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Lec16 Biogeochemical Cycles

Lec16 Biogeochemical Cycles - The Water Planet...

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The Water Planet Biogeochemical Cycles Yair Rosenthal
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Cyclic transfer of chemical constituents in the environment
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Biogeochemical cycles Recall: All matter cycles...it is neither created nor destroyed... As the Earth is essentially a closed system with respect to matter, we can say that all matter on Earth cycles . Biogeochemical cycles: describe the movement (or cycling) of matter/elements within and among Earth’s systems.
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A typical carbohydrate CH 2 O But it contains other essential element
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The periodic table of elements
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Biologically important elements The big six - H, C, O, N, P, S macronutrients - required for metabolic processes in large amounts micronutrients - required in small amounts examples : Ca, Si- “structure elements” Na, K, Fe - important for physiological processes Biolimiting elements - found in low abundance in the environment
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Toxic elements Some elements can be toxic even at very low concentration (e.g., mercury). Others, like copper (Cu) and selenium (Se), are required in metabolic processes in low concentrations, but can be toxic at high concentrations.
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Selenium requirement Selenium deficiency Selenium deficiency is linked to Keshan Disease. The most common signs of selenium deficiency seen in Keshan Disease are an enlarged heart and poor heart function. Keshan disease has been observed in low-selenium areas of China, where dietary intake is less than 19 mg per day for men and less than 13 mg per day for women. This intake is significantly lower than the current RDA for selenium.
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