The Origin and Early Evolution of Life Chapter 18.
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Transcript of The Origin and Early Evolution of Life Chapter 18.
The Origin and Early
Evolution of Life
Chapter 18
Learning Objectives
1. Differentiate between chemical evolution and organic evolution.
2. Describe the conditions on the primitive earth predicted by laboratory experiments that favored the spontaneous development of organic molecules.
3. Explain the probable sequence in the origin of the first cells, and describe how this cell interacted with its environment.
4. Review the theories proposed to explain the origin of eukaryotic organelles.
The Big Bang
• 12-15 billion years ago all
matter in the universe was
compressed into a mass
the size of our sun
• Sudden instantaneous explosion of matter and energy throughout the known universe
Earth Forms• About 4.6 to 4.5 billion years ago• Minerals and ice orbiting the sun
started clumping together• Heavy minerals moved to Earth’s
interior, lighter minerals floated to surface– Produced outer crust and
inner mantle• Chemical evolution produced the
primordial sea and the early atmosphere that would support the biosphere of the future.
p. 288
Earth Is “Just Right” for Life
The Planet:
• If smaller in diameter, gravity would not be great enough to hold onto atmosphere
• If closer to sun, water would have evaporated
• If farther from sun, water (the solvent of life) would have been locked up as ice
Early Atmosphere:
• Hydrogen gas
• Nitrogen
• Carbon monoxide
• Carbon dioxide
• No gaseous oxygen
p. 288
Stanley Miller’s Experiment
• Mixed methane, hydrogen, ammonia, and water
• Simulated lightning• Amino acids and
other small molecules formed
What, at a minimum, is needed to form a cell-like structure from these molecules?
p. 289
Possible Sequence
START: “Chemical Evolution”
“Organic Evolution”
informational molecules
separation of environments
ENDp. 291
Why is RNA believed to be the first genetic information?
Why is DNA a better molecule for heredity?
The First Cells
• Prokaryotic heterotrophs
Describe what this means.
• Secured energy through
anaerobic metabolism
…Describe.
– No oxygen present
…Why not?
p. 291Is there fossil evidence for these first cells?
Fossil Evidence• photosynthetic eubacteria
• Oxygen producing
• permits aerobic respiration
3.5 bya
2.1 bya 1.2 byap. 292
Possible Origin of ER & Nuclear Envelope
DNA
infolding of plasma membrane
p. 294
aka: Autogenous Theory
Endosymbiotic Theory
Cyanophora paradoxa
p. 295