Archean era plant. Archeozoic era. Aromorphoses of the Archeozoic era

Archean era- the oldest, earliest period in the history of the earth’s crust. IN Archean era The first living organisms arose. They were heterotrophs and used organic compounds as food. End Archean era- the time of formation of the earth's core and a strong decrease in volcanic activity, which allowed the development of life on the planet.
Archean era which began about 4 billion years ago lasted approximately 1.5 billion years. Archean era divided into 4 periods: Eoarchean, Paleoarchean, Mesoarchean, Neoarchean

Earth's crust

The lower period of the Archean era - Eoarchean 4 - 3.6 billion years ago.
About 4 billion years ago the earth formed as a planet. Almost the entire surface was covered with volcanoes and rivers of lava flowed everywhere. Lava, erupted in large quantities, formed continents and ocean basins, mountains and plateaus. Constant volcanic activity, exposure to high temperatures and high pressure led to the formation of various minerals: various ores, building stone, copper, aluminum, gold, cobalt, iron, radioactive minerals and others. Approximately 3.8 billion years ago The first reliably confirmed igneous and metamorphic rocks such as granite, diorite and anorthosite formed on Earth. These rocks were found in a wide variety of places: on the island of Greenland, within the Canadian and Baltic shields, etc.

Neoarchaean 2.8 - 2.5 billion years ago - the last period of the Archean era, which ended 2.5 billion years ago, is the time of formation of the bulk of the continental crust, which indicates the exceptional antiquity of the Earth's continents. Atmosphere and climate of the Archean era. At the beginning Archean era There was little water on Earth; instead of a single ocean, there were only shallow basins that were not connected to each other. Atmosphere Archean era, mainly consisted of carbon dioxide CO2 and its density was much higher than the current one. Thanks to the carbon dioxide atmosphere, the water temperature reached 80-90°C. The nitrogen content was small, about 10-15%. There was almost no oxygen, methane and other gases. The atmospheric temperature reached 120°C.

Flora and fauna of the Archean era

Archaean era This is the time of the birth of the first organisms. The first 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. Eukaryotic green algae that then appeared released free oxygen from the ocean into the atmosphere, which contributed to the emergence of bacteria capable of living in an oxygen environment.
At the same time, on the border of the Archean Proterozoic era, two more major evolutionary events occurred - the sexual process and multicellularity appeared. Haploid organisms (bacteria and blue-greens) have one set of chromosomes. Each new mutation immediately manifests itself in their phenotype. If a mutation is beneficial, it is preserved by selection; if it is harmful, it is eliminated by selection. Haploid organisms continuously adapt to their environment, but they do not develop fundamentally new characteristics and properties. The sexual process dramatically increases the possibility of adaptation to environmental conditions, due to the creation of countless combinations in chromosomes.

Archean era- this is the first stage in the development of life on earth, spanning a time interval of 1.5 billion years. It originates 4 billion years ago. During the Archean era, the flora and fauna of the planet began to emerge, and the history of dinosaurs, mammals and humans began from here. The first deposits of natural resources appear. There were no mountain heights and no ocean, there was not enough oxygen. The atmosphere was mixed with the hydrosphere into a single whole - this prevented the sun's rays from reaching the earth.

Archean era translated from ancient Greek means “ancient.” This era is divided into 4 periods - Eoarchean, Paleoarchean, Mesoarchean and Neoarchean.

The first period of the Archean era lasted approximately 400 million years. This period is characterized by increased meteorite showers, the formation of volcanic craters and the earth's crust. The active formation of the hydrosphere begins, and salty bodies of hot water appear, isolated from each other. The atmosphere is dominated by carbon dioxide, the air temperature reaches 120 °C. The first living organisms appear - cyanobacteria, which begin to produce oxygen through photosynthesis. The formation of Vaalbara, the main earthly continent, takes place.

Paleoarchaean

The next period of the Archean era covers a period of time of 200 million years. The Earth's magnetic field is strengthened by increasing the hardness of the earth's core. This has a beneficial effect on the living conditions and development of simple microorganisms. A day lasts about 15 hours. The formation of the world's oceans takes place. Changes in underwater ridges lead to a slow increase in the volume of water and a decrease in the amount of carbon dioxide in the atmosphere. The formation of the first earth's continent continues. Mountain ranges do not yet exist. Instead, active volcanoes rise above the ground.

Mesoarchean

The third period of the Archean era lasted 400 million years. At this time, the main continent splits into two parts. As a result of a sharp cooling of the planet, which is caused by constant volcanic processes, the Pongol glacial formation is formed. During this period, the number of cyanobacteria begins to actively grow. Chemolithotrophic organisms develop that do not require oxygen and sunlight. Vaalbar is fully formed. Its size is approximately equal to the size of modern Madagascar. The formation of the continent of Ur begins. Large islands slowly begin to form from volcanoes. The atmosphere, as before, is dominated by carbon dioxide. The air temperature remains high.

The last period of the Archean era ended 2.5 billion years ago. At this stage, the formation of the earth's crust is completed, and the level of oxygen in the atmosphere increases. The continent of Ur becomes the basis of Kenorland. Most of the planet is occupied by volcanoes. Their active activity leads to increased formation of minerals. Gold, silver, granites, diorites and other equally important natural resources were formed during the Neoarchean period. IN last centuries of the Archean era The first multicellular organisms appear, which were later divided into terrestrial and sea inhabitants. Bacteria begin to develop the sexual process of reproduction. Haploid microorganisms have one set of chromosomes. They constantly adapt to changes in their environment, but at the same time they do not develop other properties. The sexual process allowed adaptation to life with changes in the set of chromosomes. This made it possible for the further evolution of living organisms.

Flora and fauna of the Archean era

The flora of this era cannot boast of diversity. The only plant species are unicellular filamentous algae - spheromorphids - the habitat of bacteria. When these algae form in colonies, they can be seen without special instruments. They can go free swimming or attach to the surface of something. In the future, the algae will form a new form of life - lichens.

During the Archean era the first prokaryotes- single-celled organisms that do not have a nucleus. Through photosynthesis, prokaryotes produce oxygen and create favorable conditions for the emergence of new life forms. Prokaryotes are divided into two domains - bacteria and archaea.

Archaea

It has now been established that they have features that distinguish them from other living organisms. Therefore, the classification that combines them with bacteria into one group is considered outdated. Externally, archaea are similar to bacteria, but some have unusual shapes. These organisms can absorb both sunlight and carbon. They can exist in the most unsuitable conditions for life. One type of archaea is food for marine life. Several species have been found in the human intestine. They take part in the digestive processes. Other types are used to clean sewage ditches and ditches.

There is a theory, unconfirmed by facts, that during the Archean era the birth and development of eukaryotes - microorganisms of the fungal kingdom, similar to yeasts - occurred.

The fact that life on earth originated during the Archean era is evidenced by the found fossilized stromalites - waste products of cyanobacteria. The first stromatolites were discovered in Canada, Siberia, Australia and Africa. Scientists have proven that it was bacteria that had a huge impact on the formation of aragonite crystals, which is found in mollusk shells and is part of corals. Thanks to cyanobacteria, deposits of carbonate and siliceous formations arose. Colonies of ancient bacteria look like mold. They were located in the area of ​​volcanoes, at the bottom of lakes, and in coastal areas.

Archean Climate

Scientists have not yet been able to find out anything about the climate zones of this period. The existence of zones of different climates in the Archean era can be judged by ancient glacial deposits - tillites. Remains of glaciations have been found in America, Africa, and Siberia today. It is not yet possible to determine their true size. Most likely, glacial deposits covered only mountain peaks, because vast continents had not yet been formed during the Archean era. The existence of a warm climate in some areas of the planet is indicated by the development of flora in the oceans.

Hydrosphere and atmosphere of the Archean era

In the early period there was little water on earth. The water temperature during the Archean era reached 90°C. This indicates the saturation of the atmosphere with carbon dioxide. There was very little nitrogen in it, there was almost no oxygen in the early stages, the remaining gases are quickly destroyed under the influence of sunlight. The atmospheric temperature reaches 120 degrees. If nitrogen predominated in the atmosphere, then the temperature would not be lower than 140 degrees.

In the late period, after the formation of the world ocean, the level of carbon dioxide began to decrease noticeably. The temperature of water and air also dropped. And the amount of oxygen increased. Thus, the planet gradually became suitable for life of various organisms.

Archaean minerals

It was during the Archean era that the greatest formation of minerals occurred. This is facilitated by the active activity of volcanoes. Colossal deposits of iron, gold, uranium and manganese ores, aluminum, lead and zinc, copper, nickel and cobalt ores were laid down by this era of the earth's life. On the territory of the Russian Federation, Archean deposits have been found in the Urals and Siberia.

In details periods of the Archean era will be discussed in subsequent lectures.

The oldest period of the earth's existence, covering the time period from 4 to 2.5 billion years ago, is called the “Archaean era”. The flora and fauna were just beginning to emerge, there was very little oxygen on Earth, and among the water bodies on the planet there was only one shallow ocean, consisting of several reservoirs with saturated salt water, and there were no mountainous landscapes or depressions at all. This is the period when mineral deposits began to form: graphite, nickel, sulfur, iron and gold.

Rays of sunlight could not yet penetrate through the mixed hydrosphere and atmosphere, which made up a single shell of steam and gas. The resulting greenhouse effect prevented the sun from touching the earth.

The Archean era was named so by the American scientist J. Dana in 1872. The term “archaean” from ancient Greek means “ancient.” The Archean is divided into four main eras, starting from the most ancient - the Eoarchean - and ending with the Neoarchean. Let's look at them in more detail.

The beginning of the Archean - Eoarchean

The 400 million year period began about 4 billion years ago. The Eoarchean is characterized by frequent meteorite falls and the formation of craters. The lava covering the surface of the planet gradually began to give way to the earth's crust, which was actively forming.

The Archean era in this time period is known for the laying of the most ancient rocks, the largest formations of which were found in Greenland. Their age is approximately 3.8 billion years.

The formation of the hydrosphere was just beginning. And although the World Ocean had not yet appeared, there were already hints of the first small water formations. With their characteristic isolation from each other, with concentrated salty and very hot water.

There was little oxygen and nitrogen in the atmosphere; a significant part of it was carbon dioxide. The temperature in the Earth's air envelope reached 120 °C.

The first organisms of the Archean era began to appear precisely then. These were cyanobacteria that left behind ancient stromatolites - waste products. These microorganisms produce oxygen through photosynthesis, being the most ancient form of life on the planet.

The most important moment in the Eoarchean is considered to be the beginning of the formation of the first earthly continent - Vaalbara.

Second era - Paleoarchean

The Archean era of this period covers a time period of 200 million years, which began 3.6 billion years ago. Then the day had a duration of no more than 15 hours. The formation of the main continent was ending, and the still shallow World Ocean appeared. The Earth's core became more solid, which strengthened the Earth's magnetic field almost to modern levels.

It is this period that allows us to assert that already in those times the first living organisms appeared. It is known for sure that the remains of their waste products found today date back to the Paleoarchean.

Animals of the Archean era are the first bacteria, organisms that contributed to the formation of the Earth's atmosphere through photosynthesis, creating the conditions for the development of new forms of life.

Mesoarchean: Vaalbara Schism

Mesoarchean - a period that lasted 0.4 billion years (began 3.2 billion years ago). It was then that Vaalbara split, which split at an angle of 30° into two separate parts. The most famous crater in our times in Greenland also appeared from a collision with an asteroid. Perhaps the first glaciation, the Pongolian glaciation, occurred on Earth during the Mesoarchean period.

The development of life in the Archean era of the Mesoarchean period was characterized by an increase in the number of cyanobacteria.

The final stage is Neoarchean

The Neoarchean ended 2.5 billion years ago. It is characterized by the completion of the formation of the earth's crust, as well as the release of large amounts of oxygen, which subsequently led (at the beginning of the next era) to an oxygen catastrophe. It was then that the Earth's atmosphere completely changed - oxygen began to predominate in its composition.

Volcanic activity developed rapidly, which contributed to the formation of rocks and precious metals and stones. Granites, syenites, gold, silver, emeralds, chrysoberyls - all this and much more appeared several billion years ago, in the Neoarchean.

What else is interesting about the Archean era? The flora and fauna of that time formed the most ancient deposits of minerals that are still widely used today. This was also influenced by the unstable situation on the planet. Forming landscapes, the earth's crust and the first mountain formations were destroyed under the influence of ocean waters and the spill of volcanic lava.

Animal world

Scientists claim that the origin of life began precisely during the Archean period. And although these forms were too small, they still represented real living microorganisms, the first bacteriological communities that left their mark on the planet in the form of fossilized stromatolites

It was established that it was bacteria that made a significant contribution to the formation of nanocrystals of arogonite, a mineral based on calcium carbonate. Aragonite is part of the surface layer of shells of modern mollusks and is found in the exoskeleton of corals.

Cyanobacteria became the culprits in the formation of deposits of not only carbonate, but also siliceous sedimentary formations.

The Archean era is characterized by the appearance of the first prokaryotes - prenuclear single-celled organisms.

Characteristics of prokaryotes

Living organisms do not have a formed nucleus, but they are a full-fledged cell. By feeding through photosynthesis, prokaryotes produce oxygen. The DNA information (nucleotide) carried by the cell is not packaged in the protein shell of the nucleus (histone).

The group is divided into two domains:

• Bacteria.
• Archaea.

Archaea

Archaea are the oldest microorganisms, like prokaryotes, which do not have a nucleus. At the same time, their structure of life organization differs from that of other types of microbes. Archaea are similar in appearance to bacteria, but some have an unusual flat or square shape.

There are five types of archaea, although it is quite difficult to classify them. It is impossible to grow archaebacteria in nutrient media, so all research is carried out only on the basis of samples taken from their habitat.

These microorganisms can use both sunlight and carbon as an energy source, depending on the species. Archaea do not form spores and reproduce asexually. They are not pathogenic to humans and can survive in the most extreme conditions: ocean, hot springs, soil, salt lakes. The most abundant species of archaea makes up a significant portion of the plankton in the oceans, which serves as food for marine animals.

Some species even live in the human intestines, helping to carry out digestive processes. Archaea are used to create biological gas, clean sewers, and settlers.

Plants

As you can understand, the Archean era, whose flora was slightly richer than animals, was not characterized by the presence of vertebrates, fish, and even multicellular algae. Although the beginnings of life have already appeared. As for the flora, scientists have established that the only plants at that time were filamentous algae, in which, by the way, bacteria lived.

And blue-green algae, previously mistakenly considered plants, turned out to be colonies of cyanobacteria that use both carbon and oxygen as a resource to support life and are not part of the archaeal plant world.

filamentous algae

The Archean era was marked by the appearance of the first plants. These are single-celled filamentous algae that are the simplest form of flora. They do not have a specific shape, structure, organs or tissues. Forming colonies, they become visible to the naked eye. This is mud on the surface of the water, phytoplankton in its depths.

The cells of filamentous algae are connected into a single thread, which can have branches. They can easily either float freely or attach to various surfaces. Reproduction occurs by dividing the threads into two separate ones. Both all threads and only the outermost, or main, threads can be capable of division.

Algae do not have flagella; they are connected to each other through microscopic cytoplasmic bridges (plasmodesmata).

During evolution, algae formed another form of life - lichens.

The Archaean Era is the first period when biological life on Earth appeared from almost nothing. This is a turning point in the history of the evolution of the planet, characterized by the emergence of conditions for the emergence of flora and fauna: the formation of the earth’s crust, the World Ocean, the atmosphere, suitable for life of other more complex forms of flora and fauna.

The end of the Archean marked the beginning of the development of the sexual process of reproduction in bacteria, the appearance of the first multicellular microorganisms, some of which later became terrestrial organisms, others acquired characteristics of waterfowl and settled in the ocean.

Life began in the Archean era. Since the first living organisms did not yet have any skeletal formations, almost no traces remained of them. However, the presence of rocks of organic origin among the Archean deposits - limestone, marble, graphite and others - indicates the existence of primitive living organisms in this era. They were single-celled prenuclear organisms (prokaryotes): bacteria and blue-green algae.

Life in water was possible due to the fact that water protected organisms from the harmful effects of ultraviolet rays. That is why the sea could become the cradle of life.

4 major events of the Archean era

In the Archean era, four major events (aromorphosis) occurred in the evolution of the organic world and the development of life:

• Eukaryotes appeared;
• photosynthesis;
• sexual process;
• multicellularity.

The appearance of eukaryotes is associated with the formation of cells with a true nucleus (containing chromosomes) and mitochondria. Only such cells are capable of dividing mitotically, which ensures good preservation and transmission of genetic material. This was a prerequisite for the emergence of the sexual process.

The first inhabitants of our planet were heterotrophic and fed on organic substances of abiogenic origin dissolved in the primordial ocean. The progressive development of primary living organisms subsequently provided a huge leap (aromorphosis) in the development of life: the emergence of autotrophs that use solar energy to synthesize organic compounds from the simplest inorganic ones.

Of course, such a complex compound as chlorophyll did not arise immediately. Initially, simpler pigments appeared that facilitated the absorption of organic substances. From these pigments, chlorophyll apparently developed.

Over time, the organic substances that had accumulated in it abiogenically began to dry out in the primordial ocean. The appearance of autotrophic organisms, primarily green plants capable of photosynthesis, ensured further continuous synthesis of organic substances, thanks to the use of solar energy (the cosmic role of plants), and, consequently, the existence and further development of life.

With the advent of photosynthesis, the organic world diverged into two trunks, differing in the way they feed. Thanks to the emergence of autotrophic photosynthetic plants, water and the atmosphere began to be enriched with free oxygen. This predetermined the possibility of the emergence of aerobic organisms capable of more efficient use of energy in the process of life.

The accumulation of oxygen in the atmosphere led to the formation of an ozone screen in its upper layers, which did not transmit life-destructive ultraviolet rays. This paved the way for life to reach land. The appearance of photosynthetic plants provided the possibility of the existence and progressive development of heterotrophic organisms.

The appearance of the sexual process led to the emergence of combinative variability supported by selection. Finally, apparently, in this era, multicellular organisms evolved from colonial flagellates. The emergence of the sexual process and multicellularity prepared the way for further progressive evolution.

Archaea

General information and division

Archaean, Archean era (from the Greek ἀρχαῖος (archios) - ancient) is a geological eon that precedes the Proterozoic. The upper limit of the Archean is taken to be about 2.5 billion years ago (±100 million years). For the lower limit, which is still not officially recognized by the International Stratigraphic Commission, - 3.8-4 billion years ago. The vagueness of the lower limit of the Archean is explained by 2 theories of its definition: according to the first of them, the lower limit of the Archean era is the finds of ancient organisms dating back to 3.8 billion years ago; according to the second theory, the lower limit should be considered the end of the cold period, which dominated throughout the entire period preceding the Archean eon - gadea (catarchaea). The duration of the Archean is approximately 1.5 billion years.

Archean, according to modern ideas, is divided into 4 periods: Eoarchean, Paleoarchean, Mechoarchean and Neoarchean, which are distinguished purely chronologically. Previously, the Archean included the Katarchaean, which is currently separated into a separate eon.

Eoarchean is the lower period of the Archean era, covering the time interval from 4 to 3.6 billion years ago. The Eoarchean is notable for being the time of formation of the hydrosphere and the discovery of the supposed remains of the first prokaryotes, stromatolites and ancient rocks.

The period following the Eorchean, the Paleoarchean, is the time of formation of the first supercontinent in the history of the Earth - Vaalbara and a single World Ocean. The first reliable remains of living organisms (bacteria) and traces of their vital activity date back to this time. The duration of the Paleoarchean is 400 million years.

After the Paleoarchean came the Mesoarchean, which lasted from 3.2 to 2.8 billion years ago. The period is interesting due to the split of Vaalbara and the wide distribution of fossils of ancient life forms.

Finally, the last period of the Archean era - the Neoarchean, which ended 2.5 billion years ago, is the time of formation of the bulk of the continental earth's crust, which indicates the exceptional antiquity of the Earth's continents.

Tectonics

Archean tectonics is characterized, first of all, by the beginning of the formation of the most ancient continental cores (shields), relics of which were found on all ancient platforms except the Chinese-Korean and South Chinese. The formation of the continental cores is associated with the Kola (Sami; Baltic Shield) or Transvaal (South Africa) folding, which appeared at the turn of about 3 billion years ago, and the White Sea folding (Baltic Shield), also known as the Kenoran (Canadian Shield) or Rhodesian folding (South Africa), which appeared about 2600 million years ago.

Initially, there were no large continental formations on Earth, which was caused by high geological activity.

But, approximately 3.6 billion years ago, everything changed and the continents of the Earth united into the hypothetical supercontinent Valbara. This is confirmed by geochronological and paleomagnetic studies between two Archean cratons or protocontinents: the Kaapval Craton (Kaapval Province, South Africa) and the Pilbara Craton (Pilbara region, Western Australia). Additional evidence is the coincidence of the stratigraphic sequences of the greenstone and gneiss belts of these two cratons. Today, these Archean greenstone belts are distributed along the margins of the Upper Craton in Canada, as well as the cratons of the ancient continents of Gondwanaland and Laurasia.

Approximately 2.8 billion years ago, the first supercontinent in Earth's history began to break apart.

This is evidenced by geochronological and paleomagnetic studies showing a circular transverse separation of the Kaapvaal and Pilbara cratons about 2.77 billion years ago.

In general, the Archean era is characterized by very violent tectonic activity, resulting in frequent volcanic eruptions, earthquakes, etc. This was facilitated by: the high temperature of the internal layers of the Earth, the formation of a planetary core near the Earth and the decay of short-lived radionuclides.

Approximately 3.8 billion years ago, the first reliably confirmed igneous and metamorphic rocks, such as granite, diorite and anorthosite, formed on Earth. These rocks were found in a wide variety of places: on the island of Greenland, within the Canadian and Baltic shields, etc.

By the way, some scientists take the age of these very ancient rocks as the lower limit of the Archean.

3 billion years ago, a period of active formation of the continental crust began. Over a period of 500 million years, up to 70% of its total mass was formed. Although most scientists still believe that the continental crust of Archean age makes up only 5-40% of the entire continental crust of modern times.

Hydrosphere and atmosphere. Climate

At the very beginning of the Archean era, there was little water on Earth; instead of a single ocean, there were only scattered shallow basins. The water temperature reached 70-90° C, which could only be observed if the Earth had a dense carbon dioxide atmosphere at that time. Indeed, of all the possible gases, only CO 2 could create increased atmospheric pressure (for Archean - 8-10 bar). There was very little nitrogen in the atmosphere of the early Archean (10-15% of the volume of the entire Archean atmosphere), there was practically no oxygen at all, and gases such as methane were unstable and quickly decomposed under the influence of hard radiation from the Sun (especially in the presence of hydroxyl ions, also occurring in a humid atmosphere).

The temperature of the Archean atmosphere under the greenhouse effect reached almost 120°C. If, at the same pressure, the atmosphere in the Archean consisted, for example, only of nitrogen, then surface temperatures would be even higher and reach 100°C, and the temperature under the greenhouse effect would exceed 140°C.

About 3.4 billion years ago, the amount of water on Earth increased significantly and the World Ocean emerged, covering the crests of the mid-ocean ridges. As a result, the hydration of the basaltic oceanic crust noticeably increased, and the rate of increase in the partial pressure of CO 2 in the Late Archean atmosphere decreased somewhat. The most radical drop in CO 2 pressure occurred only at the turn of the Archean and Proterozoic after the separation of the earth's core and the associated sharp decrease in the tectonic activity of the Earth. Due to this, the smelting of oceanic basalts also sharply decreased in the Early Proterozoic. The basaltic layer of the oceanic crust became noticeably thinner than it was in the Archean, and beneath it a serpentinite layer formed for the first time - the main and constantly renewed reservoir of bound water on Earth.

Flora and fauna

Archean deposits lack skeletal fauna, which serves as the basis for constructing the stratigraphic scale of the Phanerozoic; nevertheless, there are quite a lot of various traces of organic life here.

These include waste products of blue-green algae - stromatolites, which are coral-like sedimentary formations (carbonate, less often silicon), and waste products of bacteria - oncolites.

The first reliable stromatolites were discovered only at the turn of 3.2 billion years ago in Canada, Australia, Africa, the Urals and Siberia. Although there is evidence of the discovery of remains of the first prokaryotes and stromatolites in sediments aged 3.8-3.5 billion years, in Australia and South Africa.

Also, in the siliceous rocks of the Early Archean, peculiar filamentous algae were found, which are well preserved, in which details of the cellular structure of the organism can be observed. At many stratigraphic levels, there are tiny round bodies (up to 50 m in size) of algal origin, previously mistaken for spores. They are known as "acritarchs" or "spheromorphids".

The animal world of the Archean is much poorer than the plant world. Some indications of the presence of animal remains in Archean rocks refer to objects that appear to be of inorganic origin (Aticocania Walcott, Tefemar kites Dons, Eozoon Dawson, Brooksalla Bassler) or are products of leaching of stromatolites (Carelozoon Metzger). Many archaean fossils are not fully deciphered (Udokania Leites) or do not have an accurate reference (Xenusion querswalde Pompecki).

Thus, in the Archean zone, prokaryotes of two kingdoms were reliably found: bacteria, predominantly chemosynthetic, anaerobic and photosynthetic cyanobionts that produce oxygen. It is possible that the first eukaryotes from the kingdom of fungi, morphologically similar to yeast fungi, also appeared in the Archean.

The most ancient bacterial biocenoses, i.e. communities of living organisms, which included only producers and destructors, were similar to films of mold (so-called bacterial mats) located at the bottom of reservoirs or in their coastal zone. Volcanic areas often served as oases of life, where hydrogen, sulfur and hydrogen sulfide, the main donors of electrons, came to the surface from the lithosphere.

Throughout almost the entire Archean era, living organisms were single-celled creatures, highly dependent on natural factors. And only at the turn of the Archean and Proterozoic two major evolutionary events occurred: the sexual process and multicellularity appeared. Haploid organisms (bacteria and blue-green algae) have one set of chromosomes. Each new mutation immediately manifests itself in their phenotype. If a mutation is beneficial, it is preserved through the process of natural selection; if it is harmful, it is eliminated. Haploid organisms continuously adapt to their environment, but they do not develop fundamentally new characteristics and properties. The sexual process dramatically increases the possibility of adaptation to environmental conditions, due to the creation of countless combinations in chromosomes. Diploidy, which arose simultaneously with the formation of the nucleus, allows mutations to be preserved and used as a reserve of hereditary variability for further evolutionary transformations.

Minerals

The Archean era is very rich in minerals. Associated with it are enormous deposits of iron ores (ferruginous quartzites and jaspilites), aluminum raw materials (kyanite and sillimanite) and manganese ores; the largest deposits of gold and uranium ores are associated with Archean conglomerates; with basic and ultrabasic rocks - large deposits of copper, nickel and cobalt ores; with carbonate rocks - lead-zinc deposits. Pegmatites are the main source of mica (muscovite), ceramic raw materials and rare metals.

On the territory of Russia, deposits of the Timan Ridge, the Urals, the Dnieper crystalline strip, and the Podkamennaya Tunguska region are associated with Archean deposits...