Transcript Origins of Life

Origins of Life
“The Scientific Story”
Origin of the Universe and the Earth
14 billion years ago:
• The “Big Bang” led to the formation of the stars of
the “universe”
• The Milky Way is one of many galaxies that make
up the universe
• The sun is the closest star to us
4.5 to 4.6 billion years ago:
• Planets of our solar system were formed including
our earth
Conditions of the early earth:
• very hot
• barren rock
• volcanoes
• lightning
• ultraviolet radiation
• gases:
• methane (CH4)
• ammonia (NH3)
• water vapor (H2O)
• hydrogen (H2)
• hydrogen sulfide (H2S)
• hydrogen cyanide (HCN)
Then what?
• The earth’s temperature cooled over many years
resulting in condensation and huge rains.
• Oceans formed and covered the earth. These oceans
were thought to be near boiling point.
• Chemical Evolution took place, rearranging the atoms
of the gases of the atmosphere into the building
blocks of organic compounds.
ORGANIC COMPOUND
BUILDING BLOCK
Protein
Amino Acids
(20 of them)
Nucleic Acids
(DNA / RNA)
Nucleotides
(ex: A T C G U)
Carbohydrates
Simple Sugars
(example : Glucose)
Lipids
Fatty Acids & Glycerol
Urey and Miller
• In the 1950’s Harold Urey and Stanley Miller did an
experiment to simulate the conditions of the
primitive earth.
• https://www.youtube.com/watch?v=NNijmxsKGbc
Urey and Miller
• What did they find?
• Amino acids and Nucleotides had formed .
• Conclusion?
• Perhaps the building blocks of organic compounds
could have formed on primitive earth (Chemical
Evolution)
The Jump…
• It is thought that these compounds began to
cluster together held by lipid molecules
accumulating. These clusters were called
Coacervates or Proteinoid Microspheres.
• Scientists believe that these “abiotic” proteinoid
microspheres made the jump to become the first
living cell approximately 3.5 to 3.8 billion years
ago.
• Spontaneous Generation? Say what??
What did this first cell look like?
• The first cell was likely:
1. Aquatic
2. Prokaryotic
3. Anaerobic
4. Heterotrophic - Oparin & Haldane’s Heterotroph Hypothesis
• Aleksandr Oparin & John Haldane hypothesized that since the
primordial oceans were full of organic compounds then the first
life forms must have been consumers of these molecules
(Heterotrophic) hence their Heterotrophic Hypothesis.
Biological Evolution now begins
• The following time line describes some of the big
events:
2 billion years ago
• photosynthetic prokaryotes evolve
• releasing O2 into the atmosphere.
• This brought about two major changes:
• Aerobic environment
• Formation of ozone (O3)
• UV-rays  2O2  O + O + O + O  O3 + O
• Aerobic environment led to aerobic organisms
evolving
• With 18X more energy they could grow faster,
reproduce faster and evolve faster.
What Happened Next?
• 1.5 billions years ago eukaryotes evolved
• Large prokaryotic cell engulfs a smaller prokaryotic
cell.
• Resulted in the first eukaryotic cell (mitochondria and
chloroplasts have their own DNA!!)
Endosymbiotic Theory:
• This theory suggests that eukaryotic cells arose from
the symbiosis among several prokaryotic cells.
• Some prokaryotic cells that had the ability to use
oxygen gas to create energy rich ATP molecules
became the MITOCHONDRIA (wow!)
Endosymbiotic Theory
Then what happened ….
• What likely followed?
1. Aquatic multicellularity
2. Terrestrial Autotrophs
3. Terrestrial Heterotrophs
Supplementary Material
• Video on the Big Bang Theory (43 Minutes)
https://www.youtube.com/watch?v=ofI03X9hAJI
• Video on Endosymbiotic Theory (6 Minutes)
https://www.youtube.com/watch?v=bBjD4A7R2xU