cell theory
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The Cell Theory A Timeline
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Late 1500’s
• Hans and Zacharias Janssen
• Dutch lens grinders, father and son • produced first compound microscope (2 lenses)
Late 1500’s
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Robert Hooke ( 1665)
• Used light microscope to look at thin slices of plant tissues -- cork
• Looked empty, like monk’s chamber
• Called tiny chambers
“cells”
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• Looked at pond water organisms
• First to see living microscopic organisms.
• Made careful sketches.
Anton von Leeuwenhoek (1673)
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Matthias Schleiden -- 1838
• German Botanist (studied plants)
• Viewed plant parts under a microscope
• Discovered that plant parts are made of cells
• He concluded:
“All plants are
made of cells.”
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Theodore Schwann -- 1839
• German scientist who studied animals - zoologist
• Saw that all animals he studied were cellular so concluded:
“All animals are made of cells.”
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Rudolf Virchow - 1855• German physician
who studied cell reproduction
• “Where a cell exists, there must have been a preexisting cell.”
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The Cell Theory• All living things are composed of one
or more cells.
• The cell is the basic unit of life in all living things.
• New cells are produced from existing cells.
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Cell Similarities• Cells come in many shapes and sizes with different
duties but …• All are surrounded with a cell membrane• All cells have hereditary material (DNA)• All have cytoplasm and organelles. Cytoplasm
is the fluid within a cell which provides a safe environment for the organelles. Organelles are the structures within the cell that have specific duties to make the cell a functioning unit.
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Two Types of Cells• Eukaryotic
• Are complex and of different types.
• Have a nucleus and many organelles.
• Contain more DNA due to different jobs within the cell. DNA is linear (in a line).
• Possess a cell membrane or a cell wall.
• All living things other than bacteria.
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Two Types of Cells• Prokaryotic
• Contain no nucleus.• Have no membrane
covered organelles, but do have ribosomes to make protein.
• Possess circular DNA.
• Are bacteria.