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The Cell Theory

The Cell Theory. What is a cell. The cell is the basic structural and functional unit of life. The average human being is composed of around 100 Trillion individual cells!!! It would take as many as 50 cells to cover the area of a dot on the letter “ i ”. Discovery of Cells.

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The Cell Theory

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  1. The Cell Theory

  2. What is a cell • The cell is the basic structural and functional unit of life. • The average human being is composed of around 100 Trillion individual cells!!! • It would take as many as 50 cells to cover the area of a dot on the letter “i”

  3. Discovery of Cells • 1665- English Scientist, Robert Hooke, discovered cells while looking at a thin slice of cork. • He described the cells as tiny boxes or a honeycomb • He thought that cells only existed in plants and fungi

  4. Anton van Leuwenhoek • 1673- Used a handmade microscope to observe pond scum & discovered single-celled organisms • He called them “animalcules” • He also observed blood cells from fish, birds, frogs, dogs, and humans • Therefore, it was known that cells are found in animals as well as plants

  5. In your Journal:In one or two complete sentences describe what the following quote tells us about the origin of new life. • Quote: • “Fireflies rise from the morning dew, fish and frogs from a muddy stew, maggot worms from rotting meat and mice shall come from sweat and wheat.” What is the Cell Theory & How was it developed??

  6. 150-200 Year Gap??? • Between the Hooke/Leuwenhoek discoveries and the mid 19th century, very little cell advancements were made. • This is probably due to the widely accepted, traditional belief in Spontaneous Generation. • Examples: -Mice from dirty clothes/corn husks -Maggots from rotting meat

  7. What is Spontaneous Generation? • the belief that living things can come from non-living things. • Was once thought to be true, but is now known to be false! How was it disproved? - the following scientists with their combined experiments proved the theory of spontaneous generation to be false & helped develop the Cell Theory.

  8. Who was… Francesco Redi? (1668) • scientist whose experiments proved maggots did not come from rotting meat.

  9. 19th Century Advancement • Much doubt existed around Spontaneous Generation thanks to Reddi’s experiments • Conclusively disproved by Louis Pasteur ? = +

  10. Who was…Matthias Schleiden? (1830’s) Onion cells Elodea cells Cork cells • studied numerous plant parts under the microscope and declared “ALL PLANTS ARE MADE OF CELLS!”

  11. Who came up with this theory? All plants are made of cells! 1. Schleiden (circa 1838) Onion skin cells

  12. Who was… Theodor Scwhann? (mid 1830’s) • Cheek cells Amphibian Blood • Used a microscope to observe numerous animal tissues and declared “ALL ANIMALS ARE MADE OF CELLS!”

  13. Development of Cell Theory • 1838- German Botanist, Matthias Schleiden, concluded that all plant parts are made of cells • 1839- German physiologist, Theodor Schwann, who was a close friend of Schleiden, stated that all animal tissues are composed of cells.

  14. Who was… Rudolf Virchow? - observed living cells dividing and declared “ALL CELLS COME FROM OTHER LIVING CELLS!”

  15. Development of Cell Theory • 1858- Rudolf Virchow, German physician, after extensive study of cellular pathology, concluded that cells must arise from preexisting cells.

  16. The Cell Theory Complete • 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)

  17. Modern Cell Theory • Modern Cell Theory contains 4 statements, in addition to the original Cell Theory: • The cell contains hereditary information(DNA) which is passed on from cell to cell during cell division. • All cells are basically the same in chemical composition and metabolic activities. • All basic chemical & physiological functions are carried out inside the cells.(movement, digestion,etc) • Cell activity depends on the activities of sub-cellular structures within the cell(organelles, nucleus, plasma membrane)

  18. How Has The Cell Theory Been Used? • 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.)

  19. Cell Theory Timeline Project • Materials: book, butcher paper, markers • Purpose: To understand what a theory is, how the cell theory developed and how this development follows the pattern of scientific development. • Background: Science distinguishes itself from other ways of knowing and from other bodies of knowledge through the use of empirical standards, logical arguments, and skepticism, as science strives for explanations of the world. Scientists develop theories to explain a large range of observations. Theories are tested by many independent scientists an allow a scientist to make accurate predictions about new situations. The Cell theory has been developed over time and new knowledge has often been based on technological breakthroughs.   • Procedure: Using Butcher paper create a timeline which follows the development of the cell theory. For each major development list the date, name of scientists involved and how one or more of the following influenced it’s acceptance. Include Pictures and descriptions

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