Spontaneous Generation Theory and Biogenesis theory

Spontaneous Generation Theory Definition

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. 

In the earliest times, people had believed in spontaneous generation theory. But later this theory was proved wrong. Several experiments were conducted to disprove spontaneous generation.

In the 19th century, Louis Pasteur’s experiment and other experiments refuted this theory and supported biogenesis.

Experiments on Spontaneous Generation Theory

Aristotle

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

In 1668, an Italian scientist Francesco Redi conduct an experiment on a piece of fresh meat to disprove the spontaneous theory.

• Redi placed a piece of fresh meat in tow different jars.
• He left one jar open and the second one was covered with a cloth.
• After a few days, he observed that the open jar contained maggots whereas the covered jar contained no maggots.
• He also noticed that maggots were found on the exterior surface of the cloth, which was used to cover the jar.

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

Later, An England scientist, John Needham proved Redi’s experiment wrong by placing broth or gravy in a bottle and heated the bottle to kill the indie’s germs, then he sealed it. After a few days, he found life inside the bottle and announced that life is originated from nonliving cells ( In actuality, he did not heat it long enough to kill all the microbes). 

Spallanzani’s Experiment

An Italian scientist, Lazzaro Spallanzani combined both experiments of Needham and Redi and constructed his own experiment.

• Spallanzani conducted her experiment by placing broth in two different bottles.
• Then he boiled both broth inside the bottle.
• Then he sealed on the bottle and left open the second one.
• After a few days, he observed that the open bottle contains life was as the sealed bottle contain no life.
• Although his experiment was successful 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.  a strong rebuttal blunted his claims.

Pasteur’s Experiment

The French scientist, Louis Pasteur accept the challenge and conduct his experiment on spontaneous generation.

• He designed several bottles with S-curved necks or also known as gooseneck flask, which were oriented downward so gravity would prevent access by airborne foreign materials.
• Then he placed nutrient-enriched broth in one goose-neck bottle.
• Then he boiled the broth inside the bottle and kept it for one year in sealed condition.
• After one year he observed no life in the jar.
• Then he broke the top portion of the goose-neck bottle and directly exposed to the air.
• After a few days, he observed that the broth has contains life.
• He noticed that no life forms were observed in the broth until this obstacle was removed from the bottle, because air born particles and dust were trapped in the S-shaped neck of the bottle.
• He confirmed that the contamination came from life-forms in the air. From this experiment, he disproves the spontaneous generation theory.

John Tyndall

• In 1876, an English physicist John conduct an experiment to support the Pasteur’s experiment.
• He designed an apparatus to prove that air carries particulate matter.
• From his experiment, he proved that pure air is free of microorganisms. When this pure air is introduced into life-supporting media no microorganism was formed.

Biogenesis Definition

• Biogenesis is referred to as the living cells are originated from the nonliving cells.
• Ther term biogenesis also refers to biochemical processes of production in living organisms.
• The biogenesis theory was proved by Louis Pasteur, that living things come only from other living things life does not spontaneously arise from non-living material.
• An English physiologist and neurologistHenry, Charlton Bastian first coined the term biogenesis.
• An English biologist and anthropologist Thomas Henry Huxley first coined the term abiogenesis.

Questions On Spontaneous Generation

Reference

1. https://www.infoplease.com/math-science/biology/genetics-evolution/origin-of-life-spontaneous-generation
2. https://en.wikipedia.org/wiki/Swan_neck_flask
3. https://en.wikipedia.org/wiki/Spontaneous_generation
4. https://en.wikipedia.org/wiki/Biogenesis
5. https://www.biologyonline.com/dictionary/biogenesis