1. The History of Life
Earth’s Early History

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3. Formation of Earth
Key Concept Earth’s Early Atmosphere Contained: Hydrogen Cyanide Carbon Dioxide Carbon Monoxide Nitrogen Hydrogen Sulfide Water

4. Formation of Earth
The Material Forming Earth Probably Condensed From Stellar Debris Over 100 Million Years Surface Originally Molten Atmosphere Pinkish-Orange &

5. Condensation of Debris

6. Earth’s Early Atmosphere

7. Kept Earth Hot Formation of Earth
~4 Billion Years Ago Earth Cooled Enough For A Crust To Form
Volcanic Activity Constant
Comet & Asteroid Hits Constant
Kept Earth Hot

8. Early Crust Forms

9. Formation of Earth ~3.8 Billion Years Ago Oceans Formed
Earth Cooled Enough
For Water To Condense
Oceans Formed
Green/Brown With Iron
Thunderstorms Continuous Life Appeared

10. The First Organic Molecules
Atoms Do Not Assemble Into Complex Organic Molecules Today Due To:
Oxygen is VERY Reactive &
Bacteria would eat them

11. Miller & Urey Stanley Miller & Harold Urey 1950’s - Chemists
Simulated Earths Early Atmosphere In The Laboratory
Ran Electric Sparks Through It Simulating Lightning

12. Miller & Urey
Experiment Generated Amino Acids In Just A Few Days

13. Miller & Urey
Key Concept Miller & Urey’s Experiments Suggested How Mixtures Of The Organic Compounds Necessary For Life Could Have Arisen From Simpler Compounds Present On A Primitive Earth.

14. Corrected Experiments Have Produced Cytosine & Uracil
Modified Miller & Urey
Original Atmospheric Components Not Accurate (Re-Analysis of Chemical Composition of Early Rocks)
Corrected Experiments Have Produced Cytosine & Uracil
Two RNA Bases

15. How Did Life Form From The Organic Soup Of Original Earth?
How Did Life Begin?
How Did Life Form From The Organic Soup Of Original Earth?
Prokaryote Fossils These Fossils Date To Million Years After The Earth Cooled Enough For Water To Form

16. Formation of Microspheres
Proteinoid Microspheres
Large Organic Molecules Naturally Form Tiny Bubbles
Not Cells But Have Some Characteristics Of Living Systems
e.g. Selective Permeable Membranes

17. Evolution of RNA & DNA Still Unknown However:
RNA Sequences Have Been Found That:
Help DNA Replicate
Transcribe DNA
Translate Proteins
Catalyze Chemical Reactions
Duplicate Themselves
Perhaps RNA Came First

18. Microfossils - 3.5 Billion Years Old
Free Oxygen
Microfossils Billion Years Old
Prokaryotes
Anaerobic (No O2 In Atmosphere)
Photosynthetic Bacteria Arose
2.2 Billion Years Ago
O2 Continuously Released Into The Atmosphere

19. First It Bound Iron In The Oceans
Free Oxygen
First It Bound Iron In The Oceans
Iron Oxides Settled To The Bottom Of The Oceans
Formed Great Bands Of Iron That We Mine Today
Oceans Changed Turned Blue

20. Next O2 Accumulated In The Atmosphere
Free Oxygen
Next O2 Accumulated In The Atmosphere
O2 Increased
Methane & Hydrogen Sulfide Decreased
Atmosphere Turned Blue

21. First Aerobic Organisms Arise
Free Oxygen
Is Highly Reactive
Deadly To Anaerobes
First Aerobic Organisms Arise

22. Free Oxygen Key Concept
The Rise Of Oxygen In The Atmosphere Drove Some Life Forms To Extinction, While Other Life Forms Evolved New, More Efficient Metabolic Pathways That Used Oxygen For Respiration

23. Variations in CO2 and O2

24. Variations in CO2 and O2 C = Cambrian O = Ordovician S = Silurian
D = Devonian
C = Carboniferous
P = Permian
Tr= Triassic
J = Jurassic
K = Cretaceous
T = Tertiary
“0” on time scale = Today

25. Origin of Eukaryotic Cells
Began About 2 Billion Years Ago
Some Prokaryotes Started Developing Inner Cell Membranes

26. Origin of Eukaryotic Cells
Endosymbiotic Theory
Some Smaller Prokaryotes Began Living In Larger Prokaryotes. A Symbiotic Relationship Developed
Some Became Mitochondria
Some Became Chloroplasts

27. Origin of Eukaryotic Cells
Key Concept: The Endosymbiotic Theory Proposes That Eukaryotic Cells Arose From Living Communities Of Prokaryotic Organisms First Proposed 100 Years Ago

28. Origin of Eukaryotic Cells
Lynn Margulis – Boston U. 1960’s
Evidence
Mitochondria & Chloroplasts Contain DNA & Ribosomes Similar To Bacterial DNA & Ribosomes
They Reproduce By Binary Fission

29. Sexual Reproduction & Multicellularity
Shortly After Forming Multicellular Organisms Sexual Reproduction Began
Accelerated Development of Genetic Variation
A Few Hundred Million Years Later, Multicellular Organisms Arose And Exploded