Cell Discovery &
Cell Theory
It all started with an invention….
 The first microscope
– Zacharias Jansen, 1595,
Middleburg, Holland
– It launched great leaps
in Astronomy and
Biology.
– Some of the first great
observations with it were
made by…
Robert Hooke (1635-1703)
– Designed microscopes
– Discovered and documented
the first “cells” in 1665
• Named them after the cells in
which a monk sleeps.
From: http://www.ucmp.berkeley.edu/history/hooke.html
Robert Hooke (1635-1703)
Released book of
detailed drawings
and observations:
Micrographia, 1665
Hooke had a life-long rivalry with Sir Isaac Newton.
Newton worked hard to destroy his reputation during and
after his death. Much of Hooke’s work was destroyed –
even his gravesite is still unknown.
Hooke’s drawing of a flea from: http://www.rod.beavon.clara.net/micro1.htm
From the Museum of Natural History website:
http://www.natmedmuse.afip.org/explore/micro/hooke.html http://micro.magnet.fsu.edu/optics/timeline/people/hooke.html
Antony van Leeuwenhoek
(1632-1723)
 A tradesman from Holland
who became fascinated with
Hooke’s book
 Discovered bacteria, freeliving protists, sperm cells,
blood cells, nematodes, etc.
 Became an expert lens grinder and made
over 500 simple microscopes
 Acute eyesight and lens grinding skill let him
build microscopes that were capable of 200X
magnification
Cell Theory
 1838 Mattias Schleiden stated that all plant
tissues consisted of cells
 1839 Theodore Schwann stated that all
animal tissues consisted of cells
 Each conjectured that there was a nucleus
 1858 Rudolf Virchow combined the two ideas
and added that all cells come from preexisting cells, formulating the Cell Theory
Rudolf Virchow
1858
Cell Theory
 All living things are
composed of one or more
cells
 In organisms, cells are the
basic units of structure and
function.
 All cells are produced only
from existing cells.
Modern Microscopes
 Some of the light microscopes here are capable of
1000x magnification.
– That is about the limit of a light microscope’s magnification
without losing clarity (called Resolving Power).
• Due to the width of visible light’s wavelength
 The electron microscope was introduced in the 1950s
and uses the wavelength of electrons to increase the
resolving power by 100x.
– Approx. 100,000x magnification!!
– Cell Biology advanced rapidly as cellular organelles were
clearly seen for the first time.
Resolving
Power
Modern Microscopes
Transmission Electron
Microscope (TEM)
magnifies a slice of a
sample.
(Rabbit trachea cilia)
Scanning Electron
Microscope (SEM)
shows 3D image of the
Rabbit trachea cilia
A modern
TEM
Fruit fly with four eyes under an
SEM