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Development of the Cell Theory

Development of the Cell Theory. Abiogenesis Vs Biogenesis. Abiogenesis. Theory states that non-living things can be spontaneously changed into living things. Also referred to as the theory of spontaneous generation . Developed by Aristotle the ancient Greek philosopher. Francesco Redi.

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Development of the Cell Theory

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  1. Development of the Cell Theory Abiogenesis Vs Biogenesis

  2. Abiogenesis • Theory states that non-living things can be spontaneously changed into living things. • Also referred to as the theory of spontaneous generation. • Developed by Aristotle the ancient Greek philosopher.

  3. Francesco Redi • An Italian doctor tried to disprove this theory of abiogenesis. • Left 4 jars of rotting meat open to the air, after a while found maggots on the meat and flies hovering in the air.

  4. Redi repeated the same thing again but covered 2 of the jars with a lid. Result, No maggots on the meat that was covered. Concluded that flies came from flies not rotting meat, disproving Aristotle’s theory of Abiogenesis. Right?

  5. Hold On ! • The supporters of Abiogenesis said the covered jars were different from the controlled jars, no fresh air circulated around the meat. They claimed that the air was the “Active Ingredient” that caused spontaneous generation”

  6. Redi’s Final Try • He put a fine mesh wire over the jars so air could circulate, result NO maggots. Proved rotting meat can’t be changed into flies. • However, critics said that the mesh was too fine to let this “Active Ingredient” into the jars. So abiogenesis was NOT yet disproved!

  7. John Needham • The meat broth was teaming with microbes that made it look cloudy. • He heated it for a short time until the meat broth was clear.

  8. After a few days, microbes were present. He concluded that microbes came from non-living things thus supporting Abiogenesis. • Two big problems, he used a cork seal to allow air to circulate but it allowed microbes to enter. Secondly, he heated the broth for a short time and didn’t destroy all the microbes. POOR SCIENCE !

  9. Lazzaro Spallanzani • He performed Needham’s experiment but melted the glass at the top of the flask to seal it and then heated it for a long time.

  10. The result showed no microbes present. • However, critics claimed once again that the “Active Ingredient” in the air was not allowed to enter the flask. So Abiogenesis was not yet disproved!

  11. Louis Pasteur • Pasteur heated an open flask containing microbe filled meat broth for a long time killing all the microbes.

  12. He then let it sit for a few days and it was teaming with microbes. • He hypothesized that the microbes must have entered from the air.

  13. Abiogenesis is Dead! • Pasteur developed a special swan-necked flask designed to trap the microbes from the air but still let the “Active Ingredient” enter the flask. • The result of this second experiment showed no microbes in the broth thus disproving Abiogenesis and proving Biogenesis which states that only life can produce life!

  14. The Cell Theory 1.All living things are composed of cells. 2.Cells are the basic units of structure and function for all living things. 3.New cells are produced from pre-existing cells.

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