Development of the Cell Theory

Big Question Where do living things come from?

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

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 development of the theory  could see small stuffs

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

1688. Francesco Redi (ITALIAN) Performed an experiment to see if rotting meat changed into flies; hypothesis of spontaneous generation was not supported.

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.

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.

1838. Matthias Schleiden (GERMAN) Looked at numerous plant samples under a microscope, concludes all plants are made of cells. Has dinner with colleague and zoologist Theodor Schwann…

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

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)

1858. CELL THEORY The 3 Basic Components of the Cell Theory were now complete: All organisms are composed of one or more cells. (Schleiden & Schwann)(1838-39) The cell is the basic unit of life in all living things. (Schleiden & Schwann)(1838-39) 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

Modern Cell Theory Adds 4 more statements: 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) All cells are basically the same in chemical composition. All energy flow (metabolism & biochemistry) of life occurs within cells. Cell activity depends on the activities of sub-cellular structures within the cell(organelles, nucleus, plasma membrane)

1864. Louis Pasteur (FRENCH) Set out to denounce the ideas of spontaneous generation; is successful

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.)

1970. Lynn Marguilis (AMERICAN) Proposes the idea that certain organelles (chloroplasts & mitochondria) were once free living cells themselves  ENDOSYMBIOTIC THEORY is added