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Cell Theory Timeline
Transcript of Cell Theory Timeline
The Egyptians knew a lot about human anatomy because of the practice of mummification, but religious laws prevented them from studying the bodies in greater depth. It's taken thousands of years. 1. All living things are composed of one or more cells. 2. Cells are the smallest units of life. 3. All cells come from pre-existing cells. Images from:
Lorenz Oken (1802)
He believed that we were all made from the same fundamental unit of life called ‘infusoria’, which is actually incorrect, but he also came up with a new system of animal classification. How did scientists come up with this theory? Aristotle (350 BCE)
He supported the theory of spontaneous generation, the idea that living organisms could come from nonliving things. Anton van Leeuwenhoek (1674)
His improved microscope allowed him to observe the algae Spirogyra as well as living bacteria and protozoa. He called them "animalcules." Francesco Redi (1668)
He published a series of controlled experiments that proved that insects can't grow out of rotting meat, the first step to disproving the theory of spontaneous generation. Medieval Europeans (Around 400AD) Biological thought was changed by
interest in empiricism and discovery
of novel organisms. Hans and Zacharias Janssen (1590) He is believed to be the first to event the
compound microscope. He was the first to use the term "cell" to name the micro honeycomb cavities in cork and for describing biological organisms because of the resemblance of plant cells to monks' cells. The cell theory could not have advanced if it
were not for advances in microscopes. Robert Hooke (1665) Andreas Vesalius (1543)
He published "On the Structure of the Human Body" and is known as the father of human anatomy. John Needham (1745)
One of his famous discoveries came when he observed soup that had been exposed to air contained micro-organisms. He theorized that life was present in all inorganic matter, including air, which could cause spontaneous generation. Lazzaro Spallanzani (1765)
Not convinced by Needham’s claims of spontaneous generation. To prove this he put the soup in an airtight container and found that after several days the soup did not contain any microorganisms. Robert Brown (1830) He recognized the nucleus as an essential part of living cells in most plants. Theodor Schwann (1837) He stated that "All living things are composed of cells and cell products". He also proved cellular origin. Matthias Schleiden (1838) He wrote "Contributions to Phytogenesis" which stated that different parts of plant organisms are made up of cells. He also recognized the importance of the nucleus and saw the connection between it and cell division. Rudolph Vichrow (1850) He was the first to recognize leukemia cells. He also accepted and plagiarized Robert Remak's work that said that "the origin of cells is the division of preexisting cells". He also applied this theory to the effects of disease. Louis Pasteur (1860s)
He conducted many experiments trying to prove where bacteria actually came from. He was able to prove that bacteria were introduced by the environment, and could not have just appeared. made of cells! THEORY OF KNOWLEDGE:
Knowledge is defined as justified true belief, and that belief is constantly changing in science as technology improves and new discoveries are made.
For example, the theory of spontaneous generation was widely accepted for hundreds of years, but now it seems ridiculous because it has been proved wrong by recent scientific discoveries.
How do we know what we know in science?
Our theories are supported by lots of data and experiments that are repeated over and over again.