Photosynthesis and chemosynthesis Both processes by which organisms produce food; photosynthesis is powered by sunlight while chemosynthesis runs on chemical energy. Ecosystems depend upon the ability of some organisms to convert inorganic compounds into food that other organisms can then exploit (or eat!). In most cases, primary food production occurs in a process called photosynthesis, which is powered by sunlight. In a few environments, primary production happens though a process called chemosynthesis, which runs on chemical energy. Together, photosynthesis and chemosynthesis fuel all life on Earth. Photosynthesis occurs in plants and some bacteria, wherever there is sufficient sunlight – on land, in shallow water, even inside and below clear ice. All photosynthetic organisms use solar energy to turn carbon dioxide and water into sugar and oxygen. There is only one photosynthetic formula: CO2 + 6H2O -> C6H12O6 + 6O2. Chemosynthesis is the use of energy released by inorganic chemical reactions to produce food. Chemosynthesis is at the heart of deep-sea communities, sustaining life in absolute darkness, where sunlight does not penetrate. All chemosynthetic organisms use the energy released by chemical reactions to make a sugar, but different species use different pathways. For example, the most extensive ecosystem based on chemosynthesis lives around undersea hot springs. At these hydrothermal vents, vent bacteria oxidize hydrogen sulfide, add carbon dioxide and oxygen, and produce sugar, sulfur, and water: CO2 + 4H2S + O2 -> CH20 + 4S + 3H2O. Other bacteria make organic matter by reducing sulfide or oxidizing methane. Chemosynthetic bacterial communities have been found in hot springs on land and on the seafloor around hydrothermal vents, cold seeps, whale carcasses, and sunken ships.
Posted on: Sat, 07 Sep 2013 01:50:18 +0000
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