The first animals on land were protozoa. The first land animals. Further development of early mammals

Humanity owes the emergence of natural diversity on Earth to billions of years of revolution. Modern geologists and paleontologists have discovered turning points in the development of life on our planet.

1. The oldest people - Omo

Humans can now trace their lineage back hundreds of thousands of years. Two skulls, named Omo 1 and Omo 2, which were discovered in Ethiopia in 1967, are 195,000 years old, making them the earliest anatomically modern humans discovered so far. Scientists now think that Homo sapiens began to evolve 200,000 years ago.

However, this is still a matter of controversy, as evidence of cultural development - found musical instruments, needles and jewelry - dates back only 50,000 years. Complex compound tools such as harpoons also appeared around this time. Therefore, no one can answer the simple question: if modern humans appeared 200,000 years ago, then why did it take them as much as 150,000 years to develop anything resembling a culture.

2. The most ancient bird - protoavis

Today, everyone knows that birds evolved from dinosaurs, and also that many dinosaurs were actually covered in feathers. As a result, the question "which bird is the most ancient" should essentially be reformulated into "at what point can dinosaurs be considered birds."

For a long time, paleontologists considered the Archeopteryx to be the most ancient birds, but today an even more ancient candidate for the title of the first bird has appeared. Protoavis lived about 220 million years ago, 80 million years earlier than any of its competitors. The fossil was found in Texas by paleontologist Sankar Chatterjee, who claims that Protoavis is actually closer to modern birds than Archeopteryx.

3. The first types of creatures that began to walk on earth - Tiktaalik and pneumodesmus

Tiktaalik, a duck-billed creature that lived in the Devonian period, was a cross between a fish, a frog and an alligator. It is believed that it first got out of the water on land 375 million years ago. Discovered in Canada in 2004, this species is considered an important transitional link between aquatic vertebrates and the first land animals. Tiktaalik can also boast of ribs that are able to support its body out of water, a light, mobile neck and eyes on the top of the head, like a crocodile. The centipede pneumodesmus lived about 428 million years ago. The 1 centimeter-sized creature was actually the first creature to live permanently on earth and breathe air.

4. The oldest reptile - Gilon

Reptiles were the first vertebrates that could live on earth. The lizard-like creature, the Gilon, which is only 20 centimeters long, is believed by scientists to be the oldest reptile. Hylonomas, which appear to have been insectivorous, arose about 310 million years ago. The surviving fossil of this creature was discovered in 1860 inside a tree trunk in Nova Scotia.

5. The oldest creature that can fly - rhinognath

Flying as a primary means of locomotion requires a complex body structure (low body weight but strong skeleton) as well as powerful wing muscles. The first creature that was able to fly is actually the oldest known insect. Rhyniognatha hirsti is a tiny insect that lived about 400 million years ago. The first evidence of the existence of this insect was discovered in 1928 in the Devonian rocks.

6. The first flowering plant - potomacapnos and amborella

People tend to associate plants with flowers, but flowers are actually relatively recent. Before flowers appeared, plants reproduced with spores for hundreds of millions of years. In fact, scientists don't even know why flowers came into being, as they are very delicate and whimsical, and also require a huge amount of energy, which theoretically could be put to a much more rational use.

These incomprehensible circumstances led Darwin to describe the growth of flowers as a "terrible secret." The oldest known fossil flowering plants date back to the Cretaceous, between 115 and 125 million years ago. Some of the oldest flowers are potomacapnos, which surprisingly resembles a modern poppy, as well as amborella, which was found on the island of New Caledonia. Everything points to the fact that flowers did not develop slowly, but suddenly arose in fact in their modern form.

7. The most ancient mammal - Hadrocodium

The oldest known mammal resembled a small mouse or a modern shrew. The length of the hadrocodium, the remains of which were found in China in 2001, was about 3.5 centimeters, and the animal weighed only 2 grams. Most likely, he led a lifestyle similar to the modern shrew, since his teeth were special fangs for grinding insects. The Hadrocodium lived about 195 million years ago, long before some of the most famous dinosaurs, including Stegosaurus, Diplodocus, and Tyrannosaurus Rex.

8. The first tree is vattieza

Trees have played (and still play) a crucial role in shaping the Earth's atmosphere. Without them, carbon dioxide would not turn into oxygen, and the planet would soon become lifeless. The first forests dramatically changed the Earth's ecosystem. Thus, the appearance of trees can be considered one of the most important evolutionary breakthroughs in history.

Currently, the oldest known tree is a 397-million-year-old species that has been named vattieza. The leaves of this fern-like plant resembled a palm, and the tree itself reached a height of 10 meters. Wattiesa arose 140 million years before the dinosaurs. The plant reproduced by spores similar to modern ferns and mushrooms.

9. The oldest dinosaur - nyasasaurus

Dinosaurs began to reign on Earth after the Permian mass extinction, which occurred about 250 million years ago and destroyed about 90 percent of all species on the planet, including 95 percent of marine life, and most of the planet's trees. After that, dinosaurs appeared in the Triassic.

The oldest dinosaur known to date is Nyasasaurus, whose bones were discovered in Tanzania in 1930. Until now, scientists have no idea whether he was a predator or herbivore, and he also walked on two legs or four. The height of the nyasasaurus was only 1 meter, and the weight was 18-60 kg.

10 Oldest Life Form

What is the oldest form of life known to science? This is a rather difficult question, since often the fossils are so ancient that their age is difficult to accurately determine. For example, rocks discovered near the Pilbara region in Australia contained microbes nearly 3.5 billion years old. However, some scientists believe that such Precambrian organ-walled microfossils are actually a strange form of minerals that arose under special hydrothermal conditions. In other words, they are not alive.

Instruction

According to abiogenic hypotheses about the origin of life on Earth, the first step towards the origin of living things was the synthesis of organic biopolymers. Through chemical evolution, biopolymers passed to the first living organisms, which further developed according to the principles of biological evolution. In the course of this historical development and complication, many forms of life have appeared.

The history of the Earth is divided into long time intervals - eras: Katarchean, Archean, Proterozoic, Paleozoic, Mesozoic and Cenozoic. Paleontology, the science of ancient organisms of past geological eras, helps scientists to obtain data on the development of life on Earth. Fossil remains - mollusc shells, fish teeth and scales, egg shells, skeletons and other hard parts - are used to study organisms that lived tens, hundreds of millions of years ago.

It is believed that in the Archean (“earliest”) era bacteria dominated the planet, the result of their vital activity was marble, graphite, limestone, etc. Archean deposits also found the remains of cyanobacteria capable of oxygen-free photosynthesis. At the end of the most ancient era, living organisms, according to assumptions, were divided into prokaryotes and eukaryotes.

In the Proterozoic - the era of early life - living organisms continued to become more complex, and their methods of nutrition and reproduction improved. All life was concentrated in the aquatic environment and along the banks of water bodies. Among animals, a wide variety of coelenterates and sponges appeared. Toward the end of the Proterozoic era, all types of invertebrates and the first chordates arose. Remains of worms, mollusks and arthropods are also found in the sediments. The only descendant of the early life era that has survived to this day is considered the lancelet.

The Paleozoic is the era of "ancient life". It distinguishes the Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian periods. At the beginning of the Paleozoic, Cambrian, invertebrates appeared, covered with a solid skeleton built from chitin, calcium carbonate and phosphate, silica. The fauna was mainly represented by benthic organisms - coral polyps, sponges, worms, archeciata, echinoderms and arthropods. Trilobites - the oldest arthropods - have reached their greatest prosperity.

The Ordovician is characterized by the strongest flooding of the Earth and the appearance of a multitude. Arthropods and mollusks were especially widespread during this period, but the first jawless vertebrates also appeared.

In the Silurian, animals and plants came to land. The first were arachnids and centipedes, apparently descended from trilobites. In the Devonian period, primitive jawed fish arose, having a cartilaginous skeleton and covered with a shell. Sharks and lobe-finned fish originated from them, and the first amphibians (ichthyostegi, stegocephals) originated from lobe-finned fish, which are already able to breathe atmospheric air.

In the Carboniferous period, the period of swamps and vast swamp forests, amphibians flourished and the first insects appeared - cockroaches, dragonflies, beetles. Primitive reptiles also appeared, inhabiting drier places. In Perm, the climate became drier and cooler, which led to the extinction of trilobites, large mollusks, large fish, large insects and arachnids. Reptiles were the most numerous at this time. The ancestors of mammals appeared - therapsids.

In the Mesozoic, the Triassic, Jurassic and Cretaceous periods are distinguished. In the Triassic, many reptiles (turtles, ichthyosaurs, crocodiles, dinosaurs, plesiosaurs) and insects arose. At the end of the period, the first representatives of warm-blooded animals appeared. In the Jurassic period, dinosaurs reached their peak of development, the first birds similar to reptiles appeared.

In the Cretaceous, marsupials and placental mammals arose. At the end of the Cretaceous there was a mass extinction of many animal species - dinosaurs, large reptiles, etc. Scientists attribute this to climate change and general cooling. Advantages in the struggle for survival were received by warm-blooded animals - birds and mammals, which flourished in the Cenozoic - the era of new life, consisting of periods of the Paleogene, Neogene and Anthropogen.

The evolution of life on the planet began more than three billion years ago, some scientists say that even more than four billion years. It was then that the first organized ecosystems arose, however, these were microbes and bacteria, and mammals were still very far away. So what were the first animals on Earth?

The very first

The oldest traces of animal life on Earth are about a billion years old, and the oldest fossils of the animals themselves are about 600 million years old.

The first animals that appeared on the planet were microscopically small and soft-bodied. They lived on the seabed or in bottom silt. These creatures could not be petrified, so the only indication of their stay on Earth is the remains of their holes or passages. The individuals were very resilient, it was they who gave rise to the Ediacaran fauna - the first known animals on the planet.

Ediacaran fauna: light at the end of the Vendian tunnel

The Ediacaran fauna takes its name from the Ediacaran Hills that are found in Australia. Here, in 1946, unusual fossils were discovered, outwardly somewhat similar to modern jellyfish, worms and corals. They were small - an average of 2 centimeters in diameter.

At first, scientists decided that the find belongs to the Cambrian period: it was then that the rapid development of the animal world began (approximately 570 million years ago). But upon closer examination, it was possible to establish that these fossils are even older and belong to an earlier period - the Vendian. This was a real discovery, since no one knew for sure whether life existed during this period.

Then representatives of the Ediacara fauna were found in different parts of the world: in Namibia, Russia, Greenland. But despite the findings, biologists are still trying to figure out what happened to them.

This is what one of these ancient animals, Kimberella, supposedly looked like:

Scientists believe that these are the direct ancestors of modern jellyfish and mollusks.

What did the Ediacarans look like?

The structure of the first animals in the world was the simplest: they did not have limbs, heads, tails, mouths and digestive organs. Ediacaran creatures did not lead a particularly bright life)) at that time the planet was safe, there were no predators yet, so they didn’t even have anyone to defend themselves from.

It is assumed that they simply absorbed organic matter from the water with their whole body. Moreover, some of them were symbiosis with algae, and outwardly, many of the creatures were very similar to plants.

So, for example, the largest creature was dikinsonia.

Some individuals reached a meter in length, but usually did not exceed one centimeter in thickness. They had a flat, bilaterally symmetrical corrugated oval body. Such a rug.

Scientists have not decided which group it belongs to: some consider it the ancestor of animals, someone says that it is a kind of mushroom, and still others claim that it generally belonged to a class of creatures that do not exist today in the kingdom of nature. And her modern relatives were never found.

And what happened after the first animals in the world?

The next period in the history of the development of life on Earth is called the Cambrian. It began about 570 million years ago and lasted about 70 million years. It was here that an astonishing evolutionary explosion took place, during which representatives of most of the major animal groups known to modern science first appeared on Earth. And this happened due to good climatic conditions.

In the Cambrian period, huge plumes and continental shoals existed on the planet. There were ideal conditions for life: the bottom, covered with a layer of soft silt, and warm water. A lot of oxygen has already formed in the atmosphere (although much less than now). The development of hard land covers led to the emergence of new life forms, such as arthropods - the first arthropods.

Animals needed new ways to protect themselves from new highly organized predators. As a result of evolution, creatures developed means for protection, respectively, predators had to develop new methods of hunting in order to overcome the resistance of the victim.

During the Cambrian period, the sea level repeatedly rose and fell, species died out, others came in their place, who had to adapt to new living conditions and ways of subsistence.

The animal world became more diverse, and more and more populations could exist next to each other without claiming the food resources of their neighbors.

At the beginning of the next, Silurian period (or Silurian ) the seas and continents retained approximately the same outlines as in the Cambrian. The marine fauna of the Silurian resembles that of the Cambrian, but appear and new groups of invertebrates - corals, graptolites, worms, bryozoans, sea urchins.

Fauna and flora of the late Paleozoic (click to enlarge)

Corals belong to the type of so-called intestinal animals - exclusively aquatic organisms. In addition to corals, the well-known jellyfish and hydra also belong to the intestinal cavities. Corals still exist today; many of them are reef-formers in the tropical zone of the Pacific and Indian oceans. Corals are arranged very simply. Like other coelenterates, their body has only one internal cavity representing the intestines (which is why they are called coelenterates). Externally, the body of a coral, or rather, a coral polyp, is a pouch that opens outwards (above) with a mouth opening around which there is a rim of tentacles that help capture prey. Coral polyps feed on small floating organisms - plankton. Waste products are also ejected through the mouth opening. The body of a coral polyp is enclosed in a skeleton - a calcareous chamber secreted by the walls of the polyp. As the chamber is built up, the polyp itself rises higher and higher, the lower wall of which (the bottom of the sac) deposits horizontal partitions called bottoms.

Coral polyps can live alone (solitary corals) or in groups (colonial corals). Solitary corals reach sizes of 15-20 cm. Like colonial corals, they still grow to the bottom. All corals are inhabitants of the sea. They live in warm clear water, rich in oxygen and well lit, that is, no deeper than 45 m.

Peculiar animals - graptolites . They are known from the Silurian deposits - the so-called graptolitic schists, which are common in our country near Leningrad, in the Baltic states and in Central Asia, and in Western Europe - in England, Germany and Sweden. Graptolites have the appearance of fan-shaped threads or twigs, on the sides of which are numerous tiny cells of polyps. Above, where the ends of the threads converged, during the life of the graptolites there was an air-bearing bell, the imprints of which have been preserved. Probably, graptolites were either passive swimming animals, or some of them crawled along the bottom. Graptolites are classified as hemichordates.

Bryozoans, as the name suggests, are more like plants (mosses) than animals. Bryozoans form colonies that look like crusts and raids on pitfalls or twigs that look like corals. Like coral polyps, each bryozoan sits in a separate cell, but bryozoans are more highly organized animals than corals. Their gastrointestinal tract has not only an inlet, but also an outlet; in addition, they already have a real nervous system (and corals have only individual nerve cells).

The mouth opening of the bryozoan, like that of corals, is surrounded by a corolla of tentacles, the movement of which drives food into the mouth - unicellular algae and unicellular animals. Interestingly, some individuals of bryozoans have the appearance of flagella, continuously vibrating, or bird heads that constantly flap their “beak”. This is a “guard” that drives away enemies of bryozoans, and at the same time silt cleaners. Bryozoans have never been a particularly numerous group, but some of their detachments have survived to the present day.

Sea urchins resemble with their needles real urchins - land mammals, but they have no relationship with them. The body of the sea urchin is enclosed in a spherical calcareous shell, consisting of many plates. These plates form fields, some of which bear needles, while others carry tiny holes. Hundreds of microscopic legs protrude through such holes in the form of soft tubes filled with water. Water is pumped into them through special channels inside the body of animals. With the help of its legs, the hedgehog slowly moves or sticks tightly to some underwater object. In the movement of the sea urchin, spines are also involved, which also serve for protection. Some sea urchins have reached the size of a child's head. Modern marine eyash are found in our northern and eastern seas. They feed on algae and tiny animals.
In the region of the current Scandinavian Peninsula, in Scotland and Ireland, on the site of Svalbard and along the eastern coast of Greenland - where the sea existed for many millions of years - high mountain ranges rose. Their remains are the Scandinavian Mountains, the Grampian Mountains of Scotland, layers crumpled into folds along the eastern outskirts of Greenland and the island of Svalbard. In the second half of the Silurian, powerful mountain-building movements took place - the so-called Caledonian folding.

The mountainous land rose in the region of present-day Kazakhstan and the northern ranges of the Tien Shan, and the Sayano-Baikal mountain arc was formed.

Caledonian mountain building led to the rise of the continents and the gradual shallowing of the seas, the appearance of numerous small bays and lagoons. Some of them were desalinated by the rivers flowing into them, in others the salinity of the water increased and even the deposition of salts occurred.

Most marine animals do not tolerate changes in the salinity of sea water in either direction. Therefore, only a few of the inhabitants of the Silurian Sea have adapted to life in the lagoons.

The "crowding in living space" of the marine population served as an impetus for the development of land as a new additional area of ​​\u200b\u200blife. It was from the dying areas of the sea - lagoons - that the first plants began to land on land, and then animals that fed on these plants, and later predatory animals came to land.

In the Silurian land plants - psilophytes - have already been distributed; apparently, they originated from algae, most likely from green ones.

Their body, like algae, has not yet been dissected into the main organs - root, stem and leaves. Instead of roots, they had peculiar underground unicellular outgrowths - rhizoids. The most primitive of the psilophytes did not even have a stem that would carry true leaves. Psilophytes reproduced with the help of spores placed in sporangia - at the ends of branches. Some psilophytes were marsh plants, while others were real land inhabitants, sometimes reaching considerable sizes - 3 m in height. Psilophytes did not last long. They are known in the next period - the Devonian. Many paleobotanists attribute to them two more genera of modern tropical plants - psilotes. In the Silurian, another group of plants is also common (also, apparently, descended from algae) - mushrooms, which, perhaps, were first aquatic forms, and then came to land. In the same period, more highly organized plants also existed - fern-like, in particular, primitive club mosses. Scorpions appear in the Silurian. These ancient scorpions, perhaps, were not yet terrestrial animals, but first inhabited various water bodies - rivers, lakes and swamps.

And another remarkable event occurred in the Silurian: the first vertebrates appeared - the so-called armored fish, the remains of which are found together with giant crustacean scorpions. Both those and others were inhabitants of lagoons - laced bays of the sea. Probably, armored fish, and after them their enemies - giant crustacean scorpions, climbed up the river deltas, gradually mastering fresh waters.

Until now, there are two points of view on the question of where the first vertebrates appeared - in the seas or rivers. Sea water contains a lot of dissolved calcium, and calcium is part of the bones of animals; in addition, all lower vertebrates live in the sea. This is strong evidence for the marine origin of vertebrates. But supporters of the theory of freshwater origin believe that the skeleton must have appeared in rivers where there is a current: the skeleton is a stable support for the body, necessary to counteract the movement of water.

One thing is certain: the ancestors of vertebrates lived in a zone where fresh waters bordered on sea waters, and their remains are found there. The oldest vertebrates known to us already possessed bone tissue - a shell, while their internal skeleton was, apparently, cartilaginous (it is not preserved in a fossil state). Replacement of cartilage by bone, its ossification occurs much later - in higher groups of fish. The ancient armored fish were not, in essence, true fish yet, they only had a fish-like shape. This body shape - in the form of a torpedo - is generally characteristic of actively swimming aquatic animals, since it provides the least resistance when moving in water.

The ancient armored fishes belong to the group of so-called jawless fishes, which are contrasted with the jawless ones, which include other classes of vertebrates.

Armored jawless are known only from the Silurian and Devonian, but some jawless have survived to the present day; these are lampreys and hagfishes. All jawless, as their name indicates, lacked jaws, as well as paired limbs (fins), and usually had only one nostril. Ancient jawless animals, the remains of which are often found in our Baltic, on the Yenisei and in the Kolyma basin, as well as in Northern Europe and North America, were rather large animals - half a meter or more in length. Their body in front or almost entirely (except for the tail) was enclosed in a shell, consisting of bone plates and scales. This armor protected them from dangerous pursuers - racoscorpions, reaching a length of 3 m.

The armored jawless ones fed on plankton. Probably some of the jawless were benthic forms. Picking their snout in the silt, they stirred it up and caught small organic remains.

Thus, the Silurian was not only the heyday of various groups of invertebrates, but also the time of the appearance of the first vertebrates. In the Silurian, the resettlement of terrestrial plants and the emergence of the first animals on land began.

To live on land, animals need lungs that allow them to extract oxygen from the air. Without lungs, aquatic animals would suffocate and die as soon as they surfaced. But the moment came when many living beings learned to breathe atmospheric air.

Amphibians

The first animals that inhabited the land protruding from the water were amphibians. They never ventured far from the water, because they laid their eggs in the water to breed. The frogs that live in ponds do the same now.

These were:

1. Dolohosoma
2. Urocordilus

At the time when the first animals came out of the water, the fish also changed a lot. Most of them have already become similar to modern fish.

Insects

The noise of wings has already begun to be heard in the ancient forests. These were some creatures, descendants of water scorpion shrimp and other species, which had wings and began to fly. This is how insects were born. There were no birds yet. The most ancient insects were dragonflies. Some of them had a wingspan of up to half a meter.

How were the first amphibians born?

It is possible that some fish acquired the ability to breathe on land for a short time when their water body dried up. They crawled on the ground in search of water, so as not to die. Some of them gradually learned to live on earth.