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Time Scale of Life on Earth
- Earth formed ~4.6BYA
- Oldest living fossils (stromalites) are 3.5BYA
- Earliest life forms evolved in anoxinc environment ~3.8BYA
- Probionts-precell without all final characteristics. composed of RNA surrounded by liposome
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Stanley Miller et al.
- 1950's: Tried to make bldg blocks from proposed earth components (H2, H20, CH4, NH4)
- Added heat & electrical discharge. Generated AA's
- Other experiments using HCN. Different starting material made sugars, nt's, and lipids
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Spontaneous Developement of other Cellular Components
- Clay or Fe2S surfaces catalyze formation and growth of lipids vesicles (which encapsulate RNA
- Early fueling systems used FeS, H2S, H2
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RNA World model (Walli Gilbert)
- Early life forms based on activities of RNA
- RNA can direct nt synthesis, self replicate, catalyze polypeptide formation, serve regulatory function
- DNA (more stable) took over genomic role
- Proteins took over cellular functions
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Evolution of Eukaryotes
- 1-Celled eukaryotes arose 1.5-2 BYA
- Eukaryotic nucleus contain genes from bacteria and archae
- Either endosymbiosis or nuclear fusion from archae w/bacteria
- Endosymbiosis is favored model
- Mitochodria evolved from Alpha-proteobacteria
- Chloroplasts evolved from cyanobacteria related to prochlorococcus
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How Evolution Among Microbes is Studied
- Gene sequence (most prevalent) of SSU rRNA or housekeeping genes. Reflects evolutionary relationships
- Morphological analysis. in early stages and misleading
- Physiological and metabolic characteristics. can be misleading
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Genomic Fingerprinting
- Use of restriction enzymes and PCR to classify genomic characteristics w/out sequencing whole genomes
- can be used for ribosomal genes (ribotyping)
- housekeeping/non-ribosomal genees (RFLP, restriction fragment length polymorp
- Intergenic highly repetitive genetic sequences used to classify humans or organisms (Short Tandem Repeats)
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Phylogenetic Trees
- Demonstrate relationship of all the organisms together
- Distance between 2 organisms related to the degree of homology
- Probionts somewhere at root of tree
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Prokaryotic Diversity
- May be as many as 10 million prokaryotic species
- 8000 species characterized into 40 different phyla
- Most species cannot be cultivated in lab (~1%)
- Species may be comprised of many strands, and evolution quite rapid
- Horizontal transmission of genetic material
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Taxonomy
- Based on SSU gene sequence
- Names of orders (end in ales), familes (end in aceae)
- Biovars: Biological variance
- Morphovars: members of same species, with different morphology
- Serovars: subspecies classification based on antibody analysis
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Bergey's Manual of Analysis
- 24 bacterial and 2 archae phyla
- Gram (+) characterized based on their GC (nucleotide) contect
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