Spontaneous Generation
Pre-existing cells
- In 1852 Robert Remak made the conclusion that cells divided to form new cells, that is cells came from pre-existing cells
- His conclusion was reached after studying cells from chicken embryos
- This discovery is often attributed to Robert Virchow who in 1855 proposed the phrase omnis cellula e cellula (all cells come from cells)
- Prior to these announcements, it was believed that life arose spontaneously from non-living matter
NOS: Testing the general principles that underlie the natural world; the principle that cells only come from pre-existing cells needs to be verified
- Up until the 17th century, the consensus was that life was spontaneously generated (living organisms arose from non-living matter). This was believed due to:
- The lack of technology - microscopes were not extensively used
- Observations being made - Aristotle observing insects forming from dew or van Helmont observing a mouse appearing from a jar containing a sweaty shirt and wheat
- The idea supporting the cultural and religious beliefs of the time
- From the 17th century scientists such as Francesco Redi with his maggot and rotting meat experiment began collecting evidence to test and verify that life required life to exist
- However, it was Louis Pasteur's experiments involving swan-neck flasks that provided sufficient verification to convince scientists that cells could only come from pre-existing cells
- The universal acceptance that cells come from pre-existing cells also comes from the idea that :
- The highly complex ultrastructure of cells has not been able to be synthesised by humans
- All the known examples of growth are a result of cells dividing by mitosis or meiosis
- Although viruses have a much simpler structure, they can only be produced inside a host cell
- The universality of the genetic code suggests that all life evolved from the same original cells
- The translation of the 64 codons produces the same amino acids for nearly all organisms - although there are some rare minor variations that have likely arisen since the common origin of life
Experiments disproving spontaneous generation