Transcript Spontaneous Generation

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The idea that non-living objects could give
rise to living things.
* For centuries, people based their beliefs on
their interpretations of what they saw going on
in the world around them without testing their
ideas to determine the validity of them.
* In other words, they did not use the scientific
method. Their conclusions were just based on
untested observations.
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* For centuries it was common knowledge that
simple organisms like worms, beetles, frogs,
flies and salamanders could come from dust,
mud, food, garbage, etc.
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* Every year in the spring, the Nile River flooded
areas of Egypt along the river, leaving mud that
enabled the people to grow that year’s crop of
food. However, along with the mud, large
numbers of frogs appeared that weren’t around
in drier times.
* It was obvious to the people that muddy soil
gave rise to the frogs.
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* In many parts of Europe, medieval farmers
stored grain in barns with thatched rooves. As
a roof aged, it was not uncommon for it to
start leaking. This could lead to spoiled or
moldy grain, and of course mice.
* It was obvious to them that the mice came
from the moldy grain.
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* In early cities, there were no sewers and no
garbage trucks. Garbage and the contents of
chamber pots were tossed out the nearest
window. Rats were rampant on the city streets
and not as common in the country.
* It was obvious to the people that rats were a
product of garbage.
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* Since there were no refrigerators, the daily
trip to the butcher shop meant battling the
flies around the carcasses.
* Obviously, the rotting meat that had been
hanging in the sun all day was the source of the
flies.
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* In 1668, Francesco Redi, an Italian
physician did an experiment with
flies and wide-mouth jars containing meat.
The picture represents the three jars and
the variables he used.
* Conclusion:
In the uncovered jars, flies entered and laid eggs on
meat. Maggots hatched and turned into adult flies. No flies
could get into the sealed jars, and hence, no maggots hatched.
In the gauze covered jars, flies and maggots appeared on the
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aapp
gauze.
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* After this experiment, people were willing to
acknowledge that organisms visible to the
naked eye didn’t arise by spontaneous
generation but had to have parents.
* With the development and refinement of the
microscope in the 1600s, people began seeing
all sorts of new life forms such as yeast, other
fungi, bacteria and various protists. Then then
believed just these tiny organisms came by
spontaneous generation.
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* In the 1700s John Needham, a Scottish naturalist, and Spallanzani,
an Italian biologist, tested soups and the growth of microorganisms.
Needham claimed there was a “life force” present in the molecules
in non-living matter like air and oxygen that could cause
spontaneous generation to occur because he had bacteria in his
soup.
* Spallanzani found that one hour of boiling could sterilize the soup so
that no microorganisms grew. He felt that the microorganisms were
already in the broth and not from the air.
* Needham was concerned that Spallanzani had destroyed the life
force with his extensive boiling.
* They argued over who was right.
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* Louis Pasteur tested the notion about life
force and sterilization to settle the debate.
* He proved that only when bacteria are able to
get into the soup did it result in the growth of
bacteria.
* Hence, bacteria also have to have a parent.
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* Reproduction
is now one of the
characteristics of all living things.
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