How to establish the relationship of modern and extinct animals. Amazing family connections in the animal world. Paleontological evidence of animal evolution
More than 20 years have passed since the cloning of the first warm-blooded animal - the famous sheep Dolly. Today, technologies for creating identical organisms are used all over the world - in laboratories and nurseries where animals are bred for experiments. Over the course of a couple of decades, thousands of cloned mice, rats, rabbits, frogs, goats, cows and even camels were born. Having mastered the cloning tool and adapted it for everyday research needs, biologists decided to use it to recreate extinct species. We present seven organisms that scientific teams are currently working on to resurrect.
Woolly Mammoth
Extinct approximately 10 thousand years ago
Scientists are serious and pragmatic people. Do not think that they choose candidates for cloning from among their favorites. No, the researchers are analyzing how the resurrected species could benefit the current ecosystem. If the animal contributes to its stabilization and improvement, he is given a chance to return from oblivion.
Take, for example, the woolly mammoth (Mammuthus primigenius) and its neighbors, who lived 2 million - 10 thousand years ago. With the extinction of these giants, as well as woolly rhinoceroses, ancient bison and roe deer, the richest flowering mammoth steppes, on which other large herbivores fed: wild horses, musk oxen, and moose, also disappeared. Now in the north of our country, where all these animals lived, there is bare tundra. The last ice age destroyed not only the megafauna, but also the flora.
It seems that the idea of resurrecting mammoths was in the air from the moment it was determined that they were extinct. But recently the idea began to come true. In 2008, a group of Russian geneticists deciphered the sequence of mitochondrial DNA (mitochondria are an essential component of every animal and plant cell, along with the cell nucleus, Golgi apparatus, ribosome, lysosome, etc.), isolated from the fossil remains of a woolly mammoth. And in 2011, an international team led by Webb Miller and Stefan Schuster from the University of Pennsylvania (USA) recovered 70% of the mammoth's DNA. In 2015, Harvard professor George Church successfully transplanted some mammoth genes into the DNA of an African elephant. Currently, a large collaboration of scientists from Russia, the USA, South Korea and Japan is working on cloning the woolly mammoth. There are no positive results yet, but observing the perseverance of the researchers, one can at least hope for success.
Even greater hope for the resurrection of the mammoth is given by the fact that in Yakutia for the last 20 years they have been preparing a home for this beast - restoring the plant diversity of the mammoth steppes. The project called “Pleistocene Park” was launched in 1997 by Russian ecologist, director of the North-Eastern Scientific Station of the Russian Academy of Sciences Sergei Zimov.
From time to time, researchers discuss the need for the return of another representative of the Pleistocene megafauna - the woolly rhinoceros (Coelodonta antiquitatis). But no one is seriously engaged in cloning it yet.
Passenger pigeon
The last individual died in 1914
The discoveries of paleontologists indicate that these birds from the pigeon family found mammoths: the oldest remains are at least 100 thousand years old. Passenger pigeons (Ectopistes migratorius) have survived a lot: climate change, megafauna extinction. They lived exclusively in the territory of modern North America, that is, they were its endemics. Scientists suggest that until the 17th century, until the colonization of North American lands began, the population of these birds amounted to billions of individuals.
The settlers, having tasted the tender meat of passenger pigeons, began to exterminate them en masse. Large-scale deforestation of the forests in which the birds nested, as well as the destruction of the pigeon’s main food, American chestnuts, also played a role in the extinction of the species. By the beginning of the 20th century, there were virtually no such birds left in nature, and in 1914 the last pigeon named Martha, who lived in the zoo of the American city of Cincinnati, died.
Now in California, an independent research organization called Revive and Restore, created to resurrect extinct species, is working on cloning the passenger pigeon. For the founder of the organization, evolutionary biologist and ecologist Ben Novak, this is a priority project (Revive and Restore simultaneously clones several species of exterminated animals): he promises to present the first individual to the world in 2025.
Stuffed passenger pigeons (Vanderbilt Museum, USA). Photo: wikipedia.org
Mauritian dodo, or dodo
Exterminated in the 1680s
The image of this bird, which lived exclusively on the island of Mauritius, is familiar to many from Lewis Carroll's fairy tale "Alice in Wonderland". The main character meets a creature named Dodo at the Tear Pool and is surprised by his abstruse speech, confusing and overloaded with terms. In John Tenniel's illustrations for the first edition of the book, Alice's new acquaintance is depicted as a bird with a heavy body, large paws, tiny wings and a powerful beak, widening in the middle, curved and pointed at the very tip. This is exactly how the Mauritian dodo (Raphus cucullatus) is depicted in the sketches of the Dutch colonialists who arrived in Mauritius at the end of the 16th century. Their illustrations and diary entries are the first documentary evidence of the existence of the dodo.
Like passenger pigeons, dodos aroused purely gastronomic interest among settlers, as evidenced by surviving entries in ship logs and diaries. “This bird is so large that we couldn’t eat it all at once; the remaining meat had to be salted,” sailor William van West Replacement either complained or rejoiced.
The dodos were indeed large: the height of some individuals reached a meter and their weight was 17 kilograms. These birds were exterminated quickly, because they were easy prey: they had no natural enemies and allowed people to get close. Domestic animals brought by sailors - dogs and pigs, which stirred up dodo nests and feasted on their eggs, also contributed to the disappearance. According to modern research, the last individuals of the Mauritian dodo died at the end of the 17th century.
At the beginning of the 2000s, British and American scientists, under the leadership of molecular biologist and geneticist, professor of evolutionary biology Beth Shapiro, began deciphering the dodo genome. The work is being carried out at the University of Oxford; dried dodo heads from the collection of the Oxford Museum of Natural History are used as biomaterial. So far, scientists have only partially restored the bird's DNA and began to compare its genes with the DNA of modern birds - potential relatives of the dodo. This is important, because a species can only be restored by introducing its genes into the egg of a living organism from a common family. There have been no sensational results yet.
Dodo skeleton and model based on modern research (Oxford University Natural History Museum, UK). Photo: wikipedia.org
Heather grouse
The last individual died in 1932
The heather grouse (Tympanuchus cupido cupido) was similar to today's grouse, but was smaller - about the size of a domestic chicken. This bird once lived throughout almost the entire territory of the modern United States. According to the notes left by the colonists, the meat of the heather grouse was extremely tasty, and the birds themselves were incredibly numerous: hundreds, or even thousands, of them were slaughtered every day. The carcasses were sold for almost nothing. However, it seems that the decisive role in the extermination of the species was played not by humans, but by the deadly avian disease histomonia, introduced by him along with chickens - necrosis of the liver and intestines, caused by the protozoan Histomonas meleagridis.
By the end of the 19th century, about two hundred individuals remained, and then only on the sparsely populated island of Martha's Vineyard (now part of the state of Massachusetts, USA). Trying to correct the situation and increase the population of heather grouse, the Americans created a nature reserve on this island, but their efforts were in vain: in 1932, the last individual died.
The main work on feathered cloning is carried out by scientists from Revive and Restore. For them, resurrecting the heather grouse is their second priority project after the passenger pigeon. So this bird also has a chance to return.
Great auk
The last representatives were destroyed in the 1850s
The only flightless bird from the auk family, which includes many modern sea birds: puffins, guillemots, little auks, auklets, etc. The great auk (Pinguinus impennis) lived along the northern waters of the Atlantic Ocean (on the coast of the North-East USA, Canada, Greenland, Iceland , Faroe Islands, Norway). With its structure, sluggishness, and black and white coloring it resembled penguins. Scientists have long argued about their relationship. However, in 2002, when the mitochondrial DNA of the great auk was deciphered, it became obvious that this bird came from a completely different family.
During the era of great geographical discoveries, the down and eggs of the great auk were in great demand among Europeans. By the 19th century, the bird population had declined greatly, and stuffed animals had increased significantly in price among collectors, which provoked a new round of violence against auks. Their natural enemies: killer whales and polar bears also helped people exterminate birds. There is a version that the last individuals living near the Canadian island of Newfoundland were found and destroyed by poachers in the 1850s.
Several scientific groups from the USA and Europe are trying to resurrect this animal with the support of the same organization Revive and Restore.
Great auks (John James Audubon's drawing from Birds of America). Photo: wikipedia.org
Bucardo
The species was officially declared extinct in 2000.
Bucardo (Capra pyrenaica pyrenaica) is an extinct subspecies of the Pyrenean ibex. These animals lived in the north of the Iberian Peninsula (Spain). Several factors probably contributed to their disappearance: poaching, environmental degradation, and competition for food with domesticated ungulates.
The last individual, named Celia, died in 2000 in a Spanish national reserve located in the province of Huesca. However, scientists from the Research Center for Agriculture and Technology of Aragon saved Celia's genetic material and in 2009 tried to create a clone of her. The chances of success were great, because geneticists did not have to spend a long time and painfully identifying their closest relatives - females of two other subspecies of the Iberian goat were taken as surrogate mothers.
Spanish biologists created 439 embryos and implanted them into the wombs of 57 goats. Pregnancy occurred in seven females, but only one was able to bear a calf. Unfortunately, the baby goat died minutes after birth. After this, work to resurrect the bucardo was suspended indefinitely.
Thylacine, or marsupial wolf
The last individual died in 1936
Another likely candidate for cloning is the marsupial wolf, also known as the thylacine (Thylacinus cynocephalus), which lived primarily on the island of Tasmania, a couple of hundred kilometers from the Australian continent. The Australian aborigines enthusiastically hunted these animals, so when European ships reached the shores of the island, there were very few marsupial wolves. The first records of this creature date back to 1808. Their author, naturalist George Harris, classified the thylacine as a member of the opossum family. “The only thing that distinguishes it from opossums is its head, which looks like a dog’s,” the researcher noted in his diary. Later, scientists revised Harris's version and recorded the thylacine in a separate taxonomic group - the family of marsupial wolves.
Wolves finally disappeared in the 20th century - by the 1940s, not a single individual remained alive. In 1999, Australian scientists first tried to clone an animal - without success. The second project to resurrect the thylacine was launched in 2008 by biologists from the University of Melbourne: they inserted fragments of marsupial wolf DNA into a mouse embryo. That's all for now, but work continues. And importantly, it is supported, including financially, by the Australian government.
P.S. Of course, I would also like to recreate a cave lion, a cave bear, a big-horned deer, a saber-toothed cat, a moa bird, a quagga, a blue butterfly... But, as you can see, it’s not that easy. Scientists face many challenges: from DNA restoration and finding the ideal surrogate mother to reviving the habitat for future clones.
Any species of animal appears, spreads, conquering new territories and habitats, and lives for some time in relatively constant conditions of existence. When these conditions change, it can adapt to them, change and give rise to a new species (or new species), or it may disappear. The totality of such processes constitutes the evolution of the organic world, the historical development of organisms - phylogeny.
This essay is devoted to the topic “Development of the animal world.” In order to expand on the topic, the following questions are covered:
1. The reasons for the evolution of the animal world based on the ideas of Charles Darwin
2. Complication of the structure of animals. Diversity of species as a result of evolution.
3. Evidence of animal evolution.
The reasons for the different levels of organization of animals, the differences between existing species and extinct ones, and the manifestations of atavisms have long been of interest to scientists and church ministers.
The famous English scientist Charles Darwin (1809-1882) explained these phenomena most fully in his work “The Origin of Species”.
According to Darwin's teaching, the diversity of species was not created by God, but was formed due to constantly occurring hereditary changes and natural selection. In the process of survival of the fittest individuals, Darwin noted the presence of a struggle for existence, the result of which is the extinction of unadapted organisms and the reproduction of the most fit.
Heredity is the ability of organisms to transmit to their descendants their specific and individual characteristics or properties. Thus, a certain species of animal produces offspring that are similar to their parents. Some individual characteristics of animals can also be hereditary, for example, coat color and milk fat content in mammals.
Variability is the ability of organisms to exist in different forms, responding to environmental influences. Variability is manifested in the individual characteristics of each organism. In nature, there are no two absolutely identical animals. The born cubs differ from each of their parents in coloring, height, behavior and other characteristics. Differences in animals, as C. Darwin noted, depend on the following reasons: on the quantity and quality of food consumed, on fluctuations in temperature and humidity, on the heredity of the organism itself. Charles Darwin identified two main forms of variability that influence the evolution of the animal world - definite, non-hereditary, and indefinite, or hereditary.
By certain variability, Charles Darwin understood the occurrence of identical changes in a number of related animals under the influence of identical environmental conditions. Thus, the thick fur of Transbaikal squirrels changed to sparse fur during their acclimatization in the coniferous forests of the Caucasus. Keeping rabbits in low temperatures results in thicker fur. Lack of food leads to stunted growth of wild and domestic animals. Consequently, a certain variability is a direct adaptation of animals to changed environmental conditions. Such variability is not passed on to descendants.
By uncertain hereditary variability, Charles Darwin understood the occurrence of various changes in a number of related animals under the influence of the same (similar) conditions. Indefinite variability, according to Charles Darwin, is hereditary and individual, since it arises by chance in one individual of the species and is inherited. An example of individual hereditary variability is the appearance of sheep with short legs, the absence of pigment in the feathers of birds or in the fur of mammals.
Charles Darwin considered one of the reasons for the evolution of the animal world to be the struggle for existence, which arises due to the intensive reproduction of organisms. A parent pair of any animal species produces numerous offspring. Out of the number of offspring born, only a few will survive to adulthood. Many will be eaten or die almost immediately after birth. Those who remain will begin to compete with each other for food, better habitats, and shelter from enemies. The descendants of those parents who are most adapted to the given living conditions will survive. Thus, the struggle for existence leads to natural selection - the survival of the fittest.
In nature, individuals of the same species differ from each other in many ways. Some of them may be useful, and, as Darwin noted, “individuals having even a slight advantage over the rest will have the best opportunity of surviving and leaving the same offspring.” The process occurring in nature that preserves organisms most adapted to environmental conditions and destroys those that are not adapted is called natural selection. According to Charles Darwin, natural selection is the main, leading cause of the evolution of the animal world.
2. INCREASING COMPLEXITY OF THE STRUCTURE OF ANIMALS. DIVERSITY OF SPECIES AS A RESULT OF EVOLUTION
Thus, birds have a streamlined body, a lightweight skeleton, which facilitates rapid movement in the air with the help of wings. Aquatic animals, such as whales, dolphins, and fur seals, have a torpedo-shaped body, adapted for rapid movement in the aquatic environment. Land animals have well-developed limbs for moving quickly on the ground. Underground animals, such as moles and mole voles, lead a burrowing lifestyle. Small animals are covered with short thick hair, which prevents particles of earth from getting on the skin, and have powerful forelimbs adapted for digging underground passages.
The existing vertebrates - fish, amphibians, reptiles, birds and mammals, characterized by a progressively more complex organization, arose on the basis of hereditary variability, the struggle for existence and natural selection during a long historical development.
The fauna around us is rich not only in a large number of individuals, but also in the diversity of species. Each individual of any species is adapted to life in the conditions of its habitat. If a large group of representatives of any species finds themselves in different conditions or they switch to feeding on different foods, this may lead to the appearance of new characteristics or adaptations. If these new adaptations, under different conditions, turn out to be useful for the migrated animals, then, thanks to natural selection, the newly acquired characteristics will be preserved in their ranks and will be passed on from generation to generation. Thus, in the process of evolution, several new ones can be formed from one species. The process of divergence of characters in related organisms was called divergence by Charles Darwin.
An example of divergence is the small birds finches on the Galapagos archipelago. Darwinian species of finches differ in the shape and size of their beaks (Fig. 194). Darwin found that finches, which had a small sharp beak, fed on larvae and adult insects. Finches with a powerful massive beak fed on tree fruits. Gradual transitions in the variability of these beaks in finches were also noted. Thus, in the process of evolution, due to the divergence of characters determined by the direction of natural selection, speciation occurred. The emergence of a new species, as Darwin noted, is preceded by the formation of intermediate forms - varieties. This evolutionary process ends with the formation of new species.
Through divergence and the directed action of natural selection, a variety of species is formed in nature.
2. Evidence of animal evolution
Paleontological evidence
Paleontology is the science of ancient organisms of past geological eras. She studies the fossil remains of those who lived on Earth tens and hundreds of millions of years ago. Fossil remains are fossilized shells of mollusks, teeth and scales of fish, egg shells, skeletons and other solid parts of organisms, prints and traces of their vital activity, preserved in soft silt, clay, sandstone (Fig.). These rocks once hardened and were preserved in a petrified state in various layers of the Earth. Using fossilized finds, paleontologists recreate the animal world of past eras. The study of paleontological samples that have reached us from the deepest layers of the Earth convincingly shows that the animal world of ancient times was significantly different from the modern one. The fossilized remains of animals located in shallower layers, on the contrary, bear structural features similar to modern animals. By comparing animals that lived in different eras, it was established that the animal world was constantly changing over time. The relationship of modern animals from various systematic groups with extinct ones is established by the findings of so-called intermediate, or transitional, forms. For example, it became known that birds descended from reptiles, which are their closest relatives, but at the same time differ significantly from them.
In Europe, an animal print was found with characteristics that are characteristic of both reptiles and birds. The scientific name of the reconstructed animal is Archeopteryx. Features characteristic of reptiles are a heavy skeleton, powerful teeth (they are absent in modern birds), and a long tail. Features characteristic of birds are wings covered with feathers. Using fossilized remains, scientists have fairly fully restored many transitional forms from distant ancestors to more modern animals.
Complete reconstruction of the appearance of organisms, transitional from distant ancestors to modern animals, serves as one of the paleontological evidence of the true picture of the evolution of living organisms on Earth.
Many animals that lived before have no analogues in the modern animal world - they are extinct. Today paleontologists are trying to unravel the reasons why they disappeared. The largest extinct animals were dinosaurs.
Embryological evidence
A comparison of the characteristics of embryonic development of representatives of various groups of vertebrates, for example fish, newt, turtle, bird, rabbit, pig and human, showed that all embryos in the early stages of development are very similar to each other. The subsequent development of embryos retains similarity only in closely related groups, for example, in a rabbit, a dog, a person, who have a common structural plan in adulthood. Further development leads to the disappearance of similarities between the embryos.
Each representative of a species develops only its own characteristic structural features. At the end of embryonic development, signs characteristic of a particular animal species appear.
Studying the successive stages of development of each embryo makes it possible to reconstruct the appearance of a distant ancestor. For example, the early stages of development of mammalian embryos are similar to fish embryos: they have gill slits. Apparently, the distant ancestors of animals were fish. In the next stage of development, the mammalian embryo is similar to the newt embryo. Consequently, among their ancestors there were also amphibians (Fig. 1).
Thus, the study of the embryonic development of various groups of vertebrate animals shows the relationship of the organisms being compared, clarifies the path of their historical development and serves as evidence in favor of the existence of the evolution of living organisms.
Comparative anatomical evidence
Comparing vertebrates of different classes, it was found that they all have a single structure plan. The bodies of amphibians, reptiles, birds and mammals consist of a head, torso, forelimbs and hindlimbs. They were characterized by similar skin eternities and were quadrupeds. Organs that have lost their function as a result of their long-term non-use are called vestigial. The presence of vestigial organs in animals is irrefutable evidence of the existence of evolution.
STAGE I
STAGE II
Fish Salamander Turtle Rat Human
Rice. 1 Similarity of vertebrate embryos
Rice. 2. Vestigial organs of animals
If the process of embryonic development is disrupted for any reason, certain features of the animal's body structure may differ sharply from other individuals of the same species. However, their presence and similarity with other representatives of this class of animals indicates the related origin and evolution of each species. Cases of manifestation of ancestral characteristics in modern individuals are called atavism. Examples of it include: three-toedness in modern horses; additional pairs of mammary glands in those who always had one pair; the presence of hair all over the body.
Comparative anatomical series showing the directions of historical development in species belonging to the same class, family, or genus are considered significant evidence of evolution. For example, the methods of reproduction in oviparous, marsupials and placentals show the directions of development of reproductive systems; limbs of equids show the emergence of a one-toed foot in connection with changed living conditions, etc.
CONCLUSION
Thus, we have examined the basic principles of the development of the animal world based on the theory of Charles Darwin, according to which the diversity of species was formed due to constantly occurring hereditary changes and natural selection. One of the reasons for the evolution of the animal world according to Darwin is the struggle for existence, as a result of which the extinction of unadapted organisms occurs and the reproduction of the most adapted.
The amazing diversity of forms and body structures of animals is the result of natural selection, as a result of which there is a constant accumulation in descendants of characteristics that are useful to them in given conditions of existence, and this process, in turn, leads to a complication of the structure of animals. Moreover, in the process of evolution, several new ones can be formed from one species. The process of divergence of characters in related organisms was called divergence by Charles Darwin.
The diversity of extinct reptiles serves as an example of their divergence based on different living conditions.
Animals of the same species living over a large area are usually heterogeneous. Their study shows the divergence of characters in individuals and the beginning of the formation of new systematic groups.
Literature
Akimov O. S. Natural science. M.: UNITY-DANA, 2001.
Gorelov A. A. Concepts of modern natural science. - M.: Center, 2002.
Gorokhov V.G. Concepts of modern natural science. - M.: INFRA-M, 2000.
Dubnischeva T.Ya. and others. Modern natural science. - M.: Marketing, 2000.
Basic concepts of modern natural science. - M.: Aspect - Pr, 2001
Petrosova R.A. Natural science and basic ecology. - M.: Academy, 2000.
Tchaikovsky Yu.V. Elements of evolutionary diagnostics. - M., 1999.
The animal world never ceases to amaze with its diversity, but, as scientists have found out, there are family ties between seemingly incompatible species that go back to ancient times. Here are some examples...
Cetaceans (dolphins and whales) are among the most beloved and respected animals on earth. Despite the fact that their element is the vastness of the seas and oceans, good-natured giants whales and mischievous clever dolphins belong to the class of mammals and have nothing to do with fish.
Surprisingly, the closest relatives of dolphins should be looked for on earth, or rather in Africa. Here, south of the Sahara Desert, live animals that, according to researchers, have common ancestors with dolphins.
Ambulocetus. wiki/Nobu Tamura
These ancient creatures, who lived more than fifty million years ago, split into two lineages: cetaceans and anthracotheriums. It’s hard to believe, but in those days, whales and dolphins walked on land and led a semi-aquatic lifestyle, like modern crocodiles and otters. In the photo above, a schematic representation of Ambulocetus, the ancestor of whales, whose name translates from Latin as “walking whale.”
Anthracotherium. wiki/Dmitry Bogdanov
The second photo shows Anthracotherium, an extinct representative of the artiodactyl order, which left behind only one descendant - the hippopotamus. Meanwhile, the cetaceans became more and more accustomed to life in the water, until they completely forgot about their land origin.
In the meantime, scientists are arguing whether it is worth including whales and dolphins in the artiodactyl order, which, in addition to hippopotamuses, includes deer, cows, pigs, etc. Agree, such a neighborhood would look strange, to say the least.
People have an ambiguous relationship with bears. On the one hand, every evening we put our children to bed hugging a teddy bear, but on the other hand, we are horrified by the thought that we might find ourselves alone with a living one.
He is menacing and handsome at the same time, and it would seem that his relatives should be the same. But this is not entirely true: Mother Nature does not always follow a simple and understandable path. And as confirmation of this is the fact that scientists call seals, sea lions, etc., the closest relatives of bears.
Pinnipeds have always occupied a special position on the evolutionary tree. However, genetic studies clearly prove that the closest relatives of pinnipeds are bears and ferrets. Skeptics will say: “They have nothing in common; you don’t need to be a biologist to see that.” But it seems so only to those who do not bother to take a closer look at these animals.
At least compare their paws. The seal's flipper is flatter, and the bear's claws are longer. But both have five non-retractable claws on each paw, the same bone structure, and both are plantigrade, meaning when they move, the heel and toes touch the ground at the same time.
Puyila. wiki/Nobu Tamura
Fossil finds discovered in a meteorite crater on the Canadian island of Devon suggest that pinnipeds descended from Puyila (lat. Puijila darwini) is a predatory mammal that lived more than twenty million years ago. Puyil could move easily on land on all fours, like bears, but had webbed limbs that allowed them to hunt in water.
Calm and reliable representatives of the equine family (horses, donkeys, etc.) became man’s faithful assistants several thousand years ago and since then have faithfully served him in various spheres of his life.
It is easy to assume that donkeys and horses must have close family ties with those with whom they share the difficult task of serving man. But in fact, you are unlikely to see the donkey's closest relatives on an ordinary farm. To meet him, you need to go either to the African continent or to one of the Asian countries - this is where the five remaining closest relatives of the equine family live.
Rhinoceroses belong to the order of odd-toed ungulates, which, in addition to them, includes two more families - equines and tapirs. Their appearance resembles a lightweight copy of a rhinoceros, deprived of its heavy armor and formidable weapon - a giant horn.
Heracotherium. wiki/Heinrich Harder
If you look at the recent past of these animals, you can see how much they have in common. For example, rhinoceroses walk, leaning on three large toes (their number is odd, hence the name - odd-toed ungulates), and horses once did the same. Over time, their fingers transformed into one large finger covered with a dense nail plate, turning into what is today called a hoof.
The most ancient ancestors of the modern horse were Heracotherium - four-toed horse-like animals that lived in the Eocene era (55-45 million years ago). Then the number of toes began to decrease - Mesohippus and Merikhippus had two, and then Pliohippus appeared - the first one-toed horse that lived in the Pliocene (5-2 million years ago).
Another unexpected relationship is that of mongooses. In appearance, hyenas resemble dogs beaten by life, but you should not rush to the pet store for a baby hyena.
This aggressive predator has nothing to do either in character or genetically with the dogs we love so much. The order Carnivora is divided into two parts: the suborder Felidae (lat. Feliformia) and canids (lat. Caniformia). Hyenas belong specifically to the cat branch of predatory mammals, this is confirmed by the structure of their skull and teeth.
The closest relatives of the hyena, also included in the suborder Catiformes, are representatives of the mongoose family (lat. Herpestidae), which also includes and . Despite their reputation as cowardly scavengers, hyenas have a courageous character and are able to defend their prey against stronger competitors, such as and, and carrion makes up only five percent of the hyena's diet. They kill the remaining 95 themselves.
Tunicates are chordate animals that inhabit the seabed and lead a monotonous lifestyle, attached to the bottom and filtering water saturated with plankton. What creatures can be called their closest relatives - sponges, corals, worms?
Surprisingly, scientists consider tunicates to be the ancestors of all vertebrates, including humans. In other words, our very distant ancestor could look like the one shown in the picture.
Paleontological evidence
1. Let's write about fossil remains.
Fossil remains - fossilized shells of mollusks, teeth and scales of fish, egg shells, skeletons of animals, prints and traces of their vital activity, preserved in soft silt, clay, sandstone. Using fossil finds, scientists reconstruct the animal world of past eras.
2. Let’s find out the relationship between modern and extinct animals.
The relationship of modern and extinct animals is established from the findings of intermediate forms. It turned out that the fossilized remains of animals bear structural features that are similar to modern animals, but at the same time differ from them.
3. Let's name the signs of Archeopteryx, bringing it closer together
With reptiles: heavy skeleton, powerful teeth, long tail.
With birds: wings covered with feathers.
4. Let's name the reasons for the extinction of dinosaurs.
Cooling climate. Other versions: the fall of an asteroid (comet), a solar flare, a pandemic, volcanic activity, changes in the composition of the atmosphere, poor diet, low genetic diversity, changes in gravitational attraction and others.
Embryological evidence
1. Let's write an answer about the similarity of embryos.
The similarity of the embryos of all vertebrates in the early stages of development indicates the unity of origin of living organisms and is evidence of evolution.
2. Let us denote the time of appearance of signs.
In the later stages of embryo development.
3. Let's write an answer about the distant ancestors of animals.
Based on the similarity of their embryos in the early stages. The initial stages of development of mammalian embryos are similar to fish embryos; at the next stage, the embryo resembles a newt embryo. Consequently, the ancestors of mammals included amphibians and fish.
Comparative anatomical evidence
1. Let's write an answer about a single building plan.
The general plan of the structure of vertebrate organisms indicates their close relationship and allows us to assert that modern chordates originate from primitive ancestral organisms that existed in the distant past.
2. Let's finish the statements.
Organs that are similar in general structural plan, but have different shapes, sizes and are differently adapted to perform various functions are called homologous.
For example, the forelimbs of vertebrates.
Organs that have lost their function as a result of prolonged disuse are called vestigial.
For example, the wing of a kiwi, the hind limbs of a python, the pelvic bones of a whale.
Atavism is the appearance in a given individual of characteristics characteristic of distant ancestors, but absent in nearby ones.
For example, modern horses have three toes, additional pairs of mammary glands, and the presence of hair all over the body.
3. Let us describe the change in communication between organisms.
As evolution progressed, the connection between the mother and offspring became closer. Oviparous animals lay eggs and care for them, but the baby develops outside the mother's body. In marsupials, the baby finally develops in a special “bag”. Placentals bear offspring inside the mother's body, the baby develops in the uterus. That is, the connection between the mother and the “children’s” organism became stronger, which ensured greater survival of the offspring.