Spontaneous Generation
What is this theory?
Many believed spontaneous generation:
life can arise from non-living matter
In 1668, the Italian physician Francesco
Redi performed an experiment to disprove
spontaneous generation.
Can you think of an experiment that could
disprove spontaneous generation?
Redi filled six jars with decaying meat.
Conditions
Results
3 jars covered with
fine net
3 open jars
No maggots
Maggots appeared
From where did the maggots come?
What was the purpose of the sealed jars?
Spontaneous generation or biogenesis?
Spontaneous
Generation
Redi’s
Experiment
Theory of Biogenesis
Francesco Redi 1688 placed meat in 6 widemouthed jars. Three were covered with a
type of wide weave cloth – three jars were
left open.
All jars turned gray and began to issue
vapors, but only the meat in the uncovered
jars were able to be transformed into flies.
Controlled experiment. Why?
Lazzaro Spallanzani
Late 1700’s
Designed an experiment to show that tiny
organisms came from other tiny organisms in
the air
Sterilized broth in two flasks, sealed one and
left the other open to the air
The open flask became cloudy with
organisms
The sealed one developed no organisms
Showed that organisms from the air entered
one flask and not the other because it was
sealed
Lazzaro Spallanzani
So now there are two hypotheses:
The hypothesis that living organisms arise
from nonliving matter is called spontaneous
generation. According to spontaneous
generation, a “vital force’ Forms life.
The alternative hypothesis, that the living
organisms arise from preexisting life, is
called biogenesis.
1861: Louis Pasteur demonstrated that
microorganisms are present in the air.
Conditions
Results
Nutrient broth placed Microbial growth
in flask, heated, not
sealed
Nutrient broth placed No microbial growth
in flask, heated, then
sealed
Spontaneous generation or biogenesis?
Spontaneous Generation of Life
Life arises from no living matter
The Theory of Biogenesis
Life arises from pre-existing cells
Pasteur’s S-shaped flask kept microbes out but
let air in. These experiments form the basis of
his technique.
Pasteur demonstrated that
these spoilage bacteria
could be killed by heat that
was not hot enough to
evaporate the alcohol in
wine. This application of a
high heat for a short time
is called pasteurization.
Early Microbiology
1861 - Pasteur dispells
theory of “spontaneous
generation”
1864 - Pasteur invents
pasteurization of wine.
Saves the French wine
industry.
The Origin of Life
Alexander Oparin
In the 1930s, a Russian scientist, Alexander Oparin,
hypothesized that life began in the oceans on early earth
between 3.9 to 3.5 billion years ago.
He suggested that first, simple organic molecules
containing carbon formed. Energy from the sun,
lightning, and earth's heat triggered chemical reactions
to produce small organic molecules from substances
present in the atmosphere.
These molecules were organized by chance into complex
organic molecules such as proteins, carbohydrates, and
nucleic acids that are essential to life.
The Formation of Amino Acids –
Miller's Experiment
Attempting to prove Oparin's hypothesis, two American
scientists, Stanley Miller and Harold Urey, carried out an
experiment in which they attempted to simulate early earth
conditions according to evolutionists.
They mixed water vapor with ammonia, methane, and
hydrogen gases. They then sent an electric current that
simulated lightning through the mixture. Then they cooled
the mixture of gases, producing a liquid that simulated
rain.
After a week, they collected the liquid in a flask and
analyzed the chemicals therein. They found that three
amino acids (amino acids constitute the basic elements of
proteins, which are the building blocks of living cells) were
created.
This experiment was claimed as proof for Oparin's
hypothesis.
Miller and Urey’s Experiment