By the 1960s in biology there is an idea of ​​the levels organization of the living as a concrete expression of an increasingly complex orderlinessorganic world. Life on Earth is represented by organisms of a kindbuildings belonging to certain systematic groups (type), as well ascommunities of varying complexity (biogeocenosis, biosphere). In turn, organismscharacterized by organ, tissue, cellular and molecular organization.Each organism, on the one hand, consists of specialized subordinateorganization systems (organs, tissues, etc.), on the other hand, is itselfrelatively isolated unit in the composition of supraorganismal biologicalsystems (species, biogeocenoses and the biosphere as a whole). Levels of organization alivematter are presented in fig. one

Fig.1. Levels of organization of the living

On all of them, such properties of life as discreteness and integrity are manifested. The body is made up of various components- organs, but at the same time, thanks to their interaction, it is integral. The species is also an integral system, although it is formed by separate units - individuals, however, their interaction maintains the integrity of the species. The existence of life at all levels is provided by the structure of the lowest rank. For example, the nature of the cellular level of organization is determined by the subcellular and molecular levels; organismic - organ; tissue, cellular; specific - organismal, etc. It should be noted the great similarity of units of organization at the lower levels and the ever-increasing difference at the higher levels (Table 1).

Table 1

Characteristics of the levels of organization of the living

Life is a multi-level system (from the Greek. system- association, collection). There are such basic levels of organization of living things: molecular, cellular, organ-tissue, organism, population-species, ecosystem, biospheric. All levels are closely interconnected and arise one from the other, which indicates the integrity of living nature.

Molecular level of organization of living

This is unity chemical composition(biopolymers: proteins, carbohydrates, fats, nucleic acids), chemical reactions. From this level, the life processes of the organism begin: energy, plastic and other exchanges, change and implementation of genetic information.

Cellular level of organization of living

Cellular level of organization of the living. animal cell

The cell is the elementary structural unit of the living. This is the unit of development of all living organisms living on Earth. In each cell, the processes of metabolism, energy conversion take place, the preservation, transformation and transfer of genetic information is ensured.

Each cell consists of cellular structures, organelles that perform certain functions, so it is possible to isolate subcellular level.

Organ-tissue level of organization of living

Organ-tissue level of organization of the living. Epithelial tissues, connective tissues, muscle tissues and nerve cells

Cells of multicellular organisms that perform similar functions have the same structure, origin, and unite into tissues. There are several types of tissues that have differences in structure and perform different functions (tissue level).

Tissues in different combinations form different organs that have a certain structure and perform certain functions (organ level).

Organs are combined into organ systems (system level).

Organismal level of organization of living

Organismal level of organization of living

Tissues are combined into organs, organ systems and function as a single whole - the body. The elementary unit of this level is an individual, which is considered in development from the moment of birth to the end of existence as a single living system.

Population-species level of organization of living

Population-species level of organization of living

A set of organisms (individuals) of the same species, having a common habitat, forms populations. A population is an elementary unit of species and evolution, since elementary evolutionary processes take place in it, this and the following levels are supraorganismal.

Ecosystem level of organization of living

Ecosystem level of organization of living

Set of organisms different types and levels of organization forms this level. Here we can distinguish biocenotic and biogeocenotic levels.

Populations of different species interact with each other, form multispecies groups ( biocenotic level).

The interaction of biocenoses with climatic and other non-biological factors (relief, soil, salinity, etc.) leads to the formation of biogeocenoses (biogeocenotic). In biogeocenoses, there is a flow of energy between populations of different species and the circulation of substances between its inanimate and living parts.

Biospheric level of organization of living

Biospheric level of organization of living things. 1 - molecular; 2 - cellular; 3 - organism; 4 - population-species; 5 - biogeocenotic; 6 - biospheric

It is represented by a part of the shells of the Earth where life exists - the biosphere. The biosphere consists of a set of biogeocenoses, functions as a single integral system.

It is not always possible to select the entire set of levels listed. For example, in unicellular organisms, the cellular and organismal levels coincide, but the organ-tissue level is absent. Sometimes additional levels can be distinguished, for example, subcellular, tissue, organ, systemic.

All Live nature is a collection biological systems different levels organization and different subordination.
The level of organization of living matter is understood as the functional place that a given biological structure occupies in common system organization of nature.

The level of organization of living matter is a set of quantitative and qualitative parameters of a certain biological system (cell, organism, population, etc.), which determine the conditions and boundaries of its existence.

There are several levels of organization of living systems, which reflect subordination, hierarchy structural organization life.

• Molecular (molecular-genetic) level represented by individual biopolymers (DNA, RNA, proteins, lipids, carbohydrates and other compounds); at this level of life, phenomena associated with changes (mutations) and reproduction are studied genetic material, metabolism. This is the science of molecular biology.
• Cellularlevel- the level at which life exists in the form of a cell - the structural and functional unit of life, is studied by cytology. At this level, processes such as metabolism and energy, information exchange, reproduction, photosynthesis, transmission of nerve impulses, and many others are studied.

The cell is the structural unit of all living things.

• tissue level studying histology.

Tissue is a combination of intercellular substance and cells similar in structure, origin and functions.

• Organlevel. An organ contains several tissues.
• Organismiclevel- the independent existence of a single individual - a unicellular or multicellular organism is studied, for example, by physiology and autecology (ecology of individuals). An individual as an integral organism is an elementary unit of life. Life in nature does not exist in any other form.

An organism is a real carrier of life, characterized by all its properties.

• population-specieslevel- level, which is represented by a group of individuals of the same species - population; it is in the population that elementary evolutionary processes (accumulation, manifestation, and selection of mutations) take place. This level of organization is studied by such sciences as de-ecology (or population ecology), evolutionary doctrine.

A population is a collection of individuals of the same species that exist for a long time in a certain area, interbreed freely and are relatively isolated from other individuals of the same species.

• Biogeocenoticlevel- represented by communities (ecosystems) consisting of different populations and their habitats. This level of organization is studied by biocenology or synecology (community ecology).

Biogeocenosis is a combination of all species with varying complexity of organization and all factors of their habitat.

• biosphericlevel- level representing the totality of all biogeocenoses. In the biosphere, the circulation of substances and the transformation of energy with the participation of organisms take place.

2. Nucleic acids (DNA and RNA) and proteins attract attention as the substrate of life. Nucleic acids are complex chemical compounds containing carbon, oxygen, hydrogen, nitrogen and phosphorus. DNA is the genetic material of cells and determines the chemical specificity of genes. Under the control of DNA, protein synthesis takes place, in which RNA participates. 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-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 non-organic organic matter.

They are sometimes called biological macromolecular substances. At the molecular level, various life processes of living organisms take place: metabolism, energy conversion. By using molecular level the transfer of hereditary information is carried out, separate organelles are formed and other processes occur.

Cellular level.

The cell is the structural and functional unit of all living organisms on Earth. Individual organelles in the cell have a characteristic structure and perform a specific function. The functions of individual organelles in the cell are interconnected and perform common life processes.

In unicellular 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 protozoa - amoeba, infusoria, 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 set of cells and intercellular substances similar in origin, structure and functions forms a tissue. The tissue level is typical only for multicellular organisms. Also, individual tissues are not an independent holistic organism. For example, the bodies of animals and humans are made up of four different tissues (epithelial, connective, muscle, and nervous). Plant tissues are called: educational, integumentary, supporting, conductive and excretory. Recall the structure and functions of individual tissues.

Organ level.

In multicellular organisms, the union of several identical tissues, similar in structure, origin and functions, 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, unite to form an organ system, for example, digestion, respiration, blood circulation, etc.

Organism level.

Plants (chlamydomonas, chlorella) and animals (amoeba, infusoria, etc.), whose bodies consist of one cell, are an independent organism. A separate individual of multicellular organisms is considered as a separate organism. In each individual organism, all the vital processes characteristic of all living organisms take place - 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 specialized in performing 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 ontogeny. An organism can exist in close relationship with the environment.

Population-species level.

An aggregate of individuals of one species or a group that exists for a long time in a certain part of the range relatively apart from other aggregates of the same species constitutes a population. At the population level, the simplest evolutionary transformations are carried out, which contributes to the gradual emergence of a new species.

Biogeocenotic level.

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

biospheric level.

The totality of all living organisms on our planet and their common natural habitat constitutes the biospheric level. At the biospheric level, modern biology decides global problems, for example, determining the intensity of the formation of free oxygen by the Earth's vegetation cover or changes in the concentration of carbon dioxide in the atmosphere associated with human activities.

In particular, the properties of living things can be called:

1. Self-renewal, which is associated with a constant exchange of matter and energy, and which is based on the ability to store and use biological information in the form of unique information molecules: proteins and nucleic acids.

2. Self-reproduction, which ensures continuity between generations of biological systems.

3. Self-regulation, which is based on the flow of matter, energy and information.

4. Most chemical processes in the body are not in a dynamic state.

5. Living organisms are capable of growth.

permanent, who are all life cycle spend in the host organism, using it as a source of nutrition and habitat (for example, ascaris, tapeworms, lice);

a) intracavitary - localized in cavities connected to the external environment (for example, in the intestine - ascaris, whipworm);

b) tissue localized in tissues and closed cavities; (eg, liver fluke, tapeworm cysticerci);

in) intracellular- localized in cells; (e.g. malarial plasmodia, toxoplasma).

additional, or second intermediate hosts (eg, fish for the cat's fluke);

1) Alimentary(through the mouth with food) - helminth eggs, protozoan cysts in case of non-compliance with the rules of personal hygiene and food hygiene (vegetables, fruits); larvae of helminths (trichinella) and vegetative forms of protozoa (toxoplasma) with insufficient culinary processing of meat products.

2) Airborne(through mucous membranes respiratory tract) - viruses (influenza) and bacteria (diphtheria, plague) and some protozoa (toxoplasma).

3) Contact household(direct contact with a sick person or animal, through linen and household items) - eggs of contact helminths (pinworm, dwarf tapeworm) and many arthropods (lice, scabies).

4) Transmissible- with the participation of the carrier - arthropod:

a) inoculation - through the proboscis when sucking blood (malarial plasmodia, trypanosomes);

b) contamination- when combing and rubbing excrement or carrier hemolymph into the skin (lousy typhus, plague).

Transplacental(through the placenta) - toxoplasma, malarial plasmodia.

Sexual(during sexual intercourse) - AIDS virus, Trichomonas.

Transfusion(during blood transfusion) - AIDS virus, malarial plasmodia, trypanosomes.

a) highly adapted(contradictions in the system practically do not appear);

The following forms of manifestation of specificity are distinguished:

topical: certain localization in the host (head and body lice, scabies mite, intestinal helminths);

age(pinworms and dwarf tapeworm more often affect children);

seasonal(outbreaks of amoebic dysentery are associated with the spring-summer period, trichinosis - with the autumn-winter period).

The world of wildlife is a collection of biological systems of 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 substances. From this level, the most important processes of the organism's life activity begin: metabolism and energy conversion, transmission of hereditary information, etc. - 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 commonplace habitation, creates a population as a system of supra-organismal order. In this system, the simplest, elementary evolutionary transformations are carried out.

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

biospheric- the biosphere - the most high level 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 during 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 of them dies and resolves, 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.

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