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FLOWS OF ENERGY AND MATTER 2.3 Energy Budget: • Only a very small part of the total sunlight reaching the Earths surface is ever transformed into energy used by living organisms. • A study of an Illinois cornfield suggested only 1.6% was actually used by the corn. Boxes and Circles represent Storage and Arrow thickness represents magnitude of flow Pathways of radiation through ecosystem ■ Conversion of light energy to chemical energy ■ Transfer of chemical energy from one trophic level to another (efficiency varies) ■ Overall conversion of ultraviolet and visible light to heat energy by organisms in ecosystem ■ Re-radiation of heat energy to the atmosphere Energy currency: C-H bonds photosynthesis ■ 6𝐶𝑂2 + 6𝐻2 𝑂 + 𝑙𝑖𝑔ℎ𝑡 𝑒𝑛𝑒𝑟𝑔𝑦 → 𝐶6 𝐻12 𝑂6 𝑔𝑙𝑢𝑐𝑜𝑠𝑒 + 6𝑂2 respiration ■ 𝐶6 𝐻12 𝑂6 𝑔𝑙𝑢𝑐𝑜𝑠𝑒 + 6𝑂2 → 6𝐶𝑂2 + 6𝐻2 𝑂 + 𝑐ℎ𝑒𝑚𝑖𝑐𝑎𝑙 𝑒𝑛𝑒𝑟𝑔𝑦 Summary: ■ Energy is conserved in ecosystems – First law of Thermodynamics ■ Chemical energy used by “buffalo and bacteria” must be less than the chemical energy generated via primary production, due to unavoidable inefficiencies in energy capture. ■ Photosynthesis is the dominant source of energy in most ecosystems through conversion of light to C-H bonds in organic material. Summary: ■ The flow and fate of carbon is tightly linked to energy flow. ■ This fact is fundamental to understanding how carbon and energy flow are – linked to other elements and nutrients – support patterns of biodiversity – connect carnivores, herbivores, and plants Work Cited ■ Beman, J. (2010) Energy Economics in Ecosystems. Nature Education Knowledge 3(10):13