1. Where does life come from?
Spontaneous Generation vs Biogenesis

2. Spontaneous Generation
Early belief: non-living objects can give rise to living organisms (abiogenesis)‏
Not tested
Based on observations: Every year the Nile floods. There are many frogs soon after, appearing from the muddy soil. Thus, the mud made frogs
Recipe for mice: Place a dirty shirt or some rags in an open pot or barrel containing a few grains of wheat or some wheat bran, and in 21 days, mice will appear. There will be adult males and females present, and they will be capable of mating and reproducing more mice.

3. Test of Spontaneous Generation
Francisco Redi, 1668
Observation: there are flies around meat carcasses
Hypothesis: Rotting meat does not turn into flies. Flies make more flies
Test: Wide mouth jars with meat

4. Redi's Test Control: Jars without lids
Experimental group: Some jars with lids, some with gauze over opening

5. Redi's Experiment Data: record presence or absence of maggots
Control: flies enter jars, many maggots in meat
Lids: no flies enter, no maggots
Gauze: some flies around gauze, few maggots
Conclusion: Only flies make more flies. Flies entered and laid eggs, making maggots.
Spontaneous generation disproved.

6. Further Developments Late 1600s: use of microscopes 1745: John Needham
1674: Anton van Leeuwenhoek
1745: John Needham
Life force in inorganic matter causes life to arise
1765: Lazzaro Spallanzani
Boiled broth, sealed in glass container and left open
Arguments with Needham regarding boiling
1860: Paris Academy of Sciences offers prize for resolution

7. Louis Pasteur 1864 Observations: Contact with air causes broth to rot
Bacteria can be filtered from air
Bacteria collect in dust
Hypothesis
Bacteria, not air, causes broth to go bad
Test
Boiled broth
Control: open upright neck flasks
Experimental group: swan-neck flask, some open, some with cottonplug

8. Pasteur Continued Results: Straight up necks have cloudiness, spoiled
Swan necks have no cloudiness

9. Pasteur Continued
Conclusions:
Disprove spontaneous generation.