Chap. 14 : Origin of Life

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Chap. 14 Origin of Life

• Biogenesis life coming from life as opposed
  to spontaneous generation (life coming from
  nonliving)
• Disproving Spontaneous Generation
• 1. Francesco Redi flies, maggots,
  meat
• 2. Lazzaro Spallanzi heated meat
  broth no microorganisms killed vital force

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3. Louis Pasteur heated broth, curved neck of
flask - - no growth in broth. Broke off flask,
growth in 1 day. Conclusion did not kill vital
force but rather air contains living things that
we can not see

• II. Earths formation
• - 5 billion yrs. ago solar system
  together in swirling mass of gas and dust.
• - Mass collapses inward forming sun
• - excess released to form planet 4.6 billion
  yrs. ago
• - volcanic eruptions formed atmosphere which
  lead to oceans
• - 2.2 billion yrs. ago Earth formed as we
  know it today

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III. Theories of Support

• Radioactive dating measure the rate of decay
  (breakdown) of radioactive isotopes called
  half-life.
• Compare C12 (stable carbon) to C14
  (radioactive carbon) in fossils. We know it takes
  5,730 yrs. to be reduced by ½. Only accurate up
  to about 60,000 yrs. old.
• ---Can use U238 up to 4.5 billion yrs.
  ago.

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IV. Formation of Life

• Alexander Oparin (1923) said primative Earths
  atmosphere contained NH3, H2, H2O, CH4
• a. Add high heat (volcanic eruptions) to
  these chemicals and reactions occur to form
  simple organic compounds (amino acids)
• b. Earth cools, simple organic compounds
  collect in H2O
• c. Add lightning and UV radiation and these
  simple compounds join to make macromolecules such
  as proteins.

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2. Miller and Urey (1953) set up experiment to
test Oparins hypothesis.
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3. Fox proteins joined together to form
membraneous spheres called microspheres

• - linking together of microspheres creates
  coacervates (proteins sugars ). Coacervates are
  considered non-living because they do not contain
  nucleic acids but have some ingredients of
  nucleic acids.
• V. 1st life forms
• A. Conditions on Earth lacking O2,
  therefore believed Archaebacteria were 1st cells
  (prokaryotes) to appear.

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Once the atmosphere began to thin, more sunlight
penetrated Earth and photosynthetic bacteria
evolved. About 3 billion years ago.

• Released O2 into atmosphere over a billion yrs.
  helped form ozone layer which was necessary for
  life to be protected from UV radiation.
• B. Eukaryote Cell Formation
• -- endosymbiosis evidence suggests around
  2 billion years ago a small aerobic prokaryote
  entered and lived inside a larger anaerobic
  prokaryote. Formed a mutualistic relationship
  together.

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• Over time these smaller aerobic prokaryotes
  evolved into mitochondria and/or chloroplast
  (make energy). Evidence is that both of these
  structures even today contain their own DNA
  inside them (not inside nucleus) and it is
  different from DNA inside the nucleus