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The Cell Theory. The CELL THEORY, or cell doctrine, states that all organisms are composed of similar units of organization, called cells.

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Presentation on theme: "The Cell Theory. The CELL THEORY, or cell doctrine, states that all organisms are composed of similar units of organization, called cells."— Presentation transcript:

1 The Cell Theory

2 The CELL THEORY, or cell doctrine, states that all organisms are composed of similar units of organization, called cells.

3 History Leading up to Cell Theory 1.First compound microscope developed Zacharias Jansen, of Middleburg, Holland, around the year Zacharias Jansen, of Middleburg, Holland, around the year 1595.

4 History Leading up to Cell Theory 2.Robert Hooke English Scientist English Scientist Observed cells in cork Observed cells in cork Approx Approx. 1663

5 History Leading up to Cell Theory 3.Antony van Leeuwenhoek First to observe bacteria and protozoa First to observe bacteria and protozoa Called animacules Called animacules Approx Approx. 1673

6 Development of Cell Theory 1.Robert Brown British botanist British botanist Discovered the nucleus of a cell Discovered the nucleus of a cell

7 Development of Cell Theory 2.Theodor Schwann German doctor German doctor Described animal cells with nucleus Described animal cells with nucleus

8 Development of Cell Theory 3.Matthias Schleiden German botanist German botanist Described plant cells with a nucleus Described plant cells with a nucleus

9 Development of Cell Theory 4.Rudolf Virchow German doctor German doctor Stated every cell originates from another cell. Stated every cell originates from another cell. About 1855 About 1855

10 Tenants of Modern Cell Theory 1.All known living things are made up of cells. 2.The cell is structural & functional unit of all living things. 3.All cells come from pre-existing cells by division.

11 Tenants of Modern Cell Theory 4.Cells contain hereditary information which is passed from cell to cell during cell division. 5.All cells are basically the same in chemical composition. 6.All energy flow (metabolism & biochemistry) of life occurs within cells. 6.All energy flow (metabolism & biochemistry) of life occurs within cells.

12 Historical Problem with the Cell Theory Flew in the face of current belief Flew in the face of current belief Then, current belief was life originated from non-life Then, current belief was life originated from non-life Known as Spontaneous Generation Known as Spontaneous Generation Disproved by Louis Pasteur Disproved by Louis Pasteur

13 Pasteurs Work Nutrient broths were heated and sterilized in a flask with a straight neck and a curved neck.

14 Pasteurs Work 1.Step 1 of his procedure As his control, straight-neck flask As his control, straight-neck flask Allowed bacteria to grow Allowed bacteria to grow

15 Pasteurs Work 2.Step 2 of his procedure S-shaped necks. S-shaped necks. With such necks bacteria could not enter With such necks bacteria could not enter Therefore no bacteria grew. Therefore no bacteria grew.

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17 Pasteurs Work Straight-neck, bacteria S-shaped neck, no bacteria Straight-neck, bacteria S-shaped neck, no bacteria So, based on his observations, what can you conclude? So, based on his observations, what can you conclude?

18 General Observations All cells posess: 1.Cell membrane 2.Cytoplasm 3.Ribosomes All cells posess: 1.Cell membrane 2.Cytoplasm 3.Ribosomes

19 General Observations Prokaryotes Prokaryotes 1.Single celled 2.Genetic material is a single, circular strand 3.No nucleus 4.No membrane bound organelles Eukaryotes Eukaryotes 1.Began as single- celled 2.Genetic material – many, strings 3.Has a nucleus 4.Membrane bound organelles 5.Became multi- celled

20 General Observations Why are cells so small? Why are cells so small? 1.Exchange sufficient amount of material 2.Surface area to volume ratio

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