The great oxidation event geological time periods

• what was the Great oxidation event

  Event where oxygen levels in the atmosphere increased dramatically
• describe the Hadean Eon

  • Period before life appeared on Earth (Pre-life)
  • 4.6 - 8.8 Ga ago (billion years ago)
  • Earth formed with a molten core and lighter crust
  • atmosphere: methane, water, ammonia, nitrogen and carbon dioxide
• describe the Archean Eon

  • Period when life first appeared on Earth
  • 3.8 to 2.5 Ga ago
  • atmosphere: methane, carbon dioxide, nitrogen and oxygen
• • Oxygen derived from photosynthesis of CO2 by cyanobacteria (blue-green algae)
  • Cyanobacteria contained thylakoid membranes allowing photosynthesis to take place
• Change in the Archean Eon atmosphere

  • oxygen oxidised soluble iron in the seas forming banded iron formations
  • this oxidised and reduced methane and ammonia from the atmosphere
  • as oxygen rose and organisms increased, oxygen in the atmosphere increased and dissolved into the water - the oxygen catastrophe
• the oxygen catastrophe:

  • Oxygen is poisonous to anaerobes, reducing their levels of methane by oxidation
  • lead to a mass extinction
• How did the snowball Earth occur?

  • loss of greenhouse gasses lead to a fall in temperature and freezing of Earth's surface and seas
• • Before Great Oxidation: sky orange, ocean green.
  • After: sky blue, ocean blue
• • Rise in oxygen led to rise in ozone in the stratosphere, providing protection from UV rays
  • O + O2 -> O3
• The boring billion

  • Period of 1 billion years between oxygen appearing and life booming
  • climate and oceans remained relatively stable
  • oxygen levels fluctuated
  • complexity of life increase
• Endosymbiosis

  • symbiosis - the living together of two different organisms in close association
  • endosymbiosis - A symbiotic relationship where one organism lives inside the other
• Primary endosymbiosis led to the formation of mitochondria and chloroplasts in eukaryotic cells
• Aerobic respiration

  • Advantages: produces energy as ATP.
  • Disadvantages: produces free radicals, slow and requires ATP
• Cambrian explosion

  • life moved from aquatic to terrestrial 500-400 Ma
  • oxygen in water is 3% of that in air
  • plants, insects and invertebrates (dragonflies and millipedes) were the first to evolve on land
  • plants contributed to the rise of oxygen
• Early land plants

  • Moss
  • vascular plants
  • Ferns
  • Gymnosperms
  • Angiosperms
• Homeobox/Hox genes allowed the Cambrian explosion and evolutionary competition of animals
• Early land animals

  • Faced challenges with water conservation, gas exchange, reproduction and dispersal
  • animals evolved: waterproof external layers, and internal gas exchange systems, reproduction without water and support systems allowing movement on land