1. Early Earth and the Origin of Life
AP Biology
Crosby High School

2. History of Life 3.5 – 4 bya 3.5 – 2 bya Earth heavily bombarded
Oldest fossils 3.5 bya
3.5 – 2 bya
Rich fossil record of Prokaryotes
Bacteria and Archae diverged
Stromatolites

3. History (cont.) 2.7 bya 2.1 bya Emergence of Cyanobacteria
O2 appeared in atmosphere
First dissolved in Water
Excess react with Iron
Corrosive to chemical bonds
2.1 bya
Eukaryotes evolved from symbiosis
Chloroplasts could account for O2 increase

4. History (cont.)
1.2 bya
Multicellular organisms arrise from cell divisions and specialization
Larger multicellular org. arrive around 600 mya
Snowball Earth (750 – 570 mya)
Limited locations of organisms
1st major diversification occurred 570 mya

5. Early Cambrian Most animal Phyla originated in 1st 20 my of Cambrian
500 mya
Fungi aid plants in taking water and nutrients
Plants supply food for Fungi
Plants transformed the landscape and allowed for terrestrial life
Insect  Amphibians  Reptiles
Reptiles became birds and mammals

6. Biogenesis Paradox Spontaneous Generation Louis Pasteur
Life – from – Life
Original Earth was very different
Little atmospheric O2
Abundance of Energy

7. Four-Stage Hypothesis for Life
Abiotic synthesis of small organic molecules
Joining of small molecules to form polymers
Origin of self-replicating molecules that made inheritance possible
Packaging of molecules into “Protobionts”

8. Abiotic Synthesis of Monomers
A.I. Oparin and J.B.S. Haldane (1920)
O2 prevents chemical bonds from forming
O3 blocks radiation
Younger suns produce more UV
Stanley Miller and Harold Urey (1953)
Using early earth conditions a.a. were formed
“Atmosphere”
Contained H2O, H2, CH4, NH3
Electrodes created lightning

9. Formation of Abiotic Polymers
Drip solutions of monomers onto hot sand, clay, or rock
Rain or waves could have washed monomers onto rocks
Polymers created and then washed back to sea

10. RNA as First Genetic Material
Molecular Replication in RNA world
Solution of nucleotides with RNA makes copies of RNA
Thomas Cech (1980s): RNA acts as catalyst
Natural Selection in RNA world
RNA contained both a genotype and phenotype
RNA may have held some a.a. long enough for them to bind

11. Protobionts form by Self Assembly
Liposomes form when organic ingredients contain lipids
Lipids organize into molecular bilayer
Stored energy as membrane potential
Liposomes sometimes engulf other liposomes
Liposomes sometimes create smaller liposomes

12. 5 Kingdom System Robert H. Whittaker (1969) Monera: All prokaryotes
Eukaryotes: separated according to diet
Plants: Produce food
Fungi: Heterotrophic decomposers
Animals: Ingestion followed by cavity digestion
Protista: Eukaryotes that did not fit into Plant, Animal, or Fungi

13. 3 Domain System Three domains exist above the Kingdoms
Archae
Bacteria
Eukarya
Monera Kingdom now obsolete

14. RNA Replication

15. Miller and Urey

16. Pasteur