How did the first animal appear on earth? Where did it come from? The very first living creature on earth The first animals on land.

In order to answer this far from simple question, it is necessary to analyze a certain amount of theory. I should also note that there is simply no single answer to this question, so I will try to consider the most popular hypotheses.

Who are the animals

As I said above, in order to improve the quality of perception of information, it is necessary to study a certain amount of theoretical information, namely the definitions of terms. An animal is a special kind of organism, which, in comparison with others, is more independent and independent. The most developed animal on planet Earth is, oddly enough, man. Man is a higher being who has absolute independence from other individuals and is guided not only by his natural instincts, but also by his own personal opinion and thinking.

How did the first animal appear and where did it come from

After learning a certain amount of theory, I can proceed directly to the answer to the question asked.

1. The first and main hypothesis is that the animal appeared as a result of mutations of bacteria, which later turned into animals familiar to us. Such a theory cannot be considered unambiguously correct, because a person does not have weighty facts in favor of this theory.
2. Also at the moment, the hypothesis of divine origin is popular. This theory cannot be confirmed or refuted in any way, because there is no evidence and cannot be.
3. There is also a theory of alien entry of some species of animals, which later multiplied and turned into animals familiar to us. Such a hypothesis has a place to be, because there are multiple traces of meteorites on the planet.

It is simply impossible to say which animal was the first, because people do not have any data on this matter.

In conclusion, I can say that humanity has not yet confirmed a single theory, so you can make any of your hypotheses based on basic knowledge, which will also have its own probability of existence.

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. Modern thinking is that these early amniotes still spent time in the water and came ashore, mainly to lay their eggs and not 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) in time Triassic period.

Trinaxodon

This evolutionary line provides an excellent series of transitional fossils. Development key feature mammals, the presence of a single bone in the lower jaw (compared to several in reptiles) can be traced back to 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 line include the development various kinds teeth (a feature known as heterodontia), the formation of a secondary palate, and an increase in dentary bone in the mandible. 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 mass extinction began to occupy free ecological niches.

However, at the end of the Permian period, it was dinosaurs, not reptilian 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. It had serious consequences when moving, as it allowed for more energy-saving movements.

Triceratops

Dinosaurs, or "terrible lizards", are divided into two groups, based on the structure hip joint: lizard and ornithischian. 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 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 family tree amniotic. 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 were already diverse group 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, it was thought that placental mammals (the group to which most living mammals belong) had 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 exposures. environment.

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, its for a long time considered a transitional form between birds and reptiles, making this animal one of the most important fossils ever discovered. Until recently, it was the earliest known bird. Recently, scientists have realized that Archeopteryx bears a closer resemblance to the maniraptors, a group of dinosaurs that includes the infamous velociraptors from Park jurassic than with 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.

A closer look at the early history of birds is good example 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 them characteristic features were well suited to this habitat: gripping hands, rotating shoulder joints, and stereoscopic vision. They also had relatively big size brain and claws on the fingers.

The earliest known fossils of most modern orders of mammals appear 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) have become 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 carefully studied in last 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 in the lowlands and transported great amount breeds. 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 plunged under the water again. 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 global changes caused by human activity. However, this term can be misleading; modern people had already been 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 first animal on Earth was Dickinsonia - a kind of soft symmetrical cake, resembling either a feather or a palm branch.

The first animal on earth

Dickinsonia are famous creatures. They lived about 560 million years ago. But were they animals? With this scientific world couldn't decide. Some considered the “cakes” to be plants, others to be mushrooms, others to be lichens, and some did not “hold” Dickinsonia as independent creatures at all, but believed that these were colonies of bacteria.

Individual representatives of the "mystery of nature" reached almost one and a half meters in diameter. But there were also small ones - a few millimeters.

The remains of two Dickinsonias were taken from a cliff located in Pomorie. The study showed that the fossils preserved organic matter. Scientists have determined their composition. And found a high concentration of cholesterol. It meant only one thing: Dickinsonia were animals. After all, only representatives of the animal world - cholesterol - produce it.

The current discovery of paleontologists indicates that the first animals appeared long before the so-called Cambrian Explosion, which happened about 540 million years ago - then the living creatures suddenly suddenly bred. Dickinsonia "wound up" much earlier - at least 20 million years.

Dickinsonia led what is called sedentary image life. But their descendants soon moved on, growing legs. And this happened, as it turned out, also many millions of years earlier than it was commonly believed.

1. Jellyfish

2. Nautilus

3. Horseshoe crabs

It was not difficult for them to survive all the known global catastrophes, practically without changing outwardly. Horseshoe crabs can rightly be called animals " blue blood". Their blood, unlike ours, has a blue color, because it is saturated with copper, and not with iron, like human.
Horseshoe crab blood has amazing properties- when it reacts with microbes, clots are formed. It is in this way that horseshoe crabs make a barrier against microbes. A reagent is made from the blood of horseshoe crabs and medicines are checked for purity with its help.

4. Neopilins

5. Latimeria

6 Sharks

For example, shark teeth grow throughout their lives, most big sharks can reach 18 meters in length. Sharks have a wonderful sense of smell - they smell blood at a distance of hundreds of meters. Sharks practically do not feel pain, because their body produces a kind of "opium", which dulls pain.

Sharks are amazingly adaptable. For example, if there is not enough oxygen, they can “turn off” part of the brain and consume less energy. Sharks can also regulate the salinity of the water by producing special means. The vision of a shark is several times better than that of cats. In dirty water, they see up to 15 meters away.

7. Cockroaches

Cockroaches can live for some time without a head - because they breathe with the cells of the body. They are excellent runners. Some cockroaches run about 75 cm in a second. This is a very good result for their height. And their incredible endurance is evidenced by the fact that they withstand radiation radiation almost 13 times more than a person.

Cockroaches can live without water for about a month, without water - a week. Their female retains the male's seed for some time and can fertilize herself.

8. Crocodiles

Crocodiles are amazing animals. They don't seem to do anything for nothing. To facilitate the digestion of food, crocodiles swallow stones. It also helps them dive deeper.

In the blood of a crocodile there is a natural antibiotic that helps them not to get sick. Their average life expectancy is 50 years, but some individuals can live up to 100 years. Crocodiles are not trainable, and they can be considered the most dangerous animals on the planet.

9. Shields

10 Turtles

If the temperature in the nest where the female laid her eggs is high, females will be born, if it is low, only males will be born.

11. Hatteria

Tuatara is similar to an iguana or lizard. But this is just a resemblance. Tuataria established separate detachment- beakheads. This animal has a "third eye" on the back of its head. Hatterias have slowed down metabolic processes, so they grow very slowly, but they easily live up to 100 years.

12. Spiders

The web could not be made artificially in any laboratory. And those spiders that were sent into space spun a three-dimensional web.
It is known that some spiders can live up to 30 years. The biggest famous spider has a length of almost 30 cm, and the smallest - half a millimeter.

13. Ants

Ants are very smart, strong and organized animals. We can say that they have their own civilization. They have order in everything - they are divided into three castes, each of which is engaged in its own business.

Ants are very good at adapting to circumstances. Their population is the largest on Earth. To imagine how many there are, imagine that there are about a million ants per inhabitant of the planet. Ants are also long-lived. Sometimes queens can live up to 20 years! And they are amazingly smart - ants can train their fellows to find food.

14. Platypuses

Platypuses are excellent swimmers, they easily get their own food from the river bottom with the help of their beak. Platypuses spend almost 10 hours a day underwater.
Platypuses failed to breed in captivity, and in wild nature today there are quite a few of them left. Therefore, animals are listed in the International Red Book.

15. Echidna

I wonder if a person can live on Earth for so long?