The Development of the Cell Theory
ºObjective: Students will be expected to describe and explain the contributions of (a) Needham,
(b) Redi (c) Spallazani (d) and Pasteur in the debate between abiogenesis and
Biogenesis, two theories on how life arises.
Abiogenesis verses Biogenesis
early scientists thought that some living things could arise from nonliving things eg. frogs
could come from mud, flies from rotting meat, plants from the dried out mud of ponds, etc.
We call this process “abiogenesis” ( also called spontaneous generation). They did not
know about microscopic life such as bacteria. They did not yet know how many organisms
Biogenesis - the theory that states that only living things can give rise to other living things.
This is the theory we accept today as true.
many scientists, over time, contributed to the debate. Some were:
(see p. 7) in 334 BC, he stated that living organisms can arise spontaneously from
Francesco Redi (1660) -
(see p. 8, fig. 1.2) challenged the idea of abiogenesis. Many persons
believed that rotting meat produced maggots. Redi observed the
maggots longer than anyone else had and saw them enter a cocoon
stage and later emerge as flies. He recalled flies on the rotting meat
so set out to prove that maggots come from flies and are part of their
life cycle. He used proper scientific methods and performed a
controlled experiment in which one containers of fresh meat were
left opened and other containers of fresh meat were left covered.
Flies could not pitch on the covered meat and no maggots appeared
on that meat. Flies could land on the uncovered meat and in time
Many of those that believed in abiogenesis refused to accept his
John Needham (1748) -
(see p. 9, fig. 1.3) believed in abiogenesis. New research had shown
the existence of microorganisms in water and that boiling water
killed them. Needham boiled a meat broth. He placed the boiled
broth in two flasks.