Origin of Life and Prokaryotes

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Origin of Life and Prokaryotes

• Chapter 18

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Reminder

• Quiz this week in lab fruits and flowers lab
  fungi (last week and week before spring break)
• Test Wednesday, April 11th in classChapters
  18,19, and lab material from 20
• Review Session Tuesday, April 10th 430-6 p.m.
  Lewis Hall 224 (lab)
• Will post study guide and Powerpoints today on
  website

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Todays Class

• Geologic Time Toilet Paper analogy and major
  geologic events
• Origin of Lifewhy is there life on Earth?

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Why does life occur on the Earth, but not
elsewhere (we think)
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The Habitable Zone
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Atmospheres

• Venus
• a runaway greenhouse hell
• 96 CO2
• Earth
• -Like Goldilocks
• j-u-u-u-u-u-st right!
• 21 O2, 78 N2, .0037 CO2 (and rising)
• Mars
• 95 CO2
• 1/100th as thick as Earths atmosphere

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How did life originate? hypotheses

• Special creation
• Not testable
• Panspermia
• Came from elsewhere
• Dust particles
• Comets, etc.
• Chemical-Biological theory
• Most accepted theory

Stromatolites, Shark Bay, Australia
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Chemical-Biological Theory

• Simple organic molecules
• Complex macromolecules
• Cell-like structures e.g. protocells
• Note we can replicate all, except weve never
  made cells (i.e. life) in the lab

Cyanobacterialifes simplest forms date back to
3.8 billion Years ago
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Chemical-Biological theory

• Miller-Urey experiment--1950s
• Mimic atmospheric conditions at the time (3.8
  billion years ago)
• Water vapor mixed with early earth atmosphere
• Electric sparks (simulated lightning)
• Cooled and trapped
• All amino acids made

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Protocells

• Protocells are the same size as cells
• They bud (reproduce)
• Even weakly respond to stimuli
• Even have some metabolism
• But its not life!

Protocells budding Similar to binary fission in
prokaryotes