l18_productivity

l18_productivity - MIT Department of Biology 7.014...

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7.014 Handout P RODUCTIVITY : T HE “M ETABOLISM OF E COSYSTEMS Ecologists use the term “productivity” to refer to the process through which an assemblage of organisms (e.g. a trophic level or ecosystem assimilates carbon. Primary producers (autotrophs) do this through photosynthesis; Secondary producers (heterotrophs) do it through the assimilation of the organic carbon in their food. Remember that all organic carbon in the food web is ultimately derived from primary production. DEFINITIONS Primary Produc tivity : Rate of conversion of CO 2 to organic carbon (photosynthesis) per unit surface area of the earth, expressed either in terns of weight of carbon, or the equivalent calories -1 e.g., g C m -2 year -1 Kcal m -2 year Primary Produc tion : Same as primary productivity, but usually expressed for a whole ecosystem -1 e.g., tons year for a lake, cornfield, forest, etc. NET vs. GROSS: For plants: Some of the organic carbon generated in plants through photosynthesis (using solar
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This note was uploaded on 05/02/2009 for the course BIOL 7.014 taught by Professor Walker during the Spring '05 term at MIT.

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l18_productivity - MIT Department of Biology 7.014...

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