1. Early Scientists

2. ARISTOTLE Greek philosopher Made observations of the natural world through reasoning. Special “vital” forces brought some living things into being, from nonliving material- “spontaneous generation.”

3. FRANCESCO REDI Italian physician Proposed that flies laid eggs on meat  this produced maggots, not spontaneous generation. BIOGENESIS (life comes from life) Experiment: covered jars of meat vs. uncovered jars of meat. Results supported his hypothesis: maggots came from flies.

4. ANTON van LEEUWENHOEK From the Netherlands Used lenses (microscope) to magnify tiny objects. “Animalcules”- tiny animals Discovered microscopic life in pond water.

5. JOHN NEEDHAM English scientist Tried to prove spontaneous generation. Sealed a bottle of gravy, then heated it (to kill any life). Found life several days later, which he claimed came from the gravy. Flaw with his experiment: the flask was not sealed and was exposed to the air.

6. LAZZARO SPALLANZANI Italian scholar Improved upon Needham’s experiment. Boiled flasks of gravy to kill life, sealed one jar, left other jar open. Open jar had living microorganisms, sealed jar did not. Concluded that gravy did not produce life, organisms entered through the air.

7. LOUIS PASTEUR French scientist Designed a flask that had a long curved neck  open to air, but microorganisms could not travel through neck to the flask. Broth remained free of life. Once neck of flask was broken, broth filled with microorganisms. Showed living things came from living things; spontaneous generation was incorrect.