The cell theory was created after the observations of microbiology greats such as Robert Hooke (who was the first to discover a cell in 1655), Antony vanLeeuwenhoek (first to see one under a microscope), and Henri Dutrochet (who wrote one of the most important arguments in cell theory) and combined all to establish three common and irrefutable tenets that apply to everything, big and small.
They are the following:
- All living things or organisms are made of cells and their products.
- New cells are created by old cells dividing into two.
- Cells are the basic building units of life.
These tenets can be basically explained as follows:
1- That all things that are alive are products of a cellular division which, in turn, made up the organism itself. Therefore, cells are the building blocks of everything that is alive, whether is a person, animal, or a thing.
2- That the process by which new cells are created is when an old cell divides into two cells. This means that new cells are the product of an old cell dividing itself into a two separate cells of the same type. It would be the same as what happens when we take one drop of water and push down on it. The drop of water will become two drops. The newly-formed drop will be the equivalent of the newly-formed cell.
3- That cells are what make life. They are the building blocks of life. Without them, we would not exist because, without them, we would not have ever become living things.
In conclusion, when all the observations and research on cells were put together, the cell theory was born. Its concepts are concise, simply-put, but very powerful. It just goes to show that small things are not to be taken for granted. The cell- something invisible to the human eye-is the basic maker of life.
Cell theory embraces the following main ideas:
- All living things are composed of cells and cell products.
- New cells are formed only by the division of pre-existing cells
- The cell contains inherited information (genes) that are used as instructions for growth, normal functioning, and development.
- The cell is the functional (smallest) basic unit of life; the chemical reactions of life take place within cells.
- Given suitable conditions, cells are capable of independent existence.
The cell theory has amassed tremendous credibility, largely through the invention and use of the microscope – an important tool in observing cells. Robert Hooke first described cells in 1665 while observing cork with a microscope he built himself. A few years later, Antonie van Leeuwenhoek, observed the first living cells and referred to them as ‘animalcules’, meaning little animals. In 1838, botanist Mathias Schleiden stated that plants are made of ‘independent, separate beings’ called cells. One year later, the zoologist Theodor Schwann made a similar statement about animals.
The principle that cells are the smallest units of life continues to gain support today, as we have not been able to find any living entity that is not made of at least one cell.