Origin of life
An early question that needs to be confronted, indeed a question that in the last analysis requires definition, is: What is life. Most biologists would agree that self-replication, genetic continuity, is a fundamental trait of the life process. Systems that generally would be deemed nonbiological can exhibit a sort of self-replication, however. Examples would be the growth of a crystal lattice or a propagating clay structure. Crystals and clays propagate, unquestionably, but life they are not. There is no locus of genetic continuity, no organism. Such systems do not evolve, do not change in genetic ways to meet new challenges. Consequently, the definition of life should include the capacity for evolution as well as self-replication. Indeed, the mechanism of evolution---natural selection---is a consequence of the necessarily competing drives for self-replication that are manifest in all organisms. The definition based on those processes, then, would be that life is any self-replicating, evolving system (Norman R Pace 2001).[1]
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Pre-replicator chemical evolution
Pre-biotic pre-replicator chemical evolution as prelude to origin of living systems. See, for example:
Also:
- Danchin 2007[5]
- Sayer 2006[6]
- Deamer 2006[7]
- Szathmary 2006[8]
The first replicators
Sources of energy
Community metabolism
Coding for amino acids
The RNA World
Rampant horizontal gene transfer hypothesis
RNA to DNA transition
Emergence of Darwinian struggle
Emergence of cells
Oldest fossils
References
Citations
- ↑ The universal nature of biochemistry
- ↑ Dyson F (1982) A model for the origin of life. See Dyson (1982) J Mol Evol 18:344-350
- ↑ Post RL. (1990) The origin of homeostasis in the early earth. Journal of Molecular Evolution 31:257-64 Summary and Link to Full-Text.
- ↑ Galimov EM. (2004) Phenomenon of life: between equilibrium and non-linearity. Orig.Life Evol Biosph. 34:599-613.
- ↑ Danchin A, Fang G, Noria S. (2007) The extant core bacterial proteome is an archive of the origin of life. Proteomics 7:875-889 PMID 17370266
- ↑ Sayer RM. (2006) Self-organizing proto-replicators and the origin of life. Biosystems PMID 17014952
- ↑ Deamer D, Singaram S, Rajamani S, Kompanichenko V, Guggenheim S. (2006) Self-assembly processes in the prebiotic environment. Philos Trans R Soc Lond B Biol Sci 361:1809-1818 PMID 17008220
- ↑ Szathmary E. (2006) The origin of replicators and reproducers. Philos Trans R Soc Lond B Biol Sci 361:1761-1776 PMID 17008217
External links
Further reading
- Goldenfeld N Woese C (2007) Essays: Connections. Biology's next revolution The emerging picture of microbes as gene–swapping collectives demands a revision of such concepts as organism, species and evolution itself. Nature 445:369 (25 January 2007) doi:10.1038/445369a
- Forterre P (2006) Three RNA cells for ribosomal lineages and three DNA viruses to replicate their genomes: A hypothesis for the origin of cellular domain PNAS 103:3669-3674