Cell Theory
Unit 2: Intro to Microscopic World
Cell Theory
• All organisms are make of cells
• First ideas came from Schleiden and Schwann
and have remained similar since 1939
First Founders of Cell Theory
Plant and Animal Cells
First Founders of Cell Theory
Early Ideas of Cell Theory
• The cell is the unit of structure, physiology,
and organization of living things
• The cell retains a dual existence as a distinct
entity and building block in the construction
of organisms
• Cells form by free-cell formation, similar to the
formation of crystals
• Cells form by free-cell formation, similar to the
formation of crystals
Was replaced by Virchow’s “All cells only arise
from pre-existing cells”
Modern Cell Theory
• Cells contain hereditary information which is
passed from cell to cell during cell division
• All cells are basically the same in chemical
composition
• All energy flow of life occurs within cells
Go Back a Few Steps
• 1663 – Robert Hooke
– Coined the term “cell” from the Latin word
“cellula” which means “small compartment”
Go Back a Few Steps
• 1673 – Anton van Leeuwenhoek
– First person to observe bacteria and protozoa (animallike protists)
– Made over 500 microscopes…but only 10 are still used
today….and they were more like a magnifying glass
(but they were powerful – 200x).
– Unfortunately, he didn’t record how to make them so
well…so there were no new microscopes for over one
hundred years.
– Discovered blood cells and the first to see living sperm
in animals
Giardia lamblia
Go Back a Few Steps
• Lorenz Oken
– May have been the first to come up with cell
theory as he stated: “All living organisms originate
from and consist of cells”
Go Back a Few Steps
• Robert Brown
– Discovered the nucleus – others had seen it, but
he was the first to recognize its existence and give
it a name
– The nucleus was found in other plant species and
even in pollen
– Schleiden used and gave credit to Brown’s
discoveries
Schwann and Schleiden
• Schwann was looking at animal cells and
realized that they were similar to plant cells –
especially the nucleus.
• They both found that the nuclei were
separated about the same distance
throughout the tissue. In some case, they
were even divided by a wall of a
compartment.
Recap: Who Did What?
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•
•
•
•
•
Hooke?
Van Leeuwenhoek?
Oken?
Brown?
Schleiden?
Schwann?