Surface Ocean Processes

1
Surface Ocean Processes

• The Genesis of Life?

2
Step 1 Creating Amino Acids

• The first step in the emergence of life would
  require simple organic compounds that are the
  building blocks of life. The 1953 Miller-Urey
  experiment in showed some of these building
  blocks could be easily formed in a mixture of
  water, methane and ammonia when this mixture was
  exposed to an energy source

NH3 2CH4 2H2O energy ? C2H5O2N 5H2
3
Glycine looses mixed in the ocean
Right Hand Side H is looking to attach to
something else as is the reactive H atom
4
Dilute Monomers

• If the mixture of these monomers (single carbon
  atoms) is too dilute in the oceans the entire
  process will fail.
• This next step must be taken

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Polymer Formation

• First step towards cells
• Note that Glycine is also found in the tails of
  Comets ? did comet delivery seed the earth with
  building blocks of life?
• Mechanisms that concentrate the monomers would
  aid in polymer formation

6
Clay Theory

• The only practical mechanism for concentration is
  evaporation that is driven by some agent. for
  evaporation. In this case, there are two clear
  possibilities
• heat the surface water 
• evaporate the surface water from small
  concentrations of ocean water.  
• Inland tidal pool could evaporate under the
  intense sun in a couple of weeks or so. The tidal
  mud would be come highly concentrated in monomers
  that were originally in the ocean. The silicate
  surfaces that compose this mud are known to be
  good catalysts for polymer formation.
• Four billion years ago the moon was substantially
  closer to the Earth than it is now. That means
  that tides of a few thousand feet high were not
  that unusual! Those large tides could have easily
  formed relatively large inland, shallow lakes,
  which are prone to rapid evaporation so that the
  monomers would settle into the clays that formed
  the lake bottom.

7
Deep Sea Thermal Concentration

• Experiments starting in 1997 showed that amino
  acids and peptides could form in the presence of
  carbon monoxide and hydrogen sulfide with iron
  sulfide and nickel sulfide as catalysts under
  conditions of high temperature and pressure, such
  as those found in a deep sea thermal vent.
• The successful experiments required temperatures
  of about 100 C and moderate pressures, although
  one stage required 250 C and a pressure
  equivalent to that found under 7 kilometers of
  rock. These conditions do occur and therefore
  hydrothermal facilitation of protein synthesis
  (e.g. polymer formation) could well have occurred
  in that environment.
• In fact, this environment is more natural place
  for this chemistry to occur and perhaps Step 2 is
  entirely driven by this deep sea process and
  nothing relevant is happening on the surface.
  Over time this formed polymers could drift up to
  the surface. Immersion in a liquid medium is very
  important for further processes to occur since
  the liquid medium both protects these large
  molecules from disruption by ultraviolet light
  (remember, there is no ozone layer yet) and it
  serves as a transport and interaction medium.

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Step 3 Discovering a Genetic Code

• Big Question

We dont know but there are plenty of ideas
9
DNA Formation

• In our framework, it is now useful to think of
  the next set of steps in terms of the idea of
  evolutionary advantage. For instance, its clear
  that those polymers that can reproduce themselves
  have a strong evolutionary advantage over those
  that can't because those that can't die and those
  that can live.
• Organic polymers in high concentration can
  separate out from the liquid medium as individual
  droplets. These may be the first proto-cells
• Long chain moleules (e.g. peptides) can
  potentially act as a primitive membrane for that
  proto-cell to control the flow of
  nutrients/proteins to the proto-cell.
• This exchange process continues, by Trial and
  Error until the "right" combination is achieved
  (e.g. DNA).

10
Time

• The fossil record shows that the first primitive
  cells/bacteria capable of reproduction, known as
  blue-green algae appear at least 2.8 BYA with
  some good evidence for formations as old as 3.5
  BY. In this sense we know that it took at least
  one billion years to evolve from atmospheric
  chemistry to blue green algae via the oceanic
  pathway. Perhaps then, all you need is time and a
  reasonable stable environment (like the oceans)
  to exist for a billion years or so.

11
Multiplying Populations and the Need for
Resources

• Eat each other? Fermentation process is
  inefficient
• Process another element H2S from volcanoes,
  metabolize the sulfur ? anaerobic photosynthesis
  which produces glucose
• Problem not enough H2S to sustain growing
  population

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Aerobic Photosynthesis

• Substitute H20 for H2S ? requires 1/3 more energy
  so use UV photons at ocean surface as the energy
  input. Bacteria have to evolve this capability
• There is no shortage of H20 so bacteria that
  develop this capability evolutionary advantage.
• The fossil record indicates that it takes about
  500 million years from the appearance of the
  first blue-green algae engaging in anaerobic
  photosynthesis (cyno) bacteria that are able to
  use water producing oxygen as a waste product..