How the ideas about the cell changed and the modern position of the cellular theory was formed

Since the discovery of cells, before the modern position of the cellular theory was formulated, almost 400 years have passed. For the first time the cell was examined in 1665 by a naturalist from England, Robert Hooke. Noticing the cellular structure on a thin section of cork, he gave them the name of the cells.

In his primitive microscope, Hooke could not yet consider all the features, but as the optical instruments improved, the methods of coloring the preparations appeared, scientists were increasingly immersed in the world of subtle cytological structures.

How did cellular theory develop?

A noteworthy discovery, which influenced the further course of research and the current position of the cellular theory, was made in the 30s of the XIX century. Scotsman R. Brown, studying a plant leaf with a light microscope, found similar rounded seals in plant cells, which he later called nuclei.

From that moment an important sign appeared for comparing the structural units of different organisms among themselves, which became the basis for conclusions about the unity of the origin of the living. Not for nothing that even the modern position of the cellular theory contains a reference to this conclusion.

The question of the origin of the cells was raised in 1838 by the German botanist Matthias Schleiden. Massively exploring plant material, he noted that in all living plant tissues the presence of nuclei is mandatory.

His compatriot zoologist Theodore Schwann made the same conclusions regarding the tissues of animals. After studying the work of Schleiden and comparing a lot of plant and animal cells, he concluded: in spite of the diversity, they all have a common feature - the formed nucleus.

Cell theory of Schwann and Schleiden

Gathering together the available facts about the cell, T. Schwann and M. Schleiden put forward the main postulate of the cellular theory. It consisted in the fact that all organisms (plants and animals) consist of cells that are close in structure.

In 1858, one more addition was made to the cellular theory. Rudolf Virchow proved that the body grows by increasing the number of cells by dividing the original maternal. It seems obvious to us, but for those times its opening was very advanced and modern.

At that time, the modern position of the Schwann cell theory in textbooks is formulated as follows:

1. All tissues of living organisms have a cellular structure.
2. Cells of animals and plants are formed by the same method (cell division) and have a similar structure.
3. The organism consists of groups of cells, each of them is capable of independent vital activity.

Becoming one of the most important discoveries of the XIX century, cell theory laid the foundation for the idea of the unity of origin and the generality of the evolutionary development of living organisms.

Further development of cytological knowledge

Improvement of research methods and equipment allowed scientists to significantly deepen knowledge about the structure and life of cells:

• The connection between the structure and function of both individual organelles and cells as a whole (the specialization of cytostructures) has been proved;
• Each cell individually demonstrates all the properties inherent in living organisms (grows, multiplies, exchanges matter and energy with the environment, is mobile to some extent, adapts to changes, etc.);
• Organelles can not separately demonstrate similar properties;
• In animals, fungi, plants, organelles of the same structure and function are found;
• All cells in the body are interconnected and work together, performing complex tasks.

Thanks to new discoveries, the provisions of the theory of Schwann and Schleiden were refined and supplemented. The modern scientific world uses extended postulates of the basic theory in biology.

5 provisions of modern cell theory

In the literature, you can find a different number of postulates of modern cell theory, the most complete version contains five points:

1. The cell is the smallest (elementary) living system, the basis of the structure, reproduction, development and life activity of organisms. Noncellular structures can not be called alive.
2. Cells appear exclusively by dividing existing ones.
3. The chemical composition and structure of structural units of all living organisms are similar.
4. A multicellular organism develops and grows by dividing one / several of the original cells.
5. A similar cellular structure of organisms inhabiting the Earth indicates a single source of their origin.

The initial and current positions of the cellular theory largely overlap. Deep and extended postulates reflect the current level of knowledge on the structure, life and interaction of cells.