1. Origin and History of Life
Chapter 19
Mader: Biology 8th Ed.

2. Outline Primitive Earth Origin of First Cells Fossils The Precambrian
The Paleozoic
The Mesozoic
The Cenozoic
Continental Drift
Mass Extinctions
Mader: Biology 8th Ed.

3. Originally too hot for anything but water vapor to form.
The Primitive Earth
Primitive atmosphere most likely consisted of water vapor, nitrogen, and carbon dioxide, with small amounts of hydrogen and carbon monoxide.
Little free oxygen.
Originally too hot for anything but water vapor to form.
Earth cooled and water vapor condensed to liquid water.
Mader: Biology 8th Ed.

4. Monomers Evolve
Stanley Miller (1953) conducted an experiment to show the first organic molecules could have been produced from primitive atmospheric gases in the presence of strong energy sources.
Mader: Biology 8th Ed.

5. Monomers join to form polymers in the presence of enzymes.
Polymers Evolve
Monomers join to form polymers in the presence of enzymes.
Protein-First Hypothesis assumes DNA genes came after protein enzymes arose.
RNA-First Hypothesis suggests only RNA was needed to progress toward formation of the first cell or cells.
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6. Protocells would have been precursors to the first true cells.
Protocell Evolves
Protocells would have been precursors to the first true cells.
A protocell is a structure with a lipid-protein membrane that carries on energy metabolism.
Semipermeable-type boundary may form around coacervate droplets.
Liposomes form in liquid environments.
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7. Protocell Anatomy
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8. Origin of First Cells
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9. Fossils are remains and traces of past life.
Great majority are found embedded in, or recently eroded from, sedimentary rock.
Sediment becomes a stratum.
Recognizable layer in stratigraphic sequence.
Paleontology is the study of the fossil record.
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10. Fossils
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11. Relative Dating of Fossils
Strata change their character over great distances.
A stratum of the same age tends to contain the same fossil.
Helps geologists determine relative dates of the strata despite upheavals.
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12. Strata
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13. Absolute Dating of Fossils
One absolute dating method relies on radioactive dating techniques.
All radioactive isotopes have a particular half-life.
Length of time it takes for half of the radioactive isotope to change into another stable element.
Compare radioactivity of a fossil to that of a modern sample of organic matter.
Mader: Biology 8th Ed.

14. Comprises about 87% of the geological timescale.
The Precambrian
Comprises about 87% of the geological timescale.
First cells came into existence.
Prokaryotes
Cyanobacteria in ancient stromatolites added oxygen to the atmosphere.
Lack of ozone shield allowed UV radiation to bombard Earth.
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15. Prokaryote Fossil of Precambrian
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16. Eukaryotic Cells Arise Eukaryotic cell arose about 2 bya.
The Precambrian
Eukaryotic Cells Arise
Eukaryotic cell arose about 2 bya.
Nearly always aerobic and contains nucleus as well as other membranous organelles.
Endosymbiotic Hypothesis.
Multicellularity Arises
Multicellularity arose approximately 1 billion years later (1.4 bya).
Mader: Biology 8th Ed.

17. The Paleozoic era lasted over 300 million years.
Contained three major mass extinctions.
Disappearance of a large number of species, or a higher taxonomic group, within a relatively small time interval.
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18. Cambrian Animals
Molecular Clock is based on principle that DNA differences in certain parts of the genome occur at fixed rate, and are not tied to natural selection.
Number of base-pair differences tells how long two species have been evolving separately.
High Cambrian diversity may be due to the evolution of outer skeletons.
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19. Cambrian Sea Life
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20. Evolution of fishes began in Ordovician.
Invasion of Land
Plants
Seedless vascular plants date back to Silurian period and later flourished in Carboniferous period.
Invertebrates
Outer skeleton and jointed appendages of arthropods are adaptive to living on land.
Vertebrates
Evolution of fishes began in Ordovician.
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21. Nonflowering seed plants became dominant.
The Mesozoic Era
Evolution of many plants and animals continued into the Triassic, the first period of the Mesozoic era.
Nonflowering seed plants became dominant.
Dinosaurs achieved enormous size.
Mammals remained small and insignificant.
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22. Flowering plants already diverse and plentiful.
The Cenozoic Era
Mammals began an adaptive radiation at the end of the Mesozoic era, moving into habitats left vacant by the demise of dinosaurs.
Flowering plants already diverse and plentiful.
Primate evolution began.
Mader: Biology 8th Ed.

23. Factors That Influence Evolution
Continental Drift
Positions of continents and oceans are not fixed.
Modern mammalian biological diversity is the result of isolated evolution on separate continents.
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24. Continental Drift
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25. Continental Drift Plate Tectonics
Movements of Earth’s crust which is fragmented into slablike plates that float on a lower hot mantle layer.
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26. Plate Tectonics
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27. Loss of 70% of marine invertebrates
Mass Extinctions
At least five mass extinctions have occurred throughout history. At the ends of:
Ordovician
Continental Drift
Devonian
Bolide Event
Loss of 70% of marine invertebrates
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28. Loss of 90% of ocean species. Triassic Meteorite Collision Cretaceous
Mass Extinctions
Permian
Excess carbon dioxide.
Loss of 90% of ocean species.
Triassic
Meteorite Collision
Cretaceous
Mader: Biology 8th Ed.

29. Review Primitive Earth Origin of First Cells Fossils The Precambrian
The Paleozoic
The Mesozoic
The Cenozoic
Continental Drift
Mass Extinctions
Mader: Biology 8th Ed.

30. Mader: Biology 8th Ed.