Two forms of cellular organization of living matter. The cell is a universal form of organization of living matter. The main structural components of a eukaryotic cell and their characteristics. Review questions and assignments
Matter is a conventional designation adopted to classify all living organisms on our planet. Live nature The earth is truly diverse. Organisms can take on different sizes: from the simplest and single-celled microbes, moving on to multicellular creatures, and ending with the largest animals on earth - whales.
Evolution on Earth occurred in such a way that organisms developed from the simplest (in the literal sense) to more complex ones. Thus, appearing and disappearing, new species improved in the course of evolution, taking on an increasingly bizarre appearance.
To systematize this incredible number of living organisms, levels of organization of living matter were introduced. The point is that, despite the differences in appearance and in structure, all organisms of living nature have common features: they one way or another consist of molecules, have repeating elements in their composition, in one sense or another - common functions of organs; they feed, reproduce, grow old and die. In other words, the properties of a living organism, despite external differences, are similar. Actually, based on these data, we can trace how evolution took place on our planet.
2. Supramolecular or subcellular. The level at which the structuring of molecules into cell organelles occurs: chromosomes, vacuoles, nucleus, etc.
3. Cellular. At this level, matter is presented in the form of an elementary functional unit - a cell.
4. Organ-tissue level. It is at this level that all organs and tissues of a living organism are formed, regardless of their complexity: the brain, tongue, kidney, etc. It should be borne in mind that tissue is a collection of cells united by a common structure and function. An organ is a part of the body whose “responsibilities” include performing a clearly defined function.
5. Ontogenetic or organismal level. At this level, organs of different functionality are combined into a whole organism. In other words, this level is represented by a complete individual of any kind.
6. Population-species. Organisms or individuals that have similar structure, function and appearance, and thus belong to the same species, are included in the same population. In biology, a population is understood as the totality of all individuals of a given species. In turn, they all form a genetically unified and separate system. A population lives in a specific place - an area and, as a rule, does not intersect with representatives of other species. A species, in turn, is the totality of all populations. Living organisms can interbreed and produce offspring only within their own species.
7. Biocenotic. The level at which living organisms are united into biocenoses - the totality of all populations living in a specific territory. Belonging to one species or another does not matter in this case.
8. Biogeocenotic. This level is due to the formation of biogeocenoses, that is, a combination of biocenosis and inanimate factors (soil, climatic conditions) in the area where the biocenosis lives.
9. Biosphere. A level that unites all living organisms on the planet.
Thus, the levels of organization of living matter include nine points. This classification defines the existing modern science systematization of living organisms.
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1. Introduction
3. Cell as a morphofunctional unit of living matter
4. The organism as the basis for the integrity of a living system
5. Conclusion
6. References
1. Introduction
The modern biological picture of the world is based on the fact that the living world is a colossal system of highly organized systems. In modern biology, the classical levels of this system, which is defined as living matter, are the following:
1. The molecular genetic level is the level of organization of living matter at which the transition from the atomic-molecular level of inanimate matter to macromolecules of living matter took place. This is the level of functioning of biopolymers, such as proteins, nucleic acids, polysaccharides. At this level, the elementary structural units are genes. All hereditary information in living organisms is contained in DNA molecules. The implementation of this information is associated with the participation of RNA molecules.
2. Cellular and subcellular levels reflect the processes of cell specialization, as well as various intracellular inclusions.
3. Organismal and organ-tissue levels reflect the characteristics of individual individuals, their structure, physiology, behavior, as well as the structure and functions of organs and tissues of living beings.
4. The population-species level is formed by freely interbreeding individuals of the same species. Its study is important for identifying factors influencing population sizes. This level is also important from the point of view of studying the paths of historical development of living things, their evolution.
5. The level of biogeocenoses expresses the next stage in the structure of living things. Biogeocenoses are understood as areas of the Earth with a certain composition of closely interconnected living and nonliving components, representing a single natural complex, an ecosystem. Rational use of nature is impossible without knowledge of the structure and functioning of biogeocenoses, or ecosystems.
6. The biosphere level includes the entire set of living organisms of the Earth that exist in close connection with the natural environment. At this level, biological science solves such a pressing problem as regulating the concentration process carbon dioxide in the atmosphere. Investigating the biosphere level of organization of living things, scientists found that in Lately As a result of a significant increase in economic activity and weak environmental protection, the concentration of carbon dioxide in the planet's atmosphere began to increase. As a result, there was a danger of a global increase in temperature, the emergence of the so-called “greenhouse effect,” and an increase in precipitation in some areas to the scale of the Great Flood.
The idea of the structural levels of organization of living systems was formed under the influence of the discovery of the cellular theory of the structure of bodies. In the mid-19th century, the cell was considered as the last unit of living matter, like the atom of inorganic bodies (M. Schleiden and E. Haeckel). But there remained a question that the cellular theory could not answer: on which structures the properties of living organisms depend. Therefore, experimental scientists continued their work in the field of studying cellular structures. In the course of this work it was obtained next result: Proteins are built from 20 amino acids, which are connected by long polypeptide bonds. 9 of these amino acids are essential, the rest are synthesized by the body itself. Feature amino acids is that they are all left-handed isomers, although there are also right-handed amino acids. Both forms of such isomers are almost identical to each other and differ only in spatial configuration, and therefore each of the amino acid molecules is a mirror image of the other. This phenomenon was first discovered by L. Pasteur. He discovered that substances of biological origin are capable of deflecting a polarized beam. These substances were subsequently called optical isomers. In contrast, molecules of inorganic substances do not have this ability and are built symmetrically. Based on his experiments, L. Pasteur expressed the idea that the most important property of all living matter is their molecular asymmetry, similar to the asymmetry of the left and right hand. This property was called molecular chirality. For a long time, in connection with the study of protein structure, opinions arose that proteins constitute the fundamental basis of life (F. Engels). Along with the study of protein structure, the mechanisms of heredity and reproduction of living systems were intensively studied. The most important discovery along this path was the isolation of a phosphorus-rich substance from the cell nucleus, which was later called nucleic acid. There are two types of nucleic acids: deoxyribonucleic acids and ribonucleic acids. In 1944, D. Watson and F. Crick proposed and experimentally confirmed the hypothesis about the structure of the DNA molecule as a material carrier of information. According to the theory of Watson and Crick, the hereditary information in a DNA molecule is carried by a sequence of four bases: two purines and two pyrimidines (1953). A hypothetical explanation of the mechanism for converting a four-letter DNA structure record into a 20-letter one was given by G. Gamov, who assumed that encoding one amino acid requires a combination of three DNA nucleotides. Seven years later, this hypothesis was confirmed experimentally. In the 60s, F. Jacob and J. Monod proved that, according to their functional activity, all genes are divided into “regulatory”, encoding protein structure, and “structural”, encoding the synthesis of metabolites. The transition to the molecular level of research has changed the understanding of the mechanism of variability. In addition to mutations, mechanisms of gene recombination were named.
2. Precellular forms of organization of living matter
matter cell morphofunctional system
The only representatives of the precellular organization of living matter are viruses.
A virus is a noncellular infectious agent that can only reproduce inside living cells.
To date, over five thousand types of viruses have been described in detail. Scientists believe there are millions of species. Virology is the study of viruses. Virology is a branch of microbiology.
Viruses can infect all types of organisms: from bacteria and archaea to plants and animals. Viruses that infect bacteria are called bacteriophages. Viruses that infect other viruses are called satellites.
The history of the study of viruses began with an article by Dmitry Iosifovich Ivanovsky, describing a non-bacterial pathogen of tobacco plants. And the first discovered and officially described virus was the tobacco mosaic virus, discovered by the Dutchman Martin Beijerinck in 1898.
Origin
The origin of viruses is unclear since they do not leave any fossil remains, but there are three main theories about their origin:
2. Cellular origin hypothesis (nomadic/escape hypothesis). Some viruses may have emerged from fragments of DNA or RNA released from the genome of a larger organism. Such fragments can come from plasmids - DNA molecules that can be transmitted from cell to cell) or from transposons (DNA molecules that replicate and move from place to place within the genome.
3. Coevolution hypothesis. This hypothesis suggests that viruses arose from complex complexes of proteins and nucleic acids at the same time as the first living cells on Earth, and have been dependent on cellular life for billions of years.
Structureviruses
Viral particles called varions consist of three components:
1. Genetic material. DNA or RNA. Some species have both types of molecules.
2. Capsid - protein shell. Serves to protect DNA/RNA.
3. Additional lipid membranes.
Based on the first criterion, viruses are divided into DNA-containing and RNA-containing. The Baltimore classification of viruses is based on this principle. The ICTV classification divides viruses into orders, families, subfamilies, genera and species.
Viral capsids are divided into four classes:
1. Spiral
2. Icosahedral
3. Oblong
4. Comprehensive
The average virus is about a hundred times smaller than the average bacterium. Therefore, most of them are indistinguishable under a light microscope.
Vitalcycle
There are usually six stages in the life cycle of a virus:
1. Attachment is the formation of a specific connection between viral capsid proteins and receptors on the surface of the host cell. The specificity of binding determines the host range of the virus.
2. Penetration into the cell.
3. Envelopment is the process of loss of the capsid.
4. Replication of viruses.
5. Assembly of viral particles.
6. Exit from the cell.
4. Cell as a morphofunctional unit of living things
A cell is the elementary unit of a living organism.
All living things are made up of cells as individual units and reproduce from cells, so a cell is considered the smallest unit of all living things. The cell has all the signs of a living thing; it is characterized by irritability, metabolism, self-organization and self-regulation, and the transmission of hereditary characteristics. A cell is a complex, self-organizing formation of organelles, which is a microcarrier of life, since each cell contains genetic information sufficient to reproduce the entire organism. All organisms are made up of one or many cells. Cell sizes vary from 0.1 microns to 155 mm (ostrich egg in shell).
The life of each cell is subordinated to the activities of the entire organism as a whole. Cells of multicellular organisms are incapable of existing in an open environment, with the exception of unicellular organisms - bacteria, protozoa, algae, and fungi. The parts that make up the cell are devoid of vital abilities. Cells isolated from various tissues of living organisms and placed in a special nutrient medium can grow and multiply. This ability of cells is widely used for research and applied purposes.
Despite the great variety and significant differences in appearance and function, all cells are composed of three main parts - plasmatic membranes, controlling the transition of substances from environment to the cage and back, cytoplasm with varied structure and cellular kernels, containing the carrier of genetic information - DNA. All animal and some plant cells contain centrioles- cylindrical structures with a diameter of about 0.15 microns, forming cell centers. Typically, plant cells are surrounded by a membrane - cellular wall. In addition, they contain plastids- cytoplasmic organelles (specialized cell structures), often containing pigments that determine their color.
Rice. 1 The structure of animal (A) and plant (B) cells
Surrounding the cell membrane consists of two layers of molecules of fat-like substances, between which there are protein molecules. The main function of the cell is to ensure the movement of certain substances in forward and reverse directions to it. In particular, the membrane maintains the normal concentration of certain salts inside the cell and plays an important role in its life: if the membrane is damaged, the cell dies immediately, while at the same time, without some other structural components, the life of the cell can continue for some time. The first sign of cell death is the beginning of changes in the permeability of its outer membrane.
Inside the cell plasma membrane is cytoplasm, containing an aqueous saline solution with soluble and suspended enzymes (as in muscle tissue) and other substances. The cytoplasm contains a variety of organelles - small organs surrounded by their own membranes. Organelles, in particular, include mitochondria - sac-like formations with respiratory enzymes. Sugar is converted into them and energy is released. There are also small bodies in the cytoplasm - ribosomes, consisting of protein and nucleic acid (RNA), with the help of which protein synthesis is carried out. The intracellular environment is quite viscous, although 65-85% of the cell mass is water.
All viable cells, with the exception of bacteria, contain core, and in it - chromosomes- long thread-like bodies consisting of deoxyribonucleic acid and protein attached to it. In a multicellular organism, all the complex manifestations of life arise as a result of the coordinated activity of its constituent cells.
The vital functions of the cell are motility, irritability, metabolism and reproduction. Cell motility is expressed in the intracellular circulation of cell contents, flow, beating of tiny protoplasmic processes, and contractility. Irritability is determined by the cell’s ability to perceive a stimulus and respond to it with an impulse or wave of excitation. This is most characteristic of the nerve cells of organisms. Metabolism includes all the transformations of matter and energy that occur in cells.
The most important function of a cell is its reproduction by division and formation of daughter cells. As the cell grows, the nutrition of its individual elements deteriorates, the ability to control the internal processes of the cell decreases, and the cell becomes unstable. Next, the cell divides into two daughter cells, as a way out of the unstable state; the newly formed cells acquire stability until the next division. When a daughter cell divides, a complete set of chromosomes carrying genetic information is transferred. Therefore, before division, the number of chromosomes in a cell doubles and during division, each daughter cell receives one set of them. In any organism, throughout its life, there is a process of replacing old cells with new ones that are formed. The average lifespan of human cells is one to two days, and the total number of cells is approximately 10 15 . It is the ability to reproduce themselves, and not just the ability to grow and eat, that allows cells to be considered the smallest units of life.
The major structural differences between animal and plant cells are few. Firstly, animal cells, unlike plant cells (excluding lower plants), contain small bodies - centrioles located in the cytoplasm. Secondly, as already mentioned, plant cells have protein formations in their cytoplasm - plastids, which animals do not have. And thirdly, plant cells have the previously mentioned cell wall, thanks to which they retain their shape. Animal cells have only a thin plasma membrane and therefore are able to move and change shape.
Depending on the type of cells, all organisms are divided into two groups - prokaryote And eukaryotes. Prokaryotes include bacteria, and eukaryotes include all other organisms: protozoa, fungi, plants and animals. Eukaryotes can be unicellular or multicellular. It is assumed that the first organisms that appeared about 4-3.5 billion years ago were prokaryotes.
RolecellsVevolutionalive
The appearance of the first primitive cell marked the beginning of the biological evolution of life on the planet. What caused the emergence of a living cell from a non-living one is still unknown; there are several hypotheses, but most of them indicate that there was some kind of pre-cellular ancestor - protobiont, from which the oldest cell was subsequently formed. The mechanism of transition from complex organic substances to simple living organisms has not yet been established by science. The theory of biochemical evolution proposed by scientist A.I. Oparin in the 20s, offers only a general scheme. In accordance with it, molecules of complex hydrocarbons could line up between primary clots of organic substances (coacervates), which led to the formation of a primitive cell membrane that provided stability to these clots. It is with the appearance of the membrane that we can talk about the birth of a cell - the basic structural unit of life, capable of growth and reproduction. Obviously, the archecell was delimited from external environment a two-layer shell (membrane), had the ability to absorb protons, ions and small molecules through it, and its metabolism was based on low molecular weight carbon compounds. The structure of the archecell is characterized by the presence of a cellular skeleton, which is responsible for the integrity of the cell and also provides the possibility of its division.
The first single-celled organisms to appear on Earth were primitive bacteria that did not have a nucleus - prokaryotes. They lived in an oxygen-free environment and ate ready-made organic compounds - substances synthesized during the process of chemical evolution. However, as the earth's atmosphere filled with oxygen, many bacteria had to adapt to oxygen respiration - photosynthesis, which was a turning point in the evolution of living things. Photosynthesis accelerated the biological cycle of substances and the evolution of living things in general. The long process of transition to photosynthesis led approximately 2.6 billion years ago to the emergence of the first organisms with a nucleus - eukaryotes. These were more advanced organisms, in the nucleus of which chromosomes with DNA were concentrated, the cell itself reproduced without major changes.
The subsequent evolution of eukaryotes is associated with the division of these organisms into animals and plants (approximately 2.6 billion - 570 million years ago). Plant cells have evolved towards the development of a hard cellulose cell wall and the active use of photosynthesis, while animal cells have “chosen” to increase the ability to move, and also have improved ways to absorb and excrete food products.
The next important stages in the evolution of the living world were sexual reproduction (about 900 million years ago) and the emergence of multicellular organisms with bodies, tissues and organs that perform certain functions (700-800 million years ago). These were sponges, worms, arthropods, etc. By that time, the world's oceans were already populated by algae.
To summarize, we can say that it was the isolation of a living independent cell from the environment that became the impetus for the beginning of the evolution of life on earth and the role of the cell in the development of all living things is dominant.
3. The organism as the basis for the integrity of a living system
An organism is any living thing. It differs from inanimate nature by a certain set of properties inherent only to living matter: cellular organization; metabolism with the leading role of proteins and nucleic acids, ensuring homeostasis of the body - self-renewal and maintaining the constancy of its internal environment. Living organisms are characterized by movement, irritability, growth, development and heredity, as well as adaptability to the conditions of existence - adaptation.
Interacting with the abiotic environment, the organism acts as an integral system, including lower and lower levels of biological organization. All these parts of the body (genes, cells, cellular tissues, entire organs and their systems) are components and systems of the preorganism level. Changes in some parts and functions of the body inevitably entail changes in others. Thus, in changing conditions of existence, as a result of natural selection, certain organs receive priority development. For example, a powerful root system in plants of an arid zone (feather grass) or “blindness” as a result of reduced eyes in nocturnal animals that exist in the dark (mole).
Living organisms have metabolism, or metabolism, with many chemical reactions occurring. An example of such reactions is respiration, which Lavoisier and Laplace considered a type of combustion, or photosynthesis, through which green plants bind solar energy, and the results of further metabolic processes are used by the entire plant.
As you know, in the process of photosynthesis, in addition to solar energy, carbon dioxide and water are used. The overall chemical equation for photosynthesis looks like this:
Solar energy + 6СО 2 +12Н 2 О >С 6 Н 12 О 6 + 6О 2,
where C 6 H 12 O 6 is an energy-rich glucose molecule.
Almost all carbon dioxide (CO2) comes from the atmosphere, and during the day its movement is directed downward to plants, where photosynthesis occurs and oxygen is released. Respiration is the reverse process, and the movement of CO 2 at night is directed upward, and oxygen is absorbed.
Some microorganisms and bacteria are capable of creating organic compounds due to other components, for example, due to sulfur compounds. Such processes are called chemosynthesis.
Metabolism in the body occurs only with the participation of special macromolecular protein substances - enzymes that act as catalysts. Each biochemical reaction during the life of an organism is controlled by a special enzyme, which in turn is controlled by a single gene. A change in a gene, called a mutation, leads to a change in the biochemical reaction due to a change in the enzyme, and in the case of a deficiency of the latter, to the loss of the corresponding stage of the metabolic reaction.
However, not only enzymes regulate metabolic processes. They are helped by coenzymes - these are large molecules, part of which are vitamins - substances necessary for the metabolism of all organisms - bacteria, green plants, animals and humans. The lack of vitamins leads to diseases - metabolism is disrupted.
Finally, a number of metabolic processes require special chemical substances, called hormones, which are produced in various places (organs) of the body and are delivered to other places by blood or through diffusion. Hormones carry out the general chemical coordination of metabolism in any organism and help, for example, the nervous system of animals and humans.
At the molecular genetic level, the effects of pollutants, ionizing and ultraviolet radiation are especially sensitive. It causes disruption of genetic systems, cell structure and inhibits the action of enzyme systems. All this leads to diseases of humans, animals and plants, oppression and even destruction of species and living organisms.
Metabolic processes occur with varying intensity throughout the life of the organism, throughout the entire path of its individual development. This path from birth to the end of life is called ontogenesis. It is a set of successive morphological, physiological and biochemical transformations undergone by the body over the entire period of life.
Ontogenesis includes the growth of the organism, i.e. increase in body mass and size, and differentiation, i.e. the emergence of differences between homogeneous cells and tissues, leading them to specialization in performing various functions in organism. In organisms with sexual reproduction, ontogenesis begins with a fertilized cell (zygote), with asexual reproduction - with the formation of a new organism by dividing the maternal body or a specialized cell, by budding, as well as from a rhizome, tuber, bulb, etc.
Each organism goes through a number of development stages in ontogenesis. For organisms that reproduce sexually, a distinction is made between the embryonic (embryonic), post-embryonic (postembryonic) and the period of development of the adult organism. The embryonic period ends with the release of the embryo from the egg membranes, and in viviparous animals - with birth. The initial stage of post-embryonic development, which occurs according to the type of direct development or the type of metamorphosis, is of important ecological significance for animals. In the first case, there is gradual development into an adult form (chick - hen, etc.), in the second, development occurs in the form of a larva, which exists and feeds independently before turning into an adult (tadpole - frog). In a number of insects, the larval stage allows them to survive unfavorable seasons (low temperatures, drought, etc.).
In plant ontogenesis, a distinction is made between growth, development (an adult organism is formed) and aging (weakening of the biosynthesis of all physiological functions and death). The main feature of ontogenesis higher plants and most algae there is an alternation of asexual (sporophyte) and sexual (hematophyte) generations. Processes and phenomena taking place at the ontogenetic level, i.e. at the level of the individual (individual), it is a necessary and very essential link in the functioning of all living things. Ontogenesis processes can be disrupted at any stage by the action of chemical, light and thermal pollution of the environment and lead to the appearance of deformities or even the death of individuals at the postnatal stage of ontogenesis.
The modern ontogeny of organisms has developed over a long period of evolution, as a result of their historical development - phylogenesis. It is no coincidence that this term was introduced by E. Haeckel in 1866, since for environmental purposes it is necessary to reconstruct the evolutionary transformations of animals, plants and microorganisms. This is the work of science - phylogenetics, based on data from three sciences - morphology, embryology and paleontology.
The relationship between the development of living things in historical and evolutionary terms and the individual development of an organism was formulated by E. Haeckel in the form of a biogenetic law: the ontogeny of any organism is a brief and condensed repetition of the phylogeny of a given species. In other words, first in the womb (in mammals, etc.), and then, upon being born, the individual in its development repeats in an abbreviated form the historical development of its species.
5. Conclusion
In modern science, the method of structural analysis is widely used, which takes into account the systematic nature of the objects under study. After all, structure is the internal dismemberment of material existence, the way of existence of matter.
The structural levels of the organization of matter are built according to the principle of a pyramid: the highest levels consist of a large number of lower levels. The lower levels are the basis of the existence of matter. Without these levels, further construction of the “pyramid of matter” is impossible. Higher levels are formed through evolution - gradually moving from simple to complex. Structural levels of matter are formed from a certain set of objects of any kind and are characterized by a special way of interaction between their constituent elements.
All objects of living and inanimate nature can be represented in the form of certain systems that have specific features and properties that characterize their level of organization. Taking into account the level of organization, one can consider the hierarchy of structures of organization of material objects of animate and inanimate nature. Such a hierarchy of structures begins with elementary particles, which represent the initial level of organization of matter, and ends with living organizations and communities - the highest levels of organization.
The concept of structural levels of living matter includes ideas of systematicity and the associated organic integrity of living organisms. However, the history of systems theory began with a mechanistic understanding of the organization of living matter, according to which everything higher was reduced to the lower: life processes - to a set of physical and chemical reactions, and the organization of the body - to the interaction of molecules, cells, tissues, organs, etc. P.
Bibliography
1. Biological encyclopedic Dictionary. M.: Great Russian Encyclopedia, 1989.
2. Danilova V.S. Basic Concepts modern natural science: Textbook. manual for universities. M., 2000.
3. Medawar P., Medawar J. Science of living things. Modern concepts in biology. M.: Mir, 1983.
4. Reimers N.F. Popular biological dictionary. M.: Nauka, 1994.
5. Ruzavin G.I. Concepts of modern natural science: Textbook for universities. M., 2003.
6. Slyusarev A.A., Zhukova S.V. Biology. Kyiv: Vishcha school, 1987.
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A cell is the basic unit of life (biological activity), bounded by a semi-permeable membrane and capable of self-reproduction in an environment that does not contain living systems. Life begins with a cell. There is no life outside cells.
The first studies of cells date back to the 17th century, and are probably due to the Englishman Robert Hooke (1635-1703). Examining sections of cork under a primitive microscope (1665), he discovered that they consisted of cells, which he called cells (from the Latin cellula - cell, cell). Subsequently, the cellular structure of many plants was observed microscopically by the Italian M. Malpigi (1628-1694) and the Englishman N. Grew (1641-1712), but what they saw we now call the cell wall of plant cells. In 1675, the Dutchman A. Leeuwenhoek (1632-1723) was the first to see single-celled organisms (bacteria) using a simple microscope.
In 1825, the Czech Jan Purkinje (1787-1869) saw and described the internal contents of the cell, calling it protoplasm (from the Greek protos first, plasma - formation), and in 1831 the Englishman R. Brown (G773-1858) discovered the nucleus cells (from Latin nucleus, Greek saguon).
The most important stage in the study of cells was the work that provided the factual basis for the creation of cell theory. In 1838, the German botanist M. Schleiden (1804-1881) came to the conclusion that plant tissues consist of cells, while the German zoologist T. Schwann (1810-1882) in 1839 came to a similar conclusion by studying the structure of animal cells . Based on the data that animal and plant cells have nuclei, M. Schleiden and T. Schwann in 1838-1839. formulated a cell theory that contained a number of important provisions, namely:
a) Organisms consist of cells and their metabolic products, and cells are the main structural unit of plants and animals;
b) Cell reproduction underlies the growth of animals and plants.
An outstanding contribution to the subsequent development of cell theory belongs to R. Virchow (1821-1902), who formulated in 1855 the very important position “cellula e cellula” (“each cell from a cell”), meaning that a cell can arise only from a pre-substance. existing cell and that there are no other ways for cells to appear. This position was not only of fundamental importance, but also of practical importance, since it meant the beginning of the development of the foundations of cellular pathology.
Subsequently, the most important contribution to the development of cell theory was provided by the discovery of chromosomes and observations in 1879-1883. cell division by mitosis (W. Fleming, 1844-1905; W. Ruth 1850-1924 and others). Already by end of the 19th century V. Chromosomes were described, their haploid and diploid numbers were determined in a number of organisms, and the phases of mitosis were determined and named. At the same time, a synthesis of cytology and genetics took place, as well as the identification of an independent problem called “Cell Biology”.
At the beginning of the 20th century. (1903) R. Hertwig (1850-1937) formulated the law of constancy of the nuclear-plasma ratio, and in 1905 J. Farmer and J. Moore introduced the term “meiosis” into the scientific literature, which contributed to a better understanding of cell division and development. But especially the progress of the study of the cell was ensured by the introduction into practice of research of phase-contrast and electron microscopy, and then the method of labeled atoms. Already in the 50s. In our century, electron microscopic images of almost all cell structures were obtained.
Modern stage in the development of cell theory is characterized by further substantiation of its provisions based on the results obtained in the study thin structure cells, synthesis of nucleic acids and proteins, as well as regulation of gene activity. The most important position of the cellular theory that the cell is an elementary structural and functional unit of living things, outside of which there is no life, i.e., has received final confirmation. The cell is the elementary unit of structure and function of a multicellular organism. Cells are highly organized differentiated formations, and cell reproduction ensures physical basis genetic continuity between parent cells and daughter cells. It has been established that the activity of an organism depends on the activity of its cells and that the growth, development and differentiation of tissues depend on the formation of new cells. The absorption, transformation, storage and use of substances and energy occurs through cells. Cell structures are the arena in which numerous biological reactions take place, in particular fermentation, respiration, photosynthesis, and chromosome duplication, and these processes take place both in unicellular organisms and in the cells of multicellular organisms. We can say that the life of multicellular organisms is based on the life of their cells.
Biology - the science of life (from the Greek bios - life, logos - science) - studies the laws of life and development of living beings. The term “biology” was proposed by the German botanist G. Treviranus in 1802 and the French naturalist J. Lamarck in 1809. Biology refers to the natural sciences, just like chemistry, physics, astronomy, and geology. Modern biology represents a set of sciences about living nature. Each of the biological sciences has its own objects of study, problems and uses various methods research. Biology studies all forms of living organisms, from viruses to humans, their structure, functions, development, origin, connection with each other and the environment. The system of biological sciences is complex due to the diversity of life forms on Earth. 2
In biology, one can distinguish disciplines that study morphology, that is, the structure of organisms, and physiology, that is, the processes occurring in living organisms, and the metabolism between the organism and the environment. Morphological sciences include, for example, cytology, which studies the structure of the cell; histology - the science of tissues; anatomy - about the shape and structure of individual organs, systems and the body as a whole. Distinguish between the anatomy of humans, animals, and plants. Comparative anatomy studies the similarities and differences in the structure of animals. 4
Physiological sciences consider the life processes (functions) of animal and plant organisms, their individual systems, organs, tissues and cells. Physiology of humans and animals is divided into several disciplines that are closely related to each other. There is general physiology, which studies the general patterns of the reaction of the body and its structures to the influence of environmental factors, and special special physiology, which studies the mechanisms of response of certain classes of animals (for example, birds or mammals) or individual organs (for example, the liver or lungs) to external influences . Plant physiology studies the general patterns of physiological and biochemical processes, their essence and the relationship between plant life and environmental conditions. 5
The science of heredity and variability of living organisms is called genetics. Depending on the object of study, the genetics of plants, animals, microorganisms and humans are distinguished. Embryology studies the patterns of individual development. The main task of ecology is the study of the interaction between organisms and the environment that allows them to survive, develop and reproduce. Anthropology is the science of the origins of man and his races. This science is not only biological, but also social, since understanding the biological evolution of man is impossible without studying the patterns of development of human society. 6
Modern biology is characterized by high specialization of the disciplines included in it, complex interaction with other sciences, such as chemistry, physics, mathematics, and the emergence of new complex disciplines. The emergence of new chemical and physical research methods in biology led to the emergence of such sciences as biochemistry, biophysics, and molecular biology. Biochemistry studies the chemical composition of living organisms, the transformation of substances in the process of their life; biophysics - physical properties and processes in individual organs, tissues, cells and the body as a whole. Molecular biology explores the basic properties and manifestations of life at the molecular level. Molecular biology emerged in the early 1950s. XX century as a result of the accumulation of knowledge about the structure and functions of proteins and nucleic acids. The use of complex research methods made it possible to study the structures and functions of the genetic apparatus of cells, the mechanism for implementing genetic information, etc. New disciplines have emerged, such as molecular genetics, molecular virology, etc. 7
Both theoretical and practical areas of research occupy an important place in biology. The former allow one to make discoveries that ensure the successful development of applied disciplines and can be used by humans in practical activities. Taking into account scientific achievements and the high pace of development of biological sciences, we can assume that since the mid-twentieth century. The age of biology has begun. Molecular genetic analysis of DNA is used for personal identification, determination of kinship and other medical purposes. Genetic engineering methods are used to produce genetically modified food products and treat certain human diseases. Biological Sciences Presents theoretical basis medicine, agronomy, livestock farming and other sectors of the national economy. For example, knowledge of the laws of genetics and selection makes it possible to develop new highly productive breeds of animals and more productive plant varieties. Discoveries made in genetic engineering can be used in biotechnology (to produce biologically active substances, antibiotics, enzymes, hormonal drugs, etc.), during cloning. 8
Basic properties of living things Chemical composition. Living things are made up of the same chemical elements, as nonliving, but in organisms there are molecules of substances characteristic only of living things (nucleic acids, proteins, lipids, carbohydrates). Chemical substances that make up living organisms have a more complex structure than inanimate nature. In living organisms 98% chemical composition accounts for four elements: carbon, oxygen, nitrogen, hydrogen. In inanimate nature, in addition to oxygen, silicon, iron, magnesium, etc. are of primary importance. Chemical organization is closely related to the orderliness of the structure and function of any organism. 9
Basic properties of living things: Discreteness and integrity. Life on earth appears in discrete forms. Any biological system (cell, organism, species, etc.) consists of individual parts, i.e. discrete. The interaction of these parts forms a complete system. For example, the body includes individual organs, connected structures but also functionally into a single whole; any type of organism includes individual individuals. Discreteness of structure is the basis of structural order, creating the possibility of self-renewal and replacement of some parts of the system without disrupting the functions they perform. For example, “worn out” cell organelles (mitochondria, etc.) are destroyed and replaced with new ones; violations of the functions they perform ( cellular respiration, ATP (adenosine triphosphoric acid) synthesis, etc.) does not occur. 10
Basic properties of living things Structural organization. Living systems are capable of bringing order to the chaotic movement of molecules, forming certain structures. Living things are characterized by orderliness in space and time. This is a complex of complex self-regulating metabolic processes occurring in a strictly defined sequence aimed at maintaining a constant internal environment - homeostasis. The complexity of the structural organization of living things can be traced at all levels. Open biological systems are inextricably linked with the external environment, which influences the processes occurring in them. For example, in complex communities of organisms called biocenoses, there are diverse interactions and interdependencies between individuals of the same and different types, as well as with their surrounding environment. eleven
Basic properties of living metabolism and energy. Living organisms are open systems that constantly exchange matter and energy with the environment. The basis of this exchange is the interconnected processes of assimilation and dissimilation that occur at the cellular level. Assimilation (assimilation) is observed when a living organism absorbs necessary substances from the external environment and transforms them into substances specific to it. This process requires energy. During dissimilation (the process of decomposition of complex substances into simple ones), the energy necessary for the biosynthesis reaction and the final decomposition products are released. Metabolism ensures the constancy of the chemical composition of all parts of the body. When environmental conditions change, self-regulation of life processes occurs according to the feedback principle, aimed at restoring the constancy of the internal environment - homeostasis. For example, waste products can have a strong and strictly specific inhibitory effect on enzymes that formed the initial link in a long chain of reactions. 12
Basic properties of living things Self-reproduction. The lifetime of any biological system is limited. To maintain life, a process of self-reproduction is necessary, associated with the formation of new structures that carry genetic information found in DNA molecules. At the molecular level, self-reproduction is carried out on the basis of matrix synthesis, i.e. new molecules are synthesized in accordance with the program embedded in the structure of pre-existing molecules. Living beings, having a limited life span, reproduce and leave behind offspring. The reproduction of organisms of all species living on Earth maintains the existence of the biosphere. 13
Basic properties of living things Heredity. The DNA molecule stores and transmits hereditary information thanks to the matrix principle of replication, ensuring material continuity between generations. Heredity is the ability of organisms to transmit their characteristics, properties and developmental features from generation to generation during reproduction. Variability. This is the acquisition of new characteristics and properties by the body. When transmitting hereditary information, various deviations sometimes arise, which lead to changes in characteristics and properties in descendants. Variability determines the creation of diverse material for the selection of the most adapted organisms to given environmental conditions. If these changes favor life, they are fixed by selection. This is how new species appear. Hereditary variability contributes to the evolution of species. 14
Basic properties of living things Growth and development. The living form of matter is characterized by individual and historical development. Organisms inherit certain genetic information about the possibility of developing certain characteristics. The implementation of information occurs in the process of individual development - ontogenesis. At a certain stage of ontogenesis, the body grows (increase in mass), associated with the reproduction of molecules, cells and other biological structures and their differentiation (the appearance of differences in structure and function). Growth is accompanied by development, as a result of which a new qualitative state of the object arises, new structures are formed that are capable of performing certain functions. For example, plants develop new branches that differ in structure from others. In inanimate nature, for example, crystal growth occurs due to the addition of similar structures. Historical development- phylogeny - accompanied by the formation of new species. Thus, all the diversity of living organisms on Earth arose. 15
Basic properties of living things Irritability and movement. The ability of living organisms to selectively respond to external influences with specific reactions is called irritability. Animals react more actively to the influence of the external environment. Plants react more slowly. The reaction of highly organized animals and humans to irritation occurs through nervous system and is called a reflex. Irritability is a universal property of all living beings. Organisms respond to stimulation with movement. Organisms that do not have a nervous system and lead an attached lifestyle, in response to the influence of a stimulus, make movements called tropisms. For example, phototropism is a response to light in plants. Single-celled animals and some cells of a multicellular organism, such as leukocytes, perform movements called taxis. The response to exposure to chemicals is called chemotaxis. Inanimate objects react passively to their environment. For example, if a stone is pushed, it will passively move from its place. 16
Basic properties of living things Self-regulation. The manifestation of all the basic properties that characterize life is associated with self-regulation, i.e. the ability of living biological systems to automatically maintain physiological and other biological indicators at a certain constant level. With self-regulation, control factors do not influence the regulated system from the outside, but are directly formed in it. The mechanisms of self-regulation are varied and depend on the level of organization of living matter. Self-regulation of all vital processes in organisms is carried out according to the feedback principle. The lack of any substances activates internal resources the body, and their excess is stored in reserve. For example, an increase in the concentration of glucose in the blood leads to increased production of the pancreatic hormone - insulin, which reduces the sugar content in it. In turn, a decrease in blood glucose levels slows down the release of the hormone into the bloodstream. Excess glucose under the influence of insulin is converted into glycogen and stored. 17
Levels of organization of living matter Molecular genetic level. Any living system, no matter how complex it is organized, consists of biological macromolecules: proteins, nucleic acids and other organic substances. At the molecular genetic level they study the physical chemical processes, occurring in the body (synthesis and breakdown of proteins, nucleic acids, lipids, metabolism and energy, copying of genetic information). The monotony of discrete units is noted. Four nitrogenous bases are part of nucleic acids. Twenty amino acids form protein molecules. An elementary unit - a gene - is a section of a DNA molecule containing certain genetic information. An elementary phenomenon is the reduplication (self-reproduction) of DNA molecules, which is carried out according to the principle of template synthesis. The genetic information contained in the genes is copied, which ensures the continuity and preservation of the properties of organisms in subsequent generations. During reduplication, various disorders can occur that change the genetic information (gene mutations), which form the basis of variability. 18
Levels of organization of living matter Cellular level. The cell is the basic structural, functional and genetic unit of organization of all living organisms. An elementary phenomenon is the reactions of cellular metabolism. At the cellular level, the structure of cells and cellular components is studied. Metabolism that occurs at the cellular level is necessary for life to occur at other levels. 19
Levels of organization of living matter. Ontogenetic level. The elementary unit of life at this level is the individual (organism). At the ontogenetic level, they study the processes occurring in the body, from the moment of its inception until the end of life: structural features, physiology, adaptation mechanisms, behavior, etc. Changes occurring throughout the entire period of individual development of an individual constitute an elementary phenomenon at this level. Characteristic is the variety of forms associated with spatial combinations that determine new qualitative characteristics of the organism. The processes of normal ontogenesis can be disrupted by unusual influences. Any physical and chemical factors of the external environment, to which organisms do not have adaptations developed during the process of evolution, can negatively affect reproduction. For example, some chemicals have a teratogenic (causing various deformities) effect. 20
Levels of organization of living matter Population-species level. An elementary unit - a population - is a collection of individuals of the same species inhabiting a certain territory, capable of interbreeding with each other and partially or completely isolated from other populations of the same species. In this system, elementary evolutionary transformations occur, such as natural selection, mutations. At the population-species level, factors influencing the size of populations, their sexual composition, problems of preserving endangered species, etc. are studied. 21
Levels of organization of living matter Biogeocenotic and biosphere levels. The elementary structure - biogeocenosis - is a historically established stable community of plants, animals and microorganisms that are in constant interaction with the components of the atmosphere, hydrosphere and lithosphere, i.e. integral self-regulating and self-sustaining system. The biosphere represents the totality of all biogeocenoses, forming a single complex covering all phenomena of life on the planet. An elementary phenomenon at the biosphere level is associated with the circulation of substances and energy that occurs with the participation of living organisms. 22
All levels of organization of living things are closely interconnected, which indicates the integrity of living nature. Without biological processes carried out at these levels, the evolution and existence of life on Earth is impossible. At a certain stage of evolutionary development, man appeared. Social relationships play a major role in his life. But man and all of humanity are component biosphere, its health depends on the ability to adapt to changing environmental conditions. If this ability is not sufficiently manifested, then diseases may arise that affect various levels of life organization (cellular, ontogenetic). 23
Forms of existence of living matter All living organisms living on Earth are divided into two groups. The first group includes viruses and phages that do not have a cellular structure. The second includes all other organisms for which various cells are the main structural unit. 24
Forms of existence of living matter Complex viruses have an outer shell called a supercapsid. It is constructed from the plasma membrane of the host cell. Complex viruses include herpes viruses (1), influenza, AIDS, etc. Viruses differ from each other in the shape of the capsid and the structure of the shell. 26
Cellular forms Most living organisms living on Earth have a cellular structure. In the process of evolution of the organic world, the cell turned out to be the only elementary system in which the manifestation of all the laws that characterize life is possible. Taking into account the structural features of cells, all living organisms are divided into prokaryotes and eukaryotes. 29
Prokaryotic cells. These are organisms with an unformed nucleus, represented by bacteria and blue-green algae. Most of them are small in size (up to 10 microns) and have round, oval or elongated cell shapes. The genetic material (DNA) of a single ring chromosome is located in the cytoplasm and is not separated from it by a membrane. This analogue of the nucleus is called a nucleoid. thirty
Eukaryotic cells. A cell is the basic structural, functional and genetic unit of organization of living things, an elementary living system. A cell can exist as a separate organism (bacteria, protozoa, some algae and fungi) or as part of the tissues of multicellular animals, plants, and fungi. 31
1.Chemical composition. Living beings consist of the same chemical elements as non-living ones, but organisms contain molecules of substances characteristic only of living things (nucleic acids, proteins, lipids).
2.Discreteness and integrity. Any biological system (cell, organism, species, etc.) consists of individual parts, i.e. discrete. The interaction of these parts forms an integral system (for example, the body includes individual organs connected structurally and functionally into a single whole).
3.Structural organization. Living systems are capable of creating order from the chaotic movement of molecules, forming certain structures. Living things are characterized by orderliness in space and time. This is a complex of complex self-regulating metabolic processes occurring in a strictly defined order, aimed at maintaining a constant internal environment - homeostasis.
4.Metabolism and energy. Living organisms are open systems that constantly exchange matter and energy with the environment. When environmental conditions change, self-regulation of life processes occurs according to the feedback principle, aimed at restoring the constancy of the internal environment - homeostasis. For example, waste products can have a strong and strictly specific inhibitory effect on those enzymes that formed the initial link in a long chain of reactions.
5.Self-reproduction. Self-renewal. The lifetime of any biological system is limited. To maintain life, a process of self-reproduction occurs, associated with the formation of new molecules and structures that carry genetic information found in DNA molecules.
6.Heredity. The DNA molecule is capable of storing and transmitting hereditary information, thanks to the matrix principle of replication, ensuring material continuity between generations.
7.Variability. When transmitting hereditary information, various deviations sometimes arise, leading to changes in characteristics and properties in descendants. If these changes favor life, they can be fixed by selection.
8.Growth and development. Organisms inherit certain genetic information about the possibility of developing certain characteristics. The implementation of information occurs during individual development - ontogenesis. At a certain stage of ontogenesis, the growth of the organism occurs, associated with the reproduction of molecules, cells and other biological structures. Growth is accompanied by development.
9. Irritability and movement. All living things selectively react to external influences with specific reactions due to the property of irritability. Organisms respond to stimulation with movement. The manifestation of the form of movement depends on the structure of the body.
3. Manifestations of life on our planet extremely diverse. In this regard, various levels of organization of living matter are distinguished, which reflect the subordination and hierarchy of the structural organization of life. The concept of levels of organization is based on the principle of discreteness.
Molecular level. The elementary units of this level of life organization are chemical substances: nucleic acids, proteins, carbohydrates, lipids, etc. At this level, such important life processes as the transfer of hereditary information, biosynthesis, energy conversion, etc. are mainly manifested. The main strategy of life is at the molecular level - the ability to create living matter and encode information acquired in changing environmental conditions.
On cellular at the organizational level, the structural elements are various organelles. The ability to reproduce one’s own kind, the inclusion of various chemical elements of the Earth into the composition of the cell, the regulation of chemical reactions, the storage and consumption of energy are the main processes of this level. The strategy of life at the cellular level is the involvement of the chemical elements of the Earth and the energy of the Sun into living systems.
Organismal the level of organization is inherent in unicellular and multicellular biosystems (plants, fungi, animals, including humans and various microorganisms). Living organisms exhibit such properties as nutrition, respiration, excretion, irritability, growth and development, reproduction, behavior, life expectancy, and relationships with the environment. All of these processes together characterize the body as an integral self-regulating biosystem. The main strategy of life at this level is the orientation of the organism (individual) towards survival in constantly changing environmental conditions.
Population-species The level of organization is characterized by the unification of related individuals into populations, and populations into species, which leads to the emergence of new properties of the system. The main properties of this level: fertility, mortality, survival, structure (gender, age, environmental), density, number, functioning in nature. The main strategy of the population-species level is manifested in a more complete use of the capabilities of the habitat, in the desire for the longest possible existence, in preserving the properties of the species and independent development.
On biogeocenotic (ecosystem) level of organization, the main structural elements are populations of different species. This level is characterized by many properties. These include: the structure of the ecosystem, the species and quantitative composition of its population, types of biotic connections, food chains and networks, trophic levels, productivity, energy, sustainability, etc. Organizing properties are manifested in the circulation of substances and the flow of energy, self-regulation and stability, autonomy, openness of the system, seasonal changes. The main strategy of this level is the active use of the entire diversity of the environment and the creation of favorable conditions for the development and prosperity of life in all its diversity.
The highest level of organization of life is biosphere. The main structural units of this level are biogeocenoses (ecosystems) and their environment, i.e. geographic envelope Earth (atmosphere, hydrosphere, soil, solar radiation, etc.) and anthropogenic impact. For this level, the organ and organizations are characterized by: active interaction of living and nonliving matter of the planet; biological circulation of substances and energy flows with geochemical cycles included in it; economic and ethnocultural activities of humans. The main strategy of life at the biosphere level is the desire to ensure the dynamic stability of the biosphere as the largest ecosystem on our planet.
cellular; cell biology (cytology) is one of the main. sections of modern biology, includes problems of morphological. cell organizations, cell specialization during development, cell membrane functions, mechanisms and regulation of cell division. These problems are of particular importance for medicine, in particular, forming the basis of the problem of cancer.
At the organismal level study the individual and its characteristic structural features as a whole, physiol. processes, including differentiation, mechanisms of adaptation (acclimation) and behavior, in particular neurohumoral regulation mechanisms, central nervous system functions. At the organ-tissue level The main problems are to study the structural features and functions of the department. organs and their tissue components
