The interactions of these molecules would ha

The interactions of these molecules would ha - processes...

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The interactions of these molecules would ha ve increased as their concentrations increased. Reactions would have led to the building of larger, more complex molecules. A pre-cellular life would have began with the formation of nucleic acids . Chemicals made by these nucleic acids would have remained in proximity to the nucleic acids. Eventually the pre-cells would have been enclosed in a lipid-protein membrane, which would have resulted in the first cells. Biochemically, living systems are separated from other chemical systems by three things. 1. The capacity for replication from one generation to another. Most organisms today use DNA as the hereditary material, although recent evidence ( ribozymes ) suggests that RNA may have been the first nucleic acid system to have formed. Nobel laureate Walter Gilbert refers to this as the RNA world. Recent studies suggest a molecular 2. The presence of enzymes and other complex molecules essential to the
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Unformatted text preview: processes needed by living systems. Miller's experiment showed how these could possibly form. 3. A membrane that separates the internal chemicals from the external chemical environment. This also delimits the cell from not-cell areas. The work of Sidney W. Fox has produced proteinoid spheres, which while not cells, suggest a possible route from chemical to cellular life. Fossil evidence supports the origins of life on Earth earlier than 3.5 billion years ago. The North Pole microfossils from Australia, illustrated in Figure 4, are complex enough that more primitive cells must have existed earlier. From rocks of the Ishua Super Group in Greenland come possibly the earliest cells, as much as 3.8 billion years old. The oldest known rocks on Earth are 3.96 billion years old and are from Arctic Canada. Thus, life appears to have begun soon after the cooling of the Earth and formation of the atmosphere and oceans....
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