Science

Nik Jameson Accelerated Biology 3/7/09

__Spontaneous Generation__ Spontaneous Generation is an obsolete theory regarding the origin of life. Spontaneous generation is the hypothetical process by which living organisms develop from nonliving matter. Francisco Redi- Francisco Redi opposed spontaneous generation and his experiment, which was done in 1668, was believed to be one of the first steps in refuting the theory. In his experiment, Redi filled six jars with decaying meat. Three of these jars he sealed, and the other three he left open. In the open jars maggots developed when flies laid their eggs on the decaying meat. But in the sealed jars of meat, flies could not enter and lay eggs, and maggots did not develop. Francisco Redi's experiment showed that dead meat does not give rise spontaneously to maggots, but still some individuals supported the theory (Redi then did a second experiment in which he put a net over three jars instead of sealing or leaving it open, and maggots still did not develop.) John Needham- John Needham supported spontaneous generation. In his experiment, done in 1745, Needham boiled gravy and put it in a sealed flask. He waited and after a while microorganisms grew. Due to this Needham believed that spontaneous did exist because microorganisms did appear after boiling. Lazzaro Spallanzani- Spallanzani did not support spontaneous generation, which he believed that he proved during his experiment. Spallanzani's experiment was basically a different form of Needham's experiment. Spallanzani believed that the microorganisms might have entered the gravy after being boiled but before being sealed so he took Needham's experiment to another level. Lazzaro put the gravy in a sealed flask and then boiled it. And sure enough no microorganisms grew. Though still, spontaneous generation had supporters who only believed that it could not take place without air. Louis Pasteur- Louis Pasteur did not support spontaneous generation. In his experiment, Pasteur boiled meat broth/gravy in a flask. Next he heated the neck of this flask until it became pliable. He then bent the flask into the shape of an S so that air could enter the flask, but microorganisms in the air could not (they would get stuck, due to gravity, in the neck of the flask). In the end no microorganisms grew. Pasteur's experiment proved two things: spontaneous generation did not exist and that microorganisms are everywhere.