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Unformatted text preview: U n i t y o f L i f e All lifeforms on Earth have a common system. Examples: universal usage of DNA to store genetic information the ribosome technique of protein synthesis proteins serve as enzymes and catalysts the same 20 amino acids are always used, and only left-handed ones a universal genetic code DNA triplets coding for same amino acid the use of proteins and lipids to make membranes the use of the ATP-ADP cycle for chemical energy. The subsystems of life are highly interlocked. Proteins are needed to make enzymes, yet enzymes are needed to make proteins. Nucleic acids are needed to make proteins, yet proteins are needed to make nucleic acids. The common system is very complex. It must have been the result of an extended evolution. In evolutionary terms, it is very far from the original organisms. It is possible to construct detailed phylogenetic trees based either on morphology or molecular (genetic) data. Conclusion: It must be that all organisms on Earth are descended from a single common ancestor. Lattimer, AST 248, Lecture 12 p.1/9 P h y l o g e n y a n d t h e N a t u r e o f t h e C o m m o n A n c e s t o r Evolutionary distance = fractional genetic difference between organisms Phylogenetic tree = map of evolutionary diversification Three primary groupings or domains: Archaea Bacteria Eucarya Most deeply diverging lineages in Bacteria and Archaea are thermophiles, suggesting that the common ancestor of all life was also. Metabolize compounds rich in H, S and Fe Utilize anaerobic (sulfur) photosyn- thesis to synthesize carbohydrates 2H 2 S + CO 2 CH 2 O + 2S + H 2 O and fermentation for respiration (energy release) 2(CH 2 O) n nCH 4 + nCO 2 + energy Thrive in oxygen- and sunlight-free environments, like hydrothermal vents Eric Gaba, NASA Astrobiology Institute Lattimer, AST 248, Lecture 12 p.2/9 E...
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- Spring '08