1. INTRO TO EVOLUTION

2. FIRST IDEAS In early times, people believed in spontaneous generation. Spontaneous generation is the belief that something living came from something nonliving. It is also called abiogenesis

3. Spontaneous Generation For example, the early Egyptians believed frogs came from mud. Every year the Nile river flooded and when the waters receded, there were millions of frogs.

4. Spontaneous Generation

5. In Medieval times, farmers believed rats came from molded grain. They stored the grain in large sheds and then began noticing rats appearing. The English believed that rats came directly from garbage.

7. Spontaneous Generation People believed that maggots came from meat that was left out and the maggots became flies.

8. MAGGOTS

9. Spontaneous Generation Aristotle was the first person to develop the idea of spontaneous generation, and the idea lasted more than 2000 years. People based their beliefs on observation versus experimentation.

10. Francesco Redi Early scientist who conducted experiments to try to disprove spontaneous generation First scientist to ever conduct a controlled experiment

11. Redi’s Experiment Redi believed that flies came from other living things, not meat. He conducted an experiment by placing raw meat in several jars. Some of the jars were completely sealed, some were covered with gauze, and some were left open.

12. Observations He noticed: o Only the jars that were left open and had flies enter had maggots on the meat. o The jars covered with gauze had flies and maggots on the gauze but not the meat. o Jars that were left closed never got maggots. He kept the maggots until they turned into flies. This disproved the idea of spontaneous generation and led to the idea that living organisms must come from other living organisms.

13. Redi’s Experiment

14. Biogenesis Biogenesis – Living organisms come from other living organisms Even though people now believed larger organisms came from other living things, the idea of spontaneous generation was still debated, especially for microscopic organisms

15. John Needham John Needham – believed spontaneous generation occurred with microorganisms. He conducted an experiment where he heated chicken broth to kill any existing microorganisms. Then he let the broth sit out and cool. After some time, the broth became cloudy with new microorganisms.

16. Conclusion Soooo……. Needham believed this proved his hypothesis was correct and that the microorganisms came from the broth

17. Lazarro Spallanzani Lazzaro Spallanzani – He did not believe in spontaneous generation and repeated Needham’s experiment. Instead of leaving the chicken broth container open, though, he sealed it. No microorganisms grew. He believed this proved his hypothesis that the microorganisms came from the air, not the broth. He “destroyed the life source”.

18. Spallanzani It did not convince many people though because they believed that air was required for spontaneous generation to occur. All he proved was that S G could not occur without air.

20. Spontaneous Generation – BUSTED! 100 years after Spallazani’s experiment, Louis Pasteur designed an experiment that proved once and for all that living things had to come from other living things.

21. Louis Pasteur Pasteur believed that microbes were carried on dust particles in the air and not by some “life force” in the air. He repeated the experiment of Spallanzani but with specially designed flasks.

22. Pasteur’s Experiment His flask had a swan-like neck. He heated the broth to sterilize it. The neck of the flask allowed air in but trapped any microorganisms so they could not reach the broth. The broth sat for years without ever becoming unsterile (no microorganisms grew)

23. Findings Once the flask was tipped to allow what was trapped in the neck to touch the broth, microorganisms grew very quickly This proved that microorganisms live in the air but are not formed from air.

25. Father of Microbiology and Immunology Pasteur became known as the Father of Microbiology and Immunology. First to determine that yeast is responsible for fermentation (beer, wine) Developed the germ theory – diseases are caused by microorganisms Vaccines for rabies and anthrax

26. Milk Pasteurization Pasteurization – process of heating milk to kill harmful bacteria This is still used during milk processing for human consumption. His discoveries in microbiology led to antiseptic techniques still used by doctors and nurses today to prevent the spreading of diseases.

27. Pasteurization Process

28. Law of Biogenesis Scientific law stating that living organisms only come from other living organisms. Firmly established and widely- accepted General fact of nature

29. Now What? After proving life came from life, people began theorizing as to how life began. Where did the first living things come from? WE CANNOT PROVE ANYTHING! WE CAN ONLY USE THE SCIENTIFIC METHOD TO THEORIZE HOW LIFE BEGAN ON EARTH.

30. Review Spontaneous generation is the belief that something living came from something nonliving. Francesco Redi was one of the first scientists to disprove spontaneous generation by showing that flies come from other flies and are not created from meat. John Needham believed he proved spontaneous generation occurs for microorganisms because he didn’t realize that microorganisms could be found in the air. Lazzaro Spallanzini believed disproved spontaneous generation by designing an experiment that kept heated broth from being re-contaminated by air. Louis Pasteur finally disproved spontaneous generation by designing an experiment that confirmed that microorganisms can be found in the air. Biogenesis a scientific law that states that living organisms only come from other living organisms.