Science 10: Unit 2: Biology
The Microscope
and Cell Theory
Science and Technology work together
Science and technology go hand in hand.
Scientific breakthroughs often allow for technical
advances.
These technological advances allow scientists to gather
new/more accurate evidence, leading to further
breakthroughs.
It is a cycle!
Science and Technology work together
A great example of technology leading to scientific
breakthrough is the microscope and its history of
development.
Leeuwenhoek’s Microscope
Leeuwenhoek designed one of the first microscopes to
help him explore the natural world.
It only had one lens and was basically a powerful
magnifying glass
He used his microscope to observe bacteria and yeast
Robert Hooke’s Microscope
Hooke built a microscope with two
lenses – known as a compound
microscope.
One set of lenses enlarges the object
and the other magnifies they image.
Hook invented the term cell while
looking at a sliver of cork. He though
that the cork cells looked like a
Monk’s cell in a monastery.
Maximum magnification of a modern
compound microscope is 1000x
Modern Microscopes: Electron Microscope
Electron microscopes pass a beam of
electrons through an object to form an
image.
This image can be viewed on a special
screen, or a picture can be taken
(called a micrograph)
Electron Microscopes can magnify
biological samples up to 100 000x!
However, they are expensive, and
cannot view living cells. You need to
prepare the specimens in plastic.
3 things affect what we see in a microscope
1) Magnification – How many times larger than normal the
image is
2) Contrast – how easily you can distinguish between light and
dark parts of the image -> High contrast is good!
3) Resolution – The ability to distinguish between two points
that are close together -> High resolution is good!
Contrast can be increased by adding stain
A stain is a dye that will darken some structures inside a
biological sample
Better microscopes lead to scientific
discovery
As microscopes became more
powerful, scientists were able to see
smaller objects.
One such object is the cell.
Studying the cell brought up
questions that challenged some of
the accepted theories at the time,
such as spontaneous generation.
Spontaneous generation was an
ancient theory, made famous by the
philosopher Aristotle, that life
emerged from non-living matter.
Disproving Spontaneous Generation
Disproving Spontaneous Generation
Disproving Spontaneous Generation
These experiments demonstrated 2 important ideas
1) Non-living objects cannot produce living objects
2) There are living organisms too small to see with the naked
eye
These ideas eventually lead to:
The Cell Theory
Cell Theory states that
1) All living things are made up of one or more cell
2) All life functions take place in cells; they are the smallest
unit of life
3) All cells are produced from other living cells
This theory finally put to bed the ancient idea that living matter
arises from non-living things.
The theory was formed out of the first observations of plant
cells under a microscope.