Nearly 400 years have passed since the discovery of cells, before the current state of cellular theory was formulated. The cell was first investigated in 1665 by Robert Hook , a naturalist from England . Having noticed cellular structures on a thin section of the cork, he gave them the name of the cells.
Hook could not yet consider all the features in his primitive microscope, but as the optical instruments improved, the methods of staining the drugs appeared, scientists more and more plunged into the world of subtle cytological structures.
How cell theory came about
A significant 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 a leaf of a plant with a light microscope, found similar round densities in plant cells, which he later called nuclei.
From this moment, an important sign appeared for comparing the structural units of various organisms with each other, which became the basis for conclusions about the unity of the origin of living things. Not for nothing that even the current position of cellular theory contains a link to this conclusion.
The question of the origin of the cells was raised in 1838 by the German botanist Matthias Schleiden. Massively examining plant material, he noted that the presence of nuclei is mandatory in all living plant tissues.
His compatriot zoologist Theodor Schwann made the same conclusions regarding animal tissue. After examining the work of Schleiden and comparing the many plant and animal cells, he concluded: despite the diversity, they all have a common feature - a formed nucleus.
The 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 cellular theory. It consisted in the fact that all organisms (plants and animals) consist of cells that are close in structure.
In 1858, another addition to cell theory was introduced. Rudolf Virchow proved that the body grows by increasing the number of cells by dividing the original maternal. This seems obvious to us, but for those times its discovery was very advanced and modern.
At that time, the current position of Schwann's cellular theory in the textbooks is formulated as follows:
- All tissues of living organisms have a cellular structure.
- The cells of animals 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.
Having become one of the most important discoveries of the 19th century, cellular 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
Improving research methods and equipment has allowed scientists to significantly deepen knowledge about the structure and vital functions of cells:
- the relationship between the structure and function of both individual organelles and cells as a whole has been proved (specialization of cytostructures);
- each cell individually demonstrates all the properties inherent in living organisms (grows, multiplies, exchanges matter and energy with the environment, is mobile to one degree or another, adapts to changes, etc.);
- organelles cannot individually exhibit similar properties;
- in animals, fungi, plants, organelles of the same structure and function are found;
- all cells in the body are interconnected and work in concert, 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 the extended postulates of the fundamental theory in biology.
5 provisions of modern cellular theory
In the literature you can find a different number of postulates of modern cellular theory, the most complete version contains five points:
- A cell is the smallest (elementary) living system, the basis of the structure, reproduction, development and vital activity 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 due to the division of one / several initial cells.
- A similar cellular structure of the organisms inhabiting the Earth indicates a single source of their origin.
The initial and modern principles of cell theory have much in common. In-depth and extended postulates reflect the current level of knowledge on the structure, life and interaction of cells.