Ch. 16 The Origin of Life
Spontaneous Generation
Spontaneous Generation
• It was believed for many centuries that
life arose from nonliving matter.
– Flies arose from meat.
– Bees arose from carcasses of cattle.
– Mice arose from piles of grain.
– Beetles and wasps came from cow dung.
• Spontaneous generation – the
hypothesis that life arises from nonlife.
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Spontaneous Generation: True or False?
• Francesco Redi (1700’s) – An Italian
scientist who hypothesized that maggots (fly
larvae) arose from eggs not from the meat
itself.
Spontaneous Generation: True or False?
• Francesco Redi concluded that maggots did
not arise spontaneously. The maggots
developed from the eggs laid by flies.
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Spontaneous Generation: True or False?
• Lazzaro Spallanzani (1700’s) – An
Italian scientist who hypothesized that
life arose from life.
– Spallanzani was familiar with Redi’s work.
Spontaneous Generation:
True or False?
• Spallanzani concluded that
life cannot arise from
nonlife.
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Spontaneous Generation: True or False?
• Despite the work of both Redi and
Spallanzani people still believed in
spontaneous generation.
• They argued that air was necessary for
spontaneous generation and
Spallanzani kept the air out by sealing
his flask.
Pasteur and Spontaneous Generation
• Louis Pasteur (1864) – A French
scientist who finally disproved the
hypothesis of spontaneous generation.
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Pasteur and Spontaneous Generation
• Pasteur conducted an
experiment which
allowed air into the
flask but not dust or
airborne particles.
• Microorganisms did not
form in the nutrient
broth.
Pasteur and Spontaneous Generation
• After one year, Pasteur
broke off the neck of
the flask. After one day
microorganisms began
to grow in the flask.
• Pasteur concluded that
microorganisms
entered the flask from
the air. Therefore, life
only come from life.
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