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The challenge for abiogenesis (origin of life) [7] [8] [9] researchers is to explain how such a complex and tightly interlinked system could develop by evolutionary steps, as at first sight all its parts are necessary to enable it to function. For example, a cell, whether the LUCA or in a modern organism, copies its DNA with the DNA polymerase ...
The generally accepted parts of modern cell theory include: All known living things are made up of one or more cells [13] All living cells arise from pre-existing cells by division. The cell is the fundamental unit of structure and function in all living organisms. [14] The activity of an organism depends on the total activity of independent ...
In a way, these modern treatments attempt to keep panspermia as a contributing factor to abiogenesis, as opposed to a theory that directly opposes it. In line with this, it is suggested that if biosignatures could be detected on two (or more) adjacent planets, that would provide evidence that panspermia is a potentially required mechanism for ...
Spontaneous generation, the first naturalistic theory of abiogenesis, goes back to Aristotle and ancient Greek philosophy, and continued to have support in Western scholarship until the 19th century. [15] The theory held that "lower" animals are generated by decaying organic substances.
One partner of this symbiosis is proposed to be a bacterial cell, and the other an archaeal cell. It is postulated that this symbiotic partnership progressed via the cellular fusion of the partners to generate a chimeric or hybrid cell with a membrane bound internal structure that was the forerunner of the nucleus. The next stage in this scheme ...
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 ...
If their reproductive success is enhanced by having, say, equal numbers in each cell, and reproduction occurs by division in which each of various types of molecules are randomly distributed among the "children", the process of selection will promote such equal representation in the cells, even though one of the molecules may have a selective ...
Mitotic cell division enables sexually reproducing organisms to develop from the one-celled zygote, which itself is produced by fusion of two gametes, each having been produced by meiotic cell division. [5] [6] After growth from the zygote to the adult, cell division by mitosis allows for continual construction and repair of the organism. [7]