Where does life come from? Spontaneous Generation vs Biogenesis

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.

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

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

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.

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

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

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

Pasteur Continued Conclusions: Disprove spontaneous generation.