In the 1600’s people did not understand how special living matter was. They thought that life could spring from nonliving matter. They believed in the theory of spontaneous generations. People believed that mice came from straw and that frogs and turtles came from rotting wood and mud at the bottom of the pond. What made them believe this?
In 1668, an Italian doctor named Francesco Redi disproved the theory of spontaneous generation. What type of experiment do you think he used?
In the 1600’s, maggots (a wormlike stage in the life cycle of a fly) often appeared on rotting meat. People believed that rotten meat had turned into maggots. This could only mean that flies (adult maggots) formed from dead animals (meat) – or that non-living things could give rise to living things. After his experiments it was proved that maggots hatched from eggs laid by flies.
Meat sealed in air tight container
Meat exposed to the outside environment
Meat covered with cheese cloth
Draw what you think happened
Draw what actually happened
More evidence was presented to disprove spontaneous generation in the mid nineteenth century. The French scientist Louis Pasteur, conducted an experiment with microorganisms. The results of this experiment showed that even microorganisms do not reproduce by spontaneous generation.
Pasteur poured broth into swan-necked flasks, similar to those shown below. The broth was made up of water, air, and nutrients. Pasteur reasoned that the bent necks of the flasks would keep microorganisms from entering.
Pasteur boiled the broth in some of the flasks. In these flasks, the broth did not spoil. However, the broth that was not boiled showed signs of spoiling, or the presence of microorganisms.
What effect do you think boiling has on the growth of microorganisms?
Why did Loius Pasteur use a swan neck flask?