STAGES OF EARLY EVOLUTION:

Coacervates (emergence of precellular life forms)

Prokaryotic cells (the emergence of life, cellular life forms - anaerobic heterotrophs)

Chemosynthetic bacteria (appearance of chemosynthesis)

Photosynthetic bacteria (the appearance of photosynthesis, in the future this will lead to the emergence of an ozone screen, which will allow organisms to reach land)

Aerobic bacteria (the appearance of oxygen respiration)

Eukaryotic cells (emergence of eukaryotes)

Multicellular organisms

- (emergence of organisms on land)

STAGES OF PLANT EVOLUTION:

- (the appearance of photosynthesis in prokaryotes)

Unicellular algae

Multicellular algae

Riniophytes, Psilophytes (plant emergence on land, cell differentiation and the appearance of tissues)

Mosses (emergence of leaves and stem)

Ferns, Horsetails, Plaunas (emergence of roots)

Angiosperms (flower and fruit emergence)

STAGES OF ANIMAL EVOLUTION:

The simplest

Intestinal (appearance of multicellularity)

Flatworms (occurrence of bilateral symmetry)

Round worms

Annelids (body segmentation)

Arthropods (the appearance of the chitinous cover)

Skullless (notochord formation, ancestors of vertebrates)

Pisces (origin of the brain in vertebrates)

Cis-fin fish

Stegocephaly (transitional forms between fish and amphibians)

Amphibians (the emergence of the lungs and five-toed limbs)

Reptiles

Oviparous mammals (the emergence of the four-chambered heart)

Placental mammals

ADDITIONAL INFORMATION:
OBJECTIVES OF PART 2:

Tasks

1. Establish the sequence of evolutionary processes on Earth in chronological order
1) the emergence of organisms on land
2) the occurrence of photosynthesis
3) the formation of the ozone screen
4) the formation of coacervates in water
5) the emergence of cellular life forms

Answer

2. Establish the sequence of evolutionary processes on Earth in chronological order
1) the emergence of prokaryotic cells
2) the formation of coacervates in water
3) the emergence of eukaryotic cells
4) the emergence of organisms on land
5) the emergence of multicellular organisms

Answer

3. Establish a sequence that reflects the stages of evolution of protobionts. Write down the corresponding sequence of numbers.
1) anaerobic heterotrophs
2) aerobes
3) multicellular organisms
4) unicellular eukaryotes
5) phototrophs
6) chemotrophs

Answer

4. Establish the sequence of the emergence of groups of organisms in the evolution of the organic world of the Earth in chronological order. Write down the corresponding sequence of numbers.
1) heterotrophic prnocaryotes
2) multicellular organisms
3) aerobic organisms
4) phototrophic organisms

Answer

Establish the sequence of the formation of aromorphoses in the evolution of chordates
1) the emergence of the lungs
2) the formation of the brain and spinal cord
3) chord formation
4) the emergence of a four-chambered heart

Answer

Arrange the organs of animals in the order of their evolutionary origin. Write down the corresponding sequence of numbers.
1) swim bladder
2) chord
3) three-chambered heart
4) uterus
5) spinal cord

Answer

Establish the sequence of the appearance of aromorphoses in the process of evolution of vertebrates on Earth in chronological order. Write down the corresponding sequence of numbers
1) reproduction by eggs, covered with dense shells
2) the formation of ground-type limbs
3) the appearance of a two-chambered heart
4) the development of the embryo in the uterus
5) feeding with milk

Answer

Establish the sequence of formation of aromorphoses in the evolution of invertebrates
1) the emergence of bilateral symmetry of the body
2) the emergence of multicellularity
3) the emergence of articulated limbs covered with chitin
4) dismemberment of the body into many segments

Answer

Establish the correct sequence for the appearance of the main groups of animals on Earth. Write down the numbers under which they are indicated.
1) Arthropods
2) annelids
3) Skullless
4) flatworms
5) Intestinal

Answer

Establish the sequence in which the types of invertebrates should be placed, taking into account their complexity nervous system in evolution
1) flatworms
2) Arthropods
3) Intestinal
4) annelids

Answer

Establish the sequence of complication of the organization of these animals in the process of evolution
1) earthworm
2) common amoeba
3) white planarian
4) may beetle
5) nematode
6) crayfish

Answer

Establish the sequence of the processes occurring during the evolution of plants on Earth, in chronological order. Write down the corresponding sequence of numbers in the answer.
1) the emergence of a eukaryotic photosynthetic cell
2) a clear division of the body into roots, stems, leaves
3) landfall
4) the emergence of multicellular forms

Answer

1) green algae
2) horsetail
3) seed ferns
4) rhinophytes
5) gymnosperms

Answer

Establish the chronological order in which the main groups of plants appeared on Earth
1) Psilophytes
2) Gymnosperms
3) seed ferns
4) unicellular algae
5) Multicellular algae

Answer

Establish the sequence of the taxonomic position of the plants, starting with the smallest category. Write down the corresponding sequence of numbers.
1) psilophytes
2) unicellular algae
3) multicellular algae
4) gymnosperms
5) fern
6) angiosperms

Answer

Establish the sequence in which the development of the plant world on Earth took place
1) the emergence and dominance of angiosperms
2) the appearance of algae
3) the emergence and dominance of gymnosperms
4) the emergence of plants on land
5) the emergence and dominance of ferns

Answer

Establish the sequence of aromorphoses in the evolution of plants, which led to the emergence of more highly organized forms
1) cell differentiation and the appearance of tissues
2) the appearance of the seed
3) the formation of a flower and a fruit
4) the appearance of photosynthesis
5) the formation of the root system and leaves

Answer

Establish the correct sequence for the emergence of the most important aromorphoses in plants. Write down the corresponding sequence of numbers.
1) the emergence of multicellularity
2) the appearance of roots and rhizomes
3) tissue development
4) seed formation
5) the occurrence of photosynthesis
6) the occurrence of double fertilization

Answer

Arrange the plants in a sequence that reflects the complexity of their organization during the evolution of the taxonomic groups to which they belong.
1) Chlamydomonas
2) Psilophyte
3) Scots pine
4) bracken fern
5) Chamomile officinalis
6) Kelp

Answer

Establish the correct sequence of the most important aromorphoses in plants. Write down the numbers under which they are indicated.
1) Photosynthesis
2) Seed formation
3) The emergence of vegetative organs
4) The emergence of a flower in a fetus
5) The emergence of multicellularity

Rice. 52. Possible way of formation of eukaryotic organisms

Currently, living organisms arise only as a result of reproduction. Spontaneous generation of life in modern conditions impossible for several reasons. Firstly, in the conditions of the Earth's oxygen atmosphere, organic compounds are rapidly destroyed, therefore, they cannot accumulate and improve. And secondly, at present there are a huge number of heterotrophic organisms that use any accumulation of organic matter for their nutrition.
Review questions and assignments
What cosmic factors in the early stages of the Earth's development were the prerequisites for the emergence of organic compounds? Name the main stages of the emergence of life according to the theory of biopoiesis. How were coacervates formed, what properties did they possess and in what direction did they evolve? How did the probionts come about? Describe how the complication of the internal structure of the first heterotrophs could have occurred. Why is the spontaneous generation of life impossible in modern conditions?
Think! Execute! Explain why the origin of life from substances of inorganic nature is impossible on our planet at the present time. Why do you think the sea became the primary environment for the development of life? Take part in the discussion "The Origin of Life on Earth." Express your point of view on this issue.
Work with computer
Please refer to the electronic attachment. Study the material and complete the assignments.


Eukaryotes, eubacteria and archaea. Comparing the sequences of nucleotides in ribosomal RNA (rRNA), scientists came to the conclusion that all living organisms on our planet can be divided into three groups: eukaryotes, eubacteria and archaea. The last two groups are prokaryotic organisms. In 1990 Karl Woese - American explorer, who built a phylogenetic tree of all living organisms on the basis of rRNA, proposed the term “domains” for these three groups.
Since the genetic code in organisms of all three domains is the same, it was hypothesized that they have a common ancestor. This hypothetical ancestor was called "progenote", that is, the progenitor. It is believed that eubacteria and archaea could have originated from a progenote, and the modern type of eukaryotic cell, apparently, arose as a result of the symbiosis of the ancient eukaryote with eubacteria.

The first living organisms arose in the Archean era. They were heterotrophs and used organic compounds of the "primary broth" as food. The first the inhabitants of our planet were anaerobic bacteria... The most important stage in the evolution of life on Earth is associated with the emergence of photosynthesis, which determines the division of the organic world into plant and animal. The first photosynthetic organisms were prokaryotic (prenuclear) cyanobacteria and blue-green algae. The eukaryotic green algae that appeared then released free oxygen from the ocean into the atmosphere, which contributed to the emergence of bacteria that can live in an oxygen environment. At the same time - on the border of the Archean Proterozoic era, two more major evolutionary events occurred - appeared reproductive process and multicellularity.

To understand more clearly the meaning of the last two aromorphoses, let us dwell on them in more detail. Haploid organisms (microorganisms, blue-green) have one set of chromosomes. Each new mutation immediately manifests itself in their phenotype. If the mutation is useful, it is preserved by selection; if it is harmful, it is eliminated by selection. Haploid organisms constantly adapt to their environment, but they do not develop fundamentally new signs and properties. The sexual process dramatically increases the ability to adapt to environmental conditions, due to the creation of countless combinations in chromosomes. Diploid, which arose simultaneously with the formed nucleus, makes it possible to preserve mutations in a heterozygous state and use them as reserve of hereditary variability for further evolutionary transformations. In addition, in a heterozygous state, many mutations often increase the viability of individuals and, therefore, increase their chances of fighting for survival.

The emergence of diploidy and genetic diversity of unicellular eukaryotes, on the one hand, caused the heterogeneity of the structure of cells and their association in colonies, on the other hand, the possibility of "division of labor" between the cells of the colony, i.e. the formation of multicellular organisms. The division of cell functions in the first colonial multicellular organisms led to the formation of primary tissues - ectoderm and endoderm, which later made it possible for the emergence of complex organs and organ systems. Improving the interaction between cells, first contact, and then with the help of the nervous and endocrine systems ensured the existence of a multicellular

organism as a whole.

The paths of evolutionary transformations of the first multicellular organisms were different. Some have moved to a sedentary lifestyle and morphed into organisms such as sponges... Others began to crawl with their cilia. From them flatworms originated. Still others retained a floating lifestyle, acquired a mouth and gave rise to coelenterates.

3.History of the Earth, since the appearance on it organic life and before the appearance of a person on it, it is divided into three large periods - eras, sharply differing from one another, and bearing names: Paleozoic - ancient life, Mesozoic - middle, Neozoic - new life.

Of these, the largest in time is the Paleozoic, it is sometimes divided into two parts: the early Paleozoic and the late, since the astronomical, geological, climatic and floristic conditions of the late differ sharply from the early. The first includes: the Cambrian, Silurian and Devonian periods, the second - the Carboniferous and Permian.

There was an Archean era before the Paleozoic, but then there was still no life. The first life on Earth is algae and plants in general. The first algae originated in water: this is how modern science sees the emergence of the first organic life, and only later do mollusks that feed on algae appear.

Algae transform into terrestrial grass, giant grasses transform into paleozoic herbaceous trees.

In the Devonian period, lush vegetation appears on Earth, and life in the water in the form of its small representatives: protozoa, trilobites, etc. Warm climate - all over the globe for there is still no modern sky with its sun, moon and stars; everything was covered with a thick, poorly permeable, powerful fog of water vapor, still surrounding the earth in colossal quantities, and only a part settled in the water basins of the oceans. The Earth rushes in cold world space, but then she was dressed in a warm, impenetrable shell. Due to the greenhouse (greenhouse) effect, the entire early Paleozoic, including even the Carboniferous period, has warm-water flora and fauna all over the earth: both on Svalbard and in Antarctica - everywhere there are deposits of coal, which is a product of the tropical forest, everywhere there was warm-water marine fauna. Then the rays of the sun did not penetrate directly to the ground, but were refracted at a certain angle through the vapors and illuminated it then differently than now: the night was not so dark and not so long, and the day was not so bright. The day was shorter than the current day. There was neither winter nor summer, there are no astronomical and geophysical reasons for this yet. Coal deposits consist of trees without growth rings, their structure is tubular, like that of grass, rather than annular. So there were no seasons. There were no climatic zones either, due to the greenhouse effect.

Modern paleontology has already sufficiently studied all types of living organisms of the Cambrian period: about a thousand different species of molluscs, but there is reason to believe that the first vegetation and even the first mollusks appeared at the end of the Archean era.

In the next, Silurian period, the number of mollusks increases to 10,000 species, and in the Devonian period, lungfish appear, that is, fish that do not have a backbone, but are covered with shells, as a transitional form from mollusks to fish. They breathed with both gills and lungs. They try to become land dwellers, but they don't have to do it. The transition from sea to land will be performed by amphibians, from the class of vertebrates such as amphibian dinosaurs.

The first representative of the lizards - Archaeosaurus - appears at the end of the Paleozoic, it develops at the beginning of the Mesozoic era, in the Triassic period.

Distinctive properties of the Paleozoic: light was not separated from darkness, an intermediate state, an intermediate between light and darkness, between day and night, partially extended until the beginning of the Carboniferous. There were no stars in the sky. There were no seasons and climatic zones.

Proof: the absence of annual rings on the trees of the Paleozoic, except for the last, Permian period, when they first appear, the disappearance of all herbaceous trees with a tubular trunk structure since that time; the spread of tropical vegetation over the entire surface of the earth, including the poles; the same thermophilic fauna throughout the earth; the formation of huge amounts of coal deposits, as a result of the death of herbaceous forests, not adapted to the direct rays of the sun and naturally charred and killed by ultraviolet radiation and solar radiation, just as grass is charred in a hot summer during a drought.

Since the Permian period, there are climatic zones and the distribution of late flora and fauna, differently adapted to climatic zones.

The next period in the life of the Earth corresponds to the entire Mesozoic era, that is, the periods: Triassic, Jurassic and Cretaceous. This was the heyday of the animal kingdom. The most varied and bizarre forms of reptiles inhabited the Earth. They were both in the seas and on land and in the air. It should be noted that the entire class of insects appeared at the end of the Paleozoic, and they were many times larger than their modern descendants.

The first birds appear in the Jurassic period. They multiplied not only quantitatively, but also in a variety of species. One species of birds gave birth to chicks with their own characteristics, which gave rise to a new species of birds, which, in turn, produced chicks that were not quite similar to them. This is how the diverse world of living beings developed. At some moments there were absolutely amazing metamorphoses.

Paleontologists know many specimens of different stages in the development of birds and not a single intermediate species between them: these are pterodactyls, Archeopteryx and completely developed birds.

Pterodactyls are half birds, half reptiles. This is a lizard, in which toes have developed strongly and films have appeared between them, like a bat. But the next generation, which retained the same long spine, on either side of which feathers grew, is sharply different from its predecessors. The body and wings were covered with feathers, but there were claws on the wings for clinging to branches.

The head of Archeopteryx is the face of a beast inherited from a pterodactyl, with sharp large teeth and soft lips. And only in the next generation the vertebral tail disappears and the head becomes the head of a bird with a beak.

The last era is coming - the Neozoic. It includes the Tertiary and Ice Age (Quaternary) periods. Man appears towards the end of the Ice Age. It was in the Neozoic era that mammals appeared. This is almost the modern world of animals. The fauna of that time can be seen to some extent in Africa, which was not touched by a glacier.

The biggest question for many is the question of monkeys. Most scientists are inclined to believe that the monkey can in no way be the predecessor of man; but some say there must be some common ancestor. But this common ancestor has not yet been found.

Geochronological table of the Earth

The very first organisms

Breeds archaea and early Proterozoic have come down to us in a highly altered state. High pressures and temperatures have transformed the original appearance of the rock, destroying all traces of ancient life. Therefore, the study of the most ancient flora and fauna is associated with enormous difficulties. However, over the past century, with the help of instruments, it was possible to clarify something in the appearance the very first organisms on Earth.

Studying with electron microscope, chemical and isotopic analyzes, shales of the Onverwacht Formation (Rhodesia), whose age is more than 3.2 billion years, scientists at the University of Arizona (USA) found thousands of tiny spherical, filamentous and shell-like formations in them. The particle size did not exceed 0.01 mm. The studies were carried out in a specially equipped laboratory, which excluded the possibility of contamination of samples by foreign organisms. Scientists believe that the formations found are the fossilized remains of unicellular algae. However, other researchers are critical of their findings, believing that these formations may be of non-biological origin.

Similar remains of algae and bacteria in rocks with an absolute age of 2.7-3.1 billion years are found in siliceous and ferruginous shales of North America, Central Africa and Australia. These findings suggest that by the beginning of the Archean era chemical evolution ended and biological evolution began.

Based on the findings, it can be assumed that already in the oceans Archean and Early Proterozoic ages protozoa dominated unicellular organisms: bacteria, algae, fungi, protozoa. In the Archean, the first organisms adapt to various forms of nutrition. Some organisms assimilated in the process of photosynthesis nutrients from water, carbon dioxide and inorganic salts (autotrophic); others lived either on autotrophs (heterotrophic), or fed on decaying organic remains (saprophages). There was a division of the organic world into the kingdom of plants and the kingdom of animals.

In the early Proterozoic, apparently, the first multicellular organisms appeared. These are the most primitive forms without clearly differentiated tissues. These include, in particular, a representative of the type of sponges - aquatic organisms leading a near-bottom attached lifestyle. The shape of the sponges is varied, it can resemble a cylinder, cup, glass, ball. The soft tissue of an animal contains an organic or mineral skeleton consisting of spicules. Representatives of sponges still inhabit the seas and oceans of our planet, but the first primitive sponges died out long ago and have come down to us only in a fossil state.

Somewhat later, representatives of the type of coelenterates appear. They are already showing differentiation of tissues and organs. Representatives of coelenterates, as well as sponges, have survived to this day and have widely settled in the seas, oceans and even in fresh water bodies, Among them are corals, jellyfish, and hydras that are well known to us.

From plants in the Archean and early Proterozoic actively developing blue-green algae... The remains of these algae in the form of spherical, mushroom and columnar calcareous bodies, characterized by thin concentric stratification, are often found in the rocks of the Proterozoic. It is believed that the first representatives of organic life on Earth were precisely blue-green algae ... Experiments carried out at Moscow State University in the last century have shown that they can exist under conditions that are "contraindicated" to other plants and animals. These algae have lived in a hermetically sealed glass bowl for over 16 years! All other inhabitants of such glass balls quickly died, some bacteria "lasted" for 12 years, only blue-green survived. This proves that they can develop even in an oxygen-free environment.

The amazing adaptability of these algae is evident from the fact that they are now found in the icy Arctic, in hot geysers, at the bottom of the Dead Sea, in oil springs, in the mountains at an altitude of more than 5000 meters. These are the only living organisms that have withstood the explosions of atomic and hydrogen bombs... They are found even inside nuclear reactors. This amazing vitality has allowed some scientists to speculate about an unearthly origin. blue-green algae... Be that as it may, but these are the first organisms that appeared not only in the ancient oceans, but also on land.

A study by the American professor E. Barghorn showed that blue-green algae they were the first to borrow gaseous oxygen from water. In the oceans near their colonies, a kind of "water" atmosphere, saturated with oxygen, was created. The first marine organisms (coelenterates, sponges) breathed this oxygen. Gradually, oxygen began to be released into the atmosphere, filling it. Thanks to life blue-green algae on our planet began to form oxygen atmosphere.

One of the conditions for the emergence of life on the early Earth was the existence of a primary atmosphere with reducing properties. In the early Archean, the primary atmosphere of the Earth consisted of carbon dioxide, nitrogen, water vapor, argon, and abiogenic methane. For the origin of life on Earth, water in the liquid phase is absolutely necessary. In the Archean, the luminosity of the Sun was 25% lower than the present day, so positive temperatures could exist only at the equator.

From the gases of the primary atmosphere in the presence of catalysts, the first simplest organic compounds were formed in an abiogenic way: methane CH 4, formaldehyde НСОН, hydrogen cyanide НСN, ammonia NH 3. From these compounds, varieties of ribonucleic acids (RNA) are formed.

Subsequently, ribose was formed as a product of formaldehyde polymerization, and adenine was also synthesized as a product of hydrocyanic acid polymerization. The starting products adenine and ribose served as material for the synthesis of nucleotides (Fig. 4.1) and adenosine triphosphate (ATP).

Rice. 4.1. Formation of a nucleotide - a link in a DNA molecule
of three components

In the Late Archean (3 billion years ago), at the bottom of warm water bodies, from the formed organic compounds, colloidal associates arose, separated from the rest of the water by a lipid membrane (membrane). Later, thanks to the biosymbiosis of amino acids and semipermeable membranes, these associates took shape in the smallest primitive unicellular creatures - protobionts (prokaryotes) - nuclear-free cellular forms of bacteria. The sources of energy for these primitive life forms were anaerobic chemogenic reactions, which received energy for breathing through fermentation (chemosynthesis). Fermentation is an inefficient way of supplying energy, so the evolution of protobionts could not go beyond the unicellular form of life organization. For example, chemosynthesis is currently used by thermophilic bacteria in the "black smokers" of the mid-ocean ridges.

In the Late Archean and Early Proterozoic, formations of stromatolites were found, the nutrient base of which was abiogenic methane. The world's richest graphite deposit Cheber (1.5 million tons) was discovered in Yakutia, the content of which in rocks exceeds 27%. The peculiarity of this fact is that accumulations of graphite were found in crystalline schists of the Archean complex with an age of about 4 billion years.

Rice. 4.2.Scheme of distribution of microfossils in the Archean and Early Proterozoic: 1 - 4 - nano- and cyanobacteria; 5 - 10 - various microfossils; 11 - 20 - imprints of large morphologically
complex shapes

More than 2 thousand microorganisms have been identified and described in rocks with an age of up to 4 billion years (Fig. 4.2). Microorganisms in ancient rocks are found in transparent thin thin sections of 0.03 mm. As a result of the loss of water, planktonic animals have undergone mummification while maintaining their vital color. In addition, microorganisms underwent graphitization when organics were transformed into graphite. The high concentration of microorganisms in graphite gneisses and ores proves the primary organogenic origin of carbon in graphite deposits, which is consistent with the results of isotope analysis. We can say that graphite deposits are the graveyards of the most ancient microorganisms - a kind of rehearsal of life on Earth.

Rare unicellular and multicellular organisms have been found in ancient rocks with an age of up to 3.8 billion years. The massive finds were carbonate rocks formed by bacteria and blue-green algae that accumulated calcium carbonate. Their age is about 1.5 billion years.

Later, more complex organic substances appeared in the water, capable of carrying out photosynthesis. The inclusion of photosynthetic substances in the composition of protobiont cells made them autotrophic. The amount of oxygen in the water began to grow. Due to the release of oxygen into the atmosphere, it was transformed from a reducing into an oxidizing one.

Rice. 4.3. Evolution of oxygen content in the atmosphere
and various life forms

Eukaryotes originated from biosymbiosis of prokaryotic bacteria. Thus, in the conditions of a reducing atmosphere, primitive life arose, which subsequently created favorable conditions for the development of highly organized life on Earth.

At the beginning of the Early Proterozoic, there was a sharp increase in the abundance of photosynthetic microorganisms - blue-green algae. Somewhat later, photosynthetic unicellular organisms such as cyanobacteria appeared, capable of oxidizing iron. Perhaps the first photochemical organisms used radiation from the ultraviolet part of the spectrum. After the appearance of free oxygen (Fig. 4.3) and the ozone layer, autotrophic photosynthetic organisms began to use the radiation of the visible part of the solar spectrum. At that time, there were many types of algae, both freely floating in the water and attached to the bottom.

Evolution of the biosphere

Evolution in relation to living organisms can be defined as follows: the development over time of complex organisms from simpler organisms.

In natural science, there is the concept of "Pasteur's point" - such a concentration of free oxygen, at which oxygen breathing becomes a more efficient way of using the energy of the Sun than anaerobic fermentation. This critical level is equal to 1% of the current oxygen level in the atmosphere. When the oxygen concentration approached the Pasteur point, the victory of aerobes over anaerobes became final. The Earth's atmosphere crossed this boundary about 2.5 billion years ago. Since that time, the development of life has taken place under the influence of atmospheric oxygenation and many other environmental conditions (Fig. 4.4).

Breathing is the reverse process of photosynthesis, which releases ten times more energy than fermentation (fermentation). This energy can be used for the growth and movement of organisms. The animals made good use of the excess of this energy: they learned to move freely in search of food. Movement required the coordination of body parts and the ability to make difficult decisions. This required a brain to distinguish animals from plants. Thus, the emergence of the biosphere begins with chemical processes, which later acquire a biochemical character.

Rice. 4.4. Diagram of the evolution of the composition of the atmosphere and biosphere

These events ensured the rapid spread of life in the aquatic environment and the development of eukaryotic cells. It is believed that the first nuclear cells appeared after the oxygen content in the atmosphere reached 4% of the current level. It happened about 1 billion years ago. Multicellular organisms appeared about 700 million years ago.

The transition from the Proterozoic to the Phanerozoic was a sharp geological and biological boundary that radically changed the ecological situation on Earth. From that moment on, the atmosphere turned into an oxidizing one, which allowed biota to switch to a metabolism based on the oxidation reactions of organic matter synthesized by plants.

In addition to an increase in the partial pressure of oxygen in the atmosphere, continental drifts, climatic changes, ocean transgression and regression have become important factors influencing the evolution of the biosphere. These factors changed the ecological niches of biological communities and intensified their struggle for survival. For example, in the Silurian and Devonian, the ocean level rose by 250 m, in the Cretaceous period, the global transgression reached 400 m. During the periods of glaciation, water was conserved in continental glaciers, which lowered the ocean level by 130 m. These processes significantly changed the Earth's climate. The significant increase in ocean surface and decrease in land area mitigated seasonal and latitudinal climate changes. As the ocean receded, the continentality of the Earth's climate increased and seasonal temperature contrasts increased.

The strong processes that influenced the climate and its latitudinal zoning were the bacterial removal of nitrogen from the atmosphere and fluctuations in the Earth's precession angle depending on the continental drift and high-latitude glaciations. In addition, the change in the relative position of the continents altered the biological productivity of the oceans and the circulation of ocean currents. For example, after Australia moved north of Antarctica, a southern circumpolar current arose, cutting off Antarctica from the warm three oceans washing it. This system of climatic isolation of Antarctica is still in operation.

A radical restructuring of the metabolism of oceanic organisms took place about 400 million years ago, when forms with lungs appeared in the animal kingdom. The appearance of this organ, adapted to gas exchange in the air, allowed highly organized life to come to land.

In the Early Cretaceous (about 100 million years ago), the tectonic activity of the Earth began, which led to the spreading of the continents and the advance of the sea onto land. The result was an increase in the diversity of fauna as the continental shelf provinces became isolated. The Cretaceous transgression led to the flourishing of the carbonate-consuming fauna and microflora on the shelves, as a result of which strata of writing chalk were formed. However, this transgression caused crisis phenomena in the life of biocenoses of coral atolls of the ocean.

All the main frontiers of geological history and the corresponding division of the geochronological scale into eras, periods and epochs are largely due to events such as collisions and splits of continents, the emergence and closure of ecological niches, the formation, extinction and conservation of certain life forms. All these processes are ultimately caused by the tectonic activity of the Earth. A striking example of this is the endemic life forms of Australia and South America.

In the last phase of the Valdai glaciation (10-12 thousand years ago) became extinct most of"Mammoth" fauna: mammoths, giant deer, cave bears, saber-toothed tigers. This was partly due to the fault of man, and partly due to the fact that the humidity of the atmosphere increased significantly, the winters became snowy, which made it difficult for herbivores to access pasture. As a result, herbivores died from hunger, and predators from the absence of herbivores.

It is very likely that the Neanderthals became extinct about 30 thousand years ago, not only because of competition with the Cro-Magnons, but also because they could not stand the cooling of the Ice Age. Sharp climate fluctuations determined the migration of peoples and the formation of the racial composition of people.

Thus, the evolution of the biosphere over 3.5 billion years has developed in close relationship with the geological evolution of the planet. At the same time, there is also a feedback - the influence of life on the course of geological processes. IN AND. Vernadsky wrote: "On the earth's surface there is no chemical force more powerful in its effects than living organisms taken as a whole."

After an increase in the oxygen concentration in the atmosphere to a level of 10% of the modern, the ozone layer began to effectively protect living matter from hard radiation, after which life began to gradually emerge on land. First, plants penetrated land, creating soil there, then representatives of different taxa of invertebrates and vertebrates penetrated animals. Eras and periods passed when one composition of flora and fauna was replaced by another, more progressive composition and the appearance of all existing forms (Fig. 4.5).

Rice. 4.5. Explosive nature of the development of life at the boundary of the Proterozoic and Phanerozoic

After an increase in the oxygen concentration in the atmosphere to a level of 10% of the modern ( 2nd point of Pasteur) the ozone layer began to effectively protect living matter from hard radiation.

The Cambrian saw an evolutionary explosion of new life forms: sponges, corals, molluscs, algae, and the ancestors of seed plants and vertebrates. During subsequent periods of the Paleozoic era, life filled the oceans and began to land on land.

Further formation of terrestrial ecosystems proceeded autonomously from the evolution of aquatic ecosystems. Green vegetation provided a large amount of oxygen and food for the subsequent evolution of large animals. At the same time, the oceanic plankton was replenished with forms with calcareous and siliceous shells.

At the end of the Paleozoic, the Earth's climate changed. During this period, there was an increase in biological productivity and huge reserves of fossil fuels were created. Later (200-150 million years ago), the content of oxygen and carbon dioxide stabilized at the level of our day. In some periods, climate changes occurred, which caused a change in the level of the World Ocean. Periods of general cooling on the planet alternated with periods of warming with a cyclicality of about 100 thousand years. In the Middle Pleistocene (45-60 thousand years ago), a powerful glacier descended to 48 o N. in Europe and up to 37 o N in North America. Glaciers melted relatively quickly - in 1,000 years.

There is an immutable law of life: any group of non-primitive living organisms will die out sooner or later. Mass extinctions of entire species of animals have repeatedly occurred. So, 65 million years ago, many reptiles disappeared (Fig. 4.6). Their last representatives disappeared at the border of the Cenozoic. These extinctions were non-simultaneous, extended over many years and were not associated with human activity. According to paleontologists' calculations, the bulk (up to 98%) of the species that have ever existed on Earth (up to 500 million species) have become extinct.

Rice. 4.6. The rise and fall of reptiles

Evolutionary progress was not accidental. Life occupied new spaces, the conditions of existence on Earth were constantly changing, and all living things had to adapt to this. Communities and ecosystems have replaced each other. More progressive, more mobile forms arose, better adapted to the new conditions of life.

The biosphere develops with the close joint evolution of organisms. IN AND. Vernadsky, continuing the experience of previous naturalists, formulated the following principle: "The living comes only from the living, there is an impassable border between the living and the inanimate, although there is constant interaction."

Such close ecological interaction of large groups of organisms (for example, plants and herbivores) is called co-evolution. Co-evolution has been going on on Earth for billions of years. Anthropogenic factors emerged in a very short time, however, in terms of their impact on the biosphere, they became comparable to natural ones. Nature and biosphere in modern natural science are presented as dynamic systems passing through crisis states, catastrophes and bifurcation points.

The evolution of the biosphere is subject to the following three laws:

- law of constancy the evolutionary process in the biosphere: the evolution of living organisms occurs constantly as long as the Earth exists;

- irreversibility law evolution: when a species dies out, it will never reappear;

- divergence law: from the ancestral form, new populations of higher systematic categories are successively formed.

About 400 million years ago, life began to master the land. First, plants penetrated land, creating soil there, then representatives of various taxa of invertebrates and vertebrates penetrated. By the end of the Devonian, all land was covered with vegetation. By the end of the Carboniferous, gymnosperms, flying insects and the first carnivorous and herbivorous terrestrial vertebrates appear. At the end of the Permian there is a great extinction (corals, ammonites, ancient fish, etc.).

Rice. 4.7. Fragment of the history of the development of life forms on Earth
in the Mesozoic and Cenozoic

The first terrestrial vertebrates gave rise to amphibians, and those gave rise to reptiles. Reptiles flourished in the Mesozoic (Figure 4.7) and gave rise to birds and mammals. In the middle of the Jurassic period, there lived giant four-legged herbivorous dinosaurs up to 30 m long and weighing from 30 to 80 tons. Sharks of the modern type appeared. The first animals - the ancestors of modern mammals - appeared about 200 million years ago.

In the Cretaceous, South America and Africa moved apart from each other. During this period, another great extinction took place: dinosaurs disappear. After the global extinction of large lizards, mammals took the leading positions and dominate at the present time. Currently, up to 3 million animal species live on Earth.

There was the formation of new species and the extinction of those forms that could not withstand competition or did not adapt to a change in the natural environment. Before the advent of man, the extinction of certain species occurred slowly over many millions of years. It has been established that the life span of a bird species is on average 2 million years, and that of mammals is 600 thousand years. The natural environment has changed many times. The change in fauna was influenced by abiotic factors. Folding and mountain building took place, the climate changed. There was an alternation of warming and glaciation, rising and falling of the ocean level, the arid climate was replaced by a humid one.

The following main stages in the evolution of the biosphere can be distinguished.

1. The stage of the prokaryotic biosphere, which ended 2.5 billion years ago, which is characterized by: a reducing (anoxic) aquatic habitat and chemosynthesis; the appearance of the first photosynthetic organisms such as cyanobacteria; the vital activity of photosynthetic prokaryotes up to the 1st Pasteur point.

2. The stage of the prokaryotic biosphere with an oxidizing aquatic habitat, which ended about 1.5 billion years ago. This stage, which began after reaching the 1st Pasteur point, is characterized by: the appearance of respiration in the simplest organisms, which is 14 times more energetically more efficient than fermentation processes; the emergence of the first eukaryotic (having a nucleus) unicellular organisms.

3. Stage of unicellular and non-tissue organisms lasting up to 700 million years. The stage ended about 800 million years ago and is characterized by: the emergence of biodiversity of the simplest organisms, due to symbiogenesis; a transition period to the emergence of multicellularity of organisms.

4. Stage of multicellular tissue organisms. At this stage: in the Devonian (about 350 million years ago), terrestrial vegetation appeared; mammals appeared about 200 million years ago; the development of biodiversity of plants, fungi and animals dominates.

5. The anthropogenic stage - the appearance of Homo sapiens in the biosphere.