Transcript The Cell Theory

Discovery of Cells
•Most cells are so
tiny that they are
not visible to the
naked eye. So how
did we find out that
cells are the basic
unit of living things?
•What would make
someone think that
a rabbit or a tree or
a person is made
up of tiny parts that
cannot be seen?
•There is a word that
describes
something that to
small to see with
the unaided eye.
Who knows the
name of the term?
•Microscopicextremely small;
invisible without
the use of a
microscope
•Actually, the first
person to see
cells was not
even looking
them.
• In 1665, a British
scientist named
Robert Hooke was
trying to find
something interesting
that he could show to
other scientist at a
meeting.
•Robert Hooke- A
British scientist
who observed the
first cells in 1665,
by using a crude
•microscope of his
own invention to
examine a variety
of objects,
including a thin
piece of cork.
• Earlier, he had built a
crude microscope that
allowed him to look at a
very tiny objects. He
decided to look at a thin
piece of cork, a soft
plant tissue found in the
bark of trees.
•To his amazement,
the cork looked liked
hundreds of tiny
boxes. He named
these tiny boxes
cells. Which means
“little rooms” in latin.
Compound Microscope invented
by Robert Hooke
•Later he look at
slices of plants and
saw living things
that appeared to
have “juice” in them.
Those cells were
plant cells.
•He also looked at
feathers, fish
scales, and eyes of
horse flies. But he
spent most of his
time looking at
plants and fungi.
•Hooke thought
that cells were
found only in
those types of
organism and not
in animals.
• In 1672 a few years after
Hooke made his
observations, a dutch
merchant named Anton
van Leeuwenhoek used
one of his own handmade
microscopes to get a
closer look.
Simple microscope
• He was amazed to see
tiny creature swimming
around in pond scum. He
called the Animalcules,
which means “little
animals”. He also looked
at blood from different
animals.
• He scraped tartar off their
teeth and his own. He
was the first person to
see bacteria. He
discovered that in bread,
the yeast used to make it
were actually tiny
organisms.
•Anton van
Leeuwenhoek- Dutch
maker of microscopes, who
first to discover protists he
also observed red blood
cells, capillary systems,
and the life cycles of
insects.
The Cell Theory
•After Hooke saw the
first cork cells, almost
two centuries passed
before anyone realized
that cells are present in
all living things.
Things to ponder
Some Scientist began
to put these ideas
together and form a
theory about cells and
how they come into
existence.
•Theory- an idea of
or belief about
something arrived
at through
speculation or
conjecture (means to
guess)
Development of the cell
theory
• The cell theory was created by
different scientist who contributed
different parts over a period of time.
Let’s review each one and learn what
they did to develop the cell theory.
Robert Brown
• 1833: was a Scottish
botanist and
palaeobotanist who
made important
contributions to
botany. He
discovered the
nucleus in plant cells.
•Matthias Schleiden, a
German botanist, looked
at many slides of plant
tissues and in 1838 he
concluded that all plant
parts are made of cells.
Matthias Schleiden
• The next year,1839,
Theodore Schwann a
German physiologist
studied animals, stated that
all animals tissue are made
of cells. He used this to
develop the Cell Theory.
Theodor Schwann
Albrecht von Roelliker
•In 1840, He was the
first to observe that
sperm and eggs are
cells.
Carl Heinrich Braun
•1845 he was the
first to identify that
cells were the
basic unit of life.
• In 1858, Rudolf Virchow, A
German doctor saw that cells
could not develop from
anything except other cells.
That applies to diseased
tissue as well as to healthy
tissue. He said that diseased
cells come from healthy cells
of normal tissue.
• Virchow wrote the third
part of the cell theory
•All cells come
from existing
cells.
Rudolf Virchow
• The Cell Theory When Schleiden,
Virchow and Schwann proposed the
cell theory, cell biology research was
forever changed. The cell theory
states that:
1. All life forms are made from one or
more cells.
2. Cells only arise from pre-existing
cells.
3. The cell is the smallest form of life.
The time line
•UnicellularOrganisms that
are composed of
a single cell.
•MulticellularOrganisms that
are composed
of two or more
cells.