The main stages in the development of life on earth are chemical. The main stages of the development of life on Earth. The problem of self-reproduction and the hypothesis of the rna world

Archaea- the oldest life. It lasted for about 900 million years, from 3500 to 2600 million years. The remains of organic life are few. Archean rocks contain a lot of graphite͵ it is believed that graphite was formed from the remains of living organisms. Discovered stromatolites- cone-shaped limestone formations of biogenic origin. Many reserves of sulfur, iron, copper, nickel, and cobalt are of bacterial origin. The living organisms of the Archean were first represented by anaerobic prokaryotes, later blue-green ones appear. Photosynthesis of blue-green animals 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. Duration 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, the fundamental aromorphoses occurred:

© about 1500 million years ago the first eukaryotes appear, the dominance of prokaryotes is replaced by the flourishing of eukaryotic organisms;

© multicellular organisms appeared - the prerequisites were created for the specialization of cells, an increase in the size and complexity of organisms;

© sexual reproduction (combinative variability) arose, in which the fusion of the genetic material of different individuals provided material for natural selection;

© The most important aromorphosis was the formation of bilateral symmetry in actively moving organisms.

In this era, all departments of algae are formed, the thallus for many becomes lamellar. For animals of that time, the absence of skeletal formations is characteristic, the end of the Proterozoic is sometimes called "century of jellyfish"... Annel worms 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 subdivided into six periods: Cambrian, Ordovician, silurian, Devonian, carbon, Permian.

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

In the Devonian, ferns appear - herbaceous and arboreal horsetails, moss, ferns. The emergence of roots and leaves provided sufficient air and mineral nutrition for a variety of ferns. Fern-like unicellular spores reproduce, in humid places they develop outgrowths that form sex cells. For fertilization, water is needed, 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. Coal 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 with

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

Seed ferns gave rise to the development of voice-seed plants. In the Permian period, the climate became arid and colder. The rainforests remain at the equator, the rest of the territory is spread by voice-seeds.

The 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 chordates appear with an internal skeleton, the distant descendants of which are lancelet and cyclostomes - lampreys and myxines.

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

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

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

In the Carboniferous, winged insects appear on land, some dragonflies had wingspan up to 70 cm.The abundance of arthropods on land caused the appearance of a large number different forms 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 period, climate change was accompanied by the disappearance of stegocephals and the dispersal of reptiles.

Mesozoic era.

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

Rice. 364. Archeopteryx.

In the animal kingdom of the Mesozoic era, insects and reptiles are most widespread. In the Triassic, reptiles return to the water for the second time, plesiosaurs live in shallow water, ichthyosaurs, resembling modern dolphins, hunt far from the coast. The first oviparous mammals appear, unlike reptiles, their high metabolic rate allows them to maintain a constant body temperature.

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

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

Cenozoic era.

Cenozoic- an era of new life. It lasts 67 million years and is divided into two periods unequal in time - the Tertiary (Paleogene and Neogene) and Quaternary (Anthropogen). In the first half of the Tertiary period (in the Paleogene), a warm tropical climate re-established over most of the Earth, in the second half (Neogene), tropical forests are replaced by steppes, monocotyledonous plants are spreading. In the Quaternary period, which lasts about 1.5 million years, during the Ice Age, Eurasia and North America were subjected to glaciations four times.

As a result of the steppe formation that took place in the second half of the Tertiary period, some of the primates were forced to descend to the ground and adapt to life in open spaces. These were the ancestral forms of people - hominids, erect primates. Another part remained to live in tropical forests and became the ancestors of great apes - pongid... At the end of the Tertiary period, monkeys appear from the hominids, pithecanthropus.

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 ice thickness of which reached tens of meters, the water evaporated and 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 to migrate animals from continent to continent. About 40 thousand years ago, the ancient people left Asia for North America along the Beringian Bridge. As a result of the cold snap and the appearance of a man who hunted animals, many large animals disappear: saber-toothed tigers, mammoths, woolly rhinos. The remains of dozens of mammoths and other large animals are found near the sites of ancient people. In connection with the extermination of large animals 10-12 thousand years ago, man was forced from gathering and hunting to go to agriculture and cattle breeding.

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

The history of the development of Life on Earth

Paleontology - a science that studies the history of living organisms on Earth, based on the surviving remains, prints and other traces of their vital activity.

DEVELOPMENT OF LIFE ON EARTH

CRYPTOSIS (hidden life)

About 85% of the entire lifetime of life on Earth

ARCHEY

(oldest)

about

3500 million

(lasting 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 emergence of eukaryotic cells

Aromorphoses: the appearance of a shaped nucleus, photosynthesis

PROTEROSIS

(primary life)

about 2600 million (lasting about 2000 million)

the longest in the history of the Earth

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%. Dry land - a single supercontinent

( Pange I am ) The process of soil formation.

The emergence of multicellularity, the process of respiration. All types of invertebrates emerged. Protozoa, coelenterates, sponges, worms are widespread. Of plants, unicellular algae are predominantly widespread.

Aromorphoses in animals: the appearance of multicellularity, 2-sided symmetry of the body, muscles, body segmentation.

PHANEROSIS

(explicit life)

PALEOZOIC

(ancient life)

Duration approx. 340 million

Cambrian

OK. 570 million

dl. 80 million

At first, a temperate humid, then a warm dry climate. The land has split into continents

The flowering of marine invertebrates, most of which are trilobites (ancient arthropods), about 60% of all species of marine fauna. The emergence of organisms with a mineralized skeleton. The emergence of multicellular algae

Ordovician

OK. 490 million

dl. 55 million

Moderate humid climate with a gradual rise in environments. Temperatures. Intensive mountain building, liberation of large areas from water

The appearance of the first vertebrates (chordates) - jawless. A variety of cephalopods and gastropods, a variety of algae: green, brown, red. The appearance of coral polyps

Silurian

OK. 435 million

dl. 35 million

Intense mountain building, coral reef formation

Lush development of corals and trilobites, crustaceans appear, widespread armored jawless (the first true vertebrates), the emergence of echinoderms, the first terrestrial animals -arachnids ... Out on land of plants, the first land plants( psilophytes )

Devonian

OK. 400 million

dl. 55million

Climate: alternating dry and rainy seasons. Glaciation in what is now South America and South Africa

Age of fish: The emergence of fish of all taxonomic groups (today you can find: coelacanth (cross-finned fish), protopter (lungfish)) the extinction of a significant number of invertebrates and most jawless, the appearance of ammonite-cephalopods with spirally twisted shells. spiders, ticks. The emergence of terrestrial vertebrates -stegocephaly (shell-headed ) (first amphibians; descended from cross-finned fish) Development and extinction of psilophytes. The emergence of spore plants: lycopods, horsetails, ferns. The emergence of mushrooms

Carbon

(Carboniferous period)

OK. 345

mln.

dl. 65 million

Worldwide spread of swamps. Warm humid climate gives way to cold and dry one.

The flourishing of amphibians, the appearance of the first reptilescotylosaurus , flying insects, trilobite decline. On land - forests of spore plants, the appearance of the first conifers

Permian

280 million

L. 50 million

Climate zoning. Completion of mountain building, retreat of seas, formation of semi-enclosed bodies of water. Reef formation

Fast development reptiles, the emergence of animal-like reptiles. Extinction of trilobites. The disappearance of forests, due to the extinction of tree ferns, horsetails and lyres. Permian extinction (96% of all marine species, 70% of terrestrial vertebrates)

An important evolutionary event takes place in the Paleozoic: the colonization of land by plants and animals.

Aromorphoses in plants: the appearance of tissues and organs (psilophytes); root system and leaves (ferns, horsetails, lyes); seed (seed ferns)

Aromorphoses in animals: the formation of bony jaws (maxillary carapace fish); five-toed limb and pulmonary respiration (amphibians); internal fertilization and accumulation of nutrients (yolk) in the ovum (reptiles)

MESOSOE

(average life) era of reptiles

Triassic

230 million

For 40 million

Supercontent split

(Laurasia, Gondwana) continental movement

The heyday of reptiles "age of dinosaurs", there are turtles, crocodiles, tuatara. The emergence of the first primitive mammals (ancestors - ancient animal-toothed reptiles), true teleost fishes. Seed ferns are dying out, ferns, horsetails, lycopods are widespread, gymnosperms are widespread

Yura

190 million

D. 60 million

The climate is humid, then gives way to arid in the equator, the movement of continents

The dominance of reptiles on land, in the ocean and in the air (flying reptiles - pterodactyls) the appearance of the first birds - Archeopteryx. Ferns and gymnosperms are widespread

chalk

136 million

L. 70 million

Cooling climate, retreat of the seas, is replaced by an increasesocean

The appearance of real 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, a more developed nervous system, an increase in the supply of nutrients in the yolk (birds)

Carrying babies in the mother's body, feeding the embryo through the placenta (mammals)

Plant aromorphoses: flower emergence, seed protection by membranes (angiosperms)

Cainoso

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. The flowering of insects. The dominance of angiosperms, tundra and taiga appear, numerous idioadaptations appear in animals and plants (for example: self-pollinating, cross-pollinated plants, a variety of fruits and seeds)

Neogene

25 million

dl. 23 mln.

Continental movement

Dominance of mammals, widespread: primates, ancestors of horses, giraffes, elephants; saber-toothed tigers, mammoths

Anthropogen

1.5 million

Repeated climate changes are characteristic. Major glaciations in the Northern Hemisphere

The emergence and development of man, animal and vegetable world acquire modern features

The main stages of the evolution of flora and fauna

Geochronological history of the Earth. It is customary to divide the history of the Earth into periods of time, the boundaries of which are major geological events: mountain-building processes, the rise and fall of the land, the change in the outlines of the continents, the level of the oceans. Movements and faults crust that occurred in different geological periods, were accompanied by intensified volcanic activity, as a result of which a huge amount of gases and ash were emitted into the atmosphere, which reduced the transparency of the atmosphere and contributed to a decrease in the amount of solar radiation entering the Earth. This was one of the reasons for the development of glaciers, which caused climate change, which had a strong impact on the development organic world... In the process of evolution, new forms of organisms constantly arose, and the former forms, which turned out to be unadapted to the new conditions of existence, died out.

For many millions of years, the remains of organisms that once lived have accumulated on the planet. On the basis of the finds of fossil forms in the sediments of the earth layers, it is possible to trace the true history of living nature (Table 4.2). The use of the radioisotope method makes it possible to determine with great accuracy the age of rocks in the places of occurrence of paleontological remains and the age of fossil organisms.

Based on paleontological data, the entire history of life on Earth is divided into eras and periods.

The main stages of plant evolution. In the Proterozoic era (about 1 billion years ago), the trunk of the most ancient eukaryotes split into several branches, from which plants, fungi and animals arose. Most of the plants of this period floated freely in the water, some of them attached to the bottom.

Tab. 4.2. Geochronological scale of the Earth.

	Period	Beginning (million years ago)	Evolutionary events
Cenozoic (new life)	Quaternary		Plants: The extinction of many plant species, the decline of arboreal forms, the flowering of herbaceous; the flora is acquiring a modern look. Animals: The development of many groups of marine and freshwater molluscs, corals, echinoderms, etc. Formation of existing communities, the emergence and evolution of humans.
	Neogene (neogene)		Plants: The predominance of angiosperms and conifers, retreating forests, an increase in the area of ​​steppes. Animals: The species composition of invertebrates is close to modern. The flourishing of placental mammals, similar to modern ones. The emergence of great apes.
	Paleogene (Paleogene)		Plants: Flowering of diatoms and main groups of angiosperms. Dominance of bivalves and gastropods. Animals: Extinction of the oldest mammals. The development of marsupials and primitive placentals: insectivores, ancient ungulates, ancient predators. The beginning of the development of anthropoids.
Mesozoic (middle life)	Cretaceous (chalk)		Plants: At the beginning of the period, the dominance of gymnosperms and the appearance of angiosperms, which predominate in the second half of the period. Animals: Development of bivalves and gastropods and other invertebrates. Development of large reptiles in the first half of the period and their extinction in the second half of the period. Development of mammals and birds.
	Jurassic (Jurassic)		Plants: Emergence of diatoms. Dominance of ferns and gymnosperms. The flowering of cephalopods and bivalves. The flowering of reptiles: ground, waterfowl, flying. The appearance of ancient birds, the development of ancient mammals.
	Triassic (Triassic)		Plants: Extinction of seed ferns. Development of gymnosperms. Animals: The extinction of many animals that thrived during the Paleozoic era. Extinction of stegocephals, the development of reptiles, the emergence of ancient mammals.
Paleozoic (ancient life)	Permian		Plants: Distribution of the first groups of gymnosperms. Animals: Reducing the number of speciescartilaginous, cross-finned and lung-breathing fish. Development of stegocephals, reptiles, some of which were ancestral to mammals and birds.
	Coal (carbon)		Plants: Flowering lycopods, horsetails, ferns, seed ferns; the appearance of conifers. Animals: The flowering of ancient marine invertebrates. The emergence of primary wingless and ancient winged insects. Distribution of sharks, stegocephals. The emergence and flowering of amphibians. The emergence of ancient reptiles.
	Devonian (Devonian)		Plants: The flowering of rhinophytes, by the beginning of the Late Devonian, their extinction. The emergence of modern types of vascular plants. Animals: The flowering of ancient invertebrates, the emergence of arachnids. The flowering of armored, cross-finned and lung-breathing fishes. At the end of the period, the appearance of the first tetrapods - stegocephals (ancient amphibians).
	Silurian (Silurian)		Plants: Emergence of modern groups of algae and fungi. At the end of the period, the reliable appearance of the first land plants. The emergence of terrestrial arthropods - scorpions. The emergence of ancient carapace and cartilaginous fish.
	Ordovician (Ordovician)		Plants: Abundance of seaweed. Presumable appearance of the first land plants - rhinophytes. The appearance of the first vertebrates - jawless.
	Cambrian (Cambrian)		Plants: Life is concentrated in the seas. Algae evolution. Animals: Development of multicellular forms. The flowering of marine invertebrates with a chitin-phosphate shell.
Proterozoic (early life)	Late Proterozoic		Plants: Development of algae, Animals: Various multicellular primitive organisms that do not have skeletal structures.
	Early Proterozoic		Plants and Animals: Development of unicellular prokaryotic and eukaryotic photosynthetic organisms. The onset of the sexual process.
	No under sect.		: The emergence of life on Earth, the appearance of the first cells - the beginning of biological evolution. The emergence of anaerobic autotrophic organisms, bacteria, cyanobacteria.
Katarchei	No under sect.		Chemical evolution leading to the emergence of biopolymers.

1. Archean era- the oldest stage in the history of the Earth, when life arose in the waters of the primary seas, which was originally presented precellular its forms and the first cellular organisms. Wasp analysis This age shows that bacteria and blue-greens lived in the aquatic environment.

2 ... Proterozoic era. On the verge of the Archean and Proterozoic eras, the structure and function of organisms became more complex: multicellularity, a sexual process that increased the genetic heterogeneity of organisms and provided extensive material for selection, became more diverse, photosynthetic plants became more diverse. The multicellularity of organisms was accompanied by an increase in the specialization of cells, their association into tissues and functional systems.

It is rather difficult to trace in detail the evolution of animals and plants in the Proterozoic era due to the recrystallization of sedimentary rocks and the destruction of organic remains. In the sediments of this era, only imprints of bacteria, algae, lower types of invertebrates and lower chordates. A major step in evolution was the emergence of organisms with bilateral symmetry of the body, differentiated into the anterior and posterior regions, left and right sides, and the isolation of the dorsal and abdominal surfaces. The dorsal surface in animals served as protection, and on the abdominal surface were located the mouth and organs for capturing food.

3. Paleozoic era. The flora and fauna reached a great variety, and terrestrial life began to develop.

In the Paleozoic, six periods are distinguished: Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian. In the Cambrian period, life was concentrated in water (it covered a significant part of our planet) and is represented by more perfect multicellular algae, which had a dissected thallus, thanks to which they synthesized organic substances more actively and were the original branch for terrestrial leafy plants. Invertebrates are widespread in the seas, including brachiopods, and from arthropods - trilobites. Archaeocyates, which formed reefs in ancient seas, were an independent type of two-layer animals of that period. They died out, leaving no descendants. Inhabited on land only bacteria and mushrooms.

In the Ordovician period, the climate was warm even in the Arctic. In the fresh and brackish waters of this period of lush development, planktonic seaweed, varied coral from the type of coelenterates, there were representatives of almost all types invertebrates including trilobites, molluscs, echinoderms. Bacteria were widely represented. The first representatives of jawless vertebrates appear - corymbose.

At the end of the Silurian period, due to mountain-building processes and a reduction in the area of ​​the seas, some of the algae found themselves in new environmental conditions - in shallow water bodies and on land. Many of them died. However, as a result of multidirectional variability and selection individual representatives acquired signs that contributed to survival in new conditions. The first terrestrial spore plants appeared - psilophytes. They had a cylindrical stem about 25 cm in height, instead of leaves - scales. Their most important adaptations are the appearance of integumentary and mechanical tissues, root-like outgrowths - rhizoids, as well as an elementary conducting system.

In the Devonian, the number of psilophytes sharply decreased, they were replaced by their transformed descendants, higher plants - lycopods, bryophytes and fern-like, which develop true vegetative organs (root, stem, leaf). The emergence of vegetative organs increased the efficiency of the function of individual parts of plants and their vitality as a harmoniously integral system. The emergence of plants on land preceded the emergence of animals. Plants accumulated biomass on Earth, and oxygen in the atmosphere. The first inhabitants of land from invertebrates were spiders, scorpions, millipedes. There were many fish in the Devonian seas, among them - jaw armored, having an internal cartilaginous skeleton and an external strong shell, movable jaws, paired fins. Freshwater bodies inhabited cross-finned fish that had gill and primitive pulmonary respiration. With the help of fleshy fins, they moved along the bottom of the reservoir, and when they dried out, they crawled into other reservoirs. A group of cross-finned fish were the ancestors of ancient amphibians - stegocephalic. Stegocephals lived in swampy areas, came out onto land, but multiplied only in water.

In the Carboniferous period, giant ferns spread, which, in a warm, humid climate, settled everywhere. During this period, they flourished ancient amphibians.

During the Permian period, the climate became drier and colder, which led to the extinction of many amphibians. By the end of the period, the number of amphibian species began to decline sharply, and only small amphibians (newts, frogs, toads) have survived to this day. The tree-like spore ferns have been replaced by seed ferns, which gave rise to gymnosperms. The latter had a developed tap root system and seeds, and fertilization took place in the absence of water. The extinct amphibians were replaced by a more progressive group of animals descended from stegocephals - reptiles. They had dry skin, denser cellular lungs, internal fertilization, a supply of nutrients in the egg, protective egg membranes.

4. Mesozoic era includes three periods: Triassic, Jurassic, Cretaceous.

In the Triassic widespread gymnosperms, especially conifers, which have taken a dominant position. At the same time they spread widely reptiles: ichthyosaurs lived in the seas, plesiosaurs in the air - flying lizards, reptiles were represented in various ways on earth. Giant reptiles (brontosaurs, diplodocus, etc.) soon became extinct. At the very beginning of the Triassic, a group of small animals with a more perfect structure of the skeleton and teeth separated from the reptiles. These animals acquired the ability to live birth, a constant body temperature, they had a four-chambered heart and a number of other progressive features of the organization. These were the first primitive mammals.
In the sediments of the Jurassic period of the Mesozoic o6, the remains of the first bird were also found - archeopteryx. He combined in his structure the features of birds and reptiles.

In the Cretaceous period of the Mesozoic, a branch of plants that had an organ of seed reproduction - a flower - separated from the gymnosperms. After fertilization, the ovary of the flower turns into a fruit, therefore the developing seeds inside the fruit are protected by the pulp and shells from adverse environmental conditions. The variety of flowers of various adaptations for pollination and distribution of fruits and seeds allowed angiosperm (flowering) plants to spread widely in nature and take a dominant position. In parallel with them, a group of arthropods developed - insects which, being pollinators of flowering plants, contributed greatly to their progressive evolution. In the same period, appeared real birds and placental mammals. Signs of a high degree of organization in them - constant body temperature | complete separation of arterial and venous blood flow, increased metabolism, perfect thermoregulation, and in mammals, in addition, viviparity, feeding of young with milk, development of the cerebral cortex - allowed these groups to take a dominant position on Earth.

5. Cenozoic era subdivided into three periods: Paleogene, Neogene and Quaternary.

In the Paleogene, Neogene and the beginning of the Quaternary period, flowering plants, thanks to the acquisition of numerous private adaptations, occupied most of the land and represented the subtropical and tropical flora. Due to the cooling caused by the advance of the glacier, the subtropical flora retreated to the south. Terrestrial vegetation of temperate latitudes began to be dominated by deciduous trees, adapted to the seasonal rhythm of temperatures, and shrubs and herbaceous plants. The flowering of herbaceous plants occurs in the Quaternary period. Warm-blooded animals are widespread:
birds and mammals. In the ice age, cave bears, lions, mammoths, woolly rhinos lived, which gradually died out after the retreat of glaciers and the warming of the climate, and the animal world acquired a modern look.

The main event of this era is the formation of man. By the end of the Neogene, small tailed mammals lived in the forests - lemurs and tarsiers. From them came the ancient forms of monkeys - parapithecus, leading an arboreal lifestyle and feeding on plants and insects. Their distant descendants - living today gibbons, orangutans and extinct small tree monkeys - dryopithecus. Driopithecus gave rise to three lines of development that led to chimpanzee, gorilla, as well as extinct australopithecus. From the Australopithecines at the end of the Neogene originated a reasonable person.

The main features of the evolution of the animal world are as follows:

1. progressive development of multicellularity and, as a result, specialization of tissues and all organ systems;
2. a free lifestyle, which determined the development of various mechanisms of behavior, as well as the relative independence of ontogenesis from fluctuations in environmental factors;
3. the emergence of a hard skeleton: external in some invertebrates (arthropods) and internal in chordates;
4. progressive development of the nervous system, which became the basis for the emergence of conditioned reflex activity

Taken from sites.

There are several hypotheses about the origin of life on Earth. They can be divided into

two groups.

Biogenesis- the origin of the living from the living (hypothesis of panspermia, stationary state).

Abiogenesis- the origin of the living from the nonliving (hypothesis of spontaneous generation, biochemical evolution)

steady state hypothesis

The earth and life on it never arose, but exist forever.

Species of living organisms can die out or change their numbers, but they cannot change.

Proof: from the theory of biogenesis as a statement that living organisms can only come from other living organisms, the only logical conclusion inevitably follows: life has existed forever. In other words, if we trace the chain of living organisms generating each other into the past, then it should stretch indefinitely.

creationism

The variety of forms in the organic world is the result of their creation by God.

Denies species change and evolution.

Almost all religious teachings claim that man and all other living beings are created by God. The views were immediately perfect and will always remain as they were created. There is no evidence that this is the case. It's a matter of faith.

Most scientists were creationists until the 19th century.

The founder of taxonomy K. Linnaeus believed that all types of plants and animals have existed since the "creation of the world" and were created by God independently of each other.

The French anatomist and paleontologist J. Cuvier believed that during the history of the Earth there were extensive catastrophes, or cataclysms, after which devastated places were populated by organisms that survived a catastrophe in remote areas (catastrophe theory).

Proof of creationism: expediency of the device of living organisms and their communities, good adaptation to habitat conditions.

Some modern followers of creationism use the existence of very complex, diverse molecular genetic processes in living things as an argument in favor of the non-randomness of their appearance. Others agree with the existence of an evolutionary process, but believe that the very beginning of evolution was associated with the act of creation.

Panspermia hypothesis

Life is brought in from space

It does not offer a solution to the problem of the origin of life in the Universe, but only explains its appearance on our planet by its introduction from space.

Proof of panspermia: some microorganisms, and especially their spores, can remain viable under very harsh conditions (for example, very low temperatures).

However, until now, when studying meteorites, no life forms have been found on them.

Oparin – Haldane hypothesis of biochemical evolution (hypothesis of abiogenesis)

The emergence of life on our planet occurred in several stages of evolution:

Abiogenic synthesis of simple organic compounds.

Formation of biopolymers.

Linking biopolymers - education coacervates.

The emergence of membranes separating the first similarities of living organisms - protobionts - from the environment.

The emergence of metabolism and energy with the environment.

The emergence of the ability to reproduce itself.

Formation of ecological links and formation of the first ecosystems.

The hypothesis of abiogenesis is based on data modern science about the formation of the Earth about 4.5 billion years ago.
The Oparin-Haldane hypothesis was formed and received the first experimental confirmation in the 1950s - 1960s At present, on the basis of modern data, the hypothesis of abiogenesis has undergone significant changes, has been expanded and supplemented. In particular, most scientists today believe that the emergence of self-reproduction preceded the formation of membranes and a full-fledged metabolism or occurred in parallel with them. Self-reproduction presupposes the preservation of properties in a number of generations of organisms, lies at the basis of natural selection (which, of course, already operated among these ancient systems) and evolution in general.

After the appearance of our planet as a solid body and its gradual cooling, condensation of water vapor took place in the primary atmosphere of the Earth. Rainwater with substances dissolved in it accumulated in the relief depressions.

The primary atmosphere contained significant amounts of carbon dioxide, hydrogen sulfide, methane, ammonia, water vapor, and almost completely no oxygen (hence, there was no ozone layer). The earth was exposed to the sun's harsh ultraviolet radiation.

The environment as a whole was full of energy. For education or break chemical bonds the following sources were important:

hard ultraviolet radiation;

electrical discharges;

natural radioactivity;

sunny wind;

volcanic activity.

American researchers Stanley Miller and Harold Urey in 1953 experimentally showed how biologically important chemical compounds... They picked up different gases in a ratio close to the composition of the ancient atmosphere, and passed spark discharges through this mixture. As a result, such biologically important compounds as formic and lactic acids, urea and amino acids (glycine, alanine, glutamic acid, aspartic acid) were obtained. Subsequent experimenters, varying the conditions and improving the methods of analysis, expanded the range of products in such a synthesis. They obtained many amino acids, purine bases - adenine and guanine (they are obtained if hydrocyanic acid is added to a mixture of gases), four- and five-carbon sugars. In 2008, the experiment was repeated and it was found that 22 different amino acids are formed.
Miller and Urey based their experiments on ideas from the 1950s. about the possible composition of the earth's atmosphere. Currently, views on this issue have changed. In particular, it is believed that the CO concentration could not be so high, while it was shown that even small changes in the conditions and composition of the gas mixture lead to very significant changes in the efficiency of the organic synthesis process. The application of new analytical methods to the most ancient terrestrial rocks made it possible to clarify the composition of the ancient atmosphere of the Earth. It turned out to be very similar to the modern atmospheres of Venus and Mars - 98% CO2, 1.5% N2 and small fractions of other gases, mainly argon and SO2. No organic matter is obtained from such an atmosphere in Miller's apparatus. To obtain organic matter from CO2, a reductant is needed, and scientists are looking for it.

Waters on the surface and directly below the surface of the Earth were saturated with similar substances ( "Primary broth"). Composition and concentration organic matter depended on environmental conditions and were probably different in different parts of the Earth's surface. Part of the formed organic matter was destroyed. However, the other part could concentrate, for example, in porous minerals, forming polymers. Experiments have shown that heating a mixture of amino acids leads to the formation of rather long polypeptides with a random sequence of monomers. Some of these polypeptides have catalytic activity.

Fatty acids, combining with alcohols, could form lipid films on the surface of water bodies.

The bonds between different biopolymers and other substances could be formed during the isolation of small volumes of biopolymers, for example, during the formation of bubbles from lipid films ( coacervates) or from peptides (microspheres).

The role of coacervates was studied by Alexander Ivanovich Oparin and his English colleague John Haldane. The studies of the American scientist Sydney Fox were devoted to microspheres.

problems of the theory of abiogenesis

The problem of the complexity of a self-replicating system... The complexity of living cells is enormous. Even the simplest bacteria have a genome of over a million nucleotides, coding for over a thousand proteins. This genome requires special molecular machines for protein synthesis (ribosomes), DNA synthesis (replicative fork), energy supply (at least 12 glycolysis enzymes, and usually also an electron transport chain on the membrane) and means of regulation and control (transcription factors and signal proteins). The complexity of such a system is very high, and biology does not know any simpler self-reproducing systems than the cell. Viruses do not count - they require a complex living cell to reproduce. Darwinian natural selection can create ever more complex systems, but to do so, they must be capable of replication from the outset. If natural selection begins only with the appearance of the first cell, then it takes a huge amount of time to randomly form it - many orders of magnitude longer than the age of the Universe.

The problem of chiral purity.
All living systems contain only certain optical isomers of amino acids and sugars (L-amino acids and D-sugars). Opposite isomers are found, but rarely and in special cases (for example, in the cell wall of bacteria). Inanimate systems do not possess this property. This property of living systems is called chiral purity... It is maintained due to the spatial correspondence of the molecules of biological catalysts - enzymes - to only one of the optical isomers. Majority chemical reactions in inanimate systems are not stereoselective, that is, both optical isomers participate in them with the same probability. Very few abiogenic processes are known that are stereoselective, that is, predominantly one optical isomer is involved in them, but they do not provide sufficient enrichment of the system with the required isomers. However, in recent years, many processes have been discovered that lead to enrichment in one or another optical isomer - see further in Section 3.

The problem of lack of reductant in the primary atmosphere(see above about the Miller-Urey experiment). According to new data on the composition of the primary atmosphere, it practically did not contain molecular hydrogen and CO, and the syntheses described by Miller and Urey could not proceed.
In many modern successful experiments on abiogenic synthesis of organics, formaldehyde is taken as a starting substance. It is highly reactive and provides many biologically relevant products.
Where could formaldehyde come from? It could be formed during the reduction of carbon dioxide on inorganic catalysts. For example, hot volcanic lava containing native iron forms formaldehyde on contact with a humid CO2 atmosphere. An aqueous solution of iron (II) hydroxide produces the same reaction under ultraviolet light.
Today, there are two detailed theories of abiogenic synthesis of organic matter, linking the reduction of CO2, energy metabolism, and the peculiarities of the content of metal ions in living matter.
The first, suggesting the origin of life in the "iron-sulfur world", on underwater geothermal springs, was proposed by the German biophysicist Karl Washterhauser.
Another scenario of abiogenic synthesis of organic matter at geothermal sources was proposed by Mulkidzhanyan. It follows from the ability of zinc and manganese sulfides to reduce various substances in the light ("zinc world").
How did the further synthesis of complex biogenic organics proceed? Scientists conduct many experiments, trying to find the conditions for these processes, possible on the ancient Earth. An important role in modern research is played by Butlerov reaction, opened back in 1865. In this reaction water solution formaldehyde (CH2O) with the addition of Ca (OH) 2 or Mg (OH) 2 turns into a complex mixture of sugars with slight heating. This reaction turned out to be autocatalytic, that is, the products are catalysts. Also catalyzes the reaction with light. Under certain conditions, the Butlerov reaction solves the problem of chiral purity, leading to the appearance of only certain optical isomers of sugars. To do this, add silicates or hydroxyapatite (calcium phosphate) - compounds that are not lacking in the earth's crust. Also, the addition of a complex of the amino acid L-proline with a zinc ion leads to the synthesis of chirally pure D-sugars.
For a long time, the synthesis of nucleotides was considered a big problem, since the conditions for the synthesis of its individual components, as well as 4 different nucleotides, turned out to be poorly compatible. However, in 2008, Sunderland carried out the synthesis of nucleotides as a whole, and not in the form of separate components, and all 4 variants were obtained.

the problem of self-reproduction and the RNA-WORLD HYPOTHESIS

How did probionts acquire the ability to reproduce themselves, i.e. the ability to reproduce the structure of macromolecules? It is impossible to say for sure, but there are hypotheses explaining the formation of self-reproducing systems based on nucleic acids.

Modern scientists are still actively involved in the problem of abiogenic synthesis and have achieved significant success. In particular, the autocatalytic synthesis of sugars (the Butlerov reaction) is being actively studied, the process of synthesizing a whole nucleotide has been discovered (earlier the formation of nucleotides was an impregnable strength - all its components could not be obtained under similar conditions). Having received nucleotides, it is easy to proceed to the assembly of the first nucleic acids, and these molecules already contain the potential for self-reproduction. Probably the first self-replicating systems were built on the basis of RNA.

The discovery in 1982 of the catalytic activity of some RNA molecules (ribozymes) suggests that it was RNA molecules that were the first biopolymers in which the ability to replicate was combined with enzymatic activity. Self-replicating RNAs (albeit of short length), that is, RNAs capable of catalyzing the synthesis of their copies, were artificially obtained. Moreover, it is RNA that plays an important role in all fundamental and, as it is assumed, the most ancient processes in the cell. Thus, it is ribosomal RNA that plays a catalytic role in protein biosynthesis on ribosomes. The protein-free ribosome does not currently exist - proteins are an integral part of this complex, but it may well have existed in the past.
All these facts speak in favor of the fact that it was RNA that once performed all biologically significant functions in the first living systems, and only then part of the functions passed to DNA (storage of hereditary information) and proteins (catalysis, structural functions, etc.). This assumption is called RNA world hypothesis and enjoys widespread support among modern scientists.

The structure of self-replicating RNA

ecology of the first organisms

It can be assumed that on initial stages In the development of life on Earth, a very wide variety of protobionts appeared, but all of them were anaerobic heterotrophs, that is, they possessed an anoxic type of respiration and absorbed ready-made organic matter (primary organic matter). Already at this stage, predation and other forms of relationships between species could appear, i.e. primary communities. At the beginning of biological evolution, the source of nutrition was probably the reserves of organic matter created by the abiogenic way. When these reserves were depleted, then the advantages in reproduction should have been obtained by those organisms that had the possibility of autotrophic nutrition, and the predators eating them.

However, it should be noted that the most ancient indisputable remains of living things belong to photosynthetic, that is, autotrophic organisms (chlorophyll components, stromatolites - fossilized cyanobacterial mats, etc.). The most ancient community that left traces in the fossil record is precisely the cyanobacterial mat. Modern mats include photosynthetic microbes, chemosynthetics and heterotrophs, and there is evidence of these components in ancient mats as well.

Cut stromatolite Modern stromatolites, Australia

The spread of probionts, and just biologically important polymers and oligomers, was limited by hard ultraviolet radiation in the absence of an ozone shield.
The emergence of oxygenic photosynthesis, i.e. photosynthesis with the release of oxygen, cannot be accurately dated, but there is paleontological evidence of the presence of cyanobacteria 3.4 billion years ago. At first, oxygen did not accumulate in the atmosphere, but was spent on the oxidation of various components of the earth's crust, for example, ferrous iron. Then a slow increase in oxygen concentration began, which led to the so-called oxygen revolution- a change in the character of the entire atmosphere from reducing to oxidizing. The sharp acceleration of oxygen accumulation in the atmosphere dates back to about 2.3 billion years ago. Molecular oxygen is a poison for anaerobic organisms, and many inhabitants ancient earth were just like that. Many scientists believe that atmospheric oxygenation was the first global environmental disaster and led to the extinction of many organisms. The survivors adapted by developing systems of protection against the toxic effects of oxygen, and some learned to use it for the oxidation of organic substances - cellular respiration, which made it possible to obtain additional energy in comparison with anoxic metabolism. Therefore, aerobes (oxygen breathing creatures) have gained a competitive advantage over anaerobes. It is from such organisms that the majority of modern species originated, including eukaryotes, which include plants, animals, fungi and a conditional (combined) group of protozoa.

It is believed that the emergence of modern types of multicellular organisms was impossible before reaching a certain concentration of oxygen in the environment.
The accumulation of oxygen in the atmosphere led to the formation of an ozone shield, which allowed life to reach land.

Spontaneous life hypothesis

The emergence of life in an abiogenic way in the distant past

The hypothesis existed in parallel with creationism. Its supporters believed that the conditions necessary for the emergence of life still exist.

Proof: the appearance of fly larvae in rotting meat; mice from crackers and rags (Van Helmont's experiments).

Experiments in which spontaneous generation did not occur after boiling the medium and sealing the vessel were not convincing, since it was believed that boiling kills the "life force".

After a while, fly larvae appeared in the open vessel, since the flies entered the vessel and laid eggs. In a closed vessel, "spontaneous generation" did not occur.

Later, at the beginning of the 18th century, Lazdzaro Spallanzani decided to check the results of the English researcher John Needham on the spontaneous generation of microorganisms in lamb gravy. He took vials of seed broth, some of which he closed with a cork. others he sealed on the fire of the burner. He boiled some for a whole hour, while others he heated only for a few minutes. After several days, Spallanzani discovered that in those bottles that were tightly sealed and well heated, there were no "small animals" - they appeared only in those bottles that were not tightly closed and not boiled for a long time, and most likely, they penetrated there from air or survived after boiling, and did not arise by themselves. Thus, Spallanzani not only proved the inconsistency of the concept of spontaneous generation, but also revealed the existence of the smallest organisms that can tolerate a short - for several minutes - boiling. Meanwhile, Needham teamed up with Count Buffon, and together they put forward a hypothesis about a producing force, a life-giving element that is contained in lamb broth and seed broth and is capable of creating living organisms from inanimate matter. Spallanzani kills the Generating Power when he boils his bottles for hours on end, they argued, and it is only natural that little animals cannot arise where this power does not exist. In subsequent experiments Spallanzani succeeded in proving the inconsistency of these hypotheses.

The experiments of the famous French biologist and chemist turned out to be decisive. Louis Pasteur... He attached an S-shaped tube with a free end to the flask. Spores of microorganisms settled on a curved tube and could not penetrate into the nutrient medium. A well-boiled nutrient medium remained sterile, and no emergence of life was found in it, despite the fact that air was provided. As a result of a series of experiments, Pasteur proved the validity of the theory of biogenesis and finally refuted the theory of spontaneous generation.
It was Pasteur who owes medicine to the birth of antiseptics and asepsis, which opened the way for modern surgery.

Flask with an S-shaped neck.

Has a long history. It all started about 4 billion years ago. The Earth's atmosphere does not yet have an ozone layer, the oxygen concentration in the air is very low and nothing is heard on the planet's surface, except for erupting volcanoes and wind noise. Scientists believe that this is what our planet looked like when life began to appear on it. It is very difficult to confirm or deny this. Rocks, which could give more information to people, collapsed a long time ago, thanks to geological processes planets. So, the main stages of the evolution of life on Earth.

Evolution of life on Earth. Single-celled organisms.

Life got its start with the emergence of the simplest forms of life - unicellular organisms. The first one cellular organisms were prokaryotes. These organisms were the first to appear after the Earth became suitable for the beginning of life. would not allow even the simplest forms of life to appear on its surface and in the atmosphere. This organism did not need 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 dropped, new living organisms appeared that could use nitrogen from the Earth's atmosphere. Such creatures were blue-green algae. The evolution of unicellular organisms took place 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 ways of their reproduction. Then, in the life of unicellular organisms, there was a transition to the division of their generative cells into male and female.

Evolution of life on Earth. Multicellular organisms.

After the emergence of unicellular organisms, more complex forms of life appeared - multicellular organisms... The evolution of life on planet Earth has acquired more complex organisms, distinguished by a more complex structure and complex transitional stages of life.

The first stage of life - Colonial unicellular stage... The transition from unicellular organisms to multicellular organisms, the structure of organisms and the genetic apparatus becomes more complicated. This stage is considered the easiest 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 took place 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 is a coordination center.

The third stage of life - Centralized differentiated stage. During this stage, the morphophysiological structure of organisms becomes more complex. The improvement of this structure occurs through the strengthening of tissue specialization. The food, excretory, generative and other systems of multicellular organisms are complicated. Have nervous systems a well-defined nerve center appears. The methods of reproduction are improving - from external fertilization to internal fertilization.

The conclusion of the third stage of the life of multicellular organisms is the appearance of man.

Vegetable world.

The evolutionary tree of the simplest eukaryotes has split into several branches. Multicellular plants and fungi appeared. Some of these plants could float freely on the surface of the water, while others attached to the bottom.

Psilophytes- plants that first mastered the land. Then other groups of terrestrial plants arose: ferns, lyres, and others. These plants multiplied by spores, but preferred an aquatic habitat.

Plants reached a great variety in the Carboniferous period. Plants developed and could reach a height of up to 30 meters. In this period, the first gymnosperms appeared. The most widespread were Lycopods and Cordaites. Kordaites resembled conifers in the shape of the trunk and had long leaves. After this period, the surface of the Earth was varied with various plants, which reached 30 meters in height. After a lot of time, our planet has become similar to the one we know now. Now on the planet there is a huge variety of animals and plants, a man has appeared. Man, as a rational being, after he got up "on his feet" devoted his life to studying. Riddles began to interest a person, as well as the most important thing - where did a person come from and why he exists. As you know, there are still no answers to these questions, there are only theories that contradict each other.