Presentation, report Proterozoic era. Proterozoic era Proterozoic era plants and animals

Proterozoic era

In Proterozoic deposits we already find traces of crawling worms, prints of coelenterates, sponge needles, and shells of protozoa - creatures that are quite biologically complex. The evolutionary process goes from simple to complex organisms. Consequently, the emergence of Proterozoic creatures was impossible without a long evolutionary process, which originated from lumps of cytoplasm that appeared in the Archean seas.

The coal-like material shungite was found in Proterozoic deposits. This indicates the appearance in the Proterozoic era of plants, from the remains of which coal was formed. Marble deposits suggest that animals with calcareous shells lived in the Proterozoic. Over time, the limestones formed from the deposits of these shells turned into marble.

The first currently known groups of creatures in the Proterozoic seas were, apparently, flagellates, located on the border between the plant and animal worlds. From them came algae, mushrooms and all groups of the animal world.

In the Proterozoic era, the first multicellular organisms evolved from colonial unicellular organisms, whose cells began to perform various functions. They were sponges, archaeocyaths (sponge-like animals). Life at that time was closely connected with the sea. There were no organisms on land, except perhaps bacteria, which could adapt to a wide variety of conditions. But what the Archean or Proterozoic bacteria were can only be guessed at.

Proterozoic rocks contain deposits of the sea, land, rivers, mountains, deserts and glaciers. Consequently, the climate of the Proterozoic was quite diverse. The marine sediments are covered by volcanic sediments, which are also overlain by marine sediments. From this we can conclude that periods of quiet development of the Proterozoic earth’s crust were replaced by violent mountain-building processes.

Many minerals are associated with Proterozoic deposits: iron ores, marble, graphite, nickel ore, piezoquartz, kaolin, gold, mica, talc, molybdenum, copper, bismuth, tungsten, cobalt, radioactive minerals, precious stones. In the south of Ukraine at that time there was a shallow sea, surrounded on all sides by mountain ranges. The mountains were weathered, and the products of weathering were deposited on the bottom of the sea. At the end of the Proterozoic, thanks to mountain-building processes, mountains arose in place of the sea, and sedimentary deposits metamorphosed. This is how the iron ore deposit of the Krivoy Rog basin was formed.

The duration of the Proterozoic era is 2 billion years.

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Organic world of the Proterozoic

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Development of the organic world. The development of the organic world in the Proterozoic is a huge stage in the history of the Earth. During this era, bacteria and algae flourished exceptionally. An intensive process of formation of sedimentary rocks took place with the participation of these organisms. The Proterozoic era includes the formation of the largest deposits of iron ores of organic origin (sedimentary iron, a product of the vital activity of iron bacteria). The dominance of blue-green prokaryotes in the Proterozoic is replaced by the flourishing of eukaryotes-green algae. Along with the plants floating in the dance of the water, filamentous forms appear attached to the bottom. About 1350 million years ago, representatives of low fungi were noted. The first multicellular animals arose 900-1000 million years ago. Ancient multicellular plants and animals lived in the bottom layers of the ocean. Life in the bottom layer required the division of the body into parts, some of which served for attachment to the substrate, others for nutrition. In some forms this was achieved through the development of a giant multinucleated cell. However, the acquisition of multicellularity and organ formation turned out to be more promising. Most animals of the Late Proterozoic were represented by multicellular forms. The end of the Proterozoic can be called the “age of jellyfish”. Annelids arise from which mollusks and arthropods originated.

Throughout almost the entire Proterozoic, the climate was warm and even.

Life was presented as anaerobic prokaryotes(bacteria and cyanobacteria), and aerobic unicellular eukaryotes. All of them, according to the latest data, appeared in archaean. The vital activity of these organisms was of decisive importance in changing the content of carbon dioxide and oxygen in the atmosphere. From the beginning of the Proterozoic, the oxygen content in the atmosphere began to gradually increase, and in the middle of the Proterozoic it increased sharply, which led to the formation of the first thick sedimentary deposits based on iron oxides. These reddish colored deposits are very characteristic of the Proterozoic. The accumulation of oxygen in the Earth's atmosphere led to the formation of the ozone layer, which blocked ultraviolet radiation from the Sun, which is destructive to all living things. Around the same time, the first multicellular algae and, possibly, the first multicellular animals were known. OK. 700 million years ago, biomineralization processes became widespread in the seas: silica, associated with golden algae, and calcareous, associated with stromatolites. In the vast warm shallow seas of the Proterozoic, stromatolites created the first reefs in the history of the Earth, formed as a product of the vital activity of cyanobionts in symbiosis with bacteria. At the end of the Proterozoic - in the Riphean, powerful manifestations of volcanism began. Huge masses of volcanic ash were thrown into the atmosphere. Very little solar heat began to reach the Earth. This led to global cooling. Almost the entire globe was under ice cover. At this time, many ancient organisms became extinct. Their extinction and changes in the chemical composition of air and water created new conditions for further biological evolution.

Despite the climatic differentiation, especially at the end of the Proterozoic, it must be admitted that in comparison with the modern era on Earth in those distant times, the climate was more monotonous. This is explained by the small thickness of the atmosphere, its high content of carbon dioxide and the large area of oceans and seas. The greenhouse regime determined the existence of high average annual temperatures. In the Late Riphean, average annual temperatures, judging by the nature of carbonate accumulation (abundance of reef formations), the widespread development of weathering crusts, peculiar organisms, as well as the data on determining absolute temperature values by isotope and magnesium paleothermometry, were quite high. Based on the ratio of heavy and light oxygen isotopes in siliceous and carbonate rocks of the Proterozoic, the average temperature of the earth's surface was 50-60°C and decreased to 40°C.

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Animal Organisms. At the end of the Proterozoic, 900-1000 million years ago, the first multicellular animals arose. Ancient multicellular plants and animals lived in the bottom layers of the ocean. Most animals of the Late Proterozoic were represented by multicellular forms. The end of the Proterozoic is called the "age of jellyfish." Annelids arise, from which mollusks and arthropods originated. During the Proterozoic, the dominance of prenuclear organisms (prokaryotes) was replaced by the dominance of nuclear organisms (eukaryotes). Multicellular forms replaced unicellular and colonial forms. Life has become a geological factor. Living organisms, changing the shape and composition of the earth's crust, formed the Earth's biosphere, and as a result of photosynthesis, the composition of the atmosphere changed. The accumulation of oxygen in the atmosphere contributed to the emergence and development of higher organisms - animals; it is assumed that by the end of the Proterozoic all groups of animals, except vertebrates, arose.

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Conclusion: During the Proterozoic, the dominance of prokaryotes was replaced by the dominance of eukaryotes. Multicellular forms replaced unicellular and colonial forms. Life has become a geological factor. Living organisms changed the shape and composition of the earth's crust, forming its upper layer - the biosphere. As a result of photosynthesis, the composition of the atmosphere changed. The accumulation of oxygen in the atmosphere contributed to the development of higher heterotrophic animal organisms.

Have you ever wondered what the Proterozoic era was like? Most likely no. Unless someone remembers some meager data from a long-ago school curriculum. For example, about the development of life in the Proterozoic era, about the formation of climate, or about the beginning of the Ice Age. Of course, all this is very little, especially considering the role this time played in the subsequent life of our planet.

This article contains a lot of interesting information. This means that the reader will receive comprehensive answers to many questions that affect the development of life on earth. Separately, we will talk about unusual representatives of flora and fauna, the harsh climate, and the peculiarities of the formation of various types of minerals.

general information

Scientists claim that this period began more than 2600 million years ago, and the error in calculations can be considerable and amount to approximately 100 million years.

According to experts, the Proterozoic era existed on the planet for quite a long time, for 2 billion years. It was this period that made it the longest period in the entire history of our planet.

Just then, worms and coelenterates began to crawl on the surface of the planet, and the simplest calcareous shells existed. Also, the Proterozoic era is known in history as the period when the so-called coal plants originated.

Among other things, this period of time is also famous for such debutants of the underwater world as flagellates, which were at the boundary of development between animals and vegetation.

By the way, not everyone knows that during evolution, after a certain decay, some particles of flagellates became algae or fungi. Others, in turn, gradually turned into representatives of the fauna.

At the same time, microscopic radiolarians, sponges, archaeocyaths, brachiopods, gastropods and other multicellular creatures appeared. The pinnacle of evolutionary development in the Proterozoic was large predatory arthropods, namely crustacean scorpions.

The Archean and Proterozoic eras are a time when a vast area of the Earth was covered by an endless sea. By the way, during this period minerals appeared en masse, and the World Ocean began to take on a more or less modern appearance.

In general, scientists divide the Proterozoic periods into the following stages:

Peleoproterozoic.
Mesoproterozoic.
Neopretorosa.

Climate of the Proterozoic era

We can safely say that in this era the climate was very diverse. This is confirmed by the large number of traces found from mountains, deserts, lakes, seas, etc. Marine deposits are mainly located in two levels and are covered with volcanic rocks and an additional marine layer. In the rocks, everything looks as if the planet was crushed by a mighty hand. Therefore, scientists assumed that violent underground processes occurred in the Proterozoic.

By the end of the early Proterozoic, the Earth's climate began to change, namely, the greenhouse effect decreased. This significantly lowered the planet's surface temperature. In addition, the Sun shone 10% less than it does now.

As a result, the first ice age came. Then, after 1700 million years, another larger one came, as a result of which almost the entire Earth was covered with ice. And temperatures at the equator became equal to temperatures in modern Antarctica. Animals of the Proterozoic era began to develop only with the melting of the ice, and it was then that a surge in biodiversity occurred.

What was happening to the earth's surface at this time?

Despite the huge masses of ice that formed at the end of the Proterozoic era, active volcanic activity continued on Earth, the air temperature gradually increased, and parts of the continents slowly began to be freed from ice deposits.

Many living organisms of the Proterozoic still almost completely disappeared during permafrost. But, most likely, in the World Ocean, in tropical latitudes, where there were areas of open water with free access to light and carbon dioxide, there was still life.

Such global glaciations did not occur again; scientists believe that this happened due to the newly formed continents, which no longer had a near-equatorial configuration.

Aromorphoses of the Proterozoic era. To walk or not to walk?

All creatures had to make exactly this choice in the Proterozoic era: to walk or not. Scientists claim that this is where the division of nature into plant and animal originated.

This happened thanks to the substance chlorophyll, which arose in representatives of the flora, since it is the most important element for photosynthesis.

Almost all living creatures were able to adapt to a mobile lifestyle, since they ate other animals or plants, and in order to get to the chosen and so necessary food, it was necessary to constantly move.

This is exactly how life developed on earth.

Features of the flora

During the Proterozoic, a change in the chemical composition of the atmosphere was observed from active carbon dioxide to neutral. This gave rise to the emergence of eukaryotic life forms, as well as algae with a separate nucleus, etc.

Algae, which were considered the first true plants, also reached a wide variety. Especially in the Proterozoic era, unicellular, colonial blue-green algae developed widely, and red and green algae also appeared.

How could one come to this conclusion? The thing is that the remains of shulgit, discovered by archaeologists and attributed to the Proterozoic, are similar to coal, which is formed from plants.

What was the fauna of this period like?

In the Proterozoic era, the first worms and coelenterates began to appear. The origin of many species began with lumps of cytoplasm located in the seas.

In addition, animals with calcareous shells lived on Earth. The best evidence of this fact is the discovered remains of ancient marble. Most likely, the first calcareous creatures were representatives of the flagellate family. Subsequently, nature ordered from them to create several species of plants and animals at once.

In the Proterozoic, multicellular organisms also formed from unicellular ones. For example, archaeocyaths or sponges.

Amazing Scorpio Cancers

The so-called crustacean scorpions were considered the most complex, but at the same time the most advanced living creatures of the Proterozoic. These predators were clad in a kind of armor, well armed and brought real terror to all living things. Even strong shells did not always save brachiopods or bivalves from formidable and predatory crustacean scorpions.

The body of these creatures was studded with long and very sharp spines, consisted of several segments, and had 6 pairs of limbs at once. The head and chest were completely hidden under a quadrangular shell, and 4 small eyes looked out at the world. At the end of the body of Scorpio cancers, both for defense and attack. Their sizes varied from 10 cm to 3 had a long straight needle connected to a poisonous gland. It was used for both defense and attack. Their sizes varied from 10 cm to 3 m in length.

Proterozoic era and minerals

Experts say that both marine and continental sediments of the Proterozoic are now widespread on all continents without exception. For thousands of years, rock destruction products accumulated in the troughs, forming strata of quartz sandstones, clays, carbonate rocks, etc.

At the end of the Proterozoic, molasse was deposited (for example, in the Urals). At the same time, deposits of iron ores and phosphorites appeared. In Equatorial Africa, Proterozoic rocks include the richest deposits of ores, copper, cobalt and uranium.

Beginning of the Ice Age

Modern research has pointed to another reason for glaciation. It is possible that the mass extinction of organisms on Earth occurred approximately 16 million years before the previously assumed glaciation. The uncontrolled growth of various types of algae could have a bad impact on marine ecosystems, since organic matter did not have time to decompose in the water column, and the algae could cover the entire surface of the water, thereby completely blocking the access of oxygen inside.

As a result, it turned out that aerobic marine life died out due to a lack of oxygen, which could lead to a reduction in carbon dioxide emissions and caused a sudden cooling. Although the traditional theory about the binding of carbon dioxide by silicates is not rejected.

If this had not happened, perhaps our development would have gone differently. The Proterozoic era actually served as the basis for the formation of everything that we have now in the reality around us.

As already mentioned, all currently known platforms and shields were formed in the Proterozoic. In the mid-Proterozoic, the ancient platforms were united into one supercontinent, Megagaia. In the Riphean, all the platforms of the southern hemisphere were united into one continent, Gondwana, and the platforms of the northern hemisphere (North American, East European, Siberian, Chinese) made up the continent of Laurasia.

The platform areas retained high tectonic mobility for a long time, and their relief remained quite contrasting and dynamic. The processes of erosion, transport and accumulation of sediments occurred quite intensively. On the leveled elevated areas, under the influence of exogenous processes, quite powerful weathering crusts arose, which is explained by the existence of high temperatures, large amounts of moisture and free oxygen in the atmosphere.

Thanks to the activity of algae in the Proterozoic, the atmosphere and hydrosphere were enriched with free oxygen, and an ozone screen arose, protecting the Earth from harsh radiation. The high content of carbon dioxide in the atmosphere influenced the formation of the greenhouse regime on the earth's surface. The climate, as at present, was mainly determined by solar radiation. The increase in the area of continents led to the division of the climate into marine and continental.

Along with indicators of humid and hot conditions in the Proterozoic era, there are indicators of arid and even cold types of climate. The few available factual data allow us to believe that the eras of dominance of an arid climate at certain periods of time were replaced by humid ones.

Noteworthy is the presence of typical glacial formations - tillites - among the Proterozoic strata. They have all the features of modern moraines and are found along with such undeniable indicators of ice activity as polished beds, “curly rocks,” “ram’s foreheads,” erratic boulders, glacial streaks, etc.

The most ancient formations resembling tillites are found among Archean strata within the Canadian Shield and in the southwestern part of Australia. However, reliable traces of possible glaciation of such an ancient age have not yet been discovered.

One of the first glaciations in the history of the Earth occurred about 2.5 billion years ago in the Proterozoic. Traces of this glaciation have been found in South Africa. They are represented by highly processed sediments of mountain glaciers. One of the largest glaciers was located in Canada.

Younger glacial deposits are 700-800 million years old. In Equatorial Africa, two glacial horizons were discovered in the Late Riphean. Glaciation, whose age is estimated at 740-780 million years, covered the territory of Angola, Zambia, Namibia and South Africa. The glacial formations of Australia, distributed from the southern to the northwestern parts of this continent, are of similar age.

Tillites have also been found in Europe, but they are younger. Their age is 650-670 million years. Tillites from West Africa, Australia, Southern and Central China are similar in age. This suggests that at the end of the Riphean, rather cold conditions established on Earth and vast areas were covered with thick glacial strata.

Based on the occurrence of packs of sedimentary rocks interbedded with tillites, it can be assumed that glacial epochs were repeatedly replaced by interglacial ones and, therefore, in this respect there are practically no differences between the Quaternary, Early Proterozoic and, especially, Vendian glaciations. Consequently, the glacial horizons of the Proterozoic should have been formed as a result of the action of fundamentally the same geological processes as moraine and genetically related deposits during the Quaternary glaciation.

So, in the Proterozoic there were glaciations, but during most of this time the Earth was quite hot. Evidence of a hot arid climate is found in the Riphean. These are red continental carbonate sandstones with desiccation cracks, dune cross-bedding, wind ripples and traces of wind erosion on the bedding surfaces. Along with them, there are strata formed in conditions of abundant moisture - various alluvial (floodplain, deltaic) deposits with characteristic cross-bedding, kaolinite clays, quartz sands, etc.

The ever-increasing processes of photosynthesis have led to a significant enrichment of the atmosphere and hydrosphere with free oxygen. This, in turn, affected not only the development of biological processes, but also the processes of weathering and sedimentation. The volume of iron ore formation is decreasing, and the places of their formation are gradually shifting to coastal and even continental areas. The appearance of atmospheric oxygen caused the transition of these compounds into oxide forms and sharply limited the migration abilities of iron and manganese. The areas of dolomite formation gradually decreased, and at the end of the Proterozoic they shifted to areas with a very dry climate.

The plant kingdom of the Riphean was dominated by algae (mainly blue-green). The animal kingdom was much less abundant, but was characterized by quite significant diversity in systematic terms.

The most numerous group of organisms throughout the Proterozoic were bacteria, which took an active part in the processes of decomposition, oxidation and even accumulation of various substances. The active participation of bacteria in rock formation contributed to the wide distribution of various ferruginous rocks, including sedimentary iron ores, graphite shales, high-carbon and high-alumina rocks. Probably, microorganisms played an important role in the weathering processes of rocks.

During the Proterozoic era, the main groups of algae developed - from primitive blue-greens to more highly organized ones. They played a leading role in the gradual removal of carbon dioxide from the atmosphere and an increase in free oxygen. Their rock-forming role is great, especially in the Riphean, when a variety of algal limestones and dolomites were widespread. Numerous stromatolites, oncolites and catagraphs are known from Riphean deposits - calcareous and dolomite nodules that arose as a result of the activity of algae.

Stromatolites are layered concretions of varying sizes in the form of growths, having loaf-shaped and columnar shapes. Oncoliths are concentric nodular formations, and catagraphs are irregularly shaped concretions without layering in the form of lumps. The concentric structure of stromatolites and oncolites is probably caused by the seasonal development of algae, similar to the growth rings of modern temperate trees. Lime was deposited around the threads and cells of the colonies.

Until recently, life in the Precambrian could only be judged by the remains of various algae, fungi, and bacteria. Biochemical and paleontological trends that have emerged in recent years have made it possible to discover numerous remains of organisms in Precambrian rocks. In the youngest complexes of Riphean formations, remains of the most ancient multicellular animals were discovered. The uniqueness of this fauna lies in the fact that, although it had significant diversity, it was represented by organisms that completely lacked mineral skeletal formations.

Currently, the non-skeletal fauna of the Late Precambrian has been discovered in the Ediacaran region in South Australia (therefore, the entire ancient fauna is often called Ediacaran), in Great Britain, in southwest Africa and Newfoundland, in the USSR - Podolsk Transnistria and Karelia.

The Ediacaran fauna consisted mainly of coelenterates - jellyfish, worms, arthropods and organisms, the systematic position of which is not yet clear. It played a big role in the development of the organic world, being the predecessor of the skeletal fauna, although it still did not have a direct and immediate continuation in the Paleozoic era. According to many researchers, the Ediacaran fauna was most likely a side branch of the evolution of organisms.

Soviet paleontologist M.A. Fedonkin discovered a huge amount of Vendian non-skeletal fauna on the shores of the White Sea. These organisms are represented by free-swimming and benthic (bottom) forms ranging in size from a few millimeters to 30 cm.

One of the features of the Vendian fauna is the presence of fossil remains among multicellular forms that resemble the larvae of modern invertebrates. In the strata of the Vendian rocks, remains were found that were very similar to the larvae of trilobites and echinoderms, but all of them were larger in size than those found in younger sediments.

The organic world of the Proterozoic mainly developed in a marine environment. The absence of a hard skeleton in organisms of the Late Proterozoic may have been caused by the high content of carbon dioxide in the atmosphere and hydrosphere. This led to a sharp increase in the solubility of lime and made it difficult to extract from water.

Proterozoic landscapes, especially in Riphean times, are more differentiated compared to Archean ones. Although the saturation of landscapes with organisms increased, the power of the biosphere remained small and was not widespread. The land was biologically a desert.

Thus, the paleogeographic conditions of the Proterozoic, even for the final stages of the Riphean and Vendian, appear in fairly general terms. By the end of the Proterozoic, the oxygen content in the atmosphere increased and amounted to 1-2%, an ozone screen was formed, which significantly reduced hard ultraviolet radiation, the salinity of ocean waters sharply increased and climatic zonality arose.