CHAPTER 1
Development of Cell Theory
IMPORTANCE OF THE CELL
 The cell is the basis for life.
 The human body is made up of 100 trillion cells all working
together.
 Cells are specialized to perform different tasks, i.e. bone cells,
muscle cells, nerve cells etc...
 ~100 years ago people wrongly believed in abiogenesis (living
things from non-living items)
A BRIEF HISTORY… OK,
NOT SO BRIEF…
Up to ~100 years ago, the science world believed
that non-living things had the ability (given the right
circumstances) to change into living things.
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Eels made from ooze in ponds
Frogs and fish from clouds in the sky
Maggots from rotting meat
Mice from sweaty shirt & straw
THE PARADIGM SHIFT
 This seemingly ridiculous idea is known as spontaneous generation: the
belief that living things are created from non-living things.
 Most scientists and general public firmly believed this to be true,
however, there were a few scientists who questioned how this could happen.
They tried to prove spontaneous generation to be false but noone would
believe them. Something was always “wrong” with their experiments to
discredit them.
 Then, Francesco Redi devised an experiment that could not fail.
 With a series of glass jars, wire mesh and rotten meat he proved
once and for all that living things (flies) were responsible for the
appearance of maggots, not a non-living entity (air).
 After Redi’s experiment spontaneous generation was dropped and the
theory of biogenesis prevailed.
 Biogenesis: living things are created from other living things of the
same kind.
HISTORY OF MICROSCOPES
 Magnification (making things appear bigger) has been used for
thousands of years. From the time of the Egyptians (1000BC)
glass lenses have been used to see the microscopic world.
 From increasing technology and resolution “cells” were
discovered and led to the development of modern cell theory.
HISTORY
Late 1600’s
-Robert Hooke- looked at cork under
microscope, coined the term “cells”
-Leeuwonhoek- saw living cells including
bacteria
1824- Henry Dutrochet- all living things made of
cells
1831- nucleus first named
1855- Rudolph Virchous- stated all cells arise from
pre-existing cells
CELL THEORY
1)
All organisms are made of cells
2)
All cells arise from pre-existing cells
3)
The cell is the basic unit of life