The Impact Of Domestication On Human Health

ADVANTAGES

appeared in the Mesozoic and required oxygen to form calcium carbonate. They became so abundant in the high oxygen of the late Cretaceous that the rain of their bodies on ocean floors gave the its name: chalk (the Latin name). Calcium carbonate, the primary constituent of limestone, comes in two forms: and . The magnesium content in the oceans, as well as the ocean temperature, determines which form of calcium carbonate will dominate. The also marked the end of a 100-million-year ice age and gave way to about 200 million years of hot times. During , Earth has . That pattern also seems . Hot seas are generally and cold seas are usually . Calcite seas create , which influence the biome that forms. The and periods had vast carbonate hardgrounds, which disappeared during the and returned in the Greenhouse Earth age of dinosaurs, becoming common in the Jurassic. Today’s Icehouse Earth has aragonite seas, so organisms that form calcium carbonate shells use aragonite, which is less stable than calcite and its formation is sensitive to temperature and acidity. Coral reefs, key phytoplankton (which help produce Earth’s oxygen), and shellfish use aragonite today to form their shells. There is already that acidification of the oceans due to humanity’s burning of fossil hydrocarbon deposits to power the industrial age is interfering with the ability of coral, carbonate-forming phytoplankton, and shellfish to form their shells. That is only one of the industrial age’s many deleterious ecosystem impacts. The current aragonite-formation situation is not a theoretical construct of fearful environmentalists, but is a .

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