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- Abiogenesis theory is the theory that all life started from inorganic molecules, which recombined in different ways due to energy input. These different forms eventually formed a self-replicating molecule, which may have used the other molecules produced by abiogenesis to start creating the basic structures of life, such as the cell.
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Apr 28, 2017 · Abiogenesis is the creation of organic molecules by forces other than living organisms. While organisms can create carbon-carbon bonds relatively easily thanks to enzymes, to do so otherwise requires large inputs of energy.
One model of abiogenesis is the " primitive Earth " model. This model proposes that life emerged on Earth through the gradual synthesis of organic molecules from inorganic precursors.
- Overview
- The Oparin-Haldane theory
- The Miller-Urey experiment
- Modern conceptions of abiogenesis
abiogenesis, the idea that life arose from nonlife more than 3.5 billion years ago on Earth. Abiogenesis proposes that the first life-forms generated were very simple and through a gradual process became increasingly complex. Biogenesis, in which life is derived from the reproduction of other life, was presumably preceded by abiogenesis, which became impossible once Earth’s atmosphere assumed its present composition.
Although many equate abiogenesis with the archaic theory of spontaneous generation, the two ideas are quite different. According to the latter, complex life (e.g., a maggot or mouse) was thought to arise spontaneously and continually from nonliving matter. While the hypothetical process of spontaneous generation was disproved as early as the 17th century and decisively rejected in the 19th century, abiogenesis has been neither proved nor disproved.
In the 1920s British scientist J.B.S. Haldane and Russian biochemist Aleksandr Oparin independently set forth similar ideas concerning the conditions required for the origin of life on Earth. Both believed that organic molecules could be formed from abiogenic materials in the presence of an external energy source (e.g., ultraviolet radiation) and that the primitive atmosphere was reducing (having very low amounts of free oxygen) and contained ammonia and water vapour, among other gases. Both also suspected that the first life-forms appeared in the warm, primitive ocean and were heterotrophic (obtaining preformed nutrients from the compounds in existence on early Earth) rather than autotrophic (generating food and nutrients from sunlight or inorganic materials).
Oparin believed that life developed from coacervates, microscopic spontaneously formed spherical aggregates of lipid molecules that are held together by electrostatic forces and that may have been precursors of cells. Oparin’s work with coacervates confirmed that enzymes fundamental for the biochemical reactions of metabolism functioned more efficiently when contained within membrane-bound spheres than when free in aqueous solutions. Haldane, unfamiliar with Oparin’s coacervates, believed that simple organic molecules formed first and in the presence of ultraviolet light became increasingly complex, ultimately forming cells. Haldane and Oparin’s ideas formed the foundation for much of the research on abiogenesis that took place in later decades.
In 1953 American chemists Harold C. Urey and Stanley Miller tested the Oparin-Haldane theory and successfully produced organic molecules from some of the inorganic components thought to have been present on prebiotic Earth. In what became known as the Miller-Urey experiment, the two scientists combined warm water with a mixture of four gases—water ...
Modern abiogenesis hypotheses are based largely on the same principles as the Oparin-Haldane theory and the Miller-Urey experiment. There are, however, subtle differences between the several models that have been set forth to explain the progression from abiogenic molecule to living organism, and explanations differ as to whether complex organic molecules first became self-replicating entities lacking metabolic functions or first became metabolizing protocells that then developed the ability to self-replicate.
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The habitat for abiogenesis has also been debated. While some evidence suggests that life may have originated from nonlife in hydrothermal vents on the ocean floor, it is possible that abiogenesis occurred elsewhere, such as deep below Earth’s surface, where newly arisen protocells could have subsisted on methane or hydrogen, or even on ocean shores, where proteinoids may have emerged from the reaction of amino acids with heat and then entered the water as cell-like protein droplets.
Some scientists have proposed that abiogenesis occurred more than once. In one example of this hypothetical scenario, different types of life arose, each with distinct biochemical architectures reflecting the nature of the abiogenic materials from which they developed. Ultimately, however, phosphate-based life (“standard” life, having a biochemical architecture requiring phosphorus) gained an evolutionary advantage over all non-phosphate-based life (“nonstandard” life) and thereby became the most widely distributed type of life on Earth. This notion led scientists to infer the existence of a shadow biosphere, a life-supporting system consisting of microorganisms of unique or unusual biochemical structure that may have once existed, or possibly still exists, on Earth.
As the Miller-Urey experiment demonstrated, organic molecules can form from abiogenic materials under the constraints of Earth’s prebiotic atmosphere. Since the 1950s, researchers have found that amino acids can spontaneously form peptides (small proteins) and that key intermediates in the synthesis of RNA nucleotides (nitrogen-containing compounds [bases] linked to sugar and phosphate groups) can form from prebiotic starting materials. The latter evidence may support the RNA world hypothesis, the idea that on early Earth there existed an abundance of RNA life produced through prebiotic chemical reactions. In fact, in addition to carrying and translating genetic information, RNA is a catalyst, a molecule that increases the rate of a reaction without itself being consumed, meaning that a single RNA catalyst could have produced multiple living forms, which would have been advantageous during the rise of life on Earth. The RNA world hypothesis is one of the leading self-replication-first conceptions of abiogenesis.
- Kara Rogers
Jun 4, 2019 · Abiogenesis is the natural process by which living organisms arose from nonliving organic molecules. Simple elements combined to form compounds; the compounds became more structured and involved different substances. Eventually, simple organic compounds were formed and linked to produce complex molecules such as amino acids.
- Bert Markgraf
In this article, we'll examine scientific ideas about the origin of life on Earth. The when of life's origins ( 3.5 billion years ago or more) is well-supported by fossils and radiometric dating. But the how is much less understood.
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- Do you believe that the diversity we see around us comes from a single ‘origin of life’ event or mul...All life on earth appears to be related — this is based on the presence of ancient genes that are found in (essentially) all living organisms. This...
- Does it mean that DNA is the evolution of RNA? Is it possible that Panspermia and Abiogenesis happen...Hi, Bintia and thank you for your questions. DNA evolved from RNA, that's our current belief. When i was a student i was constantly searching for s...
- So how exactly, do the inorganic elements on early Earth turn into the organic maters that are the b...The amino acids that are the base building blocks of life are simple to make. In the 1950's scientists combined ammonia, hydrogen, methane, and wat...
- Why is it that the RNA world hypothesis is more favored over the Metabolism-first hypothesis? (In ot...I assume that's because RNA molecules have many abilities and in general have more diverse functions than proteins. RNA can be a genetic molecule (...
- This is so confusing!!i know it may look confusing but its how life works.Life keeps going and going and soon we have the animals today and cells help all life stay alive
- Since there is so much diversity on Earth,is it more or less likely to have an ‘origin of life’ even...We think that any newly originated organism (or proto- organism) would be very unsophisticated and unlikely to survive competition with existing or...
- How is it that the RNA World hypothesis is still being considered? See this article from retraction ...A quick search of pubmed for the phrase "RNA world" finds 914 papers: https://www.ncbi.nlm.nih.gov/pubmed/?term=%22RNA+world%22 Why do you think re...
- the cell theory states that cells are formed from pre-existing cells so does abiogenesis go against ...It doesn't go against it. It simply covers something that cell theory doesn't, how primitive cells formed from non-cellular material.
- How do stromatolites differ from fossils of actual microbes?Stromatolites are buildups of compounds secreted from bacteria. Fossils of microbes would be microbes themselves, not evidence of them.
Study with Quizlet and memorize flashcards containing terms like Spontaneous Generation: inanimate objects creating __________________ objects, To get from no life to life, there had to be several steps. List the steps: monomers, What was different about the primitive earth's atmosphere? and more.
Jun 4, 2017 · Evidence for Abiogenesis. Abiogenesis is the theory that life comes from non-living things. Spontaneous generation was an early model for abiogenesis developed by Aristotle (384-322 BCE) which said that flies formed directly from decaying material and logs gave rise to crocodiles.
