Theories about the evolution of organic molecules Year 11:Biology

 Describe two scientific theories relating to the evolution of the chemicals of life and discuss their significance in understanding the origin of life

Spontaneous generation  As far back as the time of Aristotle, humans thought that life spontaneously arises from non-living matter.  They saw maggots appear in rotting meat

 This concept of spontaneous generation was an accepted ‘fact’ and was not scientifically tested until  Francesco Redi an Italian physician, demonstrated that maggots in decaying meat came from eggs laid by flies

 About 100 years later Lazzaro Spallanzani showed that the microorganisms that appeared in broth came from the air  However his experimental technique was not sufficient to exclude spontaneous generation

 It was almost another 100 years, 1862, before French scientist Louis Pasteur convinced people that the spontaneous generation did not occur  DIAGRAMS

 Pasteur’s work and work of others such as Virchow established the statement that ‘all life comes from pre-existing life’  This presumed that first living thing or things had to arise somewhere, sometime, somehow