Surface Ocean Processes The Genesis of Life?

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 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

Glycine looses mixed in the ocean Right Hand Side H is looking to attach to something else as is the “reactive” H atom

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:

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

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.

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.

Step 3: Discovering a Genetic Code Big Question Big Question We don’t know but there are plenty of ideas …

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).

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. 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.

Multiplying Populations and the Need for Resources Eat each other? Fermentation process is inefficient Process another element H 2 S – from volcanoes, metabolize the sulfur  anaerobic photosynthesis which produces glucose Problem – not enough H 2 S to sustain growing population

Aerobic Photosynthesis Substitute H 2 0 for H 2 S  requires 1/3 more energy so use UV photons at ocean surface as the energy input. Bacteria have to evolve this capability Substitute H 2 0 for H 2 S  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 H 2 0 so bacteria that develop this capability evolutionary advantage. There is no shortage of H 2 0 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.. 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..