1. The History of Life on Earth
AP Biology
Crosby High School

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

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

4. 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

5. 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

6. 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

7. 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

8. Fossil Record Generally result from bone or organic remains
Some preserved plant leaves
Amber and Ice
Trace Fossils: fossilized behavior
Fossilization is rare:
Organism must die under proper conditions
Must not be destroyed
Must be found

9. Dating Fossils Relative Dating: Lower rock is older Absolute Dating
Geologic Time Scale
Era: Separated by times of Mass Extinction
Period: Mark lesser extinctions
Epoch
Absolute Dating
Radiometric Dating: Measure radioactive isotopes in fossils
Racemization: Measure rate of change from L-a. a.  D- a.a.

10. 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

11. 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

12. Eukaryotic Origins Multicellular prokaryotes
Complex communities of prokaryotes
Compartmentalization
Infolding
Endosymbiosis

13. Mitochondria and Chloroplasts
Theory of Serial Endosymbiosis
Mitochondria: aerobic Heterotrophic bacteria
Chloroplasts: Photosynthetic bacteria
Both engulfed and became mutualistic
Heterotrophic host could have used photosynthetic symbionts
Anaerobe could have used aerobic endosymbionts
Mitochondria most likely first

14. Serial Endosymbiosis Support
Size
Enzymes and transport systems
Replication
Ribosomes

15. Eukaryotic Chimera Ancestors Gene Transfer to Nucleus
Mitochondria: α Proteobacteria
Plastid: Cyanobacteria
Compared the SSU-rRNA
Gene Transfer to Nucleus
Transformation resulted in nuclear DNA containing codes for part of mit. production

16. 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

17. 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

18. Phylogeny and Biogeography
250 mya (End of Paleozoic Era)
Pangaea formed
Ocean basins deepened
Sea level dropped
Both aquatic and terrestrial environments affected
180 mya
Pangaea separated creating Isolation

19. Permian Mass Extinction (250 mya)
Killed 96% of marine species
Pangaea formation
Massive volcanic Eruptions (Siberia)
Production of Carbon Dioxide
Oxygen deficit in the oceans

20. Cretaceous Mass Extinction (65 mya)
Climate cooled and shallow seas receded
Large volcanic Eruptions (India) may have blocked the sunlight
Impact Hypothesis
Killed the Dinosaurs along with many other lifeforms

21. Impact Hypothesis Asteroid Collided with Earth
Iridium layer of clay
Chicxulub Crater
Collision lead to Cretaceous Mass Extinction
Could have darkened the Earth for years
Would have caused Severe Acid Precipitation
Would have sent fiery debris to N. Am.

22. 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

23. 3 Domain System Three domains exist above the Kingdoms
Archae
Bacteria
Eukarya
Monera Kingdom now obsolete

24. RNA Replication

25. Miller and Urey

26. Pasteur

27. Asteroid Collision

29. Endosymbiosis