8 - Origin of Life

• Prokaryotes


  first organisms; single-celled
• Eukaryotes


  modern microbes; complex cells; 2.7 Ga
• Spontaneous Generation

  Inorganic Model

  Extraterrestrial Origins

  Biochemical Model

  Hydrothermal Model


  Scientific Models
• Spontaneous Generation


  Without descent from similar organisms
• Inorganic Model


  arose gradually on a pre-existing, non-organic replication platform; silicate crystals
• Extraterrestrial Model


  Blocks for life from outer space
• Panspermia


  "universal seeding"; views about extraterrestrial model
• Biochemical Model


  could have risen through a series of organic chemical reactions
• Hydrothermal Model


  states that LUCA (Last Universal Common Ancestor) was a hyperthermophile
• Hyperthermophile


  lived in unusually hot conditions
• RNA or RiboNucleic Acid


  one of the nucleic acids and it has key roles in protein synthesis
• Genetic Code


  Basic instructions that contains all the information to construct a living organism: DNA or DeoxyRiboNucleic Acid
• Francis Crick


  Discovered the double-helix structure
• Francis Crick and James Watson


  suggested that RNA was the first genetic molecule
• Early Precambrian World


  very beginning of the Hadean, temperatures were too high

  during the Hadean, few ocean caporizing impacts on Earth

  The Isua Group
• Anoxic


  The Archean world was --
• Methane (David Catling and colleagues)


  What os the more abundant gas in the Archean atmosphere?
• Methanogenesis


  process of generation of methane by methanogens
• Great Oxygenation Event


  cyanobacteria; anaerobic bacteria were killed leading to the Earth's first mass extinction.
• Ozone layer


  due to oxygen; blocks out solar ultraviolet radiation
• Banded Iron Formation


  Alternating bands of Iron-rich (dark: magnetitic/hematitic) chert and iron-poor chert (red: Chalcedony)
• approximately 2.3 Ga


  Continental red bed sediments
• 0.8-0.6 Ga


  A second rise of oxygen occurred around --
• Beginning and End of the Proterozoic


  Two rises in oxygen levels was at the --
• Biogeochemical Cycles


  oxygen and carbon are exchanged continuously
• Precambrian Prokaryotes


  rocks dated from 3.5 to 3.0 Ga
• Cyanobacteria and other prokaryotes


  moedrn stromatolites are constructed by what?
• Stromatolites


  Blue-green algae (Primitive one-celled organisms); thin alternating light and dark layers that may be flat, hummocky, or dome-shaped.
• 3.2 Ga


  How old is the oldest currently accepted fossils?
• Western Australia by Birger Rasmussen


  Where is the oldest currently accepted fossils found and by who?
• Thermophilic (heat-loving) bacteria


  What kind are some of the earliest life?
• Nucleus


  How are eukaryotes distinguished from prokaryotes? by having this containing their DNA in chromosomes and cell organelles.
• Mitochondria


  cell part for energy transfer
• Flagella


  cell part for movement
• Chloroplasts


  cell part for photosynthesis (in plants)
• Basal Eukaryotes


  oldest eukaryote (controversial)
• Lipid biomarkers


  what indicated that eukaryotes were around at least by 2.7 Ga?
• Grypania


  a coiled, spaghetti-like organism that has been reported from rocks as old as 1.85 Ga

  
  

  oldest known fossils on Earth are 3.5 billion year old stromatolites
• Grypania spiralis


  oldest currently known macroscopic body fossils - with distinctive spirally coiled "algae"
• True multicellular organisms


  only among the eukaryotes; more than one cell, typically a long string of connected cells in early forms