An autotroph is an organism identified as a producer on the primary level of a food chain. Only about 5% of all living organisms are autotrophs. They are often referred to as self-feeders. In fact, the Greek origin of the term autos and trophe can be translated as "self-nourishing". They are able to form nutritional organic substances form inorganic substances such as carbon dioxide. It produces complex organic compounds such as fats, proteins, and carbohydrates. It will produce these from substances present in the autotroph's surroundings using the process of photosynthesis, obtaining energy from light; or through chemosynthesis, using energy from inorganic chemical reactions. The chemical reactions are usually between hydrogen sulfide/methane with oxygen.
Autotrophs do not need organic carbon or a living energy source survive. They are known to reduce carbon dioxide to make organic compounds for biosynthesis. In addition, autotrophs can store chemical energy. Autotrophs commonly use water as the reducing agent, but there are those that use other hydrogen compounds such as hydrogen sulfide.
Autotrophs can be photoautotrophs or chemoautotrophs. Photoautotrophs use light as an energy source. The chemoautotrophs use electron donors from organic or inorganic sources as a source of energy. The electron donors come from inorganic chemical sources such as hydrogen sulfide, elemental sulfur, ammonium and ferrous iron. In the food chain, autotrophs are consumed by heterotrophs.
1. Green plants and algae: These are examples of photoautotrophs using light as an energy source. In this type, electromagnetic energy is converted from sunlight into chemical energy in the form of reduced carbon. Green plants and algae are fundamental to the food chains of all ecosystems in the world. They are primary producers in food chains.
2. Iron bacteria: This is an example of a chemoautotroph, and receive their energy from the oxidation or breakdown of various organic or inorganic food substances in their environment. Iron bacteria is a specific example of this type of autotroph. They are commonly found in soil and rivers, as well as other iron-rich areas such as groundwater sources.
3. Sulfur bacteria: Another kind of chemoautotroph living mainly in pyrite deposits. It is converted to sulfuric acid as they consume sulfur. They are also capable of using iron as an energy source like in iron bacteria. The problems they can cause include corroding metal water pipes and an increase in the acidity of water sources.
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