How did chemisty and oceans produce this?

Remember, the chemistry/biology of 4 billion years ago was totally different than it is today. Today, everything is facilitated by Cells :

Properties of Cells Today:

Prokaryotes

• no nucleus
• no organelles
• no compartments
• circular DNA
• size
• contrast with eukaryotes

Eukaryotes-

• nucleus
• organelles

Prokaryotes precede Eukaryotes by approximately 2 billion years.

Making Polymers Today:

• concentration of monomers and enzymes and proteins which act as an energy source
• O and OH are removed (hydration)
• monomers join together to make polymers

4 Billion years ago there were no cells to facilitate this. The available energy sources were

• lightning (Jupiter -- Galileo Results )
• heat
• UV
• solar radiation

All of the above are quite inefficient compared to enzymes

Now we have a multiplying population of bacteria (prokaryotes) that has to eat to survive:

What to eat?

• First feed off other organic molecules via fermentation
• fermentation is very inefficient, releases little energy
• Big problem --> the food supply is running out

EVOLUTIONARY ADVANTAGE: Bacteria that could process plentiful UV light and INorganic molecules will survive

• are most plentiful molecules dissolved in the oceans
• requires least amount of energy to break apart
• early blue green algae therefore metabolized giving off sulfur as a waste product --> stinky anerobic photosynthesis
• Important --> photosynthesis evolved from a need for the bacteria to be able to feed themselves and multiply

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There is still a problem:

• Not much is available for anerobic processes to use.
• But hey, there is all this that we are floating in so let's do this

  

So, chlorophyll evolves to more complex forms so that it can capture and store enough UV energy to breaking the hydrogen-oxygen bond in water.

Now we have a mechanism to deliver Oxygen to the atmosphere via the aerobic photosynthesis of blue-green algae. But, the oxygen does not initially go into the earth's atmosphere. Instead we have to wait 1.5 -2 billion years to get oxygen into our atmosphere!

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How did this thing get here?

So now we can crawl out on the Land!

Life:

• Astronomical Definition: self-replicating information
• Biological Definition: replication via nucleic acids (DNA

Dispersal of Parental Units by a variety of mechanisms:

Passive: (slowly alters gene pool over time)

• Migratory Random Walks
• Continental Drift
• Mountain Building
• Climate Changes
• Milloins of years timescale

Active: (catastrophe --> "overnight" change in ecosystem)

• Asteroid Impacts
• Large Floods
• Volcano eruption
• massive earthquake

Survival of the fittest works in well-defined, slowly evolving ecosystems (like the ocean); On long time scales, the role of random catastrophe is more important

Mass Extinctions in Geological History:

• 500 million years ago (unclear)
• 230 million years ago --> definite
• 65 million years ago --> famous

Mass extinctions mean:

• 1/2 to 2/3 of all species (plant and animal) eliminated
• plankton in the ocean is extincted
• both land and water are affected

Timescale of extinction is crucial in identifying its cause:

• slow --> environmental degradation
• rapid --> nuked

Evidence from Fossil Record: 100-150 million year extinction periodicity ???

• Plate Tectonic Cycle ?
• Climate Cycle ?
• Solar Cycle ?
• Solar System Cycle ?
• Galactic Cycle ?

Since the orbital period of the Sun around the center of the Galaxy is about 250 million years then every 100-150 million years the earth is in a spiral arm which is a region of high supernova density. It is possible the earth could be subject to high radition from these supernova.

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