1. Earth History GEOL 2110
Early Life
Chapter 9

2. Major Concepts
The oldest fossils known are filaments of cyanobacteria (blue-green algae) that are 3.5 billions years old
Experiments simulating the origins of life are able to create the building blocks of life (proteins and amino acids) from the primordial soup of the early earth oceans and oxygen-depleted atmosphere.
Simple, asexually reproducing, single-celled organisms persisted until 700 million years ago.
The first multicellular organism appeared as soft-bodied creatures around 700 million years ago during a period of extensive global glaciation, supercontinent breakup, and carbon infusion into the oceans
The appearance of organisms with skeletons appeared in the Cambrian after a significant increase in oxygen

3. Conditions on Earth 3.5-4.0 Ga
Oxygen deficient (anaerobic) atmosphere
Late Heavy Bombardment ( Ga)
Oceans present since 4.2 Ga (very warm)
Darwin’s “Warm Little Pond” - Primordial Soup (CH4, NH3, CO2, N2 rich) – all the components necessary to make life
Intense UV bombardment (no ozone)

4. Origin of Life: Early Ideas
Spontaneous Generation – process of putrefaction somehow producing metamorphosis of nonliving to living matter
Louis Pasteur's sealed flask experiments
If life doesn't spontaneously generate now, how could it in the past?

5. Recreating the “Warm Little Pond”
Miller demonstrated that a wide range of vital organic compounds (amino acids, cyanide, formaldehyde) can be synthesized by fairly simple chemical processes from inorganic substances
Stanley Miller

6. Making Polymers
Polymer – complex chains of linked simple organic molecules (proteins, nucleic acids, sugars, fats, enzymes)
Experimentally derived in a number of ways
– splashing amino acids under hot, dry conditions forming proteins (Sidney Fox)
– Cyanide, clays, and heat capable of polymerizing amino acids into proteins
- Can form nucleotides under similar conditions (heating of ammonium and cyanide – Miller)
Sidney Fox
Protenoids behave much like bacteria, regulate their cells, excrete waste, metabolize sugars

7. Cell membranes
Formed from fatty acids - carboxyl group (COOH) and aliphatic chain
Fatty acid (hydrophobic) + alcohol (hydrophyllic) form lipids
Lipids form cell membranes that regulate what goes in an out of a cell
Actually easy to synthesize as well as found on meteorites

8. Reproduction Coding and Replication
Which came first?
Protein synthesis or nucleic acid (RNA)
Current thinking is RNA evolved first as “naked genes” and become encoded with the help of ribozymes
Other Templates suggested for serving as templates for reproduction are: Clays, Zeolites, and Pyrite (FeS2)

9. 3.4 Ga stromatolite Swaziland Supergroup, South Africa
Single-celled Prokaryotes Rule
3,500 – 700 Ma
3.5 Ga
Cyanobacteria
Australia
1.15 Ga
4-celled cyanobacteria in chert
3.4 Ga stromatolite Swaziland Supergroup, South Africa
Modern filamentous cyanobacteria, Lyngbya

10. Evolution of Prokaryotes and Eukaryotes
Reducing, sulfur-rich
Hydrothermal vents
Photosynthesizing bacteria

11. Prokaryotes and Eukaryotes
Fig. 9.7
Prokaryotes and Eukaryotes

12. Evolution of Eukaryotes
More complex eukaryotes are thought to have developed from symbiotic relationships between prokaryotes Symbiotic origin of Eukaryotes around 1.75 Ga, didn't diversify much until 1.1 Ga (sexual reproduction?)

13. Multicellullar Organism (Metazoans) Appear ~ 600Ma

14. Ediacaran Metazoan Trace Fossils
Metazoan fossils from Ediacara Hills, Australia, 600 to 550 million years ago.
Soft bodied - like jelly fish or sea pens

15. Cambrian Explosion (535--510 ma)
Soft bodied organisms replaced with many fossils of shelled invertebrates
Significant amounts of burrowing/trace fossils
Large diversification of fossil record
Likely related to the end of the extreme Varangian glaciation and increased tectonic rifting of Rodinia

17. Additional contributors to the Cambrian Explosion
Potentially higher atmospheric O2 (close to modern concentrations) promotes calcite exoskeleton secretion (phosphate and silica common under low O2 conditions).
Increased nutrients associated with more rifting and volcanic activity
Abundant cyanobacterial mats for molluscs and other small invertebrates to graze
Development of predators
Tiering of biotic activity on the sea floors

18. Burgess Shale
Middle Cambrian from Field, British Columbia (discovered in 1909)
Abundant well preserved fossils of soft bodied animals
Highly experimental forms

19. Summary of Early Earth Events

20. Vendian, Cambrian and Early Ordovician Periods Part I Chapter 10
Next Lecture
Vendian, Cambrian and Early Ordovician Periods Part I Chapter 10