1. Going even further back!
Origin of Life on Earth remains a puzzle

2. Origins of Life on Earth
Ancient Earth
Atmosphere (Stanley Miller experiment)
Amino acids to Protocells
Prokaryotic cells
Eukaryotic cells (endosymbiont hypothesis)

3. Formation of the Planet Earth
Date: ~ 4.6 bya
2. Theory: Nebula Theory
Nebula = space gas and dust
Nebula from “big bang” formed sun & planets
3. Supporting Evidence:
Hubble Space telescope showed formation of stars from supernova

4. Ancient Earth:

5. Formation of Earth’s rocks
Date: ~ 4.0 bya
2. Theory:
Earth was covered with molten lava which cooled
3. Supporting Evidence:
rock cycle today
dating of rocks

6. Formation of Earth’s atmosphere
Date: bya
2. Theory:
volcanoes produced H2, CO, and N gases
no O2
3. Supporting Evidence:
observing volcanoes today
no rust in rocks so no O2

7. Formation of Earth’s oceans
Date: bya
2. Theory:
Lava cooled, H2O condensed; rain filled valleys
3. Supporting Evidence:
Water cycle today
sedimentary layers in the ocean

8. Formation of Simple Organic Compounds
Date: bya
2. Theory:
(1) CH4, H2, NH3, H2O gases combined to form amino acids and nucleotides
(2) Meteorites brought amino acids & nucleotides from space
3. Supporting Evidence:
Miller-Urey experiment
Found meteorites

9. Earth’s Early Atmosphere & Stanley Miller Experiment

10. Formation of Complex Molecules
Date: bya
2. Theory:
amino acids formed chains of proteins
nucleotides formed nucleic acid (RNA first)
3. Supporting Evidence:
experiments show proteins will clump together
Still no O2 present or RNA/DNA would have been damaged

11. Formation of Proto-Life
Date: bya
2. Theory:
DNA was enclosed in a membrane since the protection would allow chemical reactions to happen faster
3. Supporting Evidence:
“chimneys” formed in ocean acted as membranes
observed DNA become enclosed by lipids (lipid bilayer occurs naturally)
Microspheres exist today that show almost all characteristics of life

12. Biologists on the Verge of Creating New Form of Life
Biologists on the Verge of Creating New Form of Life September 08, 2008
Szostak's protocells are built from fatty molecules that can trap bits of nucleic acids that contain the source code for replication. Combined with a process that harnesses external energy from the sun or chemical reactions, they could form a self-replicating, evolving system that satisfies the conditions of life, but isn't anything like life on earth now, but might represent life as it began or could exist elsewhere in the universe.

13. First True Cells Date: 3.5 bya 2. Theory:
First cells were anaerobic prokaryotes;
Heterotrophic
3. Supporting Evidence:
microfossils

14. Prokaryotic cells (No membrane enclosed structures)

15. Ancient Photosynthesis
Date: bya
2. Theory:
Bacteria did ancient form of photosynthesis (chemosynthesis) to produce food from H2S
Release H2SO4 instead of O2
3. Supporting Evidence:
change in fossils (type and numbers)
Reaction still seen around volcanic vents

16. Modern Photosynthesis
Date: bya
2. Theory:
Some chemosynthetic bacteria evolved to become photosynthetic
ozone created
3. Supporting Evidence:
fossils
Stromatolites seen today composed of cyanobacteria
Observation of ozone layer today

17. Evolution of Eukaryotic cells
Date: bya
2. Theory: Endosymbiosis
Relationship in which one organism lives within the body of another to the benefit of both.
Mitochondria and chloroplasts may have developed through endosymbiosis.
3. Supporting Evidence:
Mitochon. & chloroplast have own DNA & ribosomes
DNA in a circle like prokaryotes
Similar gene structures

18. Endosymbiosis