Unit B: Cells and Systems
Topic 2: The Microscope and
Microscopic Organisms
History
• First microscopes invented by Anton van
Leewonhoek, in 1600s Holland, using
small magnifying lenses.
• Leewonhoek’s microscopes could see up
to 300X.
• He used his microscopes to study single
celled organisms. He called these
organisms animalcules.
Robert Hooke
• Lived at same time as Leeuwenhoek.
• English
• Studied the cells of cork trees. He called
them cellulae, which meant little rooms.
This is where we get the term cells.
Cell Theory
• Is a theory made up of two points:
• 1. All living things are either cells (eg.
bacteria), or made up of cells (eg.
mushrooms).
• 2. Cells are the basic units of structure and
function of life.
Microscopes Today
• Two main types of microscopes today:
• 1. Compound light microscopes: made up of two
lenses. Have a max. magnification of 2000X.
Cannot see the smaller structures in cells.
• 2. Electron Microscopes – bounces beams of
electrons off sample. The beam is then sent to a
TV or photo plate providing a greatly magnified
image. The max. magnification is 2 000 000X.
The downside with electron microscopes is that
they kill living specimens so dead ones are
used.
Field of View
• Amount of area you can see with a
microscope at a set magnification.
• Calculated in two parts:
• 1. Measure actual field of view on low
power.
• 2. FoV = Low Power FoV*LowPower Mag/
High Power Mag
Microscopic Organisms and
How They Move
• Example: Paramecium and
Cilia
• Paramecia move by having
hair-like projections around the
cell wave in the same
direction, propelling it forward
like little oars.
• Example: Chlamydomonas
and flagella
• Chlamydomonas have two
tails that they whip around to
help them move. Sperm cells
in animals also have flagella to
help them move.
Amoeba and the False Foot
• The amoeba is a
single-celled predator
which preys on other
unicellular organisms.
• It moves by changing
its shape and pushing
part of its membrane
forward and letting
the rest of the cell
catch up.