The historical development of life on earth is brief. The main stages of the development of life on Earth. Characteristics of the Mesozoic Era
History of the development of Life on Earth
Paleontology - a science that studies the history of living organisms on Earth, based on preserved remains, prints and other traces of their life activity.
DEVELOPMENT OF LIFE ON EARTH
CRYPTOSOE (hidden life)About 85% of the total existence of life on Earth
ARCHAY
(ancient)
near
3500 million
(duration about 900 million)
Active volcanic activity. Anaerobic living conditions in a shallow ancient sea. Development of an oxygen-containing atmosphere
The emergence of life on Earth. The era of prokaryotes: bacteria and cyanobacteria. The appearance of the first cells (prokaryotes) - cyanobacteria. The emergence of the process of photosynthesis, the appearance of eukaryotic cells
Aromorphoses: appearance of a formed nucleus, photosynthesis
PROTEROZOIC
(primary life)
about 2600 million (duration about 2000 million)
longest in Earth's history
The surface of the planet is a bare desert, the climate is cold. Active formation of sedimentary rocks. At the end of the era, the oxygen content in the atmosphere is about 1%. Land - a single supercontinent
( Pange I ) The process of soil formation.
The emergence of multicellularity and the process of respiration. All types of invertebrate animals arose. Protozoa, coelenterates, sponges, and worms are widespread. The most common plant species are unicellular algae.
Aromorphoses in animals: the appearance of multicellularity, 2-way symmetry of the body, muscles, body segmentation.
PHANEROSOIC
(explicit life)
PALEOZOIC
(ancient life)
Duration approx. 340 million
Cambrian
OK. 570 million
dl. 80 million
First a moderate humid climate, then a warm dry climate. The land split into continents
The flourishing of marine invertebrates, most of which are trilobites (ancient arthropods), about 60% of all species of marine fauna. The appearance of organisms with a mineralized skeleton. Emergence multicellular algae
Ordovician
OK. 490 million
dl. 55 million
Moderate humid climate with a gradual increase in temperatures. Temperatures. Intensive mountain building, liberation of large areas from water
The appearance of the first jawless vertebrates (chordates). A variety of cephalopods and gastropods, a variety of algae: green, brown, red. Appearance coral polyps
Silur
OK. 435 million
dl. 35 million
Intensive mountain building, emergence of coral reefs
Lush development of corals and trilobites, crustacean scorpions appear, wide distribution of armored agnathans (the first true vertebrates), the appearance of echinoderms, the first land animals -arachnids . Exit to sushi plants, the first land plants( psilophytes )
Devonian
OK. 400 million
dl. 55 million
Climate: alternation of dry and rainy seasons. Glaciation on the territory of modern South America And South Africa
Age of fish: The appearance of fish of all systematic groups (nowadays you can find: coelacanth (lobe-finned fish), protoptera (lungfish)), the extinction of a significant number of invertebrates and most jawless animals, the appearance of ammonites-cephalopods with spirally twisted shells. The development of land by animals: spiders, ticks. The appearance of terrestrial vertebrates -stegocephalians (shell-headed )(the first amphibians; descended from lobe-finned fish) Development and extinction of psilophytes. The emergence of spore-forming plants: lycophytes, horsetail-like plants, fern-like plants. The emergence of mushrooms
Carbon
(Carboniferous period)
OK. 345
million
dl. 65 million
Worldwide distribution of swamps. The warm, humid climate gives way to cold and dry climates.
The flourishing of amphibians, the appearance of the first reptiles -cotylosaurs , flying insects, reduction in the number of trilobites. On land - forests of spore plants, the appearance of the first conifers
Permian
280 million
Dl. 50 million
Climate zonation. Completion of mountain building, retreat of the seas, formation of semi-enclosed reservoirs. Reef formation
Fast development reptiles, the emergence of animal-like reptiles. Extinction of trilobites. Disappearance of forests due to the extinction of tree ferns, horsetails and mosses. Permian extinction (96% of all marine species, 70% of terrestrial vertebrates)
During the Paleozoic, an important evolutionary event occurred: the settlement of land by plants and animals.
Aromorphoses in plants: appearance of tissues and organs (psilophytes); root system and leaves (ferns, horsetails, mosses); seeds (seed ferns)
Aromorphoses in animals: formation of bony jaws (gnatostome armored fish); five-fingered limb and pulmonary respiration (amphibians); internal fertilization and accumulation of nutrients (yolk) in the egg (reptiles)
MESOZOIC
(middle life) era of reptiles
Triassic
230 million
Length: 40 million
Supercontinent split
(Laurasia, Gondwana) movement of continents
The heyday of reptiles is the “age of dinosaurs”, turtles, crocodiles, and tuataria appear. The emergence of the first primitive mammals (ancestors were ancient toothed reptiles), true bony fish. Seed ferns are dying out, ferns, horsetails, lycophytes are common, gymnosperms are widespread
Yura
190 million
Length 60 million
The climate is humid, then changes to arid at the equator, the movement of continents
The dominance of reptiles on land, in the ocean and air, (flying reptiles - pterodactyls) the appearance of the first birds - Archeopteryx. Ferns and gymnosperms are widespread
Chalk
136 million
Dl. 70 million
Cooling of the climate, retreat of the seas, is replaced by an increasesocean
The appearance of true birds, marsupials and placental mammals, the flourishing of insects, angiosperms appear, a decrease in the number of ferns and gymnosperms, the extinction of large reptiles
Aromorphoses of animals: the appearance of a 4-chambered heart and warm-bloodedness, feathers, more developed nervous system, increasing the supply of nutrients in the yolk (poultry)
Carrying babies in the mother's body, feeding the embryo through the placenta (mammals)
Aromorphoses of plants: the appearance of a flower, protection of the seed by shells (angiosperms)
Cenozoic
Paleogene
66 million
dl. 41 million
A warm, uniform climate is established
Fish are widespread, many cephalopods are dying out, on land: amphibians, crocodiles, lizards, many orders of mammals appear, including primates. Insect bloom. The dominance of angiosperms, tundra and taiga appear, numerous idioadaptations appear in animals and plants (for example: self-pollinating, cross-pollinating plants, a variety of fruits and seeds)
Neogene
25 million
length 23 million
Movement of continents
Dominance of mammals, common: primates, ancestors of horses, giraffes, elephants; saber-toothed tigers, mammoths
Anthropocene
1.5 million
Characterized by repeated climate changes. Major glaciations Northern Hemisphere
The emergence and development of man, flora and fauna acquire modern features
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 an aquatic environment, and only after a billion years did the first creatures emerge on the surface of the land.
The formation of terrestrial flora was facilitated by the formation of organs and tissues in plants and 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 in development was the formation of the brain, conditioned and unconditioned reflexes, and survival instincts. The further evolution of animals provided the basis for the formation of humanity.
Dividing 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 planet Earth was just beginning to form and there were no signs of life on it. The air contained chlorine, ammonia, hydrogen, the temperature reached 80°, the level of radiation exceeded 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 consequence was the formation of the Earth’s satellite, the Moon. This event became significant in the development of life, stabilized the planet’s rotation axis, and contributed to the purification of water structures. As a result, the first life arose in the depths of the oceans and seas: protozoa, bacteria and cyanobacteria.
The Proterozoic era lasted from approximately 2.5 billion years ago to 540 million years ago. Remains of unicellular algae, mollusks, annelids. Soil begins to form.
The air at the beginning of the era was not yet saturated with oxygen, but in the process of life, bacteria inhabiting the seas began to increasingly release 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.
Palaeozoic includes six periods.
Cambrian period(530 – 490 million years ago) is characterized by the emergence of representatives of all species of plants and animals. The oceans were inhabited by algae, arthropods, and 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 megalograptus (a representative of arthropods) began to come ashore to lay eggs. In the depths of the ocean, vertebrates, corals, and sponges continue to develop.
Silurian(442 – 418 million years ago). Plants come to land, and the rudiments of lung tissue form in arthropods. The formation of the bone skeleton in vertebrates is completed, and sensory organs appear. Mountain building is underway and 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 reservoirs, amphibians began to come to land, and new organisms—insects—are formed.
Carboniferous period(353 – 290 million years ago). The appearance of amphibians, the subsidence 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, the ancestors of mammals, appeared. The hot climate led to the formation of deserts, where only hardy ferns and some conifers could survive.
The Mesozoic era is divided into 3 periods:
Triassic(248 – 200 million years ago). Development of gymnosperms, appearance of the first mammals. The split of land into continents.
Jurassic period(200 - 140 million years ago). The emergence of angiosperms. The appearance of the ancestors of birds.
Cretaceous period(140 – 65 million years ago). Angiosperms (flowering plants) became the dominant group of plants. Development of higher mammals, true 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 mammal species - rhinoceroses, pigs, rabbits, etc.
Upper Tertiary period or Neogene(24 – 2.6 million years ago). Mammals inhabit land, water, and air. The appearance of Australopithecines - the first ancestors of humans. During this period, the Alps, Himalayas, and Andes were formed.
Quaternary or Anthropocene(2.6 million years ago – today). A significant event of the period was the appearance of man, first the Neanderthals, and soon Homo sapiens. Vegetable and animal world acquired modern features.
Table 1
| Era | Period (million years) | Vegetation and fauna |
| Archean, Proterozoic (beginning 4500 million years ago) | ~3500 | Life originated in the seas. (No fossil traces of the first animal creatures remain.) |
| The existence of single-celled marine organisms. | ||
| Multicellular living creatures 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 modern mollusks and arthropods. |
| The first marine vertebrates are armored fish (already extinct) with a cartilaginous skeleton and shell. | ||
| Modern fish appear. Life begins to develop on the emerging land areas. The first newcomers to land are bacteria, fungi, mosses and small invertebrate animals, followed by amphibians (amphibians). | ||
| 400-300 | The land is covered with mighty forests of ferns and other plants that are now extinct. Insects are spreading. | |
| The birth of reptiles (reptiles). | ||
| Mesozoic (beginning 230 million years ago) | 230-70 | Age of reptiles. These animals spread 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 (plants whose flowers have ovaries) appear. | ||
| Forests of gymnosperms on most of the land are being replaced by forests of angiosperms. | ||
| Dinosaurs and other large reptiles are becoming extinct. | ||
| Cenozoic (beginning 70 million years ago) | 70-20 | Mammals spread throughout environment, displacing reptiles, whose numbers are sharply declining. Birds are spreading significantly. |
| 70-50 | Various classes of mammals emerge: carnivores, chiropterans, and the ancestors of modern monkeys and humans. Herbivores appear (eg 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 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 prenuclear organisms. They live in the seas, but also come onto land.
The water is saturated with oxygen, and soil-forming processes occur on land. The bacteria did not give rise to the formation of new groups and 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 the fusion of two identical cells in flagellates, considered the most ancient unicellular organisms.
Later, the sexual process took place with the help of special germ cells - male and female, which, when fused, form a zygote. From it develops an organism containing the genotype of the father and mother, which gives combinations of various characteristics in the offspring, expanding the possibilities of action natural selection. With the advent of photosynthesis, a single stem of life was divided into two - plants and animals - due to divergence. Multicellularity caused a further complication of the organization of living organisms: differentiation of tissues, organs, systems and their functions.
In the Proterozoic era (duration 2,000 million years), green algae developed, including multicellular ones. Remains of fauna 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 invertebrate animals are known, including echinoderms and arthropods. It is believed that at the end of the Proterozoic era, primary chordates appeared - a subtype of skullless, the only representative of which in the modern fauna is the lancelet. Bilaterally symmetrical animals appear, sensory organs and nerve nodes develop, animal behavior becomes more complex, mobility and energy in life processes in general increase.
In the Paleozoic era, lasting 330 million years (ancient life), divided into several periods, further evolutionary transformations of the organic world took place. 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.
Silurian (435-400 million years ago) is rich in remains of fossil trilobites and especially brachiopods (currently there are about 200 species left). Remains of jawless vertebrates - scutes (ancestors of lampreys) - have been discovered. Further development 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, some green multicellular algae adapted to life on land. Perhaps they were psilophytes. They already had the fabrics.
Mushrooms have appeared. From the mid-Devonian (400-435 million years ago), psilophytes gradually decreased, disappearing by the end of this period. And they are replaced by lycophytes, horsetails and ferns - spore plants. During the Devonian period, jawed armored fish (their descendants are modern cartilaginous fish, for example, sharks and rays) and lungfishes appeared. However, another group of fish - lobe-finned fish - made landfall. The most primitive terrestrial vertebrates are considered to be ancient amphibians, originating from one of the groups of lobe-finned animals.
Based hereditary variability through a process of natural selection, fins evolved into limbs for moving on land. Lungs developed for breathing on land. The most ancient amphibians - stegocephalians (shell-headed) lived in swampy 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 far from water bodies.
During 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 horsetails 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 deposits of coal.
During this period, seed ferns also grew, which developed seeds instead of spores. Seed ferns (the oldest gymnosperms) clearly indicate the origin of seed plants from spore plants. The appearance of seed plants was a major aromorphosis that determined the further evolution of plants. In seed plants, fertilization occurs without the participation of water, and the embryo is located in the seed, which has a supply of nutrients.
Since the end of the Carboniferous period, due to increased mountain building, the humid climate almost everywhere gave way to dry. Tree ferns began to die out, surviving only in some damp places small forms. Seed ferns also became extinct. They were replaced by more resilient gymnosperms, which, thanks to the spread of seeds, mastered arid habitats. The spread and magnificent development of gymnosperms continued almost until the end of the Mesozoic era. During the Carboniferous period, there was an intensive development of insects, spiders, and scorpions that breath air and lay eggs with a protective shell that protects them from drying out.
At the same time, trilobites began to disappear. There were many brachiopods, mollusks, fish (especially sharks), echinoderms, and corals developed. Previously existing types and classes diverged and 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, which were more protected and adapted to living in a drier climate on land.
The appearance of ancient reptiles is a new aromorphosis in the development of the animal world. These were mostly herbivores, but some switched to a predatory lifestyle. Animal-toothed reptiles appeared, from whose descendants the first mammals are believed to have originated.
Animal-toothed lizards - transitional form. Thus, in the Paleozoic era, namely in the Permian period (280-230 million years ago), plants and animals had already reached land: these are vascular (spore and gymnosperm) plants, lobe-finned fish, amphibians, reptiles, arthropods (spiders, supposed 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 large amount 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 continental climate conditions, the development of gymnosperms intensified, in which fertilization occurred 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 mid-Cretaceous period, when, due to increasing drought and increasing brightness of the Sun, a recently emerged group of plants, the angiosperms, came to the fore. Dicotyledonous and monocotyledonous plants appeared already at the end of the Mesozoic, and in the Cretaceous period they began to flourish.
Angiosperms are characterized by a large aromorphosis - the appearance of a flower adapted to pollination. Idioadaptive changes in the flower have contributed to numerous partial adaptations to pollination. Subsequently, idioadaptation of the flower occurred, 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 the leaves. The lush development of angiosperms was simultaneously associated with the development of higher forms of arthropod (insect) pollinators: butterflies, bumblebees, bees, flies, etc.
The Mesozoic era (“the era of 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, and flying lizards. The giant reptiles became extinct relatively quickly. The first small mammals appeared in the Triassic, their reproduction was carried out by viviparity, and they fed their young with milk. They had a constant temperature and differentiated teeth.
The ancestors of mammals were wild-toothed lizards. The first birds appeared in the Jurassic period of the Mesozoic era - they were toothy birds. And at the end of the Mesozoic the first real birds appeared. Ancient cartilaginous fish were replaced by true bony fish in the Triassic. As a result of divergence, species diversity within each systematic group continually increased.
Characteristics of the Mesozoic Era
table 2
| Era (duration, million years) | Period (duration, million years) | Beginning (millions of years ago) | Climate and environment (global geographic changes) | Development of the organic world | |
| Animal world | World of plants | ||||
| Mesozoic (middle life), | Triassic (Triassic), 40 ± 5 | 230 ± 10 | Weakening of climatic zonality, smoothing out temperature differences. The beginning of continental movement. | The beginning of the heyday of reptiles - the “age of dinosaurs” begins; turtles, crocodiles, etc. appear. The appearance of the first mammals, true bony fish. | Ferns, horsetails, and lycophytes are common. Seed ferns are dying out. |
| Jurassic (Yura), | 190 - 195 ± 5 | The climate, initially humid, changes towards the end of the period to become dry in the equator region. Movement of continents, formation of the Atlantic Ocean. | In the ocean, new groups of mollusks appear, 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 zonation appears. | |
| Cretaceous (Chalk), | 136 ± 5 | In many areas of the Earth the climate is cooling. A pronounced retreat of the seas, followed by a vast increase in the area of the World Ocean and a new rise of land. Intensive mountain-building processes (Alps, Andes, Himalayas). | The appearance of true birds, as well as marsupials and placental mammals. The reservoirs are dominated by bony fish. Insect bloom. Extinction of large reptiles and primitive Mesozoic mammals. | The number of ferns and gymnosperms is sharply declining. 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 Anthropocene, which continues to the present day. During this era, continents and seas were formed in their modern form. In the Paleogene, angiosperms spread across all continents and freshwater bodies. In the second half of this period, rapid mining processes began. The weather became colder and the evergreen forests were replaced by deciduous ones. There was a rapid adaptation of forms in various local conditions.
At the end of the Neogene - the beginning of the Anthropocene, glaciers advanced from the north; on the path of the sliding of the glaciers, all living things died, leaving only those forms that were able to survive and adapt to the changed environmental conditions. Arctic flora has developed. The final formation of the modern plant world takes place in the Anthropocene. In the Cenozoic, gastropods and bivalves spread, and insects flourished among arthropods.
Large aromorphoses of insects - the development of the tracheal respiratory system, chewing-type mouthparts, hard chitinous cover, articulated limbs and nervous system - ensured their prosperity. Birds and mammals have taken a dominant position in the animal world due to an increase in the intensity of the functions of the central nervous system (especially brain functions), the complication of the structure of the circulatory system (separation of arterial and venous blood), constant body temperature and an increase in the level of metabolic processes, etc. Rapid idioadaptation to changing environmental conditions ensured their prosperity.
Has a long history. It all started approximately 4 billion years ago. The Earth's atmosphere does not yet have an ozone layer, the concentration of oxygen in the air is very low and nothing can be heard on the surface of the planet except erupting volcanoes and the noise of the wind. Scientists believe that this is what our planet looked like when life began to appear on it. It is very difficult to confirm or refute this. Rocks that could provide more information to people were destroyed a long time ago, thanks to the geological processes of the planet. So, the main stages of the evolution of life on Earth.
Evolution of life on Earth. Unicellular organisms.
Life began with the appearance of the simplest forms of life - single-celled organisms. The first unicellular organisms were prokaryotes. These organisms were the first to appear after the Earth became suitable for life. would not allow even the simplest forms of life to appear on its surface and in the atmosphere. This organism did not require oxygen for its existence. The concentration of oxygen in the atmosphere increased, which led to the appearance eukaryotes. For these organisms, oxygen became the main thing for life; in an environment where the oxygen concentration was low, they did not survive.
The first organisms capable of photosynthesis appeared 1 billion years after the appearance of life. These photosynthetic organisms were anaerobic bacteria. Life gradually began to develop and after the content of nitrogenous organic compounds fell, new living organisms appeared that were able to use nitrogen from the Earth’s atmosphere. Such creatures were blue-green algae. The evolution of single-celled organisms occurred after terrible events in the life of the planet and all stages of evolution were protected under magnetic field land.
Over time, the simplest organisms began to develop and improve their genetic apparatus and develop methods of reproduction. Then, in the life of single-celled organisms, a transition occurred to the division of their generative cells into male and female.
Evolution of life on Earth. Multicellular organisms.
After the emergence of single-celled organisms, more complex forms of life appeared - multicellular organisms. The evolution of life on planet Earth has acquired more complex organisms that differ more complex structure and difficult transitional stages of life.
First stage of life - Colonial unicellular stage. The transition from unicellular organisms to multicellular ones, the structure of organisms and the genetic apparatus becomes more complex. This stage is considered the simplest in the life of multicellular organisms.
Second stage of life - Primary differentiated stage. A more complex stage is characterized by the beginning of the principle of “division of labor” between organisms of one colony. At this stage, specialization of body functions occurred at the tissue, organ and systemic organ levels. Thanks to this, a nervous system began to form in simple multicellular organisms. The system did not yet have a nerve center, but there was a coordination center.
Third stage of life - Centrally differentiated stage. During this stage, the morphophysiological structure of organisms becomes more complex. Improvement of this structure occurs through increased tissue specialization. The nutritional, excretory, generative and other systems of multicellular organisms become more complex. Nervous systems develop a well-defined nerve center. Reproduction methods are improving - from external to internal fertilization.
The conclusion of the third stage of life of multicellular organisms is the appearance of man.
Vegetable world.
The evolutionary tree of the simplest eukaryotes was divided into several branches. Multicellular plants and fungi appeared. Some of these plants could float freely on the surface of the water, while others were attached to the bottom.
Psilophytes- plants that first mastered land. Then other groups of terrestrial plants arose: ferns, mosses and others. These plants reproduced by spores, but preferred an aquatic habitat.
Plants reached great diversity during the Carboniferous period. Plants developed and could reach a height of up to 30 meters. During this period, the first gymnosperms appeared. The most widespread species were lycophytes and cordaites. Cordaites resembled coniferous plants in their trunk shape and had long leaves. After this period, the surface of the Earth was diversified with various plants that reached 30 meters in height. After a lot of time, our planet became similar to the one we know now. Now there is a huge variety of animals and plants on the planet, and man has appeared. Man, as a rational being, after he got “on his feet”, devoted his life to studying. Riddles began to interest people, as well as the most important thing - where did man come from and why does he exist. As you know, there are still no answers to these questions, there are only theories that contradict each other.
Creationism: life was created by the creator - God.
Biogenesis hypothesis: According to this theory, life can only arise from living things.
Panspermia hypothesis(G. Richter, G. Helmholtz, S. Arrhenius, P. Lazarev): according to this hypothesis, life could have arisen one or more times in space. Life on Earth appeared as a result of its introduction from space.
The Eternity of Life Hypothesis(V. Preyer, V.I. Vernadsky): life has always existed, there is no problem of the origin of life.
Abiogenesis theory: life arose from inanimate matter through the self-organization of simple organic compounds.
■ The Middle Ages were characterized by primitive ideas that allowed the emergence of entire living organisms from inanimate matter (it was believed that frogs and insects were born in damp soil, flies from rotten meat, fish from silt, etc.).
■ A modern concretization of this theory is the Oparin-Haldane coacervate hypothesis.
Oparin's coacervate hypothesis- Haldane: life arose abiogenically during three stages:
■ First step- emergence organic matter from inorganic under the influence physical factors environment that existed on ancient earth more than 3.5 billion years ago;
■ second phase- the formation of complex biopolymers (proteins, fats, carbohydrates, nucleic acids, proteinoids) from simple organic compounds in the waters of the Earth's primary ocean and the formation of coacervates from them - droplets of a concentrated mixture of various biopolymers. Coacervates did not have the genetic information to enable them to reproduce and copy, and were therefore not “alive”;
■ third stage- the emergence in coacervates of lipoprotein membrane structures and selective metabolism and the formation of probionts - the first primitive heterotrophic living organisms capable of self-reproduction; the beginning of biological evolution and natural selection.
The first carriers of genetic information were RNA molecules. They were formed with the help of proteinoids that attracted certain nucleotides, which were combined into RNA chains. Such RNA carried information about the structure of proteinoids and attracted the corresponding amino acids, which led to the reproduction of exact copies of proteinoids. Later, the functions of RNA were transferred to DNA (DNA is more stable than RNA and can be copied with greater accuracy), and RNA began to act as an intermediary between DNA and protein. In the process of evolution, those probionts in which the interaction of proteins and nucleic acids was most clear had an advantage.
Evolution of probionts
There were probionts anaerobic heterotrophic prokaryotes . They received food and energy for life from organic substances of abiogenic origin through anaerobic digestion (fermentation, or fermentation). The depletion of organic matter increased competition and accelerated the evolution of probionts.
As a result, differentiation of probionts occurred. One part of them (primitive ancestors modern bacteria), remaining anaerobic heterotrophs , has undergone progressive complication. Other probionts containing certain pigments have acquired the ability to form organic substances by photosynthesis (first oxygen-free, and then - the ancestors of cyanobacteria - with the release of oxygen). Those. arose anaerobic autotrophic prokaryotes , which gradually saturated the Earth's atmosphere with free oxygen.
With the advent of oxygen there arose aerobic heterotrophic prokaryotes , existing due to more efficient aerobic oxidation of organic substances formed as a result of photosynthesis.
The emergence and evolution of eukaryotes and multicellular organisms
Amoeba-like heterotrophic cells could engulf other small cells. Some of the “eaten” cells did not die and were able to function inside the host cell. In some cases, such a complex turned out to be biologically mutually beneficial and led to a stable symbiosis of cells.
❖ Symbiotic theory appearance (about 1.5 billion years ago) and evolution of eukaryotic cells (symbiogenesis):
■ one group of anaerobic heterotrophic probionts entered into symbiosis with aerobic heterotrophic primary bacteria, giving rise to eukaryotic cells that have mitochondria as energy organelles;
■ another group of anaerobic heterotrophic probionts united not only with aerobic heterotrophic bacteria, but also with primary photosynthetic cyanobacteria, giving rise to eukaryotic cells that have chloroplasts and mitochondria as energy organelles. Symbiont cells with mitochondria later gave rise to the animal and fungal kingdoms; with chloroplasts - the plant kingdom.
The increasing complexity of eukaryotes led to the emergence of cells with polar properties, capable of mutual attraction and fusion, i.e. to the sexual process, diploidy (the consequence of this is meiosis), dominance and recessivity, combinative variability, etc.
❖ Hypotheses for the emergence of multicellular organisms(2.6 billion years ago):
■ gastrea hypothesis (E. Haeckel, 1874): the ancestral forms of multicellular organisms were unicellular organisms that formed a single-layer spherical colony. Later, due to invagination ( intussusception) part of the wall of the colony, a hypothetical two-layer organism was formed - gastraea, similar to the gastrula stage of embryonic development of animals; at the same time, the cells of the outer layer performed integumentary and motor functions, the cells of the inner layer performed the functions of nutrition and reproduction;
■phagocytella hypothesis(I.I. Mechnikov, 1886; this hypothesis underlies modern ideas about the origin of multicellular™): multicellular organisms evolved from single-celled colonial flagellated organisms. The feeding method of such colonies was phagocytosis. The cells that captured the prey moved inside the colony, and tissue was formed from them - endoderm, which performs a digestive function. The cells remaining outside performed the functions of perception of external irritations, protection and movement; of these, the integumentary tissue subsequently developed - ectoderm. Some cells specialized in performing the function of reproduction. Gradually, the colony turned into a primitive but integral multicellular organism - a phagocytella. This hypothesis is confirmed by the currently existing organism, intermediate between single and multicellular, Trichoplax, the structure of which corresponds to the structure of the phagocytella.
Main stages of plant evolution
Historical stages
The division of eukaryotes into several branches from which plants, fungi and animals originated (about 1-1.5 billion years ago). The first plants were algae, most of which floated freely in the water, the rest were attached to the bottom.
The appearance of the first land plants—rhiniophytes (about 500 million years ago, as a result of the process of mountain building and reduction in the area of seas, some of the algae ended up in small bodies of water and on land; some of them died, others adapted, acquiring new characteristics: they formed tissues that then differentiated into integumentary, mechanical and conductive bacteria, interacting with minerals. earth's surface, formed a soil substrate on land). Spore reproduction of rhinophytes.
The extinction of rhiniophytes and the appearance of clubmosses, horsetails and ferns (about 380-350 million years ago); the emergence of vegetative organs (which increased the efficiency of functioning of individual plant parts); appearance of seed ferns and conifers.
The appearance of gymnosperms (about 275 million years ago), which could live in a drier environment; extinction of seed ferns and tree-like spore plants; in higher land plants there is a gradual reduction of the haploid generation (gametophyte) and a predominance of the diploid generation (sporophyte).
The emergence of diatoms (about 195 million years ago).
The emergence of angiosperms (about 135 million years ago); bloom of diatoms.
Extinction of many plant species (about 2.5 million years ago), decline of woody forms, flourishing of herbaceous ones; acquisition flora modern forms.
Biological stages
1. Transition from haploid to diploid
. Diploidy mitigates the impact of unfavorable recessive mutations on viability and makes it possible to accumulate a reserve of hereditary variability. This transition can also be traced when comparing modern plant groups. Thus, in many algae all cells, except zygotes, are haploid. In mosses, the haploid generation (adult plant) predominates, with a relatively weak development of the diploid generation (sporulation organs). In more highly organized brown algae, along with haploid ones, there are also diploid individuals. But already in ferns the diploid generation predominates, and in gymnosperms (pines, spruce, etc.) and angiosperms (many trees, shrubs, grasses) only diploid individuals exist independently (see figure). 
2. Loss of connection between the process of sexual reproduction and water
, transition from external to internal fertilization.
3. Division of the body into organs
(root, stem, leaf), development of the conducting system, complication of tissue structure.
4. Pollination specialization
with the help of insects and the distribution of seeds and fruits by animals.
Main stages of animal evolution
❖ The most important biological stages of evolution:
■ the emergence of multicellular and increasing division and differentiation of all organ systems;
■ the appearance of a hard skeleton (external in arthropods, internal in vertebrates);
■ development of the central nervous system;
■ development social behavior in different groups of highly organized animals, which, together with the accumulation of a number of large aromorphoses, led to the emergence of man and human society.
The most important aromorphoses and their results
Geochronological scale of the Earth
❖Catarchaean era(4.7-3.5 billion years ago): the climate is very hot, strong volcanic activity; is happening chemical evolution, biopolymers arise.
❖ Archean era(3.5-2.6 billion years ago) - the era of the origin of life. The climate is hot, active volcanic activity; the emergence of life on Earth, the appearance of the first organisms (anaerobic heterotrophs) - probionts - at the border of the aquatic and terrestrial-air environments. The appearance of anaerobic autotrophic organisms, archaebacteria, cyanobacteria; the formation of deposits of graphite, sulfur, manganese, layered limestone as a result of the vital activity of archaebacteria and cyanobacteria. At the end of the Archean, colonial algae appeared. The appearance of oxygen in the atmosphere.
❖ Proterozoic era(2.6-0.6 billion years ago) - era of early life; is divided into the Early Proterozoic (2.6-1.65 billion years ago) and the Late Proterozoic (1.65-0.6 billion years ago). It is characterized by intense mountain building, repeated cold snaps and glaciations, the active formation of sedimentary rocks, the formation of oxygen in the atmosphere (at the end of the era - up to 1%), the beginning of the formation of a protective ozone layer in the Earth's atmosphere. In the organic world: development of unicellular prokaryotic and eukaryotic photosynthetic organisms, the emergence of the sexual process, the transition from fermentation to respiration (early Proterozoic); the appearance of lower aquatic plants - stromatolites, green algae, etc. (Late Proterozoic), and by the end of the era - all types of multicellular invertebrates (except chordates): sponges, coelenterates, worms, mollusks, echinoderms, etc.
❖ Paleozoic era(570-230 million years ago) - era ancient life; is divided into 6 periods: Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian.
■ Cambrian(570-490 million years ago): the climate is temperate, the continent of Pangea began to submerge into the waters of the Tethys Ocean. In the organic world: life is concentrated in the seas; evolution of multicellular forms; flourishing of the main groups of algae (green, red, brown, etc.) and marine invertebrates with chitin-phosphate shells (especially trilobites and archaeoceates).
■ Ordovician(490-435 million years ago): the climate is warm, the subsidence of Pangea reaches its maximum. At the end of the period, significant areas are freed from water. In the organic world: abundance and diversity of algae; the appearance of corals, marine echinoderms, hemichordates (graptolites), the first chordates (jawless fish) and the first land plants - rhiniophytes. Dominance of trilobites.
■ Silur(435-100 million years ago): the climate is arid and cool; land uplift and intensive mountain building occur; O 2 concentration in the atmosphere reaches 2%; The formation of the protective ozone layer is completed. In the organic world: the colonization of land by vascular plants (rhiniophytes) and the formation of soil on it; the emergence of modern groups of algae and fungi; the flourishing of trilobites, graptolites, corals, and crustaceans in the seas; the appearance of jawed chordates (armored and cartilaginous fish) and the first terrestrial arthropods (scorpions).
■ Devonian(400-345 million years ago): climate is sharply continental; glaciation, further rise of land, complete liberation from the sea of Siberia and Eastern Europe; the concentration of O 2 in the atmosphere reaches the modern one (21%). In the organic world: the flourishing of rhinophytes, and then (by the end of the period) their extinction; the appearance of the main groups of spore-bearing plants (bryophytes, ferns, lycophytes, horsetails), as well as primitive gymnosperms (seed ferns); the flourishing of ancient invertebrates, and then the extinction of many of their species, as well as most jawless ones; the appearance of wingless insects and arachnids; flourishing of armored, lobe-finned and lungfishes in the seas; emergence of the first four-legged vertebrates (stegocephals) - the ancestors of amphibians - onto land.
■ Carboniferous (Carboniferous period) (345-280 million years ago): climate is hot and humid (in the Northern Hemisphere), cold and dry (in the Southern Hemisphere); low-lying continents with extensive swamps in which coal was formed from fern-like trunks. In the organic world: flowering of tree-like spore-like horsetails (calamites), lycophytes (lepidodendrons and sigillaria) plants and seed ferns; appearance of the first gymnosperms (conifers); flourishing of testate amoebae (foraminifera), marine invertebrates, cartilaginous fish (sharks); the appearance on land of the first amphibians, ancient reptiles (cotylosaurs) and winged insects; extinction of graptolites and armored fishes.
■ Permian(280-240 million years ago): aridity increases, cooling sets in, and intense mountain building occurs. In the organic world: disappearance of tree fern forests; distribution of gymnosperms (Ginkgoaceae, conifers); the beginning of the flowering of stegocephals and reptiles; distribution of cephalopods (ammonites) and bony fishes; decrease in the number of species of cartilaginous, lobe-finned and lungfishes; extinction of trilobites.
❖ Mesozoic era(240-67 million years ago) - the middle era in the development of life on Earth; is divided into 3 periods: Triassic, Jurassic, Cretaceous.
■Triassic(240-195 million years ago): climate arid (deserts appear); the drift and separation of continents begins (the continent of Pangea is divided into Laurasia and Gondwana). In the organic world: extinction of seed ferns; dominance of gymnosperms (cycads, ginkgos, conifers); development of reptiles; the appearance of cephalopods (belemnites), the first oviparous mammals (triconodonts) and the first dinosaurs; the extinction of stegocephalians and many species of animals that flourished in the Paleozoic era.
■ Yura(195-135 million years ago): climate arid, continents raised above sea level; on the land big variety landscapes. In the organic world: the appearance of diatoms; dominance of ferns and gymnosperms; the flourishing of cephalopods and bivalves, reptiles and giant lizards (ichthyosaurs, brontosaurs, diplodocus, etc.); appearance of the first toothy birds (Archaeopteryx); development of ancient mammals.
■ Chalk(135-67 million years ago): climate wet (lots of swamps); colder weather in many areas; continental drift continues; intensive chalk deposition occurs (from Foraminifera shells). In the organic world: the dominance of gymnosperms, followed by their sharp decline; the appearance of the first angiosperms, their predominance in the second half of the period; formation of maple, oak, eucalyptus and palm forests; the flourishing of flying lizards (pterodactyls, etc.); the beginning of the flowering of mammals (marsupials and placentals); towards the end of the period, the extinction of giant lizards; bird development; emergence of higher mammals.
❖Cenozoic era(began 67 million years ago and continues to the present) is divided into 2 periods: tertiary (Paleogene and Neogene) and Quaternary (Anthropocene).
■ Tertiary period(from 67 to 2.5 million years ago): climate warm, cool towards the end; completion of continental drift; continents take on modern shapes; characterized by intense mountain building (Himalayas, Alps, Andes, Rocky Mountains). In the organic world: dominance of monocotyledonous angiosperms and conifers; development of the steppes; flourishing of insects, bivalves and gastropods; extinction of many forms of cephalopods; bringing the species composition of invertebrates closer to the modern one; wide distribution of bony fish occupying freshwater bodies of water and seas; divergence and flowering of birds; the development and flourishing of marsupials and placental mammals, similar to modern ones (cetaceans, ungulates, proboscis, carnivores, primates, etc.), in the Paleogene - the beginning of the development of anthropoids, in the Neogene - the appearance of human ancestors (driopithecus).
■ Quaternary period (anthropogen; began 2.5 million years ago): a sharp cooling of the climate, giant continental glaciations (four ice ages); formation of landscapes of modern type. In the organic world: the disappearance of many ancient plant species as a result of glaciations, the dominance of dicotyledonous angiosperms; decline of woody and flourishing of herbaceous plant forms; the development of many groups of marine and freshwater mollusks, corals, echinoderms, etc.; extinction of large mammals (mastodon, mammoth, etc.); appearance, prehistoric and historical development human: intensive development of the cerebral cortex, upright posture.
