2. Target of the Day!
◍ identify the sequence of events of the
history of life on earth;
◍ name the pieces of evidence on the
evolution of life on earth;
◍ recognize the importance of knowing
the history of life on earth
2
5. The Earth’s Timeline
◍ 4.6 BYA – Earliest Geologic Record of
the Earth
○ This would also pertain to the “Earth’s Age”
◍ Violent, Chaotic and Disorder
○ 4.6-3.8 BYA - because of the meteorites and
volcanic eruptions. With this condition, zircon
crystal was formed.
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6. The Earth’s Timeline
◍ Early Atmosphere
○ Probably contained CO2, CO, Nitrogen, Ammonia,
Methane
○ But, No Oxygen! (wouldn’t support life)
◍ 3.8 BYA
○ Earth cooled enough for liquid water to
form
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7. When did Life Began?
◍ 4.28 BYA
○ Fossils (microfossils) discovered in
hydrothermal vent precipitates
◍ 3.5 BYA
○ Life on Earth initially began with prokaryotes,
discovered in sedimentary rock formations called
stromatolites.
◍ Prokaryotes – cells that do not have
Nucleus (Bacteria and Archea) 7
8. Going back…
◍ Early Atmosphere
○ Probably contained CO2, CO, Nitrogen, Ammonia,
Methane
○ But, No Oxygen! (wouldn’t support life)
◍ Anaerobic organism – capable of
surviving without oxygen
◍ 3.0 BYA - The first photosynthetic
organism thrived the earth which is blue
green algae called cyanobacteria. 8
9. The Earth’s Timeline
◍ Unicellular organisms >> Multicellular
Organism
◍ 2.0 BYA - Appearance of the first
eukaryotes and the influx of
multicellular organisms occurred 1.2
billion years ago.
○ Eukaryotes – multicellular, with true nucleus
○ The first eukaryotes were protists
◍ Evolution play a pivotal role
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11. The Earth’s timeline
◍ 500 MYA The Paleozoic era when the
trilobites and cephalopods became
dominant in the ocean particularly
during the
Cambrian and Ordovician
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12. 251 to 65.5 MYA
◍ The Mesozoic era-the age of reptiles
that has a span of 251 to 65.5 MYA
divided into Triassic, Jurassic and
Cretaceous period
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22. THEORIES ON THE ORIGIN OF LIFE
◍ DIVINE CREATION
○ Life is created by a Supreme Being.
◍ ABIOGENESIS THEORY (SPONTANEOUS
GENERATION)
○ Life could appear from non-living material
◍ BIOGENESIS THEORY
○ Life could appear from living material
◍ PANSPERMIA THEORY
○ Extraterrestrial Origin
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29. Classical Experiments on Evolution of
Life
Italian physician and poet, Francesco Redi
(1668)
◍ Hypothesis: Maggots arose from tiny,
non-visible eggs laid on meat
◍ Procedures:
○ Put pieces of meat in several jars, leaving half
open to the air
○ Cover the other half with thin gauze to prevent
entrance of flies
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30. Classical Experiments on Evolution of
Life
◍ Results:
After a few days, meat in all jars
spoiled and maggots were found
only on the meat in the uncovered
jars
One of the first documented
experiments to use a control!
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38. Classical Experiments on Evolution of
Life
◍ French scientist, Louis Pasteur (1859)
○ The French Academy of Sciences held a contest for the best
experiment either proving or disproving spontaneous generation
◍ Hypothesis: Microorganisms do not arise from meat
broth
◍ Procedures:
○ Place meat broth in a flask with a long, curved neck. (This permitted
air to enter, but trapped dust and other airborne particles)
○ Boil the flask thoroughly to kill any microorganisms
○ Do NOT seal the open end of the flask
○ Wait an entire year before gathering results 38
39. Classical Experiments on Evolution of
Life
◍ Results:
○ After a year, no microorganisms could be
found in the broth!
○ Pasteur then removed the curved neck,
permitting dust and other particles to
enter. In just one day, the flask contained
microorganisms!
○ Microorganisms had clearly entered the
flask with the dust particles from the air
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Theory of Biochemical Evolution: Several models for the origin of life have been suggested. The first 'modern' model for the origin of life was presented in the 1923 independently by the Russian biochemist A. I. Oparin and later supported by the British evolutionary biologist J. B. S. Haldane in 1928. The Oparin and Haldane theory is known as biochemical theory for the origin of life.
According to the Oparin-Haldane model, life could have arisen through a series of organic chemical reactions that produced ever more complex biochemical structures. They proposed that common gases in the early Earth atmosphere combined to form simple organic chemicals, and that these in turn combined to form more complex molecules. Then, the complex molecules became separated from the surrounding medium, and acquired some of the characters of living organisms. They became able to absorb nutrients, to grow, to divide (reproduce), and so on
