History of Life on Earth

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History of Life on Earth

• Theories and Ideas on How Life Began and What Has
  Happened Since

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From Nothing to Everything?
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The Big Bang Earths Prehistory
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The Big Bang Earths Prehistory

• The Big Bang Theory is the dominant scientific
  theory about the origin of the universe.
• Created the universe between 10 billion and 20
  billion years ago
• Cosmic explosion hurled matter in all directions

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The Prebiotic Earth First Billion Years
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The Prebiotic Earth First Billion Years

• In order for life to exist on Earth, four
  requirements must have existed
• Presence of chemical building blocks
• Source of energy
• Little or no free oxygen
• Time
• Major elements found in living things
• C, H, O, N, P, S

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Oparins Hypothesis
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Oparins Hypothesis

• 1930s - Alexander Oparin hypothesized that life
  began between 3.9 to 3.5 billion years ago.
• Simple organic molecules containing carbon formed
• Energy from the sun, lightning, and earth's heat
  triggered chemical reactions
• Organized by chance into complex organic
  molecules
• 1952 - Miller-Urey Experiment
• Simulated conditions on Earth 4 billion years
  ago
• Experiment made some of the fundamental building
  blocks of life
• This suggests that these can form naturally
• Still flaws with the experiment though

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Iron-World Hypothesis
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Iron-World Hypothesis

• Suggests that life began in deep-cracks in the
  Earths deep ocean floor
• Lab experiments show production of simple organic
  compounds

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Evolution of Oxygen Content of Earths Atmosphere
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The Origin of Life on Earth
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The Origin of Life on Earth

• Life began in the sea as single-celled organisms
• Life develops into more complex forms through
  gradual evolution
• Early organisms had no hard parts to leave fossil

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Geological Time Scale
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Catastrophes? Thats Normal!
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Catastrophes? Thats Normal!

• Life on Earth has been punctuated by catastrophes
• Catastrophes cause ecosystems to collapse and
  species become extinct
• Adaptive radiation occurs following mass
  extinction

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Endosymbiosis Theory
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Endosymbiosis Theory

• Theory suggests that prokaryotes (simple cells)
  gave rise to the first eukaryotes (more complex
  cells)
• Bigger prokaryotic cell engulfed smaller
  heterotrophic prokaryotic cell
• Prokaryotic cell became dependent on host cell,
  which received more ATP production