1. The Evolutionist Theory of the Origin of Life
Packet #31

2. Geologists & The Early Earth
Biologists generally agree that life originated from non-living matter.
Chemical Evolution
Is very difficult to test experimentally
Four Requirements
Little or no free oxygen
A source of energy
The availability of chemical building blocks
Water
Minerals
Gases present in the atmosphere (All necessary to form organic molecules)
Time
Necessary for molecules to accumulate and react.

3. Chemical Evolution
During chemical evolution, small organic molecules formed spontaneously and accumulated
There are two hypotheses proposed
Prebiotic Soup Hypothesis
Organic molecules formed near Earth’s surface in a “sea of organic soup” or on rock or clay surfaces.
Iron-sulfur World Hypothesis
Suggests that organic molecules were produced at hydrothermal vents
Cracks in the deep ocean floor

4. Major Steps in the Origin of Cells
After small organic molecules were formed
Macromolecules were assembled from the small organic molecules.
Protobionts were formed from the macromolecules
Macromolecular assemblages
Cells then arose from the macromolecular assemblages
RNA World Model
RNA was the first informational molecule to evolve in the progression towards a self-sustaining and self-supporting cell
Natural selection at the molecular level resulted in the information sequence
DNA-->RNA-->protein

5. How the Evolution of Photosynthetic Autotrophs affected Both the Atmosphere and Other Organisms
The first cells, prokaryotic heterotrophs, obtained organic molecules from the environment.
Anaerobes
Later, autotrophs arose
Organisms that produce their own organic molecules by photosynthesis.
The evolution of photosynthesis ultimately changed early life because it generated oxygen
This oxygen produced accumulated in the atmosphere
Allowed the evolution of aerobes
Organisms that use oxygen for a more efficient cellular respiration.

6. Endosymbiont Theory Eukaryotic cells arose from prokaryotic cells.
Certain organelles found within eukaryotic cells evolved from prokaryotic endosymbionts with larger prokaryotic hosts.

7. The Geologic Record
Know Table 26.1 on page 519
Chapter 26