1. Chapter 20: The Origin and Evolutionary History of Life Early Life Video

2. 4 requirements for chemical evolution of life 1) little/no free O2 2) source of energy 3) availability of chemical building blocks 4) time

3. 2 models for Origin of Life Prebiotic broth hypothesis – simple organic molecules could form spontaneously from simpler raw materials Iron-sulfur world hypothesis – early polymerizations in cracks of ocean floor

4. Fig. 25-2

5. First polymers  protobionts (assemblages of abiotically produced organic polymers) – Traits of living cells – Divide in half – Maintain different internal environment – Catalytic activity

6.  cells – series of small steps – Molecular reproduction – RNA  protein – RNA  DNA Prokaryotes = 1 st cells – Heterotrophs Fermented (anaerobic) organic molecules  energy – Autotrophs Cyanobacteria – give off O2 – Aerobes More efficient; competitive (more energy from glucose than anaerobes) – Cycling of C and O

7. O  upper atmosphere  O3 (ozone) – Blanket Earth; prevent UV rays – Organisms able to live closer to water surface + land Prokaryotes  eukaryotes

8. Endosymbiont Theory Mitochondria + chloroplasts Symbiosis with larger prokaryote Mutualism – lost ability to survive alone Evidence – Individual DNA, ribosomes, tRNA – Double membrane

9. GEOLOGIC TIME SCALE – PAGE 437

10. Geologic Time Scale