Question

Describe the ‘theory” of Spontaneous Generation and how Francesco Redi and Louis Pasteur disproved the theory, using the process of scientific method

Answer 1

Answer- According to theory of spontanious generation, the living organisms originates spontaniously from non-living material.

Experiment of Frencesco Redi-

• First if all he placed meat in an opened glass jar, and after a few days he had observed the maggots (fly larvae) coming out of meat.
• Then he took another glass jar and placed meat in it and covered it by the help of muslin cloth.
• He observed that mggots did'nt appear from covered jar.

Thus he concluded that, the maggots did not appear from meat spontaniously but they arises only from eggs of fly which can only be laid in uncovered jars.

Experiment of Louis Pasteur-

He performed several experiments by which the spontaneous generation of microbes was disproved. The simplest and most sophisticated one was with the use of a swan-neck flask. He performed experiment in following steps-

• Pasteur prepared a nutrient broth similar to the broth which can support microbial growth.
• Then  he placed equal amounts of the broth into two long-necked flasks.
• He left one flask with a straight neck. The other he bent to form an "S" shape.
• Then he boiled the broth in each flask to kill any living matter in the liquid.
• The sterile broths were then left to sit, at room temperature and exposed to the air, in their open-mouthed flasks.
• After several weeks, Pasteur observed that the broth in the straight-neck flask have microbial contamination and appears cloudy, while the broth in the curved-neck flask had not changed.

• He concluded that germs in the air were able to enter down the straight-necked flask and contaminate the broth. The other flask, however, trapped germs in its curved neck,­ preventing them from reaching the broth, which never showed microbial growth or became cloudy.