From the moment of the discovery of cells, before the current state of the cell theory was formulated, almost 400 years have passed. For the first time the cell was investigated in 1665 by the naturalist from England Robert Hooke. Noticing cellular structures on a thin section of cork, he gave them the name of cells.
In his primitive microscope, Hooke could not yet see all the features, but as optical instruments improved and staining techniques appeared, scientists became more and more immersed in the world of fine cytological structures.
How the cell theory came about
A landmark discovery that influenced the further course of research and the current state of cell theory was made in the 30s of the XIX century. The Scot R. Brown, studying the leaf of a plant with a light microscope, found similar rounded seals in plant cells, which he later called nuclei.
From that moment on, an important sign appeared for comparison betweenare structural units of various organisms, which became the basis for conclusions about the unity of the origin of living things. Not for nothing that even the current position of cell theory contains a link to this conclusion.
The question of the origin of cells was raised in 1838 by the German botanist Matthias Schleiden. Massively examining plant material, he noted that in all living plant tissues, the presence of nuclei is mandatory.
His compatriot zoologist Theodor Schwann made the same conclusions about animal tissues. After studying the works of Schleiden and comparing many plant and animal cells, he concluded: despite the diversity, they all have a common feature - a formed nucleus.
Schwann and Schleiden cell theory
Having put together the available facts about the cell, T. Schwann and M. Schleiden put forward the main postulate of the cell theory. It consisted in the fact that all organisms (plants and animals) consist of cells that are similar in structure.
In 1858, another addition was made to the cell theory. Rudolf Virchow proved that the body grows by increasing the number of cells by dividing the original maternal ones. It seems obvious to us, but for those times his discovery was very advanced and modern.
At that time, the current position of Schwann's cell theory in textbooks is formulated as follows:
- All tissues of living organisms have a cellular structure.
- Cellsanimals and plants are formed in the same way (cell division) and have a similar structure.
- The body consists of groups of cells, each of them is capable of independent life.
Becoming one of the most important discoveries of the 19th century, cell theory laid the foundation for the idea of the unity of origin and commonality of the evolutionary development of living organisms.
Further development of cytological knowledge
Improvement of research methods and equipment has allowed scientists to significantly deepen their knowledge of the structure and life of cells:
- the relationship between the structure and function of both individual organelles and cells as a whole (specialization of cytostructures) has been proven;
- each cell individually demonstrates all the properties inherent in living organisms (grows, reproduces, exchanges matter and energy with the environment, is mobile to one degree or another, adapts to changes, etc.);
- Organelles cannot individually exhibit these properties;
- animals, fungi, plants have identical organelles in structure and function;
- all cells in the body are interconnected and work together to perform complex tasks.
Thanks to new discoveries, the provisions of the theory of Schwann and Schleiden have been refined and supplemented. The modern scientific world uses the extended postulates of the underlying theory in biology.
5 positions of modern cell theory
In the literature, you can find a different number of postulates of modern cell theory, the most completeoption contains five items:
- Cell is the smallest (elementary) living system, the basis of the structure, reproduction, development and life of organisms. Non-cellular structures cannot be called living.
- Cells appear exclusively by dividing existing ones.
- The chemical composition and structure of the structural units of all living organisms are similar.
- A multicellular organism develops and grows by dividing one/several original cells.
- The similar cellular structure of organisms inhabiting the Earth indicates a single source of their origin.
The original and modern positions of the cell theory have much in common. Deep and extended postulates reflect the current level of knowledge on the structure, life and interaction of cells.
