm water from the moon's surface. There has been speculation Europa's ocean could support life, and could be capable of supporting multicellular microorganisms if hydrothermal vents are active on the ocean floor. This would make Europa's ocean over twice the volume of the Earth's ocean. ![]() It has been estimated the outer crust of solid ice is about 10–30 km (6–19 mi) thick and the liquid ocean underneath is about 100 km (60 mi) deep. There is a strong possibility a large saltwater ocean exists beneath its ice surface. Europa, one of the moons orbiting Jupiter, is slightly smaller than the Earth's moon. However water is found elsewhere in the solar system. Clarke has pointed out it would be more appropriate to refer to planet Earth as planet Ocean. By volume, the ocean provides about 90 percent of the living space on the planet. Jupiter's moon Europa may have an underground ocean which supports life.Īltogether the ocean occupies 71 percent of the world surface, averaging nearly 3.7 kilometres (2.3 mi) in depth. If all of Earth's crustal surface was at the same elevation as a smooth sphere, the depth of the resulting world ocean would be about 2.7 kilometres (1.7 mi). ![]() The world ocean covers an area of 3.618 ×10 8 km 2 with a mean depth of 3682 m, resulting in an estimated volume of 1.332 ×10 9 km 3. The mass of this world ocean is 1.35 ×10 18 metric tons, or about 1/4400 of Earth's total mass. Ĭonventionally the planet is divided into five separate oceans, but these oceans all connect into a single world ocean. Earth's hydrosphere consists chiefly of the oceans, but technically includes all water surfaces in the world, including inland seas, lakes, rivers, and underground waters down to a depth of 2,000 metres (6,600 ft) The deepest underwater location is Challenger Deep of the Mariana Trench in the Pacific Ocean, having a depth of 10,900 metres (6.8 mi). The abundance of surface water on Earth is a unique feature in the Solar System. Quantities in relation to 1 kg or 1 litre of sea water. The term marine comes from the Latin mare, meaning "sea" or "ocean".Ĭomposition of seawater. Marine life is studied scientifically in both marine biology and in biological oceanography. Marine microorganisms, including protists and bacteria and their associated viruses, have been variously estimated as constituting about 70% or about 90% of the total marine biomass. Marine species range in size from the microscopic like phytoplankton, which can be as small as 0.02 micrometres, to huge cetaceans like the blue whale – the largest known animal, reaching 33 m (108 ft) in length. More than 200,000 marine species have been documented, and perhaps two million marine species are yet to be documented. dolphins, whales, otters, and seals) need to surface periodically to breathe air. Fish have gills instead of lungs, although some species of fish, such as the lungfish, have both. Marine invertebrates exhibit a wide range of modifications to survive in poorly oxygenated waters, including breathing tubes as in mollusc siphons. Plankton forms the general foundation of the ocean food chain, particularly phytoplankton which are key primary producers. Plant forms such as kelp and other algae grow in the water and are the basis for some underwater ecosystems. One group of amphibians evolved into reptiles and mammals and a few subsets of each returned to the ocean as sea snakes, sea turtles, seals, manatees, and whales. Some of these evolved into amphibians, which spend portions of their lives in water and portions on land. The earliest vertebrates appeared in the form of fish, which live exclusively in water. By volume, oceans provide about 90% of the living space on the planet. Most life forms evolved initially in marine habitats. Marine life in part shape and protect shorelines, and some marine organisms even help create new land (e.g. Marine organisms, mostly microorganisms, produce oxygen and sequester carbon. ![]() At a fundamental level, marine life affects the nature of the planet. Marine life, sea life, or ocean life is the plants, animals and other organisms that live in the salt water of seas or oceans, or the brackish water of coastal estuaries.
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