Download Beyond the light microscope

Student objectives:
•To understand how the development of the
microscope has improved our understanding
of cells and allows for continued research.
•To explain the work of key scientists in
developing the Cell Theory.
The Microscope A Short History
Janssen – Lenses in a Tube
Around 1590, two Dutch
spectacle makers, Hans Janssen
and his son Zacharias, reputedly
discovered that nearby objects
appear greatly enlarged if they
are viewed through several lenses
in a tube.
In 1609, the Italian inventor and
scientist Galileo Galilei developed his
first occhiolino or compound
microscope.
This included both a convex and a
concave lens.
Robert Hooke – the English Microscopist
In the mid-17th century, the
English microscopist Robert
Hooke made a series of
improvements upon Galileo’s
design.
Hooke noticed that samples of
cork were made up of
microscopic box-like units.
He called them cells. We now
know that there are thousands
of different types of cells in
animals and plants.
Leeuwenhoek – the Father of Microbiology
The Dutch scientist, Anton van
Leeuwenhoek, developed new
methods for grinding and
polishing tiny lenses about ten
years after Hooke’s discoveries.
These lenses could magnify
objects up to 270 times their
normal size.
Leeuwenhoek was the first to be able to see and describe
bacteria, yeast and blood cells.
He also saw and described microscopic plants and animals,
which he called “animalcules”.
Microscope improvements
• In the 1850s, German engineer Carl Zeiss began
making refinements to the lenses he used in the
microscopes he manufactured.
• Ernst Abbe was hired by Zeiss to improve the
manufacturing process of optical instruments, which
back then was largely based on trial and error. Abbe
carried out theoretical studies of optical principles,
improving the understanding of the optical quality of a
microscope.
• In the 1880s, Zeiss hired glass specialist Otto Schott,
who conducted research on optical glass, greatly
contributing to the improvement of the optical quality
of the microscope.
Beyond the light microscope
• 1931 - Ernst Ruska starts to build the first electron
microscope. This microscope can view objects as
small as the diameter of an atom and is able to
magnify objects up to 1 million times. However, no
living specimen can survive under the microscope’s
high vacuum, so the ever-changing movements of a
living cell cannot be seen.
• 1981 – Gerd Binnig and Heinrich Rohrer invented the scanning
tunnelling microscope that gives three-dimensional images of
objects down to the atomic level. This is the strongest microscope
to date.
THE CELL THEORY
and the scientists
who developed it
1665 - Robert Hooke was the first person to
use the term CELLS when he looked at
thin slices of cork.
Cork is dead plant tissue.
Hooke’s drawing
of cells
Cork cells
(stained)
Anton van Leeuwenhoek
1670 - Anton van
Leeuwenhoek looks at pond
water and becomes the first
person to see living cells
with a simple microscope.
1833 - Robert Brown was
the first to note that all
plant cells contained a small
round mass that he called
the nucleus.
He also suggested that this
structure was the centre of
cellular creation.
1838
- Matthias Schleiden:
German botanist that
suggests that all plant
tissues are composed of
cells, and that cells are
the basic building blocks
of all plants.
1839 – Theodor Schwann:
a German botanist who
reached the conclusion
that not only plants, but
animal tissue as well is
composed of cells.
1855 - Rudolf Virchow: a German
physiologist/physician/pathologist states
that all cells develop only from existing cells.
Student Activities:
•Complete the worksheet on the timeline of
microscope development
•Complete worksheet questions on the Cell
Theory.