Francesco Redi performed an experiment in 1668 that disproved the theory of spontaneous generation. He took two identical pieces of meat and placed them in sealed jars, with one covered to prevent flies from entering. Only the uncovered jar grew maggots, showing that living things arise from other living things, not non-living matter. Louis Pasteur further disproved spontaneous generation through experiments showing that microbes could only enter sterile broth through airborne dust, not by generating within the broth itself. This led to the theory of biogenesis, that all life arises from pre-existing life. While life on Earth is believed to have begun around 3.5 billion years ago, scientists have proposed theories of how simple
2. A. Spontaneous Generation
1. Theory that living things could come from non-
living things.
a. Rain creates worms; meat grows maggots.
2. This theory was accepted for hundreds of years.
a. Scientists did not believe this and had to prove it
wrong.
3. 3. 1668 Francesco Redi tested the maggots and
meat belief.
a. Took 2 identical raw pieces of meat and put them into
2 identical jars.
b. Covered one of them with a piece of light cloth. (so air
could get through)
c. Waited.
d. Upon his return he found that the uncovered jar had
maggots on the meat, but the covered jar did not.
e. Since both jars did not have maggots, he stated that
SG (Spontaneous Generation) had to be wrong.
f. His experiment did not disprove SG entirely.
5. B. Louis Pasteur and Biogenesis.
1. Louis Pasteur was a French chemist that tested
broth. (meat juices)
a. Boiled broth to make it sterile.
b. Placed into an s-shaped flask. (these flasks allows air
to enter the broth but not dust; all the dust gets
caught in the curve of the S.
c. Upon return he found no contamination to any of the
flasks.
d. He then tilted the flask so the dust could enter the
broth, within days it was contaminated.
e. Concluded that broth does not make germs, but is
contaminated by the dust in the air.
7. 2. Pasteur’s experiment led to the theory of
BIOGENSIS.
a. Living things come only from other living things.
b. See page 20 in your textbook!!!!
8. C. Life’s Origin
1. Earth is believe to be 4.6 billion years old.
2. The oldest found life is about 3.5 billion years
old.
3. 1924 Alex Oparin: Russian scientist suggested
Earth’s atmosphere had no oxygen in it but had
ammonia, hydrogen, methane, and water vapor.
a. Believed these gases combined to form the simplest
form of life (bacteria) and then the evolution cycle
began.
b. This is only one belief of how life was created!!!!
