1. Assignment Due Friday

2. What is...
LIFE??

3. Living Non-Living?

4. Organize the following into your table..
Toenail
Sun
Hair
Nerve Cell
Leaf
Fire
Tree bark
Water
Algae
Bacteria

5. What makes something alive?
Describe ways in which the “Baby” looked “alive”
What characteristics of living things are not shown by the “Baby”?

6. 10 Characteristics of Life
Organization
Reproduction
Growth & Development
Nutrition (feeding)
Respiration
6. Excretion 7. Responsiveness 8. Movement 9. Homeostasis 10. Evolution

14. Organize the following into your table..
Toenail
Sun
Hair
Nerve Cell
Leaf
Fire
Tree bark
Water
Algae
Bacteria

17. Origin of Life

19. Aristotle (384 –322 BC)
Proposed the theory of spontaneous generation
Also called abiogenesis
Idea that living things can arise from nonliving matter
Idea lasted almost years

20. Spontaneous Generation
For centuries, people based their beliefs on their interpretations of what they saw going on in the world around them without testing their ideas
They didn’t use the scientific method to arrive at answers to their questions
Their conclusions were based on untested observations
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21. Examples of Spontaneous Generation

22. 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

23. Example #1
Conclusion: It was perfectly obvious to people back then that muddy soil gave rise to the frogs

24. 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.

25. Example #2
Conclusion: It was obvious to them that the mice came from the moldy grain.

26. 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.

27. Example #3
Conclusion: Obviously, all the sewage and garbage turned into the rats.

28. Up to this point, science was based on observation and analysis…now, experiments were needed to test the hypothesis.

30. Disproving Spontaneous Generation

31. Francesco Redi
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32. Francesco Redi (1668)
In 1668, Francesco Redi, an Italian physician, did an experiment with flies and wide-mouth jars containing meat

33. Redi’s Experiment Redi used open & closed flasks which contained meat.
His hypothesis was that rotten meat does not turn into flies.
He observed these flasks to see in which one(s) maggots would develop.

34. Redi’s Findings
He found that if a flask was closed with a lid so adult flies could not get in, no maggots developed on the rotting meat within.
In a flask without a lid, maggots soon were seen in the meat because adult flies had laid eggs and more adult flies soon appeared.

35. Redi’s (1626-1697) Experiments
Evidence against spontaneous generation: 1. Unsealed – maggots on meat 2. Sealed – no maggots on meat 3. Gauze – few maggots on gauze, none on meat
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36. Results of Redi’s Experiments
The results of this experiment disproved the idea of spontaneous generation for larger organisms, but people still thought microscopic organisms like algae or bacteria could arise that way.

37. Disproving Spontaneous Generation of Microbes

38. Anton van Leeuwenhoek (1674)
Leeuwenhoek began making and looking through simple microscopes
He often made a new microscope for each specimen
He examined water and visualized tiny animals, fungi, algae, and single celled protozoa; “animalcules”
By end of 19th century, these organisms were called microbes

39. Anton van Leeuwenhoek 1632-1723
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40. Leeuwenhoek’s Microscope

41. John Needham (1745)
Showed that microorganisms flourished in various soups that had been exposed to the air
Claimed that there was a “life force” present in the molecules of all inorganic matter, including air and the oxygen in it, that could cause spontaneous generation to occur

42. Needham’s Results
Needham’s experiments seemed to support the idea of spontaneous generation
People didn’t realize bacteria were already present in Needham’s soups
Needham didn’t boil long enough to kill the microbes

43. Needham’s Experiment
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44. Lazzaro Spallanzani’s (1765)
Boiled soups for almost an hour and sealed containers by melting the slender necks closed.
The soups remained clear.
Later, he broke the seals & the soups became cloudy with microbes.

45. Spallanzani’s Results

46. Conclusion
Critics said sealed vials did not allow enough air for organisms to survive and that prolonged heating destroyed “life force”
Therefore, spontaneous generation remained the theory of the time

47. The Theory Finally Changes
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48. How Do Microbes Arise?
By 1860, the debate had become so heated that the Paris Academy of Sciences offered a prize for any experiments that would help resolve this conflict
The prize was claimed in 1864 by Louis Pasteur, as he published the results of an experiment he did to disproved spontaneous generation in microscopic organisms

49. Louis Pasteur ( )
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50. Pasteur's Experiment - Step 1
S-shaped Flask
Filled with broth
The special shaped was intended to trap any dust particles containing bacteria

51. Pasteur's Experiment - Step 2
Flasks boiled
Microbes Killed

52. Pasteur's Experiment - Step 3
Flask left at various locations
Did not turn cloudy
Microbes not found
Notice the dust that collected in the neck of the flask

53. And so, 2000 years after it started the debate of abiogenesis vs
And so, 2000 years after it started the debate of abiogenesis vs. biogenesis is settled: Biogenesis: Life comes from life, not from spontaneous generation of non-living things!!!