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Cell Theory Timeline

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Nessreen G

on 2 October 2012

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Transcript of Cell Theory Timeline

By: Noha Eilouti and Nessreen Ghanem Cell Theory All living things are composed of cells
Cells are the smallest unit of life
All cells come from pre-existing cells The Cell Theory Ancient Egyptians developed embalming or mummification.
Further dissection was considered sinful, so their knowledge was limited.
At that age, they knew the most about the human body through removing vital organs. They learned how the human body has components that work together which led to the second part of the cell theory, which is "Cells are the smallest unit of life". Ancient Egyptians
1300 B.C. Aristotle
384 B.C. Medieval Europeans
5th to 15th Century Andreas Vesalius
1543 A.D. Hans and Zacharias both invented the first compound microscope.
Allowed following scientists to site and observe cells
Studying cells allowed scientists to come to the conclusion that "All living things are made of cells." Hans and Zacharias Janssen
1590 The first person to observe cells.
Hooke coined the term "cell" while observing a piece of cork, which had compartments resembling monks' cells.
This led to greater understanding of cells and life and to the first part of the cell theory which states that "All living things are made of cells." Aristotle did numerous experiments and dissections
he was the first to theorize that each germ must have come from another
he introduced the idea that each gene has a definite parent and a similar offspring which led to "existing cells come from other cells". Advanced the idea of spontaneous generation or the idea that life occurs spontaneously at the microscopic level without the need for reproduction- this contradicts the cell theory John Needham
1760 Proved spontaneous generation wrong by redoing broth experiment originally done by Needham Lazzaro Spallanzani
1768 In this time period, people began to question the nature of life through a scientific perspective.
People didn't contribute much to the cell theory, but many of the foundations of biology can be traced back to this time period. Recognized that all living things were made of cells - "Thus every living body is essentially a mass of cellular tissue" Jean Baptiste Lamarck
1801 Stated that "All living organisms originate from and consist of cells" Lorenz Oken
1802 Observed plant cells and discovered as well as named the cell nucleus Robert Brown
1833 Concluded that all plant tissues are composed of cells and that embryonic plants arise from single cells he studied human anatomy by dissecting the human body, or cadaver.
his studies clarified how cells work together to form complex organs and systems. This showed how the second component of the cell theory came to be: "Cells are the smallest unit of life." Theodor Schwann
1839 Published aphorism "omnis cellula e cellula" which means that every cell stems from another cell Conducted experiment similar to Needham but instead used it to disprove spontaneous generation once and for all - used S shaped beaker to trap microorganisms and prevent them from entering broth Louis Pasteur
1860 TOK Connections Robert Hooke
1665 Anton van Leeuwenhoek
1674 Francesco Redi
1668 Examined heated broth and discovered microorganisms both before and after heating the broth- later dismissed as false information as he didn't heat the broth hot enough to kill the microorganisms Redi disproved the idea of spontaneous generation.
He thought that "Omne vivum ex ovo" or "All life comes from an egg"
This helped shape the third part of the cell theory, "Existing cells come from other cells". invented lenses that could magnify up to 270 percent.
he was the first to see bacteria and protozoa
he discovered spermatozoa which explained reproduction.
His lenses allowed him and following scientists to find evidence to support the cell theory as a whole. Little contribution to the cell theory - however, did theorize about the origins of cells which is left unanswered by the cell theory The Cell Theory has changed numerous times since it first began developing in Ancient Egypt. When Francesco Redi disproved spontaneous generation, which is the third part of the Cell Theory, John Needham disagreed, and Louis Pasteur re-supported it again. This is just one example of how this theory was modified and adjusted over time, based on new experiments and evidence. In fact, this theory is still being refuted and supported everyday.

"All living cells are made of cells" depends on the definition of a cell. Muscle cells, for instance, have more than one nuclei. Fungal cells have many nuclei and continuous cytoplasm and protoctista do not have one specific function.
"Cells are the smallest unit of life" depends on what scientists' definition of life is. The characteristics of what scientists define life as may vary.

"Existing cells come from other cells" raises an important questions : If all cells share a common ancestor, then are all organisms related? and which cell was the first? Also proved that both egg and sperm are necessary in the process of reproduction of new cells This supports the idea that cells are formed from preexisting cells Accredited for contributing towards the theory of evolution Offered a wealth of knowledge on inheritance and acquired characteristics Proved that "something" in parents cells are passed on to their offspring Developed new system of animal classification based on evolution: Dermatozoa- invertebrates , Glossozoa - fish with tongues, Rhinozoa - reptiles with noses that open into the mouth and used for breathing, Otozoa - birds with the first external open ears, Ophthalmozoa - mammals that have all sensory organs Believed in both the ideas that all living organisms have cells and that cells are formed by preexisting cells Stressed its importance in reproduction and recognized its significance as an essential organelle for living cells Believed that all living things are composed of cells Declared that the cell is the basic building block of plant matter Stated that plants grew through the production of new cells, which he believed were formed from the nuclei of old cells - incorrect about the purpose of nuclei but basically outlined the cell theory Observed plants on the microscopic level First to demonstrate that the cell theory applies to both normal and diseased cells - that diseased cells come from healthy tissue Added to the cell theory and strengthened the theory that cells exist from preexisting cells Postulated the Germ Theory which states that microorganisms cause infectious diseases Proved the cell theory by showing that spontaneous generation does not exist and all cells are formed by preexisting cells Matthias Schleoden
1838 Reached the same conclusions as Schleiden except in animals rather than plants Ended controversy that plant and animals were fundamentally different. Examined the cellular structure in animal cartilage and determined that cells are the basic units of life Rudolf Virchow
1855 Although the cell theory is accepted all throughout the globe, it is still in fact a theory that can be proved or disproved as long as there is sufficient, accurate data to support the argument.

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"Discovery of Cells and the Developmwnt of Cell Theory." Discovery of Cells and the Developmwnt of Cell Theory. N.p., n.d. Web. 27 Sept. 2012. <http://www.smithlifescience.com/celltheory.htm>.
"Timeline of Cell Theory 2 - Timeline Help." Timeline of Cell Theory 2 - Timeline Help. Jonathan W. Nickolsen, 2008-2012. Web. 27 Sept. 2012. <http://www.timeline-help.com/timeline-of-cell-theory.html>.
CliffsNotes.com. A Brief History of Microbiology. 1 Oct 2012
<http://www.cliffsnotes.com/study_guide/topicArticleId-8524,articleId-8406.html>.
Bibliography Thank you! :)
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