Spontaneous Generation & Biogenesis Lesson

The Slow Death of Spontaneous Generation (1668-1859) Name ______Date ______Period ______# ______Russell Levine and Chris Evers Spontaneous Generation & Biogenesis Lesson (pages 8-14) From the timehttp://www.sumanasinc.com/webcontent/animations/content/scientificmethod.html of the ancient Romans, through the Middle Ages, and until the late nineteenth century, it was generally acceptedhttp://www.phschool.com/atschool/phsciexp/active_art/redi_pasteur_experiment/ that some life forms arose spontaneously from non-living matter. Such "spontaneous Spontaneousgeneration" appeared generation to –occur primarily in decaying matter. For example, a seventeenth century recipe for the spontaneous production of mice required placing sweaty underwear and husks of wheat in an open- Biogenesismouthed jar, – then waiting for about 21 days, during which time it was alleged that the sweat from the underwear would penetrate the husks of wheat, changing them into mice. Although such a concept may Scientificseem laughable today,Redi’s it is consistent Experiment with (1668) the other widelySpallanzani’s held cultural Experiment and religious beliefsPasteur’s of the Experiment time. (1859) Experiment (1767) ScientificThe first serious attackWhere on the do idea the offlies spontaneous come generationWhat causes was microbesmade in 1668 to form by FrancescoWhere doRedi, microbes an come from QuestionItalian physician and from?poet. At Is that the time,rotting it meatwas widely in held decaying that maggots broth? arose spontaneouslythat cause in rotting broth tomeat. decay? Redi believed that maggotstransformed developed into thefrom flies? eggs laid by flies. To test his hypothesis, he set out meat in a Hypothesisvariety of flasks, someOnly open ______to the air, some can makesealed completely,Microorganisms and others formed covered not withIf gauze.cells can As arise he had from expected, maggots appearedflies and only rotting in the open flasks infrom which air the(spontaneously) flies could reach but the meat______and lay their substances, eggs. meat ______be from other microorganisms then they should appear transformed into flies. (other life). spontaneously in sterile broth. This was one of the first examples of an experiment in the modern sense, in which controls are used. In spite Experimentalof his well-executed experiment,He placed pieces the belief of meat in spontaneous Flasks generation 1 & 2 = heated remained flask strong, Straight-necked and even Redi flask = Designcontinued to believe itinto occurred 3 glass under jars. some circumstances.with broth The andinvention sealed ofwith the microscope______only servedgroup to enhance this belief. MicroscopyJar 1 = revealed a whole newmelted world glass of organisms that appeared to arise spontaneously. It was quickly learned that to create "animalcules," as the organisms were called, you needed only to place hay in waterJar 2 and= wait a few days beforeFlasks examining 3 & 4 your = heated new creationsflask underSwan-necked the microscope. flask = with broth and left open ______group The debate over spontaneousJar 3 = generation continued for centuries. In 1745, John Needham,He thenan English boiled the broth to kill clergyman, proposed what he considered the definitiveControl experiment. group =Everyone knew thatany boiling pre-existing killed organism, microorganisms, so heAll proposed of the jars to testwere whether exposed or not microorganisms appeared spontaneouslyallowed it after to cool, and set for boiling. He boiled chickento flies broth, in the put room. it into a flask, sealedExperimental it, and waited group -= sure enough,several microorganisms days. Datagrew. & Needham claimedJar 1victory = for spontaneous generation.Flask 1 = Straight-necked flask = Observations An Italian priest, Lazzaro Spallanzani, was not convinced,Flask 2and = he suggested that perhaps the microorganisms had enteredJar 2 = the broth from the air after the broth was boiled, but before it was sealed. To test his theory, he modified Needham's experiment - heFlask placed 3 = the chicken broth in a flask,Swan-necked sealed the flask flask, = drew off the air to create a partial vacuum, then boiled the broth. No microorganisms grew. Proponents of spontaneous generationJar argued 3 = that Spallanzani had onlyFlask proven 4 = that spontaneous generation could not Conclusion(s)occur without air. The boiled broth became What did the contaminated when experiment show? microorganisms from the The theory of spontaneous generation was finally laid to rest in 1859 by the young French chemist, Louis Was the ______entered the flask. Pasteur. The French Academy of Sciences sponsored a contest for the best experiment either proving or hypothesis His hypothesis was disproving spontaneous generation. Pasteur's winning experiment was a variation of the methods of supported? ______. His hypothesis was rejected. Needham and Spallanzani. He boiled meat broth in a flask, heated the neck of the flask in a flame until it became pliable, and bent it into the shape of an S. Air could enter the flask, but airborne microorganisms could not - they would settle by gravity in the neck. As Pasteur had expected, no microorganisms grew. When Pasteur tilted the flask so that the broth reached the lowest point in the neck, where any airborne particles would have settled, the broth rapidly became cloudy with life. Pasteur had both refuted the theory of spontaneous generation and convincingly demonstrated that microorganisms are everywhere - even in the air.