) supplemented it with the most important position (every cell comes from another cell).

Schleiden and Schwann, summarizing the existing knowledge about the cell, proved that the cell is the basic unit of any organism. Animal, plant and bacterial cells have a similar structure. Later, these conclusions became the basis for proving the unity of organisms. T. Schwann and M. Schleiden introduced into science the fundamental concept of the cell: there is no life outside cells. The cell theory was supplemented and edited every time.

Provisions of the Schleiden-Schwann cell theory

1. All animals and plants are made up of cells.
2. Plants and animals grow and develop through the emergence of new cells.
3. A cell is the smallest unit of living things, and a whole organism is a collection of cells.

Basic provisions of modern cell theory

1. The cell is the elementary unit of life; outside the cell there is no life.
2. A cell is a single system; it includes many naturally interconnected elements, representing an integral formation consisting of conjugated functional units - organelles.
3. The cells of all organisms are homologous.
4. A cell comes into being only by dividing the mother cell, after doubling its genetic material.
5. A multicellular organism is a complex system of many cells united and integrated into systems of tissues and organs connected to each other.
6. The cells of multicellular organisms are totipotent.

Additional provisions of the cell theory

To bring the cell theory into more complete compliance with the data of modern cell biology, the list of its provisions is often supplemented and expanded. In many sources, these additional provisions differ; their set is quite arbitrary.

1. Prokaryotic and eukaryotic cells are systems of different levels of complexity and are not completely homologous to each other (see below).
2. The basis of cell division and reproduction of organisms is the copying of hereditary information - nucleic acid molecules (“each molecule from a molecule”). The concept of genetic continuity applies not only to the cell as a whole, but also to some of its smaller components - mitochondria, chloroplasts, genes and chromosomes.
3. A multicellular organism is a new system, a complex ensemble of many cells, united and integrated in a system of tissues and organs, connected to each other through chemical factors, humoral and nervous (molecular regulation).
4. Multicellular cells are totipotent, that is, they have the genetic potential of all cells of a given organism, are equivalent in genetic information, but differ from each other in the different expression (function) of various genes, which leads to their morphological and functional diversity - to differentiation.

Story

17th century

Link and Moldnhower established the presence of independent walls in plant cells. It turns out that the cell is a certain morphologically separate structure. In 1831, Mohl proved that even seemingly non-cellular plant structures, such as water-bearing tubes, develop from cells.

Meyen in “Phytotomy” (1830) describes plant cells that “are either solitary, so that each cell is a special individual, as is found in algae and fungi, or, forming more highly organized plants, they are combined into more or less significant masses." Meyen emphasizes the independence of metabolism of each cell.

In 1831, Robert Brown described the nucleus and suggested that it was a permanent part of the plant cell.

Purkinje School

In 1801, Vigia introduced the concept of animal tissue, but he isolated tissue based on anatomical dissection and did not use a microscope. The development of ideas about the microscopic structure of animal tissues is associated primarily with the research of Purkinje, who founded his school in Breslau.

Purkinje and his students (especially G. Valentin should be highlighted) revealed in the first and most general form the microscopic structure of the tissues and organs of mammals (including humans). Purkinje and Valentin compared individual plant cells with individual microscopic tissue structures of animals, which Purkinje most often called “grains” (for some animal structures his school used the term “cell”).

In 1837, Purkinje gave a series of talks in Prague. In them, he reported on his observations on the structure of the gastric glands, nervous system, etc. The table attached to his report gave clear images of some cells of animal tissues. Nevertheless, Purkinje was unable to establish the homology of plant cells and animal cells:

• firstly, by grains he understood either cells or cell nuclei;
• secondly, the term “cell” was then understood literally as “a space bounded by walls.”

Purkinje conducted the comparison of plant cells and animal “grains” in terms of analogy, and not homology of these structures (understanding the terms “analogy” and “homology” in the modern sense).

Müller's school and Schwann's work

The second school where the microscopic structure of animal tissues was studied was the laboratory of Johannes Müller in Berlin. Müller studied the microscopic structure of the dorsal string (notochord); his student Henle published a study on the intestinal epithelium, in which he described its various types and their cellular structure.

Theodor Schwann's classic research was carried out here, laying the foundation for the cell theory. Schwann's work was strongly influenced by the school of Purkinje and Henle. Schwann found the correct principle for comparing plant cells and elementary microscopic structures of animals. Schwann was able to establish homology and prove the correspondence in the structure and growth of the elementary microscopic structures of plants and animals.

The significance of the nucleus in a Schwann cell was prompted by the research of Matthias Schleiden, who published his work “Materials on Phytogenesis” in 1838. Therefore, Schleiden is often called the co-author of the cell theory. The basic idea of ​​cellular theory - the correspondence of plant cells and the elementary structures of animals - was alien to Schleiden. He formulated the theory of new cell formation from a structureless substance, according to which, first, a nucleolus condenses from the smallest granularity, and around it a nucleus is formed, which is the cell maker (cytoblast). However, this theory was based on incorrect facts.

In 1838, Schwann published 3 preliminary reports, and in 1839 his classic work “Microscopic studies on the correspondence in the structure and growth of animals and plants” appeared, the very title of which expresses the main idea of ​​cellular theory:

• In the first part of the book, he examines the structure of the notochord and cartilage, showing that their elementary structures - cells - develop in the same way. He further proves that the microscopic structures of other tissues and organs of the animal body are also cells, quite comparable to the cells of cartilage and notochord.
• The second part of the book compares plant cells and animal cells and shows their correspondence.
• In the third part, theoretical positions are developed and the principles of cell theory are formulated. It was Schwann's research that formalized the cell theory and proved (at the level of knowledge of that time) the unity of the elementary structure of animals and plants. Schwann's main mistake was the opinion he expressed, following Schleiden, about the possibility of cells arising from structureless non-cellular matter.

Development of cell theory in the second half of the 19th century

Since the 1840s of the 19th century, the study of the cell has become the focus of attention throughout biology and has been rapidly developing, becoming an independent branch of science - cytology.

For the further development of cell theory, its extension to protists (protozoa), which were recognized as free-living cells, was essential (Siebold, 1848).

At this time, the idea of ​​the composition of the cell changes. The secondary importance of the cell membrane, which was previously recognized as the most essential part of the cell, is clarified, and the importance of protoplasm (cytoplasm) and the cell nucleus is brought to the fore (Mol, Cohn, L. S. Tsenkovsky, Leydig, Huxley), which is reflected in the definition of a cell given by M. Schulze in 1861:

A cell is a lump of protoplasm with a nucleus contained inside.

In 1861, Brücko put forward a theory about the complex structure of the cell, which he defines as an “elementary organism,” and further elucidated the theory of cell formation from a structureless substance (cytoblastema), developed by Schleiden and Schwann. It was discovered that the method of formation of new cells is cell division, which was first studied by Mohl on filamentous algae. The studies of Negeli and N.I. Zhele played a major role in refuting the theory of cytoblastema using botanical material.

Tissue cell division in animals was discovered in 1841 by Remak. It turned out that the fragmentation of blastomeres is a series of successive divisions (Bishtuf, N.A. Kölliker). The idea of ​​the universal spread of cell division as a way of forming new cells is enshrined by R. Virchow in the form of an aphorism:

"Omnis cellula ex cellula."
Every cell from a cell.

In the development of cell theory in the 19th century, contradictions arose sharply, reflecting the dual nature of cellular theory, which developed within the framework of a mechanistic view of nature. Already in Schwann there is an attempt to consider the organism as a sum of cells. This tendency receives special development in Virchow’s “Cellular Pathology” (1858).

Virchow’s works had a controversial impact on the development of cellular science:

• He extended the cell theory to the field of pathology, which contributed to the recognition of the universality of cellular theory. Virchow's works consolidated the rejection of the theory of cytoblastema by Schleiden and Schwann and drew attention to the protoplasm and nucleus, recognized as the most essential parts of the cell.
• Virchow directed the development of cell theory along the path of a purely mechanistic interpretation of the organism.
• Virchow elevated cells to the level of an independent being, as a result of which the organism was considered not as a whole, but simply as a sum of cells.

XX century

Since the second half of the 19th century, cell theory has acquired an increasingly metaphysical character, reinforced by Verworn’s “Cellular Physiology,” which considered any physiological process occurring in the body as a simple sum of the physiological manifestations of individual cells. At the end of this line of development of cell theory, the mechanistic theory of the “cellular state” appeared, including Haeckel as a proponent. According to this theory, the body is compared to the state, and its cells are compared to citizens. Such a theory contradicted the principle of the integrity of the organism.

The mechanistic direction in the development of cell theory was subjected to severe criticism. In 1860, I.M. Sechenov criticized Virchow’s idea of ​​the cell. Later, the cell theory was criticized by other authors. The most serious and fundamental objections were made by Hertwig, A. G. Gurvich (1904), M. Heidenhain (1907), Dobell (1911). The Czech histologist Studnicka (1929, 1934) made extensive criticism of the cellular theory.

In the 1930s, Soviet biologist O. B. Lepeshinskaya, based on her research data, put forward a “new cell theory” as opposed to “Vierchowianism.” It was based on the idea that in ontogenesis, cells can develop from some non-cellular living substance. A critical verification of the facts laid down by O. B. Lepeshinskaya and her adherents as the basis for the theory she put forward did not confirm the data on the development of cell nuclei from nuclear-free “living matter”.

Modern cell theory

Modern cellular theory proceeds from the fact that cellular structure is the most important form of existence of life, inherent in all living organisms, except viruses. The improvement of cellular structure was the main direction of evolutionary development in both plants and animals, and the cellular structure is firmly retained in most modern organisms.

At the same time, the dogmatic and methodologically incorrect provisions of the cell theory must be re-evaluated:

• Cellular structure is the main, but not the only form of existence of life. Viruses can be considered non-cellular life forms. True, they show signs of life (metabolism, ability to reproduce, etc.) only inside cells; outside cells, the virus is a complex chemical substance. According to most scientists, in their origin, viruses are associated with the cell, they are part of its genetic material, “wild” genes.
• It turned out that there are two types of cells - prokaryotic (cells of bacteria and archaebacteria), which do not have a nucleus delimited by membranes, and eukaryotic (cells of plants, animals, fungi and protists), which have a nucleus surrounded by a double membrane with nuclear pores. There are many other differences between prokaryotic and eukaryotic cells. Most prokaryotes do not have internal membrane organelles, and most eukaryotes have mitochondria and chloroplasts. According to the theory of symbiogenesis, these semi-autonomous organelles are descendants of bacterial cells. Thus, a eukaryotic cell is a system of a higher level of organization; it cannot be considered entirely homologous to a bacterial cell (a bacterial cell is homologous to one mitochondria of a human cell). The homology of all cells, thus, has been reduced to the presence of a closed outer membrane made of a double layer of phospholipids (in archaebacteria it has a different chemical composition than in other groups of organisms), ribosomes and chromosomes - hereditary material in the form of DNA molecules forming a complex with proteins . This, of course, does not negate the common origin of all cells, which is confirmed by the commonality of their chemical composition.
• The cellular theory considered the organism as a sum of cells, and the life manifestations of the organism were dissolved in the sum of the life manifestations of its constituent cells. This ignored the integrity of the organism; the laws of the whole were replaced by the sum of the parts.
• Considering the cell to be a universal structural element, the cell theory considered tissue cells and gametes, protists and blastomeres as completely homologous structures. The applicability of the concept of a cell to protists is a controversial issue in cellular theory in the sense that many complex multinucleated protist cells can be considered as supracellular structures. In tissue cells, germ cells, and protists, a general cellular organization is manifested, expressed in the morphological separation of karyoplasm in the form of a nucleus, however, these structures cannot be considered qualitatively equivalent, taking all their specific features beyond the concept of “cell”. In particular, gametes of animals or plants are not just cells of a multicellular organism, but a special haploid generation of their life cycle, possessing genetic, morphological, and sometimes environmental characteristics and subject to the independent action of natural selection. At the same time, almost all eukaryotic cells undoubtedly have a common origin and a set of homologous structures - cytoskeletal elements, eukaryotic-type ribosomes, etc.
• The dogmatic cell theory ignored the specificity of non-cellular structures in the body or even recognized them, as Virchow did, as non-living. In fact, in the body, in addition to cells, there are multinuclear supracellular structures (syncytia, symplasts) and nuclear-free intercellular substance, which has the ability to metabolize and is therefore alive. To establish the specificity of their life manifestations and their significance for the body is the task of modern cytology. At the same time, both multinuclear structures and extracellular substance appear only from cells. Syncytia and symplasts of multicellular organisms are the product of the fusion of parent cells, and the extracellular substance is the product of their secretion, that is, it is formed as a result of cell metabolism.
• The problem of the part and the whole was resolved metaphysically by the orthodox cell theory: all attention was transferred to the parts of the organism - cells or “elementary organisms”.

The integrity of the organism is the result of natural, material relationships that are completely accessible to research and discovery. The cells of a multicellular organism are not individuals capable of existing independently (the so-called cell cultures outside the body are artificially created biological systems). As a rule, only those multicellular cells that give rise to new individuals (gametes, zygotes or spores) and can be considered as separate organisms are capable of independent existence. A cell cannot be separated from its environment (as, indeed, any living systems). Focusing all attention on individual cells inevitably leads to unification and a mechanistic understanding of the organism as a sum of parts.

1. Give definitions of concepts.
Cell– an elementary unit of structure and vital activity of all organisms, having its own metabolism, capable of independent existence, self-reproduction and development.
Organoid- a permanent specialized structure in the cells of living organisms that performs certain functions.
Cytology– a branch of biology that studies living cells, their organelles, their structure, functioning, processes of cell reproduction, aging and death.

2. Distribute the names of scientists from the list given (the list is redundant) into the corresponding columns of the table.
R. Brown, K. Baer, ​​R. Virchow, K. Galen, C. Golgi, R. Hooke, C. Darwin, A. Leeuwenhoek, K. Linnaeus, G. Mendel, T. Schwann, M. Schleiden.

Scientists who contributed to the development of knowledge about the cell

3. Fill in the left column of the table.

HISTORY OF CELL STUDY

4. Indicate the characteristics common to all cells. Explain due to what properties of living matter all cells have common characteristics.
All cells are surrounded by a membrane, their genetic information is stored in genes, proteins are their main structural material and biocatalysts, they are synthesized on ribosomes, cells use ATP as an energy source. All cells are open systems. They are characterized by growth and development, reproduction and irritability.

5. What is the significance of cell theory for biological science?
The cell theory made it possible to conclude that the chemical composition of all cells and the general plan of their structure are similar, which confirms the phylogenetic unity of the entire living world. Modern cytology, having absorbed the achievements of genetics, molecular biology, and biochemistry, has turned into cell biology.

7. Fill in the missing terms.
Human red blood cells have the shape of a biconcave disc.
Bone tissue includes large osteocytes with numerous processes. Blood leukocytes do not have a constant shape. The cells of the nervous tissue are very diverse, possessing the ability to excitability and conductivity.

8. Cognitive task.
The first description of a cell was published in 1665. In 1675, single-celled organisms became known. The cell theory was formulated in 1839. Why does the date of the birth of cytology coincide with the time of the formulation of the cell theory, and not with the time of the discovery of the cell?
Cytology is a branch of biology that studies organelles, their structure, functioning, processes of cell reproduction, aging and death in the cell. At the time of the discovery of the cell, the cell wall was described. Then the first cells were discovered, but their structure and functions were not known. The knowledge was not enough, it was analyzed by T. T. Schwann, M. Schleiden, and they created the cell theory.

9. Choose the correct answer.
Test 1.
The cellular structure has:
1) iceberg;
2) tulip petal;

3) hemoglobin protein;

4) a piece of soap.

Test 2.
The authors of the cell theory are:
1) R. Hooke and A. Leeuwenhoek;
2) M. Schleiden and T. Schwann;

3) L. Pasteur and I. I. Mechnikov;

4) C. Darwin and A. Wallace.

Test 3.
Which position of the cell theory belongs to R. Virchow?
1) Cell - the elementary unit of living things;
2) every cell comes from another cell;
3) all cells are similar in their chemical composition;
4) the similar cellular structure of organisms is evidence of the common origin of all living things.

10. Explain the origin and general meaning of the word (term), based on the meaning of the roots that make it up.

11. Select a term and explain how its modern meaning matches the original meaning of its roots.
Cytology– originally meant the study of the structure and functions of a cell. Later, cytology turned into a broad branch of biology and became more practical and applied, but the essence of the term remained the same - the study of the cell and its functions.
12. Formulate and write down the main ideas of § 2.1.
People learned about the existence of cells after the invention of the microscope. The first primitive microscope was invented by Z. Jansen.
R. Hooke discovered cork cells.
A. Van Leeuwenhoek, having improved the microscope, observed living cells and described bacteria.
K. Baer discovered the mammalian egg.
The nucleus was discovered in plant cells by R. Brown.
M. Schleiden and T. Schwann were the first to formulate the cell theory. “All organisms consist of the simplest particles - cells, and each cell is an independent whole. In the body, cells act together to form a harmonious unity.”
R. Virchow substantiated that all cells are formed from other cells through cell division.
By the end of the 19th century. The structural components of cells and the process of their division were discovered and studied. The emergence of cytology.
Basic provisions of modern cell theory:
cell is a structural and functional unit of all living organisms, as well as a unit of development;
cells have a membrane structure;
nucleus - the main part of a eukaryotic cell;
cells reproduce only by division;
The cellular structure of organisms indicates that plants and animals have the same origin.

– an elementary structural and functional unit of all living organisms. It can exist as a separate organism (bacteria, protozoa, algae, fungi) or as part of the tissues of multicellular animals, plants and fungi.

History of the study of cells. Cell theory.

The life activity of organisms at the cellular level is studied by the science of cytology or cell biology. The emergence of cytology as a science is closely related to the creation of cell theory, the broadest and most fundamental of all biological generalizations.

The history of the study of cells is inextricably linked with the development of research methods, primarily with the development of microscopic technology. The microscope was first used to study plant and animal tissues by the English physicist and botanist Robert Hooke (1665). While studying a section of the elderberry core cork, he discovered separate cavities - cells or cells.

In 1674, the famous Dutch researcher Anthony de Leeuwenhoek improved the microscope (magnified 270 times) and discovered single-celled organisms in a drop of water. He discovered bacteria in dental plaque, discovered and described red blood cells and sperm, and described the structure of the heart muscle from animal tissues.

• 1827 - our compatriot K. Baer discovered the egg.
• 1831 - English botanist Robert Brown described the nucleus in plant cells.
• 1838 - German botanist Matthias Schleiden put forward the idea of ​​the identity of plant cells from the point of view of their development.
• 1839 - German zoologist Theodor Schwann made the final generalization that plant and animal cells have a common structure. In his work “Microscopic Studies on the Correspondence in the Structure and Growth of Animals and Plants,” he formulated the cell theory, according to which cells are the structural and functional basis of living organisms.
• 1858 - German pathologist Rudolf Virchow applied the cell theory in pathology and supplemented it with important provisions:

1) a new cell can only arise from a previous cell;

2) human diseases are based on a violation of the structure of cells.

Cell theory in its modern form includes three main provisions:

1) cell - the elementary structural, functional and genetic unit of all living things - the primary source of life.

2) new cells are formed as a result of the division of previous ones; A cell is an elementary unit of living development.

3) the structural and functional units of multicellular organisms are cells.

Cell theory has had a fruitful influence on all areas of biological research.

1. Who owns the discovery of the cell? Who is the author and founder of the cell theory? Who supplemented the cell theory with the principle: “Every cell is from a cell”?

R. Virchow, R. Brown, R. Hooke, T. Schwann, A. van Leeuwenhoek.

The discovery of the cell belongs to R. Hooke.

The principle “Every cell is from a cell” was supplemented by R. Virchow to the cell theory.

2. Which scientists made a significant contribution to the development of ideas about the cell? Name the merits of each of them.

● R. Hooke – discovery of the cell.

● A. van Leeuwenhoek - discovery of single-celled organisms, red blood cells, sperm.

● Ya. Purkin - discovery of the nucleus in an animal cell.

● R. Brown - discovery of the nucleus in plant cells, the conclusion that the nucleus is an essential component of the plant cell.

● M. Schleiden - evidence that the cell is the main structural unit of plants.

● T. Schwann – the conclusion that all living beings consist of cells, the creation of the cellular theory.

● R. Virchow – addition of the cell theory with the principle “Every cell is from a cell.”

3. Formulate the basic principles of cell theory. What contribution did cell theory make to the development of the natural science picture of the world?

1. A cell is an elementary structural and functional unit of living organisms, possessing all the signs and properties of a living thing.

2. The cells of all organisms are similar in structure, chemical composition and basic manifestations of life activity.

3. Cells are formed by division of the original mother cell.

4. In a multicellular organism, cells specialize in function and form tissues. Organs and organ systems are built from tissues.

Cell theory had a significant impact on the development of biology and served as the foundation for the further development of many biological disciplines - embryology, histology, physiology, etc. The basic principles of cell theory have retained their significance to this day.

4. Using the knowledge gained from studying biology in grades 6-9, use examples to prove the validity of the fourth proposition of the cell theory.

For example, the inner (mucosal) lining of the human small intestine includes cells of the integumentary epithelium, which ensure the absorption of nutrients and perform a protective function. Glandular epithelial cells secrete digestive enzymes and other biologically active substances. The middle (muscular) membrane is formed by smooth muscle tissue, the cells of which perform a motor function, causing the mixing of food masses and their movement towards the large intestine. The outer shell is formed by connective tissue that performs a protective function and provides attachment of the small intestine to the posterior wall of the abdomen. Thus, the small intestine is formed by various tissues, the cells of which are specialized to perform certain functions. In turn, the small intestine, together with other organs (esophagus, stomach, etc.) forms the human digestive system.

The cover cells of the leaf skin perform a protective function. Guard and secondary cells form stomatal apparatuses that provide transpiration and gas exchange. Chlorophyll-bearing parenchyma cells carry out photosynthesis. The veins of the leaf include fibers that impart mechanical strength and conductive tissues, the elements of which ensure the transport of solutions. Consequently, a leaf (plant organ) is formed by different tissues, the cells of which perform certain functions.

5. Before the 1830s. It was widely believed that cells were “bags” with nutritious juice, while the main part of the cell was considered to be its shell. What could be the reason for this idea of ​​cells? What discoveries contributed to changing ideas about the structure and functioning of cells?

The magnifying power of microscopes of that time did not allow a detailed study of the internal contents of cells, but their membranes were clearly visible. Therefore, scientists paid attention primarily to the shape of cells and the structure of their membranes, and considered the internal contents to be “nutritional juice.”

Changing the existing ideas about the structure and functioning of cells was primarily facilitated by the work of J. Purkin (discovered the nucleus in the egg of birds, introduced the concept of “protoplasm”) and R. Brown (described the nucleus in plant cells, came to the conclusion that it is an essential part of the plant cells).

6. Prove that the cell is the elementary structural and functional unit of living organisms.

A cell is an isolated, smallest structure that has all the basic characteristics of a living thing: metabolism and energy, self-regulation, irritability, the ability to grow, develop and reproduce, store hereditary information and transmit it to daughter cells during division. Individual components of the cell do not exhibit all these properties together. All living organisms are made up of cells; outside the cell there is no life. Therefore, the cell is the elementary structural and functional unit of living organisms.

7*. The size of most plant and animal cells is 20-100 microns, i.e. the cells are quite small structures. What determines the microscopic size of cells? Explain why plants and animals do not consist of one (or several) huge cells, but of many small ones.

To maintain vital activity, a cell must constantly exchange substances with its environment. The cell's needs for the supply of nutrients, oxygen, and the removal of final metabolic products are determined by its volume, and the intensity of transport of substances depends on the surface area. Thus, with an increase in cell size, their needs increase in proportion to the cube (x 3) of the linear size (x), and the transport of substances “lags behind”, because increases in proportion to the square (x 2). As a result, the speed of vital processes in cells is inhibited. Therefore, most cells are microscopic in size.

Plants and animals consist of many small cells, and not one (or several) huge ones because:

● It is “beneficial” for cells to be small in size (the reason for this is covered in the previous paragraph).

● One or a few cells would not be enough to perform all the specific functions that underlie the life of such highly organized organisms as plants and animals. The higher the level of organization of a living organism, the more types of cells are included in its composition and the more pronounced cellular specialization is.

● In a multicellular organism, the cellular composition is constantly being renewed - cells die and are replaced by others. The death of one (or several) huge cells would lead to the death of the entire organism.

*Tasks marked with an asterisk require students to put forward various hypotheses. Therefore, when marking, the teacher should focus not only on the answer given here, but take into account each hypothesis, assessing the biological thinking of students, the logic of their reasoning, the originality of ideas, etc. After this, it is advisable to familiarize students with the answer given.

Question 1. Who developed the cell theory?

The cell theory was formulated in the mid-19th century. German scientists Theodor Schwann and Matthias Schleiden. They summarized the results of many discoveries known at that time. The main theoretical conclusions, called the cell theory, were outlined by T. Schwann in his book “Microscopic studies on the correspondence in the structure and growth of animals and plants” (1839). The main idea of ​​the book is that plant and animal tissues are made up of cells. A cell is a structural unit of living organisms.

Question 2. Why was the cell called a cell?

Dutch scientist Robert Hooke, using his design of a magnifying device, observed a thin section of cork. He was amazed that the cork turned out to be built from cells that resembled a honeycomb. Hooke called these cells cells.

Question 3. What properties do all cells of living organisms share?

Cells have all the characteristics of life. They are capable of growth, reproduction, metabolism and energy conversion, have heredity and variability, and respond to external stimuli.

2.1. Basic principles of cell theory

Searched on this page:

• who developed the cell theory
• what properties do all cells of living organisms have in common?
• why is a cell called a cell
• What properties do all cells of living organisms have in common?
• who developed the cell theory?