The natural world is a collection biological systems different levels of organization and different subordination. They are in constant interaction. There are several levels of living matter:

Molecular- any living system, no matter how complex it is organized, manifests itself at the level of functioning of biological macromolecules: nucleic acids, proteins, polysaccharides, as well as important organic matter. From this level, the most important processes of the body's vital activity begin: metabolism and energy conversion, transfer hereditary information and others - the most ancient level of the structure of living nature, bordering on inanimate nature.

Cellular- a cell is a structural and functional unit, also a unit of reproduction and development of all living organisms living on Earth. There are no non-cellular life forms, and the existence of viruses only confirms this rule, since they can exhibit the properties of living systems only in cells.

Tissue- Tissue is a collection of cells similar in structure, united by the performance of a common function.

Organ- in most animals, an organ is a structural and functional combination of several types of tissues. For example, human skin as an organ includes epithelium and connective tissue, which together perform a number of functions, among which the most significant is protective.

Organismic- a multicellular organism is an integral system of organs specialized to perform various functions. Differences between plants and animals in the structure and methods of nutrition. The relationship of organisms with the environment, their adaptability to it.

population-species- a set of organisms of the same species, united by a common habitat, creates a population as a system of a supra-organismal order. In this system, the simplest, elementary evolutionary transformations are carried out.

Biogeocenotic- biogeocenosis - a set of organisms different types and varying complexity of organization, all environmental factors.

biospheric The biosphere is the highest level of organization of living matter on our planet, including all life on Earth. Thus, living nature is a complexly organized hierarchical system.

2. Reproduction at the cellular level, mitosis and its biological role

Mitosis (from Greek mitos - thread), a type of cell division, as a result of which daughter cells receive genetic material identical to that contained in the mother cell. Karyokinesis, indirect cell division, is the most common method of cell reproduction (reproduction), which ensures the identical distribution of genetic material between daughter cells and the continuity of chromosomes in a number of cell generations.

Rice. 1. Scheme of mitosis: 1, 2 - prophase; 3 - prometaphase; 4 - metaphase; 5 - anaphase; 6 - early telophase; 7 - late telophase

The biological significance of mitosis is determined by the combination of the doubling of chromosomes in it by means of their longitudinal splitting and uniform distribution between daughter cells. The onset of mitosis is preceded by a period of preparation, including the accumulation of energy, the synthesis of deoxyribonucleic acid (DNA), and the reproduction of centrioles. The source of energy is rich in energy, or the so-called macroergic compounds. Mitosis is not accompanied by an increase in respiration, since oxidative processes occur in the interphase (the filling of the “energy reserve of the macaw”). Periodic filling and emptying of the energy reserve of the macaw is the basis of the energy of mitosis.

The stages of mitosis are as follows. Single process. Mitosis is usually divided into 4 stages: prophase, metaphase, anaphase, and telophase.

Rice. Fig. 2. Mitosis in the meristematic cells of the onion root (micrograph). Interphase

Rice. Fig. 3. Mitosis in the meristematic tufts of the onion root (micrograph). Prophase (loose tangle figure)

Rice. 4. Mitosis in the meristematic cells of the onion root (micrograph). Late prophase (destruction of the nuclear membrane)

METAPHASE - consists in the movement of CHROMOSOMES to the equatorial plane (metakinesis, or prometaphase), the formation of the equatorial PLATE ("mother star") and in the separation of chromatids, or sister chromosomes.

Rice. Fig. 5. Mitosis in the meristematic cells of the onion root (micrograph). prometaphase

Fig.6. Mitosis in the meristematic cells of the onion root (micrograph). metaphase

Rice. Fig. 7. Mitosis in the meristematic cells of the onion root (micrograph). Anaphase

Anaphase - the stage of divergence of chromosomes to the poles. Anaphase movement is associated with the elongation of the central filaments of VERETIN, which pushes the mitotic poles apart, and with the shortening of the chromosomal MICROTUBES of the mitotic apparatus. The elongation of the central filaments of the SPINDLE occurs either due to the POLARIZATION of "reserve macromolecules" that complete the construction of the MICROTUBES of the spindle, or due to the dehydration of this structure. The shortening of chromosomal microtubules is provided by the PROPERTIES of the contractile proteins of the mitotic apparatus, which are capable of contraction without thickening. TELOPHASE - consists in the reconstruction of daughter nuclei from chromosomes gathered at the poles, the division of the cell body (CYTOTHYMIA, CYTOKINESIS) and the final destruction of the mitotic apparatus with the FORMATION of an intermediate body. Reconstruction of daughter nuclei is associated with chromosome desperalization, RESTORATION of the nucleolus and nuclear envelope. Cytotomy is carried out by the formation of a cell plate (in a plant cell) or by the formation of a fission furrow (in an animal cell).

Fig.8. Mitosis in the meristematic cells of the onion root (micrograph). Early telophase

Rice. Fig. 9. Mitosis in the meristematic cells of the onion root (micrograph). late telophase

The mechanism of cytotomy is associated either with the contraction of the gelatinized ring of the CYTOPLASMA encircling the EQUATOR (the "contractile ring" hypothesis) or with the expansion of the cell surface due to the straightening of the loop-like protein chains (the "MEMBRANE expansion" hypothesis).

Mitosis duration- depends on the size of the cells, their ploidy, the number of nuclei, as well as on the conditions environment, in particular on temperature. Mitosis lasts 30–60 minutes in animal cells, and 2–3 hours in plant cells. Longer stages of mitosis associated with the processes of synthesis (preprophase, prophase, telophase) self-movement of chromosomes (metakinesis, anaphase) is carried out quickly.

THE BIOLOGICAL SIGNIFICANCE OF MITOSIS - the constancy of the structure and the correct functioning of the organs and tissues of a multicellular organism would be impossible without the preservation of the same set of genetic material in countless cell generations. Mitosis provides important manifestations of vital activity: embryonic development, growth, restoration of organs and tissues after damage, maintenance of the structural integrity of tissues with constant loss of cells in the course of their functioning (replacement of dead erythrocytes, skin cells, intestinal epithelium, etc.) In protozoa, mitosis provides asexual reproduction.

3. Gametogenesis, characterization of germ cells, fertilization

Sex cells (gametes) - male spermatozoa and female eggs (or eggs) develop in the sex glands. In the first case, the path of their development is called SPERMATOGENESIS (from the Greek sperm - seed and genesis - origin), in the second - OVOGENESIS (from Latin ovo - egg)

Gametes are sex cells, their participation in fertilization, the formation of a zygote (the first cell of a new organism). The result of fertilization is the doubling of the number of chromosomes, the restoration of their diploid set in the zygote. Features of gametes are a single, haploid set of chromosomes compared to the diploid set of chromosomes in body cells2. Stages of development of germ cells: 1) increase by mitosis in the number of primary germ cells with a diploid set of chromosomes, 2) growth of primary germ cells, 3) maturation of germ cells.

STAGES OF GAMETOGENESIS - in the process of development of sexual both spermatozoa and eggs, stages are distinguished (fig.). The first stage is the period of reproduction, in which the primary germ cells divide by mitosis, as a result of which their number increases. During spermatogenesis, the reproduction of primary germ cells is very intense. It begins with the onset of puberty and proceeds throughout the entire reproductive period. Reproduction of female primary germ cells in lower vertebrates continues almost all life. In humans, these cells multiply with the greatest intensity only in the prenatal period of development. After the formation of the female sex glands - the ovaries, the primary germ cells stop dividing, most of them die and are absorbed, the rest remain dormant until puberty.

The second stage is the period of growth. In immature male gametes, this period is expressed unsharply. The sizes of male gametes increase slightly. On the contrary, future eggs - oocytes sometimes increase hundreds, thousands and even millions of times. In some animals, oocytes grow very quickly - within a few days or weeks, in others, growth continues for months and years. The growth of oocytes is carried out due to substances formed by other cells of the body.

The third stage is the period of maturation, or meiosis (Fig. 1).

Rice. 9. Scheme of the formation of germ cells

Cells entering the period of meiosis contain a diploid set of chromosomes and already double the amount of DNA (2n 4c).

In the process of sexual reproduction, organisms of any species from generation to generation retain their characteristic number of chromosomes. This is achieved by the fact that before the fusion of germ cells - fertilization - in the process of maturation, the number of chromosomes decreases (reduces) in them, i.e. from a diploid set (2n) a haploid set (n) is formed. The patterns of meiosis in male and female germ cells are essentially the same.

Bibliography

Gorelov A. A. Concepts of modern natural science. — M.: Center, 2008.


Dubnishcheva T.Ya. etc. Modern natural science. — M.: Marketing, 2009.


Lebedeva N.V., Drozdov N.N., Krivolutsky D.A. biological diversity. M., 2004.


Mamontov S.G. Biology. M., 2007.


Yarygin V. Biology. M., 2006.


The following levels of life organization are distinguished: molecular, cellular, organ-tissue (sometimes they are separated), organismic, population-species, biogeocenotic, biospheric. Live nature is a system, and the various levels of its organization form its complex hierarchical structure, when the underlying simpler levels determine the properties of the overlying ones.

So complicated organic molecules are part of the cells and determine their structure and vital activity. In multicellular organisms, cells are organized into tissues, and several tissues form an organ. A multicellular organism consists of organ systems, on the other hand, the organism itself is an elementary unit of a population and biological species. The community is represented by interacting populations of different species. The community and the environment form a biogeocenosis (ecosystem). The totality of ecosystems of the planet Earth forms its biosphere.

At each level, new properties of living things arise, which are absent at the underlying level, their own elementary phenomena and elementary units are distinguished. At the same time, the levels largely reflect the course of the evolutionary process.

The allocation of levels is convenient for studying life as a complex natural phenomenon.

Let's take a closer look at each level of organization of life.

Molecular level

Although molecules are made up of atoms, the difference between living matter and non-living matter begins to manifest itself only at the level of molecules. Only found in living organisms a large number of complex organic substances - biopolymers (proteins, fats, carbohydrates, nucleic acids). However molecular level The organization of living things also includes inorganic molecules that enter cells and play an important role in their life activity.

The functioning of biological molecules underlies the living system. At the molecular level of life, metabolism and energy conversion are manifested as chemical reactions, the transfer and change of hereditary information (reduplication and mutations), as well as a number of other cellular processes. Sometimes the molecular level is called the molecular genetic level.

Cellular level of life

It is the cell that is structural and functional unit alive. There is no life outside the cell. Even viruses can exhibit the properties of a living being only once they are in the host cell. Biopolymers fully show their reactivity when organized into a cell, which can be considered as complex system interconnected in the first place by various chemical reactions of molecules.

At this cellular level, the phenomenon of life manifests itself, the mechanisms of transmission of genetic information and the transformation of substances and energy are conjugated.

Organ tissue

Only multicellular organisms have tissues. Tissue is a collection of cells similar in structure and function.

Tissues are formed in the process of ontogenesis by differentiation of cells that have the same genetic information. At this level, cell specialization occurs.

Plants and animals have different types of tissues. So in plants it is a meristem, a protective, basic and conductive tissue. In animals - epithelial, connective, muscular and nervous. The fabrics may include a list of subfabrics.

An organ usually consists of several tissues, united among themselves in a structural and functional unity.

Organs form organ systems, each of which is responsible for an important function for the body.

The organ level in unicellular organisms is represented by various cell organelles that perform the functions of digestion, excretion, respiration, etc.

Organismal level of organization of living

Along with the cellular at the organismal (or ontogenetic) level, separate structural units are distinguished. Tissues and organs cannot live independently, organisms and cells (if it is a unicellular organism) can.

Multicellular organisms are made up of organ systems.

At the organismic level, such phenomena of life as reproduction, ontogeny, metabolism, irritability, neuro-humoral regulation, homeostasis are manifested. In other words, its elementary phenomena constitute regular changes in the organism in individual development. The elementary unit is the individual.

population-species

Organisms of the same species, united by a common habitat, form a population. A species usually consists of many populations.

Populations share a common gene pool. Within a species, they can exchange genes, that is, they are genetically open systems.

In populations, elementary evolutionary phenomena occur, ultimately leading to speciation. Living nature can evolve only in supra-organismal levels.

At this level, the potential immortality of the living arises.

Biogeocenotic level

Biogeocenosis is an interacting set of organisms of different species with different environmental factors. Elementary phenomena are represented by matter-energy cycles, provided primarily by living organisms.

The role of the biogeocenotic level consists in the formation of stable communities of organisms of different species, adapted to living together in a certain habitat.

Biosphere

The biospheric level of life organization is a higher-order system of life on Earth. The biosphere encompasses all manifestations of life on the planet. At this level, the global circulation of substances and the flow of energy (covering all biogeocenoses) take place.

LEVELS OF LIVING ORGANIZATION

There are molecular, cellular, tissue, organ, organism, population, species, biocenotic and global (biospheric) levels of organization of the living. At all these levels, all the properties characteristic of living things are manifested. Each of these levels is characterized by features inherent in other levels, but each level has its own specific features.

Molecular level. This level is deep in the organization of the living and is represented by molecules of nucleic acids, proteins, carbohydrates, lipids and steroids that are in cells and are called biological molecules. At this level, the most important processes of vital activity (coding and transmission of hereditary information, respiration, metabolism and energy metabolism, variability, etc.) are initiated and carried out. The physicochemical specificity of this level lies in the fact that a large number of chemical elements, but the bulk of life is represented by carbon, oxygen, hydrogen and nitrogen. Molecules are formed from a group of atoms, and complex chemical compounds are formed from the latter, differing in structure and function. Most of these compounds in cells are represented by nucleic acids and proteins, the macromolecules of which are polymers synthesized as a result of the formation of monomers and the combination of the latter in a certain order. In addition, the monomers of macromolecules within the same compound have the same chemical groups and are connected using chemical bonds between atoms, their nonspecific

ical parts (areas). All macromolecules are universal, as they are built according to the same plan, regardless of their species. Being universal, they are at the same time unique, because their structure is unique. For example, the composition of DNA nucleotides includes one nitrogenous base of the four known (adenine, guanine, cytosine or thymine), as a result of which any nucleotide is unique in its composition. The secondary structure of DNA molecules is also unique.

The biological specificity of the molecular level is determined by the functional specificity of biological molecules. For example, the specificity of nucleic acids lies in the fact that they encode the genetic information for protein synthesis. Moreover, these processes are carried out as a result of the same stages of metabolism. For example, the biosynthesis of nucleic acids, amino acids, and proteins follows a similar pattern in all organisms. Oxidation is also universal fatty acids, glycolysis and other reactions.

The specificity of proteins is determined by the specific sequence of amino acids in their molecules. This sequence further defines the specific biological properties of proteins, since they are the main building blocks cells, catalysts and regulators of reactions in cells. Carbohydrates and lipids serve as the most important sources of energy, while steroids are important for the regulation of a number of metabolic processes.

At the molecular level, energy is converted - radiant energy into chemical energy stored in carbohydrates and other chemical compounds, and the chemical energy of carbohydrates and other molecules - into biologically available energy stored in the form of macroergic bonds of ATP. Finally, here the energy of high-energy phosphate bonds is converted into work - mechanical, electrical, chemical, osmotic. The mechanisms of all metabolic and energy processes are universal.

Biological molecules also provide continuity between molecules and the next level (cellular), as they are the material from which supramolecular structures are formed. The molecular level is the "arena" chemical reactions that provide energy to the cellular level.

Cellular level. This level of organization of the living is represented by cells acting as independent organizations.

mov (bacteria, protozoa, etc.), as well as cells of multicellular organisms. The main specific feature of this level is that life begins from it. Being capable of life, growth and reproduction, cells are the main form of organization of living matter, the elementary units from which all living beings (prokaryotes and eukaryotes) are built. There are no fundamental differences in structure and function between plant and animal cells. Some differences relate only to the structure of their membranes and individual organelles. There are noticeable differences in structure between prokaryotic cells and eukaryotic cells, but in functional terms, these differences are leveled, because the “cell from cell” rule applies everywhere.

The specificity of the cellular level is determined by the specialization of cells, the existence of cells as specialized units of a multicellular organism. At the cellular level, there is a differentiation and ordering of vital processes in space and time, which is associated with the confinement of functions to different subcellular structures. For example, eukaryotic cells have significantly developed membrane systems (plasma membrane, cytoplasmic reticulum, lamellar complex) and cell organelles (nucleus, chromosomes, centrioles, mitochondria, plastids, lysosomes, ribosomes). Membrane structures are the "arena" of the most important life processes, and the two-layer structure of the membrane system significantly increases the area of ​​the "arena". In addition, membrane structures provide spatial separation of many biological molecules in cells, and their physical state allows for the constant diffuse movement of some of the protein and phospholipid molecules contained in them. Thus, membranes are a system whose components are in motion. They are characterized by various rearrangements, which determines the irritability of cells - the most important property alive.

tissue level. This level is represented by tissues that combine cells of a certain structure, size, location and similar functions. The tissues arose during historical development along with multicellularity. In multicellular organisms, they are formed during ontogenesis as a result of cell differentiation. In animals, several types of tissues are distinguished (epithelial, connective, muscle, blood, nervous and reproductive). The races

shadows distinguish meristematic, protective, basic and conductive tissues. At this level, cell specialization occurs.

Organ level. Represented by organs of organisms. In plants and animals, organs are formed due to a different number of tissues. In protozoa, digestion, respiration, circulation of substances, excretion, movement and reproduction are carried out by various organelles. More advanced organisms have organ systems. Vertebrates are characterized by cephalization, which consists in the concentration of the most important nerve centers and sensory organs in the head.

Organism level. This level is represented by the organisms themselves - unicellular and multicellular organisms of plant and animal nature. A specific feature of the organismic level is that at this level the decoding and implementation of genetic information, the creation of structural and functional features inherent in organisms of a given species take place.

species level. This level is determined by plant and animal species. Currently, there are about 500 thousand plant species and about 1.5 million animal species, whose representatives are characterized by a wide variety of habitats and occupy different ecological niches. A species is also a unit of classification of living beings.

population level. Plants and animals do not exist in isolation; they are united in populations that are characterized by a certain gene pool. Within the same species, there can be from one to many thousands of populations. Elementary evolutionary transformations are carried out in populations, a new adaptive form is being developed.

Biocenotic level. It is represented by biocenoses - communities of organisms of different species. In such communities, organisms of different species depend to some extent on each other. In the course of historical development, biogeocenoses (ecosystems) have developed, which are systems consisting of interdependent communities of organisms and abiotic environmental factors. Ecosystems have a fluid balance between organisms and abiotic factors. At that level, the material-energy cycles associated with the vital activity of organisms are carried out.

Global (biospheric) level. This level is the highest form organization of the living (living systems). It is represented by the biosphere. At this level, all matter-energy cycles are united into a single giant biospheric cycle of substances and energy.

There is a dialectical unity between different levels of organization of the living. The living is organized according to the type of systemic organization, the basis of which is the hierarchy of systems. The transition from one level to another is associated with the preservation of the functional mechanisms operating at the previous levels, and is accompanied by the appearance of a structure and functions of new types, as well as an interaction characterized by new features, i.e., a new quality appears.

In the organization of the living, molecular, cellular, tissue, organ, organism, population, species, biocenotic and global (biospheric) levels are mainly distinguished. At all these levels, all the properties characteristic of living things are manifested. Each of these levels is characterized by features inherent in other levels, but each level has its own specific features.

Molecular level. This level is deep in the organization of the living and is represented by molecules of nucleic acids, proteins, carbohydrates, lipids, and steroids found in cells and, as already noted, called biological molecules.

The sizes of biological molecules are characterized by a rather significant variety, which is determined by the space they occupy in living matter. The smallest biological molecules are nucleotides, amino acids and sugars. On the contrary, protein molecules are characterized by much larger sizes. For example, the diameter of a human hemoglobin molecule is 6.5 nm.

Biological molecules are synthesized from low molecular weight precursors, which are carbon monoxide, water and atmospheric nitrogen, and which in the process of metabolism are converted through intermediate compounds of increasing molecular weight (building blocks) into biological macromolecules with a large molecular weight(Fig. 42). At this level, the most important processes of vital activity begin and are carried out (coding and transmission of hereditary information, respiration, metabolism and energy, variability, etc.).

The physicochemical specificity of this level lies in the fact that the composition of the living includes a large number of chemical elements, but the main elemental composition of the living is represented by carbon, oxygen, hydrogen, nitrogen. Molecules are formed from groups of atoms, and complex chemical compounds are formed from the latter, differing in structure and function. Most of these compounds in cells are represented by nucleic acids and proteins, the macromolecules of which are polymers synthesized as a result of the formation of monomers, and the compounds of the latter in a certain order. In addition, the monomers of macromolecules within the same compound have the same chemical groups and are connected using chemical bonds between the atoms of their nonspecific parts (sites).

All macromolecules are universal, because they are built according to the same plan, regardless of their species. Being universal, they are at the same time unique, because their structure is unique. For example, the composition of DNA nucleotides includes one nitrogenous base of the four known (adenine, guanine, cytosine and thymine), as a result of which any nucleotide or any sequence of nucleotides in DNA molecules is unique in its composition, just as the secondary structure of the DNA molecule is also unique. Most proteins contain 100-500 amino acids, but the sequences of amino acids in protein molecules are unique, which makes them unique.

Combining, macromolecules different types form supramolecular structures, examples of which are nucleoproteins, which are complexes of nucleic acids and proteins, lipoproteins (complexes of lipids and proteins), ribosomes (complexes of nucleic acids and proteins). In these structures, the complexes are bound non-covalently, but non-covalent binding is very specific. Biological macromolecules are characterized by continuous transformations, which are provided by chemical reactions catalyzed by enzymes. In these reactions, enzymes convert a substrate into a reaction product within an extremely short time, which can be a few milliseconds or even microseconds. For example, the unwinding time of a double-stranded DNA helix before its replication is only a few microseconds.

The biological specificity of the molecular level is determined by the functional specificity of biological molecules. For example, the specificity of nucleic acids lies in the fact that they encode the genetic information for protein synthesis. This property is not shared by other biological molecules.

The specificity of proteins is determined by the specific sequence of amino acids in their molecules. This sequence further determines the specific biological properties of proteins, since they are the main structural elements of cells, catalysts and regulators of various processes occurring in cells. Carbohydrates and lipids are the most important sources of energy, while steroids in the form of steroid hormones are important for the regulation of a number of metabolic processes.

The specificity of biological macromolecules is also determined by the fact that the processes of biosynthesis are carried out as a result of the same stages of metabolism. Moreover, the biosynthesis of nucleic acids, amino acids and proteins proceeds according to a similar pattern in all organisms, regardless of their species. Fatty acid oxidation, glycolysis, and other reactions are also universal. For example, glycolysis occurs in every living cell of all eukaryotic organisms and is carried out as a result of 10 consecutive enzymatic reactions, each of which is catalyzed by a specific enzyme. All aerobic eukaryotic organisms have molecular "machines" in their mitochondria, where the Krebs cycle and other reactions associated with the release of energy take place. At the molecular level, many mutations occur. These mutations change the sequence of nitrogenous bases in DNA molecules.

At the molecular level, radiant energy is fixed and this energy is converted into chemical energy stored in cells in carbohydrates and other chemical compounds, and the chemical energy of carbohydrates and other molecules into biologically available energy stored in the form of ATP macroenergy bonds. Finally, at this level, the energy of macroergic phosphate bonds is converted into work - mechanical, electrical, chemical, osmotic, the mechanisms of all metabolic and energy processes are universal.

Biological molecules also provide continuity between the molecular and the next level (cellular), since they are the material from which supramolecular structures are formed. The molecular level is the "arena" of chemical reactions that provide energy to the cellular level.

Cellular level. This level of organization of living things is represented by cells acting as independent organisms (bacteria, protozoa, and others), as well as cells of multicellular organisms. The main specific feature of this level is that life begins from it. Being capable of life, growth and reproduction, cells are the basic form of organization of living matter, elementary units from which all living beings (prokaryotes and eukaryotes) are built. There are no fundamental differences in structure and function between plant and animal cells. Some differences relate only to the structure of their membranes and individual organelles. There are noticeable differences in structure between prokaryotic cells and cells of eukaryotic organisms, but in functional terms, these differences are leveled, because the “cell from cell” rule applies everywhere. Supramolecular structures at this level form membrane systems and cell organelles (nuclei, mitochondria, etc.).

The specificity of the cellular level is determined by the specialization of cells, the existence of cells as specialized units of a multicellular organism. At the cellular level, there is a differentiation and ordering of vital processes in space and time, which is associated with the confinement of functions to different subcellular structures. For example, eukaryotic cells have significantly developed membrane systems (plasma membrane, cytoplasmic reticulum, lamellar complex) and cell organelles (nucleus, chromosomes, centrioles, mitochondria, plastids, lysosomes, ribosomes).

Membrane structures are the "arena" of the most important life processes, and the two-layer structure of the membrane system significantly increases the area of ​​the "arena". In addition, membrane structures ensure the separation of cells from the environment, as well as the spatial separation of many biological molecules in cells. The cell membrane has a highly selective permeability. Therefore, their physical condition allows the constant diffuse movement of some of the protein and phospholipid molecules they contain. In addition to general-purpose membranes, cells have internal membranes that limit cell organelles.

By regulating the exchange between the cell and the environment, membranes have receptors that perceive external stimuli. In particular, examples of the perception of external stimuli are the perception of light, the movement of bacteria to a food source, the response of target cells to hormones, such as insulin. Some of the membranes themselves simultaneously generate signals (chemical and electrical). "A remarkable feature of the membranes is that energy conversion occurs on them. In particular, photosynthesis occurs on the inner membranes of chloroplasts, while oxidative phosphorylation occurs on the inner membranes of the mitochondria.

Membrane components are in motion. Built mainly from proteins and lipids, membranes are characterized by various rearrangements, which determines the irritability of cells - the most important property of the living.

tissue level represented by tissues that combine cells of a certain structure, size, location and similar functions. Tissues arose in the course of historical development along with multicellularity. In multicellular organisms, they are formed during ontogenesis as a result of cell differentiation. In animals, several types of tissues are distinguished (epithelial, connective, muscle, nervous, as well as blood and lymph). In plants, meristematic, protective, basic and conductive tissues are distinguished. At this level, cell specialization occurs.

Organ level. Represented by organs of organisms. In protozoa, digestion, respiration, circulation of substances, excretion, movement and reproduction are carried out by various organelles. More advanced organisms have organ systems. In plants and animals, organs are formed due to a different number of tissues. Vertebrates are characterized by cephalization, which is protected by the concentration of the most important centers and sense organs in the head.

Organism level. This level is represented by the organisms themselves - unicellular and multicellular organisms of plant and animal nature. A specific feature of the organismic level is that at this level, the decoding and implementation of genetic information, the creation of structural and functional features inherent in organisms of this species takes place. Organisms are unique in nature because their genetic material is unique, which determines their development, functions, and their relationship with the environment.

population level. Plants and animals do not exist in isolation; they are grouped together in a population. By creating a supraorganismal system, populations are characterized by a certain gene pool and a certain habitat. In populations, elementary evolutionary transformations also begin, and an adaptive form is developed.

species level. This level is determined by the species of plants, animals and microorganisms that exist in nature as living links. The population composition of the species is extremely diverse. One species can include from one to many thousands of populations, whose representatives are characterized by a wide variety of habitats and occupy different ecological niches. Species are the result of evolution and are characterized by turnover. The species that exist today are not like the species that existed in the past. A species is also a unit of classification of living beings.

Biocenotic level. It is represented by biocenoses - communities of organisms of different species. In such communities, organisms of different species depend to some extent on each other. In the course of historical development, biogeocenoses (ecosystems) have developed, which are systems consisting of interdependent communities of organisms and abiotic environmental factors. Ecosystems are characterized by a dynamic (mobile) balance between organisms and abiotic factors. At this level, the material-energy cycles associated with the vital activity of organisms are carried out.

Biosphere (global) level. This level is the highest form of organization of the living (living systems). It is represented by the biosphere. At this level, all matter-energy cycles are united into a single giant biospheric cycle of substances and energy.

Between different levels of organization of the living there is a dialectical unity, the living is organized according to the type of system organization, the basis of which is the hierarchy of systems. The transition from one level to another is associated with the preservation of the functional mechanisms operating at the previous levels, and is accompanied by the appearance of a structure and functions of new types, as well as an interaction characterized by new features, i.e., is associated with the emergence of a new quality.

Issues for discussion

1. What is the general methodological approach to understanding the essence of life? When did it arise and why?

2. Is it possible to define the essence of life? If so, what is this definition and what are its scientific justification?

3. Is it possible to raise the question of the substratum of life?

4. Name the properties of the living. Indicate which of these properties are characteristic of non-living things and which are only for living things.

5. What is the importance for biology of the division of the living into levels of organization? Does such a subdivision have any practical value?

6. What are the common features of different levels of organization of living things?

7. Why are nucleoproteins considered the substrate of life and under what conditions do they fulfill this role?

Literature

Faithful D. The emergence of life M.: Mir. 1969. 391 pages.

Oparin A.V. Matter, life, intellect. M.: Science. 1977. 204 pages

Pekhov A.P. Biology and scientific and technical progress. M: Knowledge. 1984. 64 pages.

Karcher S. J. Molecular Biology. Acad. Press. 1995. 273pp.

Murphy M. P., O "Neill L. A. (Eds.) What is Life? The Next Fifty Years. Cambridge University Press. 1995. 203 pp.

Levels of organization of wildlife

Allocate 8 levels.

Each level of organization is characterized by a specific structure (chemical, cellular or organismal) and the corresponding properties.

Each next level necessarily contains all the previous ones.


Let's take a look at each level in detail.

8 levels of wildlife organization


1. Molecular level of organization of living nature

• : organic and inorganic substances,
• (metabolism): processes of dissimilation and assimilation,
• absorption and release of energy.

The molecular level affects all biochemical processes that occur inside any living organism - from unicellular to multicellular.

This level difficult to call "alive". It is rather a "biochemical" level - therefore it is the basis for all other levels of organization of living nature.

Therefore, it was he who formed the basis of the classification to the kingdoms which nutrient is the main one in the body: in animals -, in fungi - chitin, in plants it is -.

Sciences that study living organisms at this level:

2. Cellular level of wildlife organization

Includes previous - molecular level of organization.

At this level, the term "" already appears as "the smallest indivisible biological system"

• The metabolism and energy of a given cell (different depending on which kingdom the organism belongs to);
• Organoids of the cell;
• Life cycles - origin, growth and development and cell division

Sciences studying cellular level of organization:

Genetics and embryology study this level, but this is not the main object of study.


3. Tissue level of organization:

Includes 2 previous levels - molecular and cellular.

This level can be called multicellular"- because the fabric is collection of cells with a similar structure and performing the same functions.

Science - Histology

4. Organ(stress on the first syllable) level of organization of life

• In unicellular organs, these are organelles - there are common organelles - characteristic of all or prokaryotic cells, there are different ones.
• Cells in multicellular organisms general structure and functions are combined into tissues, and those, respectively, into bodies, which, in turn, are combined into systems and must interact harmoniously with each other.

Tissue and organ levels of organization - study the sciences:

5. Organism level

Includes all previous levels: molecular, cellular,tissue levels and organ.

At this level, Living Nature is divided into kingdoms — animals, plants, and fungi.

Characteristics of this level:


• Metabolism (both at the level of the organism and at the cellular level too)
• The structure (morphology) of the body
• Nutrition (metabolism and energy)
• homeostasis
• reproduction
• Interaction between organisms (competition, symbiosis, etc.)
• Interaction with the environment

Sciences:



6. Population-species level of life organization

Includes molecular, cellular,tissue levels, organ and body.

If several organisms are morphologically similar (in other words, have the same structure), and have the same genotype, then they form one species or population.

The main processes at this level are:


• The interaction of organisms with each other (competition or reproduction)
• microevolution (change of an organism under the influence of external conditions)