1. A certain single chemical composition. Living organisms are made up of the same substances as inanimate objects,
but the ratio of these elements is different.
The basic elements of living beings are C(carbon), O(oxygen), N(nitrogen) and H(hydrogen).
2. Metabolism and energy dependence. Living organisms are open systems
they depend on the intake of substances and energy from the environment.
3. Self-reproduction. Living organisms are able to reproduce - to reproduce their own kind.
4. Heredity. The ability to transmit traits and properties (hereditary information) from generation to generation using DNA and RNA molecules.
5. Variability. The ability to acquire new features and properties.
6. Ability to grow and develop.
a) ontogeny. Individual development from birth to the end of life
(death or new division), accompanied by growth, is characteristic of each individual.
b) Phylogeny. Evolutionary development lies in the historical development
life on Earth from its inception to the present.
7. Irritability. Living organisms are able to respond to certain external influences (changes in the environment) with specific reactions.
8. Integrity and discreteness. All matter is integral, organized in a certain way and subject to a common law,
however, it also consists of separate, albeit connected, elements.
Self-regulation. The ability to maintain homeostasis is the constancy of its chemical composition.
Adaptation. The ability of organisms to adapt to their environment.
Rhythm. The manifestation of a special rhythm of life activity (daily, seasonal, etc.)
Hierarchy. Finding all living matter in a special subordination to each other,
in which biological systems of a less complex level makes it possible for more complex systems to exist.
All living organisms have a cellular structure, with the exception of viruses.
14. Scientific research methods
two main levels of scientific knowledge: empirical and theoretical
The empirical level of knowledge includes
observation of phenomena
Accumulation and selection of facts
Establishing links between them.
The empirical level is the stage of collecting data (facts) about social and natural objects
The theoretical level of knowledge is associated with the predominance of mental activity, with the comprehension of empirical material, its processing. On theoretical level revealed
Internal structure and patterns of development of systems and phenomena
Their interaction and conditionality.
General methods of scientific knowledge are usually divided into two large groups:
methods of empirical research (observation, comparison, measurement, experiment);
methods of theoretical research (abstraction, analysis and synthesis, idealization, induction and deduction, mental modeling, ascent from the abstract to the concrete, etc.).
Methods of empirical research
surveillance,
comparison,
measurement,
experiment
material modeling
Observation
Methods used at the theoretical level of research
Such methods are considered
abstraction,
axiomatic,
analysis and synthesis,
idealization,
induction and deduction
mental Modeling,
ascending from the abstract to the concrete
12. Fundamental properties of living matter
Biology as a science and its place in modern natural science
The goal of biology is the knowledge of life - a phenomenon that occupies a special place in the worldview. Biology today is a complex of scientific disciplines that study living organisms, their structure, functioning, distribution, origin and development, as well as the natural communities of organisms, their relationship with each other, with inanimate nature and man. Together with astronomy, physics, chemistry, geology and other sciences that study Nature, biology is one of the natural sciences.
The existence and development of inanimate nature is determined by complex physical and chemical processes, which are also fundamental for living nature. However, with the advent of living organisms (fundamentally different in their properties from the bodies of living nature), biological processes begin to take place, which have a specific character and are subject to new laws - biological ones. Thus, physical and chemical processes in living nature are fundamental, primary, and biological processes arising on their basis are derivatives, secondary. Man is a particularly complex phenomenon - it combines biological and social essence. Possessing, unlike all other living organisms, reason, language, the ability to creative activity, deep sociality, a person is subject to the action of both physico-chemical and biological, and social laws.
The rapid development and grandiose achievements in the 20th century of such biological sciences as biochemistry, biophysics, genetics, molecular biology, ecology led to a significant expansion and deepening of our ideas about the unity of the material world, about the presence of complex relationships between inanimate, living nature and humanity. Thus, the development of the doctrine of the biosphere, ecology as a whole showed that living organisms ("living matter" according to) are a powerful geological factor on a planetary scale; that at present humanity is an even more powerful environmental factor, influencing both the inanimate and animate nature of the Earth.
Determining the place and role of biology in modern natural science, it is necessary to note its importance for the development of such new directions in science as cybernetics, synergetics, and general systems theory. Indeed, after all, living systems are nothing more than open dissipative systems that are studied by synergetics. The cybernetic approach to the study of living systems is widely and fruitfully used in biology, and, “by the feedback principle”, biology contributes to the development of this direction in science. Finally, the basics general theory systems were laid down by the works of the biologist L. Bertalanffy, who was actively looking for new ways of understanding life.
All of the above explains the need to form, within the framework of modern natural science, a holistic view of the material world, an integral component of which is human society which largely determines today the further existence and development of this world.
Substratum of life
The difference between animate and inanimate nature is clearly manifested already at the level of their chemical composition. If Earth's crust 90% consists of O, Si, Al and Na, then in living organisms about 95% are C, H, O, N. In addition, this group (macroelements) includes eight more elements - Na, Cl, S, P , Ca, K, Mg, Fe, the content of which is calculated in fractions of a percent. In smaller quantities, microelements that are equally necessary for life are found - Cu, Mn, Zn, Mo, Co, F, I, Se, B. Only 27 elements are known to perform certain functions in organisms. It is no coincidence that the basis of living organisms is made up of chemical elements (called organogens) - hydrogen, carbon, oxygen and nitrogen, which mainly consist of organic substances (proteins, carbohydrates, fats, etc.). The first place among organogens undoubtedly belongs to carbon. This chemical element is characterized by the ability to form strong (and therefore energy-intensive) and labile bonds. It is, to a greater extent than all other elements on Earth, capable of forming large molecules, can combine with other carbon atoms in chains and rings. The result is complex molecules of huge size, characterized by "infinite" variety. Carbon atoms in the same compound are capable of playing the role of both an electron acceptor and an electron donor; can form almost all types of bonds known to chemistry. The high content of oxygen and hydrogen in living organisms is indisputably associated with the presence of oxidizing and reducing properties, respectively. Nitrogen is included in organic matter, which are of paramount importance for life processes - proteins and nucleic acids. Sulfur, phosphorus and other elements, like carbon, are characterized by lability, and their interaction creates an exceptional wealth of chemical bonds.
A sign of life at the molecular level are extremely diverse organic compounds. They are both structural and functional components of organisms, playing an important role in the processes of metabolism and energy. The basis of the living, or, in other words, substratum of life are proteins and nucleic acids - biopolymers that are in close interaction and interdependence. Proteins are not only the building material of living things, they play essential role in all vital functions (including in the process of nucleic acid synthesis), acting as biocatalysts (proteins - enzymes). Nucleic acids, in turn, predetermine the structure of all proteins synthesized in the body. Moreover, all living organisms on Earth have a universal genetic code - each of the twenty amino acids that form all the proteins of the body corresponds to a certain sequence of three nucleotides in the polynucleotide chain.
Thus, a characteristic feature of the substratum of life is its structural organization. Living matter built from the same chemical elements, which is inanimate, is characterized by extreme complexity chemical compounds due to a certain order at the molecular level. Orderliness in space is accompanied by orderliness in time, which ensures a strict sequence of processes occurring in living systems.
Modern ideas about the essence of life
The classic definition of life was the formulation of F. Engels: “Life is a way of existence of protein bodies, the essential point of which is the constant exchange of substances with the external nature surrounding them, and with the cessation of this metabolism, life also stops, which leads to the decomposition of protein”, And further : "... metabolism consists in the absorption of substances whose chemical composition changes, which are assimilated by the body and the remains of which are excreted along with the decomposition products of the organism itself generated during the life process." This thesis is supplemented by a very significant note by F. Engels himself: “In inorganic bodies, too, a similar metabolism can occur, which going on in the course of time, everywhere, because chemical actions take place everywhere, even if very slowly. But the difference lies in the fact that in the case of inorganic bodies metabolism destroys them, while in the case of organic bodies it is a necessary condition for their existence. Engels was far ahead of his time, and one can only be amazed at how, in the state of science of that time, he managed to see the main thing and point out the most fundamental in characterizing the essence of the living.
An outstanding biochemist, academician, noted that “the ability of living things to create order from the chaotic thermal motion of molecules is the most profound, fundamental difference between living and non-living. The tendency to order, to create order out of chaos, is nothing but the opposition to entropy. More figuratively speaking about this outstanding physicist XX century E. Schrödinger: “A living organism can avoid the state of maximum entropy, which is death, only by constantly extracting negative entropy from its environment. Negative entropy is what the organism feeds on. Or, to put it less paradoxically, what is essential in metabolism is that the organism manages to rid itself of all the positive entropy it has to produce while it is alive.”
Summarizing the achievements of modern natural science in the field of the theory of open dissipative systems, the famous biophysicist defined the living bodies that exist on Earth as "open self-regulating and self-reproducing systems consisting of biopolymers: proteins and nucleic acids."
Despite the abundance of statements about the phenomenon of life, to give a brief and unambiguous definition of life seems to be very difficult today. challenging task. "Life" does not exist by itself - it is only a specific quality certain systems called "living" or "biological". Life, in its specific manifestations on Earth, is represented by a variety of organisms. Based on the achievements of modern biology, it is possible to single out a set of properties that are common to all living beings and distinguish them from bodies of inanimate nature. Thus, we come to the concept of "life" by comprehending the specific properties of living organisms.
Levels of organization of the living
By the 60s of the current century, there was an idea of the levels of organization of the living as a concrete expression of hierarchical order. Life on Earth is represented by organisms of a certain structure, belonging to certain systematic groups (population, species), as well as communities of varying complexity (biogeocenoses, biosphere). In turn, organisms are characterized by molecular, cellular, tissue, organ structure. Each organism, on the one hand, consists of units of levels of organization subordinate to it (organs, tissues, etc.), on the other hand, it is itself a unit in the composition of supraorganismal biological systems (populations, species, biogeocenoses, the biosphere as a whole).
The existence of life at all levels is determined by the structure of the lower level. For example, the nature of the cellular level of organization is determined by the molecular and subcellular levels; organismic - cellular, tissue, organ; population-specific - organismal, etc. It should be noted the great similarity of discrete units at the lower levels and the ever-increasing difference at the higher levels.
According to the approach to the study of biological systems, the following levels of organization of living matter are distinguished on the basis of different ways structural and functional association of constituent elements:
Table 12.2
Definition and brief description |
|
Molecular | 20 amino acids and 4 nitrogenous bases that make up nucleic acid molecules |
Cellular | The cell is the basic independently functioning elementary biological unit, characteristic of all organisms. Biosynthesis and realization are possible only at the cellular level hereditary information. In unicellular organisms, this level coincides with the organism |
Tissue-organ | A collection of cells with the same type of organization constitutes a tissue. Jointly functioning cells belonging to different tissues make up organs. Only 5 main tissues are part of the organs of all multicellular animals and 6 main tissues form the organs of plants |
Organismic or ontogenetic | It is characterized by an unimaginable variety of forms. Currently, more than a million species of animals and about half a million species of higher plants live on Earth. The organism as a whole (individual) is an elementary unit of life. Outside individuals, life does not exist. At this level, the processes of ontogeny take place. |
Population- | A set of organisms (individuals) of the same species inhabiting a certain territory, interbreeding freely with each other, constitutes a population. The population is the elementary unit of the evolutionary process; it begins the process of speciation |
Biocenotic | Biocenoses are historically established stable communities of populations different types, connected with each other and with the surrounding inanimate nature by the exchange of substances, energy and information. They are elementary systems in which the material-energy cycle is carried out, due to the vital activity of organisms |
biospheric | Biosphere - an area of active life, covering the lower part of the atmosphere, the hydrosphere and the upper part of the lithosphere, where living organisms (living matter) and their habitat are organically connected and interact with each other, forming an integral dynamic system |
Fundamental properties of living matter
Metabolism (metabolism)
Metabolism (metabolism) - a set of chemical transformations occurring in living systems that ensure their vital activity, growth, reproduction, development, self-preservation, constant contact with the environment, the ability to adapt to it and its changes. In the process of metabolism, splitting and synthesis of molecules that make up cells occur; formation, destruction and renewal of cellular structures and intercellular substance. Metabolism is based on interrelated processes of assimilation (anabolism) and dissimilation (catabolism). Assimilation - the processes of synthesis of complex molecules from simple ones with the expenditure of energy stored during dissimilation (as well as the accumulation of energy during the deposition of synthesized substances in the reserve). Dissimilation - the processes of splitting (anaerobic or aerobic) of complex organic compounds, going with the release of energy necessary for the implementation of the vital activity of the organism.
Unlike bodies of inanimate nature, exchange with the environment for living organisms is a condition for their existence. In this case, the destroyed (“used”) components are restored, they are replaced with new, identical ones, i.e., self-renewal takes place. Here are some examples: all human liver and blood proteins are renewed every 20 days; all tissue proteins - within every 160 days; all cells of the intestinal epithelium are updated within a week.
Metabolic processes occurring inside the body are combined into metabolic cascades and cycles. chemical reactions, which are strictly ordered in time and space. Calculations for human cells are indicative - their metabolic apparatus includes more than 10,000 reactions. The coordinated flow of a large number of reactions in a small volume is achieved by the ordered distribution of individual metabolic links in the cell (the principle of compartmentalization). Metabolic processes are regulated with the help of biocatalysts - special proteins-enzymes. Each enzyme has substrate specificity to catalyze the conversion of only one substrate. This specificity is based on a peculiar “recognition” of the substrate by the enzyme. Enzymatic catalysis differs from non-biological in its extremely high efficiency, as a result of which the rate of the corresponding reaction increases by 1 times. Each enzyme molecule is capable of performing from several thousand to several million operations per minute without being destroyed in the process of participating in reactions. So, for example, one molecule of the catalase enzyme cleaves 5 million molecules of the substrate (H2O2) within one minute. For comparison, H2O2 can decompose in the presence of Fe atoms, but slowly - it would take 300 years for one iron atom to split as many H2O2 molecules as one molecule of catalase splits in one second. Another characteristic difference between enzymes and non-biological catalysts is that enzymes are able to speed up reactions when normal conditions(atmospheric pressure, body temperature of the organism, etc.).
All living organisms can be divided into two groups - autotrophs and heterotrophs, differing in sources of energy and necessary substances for their life.
Autotrophs - organisms that synthesize organic compounds from inorganic substances using the energy of sunlight (photosynthetics - green plants, algae, some bacteria) or the energy obtained from the oxidation of an inorganic substrate (chemosynthetics - sulfur, iron bacteria and some others), Autotrophic organisms are able to synthesize all components of the cell. The role of photosynthetic autotrophs in nature is decisive - being the primary producer of organic matter in the biosphere, they ensure the existence of all other organisms and the course of biogeochemical cycles in the circulation of substances on Earth (see Chapter 14).
Heterotrophs (all animals, fungi, most bacteria, some chlorophyll-free plants) are organisms that need ready-made organic substances for their existence, which, acting as food, serve as both a source of energy and a necessary " building material». characteristic feature heterotrophs is the presence of amphibolism in them, i.e. the process of formation of small organic molecules(monomers) formed during the digestion of food (the process of degradation of complex substrates). Such molecules - monomers are used to assemble their own complex organic compounds. For example, when food proteins are broken down in the intestines into amino acids, the latter then enter the cells of the body and there they “assemble” (synthesize) the proteins inherent in this organism.
Self-reproduction (reproduction)
Life exists in the form of discrete biological systems (cells, organisms, etc.) and the existence of each individual biological system is limited in time. Therefore, the maintenance of life at any level of organization is associated with reproduction.
The ability to reproduce (reproduce their own kind, self-reproduction) refers to one of the fundamental properties of living organisms. Reproduction is necessary in order to ensure the continuity of the existence of species, since the life span of an individual organism is limited. Reproduction more than compensates for the losses caused by the natural extinction of individuals, and thus maintains the preservation of the species in a number of generations of individuals. In the process of evolution of living organisms, the evolution of methods of reproduction took place. Therefore, in the numerous and diverse species of living organisms that currently exist, we find different forms of reproduction. Many types of organisms combine several methods of reproduction. It is necessary to distinguish two fundamentally different types of reproduction of organisms - asexual (primary and more ancient type of reproduction) and sexual.
In the process of asexual reproduction, a new individual is formed from one or a group of cells (in multicellular) of the mother organism. In all forms of asexual reproduction, the offspring have a genotype (set of genes) identical to the maternal one. Consequently, all the offspring of one maternal organism turns out to be genetically homogeneous and the daughter individuals have the same set of traits.
In sexual reproduction, a new individual develops from a zygote formed by the fusion of two specialized germ cells (fertilization process) produced by two parental organisms. The nucleus in the zygote contains a hybrid set of chromosomes, which is formed as a result of the union of sets of chromosomes of fused gamete nuclei. In the nucleus of the zygote, thus, a new combination of hereditary inclinations (genes) is created, brought in equally by both parents. And the daughter organism developing from the zygote will have a new combination of features. In other words, during sexual reproduction, the implementation of the combinative form hereditary variability organisms, ensuring the adaptation of species to changing environmental conditions and representing an essential factor in evolution. This is a significant advantage of sexual reproduction over asexual reproduction.
The ability of living organisms to reproduce itself is based on the unique property of nucleic acids to reproduce and the phenomenon matrix synthesis, underlying the formation of nucleic acid molecules and proteins. Self-reproduction at the molecular level determines both the implementation of metabolism in cells and the self-reproduction of the cells themselves. Cell division (self-reproduction of cells) underlies the individual development of multicellular organisms and the reproduction of all organisms. The reproduction of organisms ensures the self-reproduction of all species inhabiting the Earth, which in turn determines the existence of biogeocenoses and the biosphere.
Heredity and variability
Heredity provides material continuity (flow genetic information) between generations of organisms. It is closely related to reproduction at the molecular, subcellular and cellular levels. Genetic information that determines the diversity of hereditary traits is encrypted in the molecular structure of DNA (for some viruses, in RNA). DNA polynucleotide chains are subdivided into special functional units (genes), which are units of genetic (hereditary) information. The genes encode information about the structure of synthesized proteins, enzymatic and structural. The genetic code is a system of "recording" information about the sequence of amino acids in synthesized proteins using the sequence of nucleotides in the DNA molecule.
The totality of all the genes in an organism is called genotype, and the set of features - phenotype. The phenotype depends on both the genotype and the factors of the internal and external environment that affect the activity of genes and determine regular processes. The storage and transmission of hereditary information is carried out in all organisms with the help of nucleic acids, the genetic code is the same for all living beings on Earth, that is, it is universal. Due to heredity, traits are transmitted from generation to generation that ensure the adaptability of organisms to their environment.
If during the reproduction of organisms only the continuity of existing signs and properties was manifested, then against the background of changing environmental conditions, the existence of organisms would be impossible, since a necessary condition for the life of organisms is their adaptability to environmental conditions. With "hard" heredity, the evolutionary process could not be carried out either. But living organisms are characterized by variability, which is understood as the property of the living to acquire new features and lose the old ones. There is variability in the diversity of organisms belonging to the same species. Variability can be realized in individual organisms in the course of their individual development or within a group of organisms in a series of generations during reproduction.
There are two main forms of variability, which differ in the mechanisms of occurrence, the nature of the change in characteristics and, finally, their significance for the existence of living organisms - genotypic (hereditary) and modification (non-hereditary).
Genotypic variability is associated with a change in the genotype and leads to a change in the phenotype. The basis of genotypic variability may be mutations (mutational variability) or new combinations of genes that arise in the process of fertilization during sexual reproduction. In the mutational form, changes are associated primarily with errors in the replication of nucleic acids. Thus, the emergence of new genes that carry new genetic information; new signs appear. And if the newly emerging signs are useful to the organism in specific conditions, then they are “caught up” and “fixed” by natural selection. Thus, the adaptability of organisms to environmental conditions, the diversity of organisms are based on hereditary (genotypic) variability, and the prerequisites for positive evolution are created.
With non-hereditary (modification) variability, changes in the phenotype occur under the influence of environmental factors and are not associated with a change in the genotype. Modifications (changes in traits with modification variability) occur within the normal range of the reaction, which is under the control of the genotype. Modifications are not passed on to the next generations, i.e. characteristics acquired during an individual's life are not inherited. The value of modification variability lies in the fact that it ensures the adaptability of the organism to environmental factors during its life.
Individual development of organisms
All living organisms are characterized by the process of individual development - ontogenesis. Traditionally, ontogenesis is understood as the process of individual development of a multicellular organism (formed as a result of sexual reproduction) from the moment of formation of a zygote to the natural death of an individual. Due to the division of the zygote and subsequent generations of cells, a multicellular organism is formed, consisting of a huge number of different types of cells, various tissues and organs. The development of an organism is based on the "genetic program" (embedded in the genes of the chromosomes of the zygote) and is carried out in specific environmental conditions that significantly affect the process of implementing genetic information during the individual existence of an individual. In the early stages of individual development, intensive growth occurs (increase in mass and size), due to the reproduction of molecules, cells and other structures, and differentiation, i.e., the appearance of differences in structure and the complication of functions.
Obviously, the concept of "ontogeny" is applicable to unicellular organisms. It is also legitimate to talk about the individual development of unicellular and multicellular organisms resulting from asexual reproduction. Indeed, when dividing, for example, ciliates, daughter cells are formed, which differ significantly from the mother cell. They are smaller, devoid of a number of organelles that are formed only over time, in the process of the individual existence of daughter individuals. Having reached the “mature” state, the daughter organisms (in turn, having undergone division) will give rise to a new generation of ciliates. And although, with such a change of generations, there is no natural death of individuals, we can talk about their ontogeny (from division to division of these unicellular organisms). Another example is the asexual reproduction of multicellular organisms. For example, budding in hydra. Here, the process of ontogenesis unfolds from the moment the kidney appears on the mother's organism (and the separation of the daughter individual at a certain stage of its development) to the natural death of the daughter individual.
At all stages of ontogenesis, various environmental factors (temperature, gravity, pressure, food composition in terms of the content of chemical elements and vitamins, various physical and chemical agents) have a significant regulatory influence on the development of the organism. The study of the role of these factors in the process of individual development of animals and humans is of great practical importance, which increases with the intensification of anthropogenic impact on nature. IN various fields biology, medicine, veterinary medicine and other sciences, research is being widely conducted to study the processes of normal and pathological development of organisms, to elucidate the patterns of ontogenesis. IN recent decades formed an independent section of biomedical science - teratology. This direction is devoted to the study of deformities and malformations of organisms, the clarification of the causes of their appearance and the role of various environmental factors. Many of the identified teratogens (factors that cause deformities and malformations) turned out to be different chemicals with whom a person comes into frequent contact, Everyday life- nicotine, alcohol, various synthetic substances, some medications. Shown teratogenic effect and many physical factors - various type of radiation, ultrasound, vibration, electromagnetic field, etc.
The evolution of organisms
The evolution of organisms is an irreversible process of the historical development of living things. During evolution ( phylogenetic development) there is a successive change of species as a result of the process of the emergence of new species of organisms. By its nature, evolution is progressive, because the organization of living organisms in the course of evolution has gone through a number of stages - precellular forms, unicellular organisms, increasingly complex multicellular organisms up to humans (for more details, see the next section). With the advent of man, new form the existence of matter - social, higher than the biological and not reducible to it. Because of this, a person, unlike all other types of organisms, is a biosocial being (for more details, see Chapter 14).
Irritability
An integral property of organisms and all living systems is irritability - the ability to perceive external or internal stimuli (impact) and adequately respond to them. In organisms, irritability is accompanied by a complex of changes, expressed in shifts in metabolism, electrical potential on cell membranes, physicochemical parameters in the cytoplasm of cells, in motor reactions, and highly organized animals are characterized by changes in their behavior.
In animals that do not have nervous system, unicellular organisms and some cells of multicellular organisms (for example, blood phagocytes), reactions to irritation are expressed, in particular, in the form of motor reactions - taxis, spatial movements. Depending on the nature of the irritation, the following taxises are distinguished: phototaxis, chemotaxis, thermotaxis, geotaxis, etc. In photosynthetic organisms, positive phototaxis is usually pronounced (moving to the most illuminated zone), heterotrophic organisms are most often characterized by negative phototaxis (avoidance of illuminated zones) . Thanks to chemotaxis, blood phagocytes accumulate around, for example, bacteria that have entered the body and perform their function - phagocytosis ("devouring") of bacteria.
Plants are less mobile than animals. Most movements in plants arise as responses to irritation by light, temperature, gravity, and chemical factors. There are two types of active movements in plants: growth and contraction. The first movements are slower, and the second ones are faster. Growth movements are associated with the influence on the plant of a factor acting in one direction. This causes one-sided growth, and as a consequence, a bend occurs. Such bends of plant organs are called tropisms. Any tropism can be positive or negative. It is called positive when the plant bends towards the stimulus, and negative if the plant bends in the opposite direction from the stimulus. So, if you put the seedlings of a plant on a window, then the growing plants bend in one direction, towards the light. This phenomenon is called positive phototropism. The plant bends because it grows unevenly under these conditions. The side of the plant facing the light grows more slowly than the opposite side. Contractile movements in plants include the rapid movements of leaves in mimosa, oxalis, insectivorous plants (for example, sundew) when touched - nastia. In mimosa, petioles of pinnate leaves and individual leaves have special areas with special cells. When irritated (touched, pushed, shaken), cells quickly lose water, intracellular pressure drops sharply, and the leaves fold. Currently, it is suggested that the mechanism of rapid movements is also associated with the presence of special contractile proteins.
In multicellular animals, the nervous and muscular systems provide motor responses; forms of mediated reactive communication with the stimulus develop through higher nervous activity and consciousness. Due to irritability, balancing of organisms with the external environment is achieved: organisms adequately respond to changes in the conditions of their environment by changes in the functioning of the corresponding elements of the biological system and the system itself as a whole.
The phenomenon of irritability underlies the self-regulation of biological systems, and as a result of the existence of self-regulation, homeostasis is maintained in systems. homeostasis- this is the ability of the system to resist changes and maintain the relative constancy of its composition and properties (maintaining a certain body temperature, constancy full membership, osmotic pressure, etc.).
The phenomenon of irritability underlies adaptations. Adaptation (adaptation) is understood as the adaptation of an organism to continuously changing environmental conditions. Highlighting irritability as a specific property of living organisms, they are guided by the following considerations. Inanimate bodies (systems) react, as a rule, to external influences directly, that is, independently of its previous history. Living organisms react to external influences not only directly, but also based on their innate (genetic) or lifetime (individual) "memory" of all past experience of responding to external influences. Reasonable beings have the ability to act ahead in changing environmental conditions, reacting to external influences not only directly or taking into account the available and accumulated information, but actively processing it into essentially new information.
Concluding the section devoted to the analysis of the properties of living organisms, one can single out the fundamental and specific properties, the totality of which characterizes the living: self-renewal, self-reproduction and self-regulation, based on the flows of substances, energy and information. The difference between living systems and non-living ones is not in the presence of some elusive metaphysical properties - all the laws of physics and chemistry are also true for living things - but in the high structural and functional complexity of living systems. This feature includes all the features and properties of living organisms discussed above and makes the state of life a qualitatively new property of matter.
Questions for self-examination:
1. What fundamental properties distinguish living matter from non-living matter?
2. What is the substratum of life?
3. How can the phenomenon of life be defined?
4. What is metabolism and what role does it play in the dynamics of life?
5. What hierarchical levels of organization are specific for living matter?
Phenomenology of life
Structural hierarchy of living matter.
M.V. Wolkenstein proposed the following definition of life: "The living bodies that exist on Earth are open, self-regulating and self-reproducing systems built from biopolymers - proteins and nucleic acids." There is no strict and clear definition of the concept of "life", however, it is possible to list and describe those features of living matter that distinguish it from non-living matter.
1. certain chemical composition. The composition of living organisms includes the same chemical elements as in inanimate objects, but their ratio is different. The main nutrients are macronutrients H, C, O, N(98% of the mass of living organisms). In addition to them, important trace elements Na, Mg, Cl, P, S, Fe, Ca and others. In addition, all living organisms are built from 4 main groups of organic substances: nucleic acids, proteins, carbohydrates And lipids.
2. Cell structure. All living organisms have a certain organization, the structural and functional unit of which for all organisms (except viruses) is cell.
3. Metabolism and energy dependence. Organisms - open systems, which are stable only with continuous access to them by substances and energy from the outside. Wherein living system is constantly in a state of dynamic equilibrium.
4. Self-regulation. Living organisms have the ability to maintain the constancy of their chem. composition and intensity of metabolic processes.
5. Irritability- the ability of the body to respond to certain influences with specific reactions. The most striking form of manifestation of irritability is movement. In plants it tropisms, growth movements, in primitive animals - taxis. Multicellular reactions to irritation are carried out with the help of the nervous system and are called reflexes.
6. Heredity. Living organisms are characterized by the ability to transfer signs and properties unchanged from generation to generation with the help of DNA information carriers.
7. Variability- the ability of organisms to acquire new features and properties; creates a variety of material for natural selection.
8. reproduction- the ability of living beings to reproduce their own kind. Thanks to reproduction, the change and continuity of generations are carried out. Breeding types: asexual(carried out by non-sex, somatic cells) And sexual(carried out by sex cells).
asexual reproduction most widely distributed among prokaryotes, fungi and plants, but also found in various kinds animals. The main forms of asexual reproduction are fission, sporulation, budding, fragmentation, vegetative reproduction, and cloning ( clone - a genetic copy of one individual).
sexual reproduction characteristic of the vast majority of living organisms and is of great biological importance. The whole set of phenomena associated with sexual reproduction consists of 4 main processes: 1) gametogenesis- the formation of germ cells (gametes); 2) fertilization(syngamy - fusion of gametes and their nuclei) and the formation of a zygote; 3) embiogenesis(crushing of the zygote and formation of the embryo); 4) further growth and development of the organism in the post-embryonic (post-embryonic) period.
The biological significance of sexual reproduction lies not only in the self-reproduction of individuals, but also in ensuring the biological diversity of species, their adaptive capabilities and evolutionary prospects. This allows us to consider sexual reproduction biologically more progressive than asexual.
For some groups of organisms, irregular types of sexual reproduction are characteristic - parthenogenesis – development of an embryo from an unfertilized egg(bees, ants, termites, aphids, daphnia), it provides a rapid increase in the number of species.
9. Ontogenesis is individual development. A new organism arises in most cases as a result of the fusion of germ cells (gametes). In the process of growth and development, a specific organization of the individual gradually arises. The lifespan of individuals is limited by the aging process, which ultimately leads to death.
10. Phylogeny is evolutionary development. All living organisms exist not only in space, but also in time. Phylogeny is the irreversible and directed development of living nature, accompanied by the appearance of new species and the progressive complication of life.
11. integrity and discreteness. On the one hand, living matter is integral, organized in a certain way, and obeys a number of special, characteristic laws only for it. On the other hand, it is discrete (divisible), because any biol. The system consists of separate, though closely interconnected elements.
12. Negentrory. According to II law of thermodynamics all processes occurring spontaneously in isolated systems develop in the direction of decreasing order, i.e. an increase in entropy. At the same time, as living organisms grow and develop, on the contrary, they become more complex, which would seem to contradict the second law. In fact, this is an apparent contradiction. The fact is that living organisms are open systems. Organisms feed by absorbing energy from the outside, releasing it into environment heat and waste products finally die and decompose. According to the figurative expression of E. Schrödinger: “the organism feeds on negative entropy”; improving and becoming more complex, organisms bring chaos to the world around them.
In addition to those listed, sometimes physiological properties inherent in living things are distinguished - growth, development, excretion, etc.
The principle of discreteness formed the basis of ideas about the levels of organization of living matter.
Levels of organization of living matter
Organization level- the functional place of the biological structure of a certain degree of complexity. The following levels of organization of living matter are distinguished.
Molecular(molecular genetic) - includes the way of existence and self-reproduction of complex informational organic molecules, high-molecular organic compounds such as proteins, viruses, plasmids, nucleic acids, etc.
subcellular(supramolecular) - Live nature organized into organelles: chromosomes, cell membrane, endoplasmic reticulum, mitochondria, Golgi complex, lysosomes, ribosomes and other subcellular structures.
Cellular - living nature is represented by cells, i.e. elementary structural and functional unit of the living.
Organo-tissue- living nature is organized into tissues and organs. Textile- a set of cells similar in structure and function, as well as intercellular substances associated with them. Organ A part of a multicellular organism that performs a specific function or functions.
Organismic(ontogenetic) - living nature is represented by organisms. organism(individual, individual) is an indivisible unit of life, its real carrier, characterized by all its features.
population-species- living nature is organized in populations. population- a set of individuals of the same species that form a separate genetic system that exists for a long time in a certain part of the range relatively apart from other sets of the same species. View- a set of individuals (populations) capable of interbreeding with the formation of fertile offspring and occupying a certain area (range) in nature.
Biocenotic- living nature forms biocenoses- a set of populations of different species living in a certain area.
Biogeocenotic- wildlife forms biogeocenoses - a combination of biocenosis and abiotic environmental factors (climate, soil).
biospheric- living nature forms biosphere- the shell of the Earth, transformed by the activity of living organisms.
Predicting the properties of each next level based on the properties of previous levels is just as impossible as predicting the properties of water based on the properties of oxygen and hydrogen. This phenomenon is called " emergence”, i.e. the system has special, qualitatively new properties that are not inherent in the sum of the properties of its individual elements. On the other hand, knowledge of the features of the individual components of the system greatly facilitates its study.
1. Distinctive features of living matter.
1. Complex structure with a relatively small number of biomolecules (proteins, fats, carbohydrates, lipids, polysaccharides, nucleic acids)
2. A high level of structural and functional organization of biological objects with a strictly defined purpose of each component of a living organism.
3. The ability of a living organism to maintain vital activity through the exchange of matter and energy with the environment.
4. Self-regulation of biochemical reactions
5. Self-reproduction and transmission of hereditary information in every kind of living organisms
2. Biomolecules (simple and complex); biopolymers. Structural organization of the cell
Simple: α-amino acids, mononucleotides, monosaccharides, lipids, mononucleoproteins
Complex: proteins, polysaccharides, DNA, RNA (nucleic acids), polynucleotides.
Biopolymers-lipids, polysaccharides, nucleic acids (DNA, RNA), lipids, proteins.
Sugars have the general formula C(H 2 O) n, where P - integer (from 3 to 7), All sugars contain hydroxyl, as well as either aldehyde or ketone groups. Interacting with each other, monosaccharides can form di-, tri-, or oligosaccharides. Sugars are the main energy substrate of cells. In addition, they form bonds with proteins and lipids, and are also building blocks in the formation of more complex biological structures. The main reactive groups of sugars are hydroxyl groups involved, in particular, in the formation of bonds between monomers.
Fatty acids contain in their composition a carbohydrate chain and hydrophilic carboxyl groups that form amides and esters. Like carbohydrates, fatty acids are a source of energy for the body. But their main purpose is associated with participation in the formation of cell membranes. Free fatty acids are found at the lipid-water interface. However, in the body they are most often esterified or combined with other lipid structures. In the body of animals, the largest quantities of nacho-in are palmitic, oleic and stearic fatty acids. In plants, in addition to those listed, linoleic acid was also found in large quantities.
Amino acids found in biological tissues are mainly used to build protein macromolecules. Despite the differences in chemical structure, they contain amine and carboxyl groups connected to an asymmetric carbon atom. With help peptide bonds they form long polypeptide chains - the constituent parts of proteins.
Nucleotides are three-component structures consisting of nitrogenous bases and a phosphoric acid residue. Nitrogenous bases, in turn , They are divided into purine and pyrimidine, and sugar (pentose) - into ribose and deoxyribose.
Nucliotides are components of high-polymer nucleic acids - carriers of genetic information
To determine the role of a particular molecule in the processes of vital activity, it is necessary to know all the features of its structure. The stability of molecules is due to covalent bonds between the atoms that form it. The biological significance of molecules is determined, in particular, by their optical activity, this applies to molecules that have chiral centers. For example, the amino acids that form proteins have four different groups attached to one of the carbon atoms. As a result, amino acids acquire such a property as optical activity, which plays an important functional role. In addition to optical activity, the ability of molecules to adopt the most thermodynamically favorable conformation is very important. The chemical properties of molecules depend on whether it is flat or has a different shape, such as a curved one.
Nucleic acids - informational macromolecules consisting of iononucleotides. Cells contain deoxyribonucleic acid (DNA) and ribonucleic acids (RNA). DNA is the largest macromolecule in living systems. It consists of many thousands of pairs of nucleotides connected to each other in a certain sequence. RNA molecules are much smaller than DNA, but their total number exceeds DNA. For nucleic acids, a variety of functions is unusual, but the storage and transmission of genetic information is the basis for the reproduction and functioning of cells.
Proteins have many functions. They consist of amino acids connected in a genetically determined sequence, which determines both the structure and functions of these macromolecules. Thus, proteins are the instrument by which the genome controls all reactions of cellular metabolism.
Polysaccharides are macromolecular substances consisting of repeating structural units. They differ from each other in the structure of monosaccharide units, molecular weight, and glycosidic bonds. Thanks to the presence a large number polar groups, polysaccharides after swelling dissolve in water and form colloidal solutions. They are present in almost all cells and perform a variety of functions. Their role in the formation of biological structures is great. So, chitin forms the shells of arthropods, cellulose is the main structure of green plants, mucopolysaccharides are the most important components of connective tissue. Glycogen in animals and starch in plant organisms are the most important reserve polysaccharides. They are divided into homo- and heteropolysaccharides. An example of homopolysaccharides is starch, consisting of residues of only one type (glucose), and an example of heteropolysaccharides is hyaluronic acid, which consists of glucuronic acid residues alternating with N- acetylglucosamine.
Lipids are esters of higher fatty acids and glycerin. They include phosphoric acid, nitrogenous bases or carbohydrates. They play an essential role as structural components of the cell, as well as energy substrates. The physicochemical properties of lipids depend on their polarity. There are polar and neutral lipids. The latter consist of triacylglycerides and are included in the class of simple lipids. Polar lipids are multicomponent substances and are complex lipids.
Structural organization of the cell.
The cell is the basic structural element of living matter.
1. All living organisms consist of a certain number of cells, there are unicellular and multicellular microorganisms. Unicellular: streptococci, cholera bacilli, etc.
Multicellular: prokaryotes (without a nucleus), eukaryotes (with a formed nucleus)
2. Cell is the smallest structural and functional unit of living matter
3. Each cell of a living organism performs a strictly defined function
There are two large classes of cells that differ in structure and function. The most ancient and simple in structure are prokaryotic cells. The main properties characteristic of prokaryotes can be considered on the example of bacteria. These are one of the simplest cells in structure, distinguished by their small size and primitive structure. They do not have a nucleus and their genetic material is not protected by an additional intracellular membrane. As a rule, bacteria obtain the necessary energy from the environment, with glucose being its main source. A variety of bacteria are blue-green algae, or cyanobacteria, which have a photosystem similar to plant cells. Cyanobacteria can fix nitrogen carbon dioxide and release oxygen. Thus, their normal life activity can proceed in the presence of only water and air.
One of the most studied prokaryotic cells is Escherichia coli. Escherichia coli (E.coli), living in the gastrointestinal tract of many animals and humans
Like all prokaryotes, E.coli It has cell wall, to which the cell membrane adjoins on the inside,
| " |
Domestic scientists M. V. Volkenstein proposed the following definition of life: "Living bodies that exist on Earth are open, self-regulating and self-reproducing systems built from biopolymers - proteins and nucleic acids."
However, there is still no generally accepted definition of the concept of "life". But it is possible to distinguish signs (properties) of living matter, distinguish it from non-living.
1.certain chemical composition. Living organisms consist of the same chemical elements as objects of inanimate nature, but the ratio of these elements is different. The main elements of living things are carbon C, oxygen O, nitrogen N and hydrogen H.
2.Cell structure. All living organisms, except viruses, have a cellular structure.
3.Metabolism and energy dependence. Living organisms are open systems, they depend on the receipt of substances and energy from the external environment.
4.Self-regulation (homeostasis). Living organisms have the ability to maintain homeostasis - the constancy of their chemical composition and the intensity of metabolic processes.
5.Irritability. Living organisms show irritability, that is, the ability to respond to certain external influences with specific reactions.
6.Heredity. Living organisms are able to transfer signs and properties from generation to generation with the help of information carriers - DNA and RNA molecules.
7.Variability. Living organisms are capable of acquiring new features and properties.
8.Self-reproduction (reproduction). Living organisms are able to reproduce - to reproduce their own kind.
9.Individual development (ontogenesis). Each individual is characterized by ontogeny - the individual development of the organism from birth to the end of life (death or a new division). Development is accompanied by growth.
10.Evolutionary development (phylogenesis). Living matter as a whole is characterized by phylogenesis - historical development life on Earth from its inception to the present.
11.Adaptations. Living organisms are able to adapt, that is, adapt to environmental conditions.
12.Rhythm. Living organisms show the rhythm of life activity (daily, seasonal, etc.).
13.integrity and discreteness. On the one hand, all living matter is integral, organized in a certain way and obeys general laws; on the other hand, any biological system consists of separate, albeit interconnected, elements.
14.Hierarchy. Starting from biopolymers (proteins and nucleic acids) and ending with the biosphere as a whole, all living things are in a certain subordination. The functioning of biological systems at a less complex level makes possible the existence of a more complex level.
| Previous materials: |
