California
State University Long Beach
GEOL 300i; Earth Systems and Global Change
Lecture 10
Fossil Evidence for Timing Life
- Stromatolites in carbonate sediments
- Cyanobacteria or blue-green algae
- Oldest are 3.4 - 3.5 Ga (Archean)
- Abundant in rocks 2.8 - 3 Ga (Proterozoic)
- Algal filament fossils found in chert
- 3.5 Ga at North Pole, western Australia
- Spheroidal bacterial structures (Monera)
- Prokaryotic cells; cell division?
- 3.0 - 3.1 Ga
- Fig Tree Group, South Africa
Chemical Development of Prebiotic Organic Compounds -How?
- Simulation experiments; building blocks from the primordial soup
- Miller and Urey formed amino acids
- Gaseous H2, CH4 (methane), NH3(ammonia), H2O(steam)
- Sparks (simulate atmospheric lightning)
- Oparin and Fox formed protobionts, proteinoids, & microspheres
- Also called coacervate droplets
- Mimic cell behavior, but non-living
- Bada and Miller's sub-ice organic gaspacho theory
- Amino acids of extraterrestrial origin
o Carbonaceous chondrite meteorites
??span style='font:7.0pt "Times New Roman"'> Murchison Meteorite, Australia
??span style='font:7.0pt "Times New Roman"'> Contains organic compounds, amino acids
Increased complexity of organic compounds - How?
- Amino acids are monomers
- Need to linkup to form proteins.
- This requires:
- Input of energy
- Removal of water
- How could this occur?
o Evaporation?
o Freezing?
o Chemical dehydration?
o Bonding to charged mineral surfaces?
??span style='font:7.0pt "Times New Roman"'> Clays
??span style='font:7.0pt "Times New Roman"'> Pyrite
Biogeochemistry: Early organisms' contributions
- Anoxic conditions.
- Probably chemosynthetic, producing H2S, CH4, CO2
- Fermentative anaerobes - bacteria
- Sulfate-reducing bacteria
- Methanogenic bacteria
- Heterotrophs
- Consumed simple organic compounds.
- Some of the early organisms became photosynthetic
- Autotrophs
- Cyanobacteria (stromatolites)
- Possibly due to a shortage of raw materials for energy.
- Photosynthesis was an adaptive advantage
- Oxygen was a toxic byproduct
- Eukaryotic (modern differentiated) cells
- Likely formed by symbiosis and incorporation
- E.g.,
- Chloroplasts
- Mitochondria
- More mobile and adaptable
- Biosphere a tremendous force in the Earth's C, P, N, Si, O cycles
- Photosynthesis/respiration
- O2 + CH2O <= CO2 + H2O
- Redfield ratios
- C:N:P
- 105:15:1
Has not been a smooth ride...
- Evolution
- New competitors
- New biochemical processes
- New environments
- Anoxic = oxygenated
- Sea life only = sea and land life
- Shifts in location and reactivity of reservoirs
- Mass extinctions
- Major Mass Extinctions
- Late Pre-Cambrian (650 Ma?): extinction of early forms of multicellular life
- Ordovician (450 Ma?): extinction of continental shelf sea-floor (benthic) faunas such as trilobites
- Late Devonian (370 Ma?): extinction of coral reefs and other calcareous fauna
- Mid to Late Permian (250 Ma?): ~96% of marine species, reduction of terrestrial species
- Triassic (~210
Ma?): ~23% of marine and
terrestrial faunas, including shelly marine life, insects, some
vertebrates
- End of Cretaceous (65 Ma): all dinosaurs (other than bird-like), loss of marine reptiles, corals, ammonites, other calcareous fauna
- Chance adaptation or locations
- "Survival of the fittest" vs. luck
- Types of change
- Abrupt
- Stepwise
- Gradual
- Episodic (chance)
- Periodic
- Causes
- Climatic change
- Tectonic change
- Oceanographic change
- Extraterrestrial impact
- Volcanism
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John Francis
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Phone: 562-985-4928
written by R. Behl.
Last changes: 10 Oct. 1997