describe spallanzani experiment

3.1 Spontaneous Generation

Learning objectives.

By the end of this section, you will be able to:

Explain the theory of spontaneous generation and why people once accepted it as an explanation for the existence of certain types of organisms
Explain how certain individuals (van Helmont, Redi, Needham, Spallanzani, and Pasteur) tried to prove or disprove spontaneous generation

Clinical Focus

Barbara is a 19-year-old college student living in the dormitory. In January, she came down with a sore throat, headache, mild fever, chills, and a violent but unproductive (i.e., no mucus) cough. To treat these symptoms, Barbara began taking an over-the-counter cold medication, which did not seem to work. In fact, over the next few days, while some of Barbara’s symptoms began to resolve, her cough and fever persisted, and she felt very tired and weak.

What types of respiratory disease may be responsible?

Jump to the next Clinical Focus box

Humans have been asking for millennia: Where does new life come from? Religion, philosophy, and science have all wrestled with this question. One of the oldest explanations was the theory of spontaneous generation, which can be traced back to the ancient Greeks and was widely accepted through the Middle Ages.

The Theory of Spontaneous Generation

The Greek philosopher Aristotle (384–322 BC) was one of the earliest recorded scholars to articulate the theory of spontaneous generation , the notion that life can arise from nonliving matter. Aristotle proposed that life arose from nonliving material if the material contained pneuma (“spirit” or “breath”). As evidence, he noted several instances of the appearance of animals from environments previously devoid of such animals, such as the seemingly sudden appearance of fish in a new puddle of water. 1

This theory persisted into the 17th century, when scientists undertook additional experimentation to support or disprove it. By this time, the proponents of the theory cited how frogs simply seem to appear along the muddy banks of the Nile River in Egypt during the annual flooding. Others observed that mice simply appeared among grain stored in barns with thatched roofs. When the roof leaked and the grain molded, mice appeared. Jan Baptista van Helmont , a 17th century Flemish scientist, proposed that mice could arise from rags and wheat kernels left in an open container for 3 weeks. In reality, such habitats provided ideal food sources and shelter for mouse populations to flourish.

However, one of van Helmont’s contemporaries, Italian physician Francesco Redi (1626–1697), performed an experiment in 1668 that was one of the first to refute the idea that maggots (the larvae of flies) spontaneously generate on meat left out in the open air. He predicted that preventing flies from having direct contact with the meat would also prevent the appearance of maggots. Redi left meat in each of six containers ( Figure 3.2 ). Two were open to the air, two were covered with gauze, and two were tightly sealed. His hypothesis was supported when maggots developed in the uncovered jars, but no maggots appeared in either the gauze-covered or the tightly sealed jars. He concluded that maggots could only form when flies were allowed to lay eggs in the meat, and that the maggots were the offspring of flies, not the product of spontaneous generation.

In 1745, John Needham (1713–1781) published a report of his own experiments, in which he briefly boiled broth infused with plant or animal matter, hoping to kill all preexisting microbes. 2 He then sealed the flasks. After a few days, Needham observed that the broth had become cloudy and a single drop contained numerous microscopic creatures. He argued that the new microbes must have arisen spontaneously. In reality, however, he likely did not boil the broth enough to kill all preexisting microbes.

Lazzaro Spallanzani (1729–1799) did not agree with Needham’s conclusions, however, and performed hundreds of carefully executed experiments using heated broth. 3 As in Needham’s experiment, broth in sealed jars and unsealed jars was infused with plant and animal matter. Spallanzani’s results contradicted the findings of Needham: Heated but sealed flasks remained clear, without any signs of spontaneous growth, unless the flasks were subsequently opened to the air. This suggested that microbes were introduced into these flasks from the air. In response to Spallanzani’s findings, Needham argued that life originates from a “life force” that was destroyed during Spallanzani’s extended boiling. Any subsequent sealing of the flasks then prevented new life force from entering and causing spontaneous generation ( Figure 3.3 ).

Check Your Understanding

Describe the theory of spontaneous generation and some of the arguments used to support it.
Explain how the experiments of Redi and Spallanzani challenged the theory of spontaneous generation.

Disproving Spontaneous Generation

The debate over spontaneous generation continued well into the 19th century, with scientists serving as proponents of both sides. To settle the debate, the Paris Academy of Sciences offered a prize for resolution of the problem. Louis Pasteur , a prominent French chemist who had been studying microbial fermentation and the causes of wine spoilage, accepted the challenge. In 1858, Pasteur filtered air through a gun-cotton filter and, upon microscopic examination of the cotton, found it full of microorganisms, suggesting that the exposure of a broth to air was not introducing a “life force” to the broth but rather airborne microorganisms.

Later, Pasteur made a series of flasks with long, twisted necks (“swan-neck” flasks), in which he boiled broth to sterilize it ( Figure 3.4 ). His design allowed air inside the flasks to be exchanged with air from the outside, but prevented the introduction of any airborne microorganisms, which would get caught in the twists and bends of the flasks’ necks. If a life force besides the airborne microorganisms were responsible for microbial growth within the sterilized flasks, it would have access to the broth, whereas the microorganisms would not. He correctly predicted that sterilized broth in his swan-neck flasks would remain sterile as long as the swan necks remained intact. However, should the necks be broken, microorganisms would be introduced, contaminating the flasks and allowing microbial growth within the broth.

Pasteur’s set of experiments irrefutably disproved the theory of spontaneous generation and earned him the prestigious Alhumbert Prize from the Paris Academy of Sciences in 1862. In a subsequent lecture in 1864, Pasteur articulated “ Omne vivum ex vivo ” (“Life only comes from life”). In this lecture, Pasteur recounted his famous swan-neck flask experiment, stating that “…life is a germ and a germ is life. Never will the doctrine of spontaneous generation recover from the mortal blow of this simple experiment.” 4 To Pasteur’s credit, it never has.

How did Pasteur’s experimental design allow air, but not microbes, to enter, and why was this important?
What was the control group in Pasteur’s experiment and what did it show?
1 K. Zwier. “Aristotle on Spontaneous Generation.” http://www.sju.edu/int/academics/cas/resources/gppc/pdf/Karen%20R.%20Zwier.pdf
2 E. Capanna. “Lazzaro Spallanzani: At the Roots of Modern Biology.” Journal of Experimental Zoology 285 no. 3 (1999):178–196.
3 R. Mancini, M. Nigro, G. Ippolito. “Lazzaro Spallanzani and His Refutation of the Theory of Spontaneous Generation.” Le Infezioni in Medicina 15 no. 3 (2007):199–206.
4 R. Vallery-Radot. The Life of Pasteur , trans. R.L. Devonshire. New York: McClure, Phillips and Co, 1902, 1:142.

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2.1 Spontaneous Generation

Learning objectives.

Explain the theory of spontaneous generation and why people once accepted it as an explanation for the existence of certain types of organisms
Explain how certain individuals (van Helmont, Redi, Needham, Spallanzani, and Pasteur) tried to prove or disprove spontaneous generation

The Theory of Spontaneous Generation

The Greek philosopher Aristotle (384–322 BC) was one of the earliest recorded scholars to articulate the theory of spontaneous generation , the notion that life can arise from nonliving matter. Aristotle proposed that life arose from nonliving material if the material contained pneuma (“vital heat”). As evidence, he noted several instances of the appearance of animals from environments previously devoid of such animals, such as the seemingly sudden appearance of fish in a new puddle of water. [1]

This theory persisted into the 17th century, when scientists undertook additional experimentation to support or disprove it. By this time, the proponents of the theory cited how frogs simply seem to appear along the muddy banks of the Nile River in Egypt during the annual flooding. Others observed that mice simply appeared among grain stored in barns with thatched roofs. When the roof leaked and the grain molded, mice appeared. Jan Baptista van Helmont, a 17th century Flemish scientist, proposed that mice could arise from rags and wheat kernels left in an open container for 3 weeks. In reality, such habitats provided ideal food sources and shelter for mouse populations to flourish.

However, one of van Helmont’s contemporaries, Italian physician Francesco Redi (1626–1697), performed an experiment in 1668 that was one of the first to refute the idea that maggots (the larvae of flies) spontaneously generate on meat left out in the open air. He predicted that preventing flies from having direct contact with the meat would also prevent the appearance of maggots. Redi left meat in each of six containers ( Figure 2 .2 ). Two were open to the air, two were covered with gauze, and two were tightly sealed. His hypothesis was supported when maggots developed in the uncovered jars, but no maggots appeared in either the gauze-covered or the tightly sealed jars. He concluded that maggots could only form when flies were allowed to lay eggs in the meat, and that the maggots were the offspring of flies, not the product of spontaneous generation.

Francesco Redi’s experimental setup consisted of an open container, a container sealed with a cork top, and a container covered in mesh that let in air but not flies. Maggots only appeared on the meat in the open container. However, maggots were also found on the gauze of the gauze-covered container.

In 1745, John Needham (1713–1781) published a report of his own experiments, in which he briefly boiled broth infused with plant or animal matter, hoping to kill all preexisting microbes. [2] He then sealed the flasks. After a few days, Needham observed that the broth had become cloudy and a single drop contained numerous microscopic creatures. He argued that the new microbes must have arisen spontaneously. In reality, however, he likely did not boil the broth enough to kill all preexisting microbes.

Lazzaro Spallanzani (1729–1799) did not agree with Needham’s conclusions, however, and performed hundreds of carefully executed experiments using heated broth. [3] As in Needham’s experiment, broth in sealed jars and unsealed jars was infused with plant and animal matter. Spallanzani’s results contradicted the findings of Needham: Heated but sealed flasks remained clear, without any signs of spontaneous growth, unless the flasks were subsequently opened to the air. This suggested that microbes were introduced into these flasks from the air. In response to Spallanzani’s findings, Needham argued that life originates from a “life force” that was destroyed during Spallanzani’s extended boiling. Any subsequent sealing of the flasks then prevented new life force from entering and causing spontaneous generation ( Figure 2 .3 ).

(a) Francesco Redi, who demonstrated that maggots were the offspring of flies, not products of spontaneous generation. (b) John Needham, who argued that microbes arose spontaneously in broth from a “life force.” (c) Lazzaro Spallanzani, whose experiments with broth aimed to disprove those of Needham.

Describe the theory of spontaneous generation and some of the arguments used to support it.
Explain how the experiments of Redi and Spallanzani challenged the theory of spontaneous generation.

Disproving Spontaneous Generation

The debate over spontaneous generation continued well into the 19th century, with scientists serving as proponents of both sides. To settle the debate, the Paris Academy of Sciences offered a prize for resolution of the problem. Louis Pasteur, a prominent French chemist who had been studying microbial fermentation and the causes of wine spoilage, accepted the challenge. In 1858, Pasteur filtered air through a gun-cotton filter and, upon microscopic examination of the cotton, found it full of microorganisms, suggesting that the exposure of a broth to air was not introducing a “life force” to the broth but rather airborne microorganisms.

Later, Pasteur made a series of flasks with long, twisted necks (“swan-neck” flasks), in which he boiled broth to sterilize it ( Figure 2 .4 ). His design allowed air inside the flasks to be exchanged with air from the outside, but prevented the introduction of any airborne microorganisms, which would get caught in the twists and bends of the flasks’ necks. If a life force besides the airborne microorganisms were responsible for microbial growth within the sterilized flasks, it would have access to the broth, whereas the microorganisms would not. He correctly predicted that sterilized broth in his swan-neck flasks would remain sterile as long as the swan necks remained intact. However, should the necks be broken, microorganisms would be introduced, contaminating the flasks and allowing microbial growth within the broth.

Pasteur’s set of experiments irrefutably disproved the theory of spontaneous generation and earned him the prestigious Alhumbert Prize from the Paris Academy of Sciences in 1862. In a subsequent lecture in 1864, Pasteur articulated “ Omne vivum ex vivo ” (“Life only comes from life”). In this lecture, Pasteur recounted his famous swan- neck flask experiment, stating that “…life is a germ and a germ is life. Never will the doctrine of spontaneous generation recover from the mortal blow of this simple experiment.” [4] To Pasteur’s credit, it never has.

(a) French scientist Louis Pasteur, who definitively refuted the long-disputed theory of spontaneous generation. (b) The unique swan-neck feature of the flasks used in Pasteur ’s experiment allowed air to enter the flask but prevented the entry of bacterial and fungal spores. (c) Pasteur’s experiment consisted of two parts. In the first part, the broth in the flask was boiled to sterilize it. When this broth was cooled, it remained free of contamination. In the second part of the experiment, the flask was boiled and then the neck was broken off. The broth in this flask became contaminated.

How did Pasteur’s experimental design allow air, but not microbes, to enter, and why was this important?
What was the control group in Pasteur’s experiment and what did it show?
K. Zwier. “Aristotle on Spontaneous Generation.” http://www.sju.edu/int/academics/cas/resources/gppc/pdf/Karen%20R.%20Zwier.pdf ↵
E. Capanna. “Lazzaro Spallanzani: At the Roots of Modern Biology.” Journal of Experimental Zoology 285 no. 3 (1999):178–196. ↵
R. Mancini, M. Nigro, G. Ippolito. “Lazzaro Spallanzani and His Refutation of the Theory of Spontaneous Generation.” Le Infezioni in Medicina 15 no. 3 (2007):199–206. ↵
R. Vallery-Radot. The Life of Pasteur, trans. R.L. Devonshire. New York: McClure, Phillips and Co, 1902, 1:142. ↵

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Spontaneous Generation – Definition, Experiments, Importance

World of neuroscience, the weird and wonderful, pioneers in microbiology, what is spontaneous generation theory.

Definition of Spontaneous Generation

Spontaneous generation theory.

The spontaneous generation theory, as delineated by Aristotle in his seminal work “On the Generation of Animals” circa 350 B.C., offers a scientific proposition to elucidate the seemingly abrupt appearance of organisms, such as flies, rats, and maggots, within decomposing substances. This theory posits that these organisms are not progeny of pre-existing organisms or parent entities. Instead, their emergence is contingent upon specific environmental conditions conducive to their creation.

Aristotle elucidated his stance on spontaneous generation with the following declaration:

Experiments on Spontaneous Generation Theory

The Greek philosopher Aristotle(384–322 BC) supports the spontaneous generation theory. He thought that life was originated from nonliving materials if the material contained pneuma (“vital heat”).

Redi’s Experiment

From this experiment, Redi proved that maggots came from the fly eggs means spontaneous generation theory was wrong. Because according to this theory living cells were originated from the nonliving cells.

John Needham’s Experiment

Spallanzani’s experiment, pasteur’s experiment, john tyndall, biogenesis definition, the disproving of spontaneous generation theory.

2. John Needham (1731-1781) A century later, John Needham, an English naturalist and supporter of spontaneous generation, boiled a broth and poured it into a covered flask. At that time, it was known that boiling could kill “animacules” or microorganisms. However, after some time, the broth was teeming with microorganisms. Needham believed this supported spontaneous generation. Critics argued that he hadn’t boiled the broth long enough, suggesting that the animacules were heat-resistant.

In conclusion, the theory of spontaneous generation was debunked through a series of meticulous experiments by various scientists over the centuries. Their collective efforts paved the way for the modern understanding of the origins of life and the role of microorganisms in our environment.

Examples of Spontaneous Generation

3. Scorpion Creation via Basil and Bricks : Jean Baptiste van Helmont, a renowned European chemist, posited a unique method for producing scorpions. He instructed individuals to chisel a cavity into a brick, fill it with basil, and then cover it with another brick. After exposing this setup to sunlight for several days, he claimed that “the basil’s fumes, acting as a fermenting agent, would metamorphose the plant matter into genuine scorpions.”

Spontaneous generation vs. Modern abiogenesis

However, this ancient understanding of abiogenesis is vastly different from the modern hypothesis of abiogenesis.

Spontaneous generation vs. Biogenesis

Throughout history, the origin of life has been a topic of great intrigue and debate. Two primary theories emerged: spontaneous generation and biogenesis.

Huxley’s definitions gained widespread acceptance and became the standard understanding of the terms. Thus, while spontaneous generation or abiogenesis suggests life can emerge from non-life, biogenesis firmly states that life can only come from life.

Equivocal vs. Univocal generation

What did the Spontaneous Generation Theory propose? a) Life can arise from living organisms. b) Life can arise spontaneously from non-living matter. c) Life can only arise from similar life forms. d) Life can arise from water.

Who conducted an experiment with meat in jars to challenge the Spontaneous Generation Theory? a) Louis Pasteur b) John Needham c) Lazzaro Spallanzani d) Francesco Redi

Which term is synonymous with Spontaneous Generation? a) Biogenesis b) Abiogenesis c) Equivocal generation d) Univocal generation

Who proposed the term “abiogenesis” to describe the process of spontaneous generation? a) Henry Charlton Bastian b) Thomas Henry Huxley c) Lazzaro Spallanzani d) John Needham

Which theory opposes the idea of Spontaneous Generation? a) Equivocal generation b) Xenogenesis c) Biogenesis d) Heterogenesis

Which scientist designed flasks with S-shaped necks to disprove Spontaneous Generation? a) Francesco Redi b) John Needham c) Lazzaro Spallanzani d) Louis Pasteur

What did people historically believe could spontaneously generate from stored grain? a) Flies b) Maggots c) Mice d) Worms

Which term refers to the process where a species is produced from unrelated species? a) Biogenesis b) Univocal generation c) Equivocal generation d) Abiogenesis

Who believed that “vital heat” in the air was necessary for spontaneous generation? a) Francesco Redi b) John Needham c) Lazzaro Spallanzani d) Louis Pasteur

Which of the following is NOT a synonym for Spontaneous Generation? a) Abiogenesis b) Heterogenesis c) Xenogenesis d) Biogenesis

1. What is spontaneous generation and who disproved the theory?

The Spontaneous generation theory was referred to as the living cells were originated from nonliving cells. According to this theory, mice came from corn, flies from bovine manure, maggots from rotting meat, and fish from the mud of previously dry lakes.

2. Are abiogenesis and spontaneous generation the same?

3. who proposed the theory of spontaneous generation.

Spontaneous generation theory was first proposed by Aristotle (384–322 BC).

4. What is meant by the idea of spontaneous generation?

5. what is an example of a spontaneous generation, 6. does spontaneous generation occur.

Yes, spontaneous generation occurs. Then write Redi’s Experiment

7. Is spontaneous generation true?

8. why was spontaneous generation believed for so long, 9. does meat spontaneously generate flies and maggots.

No. Follow Redi’s Experiment

10. Who disproved spontaneous generation?

11. how long was spontaneous generation believed true, 12. why was the theory of spontaneous generation rejected.

Follow John Needham’s Experiment and last point of Spallanzani’s Experiment.

13. What is spontaneous generation history?

14. is spontaneous generation correct or incorrect, 15. can living matter come from nonliving matter, 16. what was the variable in redi’s experiment, 17. what was redi’s initial observation, 18. did louis pasteur believe spontaneous generation, 19. what did redi conclude, 20. did john needham believe in spontaneous generation, 21. did lazzaro spallanzani believe spontaneous generation, 22. what is the swan neck flask experiment, 23. what was lazzaro spallanzani experiment, 24. when did lazzaro spallanzani do his experiment, 25. what was francesco redi’s hypothesis about the appearance of maggots, related biology study notes, sterilization – physical and chemical methods, physical methods of sterilization, archaea – habitat, structure, characteristics, importance, examples, a- z microbiology terms with definitions – microbiology glossary, history of microbiology , history, branches, and career opportunities of microbiology, biosafety levels with their primary and secondary barriers., biosafety guidelines – biosafety guidelines and regulations, latest questions, leave a comment cancel reply.

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3. The Cell

3.1 Spontaneous Generation

Learning objectives.

Explain the theory of spontaneous generation and why people once accepted it as an explanation for the existence of certain types of organisms
Explain how certain individuals (van Helmont, Redi, Needham, Spallanzani, and Pasteur) tried to prove or disprove spontaneous generation

CLINICAL FOCUS: Part 1

What types of respiratory disease may be responsible?

Jump to the next Clinical Focus box

The Theory of Spontaneous Generation

The Greek philosopher Aristotle (384–322 BC) was one of the earliest recorded scholars to articulate the theory of spontaneous generation, the notion that life can arise from nonliving matter. Aristotle proposed that life arose from nonliving material if the material contained pneuma (“vital heat”). As evidence, he noted several instances of the appearance of animals from environments previously devoid of such animals, such as the seemingly sudden appearance of fish in a new puddle of water. [1]

This theory persisted into the 17th century, when scientists undertook additional experimentation to support or disprove it. By this time, the proponents of the theory cited how frogs simply seem to appear along the muddy banks of the Nile River in Egypt during the annual flooding. Others observed that mice simply appeared among grain stored in barns with thatched roofs. When the roof leaked and the grain moulded, mice appeared. Jan Baptista van Helmont , a 17th century Flemish scientist, proposed that mice could arise from rags and wheat kernels left in an open container for 3 weeks. In reality, such habitats provided ideal food sources and shelter for mouse populations to flourish.

An open container with meat has flies and the formation of maggots in meat. A cork-sealed container of meat has no flies and no formation of maggots in meat. A gauze covered container of meat has flies and maggots on the surface of the gauze but no maggots in the meat.

In 1745, John Needham (1713–1781) published a report of his own experiments, in which he briefly boiled broth infused with plant or animal matter, hoping to kill all preexisting microbes. [2] He then sealed the flasks. After a few days, Needham observed that the broth had become cloudy and a single drop contained numerous microscopic creatures. He argued that the new microbes must have arisen spontaneously. In reality, however, he likely did not boil the broth enough to kill all preexisting microbes.

a) drawing of Francesco Redi. B) drawing of John Needham c) drawing of Lazzaro Spallanzani.

Describe the theory of spontaneous generation and some of the arguments used to support it.
Explain how the experiments of Redi and Spallanzani challenged the theory of spontaneous generation.

Disproving Spontaneous Generation

a) Photo of Louis Pasteur b) Photo of Pasteur’s swan-necked flask, c) A drawing of Pasteur’s experiment that disproved the theory of spontaneous generation.

How did Pasteur’s experimental design allow air, but not microbes, to enter, and why was this important?
What was the control group in Pasteur’s experiment and what did it show?

Key Takeaways

The theory of spontaneous generation states that life arose from nonliving matter. It was a long-held belief dating back to Aristotle and the ancient Greeks.
Experimentation by Francesco Redi in the 17th century presented the first significant evidence refuting spontaneous generation by showing that flies must have access to meat for maggots to develop on the meat. Prominent scientists designed experiments and argued both in support of (John Needham) and against (Lazzaro Spallanzani) spontaneous generation.
Louis Pasteur is credited with conclusively disproving the theory of spontaneous generation with his famous swan-neck flask experiment. He subsequently proposed that “life only comes from life.”

Multiple Choice

Fill in the blank, short answer.

Explain in your own words Pasteur’s swan-neck flask experiment.
Explain why the experiments of Needham and Spallanzani yielded in different results even though they used similar methodologies.

Critical Thinking

What would the results of Pasteur’s swan-neck flask experiment have looked like if they supported the theory of spontaneous generation?

Media Attributions

OSC_Microbio_03_01_Rediexpt
https://link.springer.com/content/pdf/10.1007%2Fs10739-017-9494-7.pdf ↵
E. Capanna. “Lazzaro Spallanzani: At the Roots of Modern Biology.” Journal of Experimental Zoology 285 no. 3 (1999):178–196. ↵
R. Mancini, M. Nigro, G. Ippolito. “Lazzaro Spallanzani and His Refutation of the Theory of Spontaneous Generation.” Le Infezioni in Medicina 15 no. 3 (2007):199–206. ↵
R. Vallery-Radot. The Life of Pasteur , trans. R.L. Devonshire. New York: McClure, Phillips and Co, 1902, 1:142. ↵

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3 1.2 Spontaneous Generation

Learning objectives.

Explain the theory of spontaneous generation and why people once accepted it as an explanation for the existence of certain types of organisms
Explain how certain individuals (van Helmont, Redi, Needham, Spallanzani, and Pasteur) tried to prove or disprove spontaneous generation

CLINICAL FOCUS: Part 1

What types of respiratory disease may be responsible?

Jump to the next Clinical Focus box

The Theory of Spontaneous Generation

The Greek philosopher Aristotle (384–322 BC) was one of the earliest recorded scholars to articulate the theory of spontaneous generation, the notion that life can arise from nonliving matter. Aristotle proposed that life arose from nonliving material if the material contained pneuma (“vital heat”). As evidence, he noted several instances of the appearance of animals from environments previously devoid of such animals, such as the seemingly sudden appearance of fish in a new puddle of water. [1]

This theory persisted into the 17th century, when scientists undertook additional experimentation to support or disprove it. By this time, the proponents of the theory cited how frogs simply seem to appear along the muddy banks of the Nile River in Egypt during the annual flooding. Others observed that mice simply appeared among grain stored in barns with thatched roofs. When the roof leaked and the grain moulded, mice appeared. Jan Baptista van Helmont , a 17th century Flemish scientist, proposed that mice could arise from rags and wheat kernels left in an open container for 3 weeks. In reality, such habitats provided ideal food sources and shelter for mouse populations to flourish.

However, one of van Helmont’s contemporaries, Italian physician Francesco Redi (1626–1697), performed an experiment in 1668 that was one of the first to refute the idea that maggots (the larvae of flies) spontaneously generate on meat left out in the open air. He predicted that preventing flies from having direct contact with the meat would also prevent the appearance of maggots. Redi left meat in each of six containers ( Figure 1.10 ). Two were open to the air, two were covered with gauze, and two were tightly sealed. His hypothesis was supported when maggots developed in the uncovered jars, but no maggots appeared in either the gauze-covered or the tightly sealed jars. He concluded that maggots could only form when flies were allowed to lay eggs in the meat, and that the maggots were the offspring of flies, not the product of spontaneous generation.

In 1745, John Needham (1713–1781) published a report of his own experiments, in which he briefly boiled broth infused with plant or animal matter, hoping to kill all preexisting microbes. [2] He then sealed the flasks. After a few days, Needham observed that the broth had become cloudy and a single drop contained numerous microscopic creatures. He argued that the new microbes must have arisen spontaneously. In reality, however, he likely did not boil the broth enough to kill all preexisting microbes.

Describe the theory of spontaneous generation and some of the arguments used to support it.
Explain how the experiments of Redi and Spallanzani challenged the theory of spontaneous generation.

Disproving Spontaneous Generation

Later, Pasteur made a series of flasks with long, twisted necks (“swan-neck” flasks), in which he boiled broth to sterilize it ( Figure 1.12 ). His design allowed air inside the flasks to be exchanged with air from the outside, but prevented the introduction of any airborne microorganisms, which would get caught in the twists and bends of the flasks’ necks. If a life force besides the airborne microorganisms were responsible for microbial growth within the sterilized flasks, it would have access to the broth, whereas the microorganisms would not. He correctly predicted that sterilized broth in his swan-neck flasks would remain sterile as long as the swan necks remained intact. However, should the necks be broken, microorganisms would be introduced, contaminating the flasks and allowing microbial growth within the broth.

How did Pasteur’s experimental design allow air, but not microbes, to enter, and why was this important?
What was the control group in Pasteur’s experiment and what did it show?

Key Takeaways

The theory of spontaneous generation states that life arose from nonliving matter. It was a long-held belief dating back to Aristotle and the ancient Greeks.
Experimentation by Francesco Redi in the 17th century presented the first significant evidence refuting spontaneous generation by showing that flies must have access to meat for maggots to develop on the meat. Prominent scientists designed experiments and argued both in support of (John Needham) and against (Lazzaro Spallanzani) spontaneous generation.
Louis Pasteur is credited with conclusively disproving the theory of spontaneous generation with his famous swan-neck flask experiment. He subsequently proposed that “life only comes from life.”

Multiple Choice

Fill in the blank, short answer.

Explain in your own words Pasteur’s swan-neck flask experiment.
Explain why the experiments of Needham and Spallanzani yielded in different results even though they used similar methodologies.

Critical Thinking

What would the results of Pasteur’s swan-neck flask experiment have looked like if they supported the theory of spontaneous generation?
https://link.springer.com/content/pdf/10.1007%2Fs10739-017-9494-7.pdf ↵
E. Capanna. “Lazzaro Spallanzani: At the Roots of Modern Biology.” Journal of Experimental Zoology 285 no. 3 (1999):178–196. ↵
R. Mancini, M. Nigro, G. Ippolito. “Lazzaro Spallanzani and His Refutation of the Theory of Spontaneous Generation.” Le Infezioni in Medicina 15 no. 3 (2007):199–206. ↵
R. Vallery-Radot. The Life of Pasteur , trans. R.L. Devonshire. New York: McClure, Phillips and Co, 1902, 1:142. ↵

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Unit 1: An Invisible World

Spontaneous generation, learning objectives.

Explain the theory of spontaneous generation and why people once accepted it as an explanation for the existence of certain types of organisms
Explain how certain individuals (van Helmont, Redi, Needham, Spallanzani, and Pasteur) tried to prove or disprove spontaneous generations.

The Theory of Spontaneous Generation

The Greek philosopher Aristotle (384–322 BC) was one of the earliest recorded scholars to articulate the theory of spontaneous generation , the notion that life can arise from nonliving matter. Aristotle proposed that life arose from nonliving material if the material contained pneuma (“vital heat”). As evidence, he noted several instances of the appearance of animals from environments previously devoid of such animals, such as the seemingly sudden appearance of fish in a new puddle of water. [1]

This theory persisted into the seventeenth century, when scientists undertook additional experimentation to support or disprove it. By this time, the proponents of the theory cited how frogs simply seem to appear along the muddy banks of the Nile River in Egypt during the annual flooding. Others observed that mice simply appeared among grain stored in barns with thatched roofs. When the roof leaked and the grain molded, mice appeared. Jan Baptista van Helmont , a seventeenth century Flemish scientist, proposed that mice could arise from rags and wheat kernels left in an open container for 3 weeks. In reality, such habitats provided ideal food sources and shelter for mouse populations to flourish.

However, one of van Helmont’s contemporaries, Italian physician Francesco Redi (1626–1697), performed an experiment in 1668 that was one of the first to refute the idea that maggots (the larvae of flies) spontaneously generate on meat left out in the open air. He predicted that preventing flies from having direct contact with the meat would also prevent the appearance of maggots. Redi left meat in each of six containers (Figure 1). Two were open to the air, two were covered with gauze, and two were tightly sealed. His hypothesis was supported when maggots developed in the uncovered jars, but no maggots appeared in either the gauze-covered or the tightly sealed jars. He concluded that maggots could only form when flies were allowed to lay eggs in the meat, and that the maggots were the offspring of flies, not the product of spontaneous generation.

Figure 1. Francesco Redi’s experimental setup consisted of an open container, a container sealed with a cork top, and a container covered in mesh that let in air but not flies. Maggots only appeared on the meat in the open container. However, maggots were also found on the gauze of the gauze-covered container.

In 1745, John Needham (1713–1781) published a report of his own experiments, in which he briefly boiled broth infused with plant or animal matter, hoping to kill all preexisting microbes. [2] He then sealed the flasks. After a few days, Needham observed that the broth had become cloudy and a single drop contained numerous microscopic creatures. He argued that the new microbes must have arisen spontaneously. In reality, however, he likely did not boil the broth enough to kill all preexisting microbes.

Think about It

Describe the theory of spontaneous generation and some of the arguments used to support it.
Explain how the experiments of Redi and Spallanzani challenged the theory of spontaneous generation.

Disproving Spontaneous Generation

The debate over spontaneous generation continued well into the nineteenth century, with scientists serving as proponents of both sides. To settle the debate, the Paris Academy of Sciences offered a prize for resolution of the problem. Louis Pasteur, a prominent French chemist who had been studying microbial fermentation and the causes of wine spoilage, accepted the challenge. In 1858, Pasteur filtered air through a gun-cotton filter and, upon microscopic examination of the cotton, found it full of microorganisms, suggesting that the exposure of a broth to air was not introducing a “life force” to the broth but rather airborne microorganisms.

Later, Pasteur made a series of flasks with long, twisted necks (“swan-neck” flasks), in which he boiled broth to sterilize it (Figure 3). His design allowed air inside the flasks to be exchanged with air from the outside, but prevented the introduction of any airborne microorganisms, which would get caught in the twists and bends of the flasks’ necks. If a life force besides the airborne microorganisms were responsible for microbial growth within the sterilized flasks, it would have access to the broth, whereas the microorganisms would not. He correctly predicted that sterilized broth in his swan-neck flasks would remain sterile as long as the swan necks remained intact. However, should the necks be broken, microorganisms would be introduced, contaminating the flasks and allowing microbial growth within the broth.

Pasteur’s set of experiments irrefutably disproved the theory of spontaneous generation and earned him the prestigious Alhumbert Prize from the Paris Academy of Sciences in 1862. In a subsequent lecture in 1864, Pasteur articulated “ Omne vivum ex vivo ” (“Life only comes from life”). In this lecture, Pasteur recounted his famous swan-neck flask experiment, stating that “life is a germ and a germ is life. Never will the doctrine of spontaneous generation recover from the mortal blow of this simple experiment.” [4] To Pasteur’s credit, it never has.

a) Photo of Louis Pasteur b) Photo of Pasteur’s flask – a round flask that is only opened to the outside through a long S-shaped tube. c) A drawing of Pasteur’s experiment. The top diagram shows the swan-neck flask from (b) containing broth that is being boiled to kill microorganisms in the broth. After the boiling process the cooled flask remains sterile because the curve of the flask prevents outside air from entering the flask. So, no contamination occurs. The bottom diagram shows the same flask being boiled. Next, the swan-neck is removed and the flask is opened to the environment. When the neck of the flask is broken off, bacteria reach the sterile broth and organism growth occurs. This is seen as cloudiness in the broth.

Figure 3. (a) French scientist Louis Pasteur, who definitively refuted the long-disputed theory of spontaneous generation. (b) The unique swan-neck feature of the flasks used in Pasteur’s experiment allowed air to enter the flask but prevented the entry of bacterial and fungal spores. (c) Pasteur’s experiment consisted of two parts. In the first part, the broth in the flask was boiled to sterilize it. When this broth was cooled, it remained free of contamination. In the second part of the experiment, the flask was boiled and then the neck was broken off. The broth in this flask became contaminated. (credit b: modification of work by “Wellcome Images”/Wikimedia Commons)

How did Pasteur’s experimental design allow air, but not microbes, to enter, and why was this important?
What was the control group in Pasteur’s experiment and what did it show?

Key Concepts and Summary

The theory of spontaneous generation states that life arose from nonliving matter. It was a long-held belief dating back to Aristotle and the ancient Greeks.
Experimentation by Francesco Redi in the seventeenth century presented the first significant evidence refuting spontaneous generation by showing that flies must have access to meat for maggots to develop on the meat. Prominent scientists designed experiments and argued both in support of (John Needham) and against (Lazzaro Spallanzani) spontaneous generation.
Louis Pasteur is credited with conclusively disproving the theory of spontaneous generation with his famous swan-neck flask experiment. He subsequently proposed that “life only comes from life.”

Multiple Choice

Which of the following individuals argued in favor of the theory of spontaneous generation?

Francesco Redi
Louis Pasteur
John Needham
Lazzaro Spallanzani

Which of the following individuals is credited for definitively refuting the theory of spontaneous generation using broth in swan-neck flask?

Jan Baptista van Helmont

Which of the following experimented with raw meat, maggots, and flies in an attempt to disprove the theory of spontaneous generation.

Antonie van Leeuwenhoek

Fill in the Blank

The assertion that “life only comes from life” was stated by Louis Pasteur in regard to his experiments that definitively refuted the theory of ___________.

Exposure to air is necessary for microbial growth.

Explain in your own words Pasteur’s swan-neck flask experiment.
Explain why the experiments of Needham and Spallanzani yielded in different results even though they used similar methodologies.
What would the results of Pasteur’s swan-neck flask experiment have looked like if they supported the theory of spontaneous generation?
K. Zwier. "Aristotle on Spontaneous Generation." http://www.sju.edu/int/academics/cas/resources/gppc/pdf/Karen%20R.%20Zwier.pdf ↵
E. Capanna. "Lazzaro Spallanzani: At the Roots of Modern Biology." Journal of Experimental Zoology 285 no. 3 (1999):178–196. ↵
R. Mancini, M. Nigro, G. Ippolito. "Lazzaro Spallanzani and His Refutation of the Theory of Spontaneous Generation." Le Infezioni in Medicina 15 no. 3 (2007):199–206. ↵
R. Vallery-Radot. The Life of Pasteur , trans. R.L. Devonshire. New York: McClure, Phillips and Co, 1902, 1:142. ↵
OpenStax Microbiology. Provided by : OpenStax CNX. Located at : http://cnx.org/contents/[email protected] . License : CC BY: Attribution . License Terms : Download for free at http://cnx.org/contents/[email protected]

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Lazzaro Spallanzani

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The Embryo Project Encyclopedia - Biography of Lazzaro Spallanzani
Lazzaro Spallanzani - Student Encyclopedia (Ages 11 and up)

Lazzaro Spallanzani (born Jan. 12, 1729, Modena , Duchy of Modena—died 1799, Pavia, Cisalpine Republic) was an Italian physiologist who made important contributions to the experimental study of bodily functions and animal reproduction . His investigations into the development of microscopic life in nutrient culture solutions paved the way for the research of Louis Pasteur .

Spallanzani was the son of a distinguished lawyer. He attended the Jesuit college at Reggio, where he received a sound education in the classics and philosophy. He was invited to join the order, but, although he was eventually ordained (in 1757), he declined this offer and went to Bologna to study law. Under the influence of his kinswoman Laura Bassi , a professor of mathematics , he became interested in science . In 1754 Spallanzani was appointed professor of logic , metaphysics , and Greek at Reggio College and in 1760 professor of physics at the University of Modena.

Michael Faraday (L) English physicist and chemist (electromagnetism) and John Frederic Daniell (R) British chemist and meteorologist who invented the Daniell cell.

Although Spallanzani published in 1760 an article critical of a new translation of the Iliad, all of his leisure was being devoted to scientific research. In 1766 he published a monograph on the mechanics of stones that bounce when thrown obliquely across water. His first biological work, published in 1767, was an attack on the biological theory suggested by Georges Buffon and John Turberville Needham , who believed that all living things contain, in addition to inanimate matter, special “ vital atoms ” that are responsible for all physiological activities. They postulated that, after death, the “vital atoms” escape into the soil and are again taken up by plants. The two men claimed that the small moving objects seen in pond water and in infusions of plant and animal matter are not living organisms but merely “vital atoms” escaping from the organic material. Spallanzani studied various forms of microscopic life and confirmed the view of Antonie van Leeuwenhoek that such forms are living organisms. In a series of experiments he showed that gravy, when boiled, did not produce these forms if placed in phials that were immediately sealed by fusing the glass. As a result of this work, he concluded that the objects in pond water and other preparations were living organisms introduced from the air and that Buffon’s views were without foundation.

The range of Spallanzani’s experimental interest expanded. The results of his regeneration and transplantation experiments appeared in 1768. He studied regeneration in a wide range of animals including planarians, snails, and amphibians and reached a number of general conclusions: the lower animals have greater regenerative power than the higher; young individuals have a greater capacity for regeneration than the adults of the same species; and, except in the simplest animals, it is the superficial parts not the internal organs that can regenerate. His transplantation experiments showed great experimental skill and included the successful transplant of the head of one snail onto the body of another. In 1773 he investigated the circulation of the blood through the lungs and other organs and did an important series of experiments on digestion , in which he obtained evidence that digestive juice contains special chemicals that are suited to particular foods. At the request of his friend Charles Bonnet , Spallanzani investigated the male contribution to generation . Although the spermatozoa had first been seen in the 17th century, their function was not understood until some 30 years after the formulation of the cell theory in 1839. As a result of his earlier investigations into simple animals, Spallanzani supported the prevailing view that the spermatozoa were parasites within the semen . Both Bonnet and Spallanzani accepted the preformation theory . According to their version of this theory, the germs of all living things were created by God in the beginning and were encapsulated within the first female of each species. Thus, the new individual present in each egg was not formed de novo but developed as the result of an expansion of parts the delineation of which had been laid down within the germ by God at the creation. It was assumed that the semen provided a stimulus for this expansion, but it was not known if contact was essential nor if all the parts of the semen were required. Using amphibians, Spallanzani showed that actual contact between egg and semen is essential for the development of a new animal and that filtered semen becomes less and less effective as filtration becomes more and more complete. He noted that the residue on the filter paper retained all its original power if it were immediately added to the water containing the eggs. Spallanzani concluded that it was the solid parts of the secretion, proteinaceous and fatty substances that form the bulk of the semen, that were essential, and he continued to regard the spermatozoa as inessential parasites. Despite this error, Spallanzani performed some of the first successful artificial insemination experiments on lower animals and on a dog.

As Spallanzani’s fame grew, he became a fellow of most of the scientific societies in Europe. In 1769 he accepted a chair at the University of Pavia , where, despite other offers, he remained for the rest of his life. He was popular with students and colleagues. Once a small group, jealous of his success, accused him of malpractice in association with the museum that he controlled, but he was soon vindicated . Spallanzani took every opportunity to travel, to study new phenomena, and to meet other scientists. The accounts of his journeys to Constantinople and Sicily still provide interesting reading. Toward the end of his life he conducted further research on microscopic animals and plants that he had started early in his career; he also began studies on the electric charge of the torpedo fish and sense organs in bats. In his last set of experiments, published posthumously, he attempted to show that the conversion of oxygen to carbon dioxide must occur in tissues, not in the lungs (as Antoine-Laurent Lavoisier had suggested in 1787).

Lazzaro Spallanzani (1729-1799)

Lazzaro Spallanzani’s imaginative application of experimental methods, mastery of microscopy, and wide interests led him to significant contributions in natural history, experimental biology, and physiology. His detailed and thoughtful observations illuminated a broad spectrum of problems ranging from regeneration to the genesis of thunderclouds.

Born in the small town of Scandiano in northern Italy on 10 January 1729, Spallanzani grew up in a large, wealthy family and attended local schools until he was fifteen. He then studied at a Jesuit seminary in Reggio Emilia where his intellectual abilities earned him the nickname “the astrologer.” He matriculated in 1749 at the University of Bologna and began working toward a degree in jurisprudence. His love for the natural sciences and mathematics soon led him to change his focus to philosophy, in which he earned his doctorate in 1754. His philosophical studies encompassed metaphysics and theology, which prepared him to take minor orders and be ordained as a priest in the Roman Catholic Church. Spallanzani’s affiliation with the Church provided financial support, but more importantly offered protection from the Italian Inquisition, which often censored work deemed contrary to Catholic doctrine. He continued to officiate mass from time to time until later in life. In 1755 he was appointed to teach humanities at the College of Reggio Emilia and then went on to be professor of philosophy at Modena in the University and College of Nobles. He indicated, however, in a letter to Charles Bonnet, that his teaching responsibilities robbed him of his time, which he preferred to dedicate to scientific pursuits.

Spallanzani read voraciously but was a persistent skeptic, hesitant to believe anything that he could not prove himself. Unconvinced by Needham and Buffon’s description of the genesis of animalcules in plant and animal infusions, Spallanzani carefully replicated their study and showed their techniques were inadequate and therefore that their conclusions about the existence of spontaneous generation were unwarranted. He published his results refuting spontaneous generation in 1765 and thereby initiated a lifelong correspondence with Bonnet. An avid and staunch preformationist, Bonnet seized upon Spallanzani’s results to support his theoretical inclinations and challenged him to carry on his own work investigating regeneration in flatworms. Spallanzani rose to the challenge and returned Bonnet’s letter with an explanation of his many sectioning experiments on a wide variety of animals.

Spallanzani performed hundreds of salamander tail amputations, believing exhaustive repetition was necessary to confirm results. Interested in the origin of regenerating tissue, he closely examined the interface between the stump and the regenerated tail. Observation alone offered no conclusions. He had trouble believing that an organized tail could result from a simple outgrowth, but continued to look for evidence in regenerating tadpole and salamander tails that could support his inclination toward the existence of preformed germs. He openly reported his observations, even those that questioned preformationism, once suggesting that tail regenerates in tadpoles appeared to be the result of an elongation, a comment which surely must have disturbed Bonnet but nevertheless failed to persuade him to consider epigenesis seriously.

Interested in questions about generation, Spallanzani performed the first artificial insemination of a viviparous animal, a spaniel dog, a feat he recognized as one of his greatest accomplishments. These results further convinced him of the ovist preformationist doctrine. He interpreted his many findings as evidence against epigenesis and the role of sperm, which he identified as “animalcules,” in generation.

In 1776 Spallanzani accepted a professorship at the University of Pavia where he remained for the next thirty years and published extensively. He was a member of the ten most distinguished Italian academies and a foreign associate to another dozen scientific societies across Europe. His work has been celebrated for its creative approach and rigorous use of scientific methodologies inspiring many scientists, including Thomas Hunt Morgan, to revisit his studies.

Dinsmore, Charles E., ed. “Lazzaro Spallanzani: Concepts of Generation and Regeneration.” in A History of Regeneration Research: Milestones in the Evolution of a Science , 67–89. Cambridge: Cambridge University Press, 1991.
Dolman, Claude E. “Spallanzani, Lazzaro.” Dictionary of Scientific Biography Volume 12: 553–67.

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Spontaneous Generation Theory

Table of Contents

Aristotle’s Work

Early experiments, franceso redi, pier antonio micheli, john needham, lazzaro spallanzani, disproving the theory, louis pasteur, john tyndall, frequently asked questions.

Spontaneous generation theory is an archaic scientific theory which stated that living organisms could arise from nonliving matter and that such a process was regular in nature. It also explained the origin of life from the nonliving subjects. According to that theory, a piece of bread and cheese wrapped and left in a corner could give rise to mice in a few weeks, or maggots could rise from dead flesh.

The hypothesis was designed by Aristotle on the basis of previous work of natural philosophers and the theory held its place for two millenniums. Francesco Redi and Lazzaro Spallanzani then challenged this theory in the 17th and 18th centuries, but it was still not discredited. It was not until the work of Louis Pasteur and John Tyndall in the 19th century that this theory was finally disproved.

The theory lines up with the theory of origin of life, which states the process of abiogenesis. Abiogenesis is the natural process of creation of simple organic compounds from nonliving matter. The term equivocal generation, also called heterogenesis, describes the theory of spontaneous generation. According to equivocal generation, one life arises from another unrelated life form.

According to Aristotle, every living being is made up of a compound of matter and form. In his sexual theory of reproduction, he stated that male’s semen was efficient cause that passed down characteristics to female matter (menstrual blood), and gave rise to its offspring. He believed that the male semen and female matter were refinements that were produced by bodies as a result of their proportions of heat, ingested food and were a byproduct of the elements earth and water. Yet, he believed that creatures arose from spontaneous generation and not sexual reproduction.

Analogous to his sexual reproduction theory, he said that non living matter just like seminal fluid had ‘pneuma’ or ‘vital heat’ that endowed the subtances with vital properties. He came to the conclusion that whether a life form arose from sexual reproduction or spontaneous generation, they were a result of interaction between vital heat and elemental matter.

Franceso Redi was an Italian naturalist who challenged the ancient belief of spontaneous generation of maggots on decaying meat in 1668. He believed that maggots could be prevented if flies were not allowed direct contact with the meat. He designed an experiment where he put pieces of meat in six different containers. He covered two of them with gauze, two tightly sealed with corks and left the remaining two open in the air. His hypothesis came true as it was observed that there were no maggots in the covered (with gauze and cork) containers but maggots were observed in the open container. He came to the conclusion that flies were able to lay their eggs on the open piece of meat and that the maggots were their offspring who grew on flesh.

Pier Antonio Micheli, an Italian botanist, performed another experiment in 1729 where he placed fungal spores on a slice of melon and observed that the same was produced on the melon slice. He concluded that the new spores definitely did not arise from spontaneous generation.

John Needham, an English biologist, did yet another experiment in 1745 with boiled broths. He infused a broth by mixing plant and animal matter and boiled it in the belief that it would kill all the microorganisms . He sealed the broth and left it for a few days. He observed that the broth had become cloudy and that it has microscopic organisms in it. He reiterated the spontaneous generation theory and many of his peers believed him. However, in reality, the broth was not boiled vigorously so as to kill all the microorganisms.

Lazzaro Spallanzani, an Italian biologist, reattempted Needham’s experiment in 1768. He took animal and plant matter-infused broths and boiled them vigorously. He kept one of the jars sealed and left the other one open to the air. According to his observations, the sealed jar was clear and did not have any growth. He then concluded that air was the force that was introducing microbes into the flask.

By this time, there was increased skepticism among scientists about the spontaneous generation theory.

In 1859, Louis Pasteur, a French microbiologist conducted another broth experiment that settled the question of spontaneous generation once and for all. He took swan flasks that had twisted necks for the experiment and boiled meat broth in it. The design of the flask was such that it allowed exchange or air from outside to inside but prevented the entry of microorganisms. If any microbes were to enter the flask they would get caught in the twisted neck of the flask. The broth remained clear for a long amount of time as long as the flask was kept intact. Once the flask was turned, which led to entry of microbes into the broth, it became cloudy.

John Tyndall, an Irish physicist, advanced the work of Louis Pasteur and finally the theory of spontaneous generation was disproved. Not much is known about Tyndall’s experiment on spontaneous generation.

In 1862, the French Academy of Sciences, announced a prize for the scientists who shed new light on the spontaneous generation controversy and appointed a jury to decide the winner. Louis pasteur was awarded the Alhumbert Prize from the Paris Academy of Sciences for his work that totally threw away the concept of spontaneous generation. 1n 1864, Pasteur was quoted saying in a lecture: “Omne vivum ex vivo” (“Life only comes from life”). Pasteur and other scientists started to use the word biogenesis for the origin of life which again meant that life comes only from another life.

This sums up the theory of spontaneous generation. Keep visiting BYJU’S Biology for more interesting topics.

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What is spontaneous generation and who disproved the theory, what is the difference between cell theory and spontaneous generation, what is another name for spontaneous generation.

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Origin of Life: Spontaneous Generation

Spontaneous Generation

Origin of Life

Introduction
Early Earth Environment

It was once believed that life could come from nonliving things, such as mice from corn, flies from bovine manure, maggots from rotting meat, and fish from the mud of previously dry lakes. Spontaneous generation is the incorrect hypothesis that nonliving things are capable of producing life. Several experiments have been conducted to disprove spontaneous generation; a few of them are covered in the sections that follow.

Redi's Experiment and Needham's Rebuttal

In 1668, Francesco Redi, an Italian scientist, designed a scientific experiment to test the spontaneous creation of maggots by placing fresh meat in each of two different jars. One jar was left open; the other was covered with a cloth. Days later, the open jar contained maggots, whereas the covered jar contained no maggots. He did note that maggots were found on the exterior surface of the cloth that covered the jar. Redi successfully demonstrated that the maggots came from fly eggs and thereby helped to disprove spontaneous generation. Or so he thought.

In England, John Needham challenged Redi's findings by conducting an experiment in which he placed a broth, or gravy, into a bottle, heated the bottle to kill anything inside, then sealed it. Days later, he reported the presence of life in the broth and announced that life had been created from nonlife. In actuality, he did not heat it long enough to kill all the microbes.

Spallanzani's Experiment

Lazzaro Spallanzani, also an Italian scientist, reviewed both Redi's and Needham's data and experimental design and concluded that perhaps Needham's heating of the bottle did not kill everything inside. He constructed his own experiment by placing broth in each of two separate bottles, boiling the broth in both bottles, then sealing one bottle and leaving the other open. Days later, the unsealed bottle was teeming with small living things that he could observe more clearly with the newly invented microscope. The sealed bottle showed no signs of life. This certainly excluded spontaneous generation as a viable theory. Except it was noted by scientists of the day that Spallanzani had deprived the closed bottle of air, and it was thought that air was necessary for spontaneous generation. So although his experiment was successful, a strong rebuttal blunted his claims.

Pasteurization originally was the process of heating foodstuffs to kill harmful microorganisms before human consumption; now ultraviolet light, steam, pressure, and other methods are available to purify foodsin the name of Pasteur.

Pasteur's Experiment

Louis Pasteur, the notable French scientist, accepted the challenge to re-create the experiment and leave the system open to air. He subsequently designed several bottles with S-curved necks that were oriented downward so gravity would prevent access by airborne foreign materials. He placed a nutrient-enriched broth in one of the goose-neck bottles, boiled the broth inside the bottle, and observed no life in the jar for one year. He then broke off the top of the bottle, exposing it more directly to the air, and noted life-forms in the broth within days. He noted that as long as dust and other airborne particles were trapped in the S-shaped neck of the bottle, no life was created until this obstacle was removed. He reasoned that the contamination came from life-forms in the air. Pasteur finally convinced the learned world that even if exposed to air, life did not arise from nonlife.

Excerpted from The Complete Idiot's Guide to Biology © 2004 by Glen E. Moulton, Ed.D.. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with Alpha Books , a member of Penguin Group (USA) Inc.

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Origin of Prokaryotes and Eukaryotes: Origin of Prokaryotes

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The Theory of Biogenesis

What is Biogenesis?

An important theory in biology and molecular genetics, Biogenesis postulates the production of new living organisms from pre-existing life. Read ahead as we explore this seminal theory that changed age-old beliefs.

Biogenesis is based on the theory that life can only come from life, and it refers to any process by which a lifeform can give rise to other lifeforms. For instance, a chicken laying eggs, which hatch and become baby chicken.

Meaning of Biogenesis

The term ‘biogenesis’ comes from ‘bio’ meaning ‘life’, and ‘ genesis’, meaning ‘beginning’. Rudolf Virchow, in 1858, had come up with the hypothesis of biogenesis, but could not experimentally prove it. In 1859, Louis Pasteur set up his demonstrative experiments to prove biogenesis right down to a bacterial level. By 1861, he succeeded in establishing biogenesis as a solid theory rather than a controversial hypothesis.

What Was the Idea of Spontaneous Generation?

The belief in a spontaneous generation is age-old, quite literally. Aristotle in Ancient Greece first pronounces the idea. And consequently, the idea also came to be known as Aristotelian Abiogenesis.

The reason behind the resounding faith in this idea was perhaps the elusive and stealthy nature of the creatures attributed to it, i.e, mice, bacteria, flies, maggots, etc.

The 18th-century path-breaking invention of the microscope that allows most of these creatures, so we can observe them under the microscope and de-mystify their origin. By the time Pasteur set about to do his work in the field, macroscopic biogenesis was already accepted by the scientific community at large. He only had to confirm microscopic biogenesis to prove the hypothesis beyond doubt.

Macroscopic Biogenesis: Francesco Redi’s Experiment

Francesco Redi, as far back as 1668, had set out to refute the idea of macroscopic spontaneous generation, by publishing the results of his experimentation on the matter. Instead of his experiment , Redi had placed some rotting meat in two containers, one with a piece of gauze covering the opening, and the other without it.

He noticed that in the container without the gauze, maggots would grow on the meat itself. However, when he provided the gauze, the maggots would appear on the gauze instead of on the meat. He also observed that flies tend to lay eggs as close to a food source as possible. Thus, he surmised the possibility of macroscopic biogenesis.

Microscopic Biogenesis

Spallanzani’s experiment.

Source: Emaze

He solved this problem by drawing out all the air in the container after sealing it. After experimenting with this manner, he achieved his desired results of a broth that had not clouded with bacterial growth, in line with the theory of biogenesis.

However, his inference was countered by critics who asserted that air was indispensable to support life, therefore the lack of bacterial growth should be attributed to the lack of air, rather than the fact that bacteria spread through contamination. For almost a century since this criticism lay unchallenged.

Pasteur’s Experiment

The caveat of Pasteur’s 1859 experiment was to establish that microbes live suspended in air, and can contaminate food and water, however, the microbes do not simply appear out of thin air. As the primary step to his experiment, Pasteur boiled beef broth in a special flask that had its long neck bent downwards and then upwards.

This interesting contraption ensured the free diffusion of air, and at the same time prevent any bacterial contamination. As long as the apparatus remained upright, the flask remained free of any bacterial growth.

Once we slant the flask, it allows the broth to pass beyond the ‘goose-neck’ bend of the flask’s neck. The broth became clouded with bacterial growth in no time. This path-breaking experiment not only silenced all the criticism based on Spallanzani’s experiment but also cemented the Law of Biogenesis.

Law of Biogenesis Vs. Evolutionary Theory

Scientist fears that the law of biogenesis opposes the theory of evolution. It has surmised that all life stems from inorganic matter from billions of years ago. However, biogenesis simply refutes the theory of spontaneous generation and delves in a matter of generational time-span, and not of what may be achieved over thousands of generations.

While the evolutionary theories take into account the lack of predators, the difference in the chemical composition of the Earth’s atmosphere during the inception of life on Earth, as well as the trial-and-error that had taken place over millions of years to bring us to the stage of life on this planet we witness now, these do not concern the law of biogenesis at all.

Whereas the evolutionary theory demonstrates how life on earth took millions of years of trial-and-error and conducive but very different atmospheric conditions, the theory of spontaneous generation had asserted that complex life could simply appear fully formed in a matter of days. This is the belief that biogenesis had successfully challenged.

Solved Question for You

Q. Who Has Propounded the Theory of Spontaneous Generation?

Spallanzani

Ans. C. Aristotle. The idea was first propounded by Aristotle in Ancient Greece. Consequently, the idea came to be known as Aristotelian Abiogenesis.

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Is Spontaneous Generation Real?

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For several centuries it was believed that living organisms could spontaneously come from nonliving matter. This idea, known as spontaneous generation, is now known to be false. Proponents of at least some aspects of spontaneous generation included well-respected philosophers and scientists such as Aristotle, Rene Descartes, William Harvey, and Isaac Newton . Spontaneous generation was a popular notion due to the fact that it seemed to be consistent with observations that a number of animal organisms would apparently arise from nonliving sources. Spontaneous generation was disproved through the performance of several significant scientific experiments.

Key Takeaways

Spontaneous generation is the idea that living organisms can spontaneously come from nonliving matter.
Over the years great minds like Aristotle and Isaac Newton were proponents of some aspects of spontaneous generation which have all been shown to be false.
Francesco Redi did an experiment with meat and maggots and concluded that maggots do not arise spontaneously from rotting meat.
The Needham and the Spallanzani experiments were additional experiments that were conducted to help disprove spontaneous generation.
The Pasteur experiment was the most famous experiment conducted that disproved spontaneous generation that was accepted by the majority of the scientific community. Pasteur demonstrated that bacteria appearing in broth are not the result of spontaneous generation.

Do Animals Spontaneously Generate?

Prior to the mid-19th century, it was commonly believed that the origin of certain animals was from nonliving sources. Lice were thought to come from dirt or sweat. Worms, salamanders, and frogs were thought to be birthed from the mud. Maggots were derived from rotting meat, aphids and beetles supposedly sprang from wheat, and mice were generated from soiled clothing mixed with wheat grains. While these theories seem quite ludicrous, at the time they were thought to be reasonable explanations for how certain bugs and other animals seemed to appear from no other living matter.

Spontaneous Generation Debate

While a popular theory throughout history, spontaneous generation was not without its critics. Several scientists set out to refute this theory through scientific experimentation. At the same time, other scientists tried to find evidence in support of spontaneous generation. This debate would last for centuries.

Redi Experiment

In 1668, the Italian scientist and physician Francesco Redi set out to disprove the hypothesis that maggots were spontaneously generated from rotting meat. He contended that the maggots were the result of flies laying eggs on exposed meat. In his experiment, Redi placed meat in several jars. Some jars were left uncovered, some were covered with gauze, and some were sealed with a lid. Over time, the meat in the uncovered jars and the jars covered with gauze became infested with maggots. However, the meat in the sealed jars did not have maggots. Since only the meat that was accessible to flies had maggots, Redi concluded that maggots do not spontaneously arise from meat.

Needham Experiment

In 1745, English biologist and priest John Needham set out to demonstrate that microbes, such as bacteria , were the result of spontaneous generation. Thanks to the invention of the microscope in the 1600s and increased improvements to its usage, scientists were able to view microscopic organisms such as fungi , bacteria, and protists. In his experiment, Needham heated chicken broth in a flask in order to kill any living organisms within the broth. He allowed the broth to cool and placed it in a sealed flask. Needham also placed unheated broth in another container. Over time, both the heated broth and unheated broth contained microbes. Needham was convinced that his experiment had proven spontaneous generation in microbes.

Spallanzani Experiment

In 1765, Italian biologist and priest Lazzaro Spallanzani, set out to demonstrate that microbes do not spontaneously generate. He contended that microbes are capable of moving through the air. Spallanzani believed that microbes appeared in Needham's experiment because the broth had been exposed to air after boiling but before the flask had been sealed. Spallanzani devised an experiment where he placed the broth in a flask, sealed the flask, and removed the air from the flask before boiling. The results of his experiment showed that no microbes appeared in the broth as long as it remained in its sealed condition. While it appeared that the results of this experiment had dealt a devastating blow to the idea of spontaneous generation in microbes, Needham argued that it was the removal of air from the flask that made spontaneous generation impossible.

Pasteur Experiment

In 1861, Louis Pasteur presented evidence that would virtually put an end to the debate. He designed an experiment similar to Spallanzani's, however, Pasteur's experiment implemented a way to filter out microorganisms. Pasteur used a flask with a long, curved tube called a swan-necked flask. This flask allowed air to have access to the heated broth while trapping dust containing bacterial spores in the curved neck of the tube. The results of this experiment were that no microbes grew in the broth. When Pasteur tilted the flask on its side allowing the broth access to the curved neck of the tube and then set the flask upright again, the broth became contaminated and bacteria reproduced in the broth. Bacteria also appeared in the broth if the flask was broken near the neck allowing the broth to be exposed to non-filtered air. This experiment demonstrated that bacteria appearing in broth are not the result of spontaneous generation. The majority of the scientific community considered this conclusive evidence against spontaneous generation and proof that living organisms only arise from living organisms.

Microscope, Through the. “Spontaneous Generation Was an Attractive Theory to Many People, but Was Ultimately Disproven.” Through the Microscope Main News , www.microbiologytext.com/5th_ed/book/displayarticle/aid/27.
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Microbe Notes

Experiments in support and against Spontaneous Generation

Spontaneous generation is an obsolete theory which states that living organisms can originate from inanimate objects.
The theory believed that dust created fleas, maggots arose from rotting meat, and bread or wheat left in a dark corner produced mice among others.
Although the idea that living things originate from the non-living may seem ridiculous today, the theory of spontaneous generation was hotly debated for hundreds of years.
During this time, many experiments were conducted to both prove and disprove the theory.

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Experiments in Support of Spontaneous Generation

The doctrine of spontaneous generation was coherently synthesized by Aristotle, who compiled and expanded the work of earlier natural philosophers and the various ancient explanations for the appearance of organisms, and was taken as scientific fact for two millennia.

The Greek philosopher Aristotle (384–322 BC) was one of the earliest recorded scholars to articulate the theory of spontaneous generation, the notion that life can arise from nonliving matter.
Aristotle proposed that life arose from nonliving material if the material contained pneuma (“vital heat”).
As evidence, he noted several instances of the appearance of animals from environments previously devoid of such animals, such as the seemingly sudden appearance of fish in a new puddle of water.

John Needham

The English naturalist John Turberville Needham was in support of the theory.
Needham found that large numbers of organisms subsequently developed in prepared infusions of many different substances that had been exposed to intense heat in sealed tubes for 30 minutes.
Assuming that such heat treatment must have killed any previous organisms, Needham explained the presence of the new population on the grounds of spontaneous generation.
By this time, the proponents of the theory cited how frogs simply seem to appear along the muddy banks of the Nile River in Egypt during the annual flooding.
Others observed that mice simply appeared among grain stored in barns with thatched roofs. When the roof leaked and the grain molded, mice appeared.
Jan Baptista van Helmont , a seventeenth century Flemish scientist, proposed that mice could arise from rags and wheat kernels left in an open container for 3 weeks.

Experiments against Spontaneous Generation

Though challenged in the 17th and 18th centuries by the experiments of Francesco Redi and Lazzaro Spallanzani, spontaneous generation was not disproved until the work of Louis Pasteur and John Tyndall in the mid-19th century.

Francesco Redi

The Italian physician and poet Francesco Redi was one of the first to question the spontaneous origin of living things.
Having observed the development of maggots and flies on decaying meat, Redi in 1668 devised a number of experiments, all pointing to the same conclusion: if flies are excluded from rotten meat, maggots do not develop. On meat exposed to air, however, eggs laid by flies develop into maggots.
He tested the spontaneous creation of maggots by placing fresh meat in each of two different jars.
One jar was left open; the other was covered with a cloth. Days later, the open jar contained maggots, whereas the covered jar contained no maggots.
He did note that maggots were found on the exterior surface of the cloth that covered the jar. Redi successfully demonstrated that the maggots came from fly eggs.

Lazzaro Spallanzani

The experiments of Needham appeared irrefutable until the Italian physiologist Lazzaro Spallanzani repeated them and obtained conflicting results.
He published his findings around 1775, claiming that Needham had not heated his tubes long enough, nor had he sealed them in a satisfactory manner.
Although Spallanzani’s results should have been convincing, Needham had the support of the influential French naturalist Buffon; hence, the matter of spontaneous generation remained unresolved.

Louis Pasteur

Louis Pasteur ‘s 1859 experiment is widely seen as having settled the question of spontaneous generation.
He boiled a meat broth in a flask that had a long neck that curved downward, like that of a goose or swan.
The idea was that the bend in the neck prevented falling particles from reaching the broth, while still allowing the free flow of air.
The flask remained free of growth for an extended period. When the flask was turned so that particles could fall down the bends, the broth quickly became clouded.
This work was so conclusive; that biology codified the “Law of Biogenesis,” which states that life only comes from previously existing life.

John Tyndall

Support for Pasteur’s findings came in 1876 from the English physicist John Tyndall, who devised an apparatus to demonstrate that air had the ability to carry particulate matter.
Because such matter in air reflects light when the air is illuminated under special conditions, Tyndall’s apparatus could be used to indicate when air was pure.
Tyndall found that no organisms were produced when pure air was introduced into media capable of supporting the growth of microorganisms.
It was those results, together with Pasteur’s findings, that put an end to the doctrine of spontaneous generation.
Parija S.C. (2012). Textbook of Microbiology & Immunology.(2 ed.). India: Elsevier India.
Sastry A.S. & Bhat S.K. (2016). Essentials of Medical Microbiology. New Delhi : Jaypee Brothers Medical Publishers.
https://study.com/academy/lesson/spontaneous-generation-definition-theory-examples.html
https://www.britannica.com/science/biology#ref498783
https://www.infoplease.com/science/biology/origin-life-spontaneous-generation
https://www.allaboutscience.org/what-is-spontaneous-generation-faq.htm
https://courses.lumenlearning.com/microbiology/chapter/spontaneous-generation/

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Sagar Aryal

3.1 – Spontaneous Generation

Learning objectives.

Explain the theory of spontaneous generation and why people once accepted it as an explanation for the existence of certain types of organisms
Explain how certain individuals (van Helmont, Redi, Needham, Spallanzani, and Pasteur) tried to prove or disprove spontaneous generation

The Theory of Spontaneous Generation

The Greek philosopher Aristotle (384–322 B.C.) was one of the earliest recorded scholars to articulate the theory of spontaneous generation, the notion that life can arise from nonliving matter. Aristotle proposed that life arose from nonliving material if the material contained pneuma (“vital heat”). As evidence, he noted several instances of the appearance of animals from environments previously devoid of such animals, such as the seemingly sudden appearance of fish in a new puddle of water. 1

This theory persisted into the 17th century, when scientists undertook additional experimentation to support or disprove it. By this time, the proponents of the theory cited how frogs simply seem to appear along the muddy banks of the Nile River in Egypt during the annual flooding. Others observed that mice simply appeared among grain stored in barns with thatched roofs. When the roof leaked and the grain molded, mice appeared. Jan Baptista van Helmont, a 17th century Flemish scientist, proposed that mice could arise from rags and wheat kernels left in an open container for 3 weeks. In reality, such habitats provided ideal food sources and shelter for mouse populations to flourish.

However, one of van Helmont’s contemporaries, Italian physician Francesco Redi (1626–1697), performed an experiment in 1668 that was one of the first to refute the idea that maggots (the larvae of flies) spontaneously generate on meat left out in the open air. He predicted that preventing flies from having direct contact with the meat would also prevent the appearance of maggots. Redi left meat in each of six containers (Figure 3.2). Two were open to the air, two were covered with gauze, and two were tightly sealed. His hypothesis was supported when maggots developed in the uncovered jars, but no maggots appeared in either the gauze-covered or the tightly sealed jars. He concluded that maggots could only form when flies were allowed to lay eggs in the meat, and that the maggots were the offspring of flies, not the product of spontaneous generation.

An illustration of Three jars with different lids

three drawings of three different people

Check Your Understanding

Describe the theory of spontaneous generation and some of the arguments used to support it.
Explain how the experiments of Redi and Spallanzani challenged the theory of spontaneous generation.

Disproving Spontaneous Generation

The debate over spontaneous generation continued well into the 19th century, with scientists serving as proponents of both sides. To settle the debate, the Paris Academy of Sciences offered a prize for resolution of the problem. Louis Pasteur, a prominent French chemist who had been studying microbial fermentation and the causes of wine spoilage, accepted the challenge. In 1858, Pasteur filtered air through a gun-cotton filter and, upon microscopic examination of the cotton, found it full of microorganisms, suggesting that the exposure of a broth to air was not introducing a “life force” to the broth but rather airborne microorganisms.

Later, Pasteur made a series of flasks with long, twisted necks (“swan-neck” flasks), in which he boiled broth to sterilize it (Figure 3.4). His design allowed air inside the flasks to be exchanged with air from the outside, but prevented the introduction of any airborne microorganisms, which would get caught in the twists and bends of the flasks’ necks. If a life force besides the airborne microorganisms were responsible for microbial growth within the sterilized flasks, it would have access to the broth, whereas the microorganisms would not. He correctly predicted that sterilized broth in his swan-neck flasks would remain sterile as long as the swan necks remained intact. However, should the necks be broken, microorganisms would be introduced, contaminating the flasks and allowing microbial growth within the broth.

Pasteur’s set of experiments irrefutably disproved the theory of spontaneous generation and earned him the prestigious Alhumbert Prize from the Paris Academy of Sciences in 1862. In a subsequent lecture in 1864, Pasteur articulated “Omne vivum ex vivo” (“Life only comes from life”). In this lecture, Pasteur recounted his famous swan-neck flask experiment, stating that “…life is a germ and a germ is life. Never will the doctrine of spontaneous generation recover from the mortal blow of this simple experiment.” 4 To Pasteur’s credit, it never has.

A photo with three parts, first a picture of Pasteur, then one of his flasks, then his process.

How did Pasteur’s experimental design allow air, but not microbes, to enter, and why was this important?
What was the control group in Pasteur’s experiment and what did it show?

K. Zwier. “Aristotle on Spontaneous Generation.” http://www.sju.edu/int/academics/cas/resources/gppc/pdf/Karen%20R.%20Zwier.pdf

E. Capanna. “Lazzaro Spallanzani: At the Roots of Modern Biology.” Journal of Experimental Zoology 285 no. 3 (1999):178–196.

R. Mancini, M. Nigro, G. Ippolito. “Lazzaro Spallanzani and His Refutation of the Theory of Spontaneous Generation.” Le Infezioni in Medicina 15 no. 3 (2007):199–206.

R. Vallery-Radot. The Life of Pasteur, trans. R.L. Devonshire. New York: McClure, Phillips and Co, 1902, 1:142.

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Krulwich Wonders

Krulwich wonders..., two glorious science experiments: one about sex, the other about lunch.

Robert Krulwich

Done right, a good science experiment is simple, clear and revealing. Done splendidly, it's a tale you don't forget. Let's do the sex one first. It took place in Italy, in the 1760s, when a Catholic priest and scholar, Lazzaro Spallanzani , was thinking about sperm — which is why he decided to dress frogs in pants, like this ...

Spallanzani designed "tight taffeta pants" for the male frogs.

That's right, pants. Spallanzani was a serious natural philosopher (what we'd now call a scientist); he was also very suspicious of a notion common in his day: that life sometimes spontaneously generates from nonlife.

People noticed that when meat was left on a table for long enough, baby flies appeared. The beef, it was said, birthed the flies. No one knew how. It just happened — poof! Decomposition — even of inorganic things — was key. Put some wheat husks on the ground, mix them with odoriferous human underwear, wait 21 days, and the sweat and the wheat would combine to generate (spontaneously) a mouse. This was a common belief.

Spallanzani thought otherwise. He believed that, in higher animals, not only was an egg necessary, but sperm was also required. He believed that life came only from life, not nonlife. Scholars had seen sperm, those wiggly things produced by the sex organ in a flush of solution. Obviously the spermy suspension had some purpose ...

... but what? So Spallanzani came up with this test.

He acquired a bunch of frogs, males and females. He separated them, and then, for the males, he designed what historians describe as "tight taffeta pants." I'm not sure exactly what they looked like. In some translations, the Italian reads as "short pants," so they might have looked like this ...

Or maybe like this ...

The pants were then fitted on the males, who, now dressed, were released. Their job, Spallanzani wrote, was to "seek [a] female with equal eagerness and perform, as well as they can, the act of generation."

But with pants on, it wasn't easy.

They got excited, with released sperm staining their garments, but the heavier, wiggly spermatozoa didn't get through.

Spallanzani, of course, had a control group (naked frogs who showered the eggs), and those eggs quickly began to develop, eventually producing tadpoles. But the bepanted frogs?

They begat no children. The tight pants had clearly removed a key ingredient. Sperm, it seemed, was necessary in these unions. Tadpoles, clearly, didn't spontaneously generate (and didn't, as another group thought, grow from teeny premade versions of themselves). No, Spallanzani proved that baby frogs come from two parents; and while he didn't get the mechanics exactly right, and while he went a little overboard fashionwise with his pant-sized Trojans — Spallanzani had made a major discovery.

To this day, there is a statue in Scandiano , Italy, of Spallanzani holding a magnifying glass in one hand and a frog in the other. The frog, I'm sorry to say, is not wearing pants. Spallanzani is, but you'd expect that. If it had been my sculpture, that frog would have been dressed. I think a teaching moment was missed here, big time. "Mama," I can hear kids all over town asking, "Perché quella rana porta i pantaloni (Why is that frog wearing pants)?" "Ummm," the mother would say, "ask your father."

The second experiment (which I'll get to in my next post ) features John James Audubon — the great American bird illustrator — and some colleagues, who prepared a delicious lunch for vultures one day. It was a dead sheep, pre-opened and ready for eating. Only this particular sheep wasn't edible. That's because it was a drawing — a drawing sitting on top of real meat. Come back, and I'll explain what happened and why.

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3.1 Spontaneous Generation
Describe the theory of spontaneous generation and some of the arguments used to support it. Explain how the experiments of Redi and Spallanzani challenged the theory of spontaneous generation. Disproving Spontaneous Generation. The debate over spontaneous generation continued well into the 19th century, with scientists serving as proponents of ...
2.1 Spontaneous Generation
Describe the theory of spontaneous generation and some of the arguments used to support it. Explain how the experiments of Redi and Spallanzani challenged the theory of spontaneous generation. Disproving Spontaneous Generation. The debate over spontaneous generation continued well into the 19th century, with scientists serving as proponents of ...
Spontaneous Generation
Spallanzani's Experiment. An Italian scientist, Lazzaro Spallanzani combined both experiments of Needham and Redi and constructed his own experiment. ... He suggested that "abiogenesis" be used to describe the process of spontaneous generation, while "biogenesis" should refer to the principle that life arises from pre-existing life ...
Spontaneous generation
Spontaneous generation was taken as scientific fact for two millennia. Though challenged in the 17th and 18th centuries by the experiments of the Italian biologists Francesco Redi and Lazzaro Spallanzani, it was not discredited until the work of the French chemist Louis Pasteur and the Irish physicist John Tyndall in the mid-19th century.
3.1 Spontaneous Generation
Describe the theory of spontaneous generation and some of the arguments used to support it. Explain how the experiments of Redi and Spallanzani challenged the theory of spontaneous generation. Disproving Spontaneous Generation. The debate over spontaneous generation continued well into the 19th century, with scientists serving as proponents of ...
1.2 Spontaneous Generation
Describe the theory of spontaneous generation and some of the arguments used to support it. Explain how the experiments of Redi and Spallanzani challenged the theory of spontaneous generation. Disproving Spontaneous Generation. The debate over spontaneous generation continued well into the 19th century, with scientists serving as proponents of ...
Spontaneous Generation
Prominent scientists designed experiments and argued both in support of (John Needham) and against (Lazzaro Spallanzani) spontaneous generation. Louis Pasteur is credited with conclusively disproving the theory of spontaneous generation with his famous swan-neck flask experiment. He subsequently proposed that "life only comes from life."
Lazzaro Spallanzani
Lazzaro Spallanzani (born Jan. 12, 1729, Modena, Duchy of Modena—died 1799, Pavia, Cisalpine Republic) was an Italian physiologist who made important contributions to the experimental study of bodily functions and animal reproduction. His investigations into the development of microscopic life in nutrient culture solutions paved the way for ...
Lazzaro Spallanzani (1729-1799)
Lazzaro Spallanzani's imaginative application of experimental methods, mastery of microscopy, and wide interests led him to significant contributions in natural history, experimental biology, and physiology. His detailed and thoughtful observations illuminated a broad spectrum of problems ranging from regeneration to the genesis of thunderclouds.
Spallanzani, Lazzaro
Lazzaro Spallanzani. 1729-1799. Italian Physiologist. Lazzaro Spallanzani was an Italian physiologist who extensively studied animal biology and reproduction.He is probably most famous for his experiments that helped to disprove the theory of spontaneous generation, which helped to pave the way for future research by Louis Pasteur (1822-1895). Spallanzani was a creative and endlessly ...
Spontaneous Generation
The prize was claimed in 1864 by Louis Pasteur, as he published the results of an experiment he did to disproved spontaneous generation in these microscopic organisms. Observation(s): From Needham's and Spallanzani's experiments, it was known that soup that was exposed to the air spoiled — bacteria grew in it. Containers of soup that had been ...
Spontaneous Generation Theory
Early Experiments. Franceso Redi. Pier Antonio Micheli. John Needham. Lazzaro Spallanzani. Disproving the Theory. Louis Pasteur. John Tyndall. Frequently Asked Questions. Spontaneous generation theory is an archaic scientific theory which stated that living organisms could arise from nonliving matter and that such a process was regular in nature.
Origin of Life: Spontaneous Generation
Spallanzani's Experiment. Lazzaro Spallanzani, also an Italian scientist, reviewed both Redi's and Needham's data and experimental design and concluded that perhaps Needham's heating of the bottle did not kill everything inside. He constructed his own experiment by placing broth in each of two separate bottles, boiling the broth in both bottles ...
The Theory of Biogenesis
Spallanzani's Experiment. Source: Emaze. In 1768, Lazzaro Spallanzani suspected microscopic biogenesis and wanted to prove it experimentally. He boiled meat broth in a sealed container to avoid contamination. However, he was faced with a problem- upon heating a sealed container, the air inside would expand massively and would shatter the ...
Is Spontaneous Generation Real?
Spallanzani Experiment . In 1765, Italian biologist and priest Lazzaro Spallanzani, set out to demonstrate that microbes do not spontaneously generate. He contended that microbes are capable of moving through the air. Spallanzani believed that microbes appeared in Needham's experiment because the broth had been exposed to air after boiling but ...
Experiments in support and against Spontaneous Generation
Experiments in support and against Spontaneous Generation. January 30, 2022 by Sagar Aryal. Edited By: Sagar Aryal. Spontaneous generation is an obsolete theory which states that living organisms can originate from inanimate objects. The theory believed that dust created fleas, maggots arose from rotting meat, and bread or wheat left in a dark ...
3.1
Lazzaro Spallanzani (1729-1799) did not agree with Needham's conclusions, however, and performed hundreds of carefully executed experiments using heated broth.3 As in Needham's experiment, broth in sealed jars and unsealed jars was infused with plant and animal matter. Spallanzani's results contradicted the findings of Needham: Heated ...
Two Glorious Science Experiments: One About Sex, The Other About ...
No, Spallanzani proved that baby frogs come from two parents; and while he didn't get the mechanics exactly right, and while he went a little overboard fashionwise with his pant-sized Trojans ...

3.1 Spontaneous Generation

Clinical Focus

The Theory of Spontaneous Generation

Check Your Understanding

Disproving Spontaneous Generation

2.1 Spontaneous Generation

The Theory of Spontaneous Generation

Disproving Spontaneous Generation

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Spontaneous Generation – Definition, Experiments, Importance

Definition of Spontaneous Generation

Experiments on Spontaneous Generation Theory

Redi’s Experiment

John Needham’s Experiment

Examples of Spontaneous Generation

Spontaneous generation vs. Modern abiogenesis

Spontaneous generation vs. Biogenesis

Equivocal vs. Univocal generation

1. What is spontaneous generation and who disproved the theory?

2. Are abiogenesis and spontaneous generation the same?

4. What is meant by the idea of spontaneous generation?

7. Is spontaneous generation true?

10. Who disproved spontaneous generation?

13. What is spontaneous generation history?

3.1 Spontaneous Generation

CLINICAL FOCUS: Part 1

The Theory of Spontaneous Generation

Disproving Spontaneous Generation

Multiple Choice

Critical Thinking

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3 1.2 Spontaneous Generation

CLINICAL FOCUS: Part 1

The Theory of Spontaneous Generation

Disproving Spontaneous Generation

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Unit 1: An Invisible World

The Theory of Spontaneous Generation

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Macroscopic Biogenesis: Francesco Redi’s Experiment

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Experiments in support and against Spontaneous Generation