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Early evolution of life on Earth. Wachtershauser. Miller and Urey experiment. Early catabolism. Evolution of cell types. Primitive Metabolism. Early catabolism must make use of chemical disequilibria Later, photosynthetic energetics may have evolved

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primitive metabolism
Primitive Metabolism
  • Early catabolism must make use of chemical disequilibria
  • Later, photosynthetic energetics may have evolved
    • First photosynthetics were undoubtedly anaerobic photosynthetic bacteria
    • Later, oxygenic photosynthesis changed the chemistry of the Earth
  • In addition to O2 being an electron acceptor for respiration, it caused development of an O3 layer
summary
Summary

First evidence for potential life 3.8 billion yrs ago

  • other fossil evidence
  • molecular fossils
  • chemolithotrophy vs heterotrophs, who came first?
  • anoxygenic photosynthesis
  • oxygenic photosynthesis
  • Banded iron formations (BIFs)-red beds
taxonomy
Taxonomy
  • Until recently, life on Earth in 5 kingdoms:
    • Bacteria
    • Fungi
    • Protists
    • Plants
    • Animals
  • Division between Bacteria, Archaea, and Eukarya more profound than former kingdoms: level called domains
taxonomic ranks
Taxonomic Ranks
  • Empire or Domain
  • Kingdoms (Bacteria and Eukarya not yet divided into kingdoms)
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species (name is binomial: genus + epithet)
bacterial taxonomy
Bacterial Taxonomy
  • Bacterial species is the base unit for taxonomy
    • Definition of any given species is subjective
    • >70% sequence similarity of genome
    • >98% sequence similarity of rRNA
    • Each species is phenotypically distinct
evolutionary chronometers
Evolutionary Chronometers
  • Phenotypic characteristics
  • Mole percent Guanine + Cytosine
  • DNA sequence similarity (gross sequence similarity)
    • Good at the species level
  • Small-subunit RNA (16S rRNA of prokaryotes; 18S of eukaryotes)
phenotypic taxonomies
Phenotypic Taxonomies
  • Phenotype determination is classic taxonomic method
  • Today more reliance on molecular methods for taxonomies above the genus level
    • Still, phenotypic differentiation is considered requirement for separation of species
  • Some methods collect large amounts of phenotypic data quickly
    • FAME analysis
    • Pyrolysis/GC
    • Automated testing of enzymatic activities
molecular microbial ecology
Molecular microbial ecology
  • Signature sequences identify phylogenetic groups
    • 16S & 18S sequences identify Bacteria, Archaea, and Eucarya
  • Probes can be developed for FISH (fluorescent in situ hybridization)