1. History of the Earth
Chapter 14

3. Formation of the Earth

5. Where does life come from?
Spontaneous generation
the belief that living things arise from nonliving things
Biogenesis
all living things come from other living things
Redi’s experiments
Spallanzani’s experiments
Pasteur’s experiments

6. Redi’s Experiment ( )
Italian physician and poet who demonstrated that the presence of maggots on rotting meat does not result from spontaneous generation but from eggs laid on the meat by flies.
Pg. 279

7. Spallanzani’s Experiments (1729-1799)
Italian naturalist whose experiments disproved that microorganisms spontaneously generated from meat broth in open flasks.
Pg. 280

8. Pasteur’s Experiment (1822-1895)
A French chemist who proved that microorganisms are carried by dust and not air.
Improved on Spallanzani’s experiment
Pg. 281

10. The First Organic Compounds
Alexander Oparin’s Hypothesis, 1920’s):
Thought that primitive atmosphere contained: NH3, H2, H20, and C-H compounds
At high temperatures, these gases might have formed simple organic compounds like amino acids

11. Oparin’s Theory Con’t
When the Earth cooled, the water vapor condensed into lakes and seas with the organic compounds within
With the help of lightening and UV radiation, these organic compounds reacted with each other forming macromolecules essential to life.

12. Can that REALLY happen?
Yes! According to experiments performed by Miller and Urey
Products of experimental synthesis:
Amino acids
ATP
DNA nucleotides

13. Attempts to Create Life
Miller Experiment
Spark Chamber
Input Chamber
Condenser
Water Vapor Forms

14. Life began in Hydrothermal Vents
Extreme conditions: high heat, acid levels, pressure, gases
Sun cannot reach the bottom of the ocean
Chemosynthesis- organisms making their own energy from the chemicals in their enviro. (similar to photosynthesis)
Currently populated by Archae

15. Vents cont.
Scientists have also traced the DNA of all currently living organisms back to a common ancestor extremophile that would have been found in the hydrothermal vents.

16. “It came from outer space!”
Some scientists hypothesize that organic compounds may have come from meteoroids from space

17. Earth’s Age More than 4 BILLION years old!
How do scientists “know” this?
Radiometric dating
Measurement of the decay of commonly occurring radioactive isotopes
Ex) Carbon dating

18. Fossils The remains of ancient animals and plants
Found in every continent on earth
Formed from sedimentary rock
Paleontology- the branch of biology that studies past forms of life (namely fossils!)

19. Ancient Bat Saber-Toothed Cat

20. The Fossil Record
From the 1830s onwards, geologists noted how fossils became more complex through time. The oldest rocks contained no fossils, then came simple sea creatures, then more complex ones like fishes, then came life on land, then reptiles, then mammals, and finally humans. Clearly, there was some kind of 'progress' going on.

21. The First Prokaryotes About 3.5 bya the first prokaryotes,
cells without a true nucleus (like bacteria), came into existence.
The first cells were probably anaerobic and heterotrophic.
Video

22. Prokaryotes cont.
Resemble modern day Archaebacteria, which live in extreme environments
Chemosynthesis- the conversion of carbon molecules (like CO2 or methane) into organic compounds without the use of sunlight
energy is obtained from an
inorganic substance like sulfur,
hydrogen gas, or methane

23. Rise of photosynthesis and aerobic respiration
Cyanobacteria- group of unicellular, autotrophic prokaryotes about 3 bya
Increased the level of atmospheric oxygen

24. The First Eukaryotes
Endosymbiosis- about 2.0 bya, a small aerobic prokaryote began to live inside a larger anaerobic prokaryote
aerobic prokaryotes evolved to modern mitochondria
Photosynthetic cyanobacteria evolved into chloroplasts
video

25. Endosymbiosis: From prokaryotes to eukaryotes

26. Ch. 14 Notebook Quiz What does the term biogenesis mean?
Explain how Redi’s experiment disproved the hypothesis that flies formed by spontaneous generation.
What is the Earth’s age? How do we know this?
According to Oparin, what molecules were in Earth’s early atmosphere?
What process increased the level of oxygen in the atmosphere about 3 bya?
Explain the theory of endosymbiosis.