The basic provisions of the cell theory are the basis for understanding the laws of origin and existence of living organisms, consisting of elementary structural units. This biological generalization proves that life exists only in a cell, and that each "living cell" is a whole system capable of independently existing.
The main provisions of the cell theory were formulated by M. Schleiden and T. Schwann and supplemented by R. Virchow. Before making conclusions and formulating the postulates of this theory, experts worked through the works of many of their predecessors. So, in 1665, R. Hooke for the first time saw formations called “cells” on a cork. Then the cellular structure of many plants was described. Later, A. Leeuwenhoek described unicellular organisms. In the nineteenth century improvement in the design of the microscope leads to the expansion of concepts about the structure of organisms, the concept of living tissues is introduced. T. Schwann conducts a comparative analysis of the smallest structural unit in representatives of flora and fauna, and Schleiden publishes the book "Materials on Phytogenesis".
Basicprovisions of the cell theory developed by Schleiden and Schwann:
- All representatives of flora and fauna consist of elementary structural units.
- The growth and development of plant and animal organisms occur due to the appearance of new "living cells".
This structure is the smallest unit of living things, and the body is their totality.
Then R. Virchow added a very important point that every structural unit comes from its own kind. This work has been edited and summarized many times. Now the main provisions of modern cell theory look like this:
- A cell is the elementary unit of life.
- The smallest structural units of all living things are homologous in composition, life processes and metabolism.
- Cells multiply by maternal division.
- All elementary units of life have one origin, i.e. they are totipotent.
- In multicellular organisms, the smallest units of living things are united among themselves according to the functions they perform, while forming more complex structures (tissue, organ and organ system).
- Each "living cell" is an open system that is able to independently regulate the processes of renewal, reproduction and maintain homeostasis.
In recent years (after many scientific discoveries), this theory has been expanded, supplementing with new information. However, she does notfinally systematized, so some of its postulates are interpreted quite arbitrarily. Consider the most common additional provisions of cell theory:
- The smallest structural units of pre-nuclear and nuclear organisms are not completely identical in their composition and structure.
- The continuity of the transmission of hereditary information also applies to some organelles (chloroplasts, mitochondria, chromosomes, genes) of the "living cell".
- Elementary units of the living, though totipotent, however, the work of their genes is different. This is what leads to their differentiation.
- Multicellular organisms are a complex system, the functioning of which is carried out due to chemical factors, humoral and nervous regulation.
Thus, the main provisions of the cellular theory are a generally accepted biological generalization, which proves the unity of the principle of the structure, existence and development of all living beings that have a cellular structure.
