Prof. Turner The Earth Transformed 9.6.07 I) Biosphere a Coined by Edward Suess b Boundaries defined by V. Vernadsky c The portion of earth and atmosphere that sustains life; a thin envelope for life, composed of the near subsurface, surface and lower atmosphere d Earth system includes biosphere e Only biophysical condition that can sustain life as we know it (i) Biosphere sustained by the flow of energy and matter, and the cycling (biogeochemical cycles) of chemical elements or molecules through the earth system (ii) These flows & cycles (use flow to refer to both) involve terrestrial • [Ex. Hydrologic cycle] (iii) Biogeochemical cycles have sinks – stores the element for long periods of time (iv) Flows & cycling maintain balances (amount in each portion of the earth system) that render biosphere as we know it (e.g. climate) • Natural variation (e.g. ice ages) • Human interference (v) Major cycles: C, N, S, H 2 O f Inter-tropical convergent zone
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