Scientific evidence evolution (embryological, morphological, paleontological, biogeographic, etc.)

Embryological evidence

In all vertebrates, there is a significant similarity of embryos in early stages development: they similar shape bodies, there are rudiments of gill arches, there is a tail, one circle of blood circulation, etc. However, as development progresses, the similarity between the embryos of different systematic groups gradually decreases, and features characteristic of their classes, orders, families, genera begin to predominate, and, finally, species

Evolutionary changes can affect all phases of ontogenesis, that is, they can lead to changes not only in mature organisms, but also in embryos, even in the first stages of development. However, earlier phases of development should be more conservative than later ones, since changes at earlier stages of development should in turn lead to greater changes during later development. For example, a change in the type of cleavage will cause changes in the process of gastrulation, as well as in all subsequent stages. Therefore, changes that appear in the early stages are much more likely to be lethal than changes that occur in later periods of ontogenesis.

Thus, the early stages of development change relatively rarely, which means that by studying embryos of different species, it is possible to draw conclusions about the degree of evolutionary relatedness.

In 1837, embryologist Karl Reichert discovered from which embryonic structures the quadrate and articular bones in the jaw of reptiles develop. The same structures are found in mammalian embryos, but they develop into the malleus and incus of the middle ear. The fossil record also confirms the origin of parts of the mammalian ear from the jaw bones reptiles.

There are many other examples of how the evolutionary history of an organism is revealed during its development. Mammalian embryos at early stages have gill sacs, indistinguishable in structure from the gill sacs of aquatic vertebrates. This is explained by the fact that the ancestors of mammals lived in water and breathed with gills. Of course, the gill pouches of mammalian embryos do not develop into gills during development, but into structures that evolved from gill slits or the walls of gill pouches, such as the eustachian tubes, middle ear, tonsils, parathyroid glands and thymus.

The embryos of many species of snakes and legless lizards (for example, the brittle spindle) develop the rudiments of limbs, but then they are resorbed. Similarly, whales, dolphins and porpoises do not have hind limbs, but in cetacean embryos, hind legs begin to grow, develop bones, nerves, blood vessels, and then all these tissues are resorbed.

Darwin cited the presence of teeth in the embryos of baleen whales as an example.

Biogeographical evidence

Among Australia's mammals, marsupials predominate. Placental mammals include cetaceans, pinnipeds and bats (which could have moved to Australia relatively easily), as well as rodents, which appear in the fossil record in the Miocene, when Australia approached New Guinea. Wherein natural conditions Australia is also favorable for other mammal species. For example, rabbits introduced to the continent quickly multiplied, spread widely and continue to displace native species. In Australia and New Guinea, in the south South America and in Africa, flightless ratites, whistlers (toothed toads) and lungfishes are found; in other parts of the world they are absent. Living conditions in the deserts of Africa, America and Australia are very similar, and plants from one desert grow well in another. However, cacti have only been found in America (with the exception of Rhipsalis baccifera, apparently brought to the Old World by migratory birds). Many African and Australian succulents (that is, plants with special tissues for storing water) superficially resemble cacti due to convergent evolution, but belong to different orders. The marine life of the eastern and western coasts of South America is different, with the exception of some mollusks, crustaceans and echinoderms, but about 30% of the same fish species live on opposite shores of the Isthmus of Panama, which is explained by the recent emergence of the isthmus (about 3 million years ago). Most oceanic islands (that is, islands that have never been connected to the mainland) lack land mammals, amphibians and other animals that are unable to overcome significant water obstacles. Species composition The fauna of such islands is poor and is the result of the accidental introduction of certain species, usually birds, reptiles, and insects.

The geographical distribution of species in the past, which can be partially reconstructed from fossil remains, must also correspond to the phylogenetic tree. The theory of continental drift and the theory of evolution make it possible to predict where certain fossil remains should be found. The first marsupial fossils were found in North America, their age is about 80 million years. 40 million years ago, marsupials were already common in South America, but in Australia, where they now dominate, marsupials appeared only about 30 million years ago. Evolutionary theory predicts that Australian marsupials are descended from American marsupials. According to the theory of continental drift, 30-40 million years ago, South America and Australia were still part of Gondwana, large continent in the southern hemisphere, and between them was the future Antarctica. Based on two theories, researchers predicted that marsupials migrated from South America to Australia via Antarctica 30-40 million years ago. This prediction came true: since 1982, more than ten fossil marsupials aged 35-40 million years have been found on Seymour Island, located near Antarctica.

Closest relatives modern people- gorillas and chimpanzees live in Africa. Based on this, in 1872 Charles Darwin suggested that the ancient ancestors of man should be sought in Africa. Many researchers, such as Louis, Mary and Richard Leakey, Raymond Dart and Robert Broome, followed Darwin's advice, and starting in the 1920s, many intermediate forms between humans and apes were found in Africa. If fossil australopithecines had been discovered, for example, in Australia, and not in Africa, then ideas about the evolution of hominids would have to be revised.

Morphological evidence

In the course of evolution, each new organism is not designed from scratch, but is derived from an old one through a sequence of small changes. The structures formed in this way have a number of characteristic features that indicate their evolutionary origin. Comparative anatomical studies make it possible to identify such features.

In particular, evolutionary origin excludes the possibility of purposefully borrowing successful designs from other organisms. Therefore, different, not closely related species use different organs to solve similar problems. For example, the wing of a butterfly and the wing of a bird develop from different germ layers, the wings of birds are modified forelimbs, and the wings of a butterfly are folds of chitinous cover. The similarity between these organs is superficial and is a consequence of their convergent origin. Such organs are called analogous.

The opposite situation is observed in closely related species: organs with similar structures are used for completely different tasks. For example, the forelimbs of vertebrates perform a variety of functions, but at the same time they have a common structural plan, occupy a similar position and develop from the same rudiments, that is, they are homologous. The similarity in the structure of a bat's wing and a mole's paw cannot be explained in terms of utility. At the same time, the theory of evolution provides an explanation: four-legged vertebrates inherited a single limb structure from a common ancestor.

Each species inherits from the ancestral species most of its properties - including sometimes those that are useless for the new species. Changes usually occur due to the gradual sequential transformation of the characteristics of the ancestral species. The similarity of homologous organs, not related to the conditions of their functioning, is evidence of their development during evolution from a common prototype present in the ancestral species. Other examples of evolutionary changes in morphology are rudiments, atavisms, as well as numerous cases of specific imperfections in the structure of organisms.

Homologous organs

Homology (biology)

Five-fingered limb

Using mammals as an example:

In monkeys, the forelimbs are elongated, the hands are adapted for grasping, which makes climbing trees easier.

The pig's first toe is missing, and the second and fifth are reduced. The remaining two fingers are longer and harder than the others, the terminal phalanges are covered with hooves.

The horse also has a hoof instead of claws, the leg is elongated due to the bones of the middle finger, which contributes to high speed of movement.

Moles have shortened and thickened fingers, which help with digging.

The anteater uses its large middle finger to dig out anthills and termite nests.

In whales, the forelimbs are fins. Moreover, the number of phalanges of the fingers is increased compared to other mammals, and the fingers themselves are hidden under soft tissues.

In the bat, the forelimbs are modified into wings by significantly elongating the four digits, and the hook-shaped first digit is used to hang on trees.

Moreover, all these limbs contain a similar set of bones with the same relative arrangement. The unity of structure cannot be explained in terms of utility, since the limbs are used for completely different purposes.

Parts of insect mouthparts

The main parts of the oral apparatus of insects are the upper lip, a pair of mandibles (upper jaws), the subpharynx, two maxillae (lower jaws) and the lower lip (fused second maxillae). These components vary in shape and size in different species, and in many species some of the parts are lost. The structural features of the oral apparatus allow insects to use various food sources (see figure):

In their original form (for example, in a grasshopper), strong mandibles and maxillae are used for biting and chewing.

Honey bee uses the lower lip to collect nectar, and crushes pollen and kneads wax with its mandibles.

In most butterflies, the upper lip is reduced, mandibles are absent, and the maxillae form a proboscis.

In female mosquitoes, the upper lip and maxillae form a tube, and the mandibles are used to pierce the skin.

Similar bodies

Externally similar organs or parts thereof, originating from different initial rudiments and having a different internal structure, are called analogous. External similarity arises in the course of convergent evolution, that is, in the course of independent adaptation to similar conditions of existence.

The wings of birds are modified forelimbs, the wings of insects are folds of chitinous cover.

The gills of fish are formations associated with the internal skeleton, the gills of many crustaceans are outgrowths of the limbs, the ctenidial gills of mollusks develop in the mantle cavity, and the gills of nudibranchs are outgrowths of the integument of the dorsal side of the body.

Streamlined body shape in aquatic mammals - whales, dolphins - and fish.

The spines of barberry and cactus are modified leaves; the spines of hawthorn develop from shoots.

Grape tendrils (formed from shoots) and pea tendrils (modified leaves).

The shape of various succulents (plants that have special tissues to store water), such as cacti and milkweed.

The complete absence of purposeful borrowing of successful designs distinguishes evolution from conscious design. For example, a feather is a good design that helps with flight, but mammals (including bats) do not have feathers. Gills are extremely useful for aquatic animals, but mammals (such as cetaceans) lack them. To falsify the theory of evolution, it is enough to discover feathers or gills in any species of mammals.

Rudiments

Rudiments are organs that have lost their basic significance during the process of evolutionary development body. If a rudiment turns out to be functional, then it performs relatively simple or unimportant functions with the help of structures intended for more complex purposes

For example, a bird's wing is an extremely complex anatomical structure specially adapted for active flight, but ostrich wings are not used for flight. These vestigial wings can be used for relatively simple tasks, such as maintaining balance while running and attracting females. For comparison, the winged penguin has great importance, acting as a fin, and therefore cannot be considered a rudiment.

The eyes of some cave and burrowing animals, such as proteus, mole rat, mole, and Astyanax mexicanus, blind cave fish. Often the eyes are hidden under the skin.

Tibia in birds.

Remains of hair and pelvic bones in some cetaceans.

Some snakes, including the python, have hind limb bones. These bones are not attached to the spine and move relatively freely in the abdominal cavity.

In many beetle species, such as Apterocyclus honoluluensis, the wings lie under fused elytra.

In humans, the rudiments include, in particular, the caudal vertebrae, the hair of the body, the ear muscles, the tubercle of the auricle, and the Morganian ventricles of the larynx.

The vermiform appendix of the cecum (appendix) in some herbivores is used to digest plant food and is long. For example, a koala's appendix is ​​1 to 2 meters long. The human appendix has a length of 2 to 20 centimeters and is not involved in the breakdown of food. Contrary to popular belief, the presence of secondary functions in the appendix does not mean that it is not a vestige.

Atavisms

Atavism is the appearance in an individual of characteristics characteristic of distant ancestors, but absent in nearby ones. The appearance of atavisms is explained by the fact that the genes responsible for this trait are preserved in DNA, but normally do not form structures typical of ancestors.

Examples of atavisms:

Caudal appendage in humans;

Continuous hair on the human body;

Additional pairs of mammary glands;

The hind legs of whales;

The hind fins of dolphins;

Hind legs of snakes;

Extra toes in horses

The arguments for evolution are similar to those for vestiges.

Paleontological evidence

As a rule, the remains of plants and animals decompose and disappear without a trace. But sometimes biological tissues are replaced minerals, and fossils are formed. Usually found are fossilized bones or shells, that is, solid parts of living organisms. Sometimes prints of animal tracks or traces of their vital activity are found. It is even less common to find an entire animal frozen in ice in areas of modern permafrost, trapped in the later fossilized resin of ancient plants (amber) or in another natural resin - asphalt.

Paleontology is the study of fossil remains. Typically, sedimentary rocks are deposited in layers, so deeper layers contain fossils from an earlier period (superposition principle). This means that by comparing fossil forms from successive strata, we can draw conclusions about the main directions of the evolution of living organisms. Numerous geochronological techniques are used to estimate the age of fossils.

When looking at the fossil record, we can conclude that life on Earth has changed significantly. The deeper we look into the past, the less we see in common with the modern biosphere. The first prokaryotes (the simplest single-celled organisms that do not have a formed cell nucleus) appear approximately 3.5 billion years ago. The first unicellular eukaryotes appear 2.7-1.75 billion years ago. About a billion years later, 840 million years ago, the first multicellular animals, representatives of the Hainan fauna, appear in the fossil record. According to a study published in 2009, multicellular organisms belonging to one of the species were probably already present more than 635 million years ago. modern types- sponges. During the “Cambrian explosion”, 540-530 million years ago, in a geologically short period of time, remains of representatives of most modern types with skeletons appear in the geological record, and after another 15 million years - the first primitive vertebrates, similar to modern lampreys. Jawed fishes appeared 410 million years ago, insects - 400 million years ago, and for another 100 million years ferns dominated on land, and insects and amphibians remained the main groups of terrestrial fauna. From 250 to 65 million years ago on Earth, the dominant position of “top predators” and large herbivores was occupied by dinosaurs and other reptiles; the most common plants were cycads and other groups of gymnosperms. The first fossil remains of flowering plants appear 140-130 million years ago, and the beginning of their widespread distribution dates back to the mid-Cretaceous period (about 100 million years ago). The observed picture corresponds to the origin of all species from single-celled organisms and has no other scientific explanation.

Well-known evidence of evolution is the presence of so-called intermediate forms, that is, organisms that combine the characteristic features of different species. As a rule, when talking about intermediate (or “transitional”) forms, they mean fossil species, although intermediate species do not always go extinct. Based on the phylogenetic tree, the theory of evolution predicts which intermediate forms can be found and which cannot. In accordance with scientific method, the predictions that came true confirm the theory. For example, knowing the structure of the organisms of reptiles and birds, one can predict some features of the transitional form between them. One can predict the possibility of finding the remains of animals similar to reptiles, but with feathers, or the remains of animals similar to birds, but with teeth, or with long tails with a skeleton of unfused vertebrae. It can be predicted that transitional forms between birds and mammals will not be found, for example - fossil mammals with feathers or bird-like fossils with middle ear bones like mammals.

Shortly after the publication of The Origin of Species, the remains of Archeopteryx, an intermediate form between reptiles and birds, were discovered. Archeopteryx is characterized by differentiated plumage (a typical bird feature), and in terms of skeletal structure it differed little from dinosaurs from the group of compsognaths. It had claws on the forelimbs, teeth and a long tail with a skeleton of unfused vertebrae, and the supposed unique "avian" skeletal features were subsequently identified in other reptiles. Later, other transitional forms between reptiles and birds were found.

Many other transitional forms are known, including from invertebrates to fish, from fish to tetrapods, from amphibians to reptiles, and from reptiles to mammals.

In some cases, fossil transitional forms could not be found, for example - there are no traces of the evolution of chimpanzees (presumably this is due to the lack of conditions for the formation of fossils in the forests where they live), there are no traces eyelash worms, and this class unites more than 3,500 species. Of course, to falsify the theory of evolution, it is not enough to point out such gaps in the fossil record. To refute evolutionary doctrine, it would be necessary to present a skeleton that does not correspond to the phylogenetic tree or does not fit into the chronological sequence. Thus, in response to a question about what discovery could falsify evolutionary theory, John Haldane snapped: “Fossil rabbits in the Precambrian!” Millions of fossils have been found [about 250,000 fossil species, and each find is a test of the theory of evolution, and the test passed confirms the theory.

In cases where the fossil record turns out to be particularly complete, it becomes possible to construct so-called phylogenetic series, that is, series of species (genera, etc.), successively replacing each other in the process of evolution. The best known are the phylogenetic series of humans and horses (see below), and the evolution of cetaceans can also be cited as an example.

At all times, humanity has been divided into those who consider themselves supporters of the theory of evolution, and those who consider themselves its opponents. Modern science has accumulated enough factual material that illustrates the evidence of evolution. Embryological studies provide enormous food for thought.

It is about the stages of development of the embryo of various phylogenetic groups of animals that we will talk about in this article and give examples of embryological evidence of evolution in the animal world.

Introduction to general theory

In biology, the concept of “evolution” refers to the long process of the development of life on Earth. As a result the most complex process a whole variety of living forms was formed, clearly adapted to the conditions of their existence.

There are morpho-physiological, genetic, microbiological, paleontological and embryological evidence of evolution.

Embryology is a biological science that studies the development of an embryo from a zygote to the birth of a baby. This includes the development of fry in fish eggs, the development of chicks in bird eggs, and the development of a baby in the womb.

Stages of development as evidence base

Embryological evidence of evolution is considered to be:

• The similarity of the stages of development of the embryo of different phylogenetic groups of animals in the early stages of embryonic formation.
• The Muller-Haeckel law states that an individual repeats in embryogenesis the history of the emergence of its species.
• All panmictic (different sexes and sexually reproducing) organisms begin their development with a zygote - a fertilized egg. This is one of the main embryological evidence of evolution.

Mechanism of embryogenesis

It is important to understand that changes do not affect the body itself, but genetically programmed programs. The embryonic development programs of a particular organism (ontogenesis), as a rule, embryonic stage much simpler than adult development programs. The embryo develops through self-organization, when the next stage of development is launched through the previous one. Activator genes are already being studied quite successfully in practical molecular biology.

Embryogenesis stages

As already mentioned, the development of individuals of panmictic species begins from the moment of conception (fertilization of female gametes by male ones). The resulting zygote begins to divide. The following stages are distinguished in embryogenesis:

• Formation of a zygote (fertilization).
• The morula stage is when the zygote has divided into 32 cells (blastomeres). All morula cells are identical and pluripotent (can develop into a separate organism).
• The blastula stage, when there are already 128 blastomeres. The embryo is a single-layer ball of cells that have lost the properties of pluripotency, with a cavity inside (blastocoel).
• Gastrula stage. This is a two-layer embryo. The invagination of blastula cells forms the outer layer (ectoderm) and inner layer (endoderm) of the embryo.
• When a layer of mesoderm forms between the ecto- and endodermal layers, the stage is called blastula. The embryo acquires three layers, and the layers are called germ layers. It is from them that the tissues, organs and organ systems of the future organism will be formed.

From zygote to blastula

At the morula stage of the embryo, it is difficult to determine its species. And even up to the blastula stage, embryos different groups difficult to distinguish.

At the stage of laying the germ layers, differences begin that are characteristic of the embryos of organisms of a phylogenetic group. The stages of zygote fragmentation in the initial stages of embryogenesis are the same and completely uniform for all multicellular animals. And this is indisputable embryological evidence of the evolution of multicellular organisms.

Further - more difficult

After the formation of the gastrula and germ layers, cell differentiation begins. However, in a homogeneous phylogenetic group, the similarity in the formation and formation of body parts and organs is preserved. This clearly illustrates the development of the embryo of vertebrates. Proof of evolution is the embryological features of the similarity in the structure and formation of the multicellular embryo. For example, all vertebrates have a clear demarcation of the head, trunk and caudal parts of the body, rudimentary gills, a tail and a primary single circulation.

The history of evolution in embryo

Based on embryological data, it is possible to trace the entire course of evolution of a particular organism. It was this law that was introduced into biology by F. Müller and E. Haeckel: ontogeny is a short and rapid repetition of phylogeny. For example, all mammalian embryos have rudiments of gill arches and sacs. They later develop into the middle ear, tonsils, thymus and thyroid glands. But the location of the blood and nerve pathways is preserved. That is why the laryngeal recurrent nerve of mammals runs from the brain along the larynx to the aorta, goes around it and returns to the larynx. This is how the circle is innervated nerve fibers around the gills of fish, which is embryological evidence of the evolution of mammals from aquatic ancestors.

A few more examples

As an illustration of the above: you can see the presence of teeth in the embryo of a baleen whale. And in the embryo of some snakes, rudimentary lower limbs develop, which dissolve in late embryogenesis. Whales, even in adulthood, have rudimentary hind limbs, which are represented by several bones. A human embryo at 4 weeks of age has a tail of 10-12 vertebrae, and its length is about 10% of the length of the entire embryo. During embryogenesis, part of the vertebrae dissolves, leaving a person with only the coccyx - 4 caudal vertebrae.

It is impossible to prove modern ideas about the evolution of life by direct methods. The experiment will last for millions of years ( civilized society no more than 10 thousand years old), and a time machine most likely will never be invented. How is truth obtained in this area of ​​knowledge? How to approach the burning question “Who came from whom”?

Modern biology has already accumulated a lot of indirect evidence and considerations in favor of evolution. Living organisms have common features- biochemical processes proceed in a similar way, there are similarities in external and internal structure and in individual development. If the embryos of a turtle and a rat are indistinguishable in the early stages of development, then is this suspicious similarity a hint of a single ancestor from which these animals descended over millions of years? It is about the ancestors of modern species that paleontology - the science of the fossil remains of living beings - will tell. Interesting Facts, giving food for thought, provides biogeography - the science of the distribution of animals and plants.

EVIDENCE OF EVOLUTION
Morphological
Embryological
Paleontological
Biochemical
Biogeographic

1. Biochemical evidence of evolution.

1. All organisms, be they viruses, bacteria, plants, animals or fungi, have a surprisingly similar elementary chemical composition.

2. For all of them, proteins and nucleic acids play a particularly important role in life phenomena, which are always built according to a single principle and from similar components. A high degree of similarity is found not only in the structure of biological molecules, but also in the way they function. The principles of genetic coding, biosynthesis of proteins and nucleic acids are the same for all living things.

3. The vast majority of organisms use ATP as energy storage molecules; the mechanisms for breaking down sugars and the main energy cycle of the cell are also the same.

4.Most organisms have a cellular structure.

2.Embryological evidence of evolution.

Domestic and foreign scientists have discovered and deeply studied the similarities in the initial stages of embryonic development of animals. All multicellular animals go through the blastula and gastrula stages during individual development. The similarity of embryonic stages within individual types or classes is particularly clear. For example, in all terrestrial vertebrates, as well as in fish, the formation of gill arches is found, although these formations have no functional significance in adult organisms. This similarity of embryonic stages is explained by the unity of origin of all living organisms.

3. Morphological evidence of evolution.

Of particular value for proving the unity of the origin of the organic world are forms that combine the characteristics of several large systematic units. The existence of such intermediate forms indicates that in previous geological eras there lived organisms that were the ancestors of several systematic groups. A clear example of this is the single-celled organism Euglena verida. It simultaneously has characteristics typical of plants and protozoa.

The structure of the forelimbs of some vertebrates, despite the performance of completely different functions by these organs, is fundamentally similar in structure. Some bones in the skeleton of the limbs may be absent, others may be fused, the relative sizes of the bones may vary, but their homology is quite obvious. Homologous These are organs that develop from the same embryonic rudiments in a similar way.

Some organs or their parts do not function in adult animals and are superfluous for them - these are the so-called vestigial organs or rudiments. The presence of rudiments, as well as homologous organs, is also evidence of a common origin.

4. Paleontological evidence of evolution.

Paleontology points to the causes of evolutionary transformations. The evolution of horses is interesting in this regard. Climate change on Earth has caused changes in the horse's limbs. In parallel with the change in the limbs, a transformation of the entire organism took place: an increase in body size, changes in the shape of the skull and complication of the structure of the teeth, the emergence of a digestive tract characteristic of herbivorous mammals, and much more.

As a result of changes in external conditions influenced natural selection There was a gradual transformation of small five-toed omnivores into large herbivores. The richest paleontological material is one of the most convincing evidence of the evolutionary process that has been going on on our planet for more than 3 billion years.

5. Biogeographic evidence for evolution.

A clear indication of the evolutionary changes that have occurred and are ongoing is the spread of animals and plants across the surface of our planet. Comparison of animal and flora different zones gives the richest scientific material to prove the evolutionary process. The fauna and flora of the Paleoarctic and Neoarctic regions have much in common. This is explained by the fact that in the gap between the named areas there was a land bridge - the Bering Isthmus. Other areas have little in common.

Thus, the distribution of animal and plant species over the surface of the planet and their grouping into biographical zones reflects the process historical development Earth and the evolution of living things.

Island fauna and flora.

To understand the evolutionary process, the flora and fauna of the islands are of interest. The composition of their flora and fauna depends entirely on the history of the origin of the islands. A huge number of diverse biographical facts indicate that the characteristics of the distribution of living beings on the planet are closely related to the transformation of the earth's crust and to the evolutionary changes of species.

Many people around the world are interested in evidence of evolution. Since childhood, each of us has been surrounded by a variety of people - from Christian believers to lovers of fantastic stories about aliens and other categories of citizens who attribute the most amazing origin stories to humans.

In practice, few people are able to accept the simple idea that man is a creation of nature, and, like any other organism on the planet, developed gradually from simpler forms to the one in which he exists now.

The most fierce debates constantly arise on this topic, in which each theory finds its fans. But it is worth clearly recognizing the fact that it is the admirers of the theory of evolution who have the most trump cards in their hands, and only they are able to provide truly scientific and fully substantiated confirmation of their view on this issue.

The evidence for evolution is abundant and constantly updated. It is very, very difficult to argue with them. Let's look at all this in more detail.

Embryological evidence for evolution

A group of evidence of the correctness of the theory of evolution, which is derived from observations of the development of the fetus of an unborn child, is called embryological evidence. In the mid-19th century, scientists noticed that at different stages of formation human body in the womb it is very similar to others, more simple shapes life on earth.

Human embryo (6 weeks)

For example, at the beginning of its development, a person has the rudiments of gills, characteristic of creatures living in water; a very specific tail is observed in the body, which in the future is simply covered by other tissues, remaining with the person for the rest of his life in the form of a coccyx; the embryo has only one circuit for blood circulation, which is also characteristic of creatures of lower development.

Example. The early state of the middle ear system turned out to be a late stage in the degeneration of the lower jaw of reptiles.

It has been noticed that in its embryonic development the fetus goes through states that largely connect it with different systematic groups creatures, gradually narrowing down to more specific classes, orders, families, genera, and last of all comes to its native species - homo sapiens.

Embryonic evidence in itself is quite eloquent and fully confirms the theory of evolution. But their problem is that they are accessible to scientific observation and understanding mainly by scientists and more educated people close to them. That's why common man they can be difficult to break through.

Comparative anatomical evidence of evolution

The group of evidence for evolution, which is based on the similarity of certain parts of the body and characteristics of man with other animals and his supposed ancestors, is called comparative anatomical.

This group is divided into the following narrower sections:

1. Vestigial organs. These are those parts of the body of our species that were important for distant ancestors, but now they have lost their relevance and are not used for any actions and processes. An example is appendicitis. This is a classic rudiment that is completely unnecessary for a person in life and was inherited from the ancestors of mammals, in whom it played the role of the cecum. Exactly the same rudiment is the falcon - the remnant of the tail, which gradually became smaller and was eventually completely hidden. There are cases when people were born with an enlarged coccyx, which looked like a real tail, albeit small in size. It had to be removed through surgery.
2. Homologous organs. Various animals and humans have a lot of organs and systems that are almost identical in structure, but in the process of evolutionary development they could acquire slightly different appearances. Such organs have exactly the same origin and similar structure. An example is the wings of a bat and the hand of a person, the flippers of a whale, which have the same bones and functional parts.
3. Similar organs. Another group of evidence, the essence of which is that many organs in humans and animals have completely different evolutionary origins, but ultimately play the same role. An example is that the eyes of mollusks develop from an elongation of the ectodermal layer, while in vertebrates the eyes originate from the lateral processes of the brain.
4. Another large group of comparative anatomical evidence is atavisms. Atavisms are characteristics of a person that return him to the characteristics of his ancestors. Examples are excessive hairiness, which refers us to monkeys; more than two nipples on the human chest, which recalls kinship with other mammals; some people can move their ears like animals, and much more.

Comparative anatomical facts are quite telling and do not even require serious justification. After all, it is enough for us to see a person whose physiognomy is very similar to a gorilla, and thoughts about evolution begin to suggest themselves.

Biogeographic evidence for evolution

Biogeography studies the development of existing life forms in different parts of the planet, on different continents, living in the most dissimilar conditions and climates. With the help of such studies, it is possible to identify an interesting pattern - creatures living in the same climate, but on different parts of the earth, can differ significantly.

This is direct proof that everywhere the game of evolution is quite unpredictable, and it gives rise to a variety of variants of living beings in a chaotic creative disorder.

This can be observed both in representatives of the plant world and in animals. The essence of this type of evidence is to indicate that the animal and plant world of the entire planet originated at one point, but later, as a result of migration and isolation of groups from each other, they evolved in different ways.

An example is cichlid fish in Lake Malawi, where the water is clean and clear, have a purple or blue color, and in Lake Victoria, where the waters are muddy, yellow. This is how this species adapted to living conditions.

Paleontological evidence of evolution

Paleontology has made a huge contribution to the development of the theory of evolution, as it deals with the search and study of the remains of ancient organisms.

Scientists' findings once again prove that humans and other modern creatures have many similarities with their extinct ancestors, a similar skeletal structure, and some of its parts have changed. Something goes away due to uselessness, something appears, but there is always a connection between the ancestor and the modern organism.

A big problem in paleontology is the discovery of transitional forms. There is a well-known scandal when the fidelity of evolution was called into question by the fact that the intermediate link between ape and man has not yet been discovered. An example is the evolution of cetaceans, which has been studied step by step by paleontologists.

Morphological evidence

This group of evidence boils down to comparison appearance organisms and searching for similarities between them. For example, comparing skulls different types monkeys and humans, you can find a lot of similar and even common characteristics between them.

Morphophysiological facts can be so obvious that trying to dispute them is simply stupid and completely pointless.

Biochemical evidence

More subtle studies that are carried out at the level of cells, DNA, further confirm the unity of all living organisms on earth. Interestingly, this applies not only to animals, but also to plants. Do you think this plays an important role in proving evolution?

There are about 100 different nucleotides in nature, but there are only 4 of them in the DNA of absolutely any organism. Of the almost 400 types of amino acids available on the planet, only the same 22 amino acids can be found in the protein of any organism.

Any comparative table will show that all living organisms largely consist of the same chemical set, although the surrounding diversity is much greater.

Example - the metabolism of all organisms occurs along the same path, using the same enzymes.

Relic evidence

Those who are not satisfied with all of the above, including biographical, chemical and other facts, can turn to relic evidence, which lies in the fact that even now on earth there are some types of organisms that were inherent in the very ancient world.

Examples. On the islands of New Zealand you can find an amazing animal - the hatteria, which is very similar to the dinosaurs that lived 70-80 million years ago. The ginkgo tree is another example; it existed about 150 million years ago.

Conclusion

As a conclusion, we note that cytological, molecular genetic, paleontological and other studies directly indicate the correctness of the theory of evolution and its complete adequacy in relation to reality. Many people do not want to accept this point of view and have every right to do so.

One way or another, evolution is a reality, proven by millions of facts and simply common sense and observation, and perhaps in the future it will triumph on a much larger scale than now.

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§ 17. Evidence of evolution

To substantiate the theory of evolution, Charles Darwin widely used numerous evidence from the fields of paleontology, biogeography, and morphology. Subsequently, facts were obtained that recreated the history of the development of the organic world and served as new evidence of the unity of the origin of living organisms and the variability of species in nature.

Paleontological finds- perhaps the most convincing evidence of the evolutionary process. These include fossils, imprints, fossil remains, fossil transitional forms, phylogenetic series, sequence of fossil forms. Let's take a closer look at some of them.

1. Fossil transitional forms- forms of organisms that combine the characteristics of older and younger groups.

Of particular interest among plants are psilophytes. They originated from algae, were the first of the plants to make the transition to land and gave rise to higher spore and seed plants. Seed ferns- a transitional form between ferns and gymnosperms, and cycads - between gymnosperms and angiosperms.

Among fossil vertebrates, one can distinguish forms that are transitional between all classes of this subtype. For example, the oldest group lobe-finned fish gave rise to the first amphibians - stegocephalus(Fig. 3.15, 3.16). This was possible due to the characteristic structure of the skeleton of the paired fins of lobe-finned fish, which had the anatomical prerequisites for their transformation into the five-fingered limbs of primary amphibians. Forms are known that form the transition between reptiles and mammals. These include beast lizards(foreigner disease) (Fig. 3.17). And the connecting link between reptiles and birds was per-bird(Archaeopteryx) (Fig. 3.18).

The presence of transitional forms proves the existence of phylogenetic connections between modern and extinct organisms and helps in building a natural system and family tree of the flora and fauna.

2. Paleontological series- series of fossil forms related to each other in the process of evolution and reflecting the course of phylogenesis (from the Greek. phylon- clan, tribe, genesis- origin). A classic example of the use of series of fossil forms to elucidate the history of a particular group of animals is the evolution of the horse. Russian scientist V.O. Kovalevsky (1842-1883) showed the gradual evolution of the horse, establishing that successive fossil forms became increasingly similar to modern ones (Fig. 3.20).

Modern one-toed animals descended from small five-toed ancestors who lived in forests 60-70 million years ago. Climate change has led to an increase in the area of ​​steppes and the spread of horses across them. Movement over long distances in search of food and protection from predators contributed to the transformation of the limbs. At the same time, the size of the body and jaws increased, the structure of the teeth became more complex, etc.

To date, a sufficient number of paleontological series are known (proboscis, carnivores, cetaceans, rhinoceroses, some groups of invertebrates), which prove the existence of an evolutionary process and the possibility of the origin of one species from another.

Morphological evidence are based on the principle: the deep internal similarity of organisms can show the relationship of the compared forms, therefore, the greater the similarity, the closer their relationship.

1. Homology of organs. Organs that have a similar structure and common origin are called homologous. They occupy the same position in the animal’s body, develop from similar rudiments and have the same structural plan. A typical example of homology is the limbs of terrestrial vertebrates (Fig. 3.21). Thus, the skeleton of their free forelimbs necessarily has a humerus, a forearm, consisting of the radius and ulna, and a hand (wrist, metacarpus and phalanges of the fingers). The same pattern of homology is observed when comparing the skeleton of the hind limbs. In the horse, the stylus bones are homologous to the metacarpal bones of the second and fourth fingers of other ungulates. It is obvious that in the modern horse these toes have disappeared during the process of evolution.

It has been proven that the poisonous glands of snakes are a homologue of the salivary glands of other animals, the sting of a bee is a homologue of the ovipositor, and the sucking proboscis of butterflies is a homologue of the lower pair of jaws of other insects.

Plants also have homologous organs. For example, pea tendrils, cactus and barberry spines are modified leaves.

Establishing the homology of organs allows us to find the degree of relationship between organisms.

2. Analogy.Similar bodies- these are organs that are externally similar and perform the same functions, but have different origins. These organs indicate only a similar direction of adaptation of organisms, determined in

the process of evolution through the action of natural selection. External gills of tadpoles, gills of fish, polychaetes annelids and aquatic insect larvae (eg dragonflies) are similar. Walrus tusks (modified fangs) and elephant tusks (overgrown incisors) are typical analogous organs, since their functions are similar. In plants, barberry spines (modified leaves), white acacia spines (modified stipules) and rose hips (develop from bark cells) are similar.

• Rudiments.Vestigial(from lat. rudimentum- rudiment, primary basis) are organs that are formed during embryonic development, but later stop developing and remain in adult forms in an underdeveloped state. In other words, rudiments are organs that have lost their functions. Rudiments are the most valuable evidence of the historical development of the organic world and the common origin of living forms. For example, anteaters have rudimentary teeth, humans have ear muscles, skin muscles, the third eyelid, and snakes have limbs (Fig. 3.22).
• Atavisms. The appearance in individual organisms of any type of characteristics that existed in distant ancestors, but were lost during evolution, is called atavism(from lat. atavus- ancestor). In humans, atavisms are the tail, hair on the entire surface of the body, and multiple nipples (Fig. 3.23). Among thousands of one-toed horses, there are specimens with three-toed limbs. Atavisms do not carry any functions important for the species, but show the historical relationship between extinct and currently existing related forms.

Embryological proof stva. In the first half of the 19th century. Russian embryologist K.M. Baer (1792-1876) formulated the law of germinal similarity: the earlier stages of individual development are studied, the more similarities are found between different organisms.

For example, in the early stages of development, vertebrate embryos do not differ from each other. Only at the middle stages do features characteristic of fish and amphibians appear, and at later stages do features of the development of reptiles, birds and mammals appear (Fig. 3.24). This pattern in the development of embryos indicates the relationship and sequence of divergences in the evolution of these groups of animals.

The deep connection between the individual and the historical is expressed in biogenetic law, established in the second half of the 19th century. German scientists E. Haeckel (1834-1919) and F. Müller (1821-1897). According to this law, each individual in its individual development (ontogenesis) repeats the history of the development of its species, or ontogenesis is short

and rapid repetition of phylogeny. For example, in all vertebrates, a notochord is formed during ontogenesis, a feature that was characteristic of their distant ancestors. The tadpoles of tailless amphibians develop a tail, which is a repetition of the characteristics of their tailed ancestors.

Subsequently, amendments and additions were made to the biogenetic law. A special contribution to elucidating the connections between onto- and phylogeny was made by the Russian scientist A.N. Severtsov (1866-1936).

It's clear what kind of short term, How individual development, all stages of evolution cannot be repeated. Therefore, the repetition of the stages of the historical development of a species in embryonic development occurs in a compressed form, with the loss of many stages. At the same time, the embryos of organisms of one species are similar not to the adult forms of another species, but to their embryos. Thus, the gill slits in a one-month-old human embryo are similar to those in a fish embryo, but not in an adult fish. This means that during ontogenesis, mammals go through stages similar to fish embryos, and not to adult fish.

It should be noted that Charles Darwin drew attention to the phenomenon of repetition in ontogenesis of the structural features of ancestral forms.

All of the above information is of great importance for proving evolution and for elucidating related relationships between organisms.

Biogeographic evidence. Biogeography is the science of the patterns of modern settlement of animals and plants on Earth.

You already know from the course physical geography that modern geographical zones formed during the historical development of the Earth, as a result of the action of climatic and geological factors. You also know that they are often similar natural areas turn out to be inhabited by different organisms, and different zones are similar. Explanations for these facts can only be found from the standpoint of evolution. For example, the originality of the flora and fauna of Australia is explained by its isolation in the distant past, and therefore the development of the animal and plant world occurred in isolation from other continents. Consequently, biogeography contributes much evidence to the evolution of the organic world.

Currently, methods of biochemistry and molecular biology, genetics, immunology.

Thus, by studying the composition and sequence of nucleotides in nucleic acids and amino acids in proteins in different groups of organisms and by detecting similarities, one can judge their relationship.

Biochemistry has research methods that can be used to determine the “blood relationship” of organisms. When comparing blood proteins, the ability of organisms to produce antibodies in response to the introduction of foreign proteins into the blood is taken into account. These antibodies can be isolated from blood serum and determined at what dilution this serum will react with the serum of the comparison organism. This analysis showed that the closest relatives of humans are the great apes, and the most distant of them are lemurs.

The evolution of the organic world on Earth is confirmed by many facts from all areas of biology: paleontology (phylogenetic series, transitional forms), morphology (homology, analogy, rudiments, atavisms), embryology (law of embryonic similarity, biogenetic law), biogeography, etc.

1. What does paleontology study and what paleontological evidence of evolution do you know? 2. How do homologous organs differ from similar ones and what is their significance in proving evolution? 3. Which of the listed organs are homologous and which are similar: gills of fish, crayfish; sepals, petals, stamens, pistil, leaves; barberry spines, pea tendrils, grape tendrils? 4. What do rudiments and atavisms indicate? 5. What is the essence and significance of the law of germinal similarity? 6. Why are marsupials found predominantly in Australia? 7. What methods are currently used to prove the relationship between organisms of different species?

General biology: Tutorial for 11th grade 11 year old secondary school, for basic and increased levels. N.D. Lisov, L.V. Kamlyuk, N.A. Lemeza et al. Ed. N.D. Lisova.- Mn.: Belarus, 2002.- 279 p.

Contents of the textbook General Biology: Textbook for 11th grade:

Chapter 1. Species - a unit of existence of living organisms

• § 2. Population is a structural unit of a species. Population characteristics

Chapter 2. Relationships of species, populations with environment. Ecosystems

• § 6. Ecosystem. Connections of organisms in an ecosystem. Biogeocenosis, structure of biogeocenosis
• § 7. Movement of matter and energy in an ecosystem. Power circuits and networks
• § 9. The circulation of substances and the flow of energy in ecosystems. Productivity of biocenoses

Chapter 3. Formation of evolutionary views

• § 13. Prerequisites for the emergence of the evolutionary theory of Charles Darwin
• § 14. General characteristics of the evolutionary theory of Charles Darwin

Chapter 4. Modern representations about evolution

• § 18. Development of evolutionary theory in the post-Darwinian period. Synthetic theory of evolution
• § 19. Population is an elementary unit of evolution. Prerequisites for evolution

Chapter 5. Origin and development of life on Earth

• § 27. Development of ideas about the origin of life. Hypotheses about the origin of life on Earth
• § 32. The main stages of the evolution of flora and fauna
• § 33. The diversity of the modern organic world. Principles of taxonomy

Chapter 6. Origin and evolution of man