In the biological sciences, cell theory was first developed in the mid-1800s when it was realised that all living organisms were made up of cells. It forms the basis of the scientific discipline of cell biology.
The cell is the basic structural and functional unit and is the smallest unit to be found in living organisms. It can also replicate independently which is another key characteristic. Cells show immense variety too in structure and function. They can exist as individual single cell organisms such as bacteria. As cells come together they form multicellular structures such as tissues and organs which ultimately form the larger unit structures in animals and plants.
Robert Hooke identified cells as distinct bodies in 1665. He was able to employ one of the earliest microscopes. The first cells were noticed in very thin slices of bottle corks. The observed tiny pores he called cells from the Latin word ‘cella’. These cells looked like a honeycomb of tiny boxes. At the time he thought that only plants and fungi but not animals contained cells. All of these structures were beautifully illustrated in his book ‘Micrographia’.
In 1673, the Dutchman Anton van Leeuwenhoek used a hand microscope to study pond algae and from this, identified single-cell microorganisms. He called these ‘animalcules’. His other contributions include finding ‘cells;’ in birds and fish, dogs and humans.
The study of cells did not develop much after this because of the theory of ‘Spontaneous Generation’. This was the idea that life appeared spontaneously based on observations that mice would be seen in dirty clothes or that maggots would appear on rotting meat. The observations were clearly not developed at all. It was only when Louis Pasteur conclusively showed in the early 19th century that Spontaneous Generation was a fallacy.
Cell Theory Development
Mathias Schleiden, a German botanist is 1838 showed that all plant parts were made of cells. A year later, his good friend, the German physiologist, Theodor Schwann, concluded that all animal tissues were composed of cells.
A few decades later in 1858, the German physician Rudolf Virchow discovered that cells arose from preexisting cells – they could not just miraculously appear from nowhere.
The Original Cell Theory
There are three key tenets.
- All organisms are composed of one or more cells
- The cell is the basic unit of life in all living things.
- All cells are produced by the division of preexisting cells.
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