Origins of Life

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Origins of Life

• Early Idea Spontaneous Generation
• The idea that non-living material can produce
  lifeLife magically appears!
• Examples
• Meat produces maggots
• Mud produces fish (mudskippers)
• Grain produces mice

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Origins of Life

• Francesco Redi was first to disprove the theory
  of spontaneous generation in 1668
• Experiments with rotting meat

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Origins of Life

• Also during this time, scientists were just
  beginning to use microscopes
• They were able to see that microorganisms were
  EVERYWHERE!
• Even though Redi was able to disprove the theory
  of spontaneous generation, many scientists
  thought that microorganisms arose spontaneously
  from a vital force in the air

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Origins of Life

• Louis Pasteur
• Disproved the spontaneous generation of
  microorganisms
• Experiments with broth

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Origins of Life

• Pasteurs experiments showed that microorganisms
  do not arise from the broth alone even in the
  presence of air
• Biogenesis became the accepted theory about the
  origin of life
• Biogenesis is the idea that living organisms only
  come from other living organisms

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How Did Life Begin On Earth?

• Early Earth
• Very Hot
• Meteorite Collisions
• Volcanoes
• Very little oxygen
• Atmosphere made of H2O Vapor, CO2, N gas, CH4
  NH3

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How Did Life Begin On Earth?

• Ingredients for Life Before life can occur, you
  need the molecules of life
• 1st Formation of simple organic molecules
• 2nd Organization into complex organic molecules
• Proteins / Carbohydrates / Nucleic Acids / Lipids
• So How did this happen in such a harsh
  environment?

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How Did Life Begin On Earth?

• Miller Urey (1953)
• Tested theory by simulating conditions on early
  Earth in a lab
• Mixture of H20 vapor, NH3, CH4, and H gasses was
  zapped with electrodes
• Cooled gasses condensed in flask
• After a week, several kinds of amino acids,
  sugars, and other small organic molecules were
  present in the flask

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How Did Life Begin On Earth?

• The next steps in the origin of life were the
  formation of complex organic molecules and cells
• Heat caused the amino acids to form proteins and
  also caused the production of ATP and nucleic
  acids
• Doing this formed protocells or large ordered
  structures, enclosed by a membrane that carries
  out life functions

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The First True Cells

• First forms of life were prokaryotes that likely
  evolved from protocells
• Anaerobic Heterotrophs
• Later, early prokaryotes evolved to be able to
  make their own food
• These were similar to archaebacteria and used
  chemosynthesis to produce their food

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The First Photosynthetic Prokaryotes

• Likely the next kind of organisms to have evolved
• Were able to use sun to make glucose
• Produced OXYGEN, which changed Earths atmosphere
• Lightening Oxygen Ozone Layer formation

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The Endosymbiont Theory

• Lynn Margulis, in 1960s
• Eukaryotes evolved from prokaryotes as a result
  of symbiotic relationship between prokaryotic
  bacteria