Understanding:
• Cells can only be formed by division of pre-existing cells
The chemical processes that contributed to the initial formation of biological life required specific conditions to proceed
- This included a reducing atmosphere and high temperatures (>100ºC) or electrical discharges to catalyse chemical reactions
These conditions do not commonly exist on modern Earth and hence living cells cannot arise independently by abiogenesis
- Instead, cells can only be formed by the division of pre-existing cells (biogenesis)
Application:
• Evidence from Pasteur’s experiments that spontaneous generation of cells and organisms does not now
occur on Earth
Biogenesis describes the principle that living things only arise from other living things by reproduction (not spontaneous generation)
- "Omne vivum ex vivo” – All life (is) from life
The law of biogenesis is largely attributed to Louis Pasteur, who demonstrated that emergent bacterial growth in nutrient broths was due to contamination by pre-existing cells
- Broths were stored in vessels that contained long tubings (swan neck ducts) that did not allow external dust particles to pass
- The broths were boiled to kill any micro-organisms present in the growth medium (sterilisation)
- Growth only occurred in the broth if the flask was broken open, exposing the contents to contaminants from the outside
- From this it was concluded that emergent bacterial growth came from external contaminants and did not spontaneously occur
Overview of Pasteur’s Experiment into Biogenesis
