Which experiment provided evidence that contradicted the original cell theory by demonstrating that cells can arise only from pre-existing cells?

• A. Hershey and Chase's bacteriophage experiment
• B. Frederick Griffith's transformation experiment
• C. Gregor Mendel's pea plant experiments
• D. Louis Pasteur's swan-neck flask experiment

Answer: (D)

Verified step by step guidance

1. Understand the original cell theory: It initially proposed that cells arise spontaneously, which was later contradicted by evidence showing that cells arise only from pre-existing cells.
2. Review Louis Pasteur's swan-neck flask experiment: Pasteur designed an experiment to test the idea of spontaneous generation by using flasks with long, curved necks that prevented airborne microorganisms from entering the broth.
3. Examine the setup of the experiment: Pasteur boiled the broth in the flasks to kill any existing microorganisms, then left the flasks exposed to air but protected by the swan-neck design.
4. Analyze the results: The broth in the swan-neck flasks remained free of microbial growth, demonstrating that microorganisms did not spontaneously generate but came from pre-existing cells when the neck was removed or broken.
5. Conclude the significance: Pasteur's experiment provided strong evidence that contradicted spontaneous generation and supported the idea that cells arise only from pre-existing cells, refining the cell theory.