Cambrian period flora. Animals of the Precambrian and Cambrian period (13 photos)
THIRD - GREAT PRALAIA
600 – 570 million years ago - THIRD PRALAYA OF LIFE (DREAM).Cosmos, Nature is destroyed only to reappear on a more perfect plane after each Pralaya.
During Pralaya before the beginning of the 4th Circuit, all forms of life were in a highly spiritual state of ARUPA - a formless state of development.
570 million years ago there was a displacement of the solid outer crust of the Earth relative to the internal layers. The planet's rotation axis shifted by 90 degrees. The regions located at the North and South Poles moved to the equator, and the equatorial lands became the new poles.
FOURTH CIRCULATION
530 million l. back has begun FOURTH CIRCULATION.The beginning of the Fourth Circuit repeats the evolutionary work of previous Circuits at the highest level.
530-505 million l. n. CAMBRIAN Period
530-250 million l. n. Palaeozoic
"THE ARK"
530 million years ago, a spaceship (ARK) was sent to Earth from the solar system SIRIUS-V.
"This ship is round and has the shape of a disk with a flat bottom and top. Its shell has a thickness of 3 to 5 atoms. It is transparent to the human eye. The ship is driven by the Power of Thought and feelings (psychic energy). This ship is forever "was tied to the Spirit of the Earth. Since then, he has served as the protector of the Earth."
"Half-man, half-snake Nommo, who had red eyes and three pairs of flexible limbs without joints and a smooth, shiny body covered with green algae. God Amma instructed Nommo to populate the Earth. For this purpose, a huge double-decker ship with a round bottom was built. The ship was divided " a whirling vortex" bursting out of the ship through a hole shaped like this wind. At the moment of landing, the ship slid through the mud, and the hole formed after hitting the ground was filled with water and became Lake Debo (an oxbow lake of the Niger River, Africa).
13 civilizations participated in providing the Earth with species of their Animal World from the simplest invertebrates, chordates, to vertebrates (skeleton), amphibians (amphibians), insects, reptiles, marsupials, mammals (viviparous).
EARLY CAMBRIAN
"CAMBRIAN EXPLOSION"
Planet Earth 530 million years ago
530 million l. ago there was a "CAMBRIAN EXPLOSION".
MULTICELLULAR
Numerous groups of multicellular organisms were represented by small organisms (millimeters or first centimeters).
Simple invertebrates
Radiolarians- a subclass of protozoa of the sarcodaceae class. Marine planktonic organisms are close to amoebas, but have a hard skeleton consisting, like diatoms, of silica. It often forms a spherical lattice with spikes protruding in all directions. Cambrian-now.
Radiolaria
Foraminifera- a subclass of protozoa of the sarcodaceae class. They build limestone, organic and organosilicon shells. Foraminifera are abundant in marine plankton, where they feed on smaller organisms. Their long, thread-like pseudopodia protrude from the hole in the shell in all directions and capture food particles. Some foraminifera are as small as a fingernail. Cambrian-now.
Foraminifera
The tropical coasts of the continents were fringed by giant reefs of stromatolites, much like the coral reefs of modern tropical waters. These reefs gradually decreased in size, as rapidly developing multicellular animals actively ate them.
coral reef- this is a huge colony made up of myriads of tiny creatures - coral polyps. Their length is only a few millimeters. They absorb calcium dissolved in seawater, forming a calcareous colony skeleton from it. Depressions are visible on the surface of the reefs: polyps hide in them and wait for their prey. Polyps catch plankton using stinging capsules. Polyps feed on single-celled organisms, as well as worm larvae and tiny crustaceans infesting the plankton. In addition, they absorb nutrients contained in the water. Some corals live in symbiosis with single-celled algae. The algae supply their polyp neighbors with oxygen. These plants also benefit from cohabitation with corals by absorbing the substances they secrete. It is algae that colors tropical coral reefs in amazing colors.
Scientists have not come to a consensus on the origin of his name. Some believe that it comes from the Greek word "koraillon", meaning the hard calcareous skeleton of coral animals, or from - "kura halos", meaning sea fairies, since the coral branches sometimes look like these small figures. Others consider the probable origin from the Hebrew “goral”, stone-lot.
Hydra is a freshwater polyp that is practically immortal. Young cells, formed in her mouth area through constant division, descend to her sole. Thanks to this nourishment, the hydra does not age and, in favorable conditions, can live indefinitely.
Hydra
Some animals, such as jellyfish, for example, know how to control their genes and at the right moment force their cells to “live backward”, returning to early stage development. Jellyfish live almost forever, and if they die, it is as a result of an accident.
The single-celled zygote turns into the multicellular body of the embryo. The embryo becomes like a microscopic hollow ball. Part of the cell wall protrudes into the internal cavity. A single-layer closed blastula turns into a two-layer formation with a new cavity that communicates with the external environment.
1. ECTODERM - outer layer. In vertebrates, the integumentary epithelium, nervous system and sensory organs are formed.
2. ENDODERM - inner layer. Epithelium of the intestines and lungs, pancreas and liver.
Coelenterates have only two layers.
3. Between the ectoderm and endoderm, the MESODERM appears (in vertebrates it forms bony skeleton, muscles, circulatory system, kidneys).
The fact is that the extremely low level of cellular integration leaves sponges with the only possible “profession” - an attached passive filter of organic suspension. Any sponge (including archaeocyaths) is a bag open at the top, the walls of which are pierced by channels; water constantly moves through them into the internal (paragastric) cavity, then exiting out through the upper opening (ostium), and the choanocytes (collar flagellar cells) included in the walls of the canals filter out the organic matter and bacteria contained in the water. Question for the school Olympiad: what force makes water move through channels in a stationary wall? Answer: the same thing that creates furnace draft - the difference in pressure at the height of the ash and at the height of the end of the pipe in accordance with Bernoulli’s law: if the aqueous medium in which the sponge is located has a non-zero speed, then the layer of moving liquid above the mouth creates a “suction” . It’s a well-known fact: the higher the pipe, the better the traction; Accordingly, the sponge can pump water through itself only when its mouth is raised above the substrate. (A similar mechanism provides ventilation for the burrows of gophers and other rodents. The one of the exits through which soil was thrown out when digging a burrow turns out to be enclosed in a mound-“molehill” and is slightly raised above the ground; as a result, a steady flow of air from the “low” exit appears inside the burrow to "high"). The rise of the mouth above the substrate can be ensured only in the presence of a solid supporting skeleton - organic or mineral (modern sponges have both options). The absence of these easily detectable skeletal elements - spicules - in previous sediments indicates that this group of living organisms actually arose only at the beginning of the Cambrian, i.e. when true multicellular animals undoubtedly already existed.
The basis of the ecosystems of that time, however, were algae, which built small limestone structures - bioherms, and an extinct group of organisms - archaeocyaths.
Archaeocyathae(in Greek - “ancient cups”) look like small glasses (goblets) with a double-layer wall; lifestyle-attached; The diameter ranges from several millimeters to several centimeters; gigantic forms up to 1.5 m in size have also been found in Siberia.
Archaeocyathae. (a) – Archaeocyatida, (b) – Capsulocyatida, (c) – Kazachstanicyatida, (d) – Archaeocyatida.
Their nature caused controversy for a long time (it was not even clear whether they were animals or plants, or even a separate kingdom), however, Lately almost all researchers agree that they should be classified as sponges. Moreover, not so long ago a strange deep-sea sponge Vacletia was found in the Pacific Ocean, which, upon examination, turned out to be an archaeocyath that has survived to this day and has added to the gallery of “living fossils” (like lobe-finned fish or ginkgo).
The entire geological history of archaeocata (appearance, flourishing - about 300 genera, - decline and extinction) fits into a tiny interval by geological standards of 15-20 million years. Already in the second half of the Cambrian, this group, which flourished at the beginning of the period, disappears, and at the same time no one comes to replace it - that is, it is difficult to assume competitive displacement here. It seems that the archaeocyaths were exploiting some resource that was at first abundant and then became sharply scarce. This group flourished in that relatively short and fundamentally unstable period, when the development of pellet transport had already enriched the bottom layers with oxygen, but had not yet concentrated most of the organic matter inside the sediment; this alignment, as A.G. believes. Ponomarenko, should be very favorable for “thin” filter feeders. In order to exploit the discovered resource, there is no need for “skilled labor” - macroscopic organisms, even those that are not multi-tissue, are quite sufficient. However, further development of the situation with the storage of organic matter in sediment (which makes it possible to make its processing more uniform and improve the supply of oxygen to the bottom layers) sharply worsens the situation of bacteria and passive filter feeders, but favors silt eaters. The time of archaeocyaths ends, and the time of trilobites begins.
Flatworms- they have bilateral body symmetry, a more advanced nervous system, they are hermaphroditic (have male and female genital organs).
Annelids, annelids- type of higher worms; related to arthropods. For the first time, a circulatory system (closed) is formed; the blood is colorless. They feed on rotting plant debris. Cambrian-now.
Mollusks (invertebrate aquatic animals) evolved from annelids.
Konodonten- the earliest toothed worm was found in a layer 515 million years old. The teeth of this ancient animal are plates of bone tissue up to 6 mm in size. Conodontens were predators and inhabited the Earth for about 300 million years, they disappeared by the time of the heyday of dinosaurs. According to researchers, the “teeth” of some conodonts were like filtering devices, with the help of which plankton was filtered from the water and sent into the pharynx. Other teeth, based on their structure, in their opinion, were intended to “grab and tear flesh.” The lateral location of the eyes of conodonts, however, makes it unlikely that they predatory image life. Preserved muscle prints suggest that some conodonts (Promisums, in any case) were skilled swimmers, however, incapable of rapid throws.
From the eleven known complete fossilized prints of conodont-bearing organisms, it can be concluded that they were eel-like creatures, the oral apparatus of which consisted of 15 or, less commonly, 19 elements and was radically different from the jaws of modern animals. The shape of the elements is tooth-shaped, comb-shaped, leaf-shaped; composition - calcium phosphate.
Among the conodont-bearing species there were both very tiny (about 1 cm long) and gigantic ones (for example, Promissum, whose length reached 40 cm). Currently, archaeologists agree that conodont-bearing organisms are characterized by the presence of large eyes, fins with fin rays, a notochord, and powerful transverse muscles.
Conodont-bearing organisms are currently classified as chordates due to the presence of fins with fin rays, a notochord, and powerful transverse muscles.
Some researchers classify conodont-bearing species as a subphylum of vertebrates. In their appearance they are similar to modern hagfishes and lampreys. Cambrian-Triassic.
The Animal Kingdom is divided into two divisions: protostomes and deuterostomes.
Protostomes- in representatives of which the oral opening of an adult animal arises in place of the embryonic mouth.
Priapulids are a type of marine protostomes, similar to roundworms. They live in the thickness of sea bottom sediments. Most representatives lead a burrowing lifestyle or live in the interstitium. Two species of the genus Maccabeus are semi-sessile seston feeders. Excretory system associated with the reproductive system. Dioecious, development with metamorphosis. Cambrian-present; flourished in the Cambrian.
Ottoia prolifica is a Cambrian period priapulid fossil sea worm. Paleontologists discovered a large number of her fossil remains in the Burgess Shale. Ottoia lived in burrows on the seabed and led a predatory lifestyle.
Ottoia prolifica
The oldest lobopod (and the oldest arthropod in general) is considered to be Diania cactiformis (class Xenusia), known from fossil remains from the Maotianshan shale in Yunnan province (China), dating back to about 520 million years. The limbs of Diania were apparently protected by armor, which later gave rise to the exoskeleton found today in all arthropods - a hard and very durable shell made of chitin.
The most famous (thanks to the BBC series Walking with Monsters) of the lobopods is Anomalocaris.
The oldest arthropod Diania cactiformis 
Various Cambrian animals: lobopods (a-b), arthropods of unclear systematic position (c-e), trilobites (f-g). (a) – Xenusion; (b) – Aysheaia; (c) – Wiwaxia; (d) – Anomalacaris; (e) – Opabinia; (f) – Olenoides, (g) -Ogygopsis.
The most highly organized among protostomes are arthropods and mollusks.
SHELLFISH- invertebrate aquatic animals, they have a heart that is not closed circulatory system. They are descended from annelids.
Hyolites(lat. Hyolitha) - a class of mollusk type, close to spadefoots. Hyolites are bilaterally symmetrical animals with a shell of two valves. The shell was conical or pyramidal, from 0.1 to 15 cm in length, open at the wide end; the mouth of the shell was closed with a lid. The shells of some chiolites were divided by transverse partitions into a number of air chambers and one living chamber. The shell of some species was “decorated” with stripes and rings. Some chiolites had a pair of thin long appendages extending from the mouth, the purpose of which is unknown. Some scientists consider chiolites as a class of Mollusks (moreover, they are similar to Shovelopods (Scaphopoda)), others consider them a separate type of animals. Some data allow us to bring them closer to Sipunculids. Chiolites are leading fossils important for the stratigraphy of Cambrian deposits. Cambrian-Perm; flourished in the Cambrian.
Hyolite
ARTHOPODAS(crabs, amara, lobsters, shrimps, daphnia crustaceans) originated from annelids. Arthropod limbs appear and compound eyes develop.
Most creatures living in shallow seas were invisible and invulnerable thanks to their bodies covered with strong exoskeletons. These armored animals were called ARTHROPODA(ARTHOPOD - highest type protostomes, whose representatives have a jointed external skeleton made of chitin. Unites both primary aquatic animals that breathe with gills, as well as terrestrial and secondary aquatic animals that breathe with the help of “book” lungs and tracheas). From them will come insects and spiders. They had developed sense organs, had limbs, a skeleton-spine and a heart.
Cheliceraceae- a subtype of arthropods that combines both primary aquatic forms with gill respiration (horseshoe crabs and crustaceans) and terrestrial forms with pulmonary and tracheid respiration (arachnids). Cambrian-now.
Trilobites- class of gill-breathing arthropods; exclusively marine benthic forms. The morphology of the body of trilobites fully corresponds to the organization of the type of arthropods, however, they have similarities with the type of annelids (in particular, their body consisted of many homonomic segments). The body structure of trilobites bears evidence of adaptation to a benthic lifestyle: a powerful shell, flattenedness, compound eyes on the upper side of the body, the location of the mouth and legs on the ventral side of the body.
The limbs of trilobites are multifunctional, that is, they performed several functions at once - motor, respiratory and chewing. The appendages of the ventral side, discovered recently, consist of: 1) four pairs of limbs above the head shield on the sides of the mouth opening, consisting of 6-7 segments and serving partly as chewing organs. The end members of the posterior pair looked like swimming blades; 2) from paired two-branched limbs, located both under the body and under the caudal segments, consisting of a certain number of segments ending in claws. Above the outer branch there were also special two-branched and spirally coiled appendages, considered as gills.
The body is divided into a middle, or axial, part (rachis) and lateral parts (pleura), while on the caudal shield, as a continuation of the 3 corresponding parts of the body, an axial lobe and lateral lobes are distinguished. The axial parts of the body and tail shield in the fossilized state are open from below, since they were covered during life with thin skin, but the lateral parts have preserved a solid turn, usually distinguished by special lines decorating it.
The head shield (cephalon) has the shape of a semicircle. The middle part of the head shield is called the glabella, the lateral parts are called the cheeks (librigenae); the posterior corners of the cheeks are often elongated into more or less long buccal points. The head shield rarely consists of one continuous part, but is usually divided using special lines or so-called sutures into several separate parts, along which the head shield often disintegrated after death and during the processes of petrification. These separate parts also include a special plate on the wrapped part of the shield, the so-called hypostome (or upper lip), which probably served as a cover for the abdomen. According to scientists, the head of trilobites contained a stomach, heart and brain.
Some trilobites have visible organs of touch - a pair of long antennae on the head in front of the mouth opening. Trilobites had compound eyes, which were set on stalks in those animals that buried themselves in the mud. Representatives of the order Agnostida are completely devoid of eyes, which is apparently associated with life on great depth or in muddy water.
Among trilobites, some groups fed on mud, others on small invertebrates, and some on plankton. Many trilobites were probably predators, despite the lack of jaws. To grind food, they used modified appendages on the bases of the limbs (gnathobases). There were free-swimming, crawling, and burrowing animals.
The development of trilobites occurred with metamorphosis: egg, larva, adult. A significant part of the fossil finds of trilobites are on dorsal shells, which the animals shed during molting, and therefore lack a movable part of the cheek. There is evidence that trilobites molted sequentially, and after each molting their body increased by several segments. Fossil eggs and larvae of trilobites have been preserved. This method of reproduction is characteristic of modern horseshoe crabs. Scientists believe that trilobites were bisexual. Evidence of this is the presence of a brood pouch.
According to one version, the ancestor of trilobites was spriggina, an organism of the Vendian Period about 3 cm long. The popularity of this hypothesis is now less than in the past; it is likely that the similarity of these organisms is purely superficial. Cambrian-Perm.
Trilobite Order Phacopida
Deuterostomes- in representatives of which, during ontogenesis, the mouth of the embryo closes and the oral opening of an adult animal appears in a different place.
Brachiopods(Brachiopoda) - a type of deuterostome invertebrates; They have a bivalve shell and are similar in appearance to bivalves. They made up 30% of the species of the known Cambrian fauna. The durable shells of most Cambrian brachiopod species were composed of a chitinous substance impregnated with calcium phosphate, while the shells of later forms were composed primarily of calcium carbonate. Accumulating brachiopods in favorable places in innumerable quantities, brachiopods provided a significant part of the material in the formation of underwater reefs and barriers. In the Paleozoic marine fauna, brachiopods outnumbered all other types of animals. They are present in almost all marine sediments of this time. Cambrian-now. Heyday in Devon.
Primitive Ordovician brachiopods of the genus Plectorthis in the rock. Ortids (Є-R) were most likely the ancestors of all castle brachiopods. 
Brachiopod. A representative of the order Spiriferida is the Middle Von Mucrospirifer.
The pinnacle of deuterostome evolution are the vertebrates.
To the inhabitants of shells and living tubes are added creatures with fundamentally different types of hard skeleton - internal (chordates) and mobile external (arthropods).
CHORDATES- a type of higher deuterostome animals, combining vertebrates and lancelets. Cambrian-now.
LANCELANDS- a class of chordates, forming a separate subtype - skullless.
Small fish-like animals that burrow into the sand in shallow sea waters. Cambrian-now.
VERTEBRATES- the highest subtype of the chordate type, whose representatives have a bony or cartilaginous internal skeleton. Divided into superclasses of fish-like fishes (jawless, cartilaginous fishes and bony fish) and tetrapods (amphibians, reptiles, birds and mammals). Ordovician - now.
The first to achieve success were arthropods and related arthropod-like forms. The largest predator of those times was Anomalacaris.
Anamalocaris
Anomalocaris eyes
A number of unrelated groups at this time begin to independently acquire individual characteristics of arthropods, as a result of which they reach the arthropod level of organization.
“Many animals - especially among the lower species of vertebrates - have a “Third Eye”, now atrophied, but which undoubtedly operated at its origin. In some aquatic vertebrates, this organ has retained the structure of the eye - with a lens and photoreceptors.”.
LATE CAMBRIAN
At the end of the Cambrian, cephalopods appeared. These were sedentary forms, related to the modern nautilus, but with an untwisted conical shell, the so-called straight cephalopods. They reigned supreme in the bottom layers of the ocean until about the middle of the Silurian; The Ordovician marked the peak of species diversity of this group of animals (about 150 genera).
Nautiloids- a subclass of cephalopods with an external shell, straight or curled. Nautilus- a cephalopod, the only representative of nautiloids that has survived to the present day. Distributed in the southwestern Pacific Ocean.
Predators from among arthropods (crustaceans and aquatic chelicerates - horseshoe crabs and crustaceans) and vertebrates (jawless - relatives of modern lampreys) turn out to be “uncompetitive” and occupy a subordinate position in ecosystems.
Nitrogen
The atmosphere gradually became oxygen-carbon dioxide-nitrogen. Main role began to purchase NITROGEN. The carbon dioxide content decreases and the oxygen content increases.
3.5 billion liters ago PHOTOSYNTHESIS arose - the creation of pigment systems for the use of light energy. Photosynthesis is a process that takes place under the influence of sunlight, as a result of which carbohydrates are formed from CO2 and water and oxygen is released. Communities of photoautotrophs form unique oxygen oases in an oxygen-free desert; their capabilities are sufficient to create oxidizing conditions (and the precipitation of iron in oxide form) only in their immediate environment.
2.7 billion liters ago, oxidative processes began to predominate in the atmosphere, the earth's crust became more acidic in composition, and the rapid growth of granites began.
Free oxygen began to be released into the atmosphere. The oxygen content in the atmosphere reached 1% of modern levels.
Aerobic oxidation gradually displaces the anaerobic (oxygen-free) one.
1.4 billion liters ago, red granite strata began to form in the earth's crust, as a result of which the oxygen content in the atmosphere increased. Later geological processes oxygen was gradually added to the atmosphere. 650-600 million l. ago, the entire hydrosphere was saturated with oxygen to a level that allowed the existence of macroscopic animals.
During the last era of granite formation, ca. 400 million l. n. its content has approached the modern level.
Up to 450 million liters n. (Silur) very warm climatic conditions prevailed on the planet.
At the end of the Cambrian about 500 million years ago there was extinction, which led to an unprecedented renewal of the fauna and the formation of new ecological niches in the Ordovician period. As a result, at the beginning of the Ordovician (485 million years ago), diversity marine fauna was twice as high as the Cambrian, and in the middle of the Ordovician (470 million years ago) - already five times. The so-called Cambrian evolutionary fauna, with its dominant groups of animals, was replaced by the Paleozoic, already with its dominants.
Before the start of the Cambrian period, 542 million years ago, life on Earth consisted mainly of single-celled bacteria and algae, but after the Cambrian, multicellular organisms and animals began to dominate the oceans. The Cambrian was the first period (542-252 million years ago), which lasted about 57 million years, and then was replaced by and periods. These periods, as well as subsequent eras, were dominated by vertebrates, which originally evolved during the Cambrian.
Climate and geography
Not much is known about the global climate during the Cambrian period, but unusually high levels of carbon dioxide in the atmosphere (about 15 times higher than today) meant that average temperatures could exceed 50°C. About 85% of the Earth was covered in water ( compared to 70% today), most of this area was occupied by the vast oceans of Panthalassa and Iapetus; the average temperature of these vast seas could range from 38 to 43° C. By the end of the Cambrian, 485 million years ago, the bulk of the planet's land mass was concentrated on the southern continent of Gondwanaland, which had only recently broken away from the even larger Pannotia in the preceding Proterozoic eon.
Sea life
Invertebrates
The main evolutionary event of the Cambrian was the “Cambrian explosion” - a phenomenon that entailed sudden change in the bodies of invertebrate organisms. This process lasted tens of millions of years.
opabinia
For some reason, the Cambrian saw the appearance of some truly bizarre creatures, including the five-eyed Opabinia, spiny Hallucigenia, and the great Anomalocaris (which was one of the largest animals of its time).
Vivaxia
Most of these did not leave a single living descendant. This has prompted speculation about what might have happened in subsequent geological eras if, say, an "alien" vivaxia had evolved.
However, so prominent representatives invertebrates were far from the only life forms in the ocean. The Cambrian period marked the worldwide spread of early plankton, as well as trilobites, worms, tiny mollusks and small protozoa. In fact, the abundance of these organisms allowed Anomalocaris and other animals to thrive; these larger invertebrates were at the top and spent all their time feeding on the smaller invertebrates that were in close proximity to them.
Vertebrates
The Cambrian period saw the earliest identified proto-vertebrate organisms, including Pikaia, and slightly more advanced Myllokunmingia And Haikouichthys. These three genera are considered the earliest prehistoric fish, although there is still the possibility that earlier candidates from the late Proterozoic will be discovered.
Vegetable world
There is still some controversy as to whether any true plants existed during the Cambrian period. If so, they consisted of microscopic algae and lichens (which do not tend to fossilize). It is known that macroscopic plants such as seaweeds had not yet evolved during the Cambrian period, as evidenced by a noticeable gap in the fossil record.
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CAMBRIAN PERIOD
The Cambrian period received its name from the county of Cambria (England), as sediments of the Cambrian period were first described here.
In the Cambrian, on the site of North America and Greenland, there was the continent of Laurentia. The Brazilian continent extended south of Laurentia.
The African continent at that time included Africa, Madagascar and Arabia. To the north of it was located the small Russian continent.
Where China is now, there was the Chinese continent, and to the south of it was the huge Australian continent, covering the territory of modern India and Western Australia. At this time, the Northern Appalachians, the Chingiztau Mountains in Kazakhstan and the Salair-Sayan Range were formed.
Of the Cambrian deposits, the most common are limestones, dolomites, and clayey shales. Shallow lagoon deposits are also common: sandstones and clays with layers of rock salt and gypsum.
In the northern hemisphere, several zones can be distinguished in which the climate was dry and hot.
Thick layers of salts and gypsum were deposited in these places. Australian limestone deposits with desiccation cracks also indicate a hot and dry climate on the Australian mainland during the Cambrian period.
All life in the Cambrian period was closely connected with the aquatic environment.
There was no life on land yet. Calcareous algae that lived in seawater are known from plants of the Cambrian period. After they died, accumulations of limestone were formed, known as oncoids. Without a doubt, there were other algae in the Cambrian seas: blue-green, red. But they did not have solid formations, so their remains have not survived to this day.
Algae, releasing free oxygen, significantly changed the composition of the Cambrian atmosphere.
This created the opportunity for the development of other forms of life, in particular those groups of animals that consume free oxygen. Our knowledge of the animal world of the Cambrian period is very limited.
Cambrian rocks were repeatedly metamorphosed, leading to the disappearance of many prints and fossils. Many Cambrian deposits have not yet been studied. The best studied animals were those that lived in shallow seas near the coast.
The fauna of the relative deep water and open ocean is almost unknown to us.
Along with numerous representatives of single-celled organisms, colonial organisms also lived in the seas of the Cambrian period.
Many fossilized passages made by some worm-like creatures have been preserved. From Cambrian deposits, only individual representatives of the type of mollusks common in our time are known. The shells of bivalves and gastropods are similar to modern freshwater forms. Among cephalopods, large horny organisms are known, the shells of which are divided into chamber-tubes about 8 mm long and 1 mm wide. Inside the chambers there was a thin tube (siphon).
Cambrian period
The Cambrian system (Cambrian) (from Cambria (Cambria) - the Latin name for Wales) is the first system of the Paleozoic era, corresponding to the first period of the Paleozoic era of geological history. The system was first identified by the English researcher A. Sedgwick in 1835.
The Cambrian period began 542 ± 2 million years ago.
years ago and lasted ~54 million years. This period began with an astonishing evolutionary explosion, during which representatives of most of the main groups of animals known to modern science first appeared on Earth. The boundary between Precambrian and Cambrian runs along rocks, which suddenly reveal an astonishing variety of animal fossils with mineral skeletons - the result of the "Cambrian explosion" of life forms.
One of greatest mysteries in the history of the development of life on Earth. It took 2.5 billion years for the simplest cells to develop into more complex eukaryotic cells, and another 700 million years for the first multicellular organisms to arise. And then, for just 100 million.
years, the world was populated by an incredible diversity of multicellular animals. Since then, for more than 500 million years, not a single new type (fundamentally different body structure) of animals has appeared on Earth.
In the Cambrian, on the site of North America and Greenland, there was the continent of Laurentia. The Brazilian continent extended south of Laurentia. The African continent at that time included Africa, Madagascar and Arabia. To the north of it was located the small Russian continent.
A fairly wide sea basin separated the Russian continent from the Siberian continent, which was located on the site of modern Western Siberia.
Where China is now, there was the Chinese mainland, and to the south of it there was the huge Australian mainland, covering the territory of modern India and Western Australia.
At this time, the Northern Appalachians, the Chingiztau Mountains in Kazakhstan and the Salair-Sayan Range were formed. Of the Cambrian deposits, the most common are limestones, dolomites, and clayey shales. Shallow lagoon deposits are also common: sandstones and clays with layers of rock salt and gypsum.
In the northern hemisphere, several zones can be distinguished in which the climate was dry and hot. Thick layers of salts and gypsum were deposited in these places.
Australian limestone deposits with desiccation cracks also indicate a hot and dry climate on the Australian mainland during the Cambrian period.
The climate of the African continent was apparently warm and humid. South Australia, China and Norway had glaciers. When comparing the shores of the Cambrian seas with the shores of modern seas, we can conclude that most of the earth's surface during the Cambrian period was land.
There were many volcanic islands in the shallow seas. Cambrian flora and fauna spread across the globe from the Cambrian tropical seas.
The flora of the Cambrian period is represented by blue-green and red algae and primitive higher plants.
Among the mineral resources of the Cambrian period, deposits of phosphorites are significant.
The Cambrian period saw rapid development of the animal world.
Cambrian period, or Cambrian (542-485 million years ago)
Some animals that appeared at this time never survived the Cambrian period, such as animals found in the Burges Shale. The Cambrian period also gave rise to all the major groups of animals that exist today, including vertebrates, that is, the group to which we humans belong.
This amazing evolutionary explosion, known to paleontologists as the Cambrian fossil explosion, is difficult to explain.
Nothing like this ever happened again, so why did it happen then? Scientists do not know this, but they have made many assumptions. One of them is that this “explosion” was not at all as amazing as it seems to us now. According to this theory, many species of animals could have existed before the “explosion,” but since they were soft-bodied, there were few traces of their existence.
Many scientists believe this assumption is correct, but they also believe that the “Cambrian explosion” really happened, although it was not as dramatic as it might seem at first glance. It could be caused by changes in oxygen levels in the atmosphere or the topography and structure of the seabed. It is also possible that life has reached some critical point, which entailed chain reaction, during which many new forms of living beings were formed.
The Cambrian period is known as a time when trilobites flourished due to the important role these animals played in life on the seafloor.
Transparent, gelatinous jellyfish, large and small, swam on the surface of the Cambrian sea. They crowded into the backwaters, waiting out the storms, and again fluttered freely on the surface of the sea, merging with the sea water, sparkling in the sun. Sometimes the wind and waves washed the jellyfish onto the sand, and they dried up, leaving behind faint imprints. Jellyfish lived in the seas for hundreds of millions of years without changing.
The climate, the composition of the atmosphere, and the salinity of the water changed, but they remained unchanged, because they were ideally adapted to life on the surface of the water.
And at the bottom of the Cambrian seas lived archaeocyaths. Translated into our language, archaeocyath means an ancient bowl. And indeed, with their shape, these animals resemble some kind of fancy glasses, glasses, bowls.
There was a void inside these limestone glasses, and archaeocyaths were attached to the soil with limestone heels. The limestone walls of these bowls had numerous holes through which sea water freely penetrated, washing their soft body, bringing small edible particles to it. Their structure resembles the ancient bowls of modern limestone sponges, but they also had properties that can only be found in corals.
From birth until death, these animals lived in one place, entrenched in the ground, as plants do, without chasing prey, without moving.
It is not for nothing that corals are now often called animal-flowers. But unlike plants, they fed on small plankton and were incapable of photosynthesis, like plants. This means that they were animals after all.
Archaeocyaths did not live long.
Already at the end of the Cambrian they completely disappeared from the bottom of the Cambrian seas and oceans. And they did not live in vain, since it is from these ancient creatures that two large groups of animals originate - sponges and corals. The descendants of the archaeocyaths, more advanced in structure, quickly supplanted their ancestors, stealing food and places suitable for life from them.
Unlike the seas of our time, which are filled with a wide variety of mollusks, there were few of them in the Cambrian seas.
Cephalopods, the distant ancestors of modern octopuses, cuttlefish and huge squids, were small creatures in Cambrian times whose horny shells were divided into a series of small chambers.
In the middle of the rooms ran a thin tube, the so-called siphon, connecting the rooms, allowing the animal to fill them with water or gases.
Brachiopods, or brachiopods, also lived in the Cambrian seas, which scientists named so because they had two fleshy arms, coiled like a clock spring.
Brachiopods were attached to the soil by means of a cartilaginous stalk. The worm-like body of these animals already had a well-developed circulatory system, a stomach, greenish glands - the liver, a pulsating bladder-heart, pigment spots - the eyes.
These animals are very interesting for paleontologists, because by studying them, one can understand how and from what complex organs such as eyes, heart, kidneys were formed...
Unlike simple animals, into whose body sea water freely penetrated, carrying with it oxygen and nutrients, the body of brachiopods is already reliably protected by tissue. But, of course, they could not do without sea water completely. Brachiopods, so to speak, took part of the sea into their bodies. Their colorless blood, which carried oxygen throughout the body, is practically no different in its chemical composition from sea water.
The most ancient brachiopods had a chitinous shell, similar to the shell of modern insects.
It is these brachiopods, having lived for hundreds of millions of years, almost unchanged, that have survived to this day.
The ancestors of mollusks and brachiopods were obviously worms. The oldest of the mollusks, which appeared in Precambrian times, differed little from these ancestors in both shape and body structure.
But they already had one significant difference, namely, a turtle. Perhaps the first shells were formed from chitin, because there was still very little lime in the water of the Precambrian seas, therefore, there was nothing for the first mollusks to build a limestone hut from.
But later, when there was more lime in the water, the seas were populated by mollusks with limestone shells. And then real thickets of archaeocyaths and sponges arose at the bottom of the seas...
Cystoids rose above the seabed on long stems. At the tops of the stems there were limestone cups that resembled unopened flower buds.
Tentacle arms were attached to the cups, with which the cystoids pressed seawater with edible particles to their mouths. So, unlike archaeocyaths and sponges, which passively waited for the sea waves to bring them food, cystoids obtained their own food.
Sea crayfish were already crawling along the seabed. Their elongated body was reliably protected by a hard chitinous shell, and three eyes allowed them to both examine their prey and notice them from afar. dangerous predators- cephalopods.
The crayfish of the Cambrian period already had tentacles that were good at holding captured prey. Some of them swam well, rowing with flat limbs and a wide tail. Among the crayfish there were herbivores that ate seaweed, and there were also predators. At first they lived only in sea water, but then they also inhabited freshwater pools. It is from them that our crayfish came from.
Cambrian period.
From 570 to 500 million years ago.
The Cambrian period began approximately 570 million years ago, perhaps slightly earlier, and lasted 70 million years. This period began with an astonishing evolutionary explosion, during which representatives of most of the main groups of animals known to modern science first appeared on Earth.
The boundary between Precambrian and Cambrian is marked by rocks that suddenly reveal an astonishing variety of animal fossils with mineral skeletons—the result of the “Cambrian explosion” of life forms.
No one knows exactly what the world map looked like in the Cambrian era, it is only clear that it was very different from today. Across the equator stretched the huge continent of Gondwana, which included parts of modern Africa, South America, Southern Europe, the Middle East, India, Australia and Antarctica.
In addition to Gondwana, there were four other smaller continents on the globe, located in what is now Europe, Siberia, China and North America (but together with northwestern Britain, western Norway and parts of Siberia). The North American continent of that time was known as Laurentia.
In that era, the climate on Earth was warmer than today. The tropical coasts of the continents were fringed by giant reefs of stromatolites, much like the coral reefs of modern tropical waters.
These reefs gradually decreased in size, as rapidly developing multicellular animals actively ate them. On land in those days there was neither vegetation nor soil layer, so water and wind destroyed it much faster than now.
As a result, large amounts of sediment were washed into the sea.
Skeleton Riddle
Animals, until they had formed solid skeletons, were very rarely preserved in the form of fossils.
Accordingly, very little information about them has reached us.
But why did so many animals develop skeletons now, and not before, in the Precambrian?
It seems that a certain amount of oxygen is required in order for the animal's body to deposit the minerals necessary for the formation of the skeleton. Perhaps the oxygen concentration in the atmosphere became sufficient for this only in the Early Cambrian.
The first skeletons were composed primarily of calcium carbonate.
New predators ate the ancient stromatolite reefs, and as they collapsed, they released more and more calcium into the ocean waters, suitable for the formation of skeletons and shells. Shells and shells not only served reliable support organism of animals, but also protected them from the abundance of predators that appeared around them.
More rigid skeletons allowed the animals to switch to a new way of life: they were able to rise above the bottom silt, and therefore move faster along the seabed.
As soon as animals developed articulated limbs, a wide variety of methods of locomotion became available to them, including walking and swimming. The bristly limbs were also suitable for filtering food from sea water, and the articulated mouthparts opened up new opportunities for capturing prey.
Animal world Burgues shales.
Eldonia jellyfish (1) sways among tree-like glass sponges (vauxia) (2). The strange arthropods Protocaris (3) and Plenocaris (4) swim past Mackensia (5), presumably a species of sea anemone.
It seems tiny compared to the huge predatory Anomalocaris (6), whose powerful mouth may have been capable of crushing the shells of other arthropods. Crustaceans such as burgessia (7) and canadaspis (8) grazed in the mud layer, sucking food particles from it.
Naroya (9) was a primitive soft-bodied trilooite, and the bizarre Vivaxia (10) was a variety ringworm, covered with plates and spines, like canada (1 1).
Even more strange creatures there was Opabinia (12) and Hallucigenia (13), unlike any living animal, and a worm-like odontogryphus (14) with a horseshoe-shaped mouth surrounded by tiny teeth and tentacles.
"Cambrian Explosion"
The Cambrian evolutionary explosion is one of the greatest mysteries in the history of the development of life on Earth.
It took 2.5 billion years for the simplest cells to develop into more complex eukaryotic cells, and another 700 million years for the first multicellular organisms to arise. And then, in just 100 million years, the world became populated by an incredible diversity of multicellular animals. Since then, for more than 500 million years, not a single new type (fundamentally different body structure) of animals has appeared on Earth.
During the Cambrian period, there were huge areas on Earth occupied by the continental shelf, or continental shoals.
Ideal conditions for life have been created here: a bottom covered with a layer of soft silt and warm water. By this time, a lot of oxygen had formed in the atmosphere, although there was less of it than today. The development of hard surfaces led to the emergence of new life forms, such as arthropods and arthropods.
Animals needed new ways to protect themselves from new highly organized predators. Their means of defense have improved, and predators have had to develop new hunting methods to overcome the resistance of the prey.
During the Cambrian period, sea levels rose and fell repeatedly.
At the same time, some populations died out, and their habitats were occupied by other animals, which, in turn, had to adapt to new living conditions. Over time, Cambrian animals mastered more and more specialized feeding methods. The fauna became more diverse, and more and more species of animals could exist side by side, without claiming the food resources of their neighbors.
Never again on our planet will there be so many unoccupied ecological niches and such weak competition between species - in other words, such unlimited opportunities for experimentation on the part of nature.
Burgess Shale
In 1909, the American paleontologist Charles Doolittle Walcott made one of the “discoveries of the century.”
Cambrian period (Cambrian)
In the Canadian Rockies, at an altitude of about 2400 m, he discovered a small lens of shale with what appears to be a number of very strange fossils of soft-bodied animals, many of them perfectly preserved.
They lived in the early Cambrian in muddy shallow waters adjacent to a large reef. Apparently, part of the muddy shore collapsed and carried these animals with it into a deep bottom depression, capturing along the way some of those who lived in the water column above the reef; they were all quickly buried under a thick layer of silt.
Scientists believe that the Burgues Shale was formed at the dawn of the Cambrian period.
They contain the most various types animals not found in older breeds. Here are arthropods, which crawled in the mud, eating detritus (organic remains), and their relatives - active swimmers and get food by filtering water. Some swimming arthropods, such as the sidney, may have been predators. Other animals lived either on the mud or in its thickness. Among them are numerous varieties of sponges; Brachiopods (brachiopods) settled on the long branches of some of them to filter water.
A strange collection of ancient creatures
Exploring the Burgess shales, Walcott established about 70 genera and 130 species of various animals in them.
He assigned many of them names taken from the local dialects of the North American Indians. Thus, “vivaxia” means “windy” - a very suitable description for this area, and “odaraya” comes from the word “odarai”, which means “cone-shaped”.
The animals themselves turned out to be no less strange than their names. Some of them can still be attributed to some modern group of animals, but most have nothing in common with any other creature known to us, extinct or living today.
Let's say, at goshutzshensh, extremely unusual creature, had a bulbous head and a row of spines running along the back.
Opabinia had five eyes - four of them on stalks - and a long flexible stigma, with which it apparently sucked detritus from the seabed. The tip of the Opabinia stigma forked and was crowned with strange processes. Perhaps she used it as a kind of claw to grab food? Or did the appendages simply push food back into the mouth when it fell out?
Some animals seemed to have traits shared by several modern types.
Odontogus rifus, for example, resembled a flat, segmented worm, but had arthropod-like antennae and many tiny teeth growing around its mouth.
The Nekto Caris had a head and upper body like a crustacean, and a lower body and tail like a vertebrate.
Reconstruction of the Late Cambrian shallow seafloor. Numerous trilobites are present here: paradoxid (1), bailiella (2), solenopleura (3), hyolite (4) and agnostus (5).
Sea feathers (6), archaeocyaths (7) and floating graptolites (8) (Dictyonemas) filter water in search of food, and ancient brachiopods (Lingulella) (9) and Billingsella (10) pass water through their shells, using them as a filter.
Great experiment?
It seems that during the “evolutionary explosion” of the Cambrian period, nature almost deliberately experimented with a huge number of different life forms.
True, in the end only very few of them have survived to this day. During the Cambrian, many strange types and “projects” of animal structure arose that have long since disappeared from the face of our planet. There were many groups of animals that were well known to us at that time. In fact, by the end of the Cambrian period, all of the current types of solid-bodied animals had appeared, with the exception of only one.
So why hasn't evolution produced new types of animals since then?
Maybe some changes occurred in their genetic structure and they lost the ability to transform so quickly? Or has the great diversity of species created intense interspecific competition, leaving too little room for experimentation? One thing is certain: nowadays, any vacated ecological niche is instantly filled by already existing animals, perfectly adapted to the given habitat.
Life in the Cambrian seas
The evolutionary explosion of the Early Cambrian produced a wide variety of creatures.
The most important of these are trilobites, arthropods similar in many ways to modern horseshoe crabs. Their bodies were covered with shield-like shells. Most early trilobites lived on the seabed, but some swam in the water above the surface of the bottom and, quite possibly, hunted their relatives who lived in the mud.
Many other organisms also lived in sea water.
They formed a food chain (a sequence of living beings that serve each other as food), which was based on millions of floating algae and microscopic animals.
Some of them, such as foraminifera and primitive shrimps, which appeared in the Precambrian, gradually developed hard covers.
Sea waves carried jellyfish and related animals from place to place, and by the end of the Cambrian period, very highly organized predators appeared in the seas - such as cephalopods (like modern octopuses and squids) or primitive armored fish.
Numerous worms swarmed in the bottom mud, feeding on carrion, primitive mollusks similar to modern limpets and sea snails, as well as brachiopods - animals with bivalve shells, something like bivalves on a stalk, which extract food from the surrounding water.
Whole forests of sea feathers swayed above the seabed, carefully filtering the water, and in quiet waters lived
fragile glassy sponges. By the end of the period, many different echinoderms had appeared, including starfish and sea urchins.
Two live lancelets
Change on the reefs
Predators were diligently destroying the ancient Pre-Cambrian stromatolite reefs, but new tireless limestone producers had already taken over the work.
These were archaeocyaths, primitive sponge-like organisms, which, however, quickly spread throughout the world and evolved into many different species. Archaeocyaths, in turn, suddenly declined and became completely extinct in the middle of the Cambrian, but by that time the first corals had appeared in the seas - although they had not yet begun to build reefs.
The end of the Cambrian was marked by a new ice age.
Sea levels have dropped sharply. This led to the destruction of many natural areas and, accordingly, the extinction of many animal species.
A Fossil chordate animal. They included a caudal fin with V-shaped muscle groups and a structure resembling the mouth part of a jawless fish, with teeth made of dentin and enamel, like those of vertebrates. Towards the end of the period, the first vertebrates, the so-called pteraspid fish, also appeared.
Fossil chordate
human tail
Among other things, in the Cambrian the first chordates appeared, representatives of the very group whose evolution ultimately led to the emergence of Man on Earth.
All chordates, at some stage of their development, have gill slits and a clearly defined neural tube running along the back, on both sides of which are paired muscle groups. Subsequently, a bony spine or spine is formed around the neural tube, which is why higher chordates are called vertebrates.
The part of such a ridge that extends behind the anus of the animal is called the tail. Chordates also have a tough cartilaginous string (notochord) that runs along the animal's back at some point in its life cycle. The notochord is still present in the embryos of vertebrates, including humans.
Three groups of early chordates are thought to have existed in the Cambrian.
All of them had a fish-like shape, and the dorsal neural tube turned into a long tail, driven by V-shaped muscle groups. Gill slits were located directly behind the head. Similar animals live on Earth today - these are tadpole-like larvae of ascidians and adult lancelets.
The first candidate for the ancestors of all chordates can be considered the small fish-like animal Pikaya from the Burgess shale. In appearance, it resembled a lancelet, with a long, hard stripe along the entire body and individual segments that looked like groups of muscles.
Anatomy of a trilobite
Trilobites great and terrible
Trilobites were the true masters of the Cambrian seas.
They burrowed into the sediment, crawled along the seabed, furrowed the dark ocean depths and swam in the upper layers of the seas, permeated with sunlight. Many of them ate the remains of dead animals and detritus that accumulated in bottom sediments, but there were also active predators among them. Some trilobites may have even hunted their relatives who lived in sea mud deposits.
The largest of the trilobites had a length of over 70 cm, and the smallest did not reach even a centimeter.
Trilobites looked similar in appearance to modern “king crabs” (horseshoe crabs) - their distant relatives. The name “trilobites” itself means “three-membered”: their shell consisted of three sections - a central, or axial, and two flattened lateral sections on both sides.
Most trilobites had a shield-shaped head, a flexible thorax (middle part) of articulated segments, and a flat tail, often elongated into a long caudal spine. Fossil trilobites are found curled up in a ball, like woodlice - perhaps this is how they protected themselves from enemies.
Each segment of the trilobite's body had a pair of limbs.
Those of them that were located near the mouth served as palpating antennae. On the other limbs, feathery gills for breathing, swimming plates or legs for walking, and special processes were attached, with the help of which food was transmitted along the body to the mouth. The shell was often covered with grooves and bulges that broke it into pieces.
Some trilobites have shells riddled with tiny holes, perhaps in places where hairs used to grow, serving as organs of touch or taste.
Types of trilobites
Shards of the past
Like other arthropods, trilobites had a hard outer covering that they periodically had to shed (as when molting) in order to grow.
The covers shed by trilobites are perfectly preserved in fossil form. However, to make shedding easier, their shells had weak lines, or seams. Buried under a layer of sediment, the shells of trilobites, as a rule, split along these lines, so that they are found extremely rarely in their entirety.
Investigating the "trilobite case"
How do we learn about the lifestyle of trilobites? For example, the remains of their mouth parts and front legs allow us to find out something about how they fed.
And yet, they swallowed the sediments along with the substances they contained. nutrients or ate detritus directly from the seabed? And how did they move? Did the predatory trilobites chase their prey or lay in wait in ambush?
Answers to some of these questions can be obtained by studying fossilized prints - traces left by trilobites as they moved along the seabed.
Making their way through the thickness of the silt, they left behind them a trail that looked like a “Christmas tree.” And when the trilobites rested, marks resembling hoof marks remained in the rock.
The first eyes on Earth?
Trilobites were the first animals known to us with highly developed vision.
Perhaps their vision helped them spot dangerous predators in time. Like the eyes of modern insects and crustaceans, the eyes of trilobites were complex and consisted of clusters of tiny lenses. These lenses turned out to be strong enough to survive in fossil form.
The sizes and shapes of trilobite eyes are extremely diverse.
There were also completely blind trilobites - perhaps because they lived in the thickness of bottom sediments or at great depths, where there is little light. Some trilobites had panoramic eyes that gave a wide view. Others had eyes on the sides of their heads. In still others, they were located at the very top of the head or even stuck out on stalks, so that the animals could probably bury themselves almost entirely in the mud, but at the same time keep a vigilant eye on possible threats or prey.
Trilobites active image life had bulging eyes in the front of the head. The fields of vision of both eyes crossed, which allowed the animal to more accurately determine the distance to the object and calculate its speed.
Swimming trilobites acquired wide and flat tail shields.
Such species had light shells and many processes that increased the surface of the animal’s body - this helped it stay afloat. Deep sea species trilobites used the appendages to lift themselves above the sediment, perhaps to extract food particles from seawater.
This fossilized imprint, called a cruciana, was left by a crawling trilobite.
Trilobite extinction
Trilobites reached their peak during the Ordovician period, but by the end of the Paleozoic era, 225 million years ago, they became completely extinct.
Rapidly evolved shellfish and fish learned to deal with them, despite their shells. In addition, they successfully competed with trilobites for food resources.
Chained in "armor"
Some trilobites could roll up in such a way that their strong “armor” completely covered the more vulnerable abdominal cavity.
The meaning of the CAMBRIAN PERIOD in the Encyclopedia of Biology
CAMBRIAN PERIOD
(Cambrian), the first period of the Paleozoic era. Lasted approx. 35 million years. It began 540 million years ago and ended 505 million years ago. In this period huge continent Gondwanaland, located in the equatorial region, and several smaller land masses (on the site of modern Siberia, China, Europe and North America) were bordered by vast shallow seas. The cool climate at the beginning of the Cambrian (a consequence of the glaciation at the end of the Vendian) and the enrichment of the atmosphere with oxygen apparently led to a phenomenon called the “Cambrian evolutionary explosion”. It was expressed in the rapid increase in the diversity of marine multicellular organisms, many of which acquired a mineralized cover (shell, shell, tube, etc.) - calcareous, phosphate, chitinous or flint. These are trilobites, coelenterates, mollusks, echinoderms, graptolites, jawless fish-like animals, etc. At the same time, a number of groups of animals arose, systematic position and family ties which remain unclear, similar in structure to arthropods, worms or crustaceans. Thus, all known types of animals appeared in the Cambrian, including chordates. In addition, quite a number of soft-bodied multicellular organisms with unclear family relationships with known types of animals continued to persist. Of the plants, the Cambrian is characterized by the appearance and wide distribution of lime-secreting algae, new reef-formers, together with archaeocyaths. The land was almost lifeless, populated only by bacteria and fungi, but by the end of the Cambrian the first worms and centipedes probably appeared. The richest and most famous localities of the Cambrian fauna are in Canada, Greenland, China and Russia (Aldan).
Encyclopedia Biology. 2012
See also interpretations, synonyms, meanings of the word and what the CAMBRIAN PERIOD is in Russian in dictionaries, encyclopedias and reference books:
- PERIOD in the Dictionary of Musical Terms:
(from Greek - detour, a certain circle of time) - a construction in which a more or less complete musical thought is presented. sometimes in... - PERIOD
MEDIUM TERM - see MEDIUM TERM... - PERIOD in the Dictionary of Economic Terms:
INTEREST - see INTEREST... - PERIOD in the Dictionary of Economic Terms:
TAX - see TAX PERIOD... - PERIOD in the Dictionary of Economic Terms:
GRACE - see GRACE PERIOD... - PERIOD in the Dictionary of Economic Terms:
GRACEFUL - see GRACEFUL... - PERIOD in the Dictionary of Economic Terms:
BUDGET - see BUDGET... - PERIOD in the Literary Encyclopedia:
[Greek periodos - “detour”, “circle”] - a term introduced by Aristotle to designate “speech that has in itself a beginning and an end and ... - PERIOD in the Big Encyclopedic Dictionary:
in music, see Musical... - PERIOD in the Encyclopedic Dictionary of Brockhaus and Euphron:
A period is a period of time after which known events return in the same order. In astronomy it is used to mean the time of revolution of the planet or ... - PERIOD in the Modern Encyclopedic Dictionary:
(from the Greek periodos - bypass, rotation, a certain circle of time), 1) a period of time covering any completed process. 2) Stage of social development, ... - PERIOD
[from Greek bypass, rotation] 1) a period of time covering any completed process; 2) in astronomy, the period of time during which ... - PERIOD in the Encyclopedic Dictionary:
a, m. 1. The period of time during which something happens (begins, develops and ends). P. flowering. Incubation stage of the disease. Periodization... - PERIOD in the Encyclopedic Dictionary:
, -a, m. 1. The period of time during which something. occurs (begins, develops and ends). Post-war p.P. heyday. Incubation… - PERIOD
HALF-LIFE of a radionuclide (T 1/2), the period of time during which the number of radioactive nuclei on average decreases ... - PERIOD in the Big Russian Encyclopedic Dictionary:
PERIOD OF OSCILLATIONS, name. the period of time after which the oscillating system returns to its original state. P.k. is the reciprocal of frequency... - PERIOD in the Big Russian Encyclopedic Dictionary:
PERIOD (geol.), large geological interval. time during which the forge was formed. rocks that make up the geol. system. P. are divided into geological. ... - PERIOD in the Big Russian Encyclopedic Dictionary:
PERIOD (music), see Musical form... - PERIOD in the Big Russian Encyclopedic Dictionary:
PERIOD, in poetics (especially in rhetoric), an expanded complex sentence with clear intonation and division into columns (example - everything ... - PERIOD in the Big Russian Encyclopedic Dictionary:
PERIOD (from the Greek periodos - detour, rotation, defined circle of time), a period of time covering a certain completed process. Society stage. development, society ... - PERIOD in the Complete Accented Paradigm according to Zaliznyak:
peri"od, peri"ode, peri"ode, peri"ode, peri"ode, peri"ode, peri"ode, peri"ode, peri"ode, peri"ode, peri"ode, ... - PERIOD in the Dictionary of Linguistic Terms:
(Greek periodos—detour, circle, rotation). A highly common simple or polynomial sentence difficult sentence, characterized in terms of content by significant completeness and... - PERIOD in the Dictionary for solving and composing scanwords:
One third of the hockey... - PERIOD in the Thesaurus of Russian Business Vocabulary:
- PERIOD in the New Dictionary of Foreign Words:
(gr. pertodos bypass, rotation) 1) the period of time during which something happens; 2) stage of social development, social movement; 3) … - PERIOD in the Dictionary of Foreign Expressions:
[ 1. the period of time during which something happens; 2. stage of social development, social movement; 3. astre, period of time, in ... - PERIOD in the Russian Language Thesaurus:
1. ‘a period of time during which any processes or events occur’ Syn: time, time, era, times, century, term, segment, interval; stage... - PERIOD in Abramov's Dictionary of Synonyms:
cm. … - CAMBRIAN in the New Explanatory Dictionary of the Russian Language by Efremova:
adj. 1) Correlative in meaning. with noun: Cambrian associated with it. 2) Characteristic of the Cambrian, characteristic of ... - CAMBRIAN in Lopatin's Dictionary of the Russian Language.
- CAMBRIAN in the Complete Spelling Dictionary of the Russian Language.
- CAMBRIAN in the Spelling Dictionary.
- PERIOD in Ozhegov’s Dictionary of the Russian Language:
period of a function In mathematics: a quantity, when added to the argument of a certain function, the value of the function does not change the period of time, in ... - PERIOD in Dahl's Dictionary:
husband. term or period of time, duration; time from one event to another. History is divided into periods and periods. The primordial period is... - PERIOD in Ushakov’s Explanatory Dictionary of the Russian Language:
period, m. (Greek periodos) (book). 1. A period of time during which something ends. repeating process (scientific). The synodic period of the planet's revolution... - CAMBRIAN in Ephraim's Explanatory Dictionary:
Cambrian adj. 1) Correlative in meaning. with noun: Cambrian associated with it. 2) Characteristic of the Cambrian, characteristic of ... - CAMBRIAN in the New Dictionary of the Russian Language by Efremova:
- CAMBRIAN in the Bolshoi Modern explanatory dictionary Russian language:
adj. 1. ratio with noun Cambrian associated with it 2. Characteristic of the Cambrian, characteristic of ...
According to official science, life on our planet originated about three billion years ago in the form of simple organisms - microscopic isolated rods, thread-like formations, spherical and polygonal unicellular algae. These organisms could only exist in water and only in warm climates.
In general, very few fossil remains from the Precambrian period have survived to this day. Evolution seems to have slowed down for three billion years since the origin of life, changing and improving only existing species of algae and microscopic organisms.
However, 580 million years ago, a turning point in the history of evolution came - the Cambrian period. Its duration within the life of the Earth is short - 80 million years. It was then that an amazing diversity of invertebrate species suddenly and almost simultaneously appeared. More importantly, living organisms were able to acquire a solid calcareous skeleton within a short time.
Multiple biological forms Cambrian became the predecessors of all species modern life, including humans. This sudden and sudden emergence of species diversity is known as the Cambrian Explosion.
The land at that time was an absolute desert, all life was concentrated only in water. The earth's continents had a completely different location: for example, in the place of Greenland and North America there was the Laurentian continent, and to the south there was the Brazilian continent. Arabia, Africa and Madagascar represented a single African continent; in the north was the Russian continent, separated by a deep strait from the Siberian and Chinese continents. In the south there was the gigantic Australian continent, which subsequently broke up into India, Australia and a number of islands.
During the Cambrian period, some modern mountains were formed: the Northern Appalachians, Sayan Chingiztau (Kazakhstan).
Life blossomed rapidly in the water: trilobites, radiolarians, sponges, and brachiopods arose and settled. Archaeocyaths appeared - multicellular animals that were a cross between a coral and a sponge. They attached themselves en masse to the bottom of reservoirs, forming a semblance of By the end of the Cambrian, they became extinct.
At this time, trilobites - primitive arthropods similar to modern woodlice - flourished especially. They had a flat, disc-shaped body with a chitinous shell divided into 45-50 segments and many legs.
Towards the end of the Cambrian, the first armored vertebrates, prototypes of fish, arose.
Thus, without any transitional connecting forms and intermediate species, from bacteria and protozoa, suddenly many invertebrate and vertebrate species, prototypes of modern forms, were formed on Earth. The Cambrian period represents a mysterious evolutionary leap in Earth's history.
Most often, scientists explain this revolutionary event by a critical accumulation of oxygen in the ocean in the air, as well as an increase in the washout of salts from land and an increase in the concentration of calcium and magnesium in the water. The chemical has changed so much that the organisms living there have had a lot of opportunities to change and form species.
It is also believed that around this time the Earth made a sudden revolution of almost 90 degrees, which caused a sharp displacement of all continents, tectonic shifts and the formation of the modern topography of the earth's surface. This also influenced the formation of new species and adaptations for survival.
Periods of the Earth's development were met with many catastrophes: for example, dinosaurs disappeared almost simultaneously and completely 65 million years ago. And in the Permian era, almost 95% of marine inhabitants died out at once in a short period - this was 245 million years ago.
But among all these mysteries, only the Cambrian period is distinguished by its creativity, and not the destruction of species. Opponents of the evolutionary approach see confirmation of Divine origin in the mystery of the Cambrian explosion modern species life, including humans.
