Autotroph

 ( Trophic Ecology ) 

An autotroph is an organism that can convert abiotic sources of energy into energy stored in organic compounds, which can be used by Heterotroph. Autotrophs produce complex (such as , , and ) using carbon from simple substances such as carbon dioxide,Morris, J. et al. (2019). "Biology: How Life Works", 3rd edition, W. H. Freeman. generally Photosynthesis or Chemosynthesis. Autotrophs do not need a living source of carbon or energy and are the producers in a food chain, such as plants on land or algae in water. Autotrophs can Redox carbon dioxide to make organic compounds for biosynthesis and as stored chemical fuel. Most autotrophs use water as the reducing agent, but some can use other hydrogen compounds such as hydrogen sulfide.

The primary producers can convert the energy in the light (phototroph and photoautotroph) or the energy in inorganic chemical compounds (chemotrophs or chemolithotrophs) to build organic molecules, which is usually accumulated in the form of biomass and will be used as carbon and energy source by other organisms (e.g. heterotrophs and mixotrophs). The photoautotrophs are the main primary producers, converting the energy of the light into chemical energy through photosynthesis, ultimately building organic molecules from carbon dioxide, an inorganic carbon source. Examples of Lithoautotroph are some archaea and bacteria (unicellular organisms) that produce biomass from the oxidation of inorganic chemical compounds; these organisms are called , and are frequently found in hydrothermal vents in the deep ocean. Primary producers are at the lowest trophic level, and are the reasons why Earth sustains life to this day.

Autotrophs use a portion of the ATP produced during photosynthesis or the oxidation of chemical compounds to reduce NADP⁺ to NADPH to form organic compounds. Most chemoautotrophs are , using inorganic electron donors such as hydrogen sulfide, Hydrogen, elemental sulfur, ammonium and ferrous oxide as reducing agents and hydrogen sources for biosynthesis and chemical energy release. Chemolithoautotrophs are that synthesize energy through the oxidation of inorganic compounds. They can sustain themselves entirely on atmospheric CO₂ and inorganic chemicals without the need for light or organic compounds. They enzymatically catalyze redox reactions using mineral substrates to generate ATP energy. These substrates primarily include hydrogen, iron, nitrogen, and sulfur. Its ecological niche is often specialized to extreme environments, including deep marine hydrothermal vents, stratified sediment, and acidic hot springs.

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History The term autotroph was coined by the German botanist Albert Bernhard Frank in 1892. It stems from the ancient Greek word (), meaning "nourishment" or "food". The first autotrophic organisms likely evolved early in the Archean but proliferated across Earth's Great Oxidation Event with an increase to the rate of oxygenic photosynthesis by cyanobacteria. Photoautotrophs evolved from bacteria by developing photosynthesis. The earliest photosynthetic bacteria used hydrogen sulphide. Due to the scarcity of hydrogen sulphide, some photosynthetic bacteria evolved to use water in photosynthesis, leading to cyanobacteria.

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Variants Some organisms rely on as a source of carbon, but are able to use light or inorganic compounds as a source of energy. Such organisms are . An organism that obtains carbon from organic compounds but obtains energy from light is called a photoheterotroph, while an organism that obtains carbon from organic compounds and energy from the oxidation of inorganic compounds is termed a chemolithoheterotroph.

Evidence suggests that some fungi may also obtain energy from ionizing radiation: Such radiotrophic fungi were found growing inside a reactor of the Chernobyl nuclear power plant.

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Examples There are many different types of autotrophs in Earth's ecosystems. located in tundra climates are an exceptional example of a primary producer that, by mutualistic symbiosis, combines photosynthesis by algae (or additionally nitrogen fixation by cyanobacteria) with the protection of a decomposer fungus. As there are many examples of primary producers, two dominant types are coral and one of the many types of brown algae, kelp.

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Photosynthesis

Gross primary production occurs by photosynthesis. This is the main way that primary producers get energy and make it available to other forms of life. Plants, many corals (by means of intracellular algae), some bacteria (cyanobacteria), and algae do this. During photosynthesis, primary producers receive energy from the sun and use it to produce sugar and oxygen.

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Ecology

Without primary producers, organisms that are capable of producing energy on their own, the biological systems of Earth would be unable to sustain themselves. Plants, along with other primary producers, produce the energy that other living beings consume, and the oxygen that they breathe. It is thought that the first organisms on Earth were primary producers located on the ocean floor.

Autotrophs are fundamental to the food chains of all in the world. They take energy from the environment in the form of sunlight or inorganic chemicals and use it to create fuel molecules such as carbohydrates. This mechanism is called primary production. Other organisms, called , take in autotrophs as food to carry out functions necessary for their life. Thus, heterotrophs – all , almost all fungi, as well as most bacterium and protozoa – depend on autotrophs, or , for the raw materials and fuel they need. Heterotrophs obtain energy by breaking down carbohydrates or oxidizing organic molecules (carbohydrates, fats, and proteins) obtained in food. Carnivorous organisms rely on autotrophs indirectly, as the obtained from their heterotrophic prey come from autotrophs they have consumed.

Most ecosystems are supported by the autotrophic primary production of plants and cyanobacteria that capture initially released by the sun. Plants can only use a fraction (approximately 1%) of this energy for photosynthesis.

Sam H. Schurr (2011). 9781617260209 ISBN 9781617260209

The process of photosynthesis Water splitting (H₂O), releasing oxygen (O₂) into the atmosphere, and redox carbon dioxide (CO₂) to release the hydrogen atoms that fuel the metabolism process of primary production. Plants convert and store the energy of the photons into the chemical bonds of simple sugars during photosynthesis. These plant sugars are polymerization for storage as long-chain , such as starch and cellulose; glucose is also used to make and . When autotrophs are eaten by , i.e., consumers such as animals, the , , and contained in them become energy sources for the heterotrophs.

Brian S. Beckett (1981). 9780199140657, Oxford University Press. . ISBN 9780199140657

Proteins can be made using , , and in the soil.

Odum, Eugene P. (Eugene Pleasants), 1913-2002. (2025). 9780534420666, Thomson Brooks/Cole. ISBN 9780534420666

Gilbert M. Smith (2025). 9781406773156, Read Books. . ISBN 9781406773156

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Primary production in tropical streams and rivers

Aquatic algae are a significant contributor to food webs in tropical rivers and streams. This is displayed by net primary production, a fundamental ecological process that reflects the amount of carbon that is synthesized within an ecosystem. This carbon ultimately becomes available to consumers. Net primary production displays that the rates of in-stream primary production in tropical regions are at least an order of magnitude greater than in similar temperate systems.

(2025). 9780120884490 ISBN 9780120884490

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Origin of autotrophs

Researchers believe that the first cellular lifeforms were not heterotrophs as they would rely upon autotrophs since organic substrates delivered from space were either too heterogeneous to support microbial growth or too reduced to be fermented. Instead, they consider that the first cells were autotrophs. These autotrophs might have been Thermophile and anaerobic chemolithoautotrophs that lived at deep sea alkaline hydrothermal vents. This view is supported by phylogenetic evidencethe physiology and habitat of the last universal common ancestor (LUCA) is inferred to have also been a thermophilic anaerobe with a Wood-Ljungdahl pathway, its biochemistry was replete with FeS clusters and radical reaction mechanisms. It was dependent upon Fe, H₂, and CO₂. The high concentration of K⁺ present within the cytosol of most life forms suggests that early cellular life had Na⁺/H⁺ antiporters or possibly symporters. Autotrophs possibly evolved into heterotrophs when they were at low H₂ partial pressures where the first form of heterotrophy were likely amino acid and clostridial type purine fermentations. It has been suggested that photosynthesis emerged in the presence of faint near infrared light emitted by hydrothermal vents. The first photochemically active pigments are then thought to be Zn-tetrapyrroles.

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See also

• Electrolithoautotroph
• Electrotroph
• Heterotrophic nutrition
• Organotroph
• Primary nutritional groups

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External links

Categories: Trophic Ecology, Microbial Growth And Nutrition, Biology Terminology, Plant Nutrition

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