The following levels of life organization are distinguished: molecular, cellular, organ-tissue (sometimes they are separated), organismal, population-species, biogeocenotic, biosphere. 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 higher ones.

So complex organic molecules are part of cells and determine their structure and vital functions. 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 a biological species. A community is represented by interacting populations different types. The community and environment form a biogeocenosis (ecosystem). The totality of planet Earth's ecosystems forms its biosphere.

At each level, new properties of living things arise that are absent at the underlying level, and their own elementary phenomena and elementary units are distinguished. At the same time, in many ways the levels reflect the progress evolutionary process.

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

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

Molecular level

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

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

Cellular level of life

It is the cell that is the structural and functional unit of living things. There is no life outside the cell. Even viruses can exhibit the properties of a living thing only when they are in the host cell. Biopolymers fully demonstrate their reactivity when organized into a cell, which can be considered as complex system interconnected primarily 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 coupled.

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 having the same genetic information. At this level, cell specialization occurs.

In plants and animals they secrete different types fabrics. So in plants it is a meristem, protective, basic and conductive tissue. In animals - epithelial, connective, muscular and nervous. Tissues may include a list of subtissues.

An organ usually consists of several tissues interconnected into 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.

Organismic level of organization of living things

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

Multicellular organisms are made up of organ systems.

At the organismal level, such life phenomena as reproduction, ontogenesis, metabolism, irritability, neurohumoral regulation, and homeostasis are manifested. In other words, its elementary phenomena constitute the natural changes of 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 have a common gene pool. Within a species, they can exchange genes, i.e. they are genetically open systems.

Elementary evolutionary phenomena occur in populations, ultimately leading to speciation. Living nature can evolve only at supraorganism levels.

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

Biogeocenotic level

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

The role of the biogeocenotic level is the formation of stable communities of organisms of different species adapted to cohabitation in a certain habitat.

Biosphere

The biosphere level of life organization is a system of the highest order of life on Earth. The biosphere covers all manifestations of life on the planet. At this level, there is a global circulation of substances and a flow of energy (encompassing all biogeocenoses).

All life on Earth is ordered and has a complex hierarchy from simple to complex - levels of organization of living nature.

Levels

The structure of living matter begins with a molecule - the smallest particle of matter consisting of atoms. The molecule belongs to inanimate nature and is studied by physics and chemistry. By interacting, molecules form substances from which tissues, organs and organisms as a whole are built. Detailed description presented in the table of levels of organization of living nature.

Level	System elements	Processes
Molecular (molecular genetic)	Atoms, molecules of organic and inorganic compounds, biopolymers - DNA, RNA, proteins, lipids, carbohydrates	Metabolism and energy conversion, transmission of genetic information
Cellular	Cell organelles, complexes of chemical compounds	Synthesis of organic compounds, transport chemical substances, division
Fabric	Specific cells, intercellular substance	Metabolism, growth, irritability, sensitivity, conductivity, etc.
Organ	Various types of tissues that form organs	The functioning of organs depending on their purpose: movement, gas exchange, excitability, digestion, etc.
Organismal (ontogenetic)	Organ systems that form a multicellular organism - a separate functional structure of animal or plant origin	Harmonious functioning of all organs
Population-species	Groups of related individuals united in a population. They carry a single gene pool, are distinguished by the same morphological and behavioral characteristics, and occupy a specific area	Organization of communities, interactions between individuals, adaptation to changing conditions, accumulation of genetic information, evolution
Biogeocenotic	Different populations, environmental factors	Relationship between populations and environment
Biosphere	Biogeocenosis, human activity (noosphere)	The interaction of living and nonliving matter, the cycle of substances in nature, human impact on the biosphere

Rice. 1. Levels of organization.

Each level of organization has its own patterns. To study a separate level, specialized areas of biology have been identified. For example, the initial level is studied by molecular biology and biochemistry, cells are studied by cytology, tissues by histology, populations and their interaction with the environment by ecology.

Unicellular and multicellular

All organisms according to their structure are divided into two types:

• unicellular - consist of one cell;
• multicellular - consist of many interconnected cells.

Unicellular organisms are limited by a membrane, under which there is cytoplasm with organelles - the functional particles of cells. Unicellular organisms are similar in structure and function to the cells of multicellular organisms. However, they can move independently and lead a free lifestyle.

Representatives of unicellular organisms:

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• plants (eukaryotes) - chlamydomonas, chlorella, green euglena;
• animals (eukaryotes) - amoeba, ciliates;
• bacteria (prokaryotes) - Escherichia coli, cocci.

Rice. 2. Single-celled organisms.

Multicellular organisms are more complexly organized. The most primitive are sponges, the most complex are mammals.

Rice. 3. Multicellular organisms.

Unlike unicellular organisms, multicellular organisms have more levels of organization. However, regardless of the complexity of the structure, all organisms interact with the environment at the biogeocenotic and biosphere levels.

Properties of organisms

All representatives of the biosphere (unicellular and multicellular) are united properties of living organisms:

• reproduction;
• metabolism;
• energy dependence;
• height;
• development;
• self-regulation;
• irritability;
• heredity;
• variability.

In addition, living organisms have a single chemical composition. The main elements of living matter are nitrogen, oxygen, carbon, hydrogen. Proteins, fats, and carbohydrates are formed from them.

What have we learned?

From the 9th grade biology lesson we learned about the basic levels of living nature. Topic included short description the hierarchy of living nature, the characteristics of multicellular and unicellular organisms, as well as the properties of the organisms that make up the biosphere.

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Basic properties of living organisms. Questions about the origin of life and the patterns of historical development in various geological eras have always interested humanity. The concept of life covers the totality of all living organisms on Earth and the conditions of their existence.
The essence of life is that living organisms leave behind offspring. Hereditary information is passed on from generation to generation, organisms self-regulate and recover during the reproduction of offspring. Life is a special high-quality, highest form of matter, capable of self-reproduction, leaving offspring.
The concept of life was given different definitions in different historical periods. The first scientifically correct definition was given by F. Engels: “Life is a way of existence of protein bodies, and this way of existence consists essentially in the constant self-renewal of chemical components these bodies." When the process of metabolism between living organisms and the environment ceases, proteins disintegrate and life disappears. Based on modern achievements of biological science, the Russian scientist M.V. Volkenshtein gave a new definition to the concept of life: "Living bodies existing on Earth, are open, self-regulating and self-reproducing systems built from biopolymers - proteins and nucleic acids." This definition does not deny the presence of life on other planets in outer space. Life is called an open system, as indicated by continuous process exchange of substances and energy with the environment.
Based on the latest scientific achievements of modern biological science, the following definition of life has been given: “Life is an open, self-regulating and self-reproducing system of aggregates of living organisms, built from complex biological polymers - proteins and nucleic acids.”
Nucleic acids and proteins are considered the basis of all living things, since they function in the cell and form complex compounds that are part of the structure of all living organisms.
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Basic properties of living organisms

Living organisms differ from inanimate nature by their inherent properties. The characteristic properties of living organisms include: unity chemical composition, metabolism and energy, similarity of levels of organization. Living organisms are also characterized by reproduction, heredity, variability, growth and development, irritability, discreteness, self-regulation, rhythm, etc.

Levels of life organization

All living organisms in nature consist of the same levels of organization; this is a characteristic biological pattern common to all living organisms. The following levels of organization of living organisms are distinguished: molecular, cellular, tissue, organ, organismal, population-species, biogeocenotic, biosphere.
1. Molecular genetic level. This is the most elementary level characteristic of life. No matter how complex or simple the structure of any living organism, they all consist of the same molecular compounds. An example of this are nucleic acids, proteins, carbohydrates and other complex molecular complexes of organic and inorganic substances. They are sometimes called biological macromolecular substances. At the molecular level, various life processes of living organisms occur: metabolism, energy conversion. With the help of the molecular level, the transfer of hereditary information is carried out, individual organelles are formed and other processes occur.
2. Cellular level. The cell is the structural and functional unit of all living organisms on Earth. Individual organelles within a cell have a characteristic structure and perform a specific function. The functions of individual organelles in a cell are interconnected and perform common vital processes. In single-celled organisms (unicellular algae and protozoa), all life processes take place in one cell, and one cell exists as a separate organism. Remember unicellular algae, chlamydomonas, chlorella and the simplest animals - amoeba, ciliates, etc. In multicellular organisms, one cell cannot exist as a separate organism, but it is an elementary structural unit of the organism.

Tissue level

A collection of cells and intercellular substances similar in origin, structure and function forms tissue. The tissue level is characteristic only of multicellular organisms. Also, individual tissues are not an independent integral organism. For example, the bodies of animals and humans consist of four different tissues (epithelial, connective, muscle, nervous). Plant tissues are called: educational, integumentary, supporting, conductive and excretory. Remember the structure and functions of individual tissues.

Organ level

In multicellular organisms, the combination of several identical tissues, similar in structure, origin and function, forms the organ level. Each organ contains several tissues, but among them one is the most significant. A separate organ cannot exist as a whole organism. Several organs, similar in structure and function, combine to form an organ system, for example, digestion, respiration, blood circulation, etc.

Organismal level

Plants (Chlamydomonas, Chlorella) and animals (amoeba, ciliates, etc.), whose bodies consist of one cell, represent an independent organism) And an individual individual of multicellular organisms is considered as a separate organism. In each individual organism, all life processes characteristic of all living organisms occur - nutrition, respiration, metabolism, irritability, reproduction, etc. Each independent organism leaves behind offspring. In multicellular organisms, cells, tissues, organs, and organ systems are not a separate organism. Only an integral system of organs that specifically perform various functions forms a separate independent organism. The development of an organism, from fertilization to the end of life, takes a certain period of time. This individual development of each organism is called ontogenesis. An organism can exist in close relationship with its environment.

Population-species level

A collection of individuals of one species or group that exists for a long time in a certain part of the range, relatively separately from other populations of the same species, constitutes a population. At the population level, simple evolutionary transformations are carried out, which contributes to the gradual emergence of a new species.

Biogeocenotic level

A set of organisms of different species and varying complexity of organization, adapted to the same conditions natural environment, is called biogeocenosis, or natural community. The biogeocenosis includes numerous species of living organisms and natural environmental conditions. In natural biogeocenoses, energy accumulates and is transferred from one organism to another. Biogeocenosis includes inorganic, organic compounds and living organisms.

Biosphere level

The totality of all living organisms on our planet and their common natural habitat constitutes the biosphere level. At the biosphere level, modern biology decides global problems, for example, determining the intensity of formation of free oxygen by the Earth's vegetation or changes in the concentration of carbon dioxide in the atmosphere associated with human activity. The main role at the biosphere level is played by “living substances,” that is, the totality of living organisms inhabiting the Earth. Also at the biosphere level, “bio-inert substances” are important, formed as a result of the vital activity of living organisms and “inert” substances (i.e., environmental conditions. At the biosphere level, the circulation of substances and energy occurs on Earth with the participation of all living organisms of the biosphere.

Levels of life organization

Levels of organization of the organic world are discrete states of biological systems, characterized by subordination, interconnectedness, and specific patterns.

The structural levels of the organization of life are extremely diverse, but the main ones are molecular, cellular, ontogenetic, population-species, bigiocenotic and biosphere.

1. Molecular genetic level life. The most important tasks of biology at this stage are the study of the mechanisms of transmission of genetic information, heredity and variability.

There are several mechanisms of variability at the molecular level. The most important of them is the mechanism of gene mutation - the direct transformation of the genes themselves under the influence external factors. Factors causing mutation are: radiation, toxic chemical compounds, viruses.

Another mechanism of variability is gene recombination. This process occurs during sexual reproduction in higher organisms. In this case, there is no change in the total amount of genetic information.

Another mechanism of variability was discovered only in the 1950s. This is a non-classical recombination of genes, in which there is a general increase in the volume of genetic information due to the inclusion of new genetic elements in the cell's genome. Most often, these elements are introduced into the cell by viruses.

2. Cellular level. Today, science has reliably established that the smallest independent unit of structure, functioning and development of a living organism is the cell, which is an elementary biological system capable of self-renewal, self-reproduction and development. Cytology is a science that studies a living cell, its structure, functioning as an elementary living system, studies the functions of individual cellular components, the process of cell reproduction, adaptation to environmental conditions, etc. Cytology also studies the characteristics of specialized cells, the formation of their special functions and the development of specific cellular structures . Thus, modern cytology was called cell physiology.

Significant advances in the study of cells occurred at the beginning of the 19th century, with the discovery and description of the cell nucleus. Based on these studies, the cell theory was created, which became the greatest event in biology of the 19th century. It was this theory that served as the foundation for the development of embryology, physiology, and the theory of evolution.

The most important part of all cells is the nucleus, which stores and reproduces genetic information and regulates metabolic processes in the cell.

All cells are divided into two groups:

Prokaryotes are cells without a nucleus

Eukaryotes - cells containing nuclei

Studying a living cell, scientists drew attention to the existence of two main types of its nutrition, which made it possible to divide all organisms into two types:

Autotrophic - they produce what they need on their own. nutrients

· Heterotrophic - cannot do without organic food.

Later the following were clarified important factors, as the ability of organisms to synthesize necessary substances (vitamins, hormones), provide themselves with energy, dependence on ecological environment etc. Thus, the complex and differentiated nature of the connections indicates the need for a systematic approach to the study of life at the ontogenetic level.

3. Ontogenetic level. Multicellular organisms. This level arose as a result of the formation of living organisms. The basic unit of life is the individual, and the elementary phenomenon is ontogenesis. Physiology studies the functioning and development of multicellular living organisms. This science examines the mechanisms of action of various functions of a living organism, their relationship with each other, regulation and adaptation to the external environment, origin and formation in the process of evolution and individual development of the individual. In essence, this is the process of ontogenesis - the development of the organism from birth to death. At the same time, growth, movement of individual structures, differentiation and complication of the organism occur.

All multicellular organisms are composed of organs and tissues. Tissues are a group of physically united cells and intercellular substances to perform specific functions. Their study is the subject of histology.

Organs are relatively large functional units that unite various tissues into certain physiological complexes. In turn, organs are part of larger units - body systems. Among them are the nervous, digestive, cardiovascular, respiratory and other systems. Only animals have internal organs.

4. Population-biocenotic level. This is a supraorganismal level of life, the basic unit of which is the population. In contrast to a population, a species is a collection of individuals that are similar in structure and physiological properties, have a common origin, and can freely interbreed and produce fertile offspring. A species exists only through populations representing genetically open systems. Population biology is the study of populations.

The term “population” was introduced by one of the founders of genetics, V. Johansen, who gave this name to a genetically heterogeneous collection of organisms. Later, the population began to be considered an integral system that continuously interacts with the environment. Populations are the real systems through which species of living organisms exist.

Populations are genetically open systems, since the isolation of populations is not absolute and periodically it is not possible to exchange genetic information. It is populations that act as elementary units of evolution; changes in their gene pool lead to the emergence of new species.

Populations capable of independent existence and transformation are united in the aggregate of the next supraorganism level - biocenoses. Biocenosis is a set of populations living in a certain territory.

A biocenosis is a system closed to foreign populations; for its constituent populations it is an open system.

5. Biogeocetonic level. Biogeocenosis - sustainable system, which can exist for a long time. Equilibrium in a living system is dynamic, i.e. represents a constant movement around a certain point of stability. For its stable functioning, it is necessary to have feedback connections between its control and execution subsystems. This way of maintaining a dynamic balance between various elements biogeocenosis, caused by the mass reproduction of some species and the reduction or disappearance of others, leading to a change in the quality of the environment, is called an environmental disaster.

Biogeocenosis is an integral self-regulating system in which several types of subsystems are distinguished. Primary systems are producers that directly process nonliving matter; consumers - the secondary level at which matter and energy are obtained through the use of producers; then come second-order consumers. There are also scavengers and decomposers.

The cycle of substances passes through these levels in the biogeocenosis: life participates in the use, processing and restoration of various structures. In biogeocenosis there is a unidirectional energy flow. This makes it an open system, continuously connected with neighboring biogeocenoses.

Self-regulation of biogeocenls is more successful the more diverse the number of its constituent elements is. The stability of biogeocenoses also depends on the diversity of its components. The loss of one or more components can lead to an irreversible imbalance and the death of it as an integral system.

6. Biosphere level. This highest level organization of life, covering all phenomena of life on our planet. The biosphere is the living matter of the planet and the environment transformed by it. Biological metabolism is a factor that unites all other levels of life organization into one biosphere. At this level, the circulation of substances and the transformation of energy occur, associated with the vital activity of all living organisms living on Earth. Thus, the biosphere is a single ecological system. Studying the functioning of this system, its structure and functions is the most important task of biology at this level of life. Ecology, biocenology and biogeochemistry study these problems.

The development of the doctrine of the biosphere is inextricably linked with the name of the outstanding Russian scientist V.I. Vernadsky. It was he who managed to prove the connection between the organic world of our planet, acting as a single indivisible whole, and geological processes on Earth. Vernadsky discovered and studied the biogeochemical functions of living matter.

1.2. Levels of organization of a living system

The human body is a complex self-regulating system of interconnected structural elements, united
at several levels of the organization. The following levels are distinguished: to pit, tissue, organ, systemic and organismal.
Between themselves, these levels of organization are in hierarchical (subordinate) relationships.

1. Cellular level. A cell is a structural and functional unit of a living organism. She happens to be biological system and is characterized by metabolism, growth, development and reproduction.

2. Tissue level. A collection of cells that have a common origin, similar structure and perform the same functions forms tissue. There are four main types of fabric:
epithelial, connective, muscular and nervous. Each fabric has specific features structures and performs certain functions.

· Epithelial tissues are border tissues covering the outside of organs and lining the cavities of internal organs from the inside and forming glands of external and internal secretion. These tissues perform protective, absorption (intestinal epithelium), and secretory functions.

· Connecting fabrics, including several varieties: connective tissue itself(fibrous,
tissues with special properties - adipose, reticular, mucous and pigment tissue), skeletal tissues(cartilage, bone). Connective tissues also include blood and lymph (liquid connective tissue). The main functions of connective tissue types are supporting, trophic (nutritive), protective, maintaining the constancy of the internal environment of the body (homeostasis).

· Musculartissues (striated skeletal, striated cardiac and smooth muscle) provide muscle contraction and human motor reactions: movement of the body or its individual parts in space, rhythmic activity of the myocardium, movement of blood through the vessels (hemocirculation), food through the digestive tract, etc.

· Nervous fabric provides perception irritations
from the external and internal environment of the body, carrying out nerve impulses into the central nervous system (CNS), where in its higher parts the analysis and synthesis of the received information occurs, and implementation quick response adaptive reactions. The nervous system regulates the activities of individual organs and the body as a whole.

WITH The layers of tissue that cover, line and separate internal organs are called meninges. In the human body, the following main types of membranes are distinguished:

1. Mucous membranes usually line the inner surface of hollow organs. They include three layers of tissue: epithelial (with secretory cells that secrete mucus), loose connective tissue with glands and lymphoid formations, and smooth muscle.

2. Synovial membranes cover the surfaces of joints and tendons. They are formed by connective tissue and lined with endothelium.

3. Serous membranes surround outer surface all internal organs. They are formed by a connective tissue membrane covered with an epithelial layer.

4. Meninges (dura, arachnoid, soft) cover the brain and spinal cord. They are formed by connective tissue.

3. Organ level. Several tissues, uniting into a single complex, form an organ, but one of the tissues predominates in it and determines its main function. Organs occupy a certain position in the body, have a certain structure and shape, and perform a certain function necessary for the existence of a complete organism.

4. System level. Several organs that jointly perform a specific function form physiological system (cardiovascular, respiratory, digestive, nervous
and other systems). Among all the physiological systems of the body, it occupies a special place nervous system, because it regulates and coordinates the activities of all systems, ensures the body’s adaptation to changing environmental conditions.

5. Organismic level. A living organism, consisting of individual cells, tissues, organs, systems, is a single whole (“system of systems” according to I. P. Pavlov), in which the activity of all these structures is strictly coordinated, subordinated to a single whole and ensures normal life activity
in a constantly changing external environment.

Organ systems in the body do not function in isolation from each other, but at a certain period they combine with each other to achieve beneficial to the body result. Such a temporary association of organs and systems belonging to different physiological systems, P. K. Anokhin (academician, neurophysiologist)
named functional system.

It is typical for the living nature of our planet complex, hierarchical relationship between levels of organization. All organic world and the environment forms the biosphere, which, in turn, consists of biogeocenoses (ecosystems) - territories with characteristic natural conditions and certain plant and animal complexes (biocenoses). Biocenoses are formed by populations - groups of plant and animal organisms of the same species, living in a certain territory and capable of producing. Populations consist of representatives of specific species (individuals) capable of interbreeding freely and producing fertile offspring. Multicellular organisms consist of organs and tissues formed by cells. Single-celled organisms and cells are formed by intracellular structures that consist of molecules.

Based on this, we distinguish several levels of organization of living matter.

Each level of organization of living organisms is characterized by its own patterns associated with its specific principles of organization and features of relationships with other levels.

General biology studies the basic patterns of life phenomena that occur on various levels living organizations. Consideration of the organization of living matter begins with elucidation of the structure and properties of complex organic molecules. The cells of multicellular organisms are part of tissues; two or more tissues form an organ. A multicellular organism has a complex structure, which consists of tissues and organs, and at the same time is an elementary unit of a biological species. By interacting with each other, species form a community, or ecological system, which, in turn, is one of the components of the biosphere.

Each level of organization of organisms is studied by the corresponding branches of biology.

Molecular level

Note 1

Any living system, no matter how complexly it is organized, is determined at the level of functioning of biological macromolecules - biopolymers: nucleic acids, proteins, polysaccharides, as well as other important organic substances. From this level, the most important life processes of the body begin: metabolism and energy conversion, transmission of hereditary information, etc.

Molecular biology, molecular genetics, physiology, cytochemistry, biochemistry, biophysics, certain branches of virology, microbiology study the physicochemical processes occurring in a living organism (synthesis, decomposition and mutual transformations of proteins, nucleic acids, polysaccharides, lipids and other substances in the cell; metabolism, energy and information that regulate these processes).

Such studies of living systems have shown that they consist of low- and high-molecular organic compounds, which are almost impossible to detect in inanimate nature. The most characteristic biopolymers for living organisms are proteins, nucleic acids, polysaccharides, lipids (fat-like compounds) and their constituent molecules (amino acids, nucleotides, monosaccharides, fatty acids). Also, at this level, the synthesis, breakdown and mutual transformations of these compounds in cells, metabolism, energy and information, and the regulation of these processes are studied.

As a result of such studies, it was found that most important feature main metabolic pathways - the action of biological catalysts - enzymes(compounds of protein nature), which strictly selectively affect the speed chemical reactions. The structure of some amino acids, a number of proteins and many simple organic compounds has also been studied. It has been established that chemical energy, which is released during biological oxidation (respiration processes, glycolysis), is stored in the form of energy-rich compounds (mainly adenosine phosphoric acids ATP, ADP, etc.), and then used in processes that require energy input (muscle contractions, synthesis and transport of substances). A major success was the opening genetic code. It was found that heredity encoded in DNA through enzyme proteins controls both structural proteins and all the basic properties of cells and the organism as a whole.

Research at the molecular level requires isolating and studying all types of molecules that make up the cell and revealing their relationships with each other.

Research methods used at the molecular level:

• electrophoresis (to separate macromolecules using their differences in charges);
• ultracentrifugation (to separate macromolecules using their differences in density and size);
• chromatography (to separate macromolecules using their differences in adsorption properties);
• X-ray diffraction analysis (study the relative spatial arrangement of atoms in complex molecules);
• radioisotopes (study of pathways of transformation of substances, the rate of their synthesis and decay);
• artificial modeling of systems from isolated cellular elements (reproduction of processes occurring in a cell - all biochemical processes in a cell occur not in a homogeneous mixture of substances, but on certain cellular structures).

Cellular level

At the cellular level cytology, histology, and their departments (karyology, cyto- and histochemistry, cytophysiology, cytogenetics), many sections of physiology, microbiology and virology study the structure of the cell and internal cellular components, as well as connections and relationships between cells in the tissues and organs of the body. There are no free-living non-cellular life forms.

Cell- the main independent functional and structural unit of a multicellular organism. There are single-celled organisms (algae, fungi, protozoa, bacteria). Also, the cell is the unit of development of all living organisms that exist on Earth. The properties of a cell are determined by its components, which perform various functions.

Thanks to research at the cellular level, the main components of the cell, the structure of cells and tissues, and their changes during development have been studied.

Research methods at the cellular level:

• microscopy (light microscope allows you to see objects down to 1 micron);
• color histochemical reactions (detection of the localization of various chemicals and enzymes in the cell);
• autoradiography (detection of sites of macromolecule synthesis in the cell);
• electron microscopy (distinguishing structures down to macromolecules, although describing their structure is often difficult due to insufficient image contrast);
• centrifugation (study of the functions of intracellular components - they are isolated from destroyed (homogenized) cells);
• tissue culture (study of cell properties);
• microsurgery (exchange of nuclei between cells, fusion (hybridization) of cells.

Tissue level

Tissue is a collection of cells similar in structure, united by the performance of a common function. Hundreds of different cells make up the body of a variety of multicellular organisms. A variety of animal cells form four types of tissue: nervous, connective, epithelial and muscle. Plants are divided into formative and permanent tissues. Permanent tissues include integumentary, conductive, mechanical and ground tissue.

Organ level

Definition 2

Organs- these are highly differentiated parts of the body that are located in a specific place and perform special functions. It's structural - functional associations several types of fabrics. They are formed during development from cells of various tissues.

Groups of different organs function collectively to perform a common function for the body. A person has the following organ systems: digestive, respiratory, cardiovascular, nervous, secretory, excretory, reproductive, endocrine, muscular, skeletal and integumentary tissue system. Each individual organ of the system performs a specific function, but they all work together as one “team”, providing maximum efficiency the entire system. All organ systems function in interconnection and are regulated by the nervous and endocrine systems. Impaired functioning of any organ leads to pathology of the entire system and even the body.

Organismal level

Physiology (plants and animals, higher nervous activity), experimental morphology, endocrinology, embryology, immunology, as well as a number of other biological branches study the processes and phenomena occurring in an individual, and the coordinated functioning of its organs and systems.

At this level to create general theory Ontogenesis, research is carried out aimed at revealing the causal mechanisms of the formation of a biological organization, its differentiation and integration, and the implementation of genetic information in ontogenesis. The mechanisms of operation of organs and their systems, their role in the life of the body, mutual influences of organs, nervous and humoral regulation of their functions, animal behavior, adaptive changes, etc. are also studied.

At this level, the mechanism of operation of organs and systems, their role in the life of the body, the relationships of organs, the behavior of organisms, and adaptive changes are also studied.

Currently used research methods:

• electrophysiological(consist of abduction, amplification and registration of bioelectric potentials);
• biochemical(endocrine regulation is being studied - the isolation and purification of hormones, the synthesis of their analogues, the study of the biosynthesis and mechanisms of action of hormones);
• cybernetic(research of the GNI of animals and humans using the modeling method);
• experimental(production conditioned reflexes, setting goals).

Population-species level

Definition 3

Certain branches of biology (morphology, physiology, genetics, ecology) study the elementary unit of the evolutionary process - population- a collection of individuals of the same species inhabiting a certain territory, more or less isolated from neighboring groups.

The study of population composition and dynamics is inextricably linked to the molecular, cellular and organismal levels.

Research methods are the methods of those sciences that study questions specifically posed at this level:

• genetic methods - the nature of the distribution of hereditary characteristics in populations;
• morphological
• physiological
• environmental.

A population and a species as a whole can serve as objects of study in a wide variety of biological branches.

Biogeocenotic, or biosphere, level

Definition 4

Biogeocenology, ecology, biogeochemistry and other branches of biology study the processes occurring in biogeocenoses(ecosystems) - elementary structural and functional units biosphere.

At this level, comprehensive studies are carried out, covering the relationships between biotic and abiotic components that are part of the biogeocenosis; the movement of living matter in the biosphere, the paths and patterns of energy circulation are studied. This approach makes it possible to foresee the consequences economic activity people and, in the form of the international program “Man and the Biosphere,” to coordinate the efforts of biologists from many countries.

Of great practical importance is the study of the biological productivity of biogeocenoses (utilization of solar radiation energy through photosynthesis and the use of energy stored by autotrophs by heterotrophic organisms).

Note 2

The need for a detailed study of the biosphere level of organization of living things is determined by the fact that biogeocenoses are the environment in which any life processes on our planet take place.

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