HISTORY OF LIFE Chapter 14 Spontaneous Generation Before

HISTORY OF LIFE (Chapter 14)

Spontaneous Generation Before the 17 th century it was believed that living things arise from nonliving things through a process called Spontaneous Generation

6 th century BC: Greek philosophers propose life arose when sunlight was shined onto mud Why?

1600’s: It was believed that mice appeared from rotten grain

Francesco Redi (1626 -1697) Mid-17 th century people believed flies were spontaneously generated from rotting meat Redi was a scientist who noticed a life stage to the flies on the rotten meat – 1. Maggots – 2. Pupa – 3. Flies He observed that the maggots appeared where flies had landed first

Redi predicted that if the meat could be kept away from the flies, then there would be no maggots on the meat He did not believe that flies spontaneously generated from meat!!! So he set up his experiment…

Control Group = uncovered jar of meat, flies layed eggs, which hatched into maggots, which turned into more flies Experimental Group = covered jars of meat, flies have no chance to lay eggs, new flies do not appear

Lazzaro Spallanzani (17291799) Experimented around the time the microscope was created Microscope allowed scientists to view microorganisms for the first time

People believed microorganisms that made you sick (what we now know as bacteria & viruses) spontaneously generated in the air Air held “vital force” that could generate life

Spallanzani’s experiment = he knew microorganisms grew easily in food (ex: broth), he also knew that boiling the broth would kill the microorganisms

Growth occurred in boiled broth only when the flask was uncorked & exposed to air Exposure to air allows microorganisms to fall in and land in the broth to grow But many people still believed in spontaneous generation!!! Boiling destroyed the “vital force”

Louis Pasteur (1822 -1895) Continued with Spallanzani’s experiments to finally disprove spontaneous generation Pasteur set up an experiment where boiled broth was exposed to air, but microorganisms couldn’t fall in

Boiled broth was exposed to air over a period of time but nothing grew Once the neck was broken off bacteria grew in the broth Bacteria did not spontaneously grow from the air!!!