Until the middle of the twentieth century. The organic world was divided only into two kingdoms - plants and animals. Only with the development of electron microscopy and molecular biology in the middle of the twentieth century. a fundamental restructuring of the entire system of higher taxa began. It was fundamentally important to establish the fact of a sharp difference between bacteria, cyanobacteria (blue-green algae) and recently discovered archaebacteria from all other living beings.

They do not have a true nucleus, and the genetic material in the form of a circular DNA chain lies freely in the nucleoplasm and does not form true chromosomes. They are also distinguished by the absence of a mitotic spindle (non-mitotic division), microtubules, mitochondria, and centrioles. These organisms are called prenuclear, or prokaryotes. All other organisms (unicellular and multicellular) have a true nucleus surrounded by a membrane. The genetic material of the nucleus is enclosed in chromosomes containing DNA, RNA and proteins, there are usually various forms of mitosis, as well as ordered microtubules, mitochondria and plastids. Such organisms are called nuclear, or eukaryotes. The differences between prokaryotes and eukaryotes are so significant that in the system of organisms they are distinguished into superkingdoms.

According to modern views, evolutionarily, prokaryotes, along with the ancestors of eukaryotes - urkaryotes, belong to the most ancient organisms. The superkingdom of prokaryotes consists of two kingdoms - bacteria (including cyanobacteria) and archaebacteria. The situation is more complicated with the much more diverse superkingdom of eukaryotes. It consists of three kingdoms - animals, fungi and plants. The animal kingdom includes sub-kingdoms of protozoa and multicellular animals. The scope of the subkingdom of protozoa is highly controversial; many zoologists also include in it some of the nucleated algae and lower fungi. The simplest are single-celled eukaryotic organisms that are microscopic in size. The simplest do not have a single structural plan and are generally characterized by great differences, not unity. According to various sources, their number varies from 40 to 70 thousand species, the fauna of protozoa has not been studied enough.

The International Committee on the Systematics of Protozoa identified (1980) seven types of these organisms, and this classification is generally accepted. The subkingdom of multicellular animals includes organisms of a diverse structure - lamellar, sponges, coelenterates, worms, chordates, etc. However, all of them are characterized by the division of functions between different groups of cells.

Plants are the kingdom of autotrophic organisms, which are characterized by the ability to photosynthesis and the presence of dense cell membranes, usually consisting of cellulose; starch serves as a reserve substance.

The kingdom of fungi includes organisms called lower eukaryotes. The peculiarity of fungi is determined by a combination of signs of both plants (immobility, unlimited apical growth, the ability to synthesize vitamins, the presence of cell walls) and animals (heterotrophic type of nutrition, the presence of chitin in cell walls, storage carbohydrates in the form of glycogen, urea formation, the structure of cytochromes) .

The great similarity in the structure of eukaryotic cells can be explained by the fact that they descended from a common ancestor, which had all the main features of nuclear organisms. Who was this ancestor: an autotrophic organism, i.e. a plant, or a heterotrophic organism, i.e. an animal? The opinions of scientists differ. Some believe that the first nuclear organisms were plants, from which fungi and animals originated. Others believe that the first nuclear organisms were animals descended from pre-nuclear heterotrophs and then gave rise to fungi and plants.

It should be noted that the supporters of both hypotheses recognize the direct relationship between the plant and animal kingdoms. This means that at first the differences between plants and animals were small, and in the course of further evolution they increased more and more. The reason for the gradual divergence in the process of evolution of animals and plants lies in the main difference between them, namely, in the nature of metabolism: the former are heterotrophs, the latter are autotrophs. Inorganic compounds that feed on plants are scattered in the immediate vicinity of them (in water, soil, atmosphere). Therefore, plants can feed while leading a relatively immobile lifestyle. Animals, on the other hand, can synthesize organic substances only from organic substances contained in the bodies of other organisms, which determines their mobility.

Other important features of animals include active metabolism and, in connection with this, limited body growth, as well as the development in the process of evolution of various functional organ systems: muscular, digestive, respiratory, nervous systems and sensory organs. Animal cells, unlike plants, do not have a hard (cellulose) membrane.

However, the boundaries between the three kingdoms of eukaryotes are a matter of controversy, and only future research can bring clarity to this issue.

Therefore, a generally accepted system of organisms has not been created, and therefore the number of types (departments) is not the same for different authors. For example, R. Zitteker in 1969 proposed to single out the fourth kingdom of eukaryotes - the kingdom of protists, where he attributed the protozoa, euglena, golden algae, pyrophytes, as well as hyphochitridiomycetes and plasmodiophores, usually attributed to fungi.

The systems of A. L. Takhtadzhyan (1973), L. Margelis (1981) can serve as examples of the modern generally accepted system of organisms. Based on the data given in these works, the system of living organisms is presented in the following form.

A. Superkingdom Pre-nuclear organisms, or Prokaryotes:

I. Kingdom Bacteria.

1. Subkingdom of Bacteria.

II. Kingdom of Archaebacterium.

B. Superkingdom Nuclear organisms, or Eukaryotes:

I. Kingdom Animals.

• 1. Subkingdom Protozoa.
• 2. Subkingdom Multicellular.

II. Mushroom Kingdom.

III. Plant Kingdom:

• 1. The kingdom of Bagryanka.
• 2. Subkingdom Real algae.
• 3. Subkingdom Plants.

In addition to evolutionary, there are other directions in modern systematics. Numerical (numerical) systematics resorts to numerical data processing, giving each feature used to enter into the system a certain quantitative value. The classification is based on the degree of differences between individual organisms, depending on the calculated coefficient.

Cladistic systematics determines the rank of taxa depending on the sequence of separation of individual branches (cladons) on the phylogenetic tree, without attaching importance to the range of evolutionary changes in any group. Thus, mammals among cladists are not an independent class, but a taxon subordinate to reptiles.

However, the main method of taxonomy remains the comparative morphological one.

Modern taxonomy also determines the place of man in the system of organisms, which has a deep philosophical meaning for understanding the relationship between man and wildlife. This is no longer Homo duplex - a dual person, as a person was called in the 17th-18th centuries, but Homo sapiens - a reasonable person. In a word, in the system of wildlife, a person has the following address.

Kingdom of Eukaryotes.

Kingdom Animals.

Subkingdom Multicellular.

Type Chordates.

Subtype Vertebrates.

Superclass Terrestrial tetrapods.

Class Mammals.

Subclass Real animals (Viviparous).

Infraclass Placental.

Detachment Primates (Monkeys).

Suborder Narrow-nosed monkeys.

Family People (Hominid).

Genus Man (Homo).

Species Homo sapiens.

At the end of the 20th century, at the junction of the systematics and biochemistry of nucleic acids and proteins, a new area of ​​knowledge about living nature, gene systematics, was born. The term was proposed in 1974 by the domestic biochemist A. S. Antonov. A qualitatively new perspective has opened up for the creation of natural systems of the living world. It turned out that differences in the number, frequency of occurrence, and order of arrangement of nucleides in the DNA of different organisms are species-specific.

At the end of 1970, a new stage began in the history of gene systematics: ribosomal RNA molecules and proteins, the most ancient informational molecules, were included in the number of "molecular documents of evolution". Using a special method, it is possible to determine the composition and arrangement of nucleotide sequences in an RNA molecule, compile a data bank, carry out computer processing, and derive a special similarity coefficient indicating the degree of relatedness of taxa.

However, by studying the structure of DNA and RNA, it has not yet been possible to restore the sequence of ancestors-descendants in the historical development of the species. taxonomy nature classification

Serological studies have a great influence on systematics. Nuttal and his collaborators were one of the first to use them to elucidate the systematic position of taxa. For example, some of the zoologists believed that there was a close relationship between mice, squirrels, beavers on the one hand, and hares and rabbits on the other. Other taxonomists ranked rabbits and hares as a separate order, not classifying them as rodents. The results of serological analyzes confirmed the correctness of the latter theory, and two separate orders are currently distinguished - rodents and lagomorphs.

A cell is a natural grain of life, just as an atom is a natural grain of unorganized matter.

Teilhard de Chardin

Consideration of the phenomena of living nature according to the levels of biological structures will make it possible to study the emergence and evolution of living systems on Earth - from the simplest and less organized systems to more complex and highly organized ones. The first classifications of plants, the most famous of which was the system of Carl Linnaeus, as well as the classification of animals by Georges Buffon, were largely artificial in nature, since they did not take into account the origin and development of living organisms. Nevertheless, they contributed to the unification of all known biological knowledge, its analysis and the study of the causes and factors of the origin and evolution of living systems. Without such research, it would not be possible First of all, to move to a new level of knowledge, when living structures became objects of study for biologists, first at the cellular and then at the molecular level. Secondly, generalization and systematization of knowledge about individual species and genera of plants and animals required a transition from artificial classifications to natural ones, where the principle of genesis, the origin of new species should become the basis and, consequently, the theory of evolution was developed. Thirdly, It was descriptive, empirical biology that served as the foundation on the basis of which a holistic view of the diverse, but at the same time, a single world of living systems was formed.

The living is currently divided into ontogenetic, organismic and supraorganismal levels.

The idea of ​​the structural levels of organization of living systems was formed under the influence of the discovery of the cellular theory of the structure of living bodies. In the middle of the last century, the cell was considered as an elementary unit of living matter, like an atom of inorganic bodies. The study of the problem of the structure of the living, studied by molecular biology, in the middle of the 20th century led to a scientific revolution. In the second half of the XX century. the material composition, structure of the cell and the processes occurring in it were elucidated.

Each cell contains a dense formation in the middle, called core, which floats in the "semi-liquid" cytoplasm. All of them are enclosed in cell membrane. The cell is needed for reproductive apparatus, which is at its core. Without the cell, the genetic apparatus could not exist. The basic substance of the cell proteins, molecules of which usually contain several hundred amino acids and look like beads or bracelets with key chains, consisting of the main and side chains. All living species have their own special proteins, determined by the genetic apparatus.

Proteins that enter the body are broken down into amino acids, which are then used by the body to build its own proteins. Nucleic acids create enzymes, controlling reactions. Although the composition of the proteins of the human body includes 20 amino acids, but only 9 are absolutely obligatory for it. The rest, apparently, are produced by the body itself. A characteristic feature of the amino acids contained not only in the human body, but also in other living systems (animals, plants and even viruses), is that they are all left-handed isomers of the plane of polarization, although in principle there are amino acids and right rotation.

Further research was aimed at studying the mechanisms of reproduction and heredity in the hope of discovering in them that specific thing that distinguishes the living from the non-living. The most important discovery along this path was the isolation from the composition of the cell nucleus of a rich phosphorus substance, which has the properties of an acid and was later named nucleic acid. Subsequently, it was possible to identify the carbohydrate component of these acids, one of which contained D-deoxyribose, and the other P-ribose. Accordingly, the first type of acids became known as deoxyribonucleic acids, or abbreviated DNA, and the second type - ribonucleic, or briefly RNA.

Sections of DNA that exist as functionally indivisible units - genes, encode the structure (amino acid sequence) of a single protein or ribonucleic acid. The totality of the genes of a cell or the whole organism is genotype. Unlike the genotype genome silt gene pool represents a characteristic of a species, not an individual. In 2001, the human genome was deciphered. The length of the human genome (all DNA in 46 chromosomes) reaches 2 m and includes 3 billion nucleotide pairs.

The role of DNA in the storage and transmission of heredity was elucidated after, in 1944, American microbiologists managed to prove that free DNA isolated from pneumococci has the ability to transmit genetic information.

complementarity- mutual correspondence, which ensures the connection of complementary structures (macromolecules, molecules, radicals) B and is determined by their chemical properties. Complementarity is possible "if the surfaces of the molecules have complementary structures so that the protruding group (or positive charge) on one surface corresponds to the cavity (or negative charge) on the other. In other words, interacting molecules should fit together like a key to a lock" (J. Watson). The complementarity of nucleic acid chains is based on the interaction of their constituent nitrogenous bases. So, only when adenine (A) is located in one chain against thymine (T) (or uracil - U) - in the other, and guanine (G) - against cytosine (C) in these chains, hydrogen bonds arise between the bases. Complementarity is apparently the only and universal chemical mechanism of matrix storage and transmission of genetic information.

In 1953, James Watson and Francis Crick proposed and experimentally confirmed the hypothesis of the structure of the DNB molecule as a material carrier of information. In the 1960s French scientists Francois Jacob and Jacques Monod solved one of the most important problems of gene activity, revealing the fundamental feature of the functioning of living nature at the molecular level. He proved that according to their functional activity all genes are divided into "regulatory" genes encoding the structure of the regulatory protein and "structural genes" encoding the synthesis of enzymes.

The reproduction of one's own kind and the inheritance of traits is carried out with the help of hereditary information, the material carrier of which is the molecules of deoxyribonucleic acid (DNA) DNA consists of two chains that go in opposite directions and twist one around the other like electrical wires. It resembles a spiral staircase. The portion of a DNA molecule that serves as a template for the synthesis of a single protein is called a gene. Genes are located on chromosomes (parts of cell nuclei). It has been proven that the main function of genes is to code for protein synthesis. The mechanism for transferring information from DNA to morphological structures was proposed by the well-known theoretical physicist G. Gamow, indicating that a combination of three DNA nucleotides is required to encode one amino acid.

The molecular level of the study made it possible to show that the main mechanism of variability and subsequent selection are mutations that occur at the molecular genetic level. A mutation is a partial change in the structure of a gene. Its ultimate effect is to change the properties of the proteins encoded by the mutant genes. The trait that appeared as a result of a mutation does not disappear, but accumulates. Mutations are caused by radiation, chemical compounds, temperature changes, and finally, they can be simply random. The action of natural selection is manifested at the level of a living, integral organism.

Since the cell can be considered the minimum independent living system, the study of the ontogenetic level should begin precisely with the cell. Currently, there are three types of the ontogenetic level of organization of living systems, which represent three lines of development of the living world: 1) prokaryotes - cells lacking nuclei; 2) eukaryotes that appeared later - cells containing nuclei;

3) archaebacteria - whose cells are similar, on the one hand, to prokaryotes, on the other, to eukaryotes. Apparently, all these three lines of development proceed from a single primary minimal living system, which can be called a protocell. A structural approach to the analysis of primary living systems at the ontogenetic level needs additional coverage of the functional features of their vital activity and metabolism.

Cells form tissues, and several types of tissues form organs. Groups of organs associated with the solution of some common tasks, I call body systems.

The ontogenetic level of organization refers to individual living organisms - unicellular and multicellular. In different organisms, the number of cells varies significantly. In accordance with the number of cells, all living organisms are divided into five kingdoms.

The first living organisms had single cells, then the evolution of life complicated the structure and the number of cells increased. Unicellular organisms that have a simple structure are called monomers (Greek"shopegeb" - simple), or bacteria. Single-celled organisms with a more complex structure belong to the kingdom of algae, or prostites. Among algae there are also protozoa multicellular organisms. Multicellular include plants, fungi and animals. Living organisms are classified according to their evolutionary relationship, therefore it is believed that multicellular organisms had prostates as their ancestors, and those descended from Moner. But the three multicellular kingdoms originated from different prostites. Each group of multicellular organisms - plants, animals and fungi - has its own structural plan adapted to its way of life, and each species in the process of evolution has developed a certain version of this rather flexible plan. Almost every species consists of groups of individuals differing in structure, but at the same time consanguineously related. A species is not a simple collection of individuals, but a complex system of groupings, subordinate and closely related to each other.

Here is a very simplified scheme of subordination of systematic units used for natural classification:

VIEW is the main structural and classification (taxonomic) unit in the taxonomy of living organisms. The species is designated in accordance with the binary nomenclature.

Genus - the main supraspecific taxonomic unit category (rank) in the taxonomy of plants and animals, unites species close in origin.

CLASS (lat."s1a881 $" - category, group), one of the highest taxonomic categories (ranks) in the taxonomy of animals and plants. A species is united by related orders (animals) or orders (plants). The class has a common structural plan and common ancestors, includes muds (animals) B or departments (plants).

TYPE - taxonomic category (rank) in animal taxonomy. A type (sometimes a subtype first) combines classes that are close in origin. All representatives of the same type have a single building plan. Ti reflects the main branches of the phylogenetic tree of animals. All animals belong to 16 types. In the taxonomy of plants, a department corresponds to a type.

SUBKINGDOM (unicellular, multicellular).

KINGDOM (plants, animals, fungi, pellets, viruses) - the highest taxonomic category (rank). Since the time of Aristotle, the world has been organically divided into two kingdoms - plants and animals, and according to the latest systematics - into five kingdoms.

SUPERKINGDOM (non-nuclear and nuclear).

EMPIRE (precellular and cellular).

The well-known German biologist E. Haeckel discovered the biogenetic law for the organismic level of classification of the living, according to which ontogeny in brief repeats phylogenesis, i.e. an individual organism in its individual development repeats the history of the genus in an abbreviated form.

The supraorganismal level considers organisms in relation to the environment and begins with the population. The population level begins with the study of the relationship and interaction between sets of individuals of the same species that have a single gene pool and occupy a single territory. Such collections, or rather systems of living organisms, constitute a certain population. It is obvious that the population level goes beyond the scope of an individual organism, and therefore it is called the supraorganismal level of organization. The population is the first supraorganismal level of organization of living beings, which, although closely related to their ontogenetic and molecular levels, qualitatively differs from them in the nature of the interaction of constituent elements, because in this interaction they act as integral communities of organisms. According to modern ideas, it is populations that serve as elementary units of evolution.

The second supraorganismal level of organization of living things is made up of various systems of populations, which are called biocenoses, or communities. They are more extensive associations of living beings and to a much greater extent depend on non-biological, or abiotic, factors of development.

The third supraorganismal level of organization contains various biocenoses as elements, and is even more characterized by dependence on numerous terrestrial and abiotic conditions of its existence (geographical, climatic, hydrological, atmospheric, etc.). The term biogeocenosis or ecological system (ecosystems) is used to designate it.

The fourth superorganismal level of organization arises from the unification of a wide variety of biogeocenoses and is now called the biosphere.

To characterize the trophic (food) interaction of a population and biocenoses, the general rule is essential, according to which the longer and more complex the food links between organisms and populations, the more viable and stable a living system of any (supra-organismal) level is. From this it becomes clear that from a biological point of view, at this level, the trophic nature of the interaction between the elements that make up the living system acquires decisive importance.

Thus, based on the criterion of scale, the following levels of organization of the living are distinguished (Fig. 13.1):

biospheric- including the totality of living organisms of the Earth together with their natural environment;

the level of biogeocenoses, consisting of areas of the Earth with a certain composition of living and non-living components, representing a single natural complex, ecosystem;

population-species- formed by freely interbreeding individuals of the same species;

organismal and organ-tissue- reflect the signs of individual individuals, their structure, physiology, behavior, as well as the structure and function of organs and tissues of living beings;

cellular and subcellular- reflect the processes of cell specialization, as well as various intracellular inclusions;

molecular- is the subject of molecular biology, one of the most important problems of which is the study of the mechanisms of transfer of genetic information and the development of genetic engineering and biotechnology.

A living organism is the main subject studied by such a science as biology. It is a complex system consisting of cells, organs and tissues. A living organism is one that has a number of characteristic features. He breathes and eats, stirs or moves, and also has offspring.

Life Science

The term "biology" was introduced by J.B. Lamarck - a French naturalist - in 1802. At about the same time and independently of him, the German botanist G.R. gave such a name to the science of the living world. Treviranus.

Numerous branches of biology consider the diversity of not only currently existing, but also already extinct organisms. They study their origin and evolutionary processes, structure and function, as well as individual development and relationships with the environment and with each other.

Sections of biology consider particular and general patterns that are inherent in all living things in all properties and manifestations. This applies to reproduction, and metabolism, and heredity, and development, and growth.

The beginning of the historical stage

The first living organisms on our planet differed significantly in their structure from those currently existing. They were incomparably simpler. Throughout the entire stage of the formation of life on Earth, He contributed to the improvement of the structure of living beings, which allowed them to adapt to the conditions of the surrounding world.

At the initial stage, living organisms in nature ate only organic components that arose from primary carbohydrates. At the dawn of their history, both animals and plants were the smallest single-celled creatures. They were similar to today's amoebas, blue-green algae and bacteria. In the course of evolution, multicellular organisms began to appear, which were much more diverse and more complex than their predecessors.

Chemical composition

A living organism is one that is formed by molecules of inorganic and organic substances.

The first of these components is water, as well as mineral salts. found in the cells of living organisms are fats and proteins, nucleic acids and carbohydrates, ATP and many other elements. It is worth noting the fact that living organisms in their composition contain the same components that objects have. The main difference is in the ratio of these elements. Living organisms are those ninety-eight percent of whose composition is hydrogen, oxygen, carbon and nitrogen.

Classification

The organic world of our planet today has almost one and a half million diverse animal species, half a million plant species, and ten million microorganisms. Such diversity cannot be studied without its detailed systematization. The classification of living organisms was first developed by the Swedish naturalist Carl Linnaeus. He based his work on the hierarchical principle. The unit of systematization was the species, the name of which was proposed to be given only in Latin.

The classification of living organisms used in modern biology indicates family ties and evolutionary relationships of organic systems. At the same time, the principle of hierarchy is preserved.

The totality of living organisms that have a common origin, the same chromosome set, adapted to similar conditions, living in a certain area, freely interbreeding and producing offspring capable of reproduction, is a species.

There is another classification in biology. This science divides all cellular organisms into groups according to the presence or absence of a formed nucleus. This is

The first group is represented by nuclear-free primitive organisms. A nuclear zone stands out in their cells, but it contains only a molecule. These are bacteria.

The true nuclear representatives of the organic world are eukaryotes. The cells of living organisms of this group have all the main structural components. Their core is also clearly defined. This group includes animals, plants and fungi.

The structure of living organisms can be not only cellular. Biology studies other forms of life. These include non-cellular organisms, such as viruses, as well as bacteriophages.

Classes of living organisms

In biological systematics, there is a rank of hierarchical classification, which scientists consider one of the main ones. He distinguishes classes of living organisms. The main ones include the following:

bacteria;

Animals;

Plants;

Seaweed.

Description of classes

A bacterium is a living organism. It is a unicellular organism that reproduces by division. The cell of a bacterium is enclosed in a shell and has a cytoplasm.

Mushrooms belong to the next class of living organisms. In nature, there are about fifty thousand species of these representatives of the organic world. However, biologists have studied only five percent of their total. Interestingly, fungi share some characteristics of both plants and animals. An important role of living organisms of this class lies in the ability to decompose organic material. That is why mushrooms can be found in almost all biological niches.

The animal world boasts a great diversity. Representatives of this class can be found in areas where, it would seem, there are no conditions for existence.

Warm-blooded animals are the most highly organized class. They got their name from the way they feed their offspring. All representatives of mammals are divided into ungulates (giraffe, horse) and carnivores (fox, wolf, bear).

Representatives of the animal world are insects. There are a huge number of them on Earth. They swim and fly, crawl and jump. Many of the insects are so small that they are not even able to withstand water tension.

Amphibians and reptiles were among the first vertebrates that came to land in distant historical times. Until now, the life of representatives of this class is connected with water. So, the habitat of adults is dry land, and their breathing is carried out by lungs. The larvae breathe through gills and swim in the water. Currently, there are about seven thousand species of this class of living organisms on Earth.

Birds are unique representatives of the fauna of our planet. Indeed, unlike other animals, they are able to fly. Almost eight thousand six hundred species of birds live on Earth. Representatives of this class are characterized by plumage and oviposition.

Fish belong to a huge group of vertebrates. They live in water bodies and have fins and gills. Biologists divide fish into two groups. These are cartilage and bone. Currently, there are about twenty thousand different types of fish.

Within the class of plants there is its own gradation. Representatives of the flora are divided into dicots and monocots. In the first of these groups, the seed contains an embryo consisting of two cotyledons. You can identify representatives of this species by the leaves. They are pierced with a mesh of veins (corn, beets). The embryo has only one cotyledon. On the leaves of such plants, the veins are arranged in parallel (onions, wheat).

The class of algae includes more than thirty thousand species. These are water-dwelling spore plants that do not have vessels, but have chlorophyll. This component contributes to the implementation of the process of photosynthesis. Algae do not form seeds. Their reproduction occurs vegetatively or by spores. This class of living organisms differs from higher plants in the absence of stems, leaves and roots. They have only the so-called body, which is called the thallus.

Functions inherent in living organisms

What is fundamental for any representative of the organic world? This is the implementation of the processes of energy and matter exchange. In a living organism, there is a constant transformation of various substances into energy, as well as physical and chemical changes.

This function is an indispensable condition for the existence of a living organism. It is thanks to metabolism that the world of organic beings differs from the inorganic. Yes, in inanimate objects there are also changes in matter and the transformation of energy. However, these processes have their fundamental differences. The metabolism that occurs in inorganic objects destroys them. At the same time, living organisms without metabolic processes cannot continue their existence. The consequence of metabolism is the renewal of the organic system. The cessation of metabolic processes entails death.

The functions of a living organism are varied. But all of them are directly related to the metabolic processes taking place in it. This can be growth and reproduction, development and digestion, nutrition and respiration, reactions and movement, excretion of waste products and secretion, etc. The basis of any function of the body is a set of processes of transformation of energy and substances. Moreover, this is equally relevant to the capabilities of both tissue, cell, organ, and the whole organism.

Metabolism in humans and animals includes the processes of nutrition and digestion. In plants, it is carried out with the help of photosynthesis. A living organism in the implementation of metabolism supplies itself with the substances necessary for existence.

An important distinguishing feature of the objects of the organic world is the use of external energy sources. An example of this is light and food.

Properties inherent in living organisms

Any biological unit has in its composition separate elements, which, in turn, form an inextricably linked system. For example, in the aggregate, all organs and functions of a person represent his body. The properties of living organisms are diverse. In addition to a single chemical composition and the possibility of implementing metabolic processes, objects of the organic world are capable of organization. Certain structures are formed from the chaotic molecular movement. This creates a certain order in time and space for all living things. Structural organization is a whole complex of the most complex self-regulating processes that proceed in a certain order. This allows you to maintain the constancy of the internal environment at the required level. For example, the hormone insulin reduces the amount of glucose in the blood when it is in excess. With a lack of this component, it is replenished by adrenaline and glucagon. Also, warm-blooded organisms have numerous mechanisms of thermoregulation. This is the expansion of skin capillaries, and intense sweating. As you can see, this is an important function that the body performs.

The properties of living organisms, characteristic only for the organic world, are also included in the process of self-reproduction, because the existence of any has a time limit. Only self-reproduction can sustain life. This function is based on the process of formation of new structures and molecules, due to the information that is embedded in DNA. Self-reproduction is inextricably linked with heredity. After all, each of the living beings gives birth to their own kind. Through heredity, living organisms transmit their developmental features, properties and signs. This property is due to constancy. It exists in the structure of DNA molecules.

Another property characteristic of living organisms is irritability. Organic systems always react to internal and external changes (impacts). As for the irritability of the human body, it is inextricably linked with the properties inherent in muscle, nervous, and glandular tissue. These components are able to give impetus to the response after muscle contraction, the departure of a nerve impulse, as well as the secretion of various substances (hormones, saliva, etc.). And if a living organism is deprived of the nervous system? The properties of living organisms in the form of irritability are manifested in this case by movement. For example, protozoa leave solutions in which the salt concentration is too high. As for plants, they are able to change the position of the shoots in order to absorb light as much as possible.

Any living system can respond to the action of a stimulus. This is another property of the objects of the organic world - excitability. This process is provided by muscle and glandular tissues. One of the final reactions of excitability is movement. The ability to move is a common property of all living things, despite the fact that outwardly some organisms are deprived of it. After all, the movement of the cytoplasm occurs in any cell. Attached animals also move. Growth movements due to an increase in the number of cells are observed in plants.

Habitat

The existence of objects of the organic world is possible only under certain conditions. Some part of space invariably surrounds a living organism or a whole group. This is the habitat.

In the life of any organism, organic and inorganic components of nature play a significant role. They have an effect on him. Living organisms are forced to adapt to existing conditions. So, some of the animals can live in the Far North at very low temperatures. Others are able to exist only in the tropics.

There are several habitats on planet Earth. Among them are:

Land-water;

ground;

soil;

Living organism;

Ground-air.

The role of living organisms in nature

Life on planet Earth has been around for three billion years. And during all this time organisms developed, changed, settled and at the same time affected their environment.

The influence of organic systems on the atmosphere caused the appearance of more oxygen. This significantly reduced the amount of carbon dioxide. Plants are the main source of oxygen production.

Under the influence of living organisms, the composition of the waters of the World Ocean has also changed. Some rocks are of organic origin. Minerals (oil, coal, limestone) are also the result of the functioning of living organisms. In other words, the objects of the organic world are a powerful factor that transforms nature.

Living organisms are a kind of indicator indicating the quality of the human environment. They are connected by complex processes with vegetation and soil. With the loss of at least a single link from this chain, an imbalance of the ecological system as a whole will occur. That is why for the circulation of energy and substances on the planet it is important to preserve all the existing diversity of representatives of the organic world.

Abstract keywords: diversity of living organisms, systematics, biological nomenclature, classification of organisms, biological classification, taxonomy.

Currently, more than 2.5 million species of living organisms have been described on Earth. To streamline the diversity of living organisms are systematics, classification and taxonomy.

Systematics - a branch of biology, the task of which is to describe and divide into groups (taxons) of all currently existing and extinct organisms, to establish family ties between them, to elucidate their common and particular properties and characteristics.

Sections of biological systematics are biological nomenclature and biological classification.

Biological nomenclature

Biollogical nomenclature is that each species receives a name consisting of generic and specific names. The rules for assigning appropriate names to species are regulated international nomenclature codes.

For international species names, use Latin language . The full name of the species also includes the name of the scientist who described the species, as well as the year of publication of the description. For example, the international name house sparrow - Passer domesticus(Linnaeus, 1758), a field sparrow - Passer montanus(Linnaeus, 1758). Usually, in printed text, species names are italicized, but the name of the describer and the year of description are not.

The requirements of the codes apply only to international species names. In Russian, you can write and " field sparrow " and " tree sparrow ».

biological classification

The classification of organisms uses hierarchical taxa(systematic groups). Taxa have different ranks(levels). The ranks of taxa can be divided into two groups: obligatory (any classified organism belongs to the taxa of these ranks) and additional (used to clarify the relative position of the main taxa). When systematizing different groups, a different set of additional taxon ranks is used.

Taxonomy- a section of systematics that develops the theoretical foundations of classification. Taxon a group of organisms artificially identified by a person, related to one degree or another of kinship and. at the same time, it is sufficiently isolated so that it can be assigned a certain taxonomic category of one rank or another.

In the modern classification, there is the following taxon hierarchy: kingdom, department (type in animal taxonomy), class, order (squad in animal taxonomy), family, genus, species. In addition, allocate intermediate taxa : over- and sub-kingdoms, over- and sub-divisions, over- and sub-classes, etc.

Table "Diversity of living organisms"

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The science of classifying animals is called systematics or taxonomy. This science determines the relationship between organisms. The degree of relationship is not always determined by external similarity. For example, marsupial mice are very similar to ordinary mice, and tupai are very similar to squirrels. However, these animals belong to different orders. But armadillos, anteaters and sloths, completely different from each other, are united in one squad. The fact is that family ties between animals are determined by their origin. By studying the structure of the skeleton and the dental system of animals, scientists determine which animals are closest to each other, and paleontological finds of ancient extinct animal species help to establish more accurately the relationship between their descendants. plays an important role in animal taxonomy genetics the science of the laws of heredity.

The first mammals appeared on Earth about 200 million years ago, having separated from the animal-like reptiles. The historical path of development of the animal world is called evolution. In the course of evolution, natural selection took place - only those animals survived that managed to adapt to environmental conditions. Mammals have developed in different directions, forming many species. It so happened that animals with a common ancestor at some stage began to live in different conditions and acquired different skills in the struggle for survival. Their appearance was transformed, from generation to generation, changes useful for the survival of the species were fixed. Animals whose ancestors looked the same relatively recently began to differ greatly from each other over time. Conversely, species that had different ancestors and passed through different evolutionary paths sometimes find themselves in the same conditions and, changing, become similar. Thus, unrelated species acquire common features, and only science can trace their history.

Classification of the animal world

The living nature of the Earth is divided into five kingdoms: bacteria, protozoa, fungi, plants and animals. Kingdoms, in turn, are divided into types. Exist 10 types Animals: sponges, bryozoans, flatworms, roundworms, annelids, coelenterates, arthropods, molluscs, echinoderms and chordates. Chordates are the most advanced type of animal. They are united by the presence of a chord - the primary skeletal axis. The most highly developed chordates are grouped into the vertebrate subphylum. Their notochord is transformed into a spine.

kingdoms

Types are divided into classes. Total exists 5 classes of vertebrates: fish, amphibians, birds, reptiles (reptiles) and mammals (animals). Mammals are the most highly organized animals of all vertebrates. All mammals are united by the fact that they feed their young with milk.

The mammal class is divided into subclasses: oviparous and viviparous. Oviparous mammals reproduce by laying eggs like reptiles or birds, but the young are suckled. Viviparous mammals are divided into infraclasses: marsupials and placentals. Marsupials give birth to underdeveloped cubs, which are carried for a long time in the mother's brood pouch. In placental, the embryo develops in the womb and is born already formed. Placental mammals have a special organ - the placenta, which exchanges substances between the mother's organism and the embryo during intrauterine development. Marsupials and oviparous do not have a placenta.

Animal types

Classes are divided into squads. Total exists 20 orders of mammals. In the subclass of oviparous - one order: monotremes, in the infraclass of marsupials - one order: marsupials, in the infraclass of placental 18 orders: edentulous, insectivorous, woolly wings, bats, primates, carnivores, pinnipeds, cetaceans, sirens, proboscis, hyraxes, aardvarks, artiodactyls, calluses, lizards, rodents and lagomorphs.

Mammal class

Some scientists distinguish an independent detachment of tupaya from the order of primates, a detachment of jumping birds is isolated from the order of insectivores, and predatory and pinnipeds are combined into one order. Each order is divided into families, families - into genera, genera - into species. In total, about 4,000 species of mammals currently live on earth. Each individual animal is called an individual.