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The Cell Theory.

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Presentation on theme: "The Cell Theory."— Presentation transcript:

1 The Cell Theory

2 The Cell Theory 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
First compound microscope developed Zacharias Jansen, of Middleburg, Holland, around the year 1595.

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

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

6 Development of Cell Theory
Robert Brown British botanist Discovered the nucleus of a cell 1833

7 Development of Cell Theory
Theodor Schwann German doctor Described animal cells with nucleus 1838

8 Development of Cell Theory
Matthias Schleiden German botanist Described plant cells with a nucleus 1838

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

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

11 Tenants of 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 (metabolism & biochemistry) of life occurs within cells.  

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

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

14 Pasteur’s Work Step 1 of his procedure
As his control, straight-neck flask Allowed bacteria to grow

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


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

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

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

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


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