BIOL2421 Chapters 3,7,10-F2024 (1)

Chapter 3: The Cell

3.1 Origin of Life

• Spontaneous Generation: Theory that life can arise from nonliving matter (abiogenesis).

  • Coined by Aristotle as "pneuma" or "vital heat".

Spontaneous Generation Debates

• Jan Baptista van Helmont (17th Century): Proposed mice came from rags and wheat.

• Francesco Redi (1668): Demonstrated maggots come from fly eggs in meat, disproving S.G. for larger organisms.

• Lazzaro Spallanzani (1760s): Suggested microbes in the air; killed by boiling and hermetically sealing flasks.

  • John Needham (1740s): Boiled plant material; sealed flasks still grew microbes—debated.

Challenges to Spontaneous Generation

• Experiments showed that with dust and particles trapped, no contamination occurred.

• "Omne vivum ex vivo" (