Download HMH 3.1 Notes

3.1 Cell Theory
KEY CONCEPT Cells are the Basic unit of life.
3.1 Cell Theory
The cell theory grew out of the work of many scientists
and improvements in the microscope.
• Many scientists contributed to the cell theory.
Wacky History of Cells
3.1 Cell Theory
Hooke
1665: Hooke was the first to identify cells, and he
named them.
Fig. Hooke
observed the
cell walls of
dead plant cells
3.1 Cell Theory
The cell theory grew out of the work of many scientists
and improvements in the microscope.
• Many scientists contributed to the cell theory.
• More was learned about cells
as microscopes improved.
• The cell theory is a unifying
concept of biology.
Fig. Leeuwenhoek observed and
drew microscopic life, which he
called animalcules, in pond water
3.1 Cell Theory
Schleiden, Schwann and Virchow
1838: Schleiden was the first to note that plants are made of cells.
1839: Schwann concluded that all living things are made of cells.
1855: Virchow proposed that all cells come from other cells.
3.1 Cell Theory
Early studies led to the development of the cell theory.
• The Cell theory has three principles.
1. All organisms are made of cells.
3.1 Cell Theory
Early studies led to the development of the cell theory.
• The Cell theory has three principles.
2. All existing cells are produced by other living cells.
3.1 Cell Theory
Early studies led to the development of the cell theory.
• The Cell theory has three principles.
3. The cell is the most basic unit of life.
3.1 Cell Theory
Prokaryotic cells lack a nucleus and most internal
structures of eukaryotic cells.
• All cells share certain characteristics.
– Cells tend to be microscopic.
– All cells are enclosed
cell membrane
by a membrane.
– All cells are filled with
cytoplasm.
cytoplasm
Bacterium
(colored SEM; magnification 8800x)
3.1 Cell Theory
There are two cell types: eukaryotic cells and prokaryotic
cells.
• Eukaryotic cells have a
nucleus.
nucleus
• Prokaryotic cells do
not have membranebound organelles.
organelles
cell membrane
3.1 Cell Theory
There are two cell types: eukaryotic cells and prokaryotic
cells.
• Prokaryotic cells do not
have a nucleus.
nucleus
• Prokaryotic cells do not
have membrane-bound
organelles.
organelles
cell membrane
cytoplasm