The Origin of Life Ch 14 Sec 2

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The Origin of Life Ch. 14, Sec. 2

The Origin of Life Ch. 14, Sec. 2

Spontaneous Generation • Pre-17 th century it was believed that living things arose from

Spontaneous Generation • Pre-17 th century it was believed that living things arose from nonliving things through a process called Spontaneous Generation

 • 6 th century BC: Greek philosophers propose life arose when sunlight was

• 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 • Why?

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

Francesco Redi (1626 -1697) • Mid-17 th century people believed flies were spontaneously generated

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

• 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

• 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

Louis Pasteur (1822 -1895) • Finally disproved spontaneous generation once and for all! 200

Louis Pasteur (1822 -1895) • Finally disproved spontaneous generation once and for all! 200 years after Redi’s experiment • Pasteur set up an experiment where boiled broth was exposed to air, but microorganisms couldn’t fall in

 • By the 1800’s scientists understood (thanks to the microscope invented a century

• By the 1800’s scientists understood (thanks to the microscope invented a century ago) that microorganisms (bacteria & viruses) caused people to get sick • But….

 • Some scientists still believed that bacteria and viruses spontaneously generated from the

• Some scientists still believed that bacteria and viruses spontaneously generated from the air • Pasteur proved them wrong with his experiment

 • Boiled broth was exposed to air in a specially shaped flask over

• Boiled broth was exposed to air in a specially shaped flask 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!!!

 • Thanks to Pasteur…. • Biogenesis = living organisms come from other living

• Thanks to Pasteur…. • Biogenesis = living organisms come from other living organisms