Cell: a history of study

The basic structural and functional unit of any living organism is the cell. Only viruses, whose position in the living system is not entirely clear, lack a cellular structure. A cell can exist either as a separate (unicellular) organism (bacteria, protozoa, many algae and fungi), or as part of the body of multicellular animals, plants and fungi. But even in the largest organisms, each of its billions of cells is relatively independent and performs a specific function.

The history of the study of cells is inextricably linked with the development of research methods, primarily with the development of microscopic techniques. The first simple microscope appeared at the end of the 16th century. It was built in Holland. It is known about the device of this magnifying device that it consisted of a tube attached to a stand and having two magnifying glasses. The first to understand and appreciate the great importance of the microscope was the English physicist and botanist Robert Hooke. He was the first to use a microscope to study plant and animal tissues. In 1665, Robert Hooke first described the structure of some plant tissues, in particular a cork, consisting of small cells bounded by partitions, in his essay "Micrography, or some physiological descriptions of the smallest bodies made by means of magnifying glasses." Thus the cage was opened. Studying a cut prepared from cork and elderberry core, R. Hooke noticed that they include many very small formations, similar in shape to honeycomb cells. He gave them the name of a cell or cell The term "cell" was established in biology, although R. Hooke did not see the cells themselves, but the shells of plant cells.

Through the efforts of many scientists, mainly in the 19th and the first half of the 20th centuries, a special science of the cell was formed, called cytology.

The optical instrument acquired the value of a valuable scientific instrument thanks to the improvements of the famous Dutch explorer Anthony van Leeuwenhoek. His microscope made it possible to see living cells at a magnification of 270 times.

The study of the internal structure of living organisms is associated with the invention of the microscope. In 1665, the English scientist Robert Hooke, examining a thin section of wood cork with the help of a microscope designed by him, made an amazing discovery. He discovered that wood cork does not consist of a solid mass, but of very small cells separated by partitions. R. Hooke called these cells "sellula" - cells. Subsequently, a number of scientists, examining the tissues of various plants and animals under a microscope, also determined that they all consist of cells. So, the Dutch scientist A. Leeuwenhoek in 1680 discovered red blood cells - erythrocytes - in the blood.

For a long time, the main part of the cell was considered its shell. Only at the beginning of the XIX century. scientists drew attention to the semi-liquid gelatinous contents that fill the cell. In 1831, the English botanist B. Brown discovered the nucleus in cells, and in 1839 the Czech scientist J. Purkinė suggested calling the liquid contents of the cell protoplasm. Thus, at the beginning of the XIX century. scientists came to the conclusion that the organisms of plants and animals are composed of cells. In 1838-1839. German scientists - botanist M. Schleiden and zoologist T. Schwann - having summarized the data available at that time, developed the foundations of the cell theory, which was later developed by many researchers. The German physician R. Virchow proved that there is no life outside of cells, that the main component of the cell is the nucleus, and that cells are formed only from cells by their division. Further improvement of technology, the creation of an electron microscope and the methods of molecular biology made it possible to penetrate deeper into the study of the cell, to know its complex structure and the variety of biochemical processes occurring in it.

Question 1. Tell us about the history of the discovery of the cell.
The discovery of the cellular structure of living organisms became possible thanks to the advent of the microscope. Its prototype was invented in 1590 by the Dutch glass grinder Zachary Jansen. The first microscope is known to have consisted of a tube attached to a stand and had two magnifying glasses.
The importance of the microscope for studying the structure of sections of plant and animal objects was first appreciated by the English physicist and botanist Robert Hooke. In 1665, on sections of cork, he discovered structures resembling honeycombs, and called them cells or cells. However, Hooke was wrong, believing that cells are empty, and living matter is cell walls.
Dutch naturalist Anthony van Leeuwenhoek in the second half of the 17th century. improved the microscope and was the first to see living cells. He observed and drew a number of protozoa, spermatozoa, bacteria, erythrocytes and even their movement in capillaries.

Question 2. By whom and when was the cell theory first formulated?
The study of plant and animal cells made it possible to generalize all the features of their structure. In 1838, M. Schleiden created the theory of cytogenesis (cell formation). His main merit is to raise the question of the origin of cells in the body. In 1839, T. Schwann, based on the work of M. Schleiden, created a cell theory. The main provisions of the cell theory (M. Schleiden and T Schwann):
1) all tissues are made up of cells;
2) plant and animal cells have common principles of structure, tk. arise in the same way;
3) each individual cell is independent, and the activity of the organism is the sum of the vital activity of individual cells.
In 1858, R. Virchow also paid great attention to the further development of the cellular theory. He not only brought together all the numerous disparate facts, but also convincingly showed that cells are a permanent structure and arise only through the reproduction of their own kind - “every cell comes from another cell as a result of division, just like a plant is formed from a plant, and from animals animals”, i.e. discovered cell division.

Question 3. List the current provisions of cell theory.
In our time, cytology, using the achievements of genetics, molecular and physico-chemical biology, is developing very rapidly. And although the main provisions of the theory of T. Schwann and M. Schleiden remain relevant, the data obtained made it possible to form a deeper understanding of the structure and functions of the cell. Based on them, the modern cellular theory was formulated. We list its main provisions:
1) a cell is a unit of structure, functioning, reproduction and development of living organisms;
2) the cells of all organisms are similar in structure and chemical composition;
3) cell reproduction occurs by dividing the mother cell;
4) cells of multicellular organisms are specialized: they perform different functions and form tissues.

Question 4. Describe the importance of cell theory for the development of biology.
According to philosophers who studied the history of science (for example, Friedrich Engels), the cell theory is one of the greatest discoveries of the 19th century. She played a huge role in the development of not only biology, but also natural science in general. Protozoa, bacteria, many fungi and algae are cells that exist separately from each other. The body of all multicellular organisms - plants, fungi and animals - is built from more or less cells, which are the elementary structures that make up a complex organism. Regardless of whether a cell is an integral living system or a part of it, it has a set of features and properties common to all cells.
The cell theory for the first time unequivocally pointed to the unity of the living world. With its appearance, the gap between the animal kingdom and the plant kingdom disappeared. On the basis of cell theory in the middle of the XIX century. Cytology arose - a science that studies the structure and functions of the cell.
Think for which representatives of the organic world the concepts of "cell" and "organism" coincide.
A cell is the basic structural, functional and genetic unit of the organization of living things, an elementary living system. A cell can exist as a separate organism.
The concepts of "cell" and "organism" coincide in the case when we are talking about unicellular organisms. These include prokaryotes, or non-nuclear ones (in particular, bacteria), and from eukaryotes, or nuclear ones, the simplest ones (such as ciliates shoe, chlamydomonas, green euglena). Their body consists of one cell, which implements all the functions of the body - metabolism, irritability, reproduction, movement. These functions are facilitated by a variety of organelles, including special ones (for example, flagella and cilia provide movement). Unicellular organisms are often able to form clusters - colonies. However, the concept of a “multicellular organism” is still inapplicable to a colony, since its constituent cells have the same type of structure (they are not subdivided into tissues), weakly interact with each other and, being isolated from the colony, continue to exist independently and multiply without any problems.

We have repeatedly mentioned that one or another of the listed researchers noticed nuclei in the cells.

Since in the work of Schleiden, to which we turn next, the nucleus is given special importance, then, deviating from the chronological presentation, we will consider here the history of the discovery of this most important part of the cell. It was the nucleus that helped Schwann to compare animal and plant cells, and therefore the discovery of the nucleus marks the most important stage in the development of the theory of the cell.

The nuclei were first seen in the erythrocytes of fish by Löwenhoek in 1700 and depicted them in the figure. Later on the same object - erythrocytes of many vertebrates and invertebrates - Hewson (1777) sketched nuclei. The significance of this education in that early period of the birth of microscopy, of course, could not be assessed either by the authors themselves or by their contemporaries. Fontana in his study of viper venom, depicting the epithelial cells of the epidermis and erythrocytes, draws in the cells of the nucleus and briefly mentions “them in the text; but even at that time (Fontan's work appeared in 1781), when the microscopic examination of animal tissues was just beginning, Fontan's discovery could not be understood.

At the same time, some researchers observed nuclei in eggs. Cavolini (Filippo Cavolini, 1756-1810) saw nuclei in fish eggs (1787); and Poly (Poli, 1791) noted the nuclei in the eggs of mollusks. Their observations passed without a trace, without drawing attention to themselves.

In a study on the egg of birds (1825), Purkinė described the "embryonic vesicle" (vesicula germinativa). It was the nucleus of a bird egg. According to Purkine's description, it is “a compressed spherical bubble, dressed in the thinnest shell. It contains its own lymph, is incorporated into the white mammillary tubercle, and is full of generative power, which is why I have called it the "embryonic vesicle." Purkyne attached great importance to the education he discovered; after him, subsequent researchers no longer ignored this mysterious "bubble". The discovery of Purkinet, thus, did not pass without a trace, like the observations of Cavolini and Poli, but the meaning of the “germinal vesicle” remained unclear for a long time, since in understanding the parts of the egg, from the point of view of the concept of the “cell”, the correct path was outlined only after the studies of Schwann.

In plants, the first image of the cell nucleus was made by Bauer in 1802, but this drawing was published only in 1830 (J. Baker, 1949). Meyen (1830) shows a nucleus in one figure. In a study on the marchantia, Mirbel (1831-1832) also depicts a nucleus, giving it the name of a ball; the French botanist Brognard (Adolphe Brogniart, 1801-1876) also saw him. But these first observations of nuclei in plant cells were not appreciated by the observers themselves and also did not attract attention.

The recognition of the nucleus as an indispensable part of the plant cell is the merit of the English botanist Robert Brown (Robert Brown, 1773-1858).

Starting his botanical work with a description of the collections made during a trip to Australia, Brown then moves on to the study of the anatomical structure of plants. He did not set purely morphological problems in his work; anatomical studies for him are a guide to the study of plant taxonomy, but in these works Brown makes outstanding botanical discoveries regarding reproduction in plants. In 1833, Brown's work "On the organs and method of fertilization in orchids" was published (reported to the Linnean Society in London as early as November 1831). Brown writes in this article that in each cell of the epidermis he observed "a single rounded areola, usually darker than the cell membrane. This areola is more or less granular, slightly convex, and although it appears to lie on the surface, it is actually covered by the outer plate of the cell. Its position in the cell is not constant; often, however, in or near the center” (p. 710). This areola, or nucleus (nucleus) of the cell, as Brown otherwise refers to this formation, was observed by him not only in the cells of the epidermis; he saw the nucleus in the parenchyma, in the inner cells of plant parts, "especially when they are free of granular matter." Brown, though cautiously, suggests that the nucleus is an ordinary component of the cell. He does not have a categorical statement that the nucleus is an obligatory organelle of the cell; likewise, Brown does not give images of cell nuclei in his work. Nevertheless, in Brown's research, for the first time, the nucleus is not mentioned as a random formation in the cell, but appears as some kind of essential part that is important for the life of the cell.

Meyen, the author of "Phytotomy" - a work that was discussed earlier - in a later manual "A New System of Plant Physiology" (1837-1839) mentions the nucleus as a permanent part of the cell, the meaning of which remains mysterious. Actually, only the work of Negeli (S. Nageli, 1844) proved the universal distribution of cell nuclei not only in flowering plants, but also in the cells of algae, fungi, mosses and other lower plants.

In the histology of animals, the term "nucleus" was introduced by Valentin. In the report “On the fine structure of the sense organs” (1836), Valentin wrote about the epithelium of the conjunctiva: “It consists of rhomboid or square rounded cells lying closely next to each other, the boundaries of which are formed by simple threadlike lines; in each cell, without exception, there is a somewhat darker and more compact nucleus (nucleus) of a round or oblong-rounded shape. For the most part, it occupies the middle of the cell, consists of a fine-grained substance, but inside it contains a completely round body, which, following the same pattern, forms a kind of second nucleus inside it ”(p. 143). This description shows that Valentin clearly observed the nuclei of epithelial cells. Inside the nucleus, Valentine saw the nucleolus; this was apparently the first description of this intranuclear structure.

A clear description and image of nuclei in epithelial cells was given by Henle (1837). Baker (1949) correctly notes that the work of Valentin and Henle begins the era of nuclear cells in animal histology.

In 1838, an article by the young botanist Schleiden appeared in Muller's Archiv under the title "Materials for Phytogenesis" (Beitrage zur Phytogenesis). This work is traditionally considered the most important stage in the development of the cellular theory, and its author, along with Schwann, is recognized as the creator of the cellular theory. The significance of Schleiden in the history of the cellular theory is indisputable, but in educational, popular, and sometimes in historical literature, this significance is covered superficially and incorrectly. Schleiden is sometimes credited with almost discovering plant cells, therefore. it is necessary to understand what is really the significance of this scientist in the history of cellular teaching, where is the truth in the legend that has developed around his work and traditionally passes from textbook to textbook.

Matthias Schleiden(Matthias Jacob Schleiden, 1804-1881) is the largest representative of German botany in the middle of the last century. Initially, he graduated from the Faculty of Law and practiced advocacy. Having no success in this activity, Schleiden in 1831 gave up law and began to study medicine and the natural sciences. From 1840 he was a professor of botany in Jena, where he remained until 1862. This is the main period of Schleiden's creative activity. In 1842, his major work "Fundamentals of Scientific Botany" was published, which played an important role in the direction of further botanical research. Instead of natural philosophical reasoning, Schleiden requires the introduction into botany of exact methods for studying the structure and function of plants; he especially emphasized the need for attention to the history of development, in which he saw the key to solving many controversial problems. Philosophical positions of Schleiden, stated by him in his writings, are not original and reveal the imprint of Kantian philosophy. From 1862 to 1864, Schleiden was a professor of anthropology in Dorpat (now Tartu, Estonian SSR), in 1864 he left Dorpat because of a clash with church circles and at the same time stopped teaching. As the author of not only a number of scientific papers, but also many popular works, Schleiden was widely known.

“Materials for Phytogenesis” is the second work of Schleiden, who was then still a novice botanist. It is an article, about 40 pages in size, to which two tables are attached. The general basic law of the human mind, - this is how Schleiden begins his work, - the law that determines its irresistible desire for unity in cognition and the establishment, both in general in science and in the field of organisms, of analogy for both large departments - the kingdom of animals and plants, - repeatedly prompted deal with this subject. So many minds have been occupied with it, but - this cannot be denied - all the attempts so far made in this respect have failed and have been delusions. The reason lies in the fact that the concept of the individual, in the sense that it is applied in animal nature, has no application in the plant world. The greatest thing that can be said about the individual in this sense is in the lowest plants, some algae and fungi, consisting of only one cell. But each more highly developed plant is an aggregate of completely individualized closed individualities ... which are cells” (p. 137). We deliberately quoted this long quotation, which is the beginning of Schleiden's article, to show how alien to him was the idea of ​​the unity of the microscopic structure of animals and plants, expressed in the cellular structure. Meanwhile, it is this idea that is the cornerstone of the cellular theory, one of the co-authors of which is usually considered Schleiden.

For a correct assessment of Schleiden's work, one must remember the position of the cellular theory in botany by 1837, when Schleiden completed his work. The completely false idea that Schleiden proved the universal distribution of cells in plants, or even discovered cells in plants. This is a distortion of the actual historical development of science. By the beginning of the thirties of the last century, a complete idea of ​​the cell as the elementary structure of the plant world was being created in botany; Schleiden in his work takes this position as an unshakably established conclusion. Even such non-cellular parts of plants, as it seemed earlier, as water-bearing vessels of wood, by this time are considered as modified, peculiarly differentiated and merged cells. Schleiden did not have to establish the universal distribution of cells in plants: the establishment of this position was, as we have seen, the collective success of a number of works by a numerous galaxy of botanists in the first quarter of the last century.

K. A. Timiryazev (1920) rightly wrote about the expression “discovery of the cell”: “But the fact is that no one discovered the cell” (p. 79), emphasizing that the “discovery” of the cell is not the merit of some certain scientist. It is also not true that Schleiden, as Aschoff (1938) writes, developed the doctrine of "the all-embracing construction from cells of all plants" (p. 177). And in this regard, K. A. Timiryazev is right, who wrote: “Schleiden is generally considered to be the creator of this doctrine of the cell, which turned out to be so rich in the most fruitful generalizations. But this is hardly fair ... Schleiden, an eloquent, passionate opponent of routine and stagnation, could rightfully say about himself, as Bacon once did, that he is a trumpeter, herald, buccinator, announcing the emergence of this doctrine, but the factual data substantiating it already existed earlier…” (p. 75). It is characteristic that Unger (Unger, 1846) in his fundamentals of botany, outlining the position of the cell as the universal elementary structure of organisms, points out Schwann and Kölliker in the literary reference, without even mentioning Schleiden in this aspect.

The very concept of the cell in Schleiden does not differ from the ideas that took shape earlier and were reflected in Meyen's textbook (1830) even before Schleiden even began to study botany. At the level with these ideas, Schleiden took the cell for a bubble or a chamber, delimited by a shell, inside which the contents can be located. This "content" of the cell (future protoplasm!) also attracted the attention of Meyen, who devoted a great deal of research to it, but did not understand the significance of this main component of cells. Schleiden also saw the protoplasm of plant cells, but he did not understand the meaning of the “contents” of the cell. For him, it is gum (Gummi) or jelly (Gallerte). Part of the protoplasm Schleiden attributed to the cell wall. The latter, in his opinion, consists of two layers, between them is the cell nucleus - “ditoblast”, which never lies inside the cell, but is always enclosed in the cell wall “in such a way that the cell wall splits into two plates, of which one passes outside and the other inside the cytoblast. The one that runs from the inside is usually softer and more gelatinous” (p. 142). From Schleiden's drawings, it is obvious that he took the parietal layer of protoplasm of plant cells for the "inner layer of the cell wall".

What task did Schleiden set in his work? “Each cell,” he writes, “leads a double life: a completely independent one, associated only with its own development, and another dependent one, since it is an integral part of the plant. However, it is easy to see that both for plant physiology and for comparative physiology, the life processes of individual cells should generally be in the first place, should represent an inevitable basis, and in this case, the question is first of all put forward: how does this peculiar small organism actually occur? cell?" (p. 138). This task, the genesis of the cell, is the basis of Schleiden's paper. The genetic moment in this sense was put forward before, but it cannot be denied that Schleiden, in accordance with his time, posed this problem more clearly than his predecessors.

Answering the question posed, Schleiden develops his theory of cell formation. In this theory, the central role in the development of new cells is assigned to the nucleus. As we have seen, it was discovered long before Schleiden's work, but did not receive any definite interpretation. According to Schleiden, the nucleus is a "cytoblast" - the cell's former. The theory of cell formation developed by Schleiden can be briefly characterized as follows.

In the gum, adjacent from the inside to the walls of pre-existing cells, grains are formed; Schleiden calls them mucus and believes that these grains, by condensation, form nucleoli, and then a nucleus is formed, which appears as a granular sediment around the nucleolus. On the surface of the nucleus, on the one hand, a shell is again formed from the "mucus"; it delimits the cytoblast, and thus a walled space arises, where the nucleus is enclosed in the thickness of the wall. This space is the new cell. Therefore, according to Schleiden, daughter cells arise inside mother cells. The number of new cells that can develop in one maternal cell, as well as the fate of this maternal educational cell, is not discussed by Schleiden.

Such is the essence of the theory of cell formation, the essence of "Schleiden's excellent research, which shed so much light on this area," - a characterization of Schleiden's work given by Theodor Schwann. As was soon shown, Schleiden's theory is based on misinterpreted observations. It was this incorrect theory of cell formation that his friend Schwann took over from Schleiden, and it was the weakest point in Schwann's teaching. Sacks, in his history of botany, characterizes Schleiden's theory with the following harsh words: "Schleiden's theory of cell formation arose from an incomprehensible confluence of obscure observations and preconceived opinions, moreover, it strongly resembles mainly the old theories of Sprengel and Treviranus" (p. 76). Schleiden himself stubbornly defended his theory of cytogenesis and cited it even in the 4th ed. "Fundamentals of Scientific Botany" (1861).

In his article, Schleiden, in addition to the considered theory of cell formation, deals with the development of thickenings on the walls of spiral vessels and develops theoretical arguments about the work of plants. Schleiden's work does not contain anything fundamentally new in this section, and since this part of the article is not directly related to our topic, there is no need to dwell on it.

What assessment should be given in the historical aspect of Schleiden's role in the development of cellular theory? Martin Heidenhain (M. Heidenhain, 1899) at the end of the last century noted the incorrectness of the idea of ​​an equivalent value in the history of the cellular theory of Schleiden and Schwann. Later, this question was resolutely raised again on the basis of a critical analysis of the literature by the Czech histologist Studnichka (1933), a great connoisseur of the history of cell theory. Indeed, the traditional comparison of the names of Schleiden and Schwann, usually put forward as "co-authors" of the cell theory, is not justified by a careful study of the sources. Schleiden was not a co-author of the cell theory; he, as we have seen, was completely alien to the main idea of ​​this theory - the unity of the microscopic elementary structure of animals and plants; he is not the creator of the cellular doctrine in the field of botany, since the main provisions of this doctrine were developed before him. This must be emphasized, since in literature, both foreign and ours, a “legend” has been created around the name of Schleiden, of which there are so many in the history of science due to insufficient acquaintance with the originals. Studnichka, in the above-cited article about Schleiden, cited extracts from several dozen foreign manuals on histology and biology, and even from special articles on the history of cellular science, where the role of Schleiden is completely misrepresented and the legend is repeated that science owes Schleiden the discovery of the cellular structure in plants, that Schleiden and Schwann created the cell theory, etc. To the list of unjustified, and sometimes simply ridiculous statements about the role of Schleiden, which Studnich cited, one can, unfortunately, add a considerable list of quotations from newer textbooks and even special works, including the number of works claiming the significance of historical works both in our and in foreign literature. The historical role of Schleiden's work is undeniable, but this role is different from what is usually covered. Schleiden is credited with the introduction of the genetic approach into the theory of tissues and cells. Attempts of a similar approach were made before Schleiden (Wolf, Mirbel, Sprengel, Treviranus; in animal histology - Valentin), but at that time they could not be as effective as Schleiden's work, which appeared when the idea of ​​the cell as the basic structure of plants was already common. Without the genetic approach, Schwann could not have created a coherent cellular theory, substantiated by convincing data for that time. Only by referring to the history of the development of tissues and cells, Schwann was able to show the "correspondence" of various elementary structures, could prove their homology. Schleiden's work, of course, played a significant role in directing Schwann's thought to a similar path of research.

But that's not all. In order to be able to convincingly show their homology by referring to the history of the development of elementary structures, it was necessary to find a guiding feature and, taking it as a leading link, unravel the tangle of complex relationships between elementary structures in animal tissues. Schwann learned this guiding feature from Schleiden. This is the core. Cells in different tissues may look very different from each other, but the similarity of the nuclei is striking, helping to homologate outwardly dissimilar formations. The nucleus was known both in plant cells and in animal structures before Schleiden. But only in his work did the nucleus acquire the significance of the main feature of the developing cell. This sign served as a lever for Schwann, grasping which he was able to create a cell theory.

This is the significance of Schleiden in the history of cellular science. He cannot be placed next to Schwann, he was not a co-author of the cellular theory, but his work was a necessary link in the chain of research that prepared the material, without which the genius of Schwann, perhaps, would have been powerless to make the generalizations he formulated in the form of a cellular theory. Virchow (1859) correctly expressed this by pointing out that Schwann stood "on the shoulders" of Schleiden.

MUNICIPAL BUDGET EDUCATIONAL INSTITUTION "PODBELEVSKY SECONDARY SCHOOL"

HISTORY OF THE DISCOVERY OF THE CELL

Completed by: Aleshkina Nadezhda Vladimirovna,

5th grade student

Head: Krasnoshchekova Irina Nikolaevna,

chemistry and biology teacher

2016

Table of contents ( content) page

Introduction………………………………………………………………………….3

Chapter 1. The history of the invention of the microscope……...………………………3

Chapter 2

Practical part….. …………………………………………………….9

Conclusions……...…………………………………………………………………..10

Literature used…….………………………………………………11

INTRODUCTION

I'm in the 5th grade. This year we started to study a new subject - biology. Biology is the science of living nature. Biologists study the diversity of living beings, the structure of their bodies and the work of various organs, the reproduction and development of organisms, their relationship with each other and with inanimate nature.

All living beings have a cellular structure. Among them there are unicellular and multicellular organisms. Most living cells have three main parts: membrane, cytoplasm and nucleus.

At one of the biology lessons, we examined ready-made micropreparations of various cells under a microscope. At extracurricular activities (Secrets of the Microworld), we examined the infusoria-shoe, watched how it moves, prepared micropreparations ourselves from onion peel and tomato pulp. And in them we could see the nucleus, cytoplasm and membrane.

I became interested in how mankind managed to find out what organisms are made of, and how it became possible to see the cell.

Objective:find out how the invention of the microscope influenced the discovery of the cell.

Tasks:

- to study the history of the invention of the microscope;

- to study the history of the discovery of the cell;

- conduct a survey;

- to conduct an experiment;

- to conclude .

Object of study : cell

Subject of study : cell opening

Methods Used Keywords: analysis, experiment, observation, conclusions.

Chapter 1. HISTORY OF THE INVENTION OF THE MICROSCOPE

The invention of the microscope, an instrument so important for all science, is primarily due to the influence of the development of optics. Some optical properties of curved surfaces were known even to Euclid (300 BC) and Ptolemy (127-151), but their magnifying power did not find practical application. In this regard, the first glasses were invented by Salvinio deli Arleati in Italy only in 1285. In the 16th century, Leonardo da Vinci and Maurolico showed that small objects are best studied with a magnifying glass.

Rice. 1. The first microscope

The first microscope was created only in 1595 by Zaharius Jansen (Jansen). The invention consisted in the fact that Zacharius Jansen mounted two convex lenses inside one tube, thereby laying the foundation for the creation of complex microscopes. Focusing on the object under study was achieved by a retractable tube. The magnification of the microscope was from 3 to 10 times. And it was a real breakthrough in the field of microscopy! Each of his next microscope, he significantly improved.

During this period (XVI century) Danish, English and Italian research instruments gradually began to develop, laying the foundation for modern microscopy.

The rapid spread and improvement of microscopes began after Galileo, improving the telescope he designed, began to use it as a kind of microscope (1609-1610), changing the distance between the objective and the eyepiece.

Later, in 1624, having achieved the production of short-focus lenses, Galileo significantly reduced the dimensions of his microscope.

In 1625, a member of the Roman "Academy of the Vigilant" I. Faber proposed the term"microscope". The first successes associated with the use of the microscope in scientific biological research were achieved by Hooke, who was the first to describe the plant cell (about 1665). In his book Micrographia, Hooke described the structure of a microscope. From now on a new world of living beings was opening up, more diverse and infinitely more original than the world we see.(http://www.vita-club.ru/micros1.htm)

Chapter 2. HISTORY OF THE DISCOVERY OF THE CELL

A cell is an elementary structural and functional unit of an organism that has all the basic features of a living thing. Cells are capable of multiplying, growing, exchanging matter and energy with the environment, responding to changes occurring in this environment. Each cell contains hereditary material, which contains information about all the signs and properties of this organism.( )

R is. 2. Robert Hooke.

The English scientist Robert Hooke (1635-1703) first saw the cells of a plant.

This happened in 1665. It happened like this: Hooke examined a thin section of a linden cork with a magnification of 30 times. He discovered that cork is made up of many small cavities, chambers, which he called "cells." It was he who introduced the concept of "cell" into science.(Pleshakov A.A., Vvedensky E.L. Biology. Introduction to Biology: a textbook for grade 5 general educational institutions / M.: Russian Word - Textbook LLC, 2014.)True, these were not living, but already dead cells. Hooke believed that the cells themselves are emptiness, and the contents of a living organism are enclosed in a frame (cell wall).

Fig.3 Microscope R. Hooke Fig.4. Cork cells studied by Robert Hooke

Soon the cellular structure of plants was confirmed by the Italian physician and microscopist M. Malpighi and the English botanist N. Gru. Their attention was drawn to the shape of the cells and the structure of their membranes. As a result, the idea of ​​cells was given as "sacs" or "vesicles" filled with "nutritive juice". ( )

DutchmanAnthony WangLeeuwenhoekdescribed the amazing miracles that he discovered with his microscope in a drop of water, in an infusion of pepper, in the mud of a river, in the hollow of his own tooth. Leeuwenhoek, using a microscope, discovered and sketched spermatozoa, various protozoa, details of the structure of bone tissue (1673-1677).

“With the greatest amazement, I saw in the drop a great multitude of small animals moving briskly in all directions, like a pike in water. The smallest of these tiny animals is a thousand times smaller than the eye of an adult louse.

The best Leeuwenhoek magnifiers were magnified 270 times. With them, he saw for the first time the blood corpuscles, the movement of blood in the capillary vessels of the tail of the tadpole, the striation of the muscles. He opened infusoria. For the first time he plunged into the world of microscopic unicellular algae, where the border between animal and plant lies; where a moving animal, like a green plant, has chlorophyll and feeds by absorbing light; where the plant, still attached to the substrate, has lost chlorophyll and is ingesting bacteria. Finally, he even saw bacteria in great variety. But, of course, at that time there was still no remote possibility of understanding either the significance of bacteria for humans, or the meaning of the green substance - chlorophyll, or the boundary between plant and animal. ( )

The descriptions of these "animalcuses" ("animals"), as he called them, made the Dutchman world-famous. But most importantly, Leeuwenhoek's discoveries aroused interest in the study of the living microcosm.(Encyclopedia for children. V.2. Biology. - 5th ed. / Editor-in-chief M.D. Aksenova. - M .: Avanta +, 2001)

R
fig.5 by Antonia van Leeuwenhoek

In 1693, during the stay of Peter I in Delphi, A. Leeuwenhoek demonstrated to him how blood moves in the fin of a fish. These demonstrations made such a great impression on Peter I that, upon returning to Russia, he created a workshop for optical instruments. Petersburg Academy of Sciences was organized in 1725. Talented masters I.E. Belyaev, I.P. Kulibin made microscopes, in the design of which academicians L. Euler, F. Epinus took part.

Fig.6 Microscope made by Russian craftsmen.

However, for a long time the microscope remained more of an expensive toy than a scientific instrument. Only in the 30s.XIXin. lenses have improved so much that they can provide a strong increase and clarity of the image. Biologists managed to consider that each cell is covered with a membrane, and under it there is a liquid with a nucleus. The nucleus in plant cells was first described in 1831 by the Scottish botanist Robert Brown.

The famous German biologist Theodor Schwann (1810-1882) was the first scientist to understand that the cell is the smallest element that makes up all the tissues and organs of animals. Later, based on his own research and the work of the German botanist Matthias Jacob Schleiden (1804-1881), Schwann came to the conclusion that the law of cellular structure is also valid for plants. In 1839, he published his later famous essay "Microscopic studies on the correspondence in the structure and growth of animals and plants."

(Encyclopedia for children. V.2. Biology. - 5th ed. / Chief editor M.D. Aksenova. - M .: Avanta +, 2001)

Fig.7 Theodor Schwann Fig.8 Matthias Jakob Schleiden

T. Schwann and M. Schleiden made a number of generalizations, which they later calledcell theory :

All living beings are made up of cells;

Plant and animal cells have a similar structure;

Each cell is capable of independent existence;

The activity of an organism is the sum of the vital processes of its constituent cells.

They mistakenly believed that the cells in the body arise from non-cellular matter. An important addition to the cell theory was the principle of Rudolf Virchow: "Each cell is from a cell" (1859). ( )

PRACTICAL PART

The first part of my research was a survey. I interviewed 60 people, these are students of our school and residents of the village of Podbelevets. The first question on my questionnaire was: Did you know that all organisms are made up of cells? 59 people (98.3%) know the answer to this question. Almost all survey participants (58 people - 96.6%) know that a cell can be seen under a microscope. The main part of the cell, the majority (53 people - 88.3%) called the nucleus and answered correctly, 2 people (3.3%) - the cytoplasm, 2 people (3.3%) - the membrane, and 3 people (5%) do not know answer to this question. 23 people (38.3%) named Robert Hooke as the discoverer of the cell, and this is the correct answer. 19 people (31.6%) named Leeuwenhoek, 3 people (5%) - Schwann and Schleiden, and 15 people (25%) found it difficult to answer.

Based on the results of the survey, we can say that the majority of respondents have an idea about the cell and methods for studying it. Not everyone knows the history of the discovery of the cell. Primary school students do not know the answers to many questions, but they still have a long way to go.

The second stage of my work was an experiment. I prepared a micropreparation of an onion skin plant cell and examined it under a microscope. I saw many cells in which I identified three main parts of the cell: the nucleus, cytoplasm and membrane.

Technique p preparation of a micropreparation of onion skin.

I separated a fleshy scale from a piece of onion. On the inside of it is a thin film. She took it off with tweezers.

She put it on a glass slide, dropped a drop of iodine solution and covered it with a coverslip.

Examined a micropreparation under a microscope at low and high magnification.

The modern school microscope is simple, and allows students to work with it independently, to conduct small studies. It is not difficult for me to prepare micropreparations of plant and animal cells myself and examine them under a microscope.

CONCLUSION

Having studied the literature on this issue, I found out that the microscope was invented at the end of the 16th century (1595) by a Dutch spectacle makerZacharius Jansen(Jansen). Using a microscope, the English scientist Robert Hooke (1665) discovered cells while examining lime cork and called them cells. The Dutchman Anthony Van Leeuwenhoek improved the microscope and described blood cells, spermatozoa, some unicellular animals, etc. Scottish botanist Robert Brown (1831) discovered a dense formation inside the cell, which he called the nucleus. In 1838, the German scientists Theodor Schwann and Matthias Schleiden created the cell theory. They noted that all plant and animal organisms consist of cells similar in structure. In 1858, the German scientist Rudolf Virchow made an addition to the cell theory, indicating that the cell comes from the cell.

Thus, based on my research, the following conclusions can be drawn.

The invention and improvement of the microscope allowed mankind to look into the microscopic world of the living.

With the help of a microscope, it became possible not only to see the cell and its main parts, but also to study its vital activity.

According to the results of the survey, I found out that the majority of the surveyed population, regardless of age, are interested in biology, they know its basics.

USED ​​BOOKS

Belyaev D.K., Borodin P.M., Vorontsov N.N. et al. General biology: textbook. for grades 10-11 of general educational institutions / - M .: Education 2005.

Kamensky A.A. General biology. Grade 10-11: textbook for general educational institutions / - M .: Bustard 2012

Pleshakov A.A., Vvedensky E.L. Biology. Introduction to biology: textbook for grade 5 general education. institutions: line "Rakurs" / A.A. Pleshakov, E.L. Vvedensky, - M .: OOO "Russian Word - Textbook", 2013.

Teremov A.V. Biology. General patterns of life: 9th grade: textbook for students of general educational institutions / A.V. Teremov, R.A. Petrosova, A.I. Nikishov. - M .: Gumanitar. publishing center VLADOS, 2015.

Encyclopedia for children. T.2. Biology.-5th ed./Chief ed. M.D. Aksenova. - M .: Avanta +, 2001.

Internet sites

The vast majority of cells are microscopically small and cannot be seen with the naked eye. It was possible to see the cell and start studying it only when the microscope was invented. The first microscopes appeared at the beginning of the 17th century. For scientific research, the microscope was first used by the English scientist Robert Hooke (1665). Examining thin sections of cork under a microscope, he saw numerous small cells on them. These cells, separated from each other by dense walls, Hooke called cells, using the term "cell" for the first time.

In the subsequent period, which covered the second half of the 17th century, the entire 18th century. and the beginning of the 19th century. The microscope was being improved and data on animal and plant cells were accumulating. By the middle of the 19th century, the microscope had been significantly improved and much had become known about the cellular structure of plants and animals. The main materials on the cellular structure of plants at that time were collected and summarized by the German botanist M. Schleiden.

All the data obtained about the cell served as the basis for the creation of the cellular theory of the structure of organisms, which was formulated in 1838 by the German zoologist T. Schwann. Studying the cells of animals and plants, Schwann found that they are similar in structure, and found that the cell is a common elementary unit of the structure of animal and plant organisms. Schwann outlined the theory of the cellular structure of organisms in the classic work "Microscopic studies on the correspondence in the structure and growth of animals and plants."

At the beginning of the last century, the famous scientist, Academician of the Russian Academy of Sciences Karl Baer discovered the egg cell of mammals and showed that all organisms begin their development from one cell. This cell is a fertilized egg, which is crushed, forms new cells, and tissues and organs of the future organism are formed from them.

Baer's discovery supplemented the cellular theory and showed that the cell is not only a unit of structure, but also a unit of development of all living organisms.

An extremely significant addition to the cellular theory was the discovery of cell division. After the discovery of the process of cell division, it became quite obvious that new cells are formed by dividing existing ones, and do not arise anew from non-cellular matter.

The theory of the cellular structure of organisms also includes the most important materials for proving the unity of the origin, structure and development of the entire organic world. F. Engels highly appreciated the creation of the cellular theory, putting it in importance next to the law of conservation of energy and the theory of natural selection by Charles Darwin.

By the end of the XIX century. The microscope was improved so much that it became possible to study the details of the structure of the cell and its main structural components were discovered. At the same time, knowledge about their functions in the vital activity of the cell began to accumulate. By this time, the emergence of cytology, which is currently one of the most intensively developing biological disciplines, dates back.

The most important events associated with the early development of cell biology include:

• 1665 - Robert Hooke first saw dead cells while examining the structure of cork under a microscope. Hooke believed that cells are empty, and cell walls are living matter.
• 1650-1700 - Anthony van Leeuwenhoek first observed living cells under a microscope, in particular protozoa, as well as red blood cells.
• 1831-1839 - Robert Brown described the nucleus as a spherical body found in plant cells.
• 1838-1839 - botanist Matthias Schleiden and zoologist Theodor Schwann, combining the ideas of different scientists, created a cellular theory, according to which the cell is the basic structural and functional unit of living organisms.
• 1840 - Purkinje proposed the name protoplasm to refer to the cellular content, making sure that it is the content, and not the cell walls, that is the living substance.
• 1855 - Virchow proved that all cells are formed from other cells by division.
• 1866 - Haeckel established that the nucleus carries out the preservation and transmission of hereditary traits.
• 1866-1898 - describes the main components of the cell, which can be seen under an optical microscope. Cytology acquires the character of an experimental science.
• 1900 - after the advent of genetics, cytogenetics begins to develop, studying the behavior of chromosomes during division and fertilization, its influence on the hereditary characteristics of organisms.
• 1946 - The use of the electron microscope began in biology, which made it possible to study the ultrastructures of cells.