Why did Pasteur design swan-necked flasks in his experiments on spontaneous generation?

• A. The neck excluded oxygen from entering the flask.
• B. The neck stopped microorganisms in the air from contaminating the contents of the flask.
• C. The neck excluded flies and maggots from entering the flask.
• D. The neck served as a handle when heating the flask.
• E. The neck prevented Pasteur from contaminating his sample by sneezing on it.

Answer: (B)

Verified step by step guidance

1. Understand the historical context: Louis Pasteur conducted experiments to disprove the theory of spontaneous generation, which suggested that life could arise from non-living matter.
2. Recognize the purpose of the swan-necked flask design: The unique shape of the flask was intended to prevent airborne microorganisms from reaching the nutrient-rich broth inside, while still allowing air to enter.
3. Analyze how the design works: The swan-necked flask has a long, curved neck that traps dust and microorganisms in the bend, preventing them from contaminating the broth.
4. Consider the implications of the experiment: By showing that no microbial growth occurred in the broth unless the flask was tilted to allow contact with the trapped particles, Pasteur demonstrated that microorganisms come from other microorganisms, not spontaneously.
5. Reflect on the impact of Pasteur's findings: His experiments were pivotal in advancing the germ theory of disease and disproving spontaneous generation, leading to improved sterilization and hygiene practices.