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. 2. All existing cells are produced by other living cells. 3. The cell is the most basic unit of life.
Cell Theory Early studies led to the development of the cell theory. Early studies led to the development of the cell theory. – The Cell theory has three.
Dec 18, 2015
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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.2. All existing cells are produced by other living
cells.3. The cell is the most basic unit of life.
All cells share certain characteristics.
• Cells tend to be microscopic.
Bacterium(colored SEM; magnification 8800x)
All cells share certain characteristics.
• Cells tend to be microscopic.
• All cells are enclosed by a membrane.
Bacterium(colored SEM; magnification 8800x)
cell membrane
All cells share certain characteristics.
• Cells tend to be microscopic.
• All cells are enclosed by a membrane.
• All cells are filled with cytoplasm.
Bacterium(colored SEM; magnification 8800x)
cell membrane
cytoplasm
• There are two cell types: eukaryotic cells and prokaryotic cells.
– Eukaryotic cells have a nucleus.
nucleus
cell membrane
• There are two cell types: eukaryotic cells and prokaryotic cells.
– Eukaryotic cells have a nucleus.
– Eukaryotic cells have membrane bound organelles
nucleus
cell membrane
organelles
• There are two cell types: eukaryotic cells and prokaryotic cells.
– Prokaryotic cells do not have a nucleus.nucleus
cell membrane
organelles
• There are two cell types: eukaryotic cells and prokaryotic cells.
– Prokaryotic cells do not have a nucleus.
– Prokaryotic cells do not have membrane-bound organelles.
nucleus
cell membrane
organelles
cytoplasm
Evolution
Most biologists believe prokaryotes evolved before eukaryotes for two reasons:
1. Prokaryotes tend to be much smaller
2. Prokaryotes are much less complex
Viruses
Viruses• Viruses are not considered living
things.
Viruses•They have no cell membrane
•Viruses are wrapped in a protein coat
Viruses•They have no cell membrane
•They have no cytoplasm
Viruses•They have no cell membrane
•They have no cytoplasm
•They depend on their host for energy
Viruses•They have no cell membrane
•They have no cytoplasm
•They depend on their host for energy
•They depend on their host for reproduction
Viruses
Characteristics of life
1. Need energy for life processes.
2. The ability to reproduce
3. Responds to the environment.
4. Passes heritable traits through DNA.
Characteristics of Viruses
1. Must depend on host.
2. Must depend on host.
3. Does not respond to the environment.
4. Passes heritable traits through DNA or RNA
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