Actual evapotranspiration is the water annually transpired by plants and

Actual evapotranspiration is the water annually

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Actual evapotranspiration is the water annually transpired by plants and evaporated from a landscape. Concept 55.3 Energy transfer between trophic levels is typically only 10% efficient Secondary production of an ecosystem is the amount of chemical energy in food converted to new biomass during a given period of time. Production Efficiency When a caterpillar feeds on a leaf, only about one-sixth of the leaf’s energy is used for secondary production. An organism’s production efficiency is the fraction of energy stored in food that is not used for respiration. Production efficiency= net secondary production x 100%/ assimilation of primary production Trophic Efficiency and Ecological Pyramids Trophic efficiency is the percentage of production transferred from one trophic level to the next. Trophic efficiency is multiplied over the length of a food chain. Approximately 0.1% of chemical energy fixed by photosynthesis reaches a tertiary consumer. A pyramid of net production represents the loss of energy with each transfer in a food chain. In a biomass pyramid, each tier represents the dry weight of all organisms in one trophic level. Most biomass pyramids show a sharp decrease at successively higher trophic levels. Certain aquatic ecosystems have inverted biomass pyramids: producers (phytoplankton) are consumed so quickly that they are outweighed by primary consumers. Turnover time is a ratio of the standing crop biomass to production. Turnover time = standing crop (g/m^2)/ production (g/m^2 x day) The dynamics of energy flow in ecosystems have important implications for the human population. o Eating meat is a relatively inefficient way of tapping photosynthetic production. o Worldwide agriculture could feed many more people if humans ate only plant material. Concept 55.4 Biological and geochemical processes cycle nutrients and water in ecosystems Life depends on recycling chemical elements. Nutrient circuits in ecosystems involve biotic and abiotic components and are often called biogeochemical cycles. Biogeochemical Cycle Gaseous carbon, oxygen, sulfur, and nitrogen occur in the atmosphere and cycle globally.
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Less mobile elements such as phosphorus, potassium, and calcium cycle on a more local level. A model of nutrient cycling includes main reservoirs of elements and processes that transfer elements between reservoirs. All elements cycle between organic and inorganic reservoirs. The Water Cycle Water is essential to all organisms. 97% of the biosphere’s water is contained in the oceans, 2% is in glaciers and polar ice caps, and 1% is in lakes, rivers, and groundwater. Water moves by the processes of evaporation, transpiration, condensation, precipitation, and movement through surface and groundwater. The Carbon Cycle Carbon-based organic molecules are essential to all organisms. Carbon reservoirs include fossil fuels, soils and sediments, solutes in oceans, plant and animal biomass, and the atmosphere. CO 2 is taken up and released through photosynthesis and respiration; additionally, volcanoes and the burning of fossil fuels contribute CO 2 to the atmosphere.
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