development of life on earth. The main stages of the evolution of flora and fauna The first organisms on earth biology message

Table 1

Era	Period (million years)	Vegetation and animal world
Archean, Proterozoic (beginning 4500 million years ago)	~3500	Life originated in the seas. (There are no fossil traces of the first animal beings.)
	The existence of unicellular marine organisms.
	Multicellular living beings appear in the seas.
Paleozoic (beginning 600 million years ago)	600-500	Countless vertebrates appear in the seas. Among the invertebrates we find the ancestors of the current mollusks and arthropods.
	The first marine vertebrate armored fish (already extinct) with a cartilaginous skeleton, shell.
	Modern fish appear. Life begins to develop on emerging land areas. The first land settlers are bacteria, fungi, mosses and small invertebrates, followed by amphibians (amphibians).
400-300	The land is covered with mighty forests of ferns and other plants that have died out by now. Insects are spreading.
	The origin of reptiles (reptiles).
Mesozoic (beginning 230 million years ago)	230-70	Age of reptiles. These animals are distributed not only on land areas emerging from the water, but also in the seas. Some of them reach enormous sizes.
230-190	Mammals are born. The first flowering plants spread: gymnosperms. Fern forests are disappearing.
	Birds are born. The first angiosperms appear (plants in which flowers have ovaries).
	Forests of gymnosperms over most of the land are being replaced by forests of angiosperms.
	Dinosaurs and other large reptiles are dying out.
Cenozoic (beginning 70 million years ago)	70-20	Mammals are distributed throughout environment, displacing reptiles, whose numbers are sharply declining. Birds are widely distributed.
70-50	Various classes of mammals are born: carnivores, bats, and the ancestors of modern apes and humans. Herbivores appear (e.g. cattle, deer, horses)
20-10	Some mammals (cetaceans) inhabit the seas.
	Australopithecus appears - the progenitor of man.
0,04-0,02	Some large mammals are disappearing (for example, mammoth, woolly rhinoceros, saber-toothed tiger). Man becomes the undivided master of the Earth.

The first era - Archean, lasting 900 million years, left almost no traces of organic life. The presence of rocks of organic origin - limestone, marble, carbonaceous substances - indicates the existence in the Archean era of bacteria and blue-green algae (cyanobacteria) - cellular pre-nuclear organisms. They live in the seas, but also come out on land.

Water is saturated with oxygen, and soil-forming processes take place on land. Bacteria did not give rise to the formation of new groupings and have remained isolated to this day. It was during the Archean era that three major changes occurred in the development of living organisms: the emergence of the sexual process, photosynthesis, and multicellularity. The sexual process arose in the form of a fusion of two identical cells in flagellates, which are considered the most ancient unicellular.

Later, the sexual process took place already with the help of special germ cells - male and female, which, when merged, form a zygote. An organism develops from it, containing the genotype of the father and mother, which gives a combination of various traits in the offspring, expanding the possibilities of action. natural selection. With the advent of photosynthesis, a single trunk of life was divided into two - plants and animals - due to divergence. Multicellularity caused a further complication of the organization of living organisms: the differentiation of tissues, organs, systems and their functions.

In the Proterozoic era (duration 2,000 million years), green algae develop, including multicellular ones. Remains of the animal world are rare and few in number. The ancestors of multicellular organisms were probably organisms similar to the colonial forms of unicellular flagellates, and the first multicellular animals were close to sponges and coelenterates.

Remains of all types of invertebrates, including echinoderms and arthropods, are known. It is believed that at the end of the Proterozoic era, primary chordates appeared - a subtype of non-cranial ones, the only representative of which in the modern fauna is the lancelet. Bilaterally symmetrical animals appear, sense organs develop, ganglions, the behavior of animals becomes more complicated, mobility and energy in the processes of life in general increase.

In the Paleozoic era, lasting 330 million years (ancient life), subdivided into several periods, further evolutionary transformations took place organic world. In the Cambrian period (570-490 million years ago), in addition to bacteria and unicellular algae, large multicellular algae were common. The Cambrian and Ordovician (490-435 million years ago) are characterized by the presence of fossil remains of protozoa, coelenterates, sponges, worms (three types), echinoderms, mollusks, arthropods, chordates.

The Silurian (435-400 million years ago) is rich in remains of fossil trilobites and especially brachiopods (at present there are about 200 species left). Remains of jawless vertebrates - scutes (ancestors of lampreys) were found. Further development of evolution continued along the path of divergence of types of the animal world with the replacement of low-organized primitive forms by more highly organized ones. At the end of the Silurian period, part of the green multicellular algae adapted to life on land. Perhaps they were psilophytes. They already had fabrics.

Mushrooms have appeared. From the middle of the Devonian (400-435 million years ago), psilophytes gradually decrease, disappearing by the end of this period. And they are replaced by club moss, horsetail and fern - spore plants. During the Devonian period, jawed armored fish appear (their descendants are modern cartilaginous fish, for example, sharks and rays), lungfish. However, another group of fish, the lobe-finned fish, made landfall. The most primitive terrestrial vertebrates are considered ancient amphibians, originating from one of the groups of lobe-finned.

Based hereditary variability in the process of natural selection, fins evolved into limbs for movement on land. Lungs evolved for breathing on land. The oldest amphibians - stegocephals (shell-headed) lived in marshy places. Stegocephalians combined the characteristics of fish, amphibians and reptiles. Devonian animals, like plants, lived in humid places, so they could not spread inland and occupy places remote from water bodies.

In the Carboniferous period (345-280 million years ago) there was a major evolutionary upsurge in the development of terrestrial vegetation. This period was characterized by a warm, humid climate. Huge forests formed on Earth, consisting of giant ferns, tree-like horsetail and club mosses - 15-30 m high. They had a good conducting system, roots, leaves, but their reproduction was still associated with water. The forests of the Carboniferous period formed coal deposits.

During this period, seed ferns also grew, in which seeds developed instead of spores. Seed ferns (the oldest gymnosperms) clearly indicate the origin of seed plants from spores. The appearance of seed plants was a major aromorphosis that determined the further evolution of plants. In seed plants, fertilization occurs already without the participation of water, and the embryo is in the seed, which has a supply of nutrients.

Since the end of the Carboniferous period, due to increased mountain building, the humid climate has almost everywhere been replaced by a dry one. Tree ferns began to die out, only in some damp places small forms were preserved. The seed ferns also died out. They were replaced by more viable gymnosperms, which, thanks to the distribution of seeds, have mastered arid habitats. The distribution and magnificent development of gymnosperms continued almost until the end of the Mesozoic era. In the Carboniferous period, there was an intensive development of insects, spiders, scorpions, which have air breathing and lay eggs with a protective shell that protects against drying out.

At the same time, trilobites began to disappear. There were many brachiopods, mollusks, fish (especially sharks), echinoderms, corals developed. Previously existing types and classes diverged, adapted to different habitats. With the onset of dry conditions at the end of the Carboniferous period, large amphibians disappear, only small forms remain in damp places. Amphibians were replaced by reptiles, more protected and adapted to existence in a drier climate on land.

The appearance of the most ancient reptiles is a new aromorphosis in the development of the animal world. Mostly they were herbivores, but some moved to a predatory lifestyle. Animal-toothed reptiles appeared, from whose descendants the first mammals are believed to have originated.

Animal-toothed lizards are a transitional form. Thus, in the Paleozoic era, namely in the Permian period (280-230 million years ago), plants and animals already came to land: these are vascular (spore and gymnosperms) plants, lobe-finned fish, amphibians, reptiles, arthropods (spiders, are thought to have appeared in the Silurian). The dry and warm climate of the Permian period contributed to their formation. The Archean, Proterozoic and Paleozoic eras provided a wealth of factual material on the basis of which one can judge the main directions of the evolution of the organic world.

In the Triassic period of the Mesozoic era, under the conditions of a continental climate, the development of gymnosperms intensified, in which fertilization took place already without the participation of water, which is the largest aromorphosis. The Mesozoic era is characterized by an unusually rich development of gymnosperms, which continued until the middle of the Cretaceous period, when, due to increasing drought and an increase in the brightness of the Sun, a recently emerged group of plants - angiosperms - comes to the fore. Dicotyledonous and monocotyledonous plants appeared already at the end of the Mesozoic, and in the Cretaceous period they begin to flourish.

Angiosperms are characterized by large aromorphosis - the appearance of a flower adapted to pollination. Idioadaptive changes in the flower contributed to numerous particular adaptations to pollination. Subsequently, the idioadaptation of the flower took place, as a result of which adaptations were developed for the distribution of fruits and seeds, as well as for reducing the evaporation of water by leaves. The magnificent development of angiosperms was simultaneously associated with the development of higher forms of arthropods (insects) pollinators: butterflies, bumblebees, bees, flies, etc.

The Mesozoic era (“the era of the dinosaurs”; discussed in more detail in Table 2) is characterized by the amazing development and subsequent very rapid extinction of giant reptiles. Giant lizards lived on land - dinosaurs, viviparous ichthyosaurs, crocodiles, flying lizards. Giant reptiles died out relatively quickly. The first small mammals appeared in the Triassic, their reproduction was already carried out by live birth, they fed their young with milk. They had a constant temperature and differentiated teeth.

The ancestors of mammals were animal-toothed lizards. The first birds arose in the Jurassic period of the Mesozoic era - they were toothy birds. And at the end of the Mesozoic, the first true birds appeared. Ancient cartilaginous fish in the Triassic were supplanted by true bony fish. As a result of divergence, species diversity has steadily increased within each systematic group.

Characteristics of the Mesozoic Era

table 2

Era (duration, million years)	Period (duration, million years)	Beginning (million years ago)	Climate and environment (global geographical changes)	Development of the organic world
Animal world	plant world
Mesozoic (middle life),	Triassic (Triassic), 40 ± 5	230±10	Weakening of climatic zonality, smoothing of temperature differences. The beginning of the movement of the continents.	The beginning of the heyday of reptiles - the "age of dinosaurs" begins; turtles, crocodiles, etc. appear. The appearance of the first mammals, real bony fish.	Ferns, horsetails, lycopsids are common. Seed ferns are dying out.
Jura (Yura),	190 - 195±5	The climate, initially humid, changes towards the end of the period to dry in the region of the equator. The movement of the continents, the formation of the Atlantic Ocean.	In the ocean, the emergence of new groups of molluscs, including cephalopods, as well as echinoderms. The dominance of reptiles on land, in the ocean and in the air. At the end of the period, the appearance of the first birds - Archeopteryx.	Ferns and gymnosperms are widespread, and a well-defined botanical and geographical zoning appears.
Cretaceous (Chalk),	136±5	In many regions of the Earth, the climate is cooling. A pronounced retreat of the seas, which was replaced by a vast increase in the area of the World Ocean and a new rise in land. Intensive mountain building processes (Alps, Andes, Himalayas).	The emergence of true birds, as well as marsupials and placental mammals. In reservoirs, the predominance of bony fish. The flowering of insects. Extinction of large reptiles and primitive Mesozoic mammals.	The number of ferns and gymnosperms is sharply reduced. The first angiosperms appear.

Cenozoic era ( new life) lasts approximately 60-70 million years. Its first period is the Paleogene, the second is the Neogene, and the third is the Anthropogen, which continues to the present. During this era, the continents and seas were formed in their modern form. In the Paleogene, angiosperms spread over all continents and freshwater bodies. In the second half of this period, rapid mining processes began. A cold snap has come, evergreen forests have been replaced by deciduous ones. There was a rapid idioadaptation of forms in various local conditions.

At the end of the Neogene - the beginning of the Anthropogen, glaciers advanced from the north, all living things died on the way of the sliding of glaciers, only those forms remained that could survive and adapt to the changed environmental conditions. Arctic flora developed. In the Anthropogen, the final formation of the modern flora. In the Cenozoic, gastropods and bivalves spread, and insects thrive among arthropods.

Large aromorphoses of insects - the development of the tracheal respiratory system, chewing type mouth apparatus, hard chitinous cover, jointed limbs and nervous system ensured their prosperity. Birds and mammals have occupied a dominant position in the animal world due to an increase in the intensity of the functions of the central nervous system (especially the functions of the brain), the complication of the structure of the circulatory system (separation of arterial and venous blood), a constant body temperature and an increase in the level of metabolic processes, etc. Rapid idioadaptation to changing environmental conditions ensured their prosperity.

Dinosaur skeletons have been found throughout human history, but our ancestors mistook them for the bones of dragons, griffins, and other mythical creatures. When scientists first encountered dinosaur remains in 1677, the director of one of British museums, Robert Plot, identified the pieces of bone as a fragment of the femur of a giant man. Myths about antediluvian giants developed for several hundred more years, until scientists learned how to accurately restore fossil remains and determine their age. The science of fossil animals is being improved today, applying latest methods research. Thanks to them, scientists can accurately restore the appearance of amazing creatures that walked the earth millions of years ago.

Exceptionally rich material for the development of evolutionary ideas was provided by the science of paleontology, which studies the history of life from the remains of organisms that have been preserved in rocks and sediments (see Fig. 1). Paleontology has recreated the main chronology of events that occurred mainly in the last 700 million years, when the evolution of life on our planet was especially intensive.

This part of the history of the development of the Earth is usually divided into large intervals, which are called eras. Eras, in turn, are divided into smaller intervals - periods. Periods - for epochs and centuries. The era names are Greek origin. For example, Mesozoic - "middle life", Cenozoic - "new life". Each era, and sometimes even a period, has its own characteristics in the development of the animal and plant world ().

For the first 1.5 billion years after the formation of our planet, living organisms did not exist on it. This period is called katarchey (Greek "below the most ancient"). Education took place in the Katharchea earth's surface, there were active volcanic and mountain-building processes. Life arose on the border of the Catarchean and the Archean era. This is evidenced by the finds of traces of vital activity of microorganisms in rocks aged 3.5-3.8 billion years.

Archean era lasted 900 million years and left almost no traces of organic life. The presence of rocks of organic origin: limestone, marble, carbon dioxide indicates the existence of bacteria and cyanobacteria, that is, prokaryotic organisms, in the Archean era (see Fig. 2). They lived in the seas, but, perhaps, went out on land as well. In Archaea, water is saturated with oxygen, and soil-forming processes take place on land.

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It was in the Archean era that three major changes occurred in the development of living organisms: the emergence of the sexual process, the emergence of photosynthesis, and the emergence of multicellularity ().

The sexual process arose as a result of the fusion of two identical cells in flagellates, which are considered the most ancient unicellular. With the advent of photosynthesis, a single trunk of life was divided into two - plants and animals. And multicellularity led to a further complication of life: tissue differentiation, the emergence of organs and organ systems (see Fig. 3).

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In the Proterozoic era lasting 2 billion years, algae develop - green, brown, red (see Fig. 4), and fungi also appear.

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The ancestors of multicellular organisms may have been colonial organisms like modern colonial flagellates (see Fig. 5). And the first multicellular organisms were like modern sponges and corals (see Fig. 6).

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The fauna of that period was represented by all types of invertebrates (see Fig. 7).

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It is believed that at the end of the Proterozoic era, primary chordates, a subtype of non-cranial, appeared, the only representative of which in the modern fauna is the lancelet (see Fig. 8).

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Bilateral symmetrical animals appear, sense organs, nerve nodes develop, and the behavior of animals becomes more complicated (see Fig. 9).

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The Paleozoic era began 570 million years ago and was characterized by the most important evolutionary events in the history of the development of organic life on Earth (). At the beginning of this era, a significant part of the Earth's land was formed, the formation of the ozone screen ended, which made it possible for the first plants, rhyniophytes, to come to earth about 400 million years ago (see Fig. 10, 11). They, unlike algae, already possessed conductive, integumentary and mechanical tissues; allowing to exist in the conditions of the ground-air environment. Then the main groups of higher spore plants originated from rhinophytes: lycopods, horsetails and ferns, from which primary forests were formed () (see Fig. 12).

During the Carboniferous period, there was a major evolutionary upsurge in the development of terrestrial vegetation.

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This period was characterized by a warm, humid climate. On Earth, huge terrestrial forests were formed, consisting of giant ferns, tree-like horsetails and club mosses from 15 to 20 m high.

They had a good conducting system, roots, leaves, but their reproduction was still associated with water. During this period, seed ferns grew, which developed seeds instead of spores (see Fig. 13). The appearance of seed plants was the largest aromorphosis in the history of the development of the Earth, since the reproduction of seed plants no longer depended on water. The embryo is located in the seed and is provided with a supply of nutrients.

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Since the end of the Carboniferous period, due to the active mountain-building process, the humid climate everywhere becomes dry. Tree ferns are dying out, leaving only their small forms in damp places. Seed ferns are also dying out. The forests of the Carboniferous period led to the formation of coal deposits.

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In the development of the animal world in the Paleozoic (see Fig. 14), the most important evolutionary events also took place. At the beginning of the era, the first vertebrates appeared - armored fish. They possessed an internal skeleton that gave them an advantage in movement compared to invertebrates. Cartilaginous and bony fish then evolved from armored fish (see Fig. 15). Among the bony fish, the lobe-finned fish stood out, from which the first terrestrial vertebrates originated about 300 million years ago.

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The most primitive terrestrial vertebrates are considered to be ancient amphibians - stegocephals, which lived in marshy places (see Fig. 16, 17). Stegocephals combined the signs of fish and amphibians ().

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Animals of this period, like plants, lived in humid places, so they could not spread inland and occupy places remote from water bodies. With the onset of dry conditions at the end of the Carboniferous period, large amphibians disappear, only small forms remain in damp places.

Amphibians were replaced by reptiles (see Fig. 18). More protected and adapted to existence in a dry climate on land, all reptiles, unlike amphibians, have skin protected from drying out with horny scales. Their reproduction is no longer associated with water, and the eggs are protected by dense shells.

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The Mesozoic era began about 230 million years ago. Climatic conditions were favorable to further development life on our earth. Gymnosperms dominated on land at that moment, but about 140 million years ago, the first angiosperms, or flowering plants, already arose ().

The seas were dominated by cephalopods and bony fish (see Fig. 19). Giant lizards lived on land - dinosaurs, as well as viviparous ichthyosaurs, crocodiles, flying lizards (see Fig. 20, 21).

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But giant reptiles died out relatively quickly. At the beginning of the Mesozoic, about 200 million years ago, the first birds originated from a group of ornithischian reptiles (see Fig. 22), and the first mammals originated from a group of animal-like reptiles (see Fig. 23).

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A high level of metabolism, warm-bloodedness, a developed brain allowed birds and mammals to occupy a dominant position on our planet.

The Cenozoic era began 67 million years ago and continues to the present day. After the Pleogen and Neogene, the third period of the era began - the Anthropogen, in which we now live.

During this era, the seas and continents took shape in their present form. In the Pleogen, angiosperms spread throughout the land and in freshwater reservoirs, active mountain-building processes took place, as a result of which the climate became colder. This has led to the replacement of evergreen forests by deciduous forests. In the anthropogen, the modern flora and fauna finally formed, a person arose ().

Paleontology

Paleontology is a science that studies the history of the development of life on Earth according to the remains, imprints and traces of the vital activity of ancient living organisms preserved in sedimentary rocks. Scientific paleontology arose at the end of the 18th century. Georges Leopold Cuvier is considered its founder (Fig. 24).

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For more than 200 years of its existence, paleontology has accumulated a huge amount of material about ancient plants and animals, many of which are completely different from modern life forms.

Paleontologists study not only the remains of ancient plants and animals, but also fossils, that is, the bodies or fragments of the bodies of ancient living organisms in which organic matter over time were replaced by mineral salts. Paleontology also uses the methods of paleoecology and paleoclimatology to recreate the living conditions under which ancient organisms existed. Recently, paleontology has received a new development due to the fact that the methods of computed tomography, digital microscopy, and molecular biology have become available to it. With the help of these discoveries, it was possible to prove that life on our planet is much older than it seemed before.

Geochronology

For convenience of study and description, the entire history of the Earth is divided into certain periods of time. These intervals differ in duration, mountain building processes, climate, flora and fauna. In the geochronological record, these periods are characterized by different layers of sedimentary rocks with fossil remains preserved in them. The deeper the sedimentary layer lies, the older the fossil in it. The largest divisions of the geological record are eons. There are two eons: cryptozoic, which in Greek means "secret life", and phanerozoic - "manifest life". Eons are divided into eras. There are two eras in the Cryptozoic: the Archean and the Proterozoic. And in the Phanerozoic - three eras: Paleozoic, Mesozoic and Cenozoic. Eras are in turn divided into periods, which may have smaller subdivisions.

The importance of photosynthesis in the development of life on Earth

The appearance of autotrophic organisms on Earth led to gigantic changes in its development. First, the appearance and vital activity of plants led to the formation of free oxygen in the atmosphere of our Earth. The presence of free oxygen changed biochemical processes, which led to the death of many living organisms, for which free oxygen was fatally toxic. But, on the other hand, the presence of free oxygen in the atmosphere allowed living organisms to master the process of respiration, as a result of which much more energy is accumulated in the form of an ATP molecule. Such an energetically more favorable way of breathing allowed living organisms to subsequently master the land. In addition, under the influence of ultraviolet radiation, oxygen was converted into ozone. Thanks to this process, a protective ozone screen was formed, which does not allow hard ultraviolet radiation to reach the Earth. This was another reason why living organisms were able to go to land. In addition, autotrophs themselves have become more high-energy food for heterotrophs. The interaction of autotrophs and heterotrophs, their birth and death led to the most important process of the emergence of the biological cycle of substances. Thanks to this, the once lifeless shell turned into a biosphere inhabited by living organisms.

Bibliography

Mamontov S.G., Zakharov V.B., Agafonova I.B., Sonin N.I. Biology. General patterns. - M.: Bustard, 2009.
Pasechnik V.V., Kamensky A.A., Kriksunov E.A. Biology. Introduction to general biology and ecology. Textbook for 9 cells. 3rd ed., stereotype. - M.: Bustard, 2002.
Ponomareva I.N., Kornilova O.A., Chernova N.M. Fundamentals of General Biology. Grade 9: Textbook for students in grade 9. educational institutions / Ed. prof. I.N. Ponomareva. - 2nd ed., revised. - M.: Ventana-Graf, 2005.

Homework

List the sequence of eras in the development of the Earth.
What era are we living in?
Could our species not have dominated the Earth?
What happened to animals and plants that arose in the Mesozoic?

There is a whole complex of sciences that study the main stages of the development of life on Earth, they all consider this issue in many ways, because this is a fundamental problem of natural science. The significance of paleontology, which studies the remains of plants and animals of past eras, is very important; it is directly related to the study of the evolution of the world.

This science studies the main ones by reconstructing the appearance, external similarities and differences, the way of life of prehistoric, already extinct animals and plants, and also determines the approximate time of existence of a particular species. But paleontology could not exist as a separate science without many others that support it; this science is at the intersection of biological and geological disciplines. The main stages of the development of life on Earth are recreated with the help of disciplines such as:

historical geology;
stratigraphy;
paleography;
comparative anatomy;
paleoclimatology and many others.

All of them are interconnected; without one, the others cannot exist.

Geological time

To single out the main stages in the development of life on Earth, it is necessary to have an idea of such a concept as geological time. How did people manage to identify some time stages? The whole secret lies in the study of rocks. The fact is that the rocks that arose at a later time are superimposed on top of those that existed earlier. And the age of these layers can be determined by studying the fossils remaining in them.

Among all their diversity, the so-called guiding fossils stand out, which are the most numerous and widespread. Unfortunately, with the help of rocks it is impossible to establish the absolute age, but even here scientists do not stop, extracting this knowledge from volcanic rocks. As you know, they arise from magma. This is how the main stages of the development of life on earth are distinguished.

Briefly, the process of determining the absolute age of volcanic rocks looks like this: igneous rocks contain some elements, if you determine their content in the rock, then you can accurately determine the absolute age of the rock. Of course, errors are possible, but they do not exceed five percent. In addition, the age of our planet is also determined, all scientists adhere to their figures, but the generally accepted value is five billion years. Now we will highlight the main stages, which will be a good helper in this case.

Eras, eras and periods

In total, paleontologists distinguish five stages or, in other words, eras, each of which is divided into periods, all of which consist of eras, and the last of centuries. The Archean and Proterozoic eras are the most ancient times, covering about three billion years. They are distinguished by the complete absence of vertebrates and terrestrial plants, which appear in the "era of ancient life", which spans more than three hundred million years. Next comes the "era of middle life", the Mesozoic (one hundred and seventy-five million years), its distinctive features are the development of reptiles, birds, mammals, plants, both flowering and angiosperms.

The latest, fifth, era is the Cenozoic, also called the "era of new life", it began seventy million years ago, and we are still living in it. characterized by the rapid development of mammals and the appearance of man. Now we have analyzed the stages of the development of life on Earth briefly, we propose to consider each era separately.

Archean era

This stage covers the period from three thousand nine hundred to two thousand six hundred million years ago. Part of the sedimentary rocks, that is, formed with the help of particles of the aquatic environment, remained in Africa, Greenland, Australia and Asia. All of them contain:

biogenic carbon;
stromatolites;
microfossils.

At the same time, the origin of the latter in this era is not entirely clear; for example, in the Proterozoic they are associated with cyanobacteria. In the Archean era, all organisms were classified as prokaryotes, and sulfates, nitrates, nitrites, and so on served as a source of oxygen. All existing organisms on the planet outwardly resembled mold films, mainly located at the bottom of reservoirs, in volcanic areas.

Proterozoic era

It is important to mention that this era is also divided into three periods. In addition, this is the longest period of our history (approximately two million years). If we consider the turn of this era and the Archean, then it was during this period that our planet changed a lot, land and water expanses were redistributed. The earth was an icy desert, but at the end of this period, the percentage of oxygen reached one percent, which contributed to the sustainable life of unicellular organisms, bacteria and algae developed.

At the end of the Proterozoic, multicellular animals formed, this period is also called the “age of jellyfish”. For changing unicellular organisms come multicellular, which qualitatively change the composition of the atmosphere, which contributes to the development of life on our planet.

Paleozoic

It includes as many as six periods, the first half is called the early Paleozoic, and the second - late. The early and late Paleozoic differ in animal and plant life.

At the first stage, evolution can be traced exclusively in underwater world, land settlement began only in the Devonian, which belongs to the late Paleozoic.

Mesozoic era

We are now moving into a most interesting era, rich in mystery and diversity of life, evolving over a period of some one hundred and eighty-five million years. As can be seen from the table, it is also divided into three periods. The Cretaceous, compared with the Jurassic and Triassic, is the longest (seventy-one million years).

As for the climate, it all depends on the location of the continents. Differences from our climate are that:

it was much warmer than today;
there were no temperature differences between the equators and the poles.

In addition, the air was humid, which contributed to the rapid development of living organisms.

If we turn to fauna, then the most unique group is the well-known dinosaurs. They have taken a dominant position over other forms of life due to the structure of their body, physiological data and reaction.

So, analyzing the question of what are the main stages in the development of life on Earth, we have identified five stages. To complete the picture, it remains to consider one more. We suggest you get started right now.

Cenozoic era

This new era which continues to this day. The continents have acquired a modern look, the last dinosaurs have disappeared, plants and animals that are quite familiar to us predominate on Earth. We briefly reviewed the main stages in the development of life on Earth, analyzed all the stages separately, and our goal has been achieved.

archaeus- ancient life. It lasted about 900 million years, from 3500 to 2600 million years. Little remains of organic life. Archean rocks contain a lot of graphite, it is believed that graphite was formed from the remains of living organisms. Discovered stromatolites- cone-shaped calcareous formations of biogenic origin. Many reserves of sulfur, iron, copper, nickel, and cobalt are of bacterial origin. Archaean living organisms were first represented by anaerobic prokaryotes, later blue-green ones appear. Photosynthesis of blue-greens is the most important aromorphosis of the Archean era. Thanks to their vital activity, the atmosphere is enriched with oxygen.

Proterozoic era.

Proterozoic- the era of primary life. The duration is from 2600 million years to 570 million years, that is, about 2 billion years. The surface of the planet was a bare desert, life developed mainly in the seas. This longest era is characterized by the formation of the largest deposits of iron ores formed due to the activity of bacteria. In the Proterozoic era, fundamental aromorphoses occurred:

In this era, all sections of algae are formed, the thallus of many becomes lamellar. The animals of that time were characterized by the absence of skeletal formations, the end of the Proterozoic is sometimes called "age of jellyfish". Annelids appear, from which mollusks and arthropods originated. The amount of oxygen in the atmosphere has reached 1% of the current level.

Paleozoic- the era of ancient life, the duration of which is from 570 to 230 million years. In this era, significant aromorphoses occur in the plant and animal world, associated both with life in water and with the development of land. It is divided into six periods: Cambrian, Ordovician, Silurian, Devonian, carbon, Permian.

Cambrian and Ordovician plants inhabit the seas and are represented by all divisions of algae. In the Silurian period (440 million years ago), in the zone of ebb and flow from green plants, the first terrestrial higher plants appear - psilophytes(naked plants) (Fig. 361). The appearance of integumentary, mechanical, conductive tissues were those aromorphoses that helped plants to enter the air. Psilophytes still lack roots, they absorb water and mineral salts with the help of rhizoids. Scales on the stem of psilophytes increased the surface of photosynthesis.

In the Devonian, ferns appear - herbaceous and tree-like horsetails, club mosses, ferns. The appearance of roots and leaves provided sufficient air and mineral nutrition for a variety of ferns. Ferns reproduce by unicellular spores; in moist places, they develop outgrowths that form germ cells. Water is needed for fertilization, an adult plant develops from the zygote.

A warm and humid tropical climate is established in the Carboniferous. Ferns reach gigantic sizes - up to 40 m in height. Carboniferous forests subsequently led to the formation of huge deposits of coal. At the same time, two most important aromorphoses occur in the Carboniferous, as a result of which higher seed plants appeared: firstly, pollination appears with

with the help of wind, when pollen with male germ cells through the air falls on plant organs containing female germ cells, water is no longer needed for fertilization; secondly, after fertilization, seeds are formed. These plants were seed ferns.

Seed ferns gave rise to the development of gymnosperms. In the Permian period, the climate became arid and colder. Tropical forests remain near the equator; gymnosperms spread to the rest of the territory.

Animals of the Cambrian period are characterized by a variety of trilobites - the oldest arthropods; in this period, animals with a mineralized skeleton appear.

In the Ordovician period, the first chordate animals with an internal skeleton appear, the distant descendants of which are lancelets and cyclostomes - lampreys and hagfishes.

In the Silurian seas, echinoderms and jawless armored "fish" appear, which only superficially resembled real fish and did not have jaws. Capturing and holding large prey with the help of such a mouth was impossible. The first arthropods - scorpions and spiders - come to land.

In the Devonian, insects appeared on land, real fish already swam in the seas - cartilaginous (sharks) and fish with a bone skeleton. As a result of mutations and selection, the third pair of gill arches turned into jaws, with the help of which it was possible to feed on large prey.

The most interesting among bony fish were lungfish and freshwater lobe-finned fish, which had lungs along with gills. warm water and the abundance of fresh water vegetation served as prerequisites for the development of additional respiratory organs, the pharyngeal pockets of lungfish and lobe-finned animals gradually turn into lungs. Freshwater lobe-finned fish also had powerful paired limbs (Fig. 362) and were better adapted to life in shallow coastal waters, and stegocephals (shell-headed amphibians) originated from them (Fig. 363).

In the Carboniferous, winged insects appeared on land, some dragonflies had a wingspan of up to 70 cm. The abundance of arthropods on land caused the appearance of a large number of different forms of ancient amphibians (up to 6 m in length).

Further development of land led to the appearance of reptiles and was accompanied by a number of aromorphoses: the surface of the lungs increased, dry scaly skin protected from evaporation, internal fertilization and the laying of large eggs allowed embryos to develop on land.

In the Permian, climate change was accompanied by the disappearance of stegocephalians and the spread of reptiles.

Mesozoic era.

Mesozoic- the era of middle life, began 230, ended 67 million years ago. It is divided into three periods: Triassic, Jurassic and Cretaceous. The vegetation of the first two periods of the Mesozoic era was represented by gymnosperms and ferns, and the extinction of tree-like ferns continued. At the beginning of the Cretaceous period (130 million years ago), the first angiosperms appeared. The appearance of a flower and a fruit are large aromorphoses that led to the appearance of angiosperms. With the help of a flower, the process of pollination was facilitated, the ovules located inside the ovary of the pistil were better preserved. The walls of the pericarp protected the seeds and contributed to their spread.

Rice. 364. Archeopteryx.

In the animal world of the Mesozoic era, insects and reptiles reach the greatest distribution. In the Triassic, reptiles return to the water for the second time, plesiosaurs live in shallow water, and ichthyosaurs resembling modern dolphins hunt far from the coast. The first egg-laying mammals appear, unlike reptiles, the high metabolic rate allows them to maintain a constant body temperature.

In the Jurassic period, some herbivorous reptiles reach gigantic sizes, and very large predatory dinosaurs appear - tyrannosaurs, whose body length reached 12 meters. Some reptiles master the airspace - flying lizards (pterosaurs) appear. In the same period, the first birds also appear, Archeopteryx (the size of a dove) retains many signs of reptiles - its jaws have teeth, three fingers protrude from the wing, the tail consists of a large number vertebrae (Fig. 364).

At the beginning of the Cretaceous period, the dominance of reptiles on land, in water and in the air remains, some herbivorous reptiles reach a mass of 50 tons. Marsupial and placental mammals appear, the parallel evolution of flowering plants and pollinating insects continues. At the end of the Cretaceous period, the climate becomes cold and arid. The area occupied by vegetation is reduced, giant herbivorous, then predatory dinosaurs die out. At the end of the Mesozoic era, some mammals from the order of insectivores began to lead an arboreal lifestyle, from them at the beginning of the Cenozoic era, ancestral forms of primates appeared.

Cenozoic era.

Cenozoic- the era of new life. It lasts 67 million years and is divided into two unequal periods - Tertiary (Paleogene and Neogene) and Quaternary (Anthropogenic). In the first half of the Tertiary period (in the Paleogene), a warm tropical climate was again established in most of the Earth, in the second half (Neogene), tropical forests were replaced by steppes, and monocotyledonous plants spread. In the Quaternary period, which lasts about 1.5 million years during the ice age, Eurasia and North America were subjected to glaciation four times.

As a result of the steppe stepping that took place in the second half of the Tertiary period, part of the primates was forced to descend to the ground and adapt to life on open spaces. These were the ancestral forms of humans - hominids, upright primates. The other part remained to live in the rainforests and became ancestors great apes - pongid. At the end of the Tertiary period, ape-men appear from hominids, pithecanthropes.

In the Quaternary period, the cold climate led to a decrease in the level of the world ocean by 60 - 90 m, glaciers formed and descended to the south, the thickness of which reached tens of meters, the water evaporated, but did not have time to melt. Land bridges were formed between Asia and North America, between Europe and the British Isles. These land bridges were used for animal migration from continent to continent. About 40 thousand years ago, along the Bering Bridge, ancient people left Asia for North America. As a result of a cold snap and the appearance of a man who hunted animals, many large animals disappear: saber-toothed tigers, mammoths, woolly rhinos. Near the sites of ancient people, the remains of many dozens of mammoths and other large animals are found. In connection with the extermination of large animals 10 - 12 thousand years ago, man was forced to move from gathering and hunting to agriculture and cattle breeding.

The development of life on Earth - the concept and types. Classification and features of the category "Development of life on Earth" 2017, 2018.

The origin of life on Earth occurred about 3.8 billion years ago, when education ended earth's crust. Scientists have found that the first living organisms appeared in the aquatic environment, and only after a billion years did the first creatures come to the surface of the land.

The formation of terrestrial flora was facilitated by the formation of organs and tissues in plants, the ability to reproduce by spores. Animals also evolved significantly and adapted to life on land: internal fertilization, the ability to lay eggs, and pulmonary respiration appeared. An important stage of development was the formation of the brain, conditioned and unconditioned reflexes, survival instincts. The further evolution of animals provided the basis for the formation of humanity.

The division of the history of the Earth into eras and periods gives an idea of the features of the development of life on the planet in different time periods. Scientists identify particularly significant events in the formation of life on Earth in separate periods of time - eras, which are divided into periods.

There are five eras:

Archean;
Proterozoic;
Paleozoic;
Mesozoic;
Cenozoic.

The Archean era began about 4.6 billion years ago, when the planet Earth only began to form and there were no signs of life on it. The air contained chlorine, ammonia, hydrogen, the temperature reached 80 °, the radiation level exceeded the permissible limits, under such conditions the origin of life was impossible.

It is believed that about 4 billion years ago our planet collided with celestial body, and the result was the formation of the Earth's satellite - the Moon. This event became significant in the development of life, stabilized the axis of rotation of the planet, contributed to the purification of water structures. As a result, the first life originated in the depths of the oceans and seas: protozoa, bacteria and cyanobacteria.

The Proterozoic era lasted from about 2.5 billion years to 540 million years ago. Remains of unicellular algae, mollusks, annelids were found. Soil is starting to form.

The air at the beginning of the era was not yet saturated with oxygen, but in the process of life, the bacteria that inhabit the seas began to release more and more O 2 into the atmosphere. When the amount of oxygen was at a stable level, many creatures took a step in evolution and switched to aerobic respiration.

The Paleozoic era includes six periods.

Cambrian period(530 - 490 million years ago) is characterized by the emergence of representatives of all types of plants and animals. The oceans were inhabited by algae, arthropods, mollusks, and the first chordates (Haikouihthys) appeared. The land remained uninhabited. The temperature remained high.

Ordovician period(490 - 442 million years ago). The first settlements of lichens appeared on land, and the megalograpt (a representative of arthropods) began to come ashore to lay eggs. Vertebrates, corals, sponges continue to develop in the thickness of the ocean.

Silurian(442 - 418 million years ago). Plants come to land, and rudiments of lung tissue form in arthropods. The formation of the bone skeleton in vertebrates is completed, sensory organs appear. Mountain building is underway, different climatic zones are being formed.

Devonian(418 - 353 million years ago). The formation of the first forests, mainly ferns, is characteristic. Bone and cartilaginous organisms appear in water bodies, amphibians began to land on land, new organisms are formed - insects.

Carboniferous period(353 - 290 million years ago). The appearance of amphibians, the sinking of the continents, at the end of the period there was a significant cooling, which led to the extinction of many species.

Permian period(290 - 248 million years ago). The earth is inhabited by reptiles, therapsids appeared - the ancestors of mammals. The hot climate led to the formation of deserts, where only resistant ferns and some conifers could survive.

The Mesozoic era is divided into 3 periods:

Triassic(248 - 200 million years ago). The development of gymnosperms, the appearance of the first mammals. The division of land into continents.

Jurassic period(200 - 140 million years ago). The emergence of angiosperms. The emergence of the ancestors of birds.

Cretaceous period(140 - 65 million years ago). Angiosperms (flowering) became the dominant group of plants. The development of higher mammals, real birds.

The Cenozoic era consists of three periods:

Lower Tertiary period or Paleogene(65 - 24 million years ago). The disappearance of most cephalopods, lemurs and primates appear, later parapithecus and dryopithecus. The development of the ancestors of modern mammalian species - rhinos, pigs, rabbits, etc.

Upper Tertiary or Neogene(24 - 2.6 million years ago). Mammals inhabit land, water and air. The emergence of Australopithecus - the first ancestors of humans. During this period, the Alps, the Himalayas, the Andes were formed.

Quaternary or Anthropogene(2.6 million years ago - today). A significant event of the period is the appearance of man, first Neanderthals, and soon Homo sapiens. The flora and fauna have acquired modern features.