Cell theory is a way that we can describe the living things around us in a biological way.
Since cells are a basic life unit, we consider them to be alive and they can also be part of bigger living things. Other cells, such as bacteria, are smaller and can exist as a single unit.
To make things easier to explain and understand, scientists have divided cell theory into three principles:
Breaking things down to these three principles is important so that scientists can study cells, what they are made of, and how they reproduce.
The study of cells also helps us understand us and the other animals and plants that are around us.
The old idea of Spontaneous Generation
Science is always learning and changing and before scientists developed cell theory, they had another idea that they called spontaneous generation.
In that idea they thought that life could be created from non-living things. An example of this really old idea is that they thought fleas could be made from dust.
It may sound silly because we know fleas only come from fleas.
Aristotle was a Greek philosopher and while very respected, he was the one that came up with the idea of spontaneous generation.
Because Aristotle was so smart, no one disputed it until the mid-1800’s when they changed the idea to living things can only come from other living things.
Scientists were trying to get more information about cells for many years. The problem was that they didn’t have very powerful microscopes and they had to do the best that they could with what they had.
Robert Hooke made use of a compound microscope that had two lenses so that he could view the inside of a cork, and some insects and leaves. In 1665, he was the first scientist to develop the idea of a cell.
There were a lot of other scientists and naturalists that made use of this new miracle instrument and the ongoing investigation was accomplished by Nehemiah Grew (1641-1712), and Marcello Malpighi (1628-1694).
Grew had his work published in 1682 as The anatomy of plants. However, it isn’t very clear who was the first to see animal cells, Malpighi, Jan Swammerdam (1637-1680) or Antonie van Leeuwenhoek (1632-1723).
It was Leeuwenhoek that made discoveries and drawings of what he called “little animalules,” and this opened up a whole new world of research.
By the 1800’s, the competition for discovery was getting fierce. Theodore Schwann and Matthias Schleiden (1804-1881) are given the credit for their cell theory, even though some of their information wasn’t completely correct.
Working together they made the assumption that all living things are made up of cells and they stated that the basic units of life were cells.
Scientists were very excited about the new theories and one that came up with a phrase of “omne vive ex ovo” (every living thing comes from other things) was Rudolph Virchow. He added to the basic idea of cell theory with his quote.
The cell theory of modern times has taken the original idea and added new principles as part of modern cell theory:
The first rule of Cell Theory is all living organisms are composed of one or more cells. This has been disputed as there are non-cellular entities such as viruses that are sometimes given the title of a life form.
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