Perspectives on Earth History to Paleozoic

• Change is inevitable!!!
• Environmental changes are consequences of the on-going, unfinished evolution of the Earth as a planet
• There is nothing permanent except change
• Man is a recent agent of change
• Loss of internal heat and its consequence called "death of planet Earth" form part of the destiny of this planet
• Geologic time


  One of the major contributions of geosciences to knowledge
• The Earth is 4.56 billion years old
• Rates of change: slow to fast
• The Earth came from dust-cloud or nebula derived from a supernova
• You were at least once a star!
• 1 billion


  It takes 32 years to spend 1 billion pesos at 1 peso/second
• 4.56 billion years is the age of the Earth
• Man's appearance 2-2.5 Ma = 0.04% of geologic time
• Records of Earth History


  • Fossils
  • Earth materials
  • Rock & mineral deposits
  • Structures and features in them

  
• Fossils


  Actual remains, imprints, and traces of formerly living organisms older than 11K years

  
• Types of fossils


  • Actual remains (body fossils)
  • Casts, molds
  • Trace fossils: manifestation of activity (burrows, coprolites, tracks)
  • Chemical: molecules

  
• Actual preservation


  • Amber
  • Tar pits
  • Ice
• Ichnofossils/Trace fossils


  Traces, tracks of animals
• Living fossils


  Organisms that have remained essentially unchanged from earlier geologic times and whose close relatives are usually extinct
• Living fossils


  • Ginkgo biloba
  • Coelacanth (Latimeria chalumnae)
  • Horseshoe Crab
• The fossil record is incomplete but pattern recognition is still possible

  
• The evolution of the horse shows reconstruction of the fossil species obtained from successive rock strata

  
• 3 Major Domains of Life


  • Eubacteria
  • Archaea
  • Eucarya
• Eubacteria


  Prokaryote: no nuclear membrane, some as ancestors of Archaea, chlorophyll-based photosynthesis but most can function anaerobically, large number of heterotrophs oxidize organic molecules for energy, some use inorganic reactions to produce organic molecules
• Archaea


  Prokaryote: no nuclear membrane, probably have common ancestor with Eucarya, many obtain energy from inorganic reactions to make organic matter, typically in extreme environments (high T, high salinity, anaerobic)
• Eucarya


  Eukaryote: with nuclear membrane, many kinds of membranous organelles in cell, chloroplasts probably derived from cyanobacteria, mitochondria probably derived from aerobic bacteria, development of complex cells through symbiosis with other organisms

  
• Origin of Eukaryotic Cells


  Early heterotrophs and autotrophs were unicellular prokaryotes, endosymbiotic theory: free-living prokaryotic bacteria established a relationship with another primitive "nuclear-membrane-containing" cell type
• The Cryptozoic or Precambrian History (4.6 Ga - 540 Ma) represents ~90% of Earth history and records much more obscure than Phanerozoic
• Eons of the Cryptozoic/Precambrian

  • Hadean Eon (4.56 - 3.8 Ga)
  • Archaean Eon (3.8 - 2.5 Ga)
  • Proterozoic (2.5 Ga - 540 Ma)
• Hadean Eon


  Chaotic times: meteorite bombardment, formation of second atmosphere and oceans, oldest crustal rocks (3.9 - 4.2 Ga), towards end: origin of life? (abiogenesis, panspermia)
• Archaean Eon


  Anaerobic conditions, slightly aerobic by ?3 Ga, earliest life forms: prokaryotes, first ones at mid-ocean ridges?, appearance of first life form: 4.1 to 3.8 Ga, abundant stromatolites
• Researchers have determined that fossilized evidence of bacteria from ancient seafloor hydrothermal vent precipitates found in the Nuvvuagittuq belt in Quebec, Canada is at least 3.77 billion years old (or even as much as 4.28 billion years old)
• Stromatolites


  Layered mats produced by the activity of cyanobacteria, composed of calcium carbonate (CaCO3), fossil examples date back as old as 3.5 billion years

  
• Archaean Life


  Prokaryotes (descendants of the first organisms on Earth?), anaerobic, showed no visible signs of change for 1.5 billion years, appearance of multi-cellular organisms only by 0.7 Ma; before: life as unicellular bacteria
• Proterozoic


  Prokaryotic cyanobacteria add O2, gradually increasing O2, but Fe dissolved in water reacts to form banded iron formations (BIF), single supercontinent by 1.1 Ga: Rodinia
• Proterozoic Life


  • Gunflint fossils (Canada, 1.9 Ga): threads (cyanobacteria?), spherical bodies, star-, umbrella-, parachute- shaped bodies, some resemble manganese bacteria in recent lakes

  
• First Eukaryotic Cells appeared around 1.8 Ga
• First appearance of multicellular eukaryote: carbonaceous sheets and ribbons, more abundant from 1.3 Ga and onwards

  
• Varangian Glaciation


  Occurred at end of Proterozoic, continental glaciers at nearly equatorial latitudes, controversial cause, but Earth became like lifeless frozen world (like Mars?), after retreat, multicellular emerge after 3 billion years of single-celled life
• Vendian Revolution


  Late Proterozoic (650 – 543 mya), free Fe used up, free O2 build up in oceans & atmosphere, prokaryotes die or retire to O2-free environments, eukaryotes appear; possess ways to tolerate and use O2