When Microbes Ruled the World
- OLDEST EVIDENCE OF LIFE
- Stromatolites@ 3500 MY
- Pilbara shield of Australia
- 3800 MY BIF's yield 12C :13C ratios similar to modern organisms
- Other fossil assemblages include:
- Fig Tree Chert (Pongola Super Group) -Barberton Mts - South Africa - 3000 MY BP
- Bulawayan Group - Rhodesia - 2800 MY BP
- Requirements for Life
- Protein synthesis from simple amino acids Nucleic acids
- Organic phosphorus compounds ADP/ATP
- "Cellular" membrane
- DeNovo Synthesis of Organic Molecules
- Synthesis of amino acids from Earth's "early atmosphere" in 1953 - Miller & Urey
- By 1968 biochemists had synthesized all amino acids, chlorophyll (mg-based molecule), and
variety of other organic molecules.
- Discovery of Protenoids
- Fox discovered amino acids in water can combine to form proteins in the presence of
phosphatic acid (70 C)
- Found adjacent to Hawaiian volcanic vents
- Cooling of proteinoids form microspheres
- Film-like outer wall, capable of dsmotic swelling & shrinking;
- Exhibit budding (asexual reproduction)
- Divide into daughter microspheres
- Aggregate into filaments
- Extraterrestrial Life?
- Carbonaceous chondrite known as the Murchison meteor (Australia, 1969)
- Amino acids & organic molecules identified
- 12C :13C ratio greater than present life on Earth.
- Early Life Strategies
- Autotroph (self-generating food)
- Heterotroph (unable to produce own food supply)
- Lab produced ATP from heating gasses
- Probably available in the Archean.
- Early Life Strategies 2
- Chemosynthetic bacteria
- Fermentation (disassemble organic molecules to release energy)
- Sulfate-reducing bacteria (sulfur-source)
- Archaebacterial methanogens (methane- source; first discovered 1978).
- Evolution of facultative photoautotrophs (cyanobacteria) sometime in Archean
- Free O2 could be released into the atmosphere
- Earliest Fossils
- Stromatolites of the Warrawoona Group, Pilbara Shield (Australia)
- Spheroidal microfossils (17- 20m in diameter)
- Filamentous forms
- 12C :13C ratio provides evidence of biological fixation of CO2 by photosynthesis.
- Attributed to prokaryotes.
- Stromatolites Defined
- Stromatolites are laminar, organic sedimentary structures formed by trapping of sedimentary
clasts and precipitation of CaCO3 in response to metabolic activities.
- Prokaryotes vs Eukaryotes
- Prokaryotes
- No nuclear membrane
- Nucleic acids only
- Dispersed chlorophyll
- Only ribosomes
- Muramic acid cell wall
- Eukaryotes
- Nuclear membrane
- Nucleic acids and proteins
- Chlorophyll concentrated in a specific organelle
- Complement of internal organelles
- Complex organic wall
- Symbiotic Theory of Eukaryotes
- Eukaryoticarose from symbiotic relationship between prokaryotes
- Membrane-bound organelles once autonomous prokaryotes
- Host cell became dependent upon the relationship and necessary for continued existence.
- Evidence for Symbiotic Theory
- Mitochondria & chloroplasts have capability of semi-autonomous growth & division
- Arise from pre-existing mitochondria or chloroplasts
- Both possess own DNA & RNA, both of which can be synthesized & replicated within the
organelle
- Both capable of building proteins from amino acids
- Ribosomes of chloroplasts and mitochondria are of the prokaryotic type