Diversity of life forms in nature. Diversity of life forms. The history of Darwin's theory of evolution
What miracles would be revealed to a person,
may his eyes be able to see
outlines and movements of the smallest
particles in blood and other fluids
organisms as clearly as
the outlines and movements of the living themselves
creatures
J. Locke
How are animal cells and plant cells different? What are the features of the organization and functioning of unicellular eukaryotes and cells as part of a multicellular organism? How are prokaryotic cells structured? What are viruses?
Lesson-lecture
DIFFERENCES IN THE STRUCTURE OF ANIMAL AND PLANT CELLS. The description of the general structure of a eukaryotic cell is mainly considered using the example of an animal cell. The organization of a plant cell has some specific features (Fig. 44). On the outside, it is covered with a cell wall, which consists of cellulose.
Rice. 44. Structure of a plant cell
The presence of a dense cell wall prevents the formation of a constriction during the division of the cell cytoplasm in the telophase of mitosis, as described in § 32. The division of the cytoplasm into two parts during mitosis of plant cells occurs through the formation of a plasma membrane and a cell wall directly inside the dividing cell - from the center to the periphery.
Plant cells contain special organelles - plastids. They are surrounded by at least two membranes, contain short circular DNA, ribosomes and are capable of independent division. Functionally, most varieties of plastids are in one way or another related to the energy of the cell. First of all, these are chloroplasts, in which photosynthesis reactions take place.
Chloroplasts contain chlorophyll, carotenoids and proteins necessary for photosynthesis. Chromoplasts do not contain chlorophyll, but are enriched with carotenoids - yellow, orange and red pigments that determine the color of flowers, fruits and some root vegetables (carrots). And finally, leucoplasts are colorless. Some of them can synthesize and accumulate starch, while others can store fat and protein. Under certain conditions, leucoplasts can transform into chloroplasts and chromoplasts, and chloroplasts into chromoplasts. The latter process is associated with the autumn change in leaf color.
Let us remember that cellulose is a polysaccharide, the molecules of which form the finest threads. Communication between neighboring cells in multicellular plants is carried out thanks to thin strands of cytoplasm that penetrate the non-compacted areas of the cell wall.
A typical plant cell has one or more central vacuoles, which, with strong development, can displace the rest of the cell contents to the periphery. Vacuoles are surrounded by a membrane, and their internal contents vary greatly in different cell types. These can be reserve nutrients (sugars, soluble proteins), solutions of salts necessary for the cell, amino acids, etc. Harmful products formed as a result of metabolism, for example, oxalic acid, are also excreted in the vacuole.
Pigments, anthocyanins, also accumulate in the vacuoles, which can give plants a wide range of shades - from pink to black-violet.
Anthocyanins provide blue and red coloring to fruits (plum, cherry, grapes, lingonberries, strawberries) and flower petals (cornflower, geranium, rose, peony). In addition, they are the ones that color autumn leaves bright red.
A plant cell has fundamentally the same structure as an animal cell. A distinctive feature of a plant cell is the presence of a cell wall, plastids and vacuoles.
CELL AS AN ORGANISM AND CELL AS COMPOSITION OF AN ORGANISM. You already know that a cell can function as an independent organism or be part of a multicellular organism or colony. In all these cases, the cells have specific features in their organization. Unicellular eukaryotes have organelles that they need for independent existence and which are never found in the cells of multicellular organisms. These can be pigment eyes, flagella and cilia, a cell mouth (a special section of the cytoplasm with which some predatory protozoa capture prey) and much more.
The main feature of the cells that form a multicellular organism is their specialization. This is especially clearly manifested at the tissue level of organization of higher plants and animals. The cells of each tissue are strictly differentiated, that is, they are adapted to perform one main function or a few functions, which determines their structural features. Moreover, such cells, as a rule, lose their ability to reproduce. They function for a certain time and then die. Most tissues contain some supply of undifferentiated cells capable of dividing. They produce new cells, which, after going through a certain stage of differentiation, replace the dead cells of a given tissue.
Cells of unicellular eukaryotes, in addition to the usual set of organelles, have a number of specific structures that ensure their existence as independent organisms. Within tissues, cells are adapted to perform certain functions. This specialization is irreversible, and the replenishment of tissues with new cells occurs as a result of division and subsequent specialization of undifferentiated cells.
SPECIFICITY OF PROKARYOTIC CELLS. A bacterial cell is fundamentally different from the cells of eukaryotic organisms we have considered. These differences do not relate to sizes, which for most bacteria are 1 - 10 microns. This is quite comparable to the size of some types of eukaryotic cells. But the structure and associated features of the functioning of the bacterial cell turn out to be completely different (Fig. 45).
Rice. 45. Structure of a bacterial cell
First of all, bacteria lack not only a formed nucleus, but also all other organelles. Differences are also found in the structure of the membrane surrounding the bacterial cell. Substances enter and leave the bacterium only through diffusion.
The supra-membrane structures of bacteria form a rigid cell wall around them. It has selective permeability. On top of the cell wall, the bacteria also form a mucous capsule, which serves as additional protection from adverse environmental factors, including protection from drying out. The cytoplasm of bacteria lacks a cytoskeleton.
Some bacteria are equipped with a flagellum, which has nothing in common either in structure or in functional features with the structure of the same name in eukaryotes.
Finally, the genetic apparatus of bacteria, the so-called nucleoid, is represented by a DNA molecule closed in a ring, which lies freely in the cytoplasm. The nucleoid is attached to the inside of the bacterial membrane. Before the bacteria begin to divide, the circular DNA is doubled, and the two resulting nucleoids “move apart” along the membrane in different directions. The membrane and cell wall then invaginate and lace the bacterial cell in two. Each of the resulting cells has its own nucleoid.
Prokaryotic cells lack a formed nucleus and cellular organelles. On the outside, the bacterium is surrounded by a dense cell wall and capsule; some species have a flagellum. The genetic apparatus of prokaryotes is represented by a circular DNA molecule, the replication of which precedes the division of the bacterium.
NON-CELLULAR LIFE FORM - VIRUSES. The existence of viruses was first learned in 1892, when the Russian botanist D.I. Ivanovsky discovered that a disease of tobacco - tobacco mosaic - is caused by a pathogen passing through bacterial filters, i.e. it is significantly smaller in size than bacteria. Indeed, the sizes of most viruses vary between 15-300 nm. In the simplest case, the virus consists of a small DNA or RNA molecule surrounded by a protective protein shell - capsid(Fig. 46).
Rice. 46. Structure of the tobacco mosaic virus: a - RNA; b - capsid
The virus can exist for a long time and under a wide range of external conditions. However, viruses cannot reproduce themselves on their own, since they do not contain those structures and enzymes that provide processes associated with the replication of nucleic acids and protein biosynthesis. Therefore, the main task of the virus is to enter the host cell. This process can occur accidentally, for example with liquid during pinocytosis. However, most viruses are able to recognize precisely those cells in which they can reproduce.
Once in the host cell, the viral DNA begins to replicate.
Information is also read from it in the form of mRNA, which is sent to ribosomes, where viral proteins are synthesized. In the case of RNA viruses, the viral RNA replicates many times and itself plays the role of mRNA. As the capsid proteins and nucleic acids of the virus accumulate in the cytoplasm of the host cell, viral particles are assembled. Their accumulation leads to the death of the host cell, it ruptures, and viral particles are released into the external environment.
However, the sequence of events following the entry of the virus into the host cell may be different. It turned out that under certain circumstances, the DNA of the virus does not begin replication in the cytoplasm of the host cell, but is integrated into its circular DNA (in bacteria) or into the DNA of chromosomes (in eukaryotes). Such a cell with viral DNA in its genome is capable of multiplying, and viral DNA also enters each daughter cell. Then, under some external influence (ultraviolet or radiation), the viral DNA leaves the genome of the host cell and begins to produce viral particles according to the scheme described above.
The ability of DNA viruses to integrate into the genome of a cell has a number of serious consequences. The fact is that when viral DNA leaves a chromosome or nucleoid, it can also capture adjacent sections (genes) of the host DNA. Then, together with the viral DNA, these sections can be integrated into the genome of the cells of another individual (or even an individual of another species), into which the virus will penetrate. This “horizontal” transfer of genetic material (as opposed to the “vertical” transfer from parents to children) plays an important role in the evolution of organisms.
Viral DNA and RNA can carry oncogenes- genes that, when inserted into the genome of a cell, transform it into cancer. In addition, the integration of the genetic material of the virus into the DNA of a cell can provoke the activation of some of its own genes (proto-oncogenes), which also leads to cell degeneration and tumor formation.
A virus is a DNA or RNA molecule surrounded by a protein shell. Viruses can only reproduce in host cells. Viral DNA can integrate into the host genome, which can lead to the phenomenon of horizontal transfer of genetic information.
Many viruses and bacteria die when exposed to ultraviolet radiation. During epidemics caused by viruses, it is useful to quartz the room. In the absence of appropriate equipment, it is necessary to regularly ventilate the room and do wet cleaning.
- Explain the differences in the structure of plant and animal cells.
- Why is the rate of bacterial cell division higher than the rate of eukaryotic cell division? What is the role of viruses in the biosphere?
- Why did eukaryotic cells, rather than prokaryotic cells, become dominant in the process of evolution and give rise to a huge variety of life forms?
Diversity of life forms. Systematics is a science that studies the diversity of living organisms and issues of their classification. Classification is the distribution of living organisms into groups according to their degree of relatedness. Units of classification (systematic units) are called taxa.
Systematic units (taxa) in zoology and botany. Zoology Botany Species Species Genus Genus Family Family Order Order Class Class Type Division Kingdom Kingdom In addition, additional systematic units are often used, such as: subkingdom, superfamily, and non-systemic classification units, for example, division or section.
Diversity of life forms. The highest ranking taxon is Kingdom. There are 5 kingdoms: Viruses, Bacteria, Fungi, Plants, Animals.
Diversity of life forms. Viruses are non-cellular life forms. All they have is a nucleic acid molecule and a protein shell. Representatives of the other 4 kingdoms have a typical cellular structure. Among them, a distinction is made between the superkingdom of Eukaryotes (plants, animals and fungi) and the superkingdom of Prokaryotes (bacteria).
1. There is a formed core; 2. There are numerous organelles in the cytoplasm; 3. Chromosomes are linear and numerous; 4. Relatively large cells (100 times or more). 1. there is no nucleus, the DNA-containing zone is called a nucleoid; 2. there are no membrane organelles. Only ribosomes are present. 3. One ring chromosome. 4. The cells are small.
Living environments There are 4 living environments: Ground-air (aerobionts, or terrabionts), Aquatic (hydrobionts), Soil (edaphobionts), Organismic (endobionts).
Structural levels of life organization. There are several levels of organization of living things: 1. molecular genetic; 2. cellular; 3. organismal, 4. population-species. 5. biogeocenotic. 6. biosphere. Each of these levels is called a biosystem. A biosystem is a form of life organization characterized by the presence of interconnected components.
Structural levels of life organization. Level Basic processes Structural unit of the biosystem Molecular-genetic Metabolism of substances and energy; storage and transmission of hereditary information atoms Cellular All processes inherent in the cell Biopolymers - molecules of complex organic substances - BZhU, NC Organismal Regulated interaction of all organ systems Organs and their systems Population-species Elementary evolutionary transformations are carried out Individual individuals of the species
Structural levels of life organization. Level Basic processes Structural unit of the biosystem Biogeo-cenotic Partial circulation of substances and energy between the components of the biosystem Populations of different species Biosphere Planetary circulation of substances and energy Biogeocenoses of the planet
Definitions of concepts Population is a group of individuals of one species geographically distant from other groups of the same species. A species is a group of individuals similar in structure and life processes, which freely interbreed with each other and produce fertile offspring. Biogeocenosis is a collection of organisms of different species living in a certain territory and interconnected with each other and their habitat by the flow of substances and energy. The biosphere is the area of distribution of living organisms, covering the inhabited part of all the earth’s shells (atmosphere, hydrosphere, lithosphere), the totality of all biogeocenoses of the planet.
Let us remember that cellulose is a polysaccharide, the molecules of which form the finest threads. Communication between neighboring cells in multicellular plants is carried out thanks to thin strands of cytoplasm that penetrate the non-compacted areas of the cell wall.
The presence of a dense cell wall prevents the formation of a constriction during the division of the cell cytoplasm in the telophase of mitosis, as described in § 35. The division of the cytoplasm into two parts during mitosis of plant cells occurs through the formation of a plasma membrane and a cell wall directly inside the dividing cell - from the center to the periphery.
Plant cells contain special organelles - plastids. Like mitochondria, they are surrounded by at least two membranes, contain short circular DNA, ribosomes, and are capable of independent division. Functionally, most varieties of plastids are in one way or another related to the energy of the cell. First of all, these are chloroplasts, in which photosynthesis reactions take place.
Chloroplasts contain chlorophyll, carotenoids and proteins necessary for photosynthesis. Chromoplasts do not contain chlorophyll, but are enriched with carotenoids - yellow, orange and red pigments that determine the color of flowers, fruits and some roots (carrots). And finally, leucoplasts are colorless. Some of them can synthesize and accumulate starch, while others store fat and protein. Leucoplasts, under certain conditions, can transform into chloroplasts and chromoplasts, and chloroplasts into chromoplasts. The latter process is associated with the autumn change in leaf color.
A typical plant cell has one or several central vacuoles, which, when strongly developed, can displace the rest of the cell contents to the periphery. Vacuoles are surrounded by a membrane, and their internal contents vary greatly in different cell types. These can be reserve nutrients (sugars, soluble proteins), solutions of salts necessary for the cell, amino acids, etc. Harmful products formed as a result of metabolism, for example, oxalic acid, are also excreted in the vacuole.
Pigments, anthocyanins, also accumulate in the vacuoles. Unlike carotenoids, they can give plants a wider range of shades - from pink to black-violet. Anthocyanins provide the red and blue color of fruits (plum, cherry, grapes, lingonberries, strawberries) and flower petals (cornflower, geranium, rose, peony). In addition, they are the ones that color autumn leaves bright red. In autumn, the synthesis of chlorophyll in the leaves stops. Anthocyanins are formed in them mainly in cold sunny weather. Therefore, the brightest color of the leaves is in the cold and clear autumn. In warmer and more humid weather, the color of autumn leaves is largely determined by carotenoids and the dominant tone is yellow.
A plant cell has fundamentally the same structure as an animal cell. A distinctive feature of a plant cell is the presence of a cell wall, plastids and vacuoles.
The main feature of the cells that form a multicellular organism is their specialization. This is especially clearly manifested at the tissue level of organization of higher plants and animals. The cells of each tissue are clearly differentiated, that is, they are adapted to perform one main function or a few functions, which determines their structural features. Moreover, the differentiated cells that make up the tissues of plants and animals, as a rule, lose their ability to reproduce. They function for a certain time and then die. Most tissues contain some supply of undifferentiated cells capable of dividing. They produce new cells, which, after going through a certain stage of differentiation, replace the dead cells of a given tissue.
Cells of unicellular eukaryotes, in addition to the usual set of organelles, have a number of specific structures that ensure their existence as independent organisms. Within tissues, cells are differentiated to perform specific functions. This specialization is irreversible and the replenishment of tissues with new cells occurs as a result of division and subsequent specialization of undifferentiated cells.
Specificity of a prokaryotic cell. A bacterial cell is fundamentally different from the cells of eukaryotic organisms we have considered. These differences do not relate to sizes, which for most bacteria are 1–10 microns. This is quite comparable to the size of some types of eukaryotic cells. But the structure and associated features of the functioning of the bacterial cell turn out to be completely different.
First of all, bacteria lack not only a formed nucleus, but also all other cellular compartments - the basis for the structural and functional organization of eukaryotic cells. Differences are even found in the structure of the membrane surrounding the bacterial cell. Substances enter and leave the bacterium only through diffusion.
The supra-membrane structures of bacteria form a rigid cell wall around them. It has selective permeability; the nutrients necessary for bacteria pass through the cell wall and the final products of metabolism are excreted. Bacteria also form a mucous layer on top of the cell wall. capsule, which serves as additional protection from adverse environmental factors, including protection from drying out.
Bacterial ribosomes have a slightly different protein composition than ribosomes of eukaryotic cells. There are also differences in ribosomal RNAs. An important distinguishing feature of the bacterial cytoplasm is the absence of a cytoskeleton in it.
Some bacteria are equipped with a flagellum, which has nothing in common either in structure or in functional features with the structure of the same name in eukaryotes (for more details, see § 00).
Finally, the genetic apparatus of bacteria, the so-called nucleoid, is represented by a DNA molecule closed in a ring, which lies freely in the cytoplasm. The nucleoid is attached to the inside of the bacterial membrane. Before the bacteria begin to divide, circular DNA replication occurs and the two resulting nucleoids “move apart” along the membrane in different directions. The membrane and cell wall then invaginate and lace the bacterial cell in two. Each of the resulting cells has its own nucleoid.
Prokaryotic cells lack a formed nucleus and cellular compartments. Their genetic apparatus (nucleoid) is represented by a circular DNA molecule, which lies freely in the cytoplasm and is attached by one of its sections to the inner side of the membrane surrounding the bacterium.
Non-cellular form of life – viruses. The existence of viruses was first learned in 1892, when the Russian botanist D.I. Ivanovsky discovered that the disease of tobacco, the so-called tobacco mosaic, is caused by a pathogen passing through bacterial filters, i.e. it is significantly smaller in size than bacteria. Indeed, the sizes of most viruses vary between 15 and 300 nm. In the simplest case, the virus consists of a small molecule of DNA (DNA-containing viruses) or RNA (RNA-containing viruses), surrounded by a protective protein shell - the capsid.
A viral particle can exist for a long time and under a wide range of external conditions. However, viruses cannot reproduce themselves on their own, since they do not contain those structures and enzymes that provide processes associated with the replication of nucleic acids and protein biosynthesis. The nucleotide sequence of DNA or RNA viruses encodes only information about capsid proteins and several (not all!) enzymes necessary for the replication of viral nucleic acid.
Therefore, the main task of the virus is to enter the host cell. This process can occur accidentally, for example, with liquid during pinocytosis. However, most viruses are able to recognize precisely those cells in which they are able to reproduce.
A different route of penetration is typical for bacterial viruses – bacteriophages. We have already noted in the previous section of this paragraph that bacteria are not capable of either phagocytosis or pinocytosis. Therefore, the path into the bacterial cell inside the membrane vesicle is closed for bacteriophages. The bacteriophage capsid is designed like a kind of syringe that pierces the cell wall and membrane of bacteria and injects its DNA or RNA inside.
A virus is a DNA or RNA molecule surrounded by a protein shell. Viruses can only reproduce in cells, where they use existing cellular systems to synthesize their own proteins and replicate their DNA or RNA. Viral DNA can integrate into the host genome, which can lead to the phenomenon of horizontal transfer of genetic information. When comparing cellular and non-cellular forms of life, you were convinced that in Nature there are no structures that are not required for the functioning of the biosphere. The stability of the biophere is based on the diversity of life forms.
Biology teacher: Kasatkina Marina Aleksandrovna.
GBOU KK boarding school for gifted children named after. V.G. Zakharchenko.
Topic: “The variety of forms of living organisms.”
Item: Biology.
Class : 9.
Basic tutorial : Ponomareva I.N., Chernova N.M., Kornilova O.A. Biology 9th grade (VENTANA-GRAF).
Lesson Objectives :
generalize and consolidate students’ knowledge about the diversity of forms of living organisms;
determine the biological significance of all kingdoms of living nature for the preservation of the biosphere;
to form a cognitive interest in the study of living nature;
to form in students an idea of the unity of the world and the value of life in all its manifestations
Tasks :
- educational
repeat and consolidate the concepts of the kingdom of living nature;
to formulate the importance of biological diversity for the conservation of the biosphere;
Withto form a cognitive interest in the study of living nature;
- developing : creating conditions for the development of thinking techniques (analysis, synthesis, systematization, generalization, ability to draw conclusions); the ability to argue one’s position (communicative competence); ability to work with a source of biological information; ability to solve a problem situation;
- educational: creating conditions for nurturing activity and independence, confidence in the knowability of the world.
Lesson type
: learning new material.
Form of organization of educational activities
:
collective
Teaching methods
: verbal, visual.
Design and equipment: textbook, computer, multimedia projector, presentation “Levels of Life Organization”, educational complex 1C: School. Biology, 9th grade.
During the classes:
Organizing time.
Setting lesson goals and objectives, organizing students.
Checking homework.
What properties are common to all living organisms?
What are the main chemical elements of living things?
Define "life".
Updating basic knowledge.
Teacher:
What kingdoms of living nature do you know?
Students:
Plants, Animals, Fungi, Bacteria.
Learning new material:
1.Kingdoms of living nature.
A diagram appears on the screen.
Teacher:
Which kingdom is missing from the diagram?
Students
: Kingdom of Viruses.
2. Life forms.
Teacher:What types of life are there?
Students: Cellular and non-cellular.
3.Ecological groups of organisms.
Teacher
: Name the environment of life. What organisms inhabit them?
Students
: aquatic, terrestrial, soil and organismal.
A table appears on the screen.
4. Levels of organization of living matter.
Teacher
: We have examined with you the kingdoms of living nature; living environment of organisms.
And now I suggest you watch the presentation Levels of Life Organization.
Level - this is the functional place of a biological structure of a certain degree of complexity in the general hierarchy of living things.
Molecular genetic level
represented by individual biopolymers (DNA, RNA, proteins, lipids, carbohydrates and other compounds);
At this level of life, phenomena related to changes (mutations) and reproduction of genetic material and metabolism are studied.
Subcellular- represented by organelles: EPS, AG, ribosomes, etc.
Cellular
- the level at which life exists in the form of a cell - the structural and functional unit of life.
At this level, processes such as metabolism and energy, information exchange, reproduction, photosynthesis, nerve impulse transmission and many others are studied.
Organ
-
tissue
-
represented by tissues and organs;
-textile
- a set of cells similar in structure and function, connected by an intercellular substance;
-organ
- part of a multicellular organism that performs a specific function.
Organismal
- this is the independent existence of an individual - a unicellular or multicellular organism;
organism
- an indivisible unit of life, its real carrier, characterized by all its characteristics;
biosystem- living system.
Population-species
– level, which is represented by a group of individuals of the same species – a population; It is in the population that elementary evolutionary processes occur - the accumulation, manifestation and selection of mutations;
-population
- a collection of individuals of one species that form a separate genetic system that exists for a long time in a certain part of the range, relatively separately from other individuals of the species;
-view
- a set of individuals (populations of individuals) capable of interbreeding to form fertile offspring and occupying a certain area.
Biocenotic
- represented by biocenoses
-biocenosis
is a collection of populations of different species living in a certain territory.
Biogeocenotic
– represented by ecosystems consisting of different populations and their habitats;
-biogeocenosis
- a set of biocenoses and abiotic environmental factors (climate, soil).
Biosphere – a level representing the totality of all biogeocenoses. In the biosphere there is a circulation of substances and the transformation of energy with the participation of organisms. The waste products of organisms participate in the process of evolution of the Earth.
IV
.Reinforcement.
Teacher:
1.Which kingdom do cyanobacteria belong to? What life form is this?
2. Yeast and tinder fungus are representatives of which kingdom? What form of life are they?
3. What standard of living include:
- taiga forest
- a flock of sheep
- common amoeba
- chloroplast.
VI
.Summing up the lesson.
VII
.Homework.
Paragraph 3, questions at the end of the paragraph.
Life on Earth... The richness of its forms is amazing! Go out to the forest lawn in summer. Among the green grasses and flowers, grasshoppers chirp and ants scurry around. Squirrels are jumping along the branches of trees, a lark is pouring into the blue sky... Life has penetrated both the depths of the ocean and the Arctic Circle, climbed to the tops of the highest mountains and even higher - into the rarefied layers of the atmosphere, where many types of microorganisms are found.
Have life forms always been the way we see them today, or have they come a long way over the centuries? - this is the question that arises in everyone who sees such a variety of living beings.
Since ancient times, people have answered it in different ways. According to the biblical book of Genesis, on the third day God created the plant world: “the grass that sows seed, the fruitful tree that bears fruit according to its kind, in which is its seed on the earth.” On the fifth day, “God created the great fish and every living creature that moves, which the waters brought forth, according to their kinds, and every winged bird according to its kind.” On the sixth day He created “the beasts of the earth according to their kinds, and the cattle according to their kinds, and every creeping thing that creeps on the earth according to their kinds” (Gen. 1:11,21, 25).
The extreme complexity of the structure and the observed expediency of the behavior of living organisms led many to the opinion that life is more than just a physical and chemical phenomenon. Living beings, compared to objects of inanimate nature, have a number of distinctive properties, thanks to which a very specific goal is achieved. In this regard, since ancient times, an idea has arisen: although living beings are material, living matter is apparently “animated” by a certain immaterial factor. This point of view was and is held by many people of different religious and philosophical beliefs. This point of view underlies vitalism - currents in biology that recognize the presence in organisms of an immaterial supernatural force (“vital force”, “soul”, etc.) that controls life phenomena.
The results of modern experiments show that the fundamental laws of nature - the laws of conservation of mass and energy - are fulfilled in living systems within the limits of experimental accuracy. When sugars, fats or proteins are oxidized in the body, the same amount of energy is released as when they are converted in the laboratory, and in this sense, the human or animal body is similar to a non-living chemical system. At the same time, it is clear that if there is a certain “vital force” inherent only in living matter, then by its nature it is not capable of violating the fundamental laws - the laws of conservation of mass and energy. A stronger statement can also be stated: numerous experiments show that in biological systems not a single law of physics and chemistry is violated. However, it is too early to conclude from this statement that living systems obey only the laws of physics and chemistry.
When characterizing the differences between living and inanimate matter, in addition to the already mentioned expediency, one should also mention the meaningfulness of the actions of living systems. Meaning cannot exist in the form of a completely disembodied “spirit.” It disappears if it is not embodied in some material system, including, for example, a very specific configuration of nerve connections in the brain. At the same time, the meaning may not depend on the specific physical system of its implementation. For example, the meaning of the same slogan coming from a person does not depend on the technical means of its reproduction.
So, with a very great degree of caution we can say: living things are a material system endowed with the property of purposefulness. Of course, this statement does not pretend to be a complete, exhaustive definition of living systems, and, of course, with the development of natural science and science in general, it will certainly be specified, supplemented and, therefore, modified.
Since ancient times, there has been an idea about gradual modification living forms. This the idea was quite clearly expressed by the ancient Greek philosopher Empedocles, who lived in the 5th century. BC e. And yet, for many centuries, the idea of the immutability of the forms of the organic world remained dominant, and the reason for this, most likely, is that man, in the apt expression of Charles Darwin (1809-1882), looked at the organic world “as a savage looks at ship, that is, as something beyond his understanding.”
The birth of the evolutionary idea
What strikes us when we get acquainted with the structure of any living organism? First of all, its expediency. The potter rotates the potter's wheel by rhythmically pressing the pedal; before our eyes, his skillful fingers transform a shapeless piece of clay into an elegant jug. The vessel is designed for a specific purpose - to store water, and its entire structure is such as to perform this task in the best possible way. Let's take a closer look at it: the bottom is wide - so that the jug is stable and does not tip over from the first push; and its neck is narrow - to reduce heating and evaporation of moisture. Only the very top of the neck is widened in the form of a funnel - otherwise it would be difficult to pour water into the jug. If a jug is made by a true craftsman, it is beautiful and at the same time useful, we call it a perfect creation. What does a person think when he gets acquainted with the purposeful organization of a living organism? Let's take any wading bird, for example a heron. She has long bare legs, which allows her to walk in shallow water while remaining dry. The long beak makes it possible to extract food from under the water. A swimming bird (ducks, geese) has short legs, equipped with swimming membranes: it has special glands that secrete fat and make the plumage waterproof. And when a person became acquainted with all this, the question involuntarily arose: who created the birds so successfully adapted to life in a swamp or lake? Of course not people. Means? This means that this was created by another, more powerful creator!
And yet daring minds could not come to terms with such an explanation, the French naturalist of the 18th century. J. Buffon was inclined to think about the gradual improvement of living organisms, and his follower J.-B. Lamarck (1744-1829) first tried to create a slender theory of the evolution of life on Earth. Lamarck considered the main factor of evolution to be the exercise of some organs and the passivity of others under the influence of living conditions. If an organ is exercised, Lamarck reasoned, it gradually strengthens, and if it is not exercised, it weakens and dies. At first glance, everything is clear here. Compare a gymnast with a person who does not play sports. In the first, the muscles are elastic and elastic, they play under the skin. The second one has flabby muscles and a fair layer of fat under the skin. And if we ask the question how the gymnast achieved such a state, then everyone can answer it without much difficulty: through exercise!
However, our question will not seem so simple if we turn to the children of these people. Of course, they can follow in the footsteps of their fathers, then the differences between them will be the same. Well, what if both of them start playing sports at the same time under the guidance of the same coach and with equal diligence? Can we say that in this case, the gymnast’s children will definitely achieve better sports results than their comrades? In general, this question can be formulated as follows: are the characteristics that parents developed in the course of life through exercise or as a result of adaptation to external conditions transmitted to children? Lamarck answered this question: they are transmitted! If we return to our example with wading and swimming birds, then, according to Lamarck, their ancestors, who were no different from ordinary birds, having found themselves, due to circumstances, in special conditions, for example, in a swamp, began to intensively exercise their legs, which began to lengthen and gradually reached the length of the legs of a modern heron. Other birds, forced to live and feed on lakes and rivers, tried to swim, quickly spreading and joining their fingers. This caused the skin at the base of the fingers to stretch, and as a result, after many generations, swimming membranes were formed.
Lamarck's assumption about the development and improvement of existing organs did not answer such an important question at all: what are the reasons for the appearance of completely new organs? Indeed, what kind of “exercise” can explain the appearance of horns in some animals? To find a way out of this situation, Lamarck endowed living beings with a special property - “the desire for improvement.” The entire organic world, the French scientist believed, is constantly changing and improving on its own thanks to the inherent desire for progress in living organisms.
Lamarck's views, which he outlined in 1809, did not find recognition among his contemporaries. The views of his compatriot J. Cuvier (1769-1832) were much more popular. While Lamarck was thinking about the reasons for the purposefulness of living organisms, Cuvier chose this purposefulness as the main instrument of research. He proceeded from the fact that all organs in the body are interdependent and correlated. Let's take a herbivore. Plant foods have little nutritional value and require large quantities to meet the body's needs. This means that the stomach of a herbivore must be large. The size of the stomach determines the size of other internal organs: the spine, the chest. The massive body can stand on powerful legs equipped with hard hooves, and the length of the legs determines the length of the neck so that the animal can freely pluck the grass. His teeth should be wide, flat, with a large abrasive surface.
Predators are a different matter. Their food is more nutritious, which means their stomach may be small. The predator needs soft paws with movable clawed fingers to quietly sneak up on prey and grab it. A predator's neck should be short, its teeth sharp, etc.
Cuvier brought his method to such perfection that he was often able to restore the appearance of an entire animal from one found tooth. If he had a skeleton or at least part of it, then success was guaranteed. Thus Cuvier discovered a whole world of fossil animals. Giant lizards that once lived on Earth, mammoths and mastodons - if we are now well aware of them, the credit for this belongs primarily to Georges Cuvier. With his discoveries, the scientist made a huge contribution to the future evolutionary theory, but he himself did not suspect it.
While studying extinct animals, Cuvier discovered that the remains of some species are confined to the same geological strata and are not found in neighboring strata, which are characterized by completely different organisms. From this he concluded that the animals that once inhabited our planet died almost instantly from some unknown reasons, and later in their place new ones appeared that had nothing in common with their predecessors. In addition, according to Cuvier, many of the current land areas were once the seabed, and the sea advanced and retreated here several times. At the same time, sedimentary rocks, which should usually be located horizontally, often turned out to be broken, crushed into giant folds. All these facts forced Cuvier to assume that gigantic catastrophes occurred on Earth from time to time, destroying entire continents, and with them all their inhabitants. Later, new organisms appeared in their place. Strange as this theory of catastrophes sounds now, at the beginning of the 19th century. she looked quite convincing.
At a time when Cuvier’s theory was considered absolutely reliable, the Englishman Charles Lyell (1797-1875) began geological research. He, more intuitively than consciously, immediately sensed the arbitrary nature of the catastrophe theory. Traveling a lot, he paid special attention to the geological processes that constantly occur around us. To understand the Earth's past, it is necessary to study its present - this is what became the basic principle of Charles Lyell's scientific research. Observing sediments in river deltas, the activity of wind, sea tides, studying the formation of shoals, volcanic craters, Lyell became convinced that slow, insignificant changes on Earth can even today lead to the most amazing results if they continue long enough and in one direction. Lyell studied especially carefully the sediments of the Tertiary era, which immediately precedes ours in the history of the development of the Earth. He noted that many organisms that lived then are found on Earth now. At the same time, new species were born and old ones lived out their lives. Such conclusions fundamentally undermined Cuvier's theory. Lyell himself did not claim that some species descend from others - such a thought did not occur to him. But, having proven the slow, gradual nature of geological changes, he created another a prerequisite for the development of the evolutionary idea.
7.9. Evolution of life
The history of Darwin's theory of evolution
In 1831, setting off on a voyage around the world, the young Englishman Charles Darwin took with him the just published first volume of Lyell’s Principles of Geology, and five years later he brought back from his voyage a huge amount of materials confirming the correctness of his fundamental idea. But that's not all: Darwin also brought something more - the conviction that living species are changeable, that the animal and plant kingdom as we know it today is the result of a gradual, very long development of a complex organic world.
Charles Darwin began to study the problem of evolution closely in 1836 after returning from a trip around the world on the Beagle ship. He discussed it with few of his colleagues, including in correspondence. Therefore, it seemed to many that he was completely immersed in the study and classification of barnacles and was acting as secretary of the Geological Society. Colleagues advised him to publish his hypothesis, but he did not follow their advice. And then on June 14, 1858, Darwin received a letter from Alfred Russel Wallace (1823-1913) from Ternate in the Moluccas. The letter contained an article that Wallace asked to convey to Sir Charles Lyell, a famous geologist and friend of Darwin. It briefly outlined the essence of the theory of evolution by natural selection.
Wallace published the assumption that species can change in one of his works earlier - in 1855. This idea was developed after he read in 1858 the work of the English scientist Thomas Malthus (1766-1834) “An Essay on the Law of Population.” Malthus believed that each population strives to multiply as much as possible without taking into account the means of subsistence, and when it reaches a certain maximum size, depending on living conditions, poverty begins to hinder further growth: the excess population must die. This can happen tragically and suddenly, or as a result of increasing mortality as the limit of possible growth is approached. Malthus did not specifically address the question of who would live and who would die. Wallace's guess was that it would not be a random sample from the population that would survive, but the individuals that were better adapted to the conditions of existence. If their fitness is above the average level for the entire population and it is at least partially inherited, then the species as a whole will change in the direction of greater fitness, that is, higher adaptation to the environment. Interestingly, Darwin came to the same conclusions after reading the work of Malthus.
Wallace, then a little-known naturalist, was collecting tropical insects. However, given the current situation, his message could not be ignored. After consulting with his friends, primarily C. Lyell and Joseph Hooker (1817-1911), a famous botanist, Darwin decided that it was necessary to combine excerpts from a letter that he had recently sent to the American botanist A. Greso, a summary of an unpublished article written as early as 1844, and a report by Wallace. All this was formalized in the form of a report presented on July 1, 1858 to the Linnean Society. Darwin's book On the Origin of Species was published in November 1859, and all 1,250 copies of it were sold out on the first day.
The great interest in the idea of natural selection was not at all due to the fact that Darwin and Wallace postulated the transformation of some species into others, that is, the very fact of evolution. Many people spoke about this before, and above all Lamarck in France, Erasmus Darwin - the grandfather of Charles Darwin, and, finally, Anaximander in Ancient Greece. The interest was determined mainly by the fact that a mechanism was proposed for the “construction” of living beings without the participation of the Creator. This mechanism quite suited the opponents of the statement: if something is created, then there must be a Creator.
The idea of evolution by natural selection made it possible to combine many seemingly unrelated facts. Both Darwin and Wallace were able to draw on a wealth of material from paleontology, biogeography, and other sciences that pointed to natural selection as the most likely driving force behind evolution.
Some prominent scientists, Darwin's contemporaries, nevertheless remained very active anti-evolutionists. These included the English zoologist R. Owen (1804-1892), the Swiss naturalist L. Agassiz (1807-1873), who worked for a long time at Harvard. Even the great geologist Charles Lyell did not immediately believe in the theory of evolution. Based on paleontological data, they recognized the emergence of new species, but believed that this was the result of some still unclear natural processes, and not the gradual transformation of one species into another. At the same time, Darwin's ideas were supported by T. Huxley (1825-1895) in England, E. Haeckel (1834-1919) in Germany, K.A. Timiryazev (1843-1920) in Russia.
For those who demanded complete convincing from the theory of evolution, there remained one serious insurmountable difficulty associated with the nature of heredity. At that time, neither Wallace, nor Darwin, nor many other scientists yet knew the laws of inheritance of traits. True, it was known that sometimes signs may not appear in all generations in a row. This mysterious phenomenon, later named atavism, consists in the fact that the descendants suddenly again exhibit signs of more or less distant ancestors. It was believed, however, that heredity in general is based on the principle of mixing, with the exception of individual cases. For example, a plant could have either white or red flowers. With the mixing mechanism, the hybrid should have pink flowers, and when crossing a red flower with a pink flower, the flowers should be dark pink, etc. In many cases, this happens. An important conclusion followed from this: a new trait that appeared in an individual as a mutation must disappear over time, dissolve in the population, despite natural selection, like a glass of milk in many barrels of water.
Analyzing the mechanism of averaging of traits, the British engineer and physicist F. Jenkin, possessing a mathematical mind, in 1867, based on strict elementary arithmetic calculations, proved that in the case of averaging of traits during crossing, natural selection will not work. Darwin never found a convincing answer to such evidence. The intermediate manifestation of traits in descendants meant that all genetic differences in populations should quickly be leveled out, and then the entire population would become homogeneous, consisting of very similar individuals.
This objection to the theory of evolution was removed by the results of crossing experiments conducted by the Austrian naturalist Gregor Mendel (1822-1884). It all started with Gregor Mendel, a monk from the Augustinian monastery in Brunn (now the city of Brno in the Czech Republic, at that time in Austria-Hungary), in 1850, i.e. long before Darwin and Wallace introduced report on evolution, tried to get a certificate to teach science, but could not pass the exam. Wanting to prepare for the test, he entered the university in Vienna, where he studied mathematics, biology, chemistry and physics for four semesters. He then returned to Brünn and began growing peas in his garden. Experiments carried out on peas helped to establish the nature of heredity with apparent ease and grace. Namely, in 1868, Gregor Mendel, in experiments with crossing peas, showed that heredity does not have, as was then believed, an intermediate nature - traits are transmitted by discrete particles, which today are called genes.
In diploid organisms, i.e. organisms with two homologous sets of chromosomes, which include both peas and humans, two genes correspond to each trait. They can be either exact copies or variants (alleles) of each other. From each parent, the offspring receives one such gene. Genes are contained in small bodies - chromosomes, located in the cell nucleus.
Mendel's work was written with exceptional clarity and from a scientific point of view represented a real masterpiece, but for a long time remained unclaimed. Only in 1900 did three unknown researchers simultaneously confirm their results with their experiments.
One more similar example can be given. In 1902, London physician A. Gerrod showed that the action of at least some genes is to control the activity of enzymes. This work also went unnoticed. The idea that genes contain information for building a protein (one gene - one enzyme) was established only after 1945. The examples given and the history of the development of the theory of evolution show how complex and time-consuming the path to comprehend natural scientific truth is.
Russian botanist S.I. Korzhinsky (1861-1900) and independently the Dutch scientist Hugo De Vries (1848-1935) proposed mutation theory - sudden changes in heredity. This theory, shedding light on the process of variability, confirmed Darwin's teaching. The sharper the mutation, the larger the jump, the less chance there is for the new form of the organism to survive under these conditions. Another thing is that the mutations are small. Most often, they are also harmful to the body, but in rare cases, a small change can be beneficial. The organism improves, turns out to be better adapted than its unchanged relatives, and natural selection consolidates the new form. Thus, the mutation theory built a bridge between Mendelian laws of heredity and Darwinism.
At the same time, the theory of mutations has given rise to new problems related, in particular, to the causes of mutational changes. In fact, why do some individuals of a given species change, while others living in the same conditions do not? Not seeing any external reasons that would cause these changes, many scientists were inclined to believe that mutations were spontaneous, that is, spontaneous. But in 1927, a short note by the American geneticist G. Meller appeared. He irradiated Drosophila fruit flies with X-rays and obtained an unprecedented outbreak of variability. It was soon proven that mutations can be caused not only by X-rays, but also by other types of radiation, as well as by many chemical compounds, sudden changes in temperature, etc.
This is one direction of research, determined by the results of Mendel's experiments. Another, no less important direction, related to elucidating the nature of the gene itself, developed under the leadership of the American geneticist T.G. Morgan (1866-1945). By now, many questions about the nature of the gene and genetic information have already been clarified.
Artificial and natural selection
Solving the main question of the driving forces of development, Darwin came to the point at which Lamarck had previously stopped. However, unlike Lamarck, Darwin decisively excluded the mysterious “striving for improvement” from consideration, turning his attention to human activity.
In fact, do we not underestimate ourselves too much when we say that we are not capable of creating new forms of organic life? What about ours? cultivated plants and domestic animals - aren't they created by man? Let's focus on wheat. Once upon a time a man threw a handful of grains of a nondescript wild animal into the ground. The grains were small, and the ears fell off at the slightest breath of wind. It was not easy for the first farmer to harvest! Thousands of years of first unconscious and then conscious selection of the best specimens led to the fact that the grain became full-bodied and the ear did not fall off. And humans have given dozens of other properties to wheat: they have increased the amount of protein in the grain, made it resistant to many diseases, developed varieties that are responsive to fertilizers, non-lodging, and early ripening... Now cultivated wheat occupies over 200 million hectares on the globe, but if you stop take care of it, then in a few years not a single grain of cultivated cereal will be found. Left to its own devices, cultivated wheat will die! The same can be said about almost any cultivated species of plants or animals.
And if so, then we should take a closer look at the methods by which man created new varieties of plants and breeds of livestock. Darwin often met with pastoralists and asked how they created and maintained their herds. And the answer was almost always the same: “We leave the best animals for the tribe.”
That's all! The casket opened surprisingly simply. Cattle breeders did not suspect that by slaughtering weak and low-productive animals (those with low milk yield if they are cows, with worse wool if they are sheep; those with weak strength if they are horses intended for transporting goods, and not fast-footed enough if they are racehorses), they carried out enormous creative work. Artificial selection - This is what Darwin called this method. Through artificial selection, man has created forms that did not previously exist in the wild (Fig. 7.10). Darwin decided to see if something similar was happening among wild animals.
It has long been clear to man that food resources for any species of animal (or plant) in a certain area are limited. What about the ability to reproduce? It has no boundaries! The numbers here are as simple as they are astounding. If from all the eggs laid by one bird the chicks hatched, grew up and gave birth to offspring themselves, and the offspring of this offspring were also preserved in full and continued like this for, say, 15 years, then the total number of descendants of one pair would reach ten million!
However, this almost never happens. The number of birds, animals, and plants remains unchanged (or changes within small limits, both upward and downward), often for many centuries. This means that not all eggs hatch into chicks, not all chicks become adult birds, and, finally, not all adults leave offspring. Who is lucky, who gets a lucky lot? Obviously, those who manage to capture the required amount of food are protected from enemies - in a word, those who manage to win the struggle for existence.
Thus, those better adapted to life in environmental conditions win the struggle for existence. For example, some trees in the forest are oppressed: they do not have enough space in the sun (Fig. 7.11), and if this is the case, then in nature, as on a livestock farm, selection also occurs. However, it is no longer man who selects here, but nature itself. It is the conditions of the natural environment that lead to the selection of the most adapted - natural selection, as Darwin called it. This explains the expediency of organic forms! The structure of an animal or plant is not expedient because someone adapted this organism for a specific purpose, but because out of all the diversity of forms, individuals that were better adapted to the given conditions survived and could leave offspring! 
Two young Russian scientists, A.O. Kovalevsky (1840-1901) and I.I. Mechnikov (1845-1916), adopting evolutionary theory, began to create a new science - comparative evolutionary embryology (embryo - Greek embryo). At the same time, Kovalevsky discovered transitional forms between vertebrates and invertebrates, thereby filling the most important gap in the general system of development of the animal kingdom.
Goal-directed behavior and natural selection
Man-made devices and machines (for example, a guided missile, a personal computer) prove that non-living systems are also capable of purposeful action. However, to create them, a designer who is aware of the goal is required. In this regard, the question arises: wasn’t this kind of constructor needed when creating a living system? One of the possible answers to this eternal question is contained in the idea of Darwin and Wallace, the essence of which is that living beings can improve themselves (evolve) towards greater adaptation, that is, adaptability to their environment. Both scientists suggested the presence of a mechanism of natural selection. Living beings are capable of changing (mutating) randomly, and such mutations are inherited. If mutations turn out to be useful for survival, then their proportion in subsequent generations will increase. As a result, populations evolve towards greater adaptation to the environment.
For the formation of, for example, such complex organs as the eye, many coordinated mutations are required. Their simultaneous occurrence is unlikely, so it is natural to assume that evolution proceeds through the accumulation of small shifts.
All intermediate stages in the evolution of an organ must be functionally useful and lead to its gradual improvement. Even given all sorts of constraints, natural selection can produce surprisingly complex structures. The assumption that a particular structure serves a specific purpose has proven very fruitful for experimental biology.
The importance of purposeful action can be illustrated by the example of constructing a self-reproducing machine. The idea of such a design was first proposed by the famous mathematician von Neumann. He showed that it is logically quite possible to build a universal machine that, according to the instructions given to it, is capable of creating any other machine of a given design. Such a machine can also be programmed to reproduce itself.
Such machines must include three interconnected functional parts:
A - a working mechanism that ensures the physical construction of the machine (in engineering terms, this is a program-controlled line);
I - instructions (commands) recorded on a storage medium that set an algorithm of actions for the working bodies (a storage medium containing the information necessary for constructing A);
IN - device for copying instructions.
In general, this system can be represented in the form
S = A+ B+ I.
Such a self-reproducing machine perfectly models a living organism, for which A is the body, I is genes, IN - a mechanism for copying genes to pass them on to the next generation. This machine can be programmed not only for playback, but also for other functions. In biological language, this means that such machines are capable of mutating and undergoing evolution, that is, their descendants will differ from their ancestors. If self-reproducing machines change randomly, this will not lead to their directed evolution. In order for an oyster to appear as a self-reproducing organism, complex organs must be formed: gills, intestines, etc., as well as purposeful behavior, etc., which taken together seems simply incredible.
One of the features of natural selection is that mutations, favorable or unfavorable for the organism, arise randomly. A change in any adaptive trait is the result of a single mutation: once it occurs, it falls under natural selection. However, one very serious objection can be raised against such a view, which can be conveniently illustrated using the example of the evolution of the eye. The probability of the simultaneous occurrence of a number of mutations leading to the formation of the retina (layer of light-sensitive cells), lens, etc., is negligible. To imagine that such simultaneous changes could occur as a result of random mutations is like throwing a complete set of watch parts into a box, shaking them and expecting them to fold themselves into a whole watch. If the mutations do not occur simultaneously and as a result at least one component of the eye is missing, such an eye will be useless and selection for all other mutations will be impossible.
Complex biological structures can be created by natural selection if, in principle, they can be achieved through constant complication, so that each new stage provides some new advantage. Since natural selection does not have the gift of foresight, it sometimes cannot promote the emergence of some intermediate structure that does not immediately bring a certain benefit, even if this structure could prove useful in the distant future.
Some adaptations are quite sophisticated and seem as if they would not have been possible without foresight and ingenuity. Therefore, many find it difficult to believe that this happened through a simple accumulation of individual changes for the better. It may be possible to believe, but then a completely logical question arises: how does such a concept differ from the one in which the role of the Creator is defended? After all, both ideas in this case are based on faith. In addition, there are adaptations in nature that cannot be explained by natural selection. For example, the physical and chemical properties of substances and fundamental constants seem to be specially selected so that life can arise. This statement is sometimes called environmental fitness. There is another formulation: if If the fundamental constants were just a little different, life would be impossible. This principle, extended to the development of the Universe, is called fine tuning of the Universe.
Geological eras and the evolution of life
Under the influence of evolutionary theory, geologists had to reconsider their ideas about the history of our planet. The organic world developed over billions of years along with the environment in which it had to exist, that is, together with the Earth. Therefore, the evolution of life cannot be understood without the evolution of the Earth, and vice versa. Brother A.O. Kovalevsky Vladimir Kovalevsky (1842-1883) based evolutionary theory paleontology - science of fossil organisms.
Geologists discover the first traces of organic remains in the most ancient sediments dating back to Proterozoic geological era, covering a huge period of time - 700 million years. The earth at that time was almost completely covered by ocean. It was inhabited by bacteria, protozoan algae, and primitive marine animals. Evolution then proceeded so slowly that tens of millions of years passed before the organic world changed any noticeably (Fig. 7.12). 
IN Paleozoic era(lasting about 365 million years), the evolution of all living things proceeded at a faster pace. Large expanses of land were formed, on which land plants appeared. Ferns developed especially rapidly: they formed gigantic dense forests. Marine animals also improved, which led to the formation of huge armored fish. In the Carboniferous (Carboniferous) period, which marked the heyday of the Paleozoic fauna and flora, amphibians already appeared. And in the Permian period, which ended the Paleozoic era and began the Mesozoic (it is 185 million years removed from us), there were reptiles.
Even faster, the animal and plant world of the Earth began to develop in Mesozoic era. Already at its very beginning, reptiles began to dominate the land. The first mammals, marsupials, also appeared. Coniferous trees became widespread, and a variety of birds and mammals arose.
About 70 million years ago came Cenozoic era. Species of mammals and birds continued to improve. In the plant world, the dominant role has passed to flowering plants. The species of animals and plants that live on Earth today were formed.
With the emergence of man about 2 million years ago, the current period of the Cenozoic era begins - the Quaternary, or anthropogen. Man - on a geological scale of time - is a perfect baby. What is 2 million years for nature! This is an extremely short period of time. The most significant event in the Cenozoic era was the emergence of a large number of cultivated plants and domestic animals. All of them are the result of the creative activity of man - a rational being capable of purposeful activity.
If Darwin, while developing the theory of evolution, studied the experience of breeders, then, armed with scientific theory, breeders learned to develop new varieties much faster and more purposefully. Here a special role belongs to the Russian scientist N.I. Vavilov (1887-1943), who developed the doctrine of the origin of cultivated plants. The evolution of living things continues, but under the influence of man.
We now know that the expediency of organic forms is not something given in advance, but the result of a long and complex process of development of matter, and, therefore, the expediency of organic forms is relative. Man is now actively changing living nature. Increasing human intervention in natural processes gives rise to new serious problems that can be solved only on the condition that man himself takes care of the surrounding nature and the preservation of those subtle relationships in biosphere, which have developed in it over millions of years of the evolution of life on Earth.
The doctrine of the biosphere was created by the remarkable scientist V.I. Vernadsky (1863-1945). By the biosphere, the scientist understood that thin shell of the Earth in which all processes take place under the direct influence of living organisms. The biosphere unites the upper shells of the Earth - the lithosphere, hydrosphere and atmosphere - and plays a crucial role in the exchange of substances between them. Huge amounts of oxygen, carbon, nitrogen, hydrogen and many other elements constantly pass through living organisms on Earth. V.I. Vernadsky showed that there is practically not a single element in the periodic table that would not be included in the living matter of the planet and would not be released from it during its decay. Therefore, the face of the Earth as a celestial body is actually shaped by life. Vernadsky was the first to show what a decisive geological role living matter played on our planet.
Vernadsky also focused on the enormous geological role of man. He showed that the future of the biosphere is noosphere, that is, the sphere of reason. The scientist believed in the power of the human mind, believed that, by increasingly interfering with natural evolutionary processes, man would be able to direct the evolution of living things in such a way as to make our planet even more beautiful and richer.
