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The transition from non-life to life has never been observed experimentally, but many proposals have been made for different stages of the process. The study of abiogenesis aims to determine how pre-life chemical reactions gave rise to life under conditions strikingly different from those on Earth today.
A scenario is a set of related concepts pertinent to the origin of life (abiogenesis), such as the iron-sulfur world. Many alternative abiogenesis scenarios have been proposed by scientists in a variety of fields from the 1950s onwards in an attempt to explain how the complex mechanisms of life could have come into existence. These include ...
A proto-metabolism is a series of linked chemical reactions in a prebiotic environment that preceded and eventually turned into modern metabolism.Combining ongoing research in astrobiology and prebiotic chemistry, work in this area focuses on reconstructing the connections between potential metabolic processes that may have occurred in early Earth conditions. [1]
The human hepatic portal system delivers about three-fourths of the blood going to the liver.The final common pathway for transport of venous blood from spleen, pancreas, gallbladder and the abdominal portion of the gastrointestinal tract [2] (with the exception of the inferior part of the anal canal and sigmoid colon) is through the hepatic portal vein.
A grasshopper has an open circulatory system, where hemolymph moves through interconnected sinuses or hemocoels, spaces surrounding the organs. Above is a diagram of an open circulatory system. An open circulatory system is made up of a heart, vessels, and hemolymph.
The circulatory system uses the channel of blood vessels to deliver blood to all parts of the body. This is a result of the left and right sides of the heart working together to allow blood to flow continuously to the lungs and other parts of the body. Oxygen-poor blood enters the right side of the heart through two large veins.
In order to discuss abiological life inside stars, Luis Anchordoqui and Eugene Chudnovsky suggest three postulates which must be satisfied by any reasonable definition of life: [4] The ability to encode information; The ability of information carriers to self-replicate faster than they disintegrate
While there isn't one unifying theory of abiogenesis, there are several principles and competing hypotheses for how abiogenesis could have occurred, which are detailed in the article. Wikipedia describes the phenomenon of abiogenesis as a fact because the reliable sources from the peer-reviewed scientific literature describe it as a fact.