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Biogenesis vs. Abiogenesis

Biogenesis vs. Abiogenesis. Biology 11. “The secret to reaching my goals lies solely in my tenacity” -Louis Pasteur. Abiogenesis vs. Biogenesis. Introduction: Biology as a Science progressed by observation. The hypotheses proposed by early scientists were rarely tested by experiments.

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Biogenesis vs. Abiogenesis

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  1. Biogenesis vs. Abiogenesis Biology 11

  2. “The secret to reaching my goals lies solely in my tenacity” -Louis Pasteur

  3. Abiogenesis vs. Biogenesis Introduction: • Biology as a Science progressed by observation. • The hypotheses proposed by early scientists were rarely tested by experiments.

  4. Abiogenesis continued… Example: • Pond dries up – no fish or frogs • Rain comes – fish and frogs Therefore: It rained fish and frogs

  5. Abiogenesis continued… Theory of Abiogenesis (aka spontaneous generation) • Nonliving things can be transformed into living things. • Proposed by Aristotle who observed rotting meat and flies. • Existed for nearly 2000 years

  6. Van Helmont continued… • ~300 years ago Belgian doctor Jean van Helmont – concluded that mice could be created from a dirty shirt. • He placed grains of wheat and a dirty shirt in a container and in 21 days mice appeared. • Conclusion: Sweat caused wheat to ferment into mice. Abiogenesis!

  7. Redi • In 1668 Francesco Redi (Italian physician) tested Aristotle’s hypothesis (meat  flies)

  8. Redi continued… • 4 sets of jars with meat (snake, eel, fish, veal) one set was open (experimental group) one set was sealed (control group) • Maggots appeared on open jars of meat • Conclusion: Flies come from flies! Biogenesis – life from life.

  9. Redi continued… • Bad news  lots of critics • No air in jar, therefore life could not survive. • Redi repeated his experiment with a fine mesh wire – supported Biogenesis again! • Critics still objected…

  10. Needham • John Needham (1713 – 1781) English botanist • Reexamined theory of Abiogenesis • Observed meat broth left unsealed soon changed colour (evidence of microorganisms).

  11. Needham continued… Experiment: • Boiled flasks of meat broth to kill microorganisms • Left the flasks (unsealed) • Flasks soon become murky and full of microbes

  12. Needham continued… Conclusion: • Abiogenesis AHHHHHHHHH!!! • Sent many Scientists down the wrong path.

  13. Lazzaro Spallanzani (1729-1799) • 25 years later Spallanzani repeated experiment more carefully • Boiled flasks longer and sealed flasks • Critics again objected to sealed flasks!

  14. The Final Blow! Louis Pasteur (1822-1895) • 1864 – Pasteur developed a swan-neck flask

  15. Pasteur continued… Experiment: • Boiled broth, air could enter but microbes were trapped in curved flask • Broth remained clear  Biogenesis finally proven!

  16. The End! Now here is your assignment: List and explain three “flaws” in experimental design that you have heard about during this presentation.

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