Transcript document

Origin of Life
Honors Biology
2006
ANCIENT MICROBIOLOGICAL HISTORY
Ancient man recognized many of the factors involved in
disease. Early civilizations on Crete, India, Pakistan and
Scotland invented toilets and sewers; lavatories, dating
around 2800 BC, have been found on the Orkney islands and
in homes in Pakistan about the same time. One archaeologist
has stated that "The high quality of the sanitary
arrangements [in ~2500 BC] could well be envied in many
parts of the world today". In Rome, 315 AD, the public
lavatories were places where people routinely socialized and
conducted business. The Chinese used TOILET PAPER as
early as AD 589. In Europe moss, hay and straw were used
for the same purpose.
History of Microbes
• Most ancient peoples recognized that some diseases were
communicable and isolated individuals thought to carry "infections".
An example of this is the universal shunning of lepers, which occurs
even today. When the Black Death struck Europe, entire villages were
abandoned as people fled in an effort to escape the highly infectious
plague. Similarly, in the Middle Ages the rich of Europe fled to their
country homes when small pox struck in an effort to escape its terrible
consequences. The fact that people who recovered from a particular
disease were immune to that disease was probably recognized many
different times in many places. Often these survivors were expected to
nurse the ill. Greek and Roman physicians routinely prescribed diet
and exercise as a treatment for ills.
• Ancient people had certainly seen masses of microbes, such as mold
and bacterial colonies, on spoiled food, but it is doubtful if anyone
considered that they were VIEWING living organisms.
Spontaneous Generation
• It was once widely thought that
living things could arise from
non-living things in a process
called SPONTANEOUS
GENERATION.
• Why is this not possible?
• BIOGENESIS - All living
things come from other living
things
Redi’s Experiment
• Redi's Problem
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Where do maggots come from?
Hypothesis: Maggots come from flies.
Redi put meat into three separate jars.
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Jar 1 was left open
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Jar 2 was covered with netting
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Jar 3 was sealed from the outside
Redi's Experiment Step 1
• Jar-1
• Left open
• Maggots developed
• Flies were observed laying
eggs on the meat in the open
jar
Redi's Experiment Step 2
• Jar-2
• Covered with netting
• Maggots appeared on the netting
• Flies were observed laying eggs on the
netting
Redi's Experiment Step 3
• Jar-3
• Sealed
• No maggots developed
Redi's Experiment Results
What did Redi's experiment show?
Was his hypothesis correct or incorrect?
Lazzaro Spallanzani
• One of the first to
disprove spontaneous
generation. An Italian
scientist who proved
microorganisms could
be killed by boiling.
(Italian 1767)
Spallanzani's Problem
• What causes microbes to form in decaying broth?
• Hypothesis: Microbes come from the air. Boiling will kill
microorganisms.
• Spallanzani put broth into four flasks
• Flask 1 was left open
• Flask 2 was sealed
• Flask 3 was boiled and then left open
• Flask 4 was boiled and then sealed
Spallanzani's Experiment Step 1
• Flask-1
• Left Open
• Turned cloudy
• Microbes were found
Spallanzani's Experiment Step 2
• Flask-2
• Sealed
• Turned cloudy
• Microbes were found
Spallanzani's Experiment Step 3
• Flask-3
• Boiled and left open
• Turned cloudy
• Microbes were found
Spallanzani's Experiment Step 4
• Flask-4
• Boiled and sealed
• Did not turn cloudy
• Microbes not found
• Spallanzani's Experiment Results
• What did Spallanzani's experiment show?
• Was his hypothesis correct or incorrect?
Louis Pasteur (1822-1895)
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Pasteur championed changes in
hospital practices to minimize the
spread of disease by microbes.
He discovered that weakened forms
of a microbe could be used as an
immunization against more virulent
forms of the microbe.
Pasteur found that rabies was
transmitted by agents so small they
could not be seen under a
microscope, thus revealing the
world of viruses.
Pasteur developed "pasteurization",
a process by which harmful
microbes in perishable food
products are destroyed using heat,
without destroying the food.
Pasteur's Problem
• Where do the microbes come from to cause broth to decay.
• Hypothesis: Microbes come from cells of organisms on dust particles
in the air; not the air itself.
• Pasteur put broth into several special S-shaped flasks
• Each flask was boiled and placed at various locations
Pasteur's Experiment Step 1
• S-shaped Flask
• Filled with broth
• The special shaped was
intended to trap any dust
particles coming in.
Pasteur's Experiment Step 2
• Flasks boiled
• Flasks boiled
• Micropes Killed
Pasteur's Experiment Step 3
• Flask Left Out
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Flask left at various
locations
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Did not turn cloudy
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Microbes not found
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Notice the dust that collected
in the neck of the flask
Pasteur's Experiment Results
• What did Pasteur's experiment show?
• Was his hypothesis correct or incorrect?
First Organic Compounds
• All the elements found in organic
compounds are thought to have existed on
Earth when it formed
• But how and where were these elements
assembled into organic compounds found in
life?
Alexander I. Oparin (1894-1980)
• Proposed a hypothesis
for how life formed in
1923
• Suggested that the
primitive Earth was
very different than
today
– NH3, H2, H2O, CH4
Miller-Urey Experiment
•
By the 1950s, scientists were in hot
pursuit of the origin of life. Around
the world, the scientific community
was examining what kind of
environment would be needed to
allow life to begin. In 1953,
Stanley L. Miller and Harold C.
Urey, working at the University of
Chicago, conducted an experiment
which would change the approach
of scientific investigation into the
origin of life.
QuickTime™ and a
TIFF (Uncompressed) decompressor
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Miller/Urey Experiment
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Miller took molecules which were
believed to represent the major
components of the early Earth's
atmosphere and put them into a
closed system
The gases they used were methane
(CH4), ammonia (NH3), hydrogen
(H2), and water (H2O).
Next, he ran a continuous electric
current through the system, to
simulate lightning storms believed
to be common on the early earth.
Miller and Urey Conclusions
• Analysis of the experiment was done by chromotography.
• At the end of one week, Miller observed that as much as 10-15% of the
carbon was now in the form of organic compounds.
• Two percent of the carbon had formed some of the amino acids which
are used to make proteins.
• Perhaps most importantly, Miller's experiment showed that organic
compounds such as amino acids, which are essential to cellular life,
could be made easily under the conditions that scientists believed to be
present on the early earth