Download Discovery of Cells PPT - Ms. George`s Science Class

The Discovery of Cells
How some very smart scientists
invented microscopes,
which led to the discovery of cells
and the development of the
Cell Theory and the Germ Theory
All Living Things:
Are made up of cells
1.
Cell: the basic unit of living things that can
perform all the processes associated with life
Sense and Respond to Change in their
Environment
Reproduce
Have DNA
Obtain and Use Energy
2.
3.
4.
5.
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6.
Energy: ability to make things move or change
Grow and Develop
The Invention of Microscopes
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During the 1st century AD (year 100), glass was
invented and the Romans were looking through
the glass and testing it. They experimented with
different shapes of clear glass and one of their
samples was thick in the middle and thin on the
edges.
They discovered that if you held one of these
lenses over an object, the object would look
larger.
These lenses were not used much until the end
of the 13th century when spectacle makers were
producing lenses to be worn as
eyeglasses.
Zaccharias and Hans Janssen
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Sometime around the year 1590, two Dutch spectacle
makers, Zaccharias Janssen and his father Hans
started experimenting with lenses.
They put several lenses in a
tube and made a very important
discovery.
The object near the end of the
tube appeared to be greatly enlarged,
much larger than any simple magnifying glass could
achieve by itself!
They had just invented the compound
microscope (a microscope that uses two or
more lenses).
Anthony van Leeuwenhoek
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Anthony van Leeuwenhoek of
Holland became very interested
in lenses while working with
magnifying glasses in a store.
He used the magnifying glass to
count threads in woven cloth.
He became so interested that he
learned how to make lenses.
He made small lenses with great
curvatures.
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Leeuwenhoek’s rounder
lenses produced greater
magnification, and he
created microscopes that
were able to magnify up to
270 times!
These more powerful
microscopes led to the
discovery that there were
many very small organisms
that did not belong in the
Animal or Plant Kingdoms.
Before this time, people did
not know that there were
organisms smaller than
plants or animals!
Anthony van Leeuwenhoek
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Leeuwenhoek used his microscope to
look at scrapings from his own teeth as
well as from teeth of 2 old men who had
NEVER BRUSHED THEIR TEETH!
The term “bacteria” didn’t exist yet, and
so he called the organisms he saw
“animalcules”
In his own words…
"I then most always saw, with great wonder, that in
the said matter there were many very little living
animalcules, very prettily a-moving. The biggest
sort. . . had a very strong and swift motion, and
shot through the water (or spittle) like a pike does
through the water. The second sort. . . oft-times
spun round like a top. . . and these were far more
in number." In the mouth of one of the old men,
Leeuwenhoek found "an unbelievably great
company of living animalcules, a-swimming more
nimbly than any I had ever seen up to this time.
The biggest sort. . . bent their body into curves in
going forwards. . . Moreover, the other
animalcules were in such enormous numbers,
that all the water. . . seemed to be alive."
Anthony van Leeuwenhoek
September 17, 1683
Leeuwenhoek’s observations
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What Anthony van
Leeuwenhoek observed
included bacteria, yeast,
blood cells and many tiny
animals (protozoans)
swimming about in a drop
of water.
From his great
contributions, many
discoveries and research
papers, Anthony
Leeuwenhoek has since
been called the "Father of
Microscopy".
Robert Hooke
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Robert Hooke, an Englishman
who is sometimes called the
“English Father of
Microscopy”, also spent much
of his life working with
microscopes and improved
their design and capabilities.
He used a microscope that
magnified 30 times (30X) to
look at the bark of a cork tree.
Hooke’s
Sketch
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In the thin slice of
cork, Hooke saw
small areas that
looked like small
empty rooms, or
cells.
 What he actually saw
was the remaining
dead walls of plant
cells, not living cells.
Cork Tree Bark
Cork Tree
Other Key Contributors
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In 1838, German botanist Matthias Schleiden
used the microscope to study parts of plants
 He concluded that plants were made of cells.
 One year later, scientist Theodor Schwann,
concluded that all animals are made of cells.
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Together, Schleiden and Schwann
concluded that all living things are made
of cells.
Key contributors, continued
In the mid-1850’s, doctor Rudolph
Virchow stated that new cells do not
form on their own. All cells come
from other living cells.
 Virchow’s discovery, combined with
Schleiden and Schwann’s findings,
led to what we know today as…
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The Cell Theory
The Cell Theory
All living organisms are made of one
or more cells.
2. All cells are the basic units of
structure and function in all
organisms.
1.
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Structure: how something is built—its form
 Function: what something does—its job
3.
All cells come from previously
existing cells.
1. All living organisms are made
of one or more cells
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Living organisms can
be single-celled, like
these bacteria
 Or multi-cellular, like
the tapir, swordfish,
and tree.
2. Cells are the basic units of
structure and function in all
organisms
Examples:
 Bone cells, nerve cells (neurons),
blood cells, skin cells, muscle cells,
etc.
 Leaf cells, root cells, flower cells,
cells that make up a plant’s
transport tissues (xylem and
phloem)
Blood
Cells
Skin Cells
Neuron
Bone Cells
Rod & Cone
Eye Cells
3. All cells come
from previously
existing cells
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Cells come from
other cells when
they divide through
a process called
Mitosis.
2 Identical Daughter Cells
1 cell
Knowing about cells is useful!
Back in the 1800’s, there
were no refrigerators like
we have today.
 Food often spoiled and
milk went sour.
 A French scientist,
Louis Pasteur, proved
that microscopic
organisms led to food
spoilage and disease.
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Pasteurization
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Pasteur noticed that spoiled
beverages contained large
amounts of bacteria.
He created a process in
which heat was used to kill
the bacteria, thereby keeping
beverages fresh longer.
This process, called
pasteurization, is still used
today. Check your milk cartons at
lunch and at home for the word
“pasteurized”
Germ Theory
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Pasteur is the most famous of the many
scientists who developed the Germ Theory
The Germ Theory, in simplest terms, states
that many diseases are caused by
microorganisms.
Over time, acceptance of this theory led to
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doctors washing their hands before surgery
 development of medicines like antibiotics
Main Idea
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The following sentences are all facts from
today’s lesson. Only one sentence below
represents the main idea of today’s power
point. Circle the main idea sentence.
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Our bodies are made of cells
 Scientific knowledge develops over time, often
with contributions from more than one scientist.
 Pasteurization is important for keeping our
food safe.
When scientists announce their discoveries
they refer to the following quote:
“If I have seen a little further it is by
standing on the shoulders of Giants”
Isaac Newton (in a letter to Robert Hooke dated February 5, 1676)
How does this quote apply to Louis Pasteur
and his discovery?