development of the cell theory. big question where do living things come from?
TRANSCRIPT
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Development of the
Cell Theory
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Big Question
• Where do living things come from?
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1600s. Ideas of the time
• For centuries, people accepted the prevailing explanation for the sudden appearance of some organisms (flies, maggots, mice, bees)
• Scholars of the day gave a name to their accepted theory: spontaneous generation
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1590. Zacharias & Hans Janseen (DUTCH)
• Credit for the first compound (more than one lens) microscope is usually given to Zacharias Jansen, of Middleburg, Holland, around the year 1595.
• HUGE impact on developmentof the theory could see small stuffs
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1655. Robert Hooke (ENGLISH)
• Using a microscope, looks at a thin slice of cork.
• Calls the spaces in the cork “Cells” first person to use the word to describe these microscopic structures
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1688. Francesco Redi (ITALIAN)
• Performed an experiment to see if rotting meat changed into flies; hypothesis of spontaneous generation was not supported.
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1674. Anton van Leevwenhoek (DUTCH)
• Developed his own microscope & looked at pond samples identified simple microorganisms (bacteria & protozoa) which he called “animacules”
• Also looked at blood samples from plants and animals to see cells.
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150-200 Year Gap???
• Between the Hooke/Leuwenhoek discoveries and the mid 19th century, very little cell advancements were made.
• This is due to the widely accepted, traditional belief in Spontaneous Generation.
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1838. Matthias Schleiden (GERMAN)
• Looked at numerous plant samples under a microscope, concludes all plants are made of cells.
• Has dinner with colleague andzoologist Theodor Schwann…
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1839. Theodor Schwann(GERMAN)
• After looking at numerous animal samples, concludes all animals are made of cells.
• Publishes “Microscope Investigations on the Accordance in the Structure of Growth of Plants and Animals,” which stated first statement of the cell theory:– ALL LIVING THINGS ARE MADE OF CELLS
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1855. Rudolph Virchow (GERMAN)
• Extends work of Schleiden & Schwann by proposing that all living cells must rise from pre-exisiting cells.
• RADICAL idea (spontaneous generation still widely accepted)
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1858. CELL THEORY
• The 3 Basic Components of the Cell Theory were now complete:1. All organisms are composed of one or more cells.
(Schleiden & Schwann)(1838-39)2. The cell is the basic unit of life in all living things.
(Schleiden & Schwann)(1838-39)3. All cells are produced by the division of preexisting cells.
(Virchow)(1858)• Cell Theory is accepted by scientific community, but
skepticism exists due to belief in spontaneous generation
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Modern Cell Theory
• Adds 4 more statements:1. Cells contains hereditary information which is passed
from cell to cell during cell division. (The first cell is the exception because it could not have come from a previously existing cell)
2. All cells are basically the same in chemical composition.3. All energy flow (metabolism & biochemistry) of life
occurs within cells. 4. Cell activity depends on the activities of sub-cellular
structures within the cell(organelles, nucleus, plasma membrane)
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1864. Louis Pasteur (FRENCH)
• Set out to denounce the ideas of spontaneous generation; is successful
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How is the Cell Theory Used Today?
• The basic discovered truths about cells, listed in the Cell Theory, are the basis for things such as:– Disease/Health/Medical Research and Cures(AIDS, Cancer,
Vaccines, Cloning, Stem Cell Research, etc.)
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1970. Lynn Marguilis (AMERICAN)
• Proposes the idea that certain organelles (chloroplasts & mitochondria) were once free living cells themselves ENDOSYMBIOTIC THEORY is added