Origin of Life

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Origin of Life

• Origin of Universe
• Origin of Elements
• Origin of Sun Solar System
• Origin of Living Systems
• Evolution of Living Systems

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Arguments for Origin

• Divine
• Extraterrestrial
• Chemical evolution

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In the beginninga big bang

• About 15 billion years ago
• Evidence
• Hubble Expansion
• Big Bang Nucleosynthesis
• Microwave background radiation

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Big bang Hubble Expansion

• Galaxies appear to be moving away from our galaxy
• Initially observed by Edward Hubble in 1927
• Galaxies have a red shift in light produced by
  the Doppler effect similar to sound (also used in
  radar)
• The movement of galaxies away from us corresponds
  to an equation called "Hubble's Law"
• The time elements in Hubble's Law permit the
  estimation of the age of the universe about
  13.7 billion years

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Big Bang - Nucleosynthesis

• Occurred during seconds 100 to 300 following big
  bang temperature cools allowing hydrogen to form
• Result of temperature of universe dropping below
  that required for nuclear fusion (4 H to He)
  forms Helium
• Produced a large amount of Helium which is very
  stable and cannot be converted easily into
  heavier elements
• Amount of background Helium measured in universe
  is consistent with Big Bang Nucleosynthesis

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Big Bang Background Radiation

• If big bang then there should exist remanentt
  heat
• The cosmic microwave background was predicted in
  1948
• 1964-65Arno Penzias and Robert Woodrow Wilson
  measured the temperature to be approximately
  2.725 K which translates to specific background
  radiation in the microwave range.
• This radiation as a signature of the big bang.
• Penzias and Wilson received the 1978 Nobel Prize
  in Physics for their discovery.
• Observation confirmed by later NASA observations.

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Origin of Elements

• Hydrogen fuses to form helium
• Hydrogen Helium most abundant
• Suns energy drives life processes
• Stars become red giants as hydrogen runs low
  (about 10 billion years)
• Helium fuses into other elements
• Star goes nova (blows up)
• Heavier elements released into space

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Sun and Planets

• Sun formed about 5 billion years ago
• Gravitational attraction of gases
• Gravitational field becomes great enough to
  initiate fusion reactions
• Accretion forms inner planets moons from dust
  and debris of supernova
• Process occurs quickly-earth moon about same age

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Early Earth

• Earth 4.6 billion years old (U238 dating)
• Moon rocks meteorites
• Early Atmosphere mostly non-oxidizing
• Nitrogen
• Carbon dioxide
• Water (as water vapor)
• Lesser amounts
• CO, H2, NH3, H2S and CH4

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Venus, Earth Mars Comparison
Venus Earth Mars
Atmosphere CO2 (gt98) N2 (1) Ar (1) O2 (0) CO2 (0.03) N2 (79) Ar (1) O2 (20) CO2 (96) N2 (2.5) Ar (1.5) O2 (2.5)
Pressure 91 atm 1 atm 0.006 atm
Temperature 740 K 290 K 240 K
Gravity 8.87 m/s2 9.87 m/s2 3.72 m/s2
870º F 70º F -30º F
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Characteristics of Life

• Composed of Cells
• Reproduce in kind
• Metabolism / Energy Transformations
• Respond to stimuli

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Abiogenesis

• The process of life from the inanimate
• Formation of organic monomers from inorganic
  molecules
• Formation of organic polymers from organic
  monomers
• Evolution of membranes
• Evolution of DNA based reproduction

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Chemical Evolution

• Requires a non-oxidizing atmosphere
• No oxygen initially
• Requires a sources of energy
• Lightening, UV light, Volcanoes Meteorites
• Requires hydrogen, nitrogen, carbon, oxygen
• Components of organic and biological compounds
• water, ammonia, carbon dioxide/methane
• Requires time

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Chemical Reactions Chemical Reactions

• Need to speed up chemical processes
• Reactions are sped up by
• Increasing concentrations of reactants
• Temperature
• Common phases
• Solvent effects
• Catalyst

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Molecular Clues to Origins

• The following suggest common origin
• Organisms use molecules based mostly on hydrogen,
  nitrogen and carbon present on early earth
• Only L-amino acids found in proteins
• DNA RNA are universal in all organisms
• ATP is energy intermediate in all organisms
• All organisms initiate carbohydrate metabolism
  with similar steps
• Genetic code is universal
• All cells bound by a plasma membrane composed of
  a lipid bylayer

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Organic Monomers

• Oparin Haldane suggest organic molecules could
  form from precursors (1930)
• Miller Urey test using an apparatus which
  simulates early earth (1950)

Stanley Miller
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Organic Polymers

• Major Groups - Nucleic acid, proteins, lipids,
  polysaccharides - have been formed synthetically
• Information vs. Structural vs. Catalytic
• Protenoids will form spontaneously on clay
• D L amino acids can be selected on calcite - a
  common crystalline mineral
• RNA - has all three capabilities

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RNA Life

• Ribose, a component of RNA will form
  spontaneously from formaldehyde and HCN
• Some RNAs have been found to have catalytic
  activity - ribozymes
• RNA has structural capability in ribosomes
• RNAs have an information carrying capacity in
  viruses RNAs have been induced to take on new
  traits

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RNA Life

• Book segment by B. Alberts http//www.ncbi.nlm.n
  ih.gov/books/NBK26876/
• http//exploringorigins.org/timeline.html
• https//www.princeton.edu/achaney/tmve/wiki100k/d
  ocs/RNA_world_hypothesis.html

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DNA Life

• Separation of functional roles of molecules
  related to constant input of energy
• Separation of information carrying capacity from
  other roles of molecules in cells
• RNA to DNA
• RNA to Protein - catalytic capacity
• Protein polysacharides take on structural roles
  in cells

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Membranes

• Why cells?
• Inside vs. outside
• Concentration effect on reactions
• Indications of process
• Microspheres - hydrocarbons in water form
  microsperes which can contain other molecules
• Liposomes - artificial lipid bilayers very
  similar to cell membranes but smaller - used for
  drug transport

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Prokaryotic Cells

• Appear about 3.5 billion years ago
• Photosynthesis in blue-green algae begins to
  modify atmosphere
• Oxygen in atmosphere begins to modify types of
  organisms

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Stromatolites
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Mono Lake, California
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Eukaryotic Cells

• Begin to appear in fossil record about 2.5
  billion years ago
• Considerable internal structure relative to
  prokaryotic cells
• Precursors to multicellular organisms

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Fossil Record

• Dating
• Stratographic analysis
• Radiometric dating
• Geologic Time
• Precambrian - 4.6 to 0.57 billion years ago
• Fossils all unicellular
• Caambrian 0.57 billion years ago to present
• Multicellular organisms
• Extinction Level Events

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Evidence for Evolution

• Physical methods radiometric dating
• Fossil record
• Anatomical comparisons
• DNA sequence analysis
• Laboratory experiments showing selection