Theories about the evolution of organic molecules

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
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 1668.
 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
It was almost another 100 years,
1862, before French scientist Louis
Pasteur convinced people that the
spontaneous generation did not
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