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Most water in Earth's atmosphere and crust comes from saline seawater, while fresh water accounts for nearly 1% of the total. The vast bulk of the water on Earth is saline or salt water, with an average salinity of 35‰ (or 3.5%, roughly equivalent to 34 grams of salts in 1 kg of seawater), though this varies slightly according to the amount of runoff received from surrounding land.
An essential amino acid is an amino acid that is required by an organism but cannot be synthesized de novo by it, and therefore must be supplied in its diet. Out of the twenty standard protein-producing amino acids, nine cannot be endogenously synthesized by humans: phenylalanine , valine , threonine , tryptophan , methionine , leucine ...
While the majority of Earth's surface is covered by oceans, those oceans make up just a small fraction of the mass of the planet. The mass of Earth's oceans is estimated to be 1.37 × 10 21 kg, which is 0.023% of the total mass of Earth, 6.0 × 10 24 kg.
Carbonic anhydrase, an enzyme that requires zinc (gray sphere near the center of this image), is essential for exhalation of carbon dioxide.. In the context of nutrition, a mineral is a chemical element.
The Encyclopedia of Earth (abbreviated EoE) is an electronic reference about the Earth, its natural environments, and their interaction with society.The Encyclopedia is described as a free, fully searchable collection of articles written by scholars, professionals, educators, and other approved [who?] experts, who collaborate and review each other's work.
The water, energy and food security nexus according to the Food And Agriculture Organisation of the United Nations (FAO), means that water security, energy security and food security are very much linked to one another, meaning that the actions in any one particular area often can have effects in one or both of the other areas.
The elevation of the land surface varies from a low point of −418 m (−1,371 ft) at the Dead Sea, to a maximum altitude of 8,848 m (29,029 ft) at the top of Mount Everest. The mean height of land above sea level is about 797 m (2,615 ft). [109] Land can be covered by surface water, snow, ice, artificial structures or vegetation.
The abyssopelagic zone is the portion of the ocean deeper than about 4,000 m (13,000 feet) and shallower than about 6,000 m (20,000 feet). The zone is defined mainly by its extremely uniform environmental conditions, as reflected in the distinct life forms inhabiting it. [ 8 ]