Cell theory
The cell theory is one of the fundamental findings in the field of biology . It says that all plants and animals as well as their organs , however varied they may be, are always composed of cells . This theory led to far-reaching conclusions: Growth is a process in which more and more cells are formed, which are always formed from cells. The cell also plays an essential role in reproduction. New individuals always emerge from living cells through cell division ; there can never be spontaneous generation, i.e. the formation of cells from dead material, can be observed. The findings of cell theory finally led to a principle of biology, which was first formulated in Latin by Rudolf Virchow in 1855: omnis cellula e cellula (every cell arises from a cell).
History of the cell theory
The development of cell theory is closely linked to the history of cell biology (cytology). After the invention of optical devices like the microscope , the anatomical structure of plants could be examined. In 1665 Robert Hooke was the first to coin the term cell (cellula, little chamber) after observing it in the tissue of the cork , later he found similar structures in other plants.
In his textbook Phytotomie in 1830 the physician and botanist Franz Julius Ferdinand Meyen described the microscopic structure of plant organs from cells. In the same year, Karl Heinrich Baumgärtner published his educational sphere theory, which is also regarded as a precursor of the cell theory.
The cell theory was first formulated for plants in 1838 by Matthias Schleiden . In the same year Theodor Schwann expanded this statement to include animal organisms. The essential commonality of all living beings was thereby emphasized. These observations were summarized in Schwann's " Microscopic investigations into the correspondence in the structure and growth of animals and plants " and published in 1839. Schwann also formulated the basic principles of embryology by observing that an egg is a single cell that eventually develops into a complete organism .
The theory was expanded to include medicine in the 1850s by the Berlin doctor Rudolf Virchow . In 1858 Virchow published his theory of cellular pathology , which states that diseases are based on disorders of the body's cells. This realization is one of the pillars of today's pathology. The influence of microorganisms on the development of diseases did not play a role for Virchow.
Through the work of Louis Pasteur , the possibility of spontaneous generation (generatio spontanea) was finally ruled out.
Central statements
The statements of cell theory generally accepted today state:
- All organisms consist of one or more cells.
- Cells always arise from other cells through cell division.
- All cells have essentially the same basic structure and biochemical structure.
- The cell is the fundamental unit for the structure and function of organisms.
- The basic metabolism takes place within the cells.
- Genetic material and genetic information are passed on when cells divide.
Individual evidence
- ^ Heinz Otremba: Rudolf Virchow. Founder of cellular pathology. A documentation. Echter-Verlag, Würzburg 1991, p. 5.