Ch.Darwin's lesson about the reasons for the evolution of the animal world. Disclosure by Ch. Darwin of the reasons for the evolution of the animal world Breeding of domestic animals. artificial selection

Ichthyostega's skull was similar to that of a lobe-finned fish Eusthenopteron, but a pronounced neck separated the body from the head. While the Ichthyostega had four strong limbs, the shape of its hind legs suggests that this animal did not spend all of its time on land.

The first reptiles and the amniotic egg

Hatching a turtle from an egg

One of the greatest evolutionary innovations of the Carboniferous (360 - 268 million years ago) was the amniotic egg, which allowed early reptiles to move away from coastal habitats and colonize dry areas. The amniotic egg allowed the ancestors of birds, mammals and reptiles to breed on land, and prevent the embryo inside from drying out, so you could do without water. It also meant that, unlike amphibians, reptiles were able to produce fewer eggs at any given time, as the risks of hatchlings were reduced.

The earliest date for the development of an amniotic egg is about 320 million years ago. However, reptiles were not exposed to any significant adaptive radiation for about 20 million years. The current thinking is that these early amniotes still spent time in the water and came ashore mainly to lay their eggs rather than feed. Only after the evolution of herbivores did new groups of reptiles emerge that could exploit the abundant floristic diversity of the Carboniferous.

Hylonomus

The early reptiles belonged to an order called the captorhinids. Gilonomus were representatives of this detachment. They were small, lizard-sized animals with amphibian skulls, shoulders, pelvis, and limbs, as well as intermediate teeth and vertebrae. The rest of the skeleton was reptilian. Many of these new "reptilian" features are also seen in small, modern amphibians.

First mammals

Dimetrodon

A major transition in the evolution of life occurred when mammals evolved from a single lineage of reptiles. This transition began during the Permian period (286 - 248 million years ago), when a group of reptiles that included the Dimetrodons gave birth to the "terrible" therapsids. (Other large branches, sauropsids, gave rise to birds and modern reptiles.) These reptilian mammals in turn gave birth to cynodonts such as Thrinaxodon ( Thrinaxodon) during the Triassic period.

Trinaxodon

This evolutionary line provides an excellent series of transitional fossils. The development of a key mammalian feature, the presence of a single bone in the lower jaw (compared to several in reptiles), can be traced in the fossil history of this group. It includes excellent transitional fossils, Diarthrognathus and Morganucodon, whose lower jaws have both reptilian and mammalian articulations with the upper ones. Other new features found in this lineage include the development of different types of teeth (a feature known as heterodontia), the formation of a secondary palate, and an increase in dentary bone in the lower jaw. The legs are located directly below the body, an evolutionary advance that occurred in the ancestors of the dinosaurs.

The end of the Permian period was marked by perhaps the greatest. According to some estimates, up to 90% of the species became extinct. (Recent studies have suggested that this event was caused by an asteroid impact that triggered climate change.) During the subsequent Triassic period (248 to 213 million years ago), the survivors of the mass extinction began to occupy vacant ecological niches.

However, at the end of the Permian, it was dinosaurs, not reptile mammals, that took advantage of the new available ecological niches to diversify into dominant land vertebrates. In the sea, ray-finned fish began a process of adaptive radiation that made their class the most species-rich of all classes of vertebrates.

Dinosaur classification

One of the major changes in the group of reptiles that gave birth to the dinosaurs was in the posture of the animals. The arrangement of the limbs has changed: previously they protruded on the sides, and then began to grow directly under the body. This had major implications for locomotion, as it allowed for more energy-efficient movements.

Triceratops

Dinosaurs, or "terrible lizards", are divided into two groups based on the structure of the hip joint: lizards and ornithischians. Ornithischians include Triceratops, Iguanodon, Hadrosaurus, and Stegosaurus). The lizards are further subdivided into theropods (eg Coelophys and Tyrannosaurus Rex) and sauropods (eg Apatosaurus). Most scientists agree that from theropod dinosaurs.

Although dinosaurs and their immediate ancestors dominated the terrestrial world during the Triassic, mammals continued to evolve during this time.

Further development of early mammals

Mammals are highly developed synapsids. Synapsids are one of the two great branches of the amniote family tree. Amniotes are a group of animals that are characterized by having embryonic membranes, including reptiles, birds, and mammals. Another large amniotic group, the Diapsid, includes birds and all living and extinct reptiles except turtles. Turtles belong to the third group of amniotes - Anapsids. Members of these groups are classified according to the number of openings in the temporal region of the skull.

Dimetrodon

Synapsids are characterized by the presence of a pair of accessory openings in the skull behind the eyes. This discovery gave synapsids (and similarly diapsids, which have two pairs of holes) stronger jaw muscles and better biting abilities than early animals. Pelycosaurs (such as Dimetrodon and Edaphosaurus) were early synapsids; they were reptilian mammals. Later synapsids included therapsids and cynodonts, which lived during the Triassic period.

cynodont

Cynodonts shared many characteristic mammalian features, including a reduced number or complete absence of lumbar ribs, suggesting a diaphragm; well developed fangs and secondary palate; increased size of the dentition; openings for nerves and blood vessels in the lower jaw, indicating the presence of whiskers.

About 125 million years ago, mammals had already become a diverse group of organisms. Some of these would have been similar to today's monotremes (such as the platypus and echidna), but early marsupials (a group that includes modern kangaroos and opossums) were also present. Until recently, placental mammals (the group to which most living mammals belong) were thought to be of a later evolutionary origin. However, recent discovered fossils and DNA evidence suggest that placental mammals are much older, and may have evolved over 105 million years ago.

Note that marsupials and placental mammals provide excellent examples of convergent evolution, where organisms that are not particularly closely related developed similar body shapes in response to similar environmental exposures.

Plesiosaurs

However, despite the fact that mammals had what many consider "advanced", they were still minor players on the world stage. When the world entered the Jurassic period (213 - 145 million years ago), the dominant animals on land, in the sea and in the air were reptiles. Dinosaurs, more numerous and unusual than during the Triassic, were the main land animals; crocodiles, ichthyosaurs, and plesiosaurs ruled the sea, and pterosaurs populated the air.

Archeopteryx and the evolution of birds

Archeopteryx

In 1861, an intriguing fossil was discovered in the Solnhofen Jurassic limestone in southern Germany, a source of rare but exceptionally well-preserved fossils. The fossil seemed to combine features of both birds and reptiles: a reptilian skeleton accompanied by a clear imprint of feathers.

While Archeopteryx was originally described as a feathered reptile, it has long been considered a transitional form between birds and reptiles, making it one of the most important fossils ever discovered. Until recently, it was the earliest known bird. Recently, scientists have realized that Archeopteryx bears more resemblance to the maniraptors, a group of dinosaurs that includes the infamous Jurassic Park velociraptors, than to modern birds. Thus, Archeopteryx provides a strong phylogenetic relationship between the two groups. Fossil birds have been found in China that are even older than Archeopteryx, and other feathered dinosaur discoveries support the theory that theropods evolved feathers for insulation and thermoregulation before birds used them for flight.

Looking closer at the early history of birds is a good example of the concept that evolution is neither linear nor progressive. The bird lineage is erratic and many "experimental" forms appear. Not everyone achieved the ability to fly, and some looked nothing like modern birds. For example, Microraptor gui, which appears to have been a flying animal with asymmetrical flight feathers on all four limbs, was a dromaeosaurid. Archeopteryx itself did not belong to the lineage from which true birds evolved ( Neornithes), but was a member of the now-extinct enanciornis birds ( Enantiornithes).

End of the Dinosaur Age

Dinosaurs spread throughout the world during the Jurassic, but during the subsequent Cretaceous (145 - 65 million years ago) their species diversity declined. In fact, many of the typically Mesozoic organisms such as ammonites, belemnites, ichthyosaurs, plesiosaurs, and pterosaurs were in decline during this time, despite still giving rise to new species.

The emergence of flowering plants during the early Cretaceous caused a major adaptive radiation among insects: new groups such as butterflies, moths, ants and bees emerged. These insects drank the nectar from the flowers and acted as pollinators.

The mass extinction at the end of the Cretaceous, 65 million years ago, wiped out the dinosaurs, along with any other land animal weighing more than 25 kg. This paved the way for the expansion of mammals on land. In the sea at this time, fish again became the dominant vertebrate taxon.

modern mammals

At the beginning of the Paleocene (65 - 55.5 million years ago), the world was left without large land animals. This unique situation was the starting point for a great evolutionary diversification of mammals, which were previously nocturnal animals the size of small rodents. By the end of the era, these representatives of the fauna occupied many of the free ecological niches.

The oldest confirmed primate fossils are about 60 million years old. Early primates evolved from ancient nocturnal insectivores, something like shrews, and resembled lemurs or tarsiers. They were probably arboreal animals and lived in or subtropical forests. Many of their characteristic features were well suited to this habitat: gripping hands, rotating shoulder joints, and stereoscopic vision. They also had a relatively large brain size and claws on their fingers.

The earliest known fossils of most modern orders of mammals appear in a short period during the early Eocene (55.5-37.7 million years ago). Both groups of modern ungulates - artiodactyls (a detachment to which cows and pigs belong) and equids (including horses, rhinos and tapirs) became widespread throughout North America and Europe.

Ambulocetus

At the same time that mammals were diversifying on land, they were also returning to the sea. The evolutionary transitions that led to whales have been extensively studied in recent years with extensive fossil finds from India, Pakistan and the Middle East. These fossils point to a change from terrestrial Mesonychia, which are the likely ancestors of whales, to animals such as Ambulocetus and primitive whales called Archaeocetes.

The trend towards a cooler global climate that occurred during the Oligocene epoch (33.7-22.8 million years ago) contributed to the emergence of grasses, which were to spread to vast grasslands during the subsequent Miocene (23.8-5.3 million years ago). ). This change in vegetation led to the evolution of animals, such as more modern horses, with teeth that could handle the high silica content of grasses. The cooling trend has also affected the oceans, reducing the abundance of marine plankton and invertebrates.

Although DNA evidence suggests that hominids evolved during the Oligocene, abundant fossils did not appear until the Miocene. Hominids, on the evolutionary line leading to humans, first appear in the fossil record during the Pliocene (5.3 - 2.6 million years ago).

During the entire Pleistocene (2.6 million - 11.7 thousand years ago) there were about twenty cycles of cold ice age and warm interglacial periods at intervals of about 100,000 years. During the Ice Age, glaciers dominated the landscape, snow and ice spread into the lowlands, and transported vast amounts of rock. Because a lot of water was locked up on the ice, the sea level dropped to 135 m than it is now. Wide land bridges allowed plants and animals to move. During warm periods, large areas were again submerged under water. These repeated episodes of environmental fragmentation resulted in rapid adaptive radiation in many species.

The Holocene is the current epoch of geological time. Another term that is sometimes used is the Anthropocene because its main characteristic is the global changes caused by human activities. However, this term can be misleading; modern humans were already created long before the beginning of the era. The Holocene epoch began 11.7 thousand years ago and continues to the present day.

Mammoths

When warming came on Earth, she gave way. As the climate changed, very large mammals that adapted to extreme cold, such as the woolly rhinoceros, became extinct. Humans, once dependent on these "mega-mammals" as their main source of food, have switched to smaller animals and started harvesting plants to supplement their diet.

Evidence shows that around 10,800 years ago, the climate underwent a sharp cold turn that lasted several years. The glaciers did not return, but there were few animals and plants. As temperatures began to recover, animal populations grew and new species emerged that still exist today.

Currently, the evolution of animals continues, as new factors arise that force representatives of the animal world to adapt to changes in their environment.

The history of animals has been studied most fully due to the fact that they have a skeleton and therefore are better fixed in fossilized remains. The earliest traces of animals are found at the end of the Precambrian (700 million years). It is assumed that the first animals originated either from a common trunk of all eukaryotes, or from one of the groups of ancient algae. The closest to the ancestors of protozoa (Protozoa) are unicellular green algae. It is no coincidence that, for example, euglena and volvox, capable of both photosynthesis and heterotrophic nutrition, are classified by botanists as green algae, and zoologists as protozoa. Over the entire history of the animal world, 35 types have arisen, of which 9 have died out, and 26 still exist.

The diversity and quantity of paleontological records in animal history increases dramatically in rocks dating back less than 570 million years. Within about 50 million years, almost all types of celiac animals with a strong skeleton appear rather quickly. Trilobites were widely distributed in the seas of the Silurian. The emergence of the chordate type (Chordata) dates back to less than 500 million years. Complexes of well-preserved fossils have been found in the shales of Berges (Columbia), which contain remains of invertebrates, in particular soft-bodied organisms of the Annelida type, to which modern earthworms belong.

The beginning of the Paleozoic is marked by the formation of many types of animals, of which about a third exist at the present time. The reasons for this active evolution remain unclear. In the late Cambrian time, the first fish appeared, represented by jawless-Agnata. In the future, they almost all died out, lampreys survived from modern descendants. In the Devonian, jawed fish arise as a result of such major evolutionary transformations as the transformation of the anterior pair of gill arches into jaws and the formation of paired fins. The first jawed-stomes were represented by two groups: ray-finned and lobe-finned. Almost all living fish are descendants of ray-finned fish. Lobe-finned animals are now represented only by lungfish and a small number of relict marine forms. Lobe-finned fins had bone supporting elements in their fins, from which the limbs of the first inhabitants of the land developed. Earlier, amphibians arose from the group of lobe-finned ones, therefore, all four-legged vertebrates have this extinct group of fish as their distant ancestor.

The most ancient representatives of amphibians - Ichthyostegs were found in the Upper Devonian deposits (Greenland). These animals had five-fingered limbs with which they could crawl on land. Nevertheless, a number of signs (a real caudal fin, a body covered with small scales) indicate that ichthyostegi lived mainly in water bodies. Competition with lobe-finned fish forced these first amphibians to occupy habitats intermediate between water and land.

The heyday of ancient amphibians is dated to the Carboniferous, where they were represented by a wide variety of forms, united under the name "stegocephals". Among them, the most prominent are labyrinthodonts and crocodilians. Two orders of modern amphibians - tailed and legless (or caecilians) - probably descended from other branches of stegocephalians.

From primitive amphibians, reptiles originate, widely settled on land by the end of the Permian period due to the acquisition of pulmonary respiration and egg shells that protect against drying out. Among the first reptiles, cotylosaurs stand out especially - small insectivorous animals and active predators - therapsids, which gave way in the Triassic to giant reptiles, dinosaurs that appeared 150 million years ago. It is likely that the latter were warm-blooded animals. In connection with warm-bloodedness, dinosaurs led an active lifestyle, which can explain their long dominance and coexistence with mammals. The reasons for the extinction of dinosaurs (about 65 million years ago) are unknown. It is assumed, in particular, that this could be the result of the mass destruction of dinosaur eggs by primitive mammals. A more plausible hypothesis seems to be that the extinction of dinosaurs is associated with sharp fluctuations in climate and a decrease in plant foods in the Cretaceous period.

Already in the period of the dominance of dinosaurs, there was an ancestral group of mammals - small in size with a coat of animals that arose from one of the lines of predatory therapsids. Mammals come to the forefront of evolution due to such progressive adaptations as the placenta, feeding offspring with milk, a more developed brain and the associated greater activity, warm-bloodedness. Mammals reached a significant diversity in the Cenozoic, primates appeared. The Tertiary period was the heyday of mammals, but many of them soon became extinct (for example, the Irish deer, saber-toothed tiger, cave bear).

The progressive evolution of primates was a unique phenomenon in the history of life, as a result, it led to the emergence of man.

The most significant features of the evolution of the animal world were as follows: 1) The progressive development of multicellularity and the specialization of tissues and all organ systems associated with it. A free way of life (the ability to move) largely determined the improvement of behavioral forms, as well as the autonomization of ontogenesis - the relative independence of individual development from fluctuations in environmental factors based on the development of internal regulatory systems. 2) The emergence of a solid skeleton: external - in arthropods, internal - in vertebrates. This division determined the different paths of evolution of these types of animals. The external skeleton of arthropods prevented an increase in body size, which is why all insects are represented by small forms. The internal skeleton of vertebrates did not limit the increase in body size, which reached its maximum size in Mesozoic reptiles - dinosaurs, ichthyosaurs. 3) Emergence and improvement of the centrally differentiated stage of organocavities to mammals. At this stage, the separation of insects and vertebrates occurred. The development of the central nervous system in insects is characterized by the improvement of forms of behavior according to the type of hereditary fixation of instincts. Vertebrates have developed a brain and a system of conditioned reflexes, and there is a pronounced tendency towards an increase in the average survival rate of individual individuals.

This path of evolution of vertebrates led to the development of forms of group adaptive behavior, the final event of which was the emergence of a biosocial creature - man.

Summary of a lesson in biology for grade 7.

Topic: "Charles Darwin on the causes of the evolution of the animal world."

Target: reveal the concepts of heredity, variability, the struggle for existence, natural selection as the driving forces of evolution.

Tasks:

educational: generalize knowledge about the evidence of evolution, consider the main provisions of the evolutionary teachings of Ch. Darwin;

developing: to continue the formation of the skills of research work in a group, independent work with a textbook, the ability to highlight the main thing, draw conclusions;

educational: patriotic education - on the example of the life of Ch. Darwin.

Lesson type : combined.

Conduct method : student messages, independent work in groups, defense of research papers, conversation.

Equipment : multimedia projector, multimedia presentations on the topic, the collection "Fossils", didactic material for consolidation on the topic "Evidence of evolution", forms of reflection and self-assessment.

Preparing the audience for work : On the desktops lay out equipment for organizing research work in a group, forms of reflection and self-assessment.

Board decoration : Evolution - evolutio - deployment - an irreversible process of the historical development of the living.

During the classes:

1. Organizational moment.

greetings;

the presence of students;

assessment of mood at the beginning of the lesson

2. Updating knowledge

Acquaintance of students with the topic of the lesson, the purpose and objectives of the lesson.

Research paper on the topic "Evidence for the evolution of animals" (5 min.)

Purpose: to summarize knowledge about the evidence for evolution.

Progress:

1. Determine the type of evidence for evolution.

2. Explain what this find testifies to.

Task for groups:

the imprint of a trilobite shell, and a jellyfish;

clam shell imprint;

shell fossils;

bone fossil;

image of Archeopteryx;

image of a lobe-finned fish;

image of a mammoth;

phylogenetic series of the horse limb;

limbs of vertebrates;

vestiges;

atavisms;

embryos of fish and mammals.

Protection of research works. (10 min.)

3. Dynamic pause (3 min)

The biogenetic law formulated by Müller and Haeckel reads: "Each species in its individual development repeats to a certain extent the historical development of the species"

How does this happen:

Single cell stage

Bilayer Animals

Swim like fish

They blinked and croaked

Hissed

Climb up a tree

We stood on two legs, straightened our backs and sat down at our desks to study.

4. Learning new material.

Questions for the class:

What are the reasons for the diversity of the animal world?

Has the animal world always been the way it is today?

Having received the answers, supplement and summarize them, saying that for many years these questions have worried the minds of mankind, and in different historical epochs they were answered in different ways. A scientific explanation of the reasons for the diversity of the organic world, its changes and development was given in the second halfXIXin. English scientist C. Darwin.

Life and work of Ch. Darwin (listen to student feedback). (5 minutes.)

Charles Robert Darwin is the grandson of the English natural philosopher, physician and poet Erasmus Darwin, author of the transformist works Zoonomy, or the Laws of Organic Life (1794-1796) and The Temple of Nature, or the Origin of Society.

C. Darwin was born in 1809 in Shrewsbury. He graduated from classical school, entered the medical faculty of the University of Edinburgh, and two years later transferred to the University of Cambridge, where he studied theology and received a bachelor's degree. He makes his first scientific reports in 182601827. in the Pliny Society. He received his naturalistic education under the guidance of botanist J. Huxloe and geologist A. Sedgwick.

In 1831-1836. C. Darwin travels around the world on the ship "Beagle" as a naturalist, collecting the richest zoological, paleontological, botanical and geological collections.

In 1836, having returned from a trip, he left London due to illness and in 1842 moved to his suburb of Down, where he lived for all subsequent years. In 1839, C. Darwin published his famous Diary of Research, where he first described many South American and island animals. This book also touches upon questions of geology and problems of the social and political life of South American Indians and Negroes. Developed the theory of the origin of coral reefs.

In 1842, Darwin made the first draft of The Origin of Species, in which he laid the foundations for a future evolutionary theory, and in 1844 he developed this essay into a significant manuscript. But another 15 years will pass until Charles Darwin publishes the final version of his famous book, The Origin of Species by Means of Natural Selection (1859).

In 1868, C. Darwin published his second major work - "Change in Domestic Animals and Cultivated Plants", in which he cites a lot of additional material to prove the evolutionary idea. This work lays the theoretical foundations of selection.

In 1871, Darwin's third fundamental work, The Descent of Man and Sexual Selection, was published. C. Darwin was a foreign member of the St. Petersburg (since 1876), Berlin (since 1878), and Paris (since 1878) academies of sciences, an honorary member of many scientific societies, and an honorary doctorate from a number of universities. In 1864 he was awarded the medal to them. G. Copley of the Royal Society of London.

The scientist died on April 19, 1882 and was buried in Westminster Abbey, the burial place of many great scientists of England, next to Newton's grave.

Work in groups - 5 groups of 3-4 people, each group is given a card with a question. The group prepares the answer together, one member of the group answers. (3+7 min.)

Using the textbook material pages 256-258, answer the questions

Group 1 - What is heredity?

Group 2 - What is variability?

Group 3 - What forms of variability are known?

Group 4 - What is the struggle for existence?

Group 5 - What is called natural selection?

Group protection.

Heredity is the ability of parents to pass on typical traits to their offspring.

Variability - the ability of organisms to exist in various forms, reacting to the influence of the environment.

Variability forms

definite indefinite

(non-hereditary) (hereditary)

The phenomena of variability have been known for a long time. The ability of organisms to multiply exponentially has long been known.

It was Charles Darwin who compared these two phenomena in nature and made a brilliant conclusion that seems so simple to us now: in the processstruggle for existence, only those organisms survive that differ in some features that are useful under given conditions. Consequently, the probability of survival of individuals is not the same: individuals that have at least a slight advantage over the rest are more likely to survive and leave offspring.

Natural selection is the preservation of animals that are better than others adapted to the conditions of existence in the wild, possessing (in comparison with others) certain advantages of structure or behavior. The living conditions of animals are a selection factor. Natural selection proceeds without interruption for many centuries and leads to the formation of forms that are best adapted to the environment.

Conclusion: Causes of animal evolution

Variability

Heredity

Struggle for existence

Natural selection

5. Consolidation of the studied . (5 minutes)

Run a test

1. Different types of organisms are formed from one:

under different environmental conditions;

under the same conditions;

in both conditions.

2. A possible reason for the conservation of green grasshoppers in a green meadow is due to the fact that:

birds do not eat green grasshoppers;

birds do not see them;

green grasshoppers breed more actively than grasshoppers of a different color.

3. How to explain that sharks, dolphins and penguins are equally well adapted to life in the seas:

hereditary variability and natural selection;

random fitness;

non-hereditary variation.

4. A white hare is not visible on white snow, but it can be seen well on a thawed patch. This proves that adapting it to the environment:

useless;

Harmful;

relative.

6. Homework: § 50, questions at the end of the paragraph. Give examples of the causes of evolution from the life of animals.

7. Self-esteem

8. Reflection

Evolution is a development process consisting of gradual changes, without sharp jumps (as opposed to revolution). Most often, when speaking of evolution, they mean biological evolution. Biological evolution is an irreversible and directed historical development of living nature, accompanied by a change in the genetic composition of populations, the formation of adaptations, speciation and extinction of species, the transformation of ecosystems and the biosphere as a whole.

Charles Robert Darwin (1809-1882) is the founder of evolutionary biology. C. Darwin is also the author of a number of major works on botany, zoology, geology, and comparative psychology. Charles Darwin's teaching is based on a large amount of factual material collected during the journey and proving the validity of his theory, as well as on scientific achievements (geology, chemistry, paleontology, comparative anatomy, etc.), primarily in the field of selection. Darwin first began to consider evolutionary transformations not in individual organisms, but in a species or intraspecific groups.

Variability. The starting point of Darwin's teaching is his statement about the presence of variability in nature. Variability is the general property of organisms to acquire new characteristics - differences between individuals within a species.

Analyzing the material on the variability of animals, the scientist noticed that any change in the conditions of detention is enough to cause variability. He distinguished two main forms of variability: group, or definite, and individual, or indefinite. With group, specific, but not hereditary variability, many individuals of a given breed or variety, under the influence of a specific cause, change in the same way. So, for example, the growth of organisms depends on the amount of food, color - on its quality. Under individual, indefinite, hereditary variability, one should understand those small differences by which individuals of the same species differ from each other. These are changes that occur as a result of an indefinite effect of the conditions of existence on each individual, such changes appear in animals of the same litter, in plants grown from the seeds of one box. The uncertainty of these changes lies in the fact that under the influence of the same conditions, individuals change in different ways.

Heredity. All organisms in nature have heredity. This property is expressed in the preservation and transmission of traits to offspring. Darwin attached great importance to the presence of variability and heredity in nature. Variability and heredity, combined with selection, is a natural factor in evolution.

Darwin paid much attention to the study of various varieties of cultivated plants. So, comparing various varieties of cabbage, he concluded that they were all bred by man from one wild species. In what way is this achieved? Darwin noticed that in all cases the breeders used the same technique. Breeding animals or plants, they left for reproduction only the specimens that best suited their needs, and from generation to generation they accumulated changes useful to humans. This method of obtaining breeds and varieties is called artificial selection.

artificial selection. The success of artificial selection depends on the degree of variability of the original form: the more the characters change, the easier it is to find the necessary changes.

Darwin pointed out the conditions conducive to artificial selection: A high degree of variability in organisms. A large number of individuals subject to selection. The art of the breeder. Elimination of random individuals. Sufficiently high value of these animals or plants for humans.

Natural selection The most important place in the theory of natural selection is occupied by the concept of the struggle for existence. According to Darwin, the struggle for existence is the result of the tendency of organisms of any kind to multiply without limit. A predator, in order to live, must eat, and herbivores serve as food for it. A herbivore, in order to live, eats many thousands of meadow plants. Plants are destroyed by insects. Insects are food for insectivorous birds, which in turn are exterminated by birds of prey. These complex relationships Darwin called the struggle for existence.

Various manifestations of the struggle for existence Darwin reduced to three types: interspecific, intraspecific and the struggle against the conditions of the inorganic external environment. natural selection is a process that occurs in nature, in which, as a result of the impact of environmental conditions on developing organisms, individuals with useful traits are preserved that increase survival in given environmental conditions and cause their higher fertility.

In his work "The Origin of Species ..." Darwin noted the most important feature of the evolutionary process - its adaptive character.

Evolutionary changes in the vertebrate skeleton. Species are constantly adapting to the conditions of existence, and the organization of any species is constantly being improved. The merit of the evolutionary doctrine is the explanation of this perfection of organisms as the result of the historical accumulation of adaptations.

Conclusions: Biological evolution is an irreversible and to a certain extent directed historical development of living nature, accompanied by a change in the genetic composition of populations, the formation of adaptations, the formation and extinction of species, the transformation of ecosystems and the biosphere as a whole. Biological evolution is determined by variability, heredity, natural selection of organisms that occur against the background of changes in the composition of ecosystems. (lat. Evolutio - development)