Overview
This lecture covers the historical debate between spontaneous generation (life from non-life) and biogenesis (life from existing life), highlighting key experiments that disproved spontaneous generation.
Spontaneous Generation
- Spontaneous generation claimed that life could arise from non-living matter via a "vital force."
- Examples included beliefs that mice came from mud, insects from cow dung, and bees from buried animal carcasses.
Emergence of Biogenesis
- Biogenesis is the concept that all living things come from pre-existing living things.
- The theory of biogenesis replaced spontaneous generation after key experiments.
Key Experiments & Scientists
- Francisco Redi: Showed that maggots on meat came from flies, not meat itself, using open, sealed, and gauze-covered containers.
- John Needham: Supported spontaneous generation, but his sealed containers were actually porous, allowing microbial contamination.
- Lazzaro Spallanzani: Sealed glass flasks and boiled contents, preventing contamination and supporting biogenesis.
- Louis Pasteur: Used an S-shaped flask to show that microbes in air, not a vital force, caused contamination; his experiment conclusively disproved spontaneous generation.
Current Consensus
- The scientific community now accepts biogenesis: all life arises from existing life, not from non-living material.
Key Terms & Definitions
- Spontaneous Generation — The outdated belief that life can arise from non-living matter by a "vital force."
- Biogenesis — The scientific theory that all living things arise from other living things.
- Vital Force — Supposed mystical force responsible for spontaneous generation.
- S-shaped Flask — A special flask used by Pasteur allowing air but not microbes to enter, preventing contamination.
Action Items / Next Steps
- Review the key experiments and their significance for future discussions on microbiology.