History
Robert Hooke, an English naturalist and inventor, greatly improved the design of the microscope in the XVII century and he published the results of studies in which he introduced the term "cell", observing the structure of the bark of a cork tree, whose structure looks like a honeycomb. Each such element was called a cell. For the next 150 years Microscopic objects were studied by scientists Nehemiah Grew, Marcello Malpighi and Anton van Leeuwenhoek. At that time there was no talk about the structure of the cell, because the microscope of that time did not allow to distinguish such small details.
In the 19th century, Ernst Abbe gathered together the knowledge about microscopes and deduced the theory by which the production of microscopes it was established by a German company, the quality has grown significantly. Also, by this time have been improved techniques for preserving living matter for research, which in total made it possible to study cells in more detail. In 1831 Robert Brown discovered the presence of a nucleus in every cell and in 1838 Matthias Schleiden put forward the assumption, that cells are the structural unit of all plants.
In 1839, Theodor Schwann confirmed the presence of cells in animals, from which the cell theory originated, which united the study of living organisms. Since 1990, knowledge about the cell has increased significantly, especially in the fields of genetics and cellular physiology, in connection with the discovery of the electron microscope. Also a great contribution was made by the molecular biology, allowing the study of all elements of the cytoplasm.
Definitions
Cell theory is based on the assumption that all living organisms, from the smallest to the largest, they consist of cells.
A cell is the basic structural unit of any living organism.
A unicellular organism is a living organism consisting of a single cell.
A multicellular organism is a living organism consisting of two or more cells.Examples of unicellular organisms can be bacteria or other protozoa.
Postulates of cell theory
All living organisms consist of one or more cells
The cell is the basic structural and functional unit of a living organism
Cells originate only from other cells
