1. How Did Life Originate?

2. Remember: The Origin Of The Earth
~4.6 Billion years the earth was formed
~3.4 Billion years ago the first organisms appear
These blue-green algae made oxygen, which began to accumulate in the atmosphere.

3. Theories on the Origin of Life
Spontaneous Generation
Biogenesis
Divine Origins
Meteorites
“Primordial Soup”

4. Spontaneous Generation
The idea that organisms simply “appear” from non – living matter
Example: Maggots arose from rotting meat

5. Examples of Spontaneous Generation
Do not write the examples!!!!!!!!!!!
Examples of Spontaneous Generation
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Example #1
Observation: Every year in the spring, the Nile River flooded areas of Egypt along the river, leaving behind nutrient-rich mud that enabled the people to grow that year’s crop of food. However, along with the muddy soil, large numbers of frogs appeared that weren’t around in drier times
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Example #1
Conclusion: It was perfectly obvious to people back then that muddy soil gave rise to the frogs
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Example #2
Observation: In many parts of Europe, medieval farmers stored grain in barns with thatched roofs (like Shakespeare’s house). As a roof aged, it was not uncommon for it to start leaking. This could lead to spoiled or moldy grain, and of course there were lots of mice around.
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Example #2
Conclusion: It was obvious to them that the mice came from the moldy grain.
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Example #3
Observation: In the cities centuries ago, there were no sewers, no garbage trucks, no electricity, and no refrigeration. Sewage flowed down the streets, and chamber pots and left over food were thrown out into the streets each morning. Many cities also had major rat problems and a disease called Bubonic plague.
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Example #3
Conclusion: Obviously, all the sewage and garbage turned into the rats.
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Example #4
Observation: Since there were no refrigerators, the mandatory, daily trip to the butcher shop, especially in summer, meant battling the flies around the carcasses. Typically, carcasses were “hung by their heels,” and customers selected which chunk the butcher would carve off for them.
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Example #4
Conclusion: Obviously, the rotting meat that had been hanging in the sun all day was the source of the flies.
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14. Spontaneous Generation was disproved in 1668 by Francesco Redi, an Italian physician:
Used 3 samples of rotting flesh placed in flasks
open to air
sealed
covered with gauze
Maggots were generated in the open container, where flies had access to meat and were able to lay their eggs

15. Redi’s Experiment
Evidence against spontaneous generation: 1. Unsealed – maggots on meat 2. Sealed – no maggots on meat 3. Gauze – few maggots on gauze, none on meat

16. Redi’s experiments led to a new theory
Biogenesis:
Life can only come from pre-existing life.

17. More conclusive evidence for biogenesis
Louis Pasteur -1864
Experiment showed that life did not spontaneously appear

18. Pasteur’s experiment:
Meat broth was boiled in a flask to kill microorganisms
The neck of the flask was heated and bent into the shape of an S
Microorganisms could not get into broth because they would settle in S shaped neck before contact with broth
No growth was in discovered in the broth
Broth was tilted into the S component and microorganisms contaminated broth and grew

19. Diagram of Pasteur’s experiment

20. Divine Origins Christianity Judaism Islam Etc.
Each has their own belief of where life came from.

21. Image provided by NASA JPL
Or… Meteorite theory
Life came from space on comets
There is some evidence!
September 28, 1969 Murchison, Australia
Meteorite shower fell
Analysis determined it was carbon rich
Many organic compounds
Many of the protein amino acids found in biological systems
Image provided by NASA JPL

22. Primordial Soup Theory
Says that there was just the right mixture of chemicals on Earth, and life just appeared. Right time, right place!
Believe it or not, there is some experimental evidence for this, too.

23. Dr. Stanley Miller and Dr. Harold Urey-1953
Put the following ingredients into an elaborate flask apparatus:
ammonia (NH3)
methane (CH4)
water (H2O)
hydrogen (H2)
Electricity was passed through the apparatus
Amino Acids, sugars, and other small organic molecules were synthesized – the basis of life!

25. Which Theory Do You Think Is Correct?
The pros and cons to each theory
What evidence is there to support or disclaim a theory
For example: Fossil records
Could there be another theory?