Spontaneous Generation
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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.

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Spontaneous Generation What is this theory?

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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.

Spontaneous Generation

Redi’s Experiment

Theory of Biogenesis

  • Francesco Redi 1688 placed meat in 6 wide-mouthed 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.

  • 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

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