Sections of the site

Editor's Choice:

Advertising

home - Recipes

Write a classification of animals. Classification of animals. General information. Starfish class

, vol. 13. M., 1973, 1977, 1979 Hadorn E., Werner R..

General zoology

. M., 1989 In order not to get confused in all the diversity of animals that live and have lived on Earth, it is necessary to divide them into interconnected groups. In other words, animals need to be classified. Science deals with the classification of all living organisms and animals in particular. taxonomy of the living world

Despite the fact that the living nature of the Earth has already been well studied by man, new previously unknown species of animals continue to be discovered. Scientists and researchers describe a new species and then, in accordance with the classification of animals, assign it to one group or another.

Throughout human history, people in different countries have discovered and described animal species. They gave them names. Often the same species was called differently in different places. In order to prevent ambiguity in the classification of living organisms, in the 18th century C. Linnaeus introduced into science the so-called binary nomenclature. This is a way of giving species names consisting of two Latin words. The first word denotes the genus to which this species of animal belongs, and the second word specifies the species. For example, the red kangaroo is called Macropus rufus in Latin. Here the word Macropus is the Latin name of the genus of gigantic kangaroos, and the word rufus in combination with the first word unambiguously classifies the species.

Animal classification is designed to reflect the evolutionary and related relationships between groups of animals. Single-celled animals are grouped into the subkingdom Protozoa (although nowadays they are usually separated into a separate kingdom). In this subkingdom, the following types are distinguished: Ciliates, Sarcodidae, etc. Multicellular animals are classified as a separate subkingdom. Here the types are Coelenterates, Flatworms, Roundworms, Annelids, Molluscs, Arthropods, and Chordata.

In the phylum of chordates, the classes Cartilaginous fish and Bony fish, Amphibians, Reptiles, Birds and Mammals are distinguished.

The evolution of the animal world on Earth went from unicellular forms to multicellular ones, which subsequently developed complex organ systems (a skeleton, nervous system, etc. appeared). Birds and mammals have the most complex structure.

Groups of animals are not equal to each other in terms of the number of species and their role in nature. Therefore, in the study of zoology, it is common to consider individual classes of one type in more detail, while another type is considered in general. For example, the type of Ciliates is considered in detail, but not the individual classes of this type. While the classes belonging to the phylum Chordata are considered separately.

The science of classifying animals is called systematics or taxonomy. This science determines family relationships between organisms. The degree of relationship is not always determined by external similarity. For example, marsupial mice are very similar to ordinary mice, and tupayas are very similar to squirrels. However, these animals belong to different orders. But armadillos, anteaters and sloths, completely different from each other, are united into one squad. The fact is that family ties between animals are determined by their origin. By studying the skeletal structure and dental system of animals, scientists determine which animals are closest to each other, and paleontological finds of ancient extinct species of animals help to more accurately establish family ties between their descendants. Plays a major role in the taxonomy of animals genetics- the science of the laws of heredity.

The first mammals appeared on Earth about 200 million years ago, separating from animal-like reptiles. The historical path of development of the animal world is called evolution. During evolution, natural selection occurred - only those animals survived that were able to adapt to environmental conditions. Mammals have evolved in different directions, forming many species. It happened that animals that had a common ancestor at some stage began to live in different conditions and acquired different skills in the struggle for survival. Their appearance was transformed, and changes useful for the survival of the species were consolidated from generation to generation. Animals whose ancestors looked the same relatively recently began to differ greatly from each other over time. Conversely, species that had different ancestors and went through different evolutionary paths sometimes find themselves in the same conditions and, changing, become similar. Thus, species unrelated to each other acquire common features, and only science can trace their history.

Classification of the animal world

The living nature of the Earth is divided into five kingdoms: bacteria, protozoa, fungi, plants and animals. Kingdoms, in turn, are divided into types. Exists 10 types animals: sponges, bryozoans, flatworms, roundworms, annelids, coelenterates, arthropods, molluscs, echinoderms and chordates. Chordates are the most progressive type of animals. They are united by the presence of a notochord, the primary skeletal axis. The most highly developed chordates are grouped into the vertebrate subphylum. Their notochord is transformed into a spine.

Kingdoms

Types are divided into classes. Total exists 5 classes of vertebrates: fish, amphibians, birds, reptiles (reptiles) and mammals (animals). Mammals are the most highly organized animals of all vertebrates. What all mammals have in common is that they feed their young with milk.

The class of mammals is divided into subclasses: oviparous and viviparous. Oviparous mammals reproduce by laying eggs, like reptiles or birds, but feed their young with milk. Viviparous mammals are divided into infraclasses: marsupials and placentals. Marsupials give birth to underdeveloped young, which are carried to term in the mother's brood pouch for a long time. In placentals, the embryo develops in the mother's womb and is born already formed. Placental mammals have a special organ - the placenta, which carries out the exchange of substances between the maternal body and the embryo during intrauterine development. Marsupials and oviparous animals do not have a placenta.

Types of animals

Classes are divided into squads. Total exists 20 orders of mammals. In the oviparous subclass there is one order: monotremes, in the marsupial infraclass there is one order: marsupials, in the placental infraclass there are 18 orders: odontates, insectivores, woolly wings, chiropterans, primates, carnivores, pinnipeds, cetaceans, sirenians, proboscideans, hyraxes, aardvarks, artiodactyls, Callopods, lizards, rodents and lagomorphs.

Mammal class

Some scientists distinguish the independent order Tupaya from the order of primates, from the order of insectivores they separate the order Jumpers, and the predators and pinnipeds are combined into one order. Each order is divided into families, families into genera, and genera into species. In total, about 4,000 species of mammals currently live on earth. Each individual animal is called an individual.

The subject of the science of taxonomy is the classification of living organisms. Grouping creatures into groups based on certain characteristics has important practical significance for their study. The main systematic categories of animals and the principles underlying their classification will be discussed in our article.

Basics of Animal Classification

By what characteristic can animals be distinguished from the entire diversity of living organisms? According to the only method of nutrition. All animals, from the microscopic amoeba to the giant whale, are heterotrophs. This means that they feed only on ready-made organic substances and are not able to produce them on their own.

The smallest taxon of animals is a species. This is a group of individuals that are united on the basis of similarity in structure, physiology and ecology. This systematic category of animals has a double name. It was first introduced into science by the famous scientist Carl Linnaeus. May beetle, polar owl - the first name is specific. The second word determines the genus to which the animal belongs.

Systematic categories of animals: table

Systematic units are also called taxa. Species and genus are the least of these. The largest taxon is the kingdom. At the present stage of taxonomy, there are five of them. These are plants, fungi, bacteria, viruses and animals. Their main difference is the method of nutrition and the structural features of the cell. The sequence of systematic categories of animals is given in our table.

Unicellular

The systematic category of animals that are protozoa includes single-celled organisms. All of them are eukaryotes. Their cell is a complete organism capable of carrying out all life processes: nutrition, respiration, growth, reproduction, movement.

Typical examples of animals that belong to the subkingdom of unicellular organisms are green euglena and slipper ciliates.

Multicellular

The body of representatives of this systematic unit is not simply formed by many cells. These are the smallest structures, similar in structure and function, which are sequentially combined into tissues, organs and their systems. This systematic category of animals includes several types, the structure of which progressively becomes more complex. There are seven of them in total. The most primitive in structure are sponges. These organisms lead an attached lifestyle, feeding by filtering. Freshwater hydra, jellyfish and polyps are representatives. They have specialized cells that do not yet form true tissues.

These structures first appear in worms, which form several types of animals: flat, round and annelid. Moreover, the latter are characterized by the appearance of the circulatory system. The next type of multicellular animals is called molluscs. They have a soft body that is not divided into segments and is often protected by a shell. The largest species diversity is the phylum of arthropods, which includes insects, crustaceans and arachnids.

Chordata

This systematic category of animals is the most complex in structure and has a general structural plan. This is the presence of an axial cord, or chord, neural tube and gill slits in the pharynx. They vary depending on their habitat. Representatives of the chordate classes are known to everyone and are widely used by humans in economic activities. These include typical aquatic inhabitants - fish, which are characterized by gill breathing. Amphibians live on land and breed in bodies of water. These are frogs, toads and tree frogs. Reptiles come completely onto land - crocodiles, lizards, snakes, turtles. And birds have conquered the air habitat. The most highly organized animals of the chordate type are mammals, of which humans are representatives.

The world is full of mysterious creatures; they constantly surprise humanity. There are many species of animals that amaze with their uniqueness.

Classification

There are the following groups of animals:

Mammals.
Mollusks, echinoderms.
Fish, lancelets, cyclostomes.
Birds.
Reptiles.
Amphibians.
Arthropods.

Many animals have become dear to man, since he cannot imagine his life without them. But there are wild creatures that people will never be able to tame. By the way, the first animal that man subjugated was the wolf. This happened about 15 thousand years ago. He became domesticated and eventually evolved into a dog. Now it is man's best friend.

How to determine the group of an animal?

Different creatures are assigned a specific group. The animal world is diverse, so each classification has its own characteristics. Namely:

Mammals include warm-blooded animals. They are covered with fur, have a four-chambered heart, and mammary glands that secrete milk. When they give birth, they have a live baby.
Birds - which lay eggs. They are covered with feathers, have wings, and have a four-chambered heart.
Reptiles are cold-blooded animals. Their body is covered with scales and they lay eggs.
Amphibians are also cold-blooded. They have a three-chambered heart, they breathe using their skin, and their larvae live in water. Water can penetrate through the shell of the egg.
Chordates include some fish-like organisms in their list.

Varieties of living beings depending on the food consumed

Animals can be divided into groups according to their feeding method. There are herbivorous living beings. They feed on leaves, seeds, fruits, roots, etc. Their oral apparatus has its own characteristics: they have more horny plates or incisors, molars. Nature has thus created a device for grinding food of plant origin. But aphids, bugs, and cicadas have a sucking apparatus, which gives them the opportunity to feed on plant juices. Additional sections are developed in the gastrointestinal tract, such as the rumen. They allow the processing of fiber. Herbivorous mammals have peripheral vision. Such animals have muscles that are quite coarse and not as developed as those of predators of the same group.

There are predatory animals that feed on other creatures. They have the skills to attack the victim. Among all teeth, canines are considered the most developed; this difference is observed in mammals. A crocodile has an elongated mouth, while a shark has a number of rows of teeth directed inward. Birds of prey have developed and sharp claws. Carnivorous mammals have good visual acuity. Carnivores attack their prey in a special way: they wait and make a sharp jerk. They are resilient, have precise coordination, and are very fast.

The starfish destroys the enemy in a special way. She crawls onto the mussel, waits for the valves to open, and then injects enzymes into the shell.

But woodpeckers eat insect larvae that live under the bark of trees. To do this, they have a strong large beak, special paws with which the birds firmly hold onto each creature. Nature has created certain devices with which they can obtain food.

There are groups of animals that feed on the remains of organisms. A striking example would be scavenger birds. They have a long neck, a narrow muzzle, and a good sense of smell. But, for example, the food of fly larvae is the organic remains of plants and animals.

round and flatworms;
insects such as fleas, mosquitoes, bedbugs, mosquitoes, lice, midges;
mites;
crustaceans;
cyclostomes.

There are also groups of animals according to their feeding method, which eat food of plant and animal origin. They are called omnivores. They are endowed with features that resemble both predators and herbivores. Such animals are bears, crickets, and rats. Reptiles include geckos, agama and other reptiles. Humans are also included in this group.

Interesting information about animals from different groups

There are some facts that amaze many people:

The giraffe has the largest heart. This animal has a length of up to 45 cm.
The bones of the gar fish are green.
The cat is unable to move its jaws.
The heartbeat of a whale is 9 beats per minute.
The octopus has rectangular pupils.
A record-breaking flight of a chicken was recorded. It is 13 seconds.
Caterpillar muscles predominate in number over human muscles.
A female armadillo can extend pregnancy up to 2 years if she is stressed.
A tit sometimes feeds its young a thousand times a day.

Groups of dangerous animals

All entities in the world can be classified according to other criteria. For example, there are groups of animals that are dangerous to human life. At first glance, they may seem harmless. Such an animal is the mosquito. He is a carrier of malaria. The insect transmits the infection through the blood. About 2 million people die every year from the bites of these animals.

The Australian jellyfish joins the list of dangerous living creatures. She has very long tentacles that reach up to 4 meters. Their number is 60 pieces. At the same time, a jellyfish can kill 60 people. And many other animals pose a danger to humans.

conclusions

So, it is not difficult to determine which group of animals a particular creature belongs to. The main thing is to know by what criteria the grouping occurs. After all, animals are divided by place of residence, method of feeding, classes, species and other factors. Each living creature is adapted to its habitat, has its own characteristics, and eats different foods.

SYSTEMATICS OF ANIMALS, also called animal taxonomy, a branch of zoology that deals with assigning scientific names to animals, describing their species, and distributing (classifying) the latter into natural groups based on family (evolutionary) relationships. The terms “systematics” and “taxonomy” are often used interchangeably, but it is still useful to distinguish between them.

Taxonomy, unlike taxonomy, emphasizes the theory and methodology of classification. Its purpose is to divide animals into groups (taxa) and arrange these groups in an order reflecting their related relationships and hierarchy (from lower to higher, i.e. from species to genera, families, etc.) based on the degree of similarity and differences between them. There are several methods for determining the relative position of a group in a system. For example, the method known as cladistic constructs branching patterns that take into account the number of common characters and their adaptive role; the phylogenetic method establishes family relationships based on data from comparative anatomy and paleontology.

Unlike taxonomy, taxonomy gives names to animals, and interprets and evaluates the similarities and differences between them, used in identifying taxonomic groups; in other words, the task of taxonomy is to study the diversity of living forms. Thus, it is a broader concept that includes part or all of the taxonomy.

In the scientific classification system, each animal species receives a standard Latin name consisting of two words (binomen). This eliminates the confusion that is inevitable when using a variety of traditional, i.e. "folk" names.

HISTORY OF CLASSIFICATION Ancient Greek systems. It can be considered that the foundations of classification were laid by the Greek philosopher Plato, who created the doctrine of “ideas”. Aristotle, one of Plato's students, made an attempt to distribute animals into groups based on their correspondence to one or another “idea” embodied in a set of characteristics. Without creating a full-fledged classification system, he introduced two important taxonomic categories into use: “species”, i.e. a collection of almost identical forms, and a “family” group of similar species. Nevertheless, his works were widely used by subsequent generations of taxonomists.Early period of modern taxonomy. Still at 16 V. such prominent scientists as E. Wotton and K. Gesner continued to be content with the most primitive systems of living things. However, Wotton's critical attitude towards species clearly invented by ancient authors introduced a fresh stream into this area of \u200b\u200bknowledge, which influenced Gesner. In addition to numerous articles, Gesner published his classic Animal history (Historia animalium ), where he distributed them alphabetically, combining related forms into groups. Each species was described quite accurately for the time, and all the material was presented with encyclopedic care. However, despite discussing many different issues, Gesner did not make comparisons between groups and did not address functional aspects at all. At the same time, he included his original observations in the text, which most of his predecessors did not do, and demonstrated how useful it is to supplement descriptions with drawings.

Ulysses Aldrovandi published 14 large volumes on animals, showing that some of their large groups can be divided into subgroups, and including data on the internal structure of organisms in the descriptions. In the 16th century P. Belon was the first to use comparative anatomy for classification. One of the outstanding biologists of the 17th century. was D. Ray. Among his works, mostly related to botany, there were several zoological studies that contained an in-depth analysis of the functional relationships between animals. Rey clearly established the distinction between genus and species and formulated the concept of similar characters as the basis for identifying relationships between natural groups. The works of J. Buffon, published in the mid-18th century, played an important role in the development of taxonomy. His theories, for all their shortcomings, turned out to be very useful for biologists of subsequent generations. Buffon showed that many difficulties in taxonomy arise from the external similarity of animals that are distant from each other, but it is precisely this that makes it possible to identify more general patterns of natural history.

The beginning of modern taxonomy was laid System of nature

(Systema Naturae ) Carl Linnaeus. Its tenth edition, published in 1758, established a hierarchy of taxonomic categories such as phylum, class, order, genus and species. We still use not only the binomial nomenclature created by Linnaeus, but also many of the scientific names he introduced. Not all of the 4,000 animal species he described continue to remain in the groups in which he placed them, but the groups themselves have survived. Linnaeus indicated the natural unit species as the starting point of classification, but, following Ray and his other predecessors, he considered species unchanged. Only in the 19th century, after the emergence of the evolutionary theories of Jean Lamarck and Charles Darwin, the concept of the historical transformation of living forms was established. This evolutionary doctrine and the discovery at about the same time of the basic laws of heredity formulated by Gregor Mendel served as the basis for the transformation of systematics into a real science.New taxonomy. The modern classification system, using many of the ideas and methods that emerged in the 19th century, goes much further, relying on constantly accumulating new information. Currently, the characteristics of not individual individuals, but entire populations of organisms are being systematized. A quantitative approach was added to the subjective qualitative study. Experts do not limit themselves to analyzing differences and similarities, but try to create a unified natural system. It has long been recognized that populations change and that changes that occur can be perpetuated through reproductive isolation. Accordingly, the main attention is paid to such problems as the “rate and direction” of changes (evolution) of organisms; speciation, i.e. the origin of species from ancestral forms; family ties between groups.Terminology. Since classification was carried out by hundreds of taxonomists, working both on the same and on different materials, it became necessary to establish certain rules and terminology. The largest groups (taxa) into which the animal kingdom is now divided are called phyla. Each type is divided successively into classes, orders, families, genera and species (sometimes intermediate categories are also distinguished, for example subtypes, superfamilies, etc.). As we move from the highest to the lowest hierarchical group, the degree of relatedness between animals belonging to the same taxon increases. Within the same species, all animals are very similar in characteristics and, when crossed, produce fertile offspring. The table below illustrates this classification system with several examples.

Type	Chordata	Chordata	Chordata	Chordata
Subtype	Vertebrates	Vertebrates	Vertebrates	Vertebrates
Class	Bony fish	Amphibians	Mammals	Mammals
Squad	Herring	Anurans	Predatory	Primates
Family	Salmonidae	Frogidae	Felines	Hominids
Genus	Trout	Real frogs	Cats	People
View	Brook trout	Leopard frog	Domestic cat	Homo sapiens
Scientific name	Salmo trutta	Rana pipiens	Felis catus	Homo sapiens

All four species belong to the same type and subtype, since they have an important common feature - a spine consisting of movably articulated vertebrae. Cat and man belong to the same class; their relationship is evidenced by the presence in both cases of hair and mammary glands in females. The frog and the fish belong to different classes; the fish has gills and a two-chambered heart, while the frog has lungs and a three-chambered heart. Cats, with their claws on their fingers and a pair of large cheek teeth of a cutting type, represent the order of carnivores, and humans represent the order of primates, because instead of claws, he has nails, and his thumbs are opposed to the rest. In all four examples, the scientific name of the animal is composed of two Latin words: the generic name (with a capital letter) and the specific epithet; in any part of the globe Salmo trutta , for example, means the same specific biological species.Classification rules. The procedure for naming animals is regulated by certain international rules. For species described after 1758, the name proposed by the author of the description is considered priority; it is this name that all others must use; all names used by Linnaeus are also given priority (if they correspond to the modern distribution of organisms by taxonomic groups). Two species cannot have the same name. When describing a new species, it is necessary to select and preserve in one form or another one or more of its “type” specimens, indicating the place where they were found. There are also rules about the languages that can be used for names, and about the grammatical construction of the latter (for example, their “Romanization” is required, although the use of Greek roots is acceptable). Such general rules did not always exist: Linnaeus and other scientists used their own, which led to confusion. A number of countries tried to develop national codes of biological nomenclature, for example in Great Britain (Strickland Code, 1842), USA (Dall Code, 1877), France (1881) and Germany (1894). Finally everyone realized that classification was an international problem. In 1901, the International Rules of Zoological Nomenclature (International Code) were adopted. There is an International Commission on Zoological Nomenclature, whose functions include recommending amendments and additions to the Rules, interpreting them, compiling lists of clarified names and resolving controversial issues of classification. BASIC SIGNS OF ANIMALS Despite significant differences between animal types, many of them share some fundamental characteristics that can be used to identify distant relationships. However, these similarities, for example, characteristics of growth and embryonic development, cannot be considered absolute. On the one hand, they may be characteristic not only of a given large group, and on the other hand, they may not be found in all of its representatives; in addition, they are expressed to varying degrees or not at all stages of development. Therefore, many zoologists do not consider them particularly significant. Nevertheless, such characters generally help to understand the origin and evolution of animal types and to develop a classification that most accurately reflects their relationships.Symmetry. One of the most important features of an organism is the symmetry of its structure. If a body can be divided into at least two identical or mirror-like parts, it is called symmetrical. Animals are characterized by two types of symmetry: bilateral (bilateral) and radiant (radial); neither one nor the other is found in its pure form. Sponges, cnidarians and ctenophores are radially symmetrical, i.e. their general shape is cylindrical or disc-shaped, with a central axis. More than two planes can be drawn through this axis, dividing the body into two identical or mirror parts. Animals of all other types are bilaterally symmetrical: the anterior (head) and posterior (tail) ends, as well as the lower (abdominal) and upper (dorsal) sides are clearly visible; as a result, the body can only be divided lengthwise into two mirror halves - right and left. It may seem that some types of animals (for example, echinoderms) are mistakenly classified as bilaterally symmetrical because their symmetry appears to be radial. However, it is secondary in origin: their ancestors had bilateral symmetry, which can be found in the larval stages of modern forms.Egg crushing. Another fundamental feature is the nature of egg fragmentation during the formation of the embryo. Despite the complexity and diversity of this process in different groups, two main types can be distinguished: radial and spiral.

The polar axis of an egg is an imaginary line running from its “north pole” (top) to its “south” (base). The radial crushing furrows run either perpendicular or parallel to this axis. As a result, a cluster of cells is formed, located radially and symmetrically relative to it (like slices in an orange).

The furrows of spiral cleavage pass at a different angle to the polar axis, so the emerging daughter cells are located “obliquely” slightly above and below the mother one from which they were formed, and form spirals as part of the developing embryo.

With radial and spiral fragmentation, the timing of determining the future “fate” of the cells usually differs, i.e. what tissue will ultimately develop from one or another group of them. If this occurs only at a relatively late stage of development, then by dividing a four-cell embryo (for example, a starfish) into separate cells under experimental conditions, each of them can be grown into a whole individual. This development is called regulatory; it is usually associated with the radial type of crushing. Conversely, if the fate of the cells is determined very early, then the experimental division of a four-cell embryo (for example, a ring) will lead to the formation of only four of its “quarters”. This development is called mosaic; it is characteristic of spiral crushing.

Gastrulation. The early embryo resulting from cleavage is essentially a spherical clump of cells called a blastula (cm. EMBRYOLOGY). During further development, it becomes two-layered; more precisely, the process of gastrulation turns it into a gastrula. Gastrulation occurs differently depending on the type of blastula.

This process is especially clearly expressed in animals with a hollow blastula (for example, starfish): during the so-called. Invagination, a certain part of it is screwed inward and forms a pocket-like cavity. The pocket wall becomes the inner layer located under the original outer layer. For clarity, imagine a weakly inflated ball that you pressed with your finger; under it there will be two layers of rubber.

Germ layers. The two layers of cells formed as a result of gastrulation are called germ layers: the outer ectoderm, the inner endoderm. Subsequently, a third layer, the mesoderm, is formed between them. It comes in two main types: mesenchymal (a loose mass of cells embedded in a gelatinous substance) and sheet-like (resembling epithelial tissue). In sponges, cnidarians and ctenophores, the mesoderm is mesenchymal, arising from ectoderm cells. In all other types of animals it is either mesenchymal or sheet-like and is formed from the endoderm.

Each germ layer gives rise to certain tissues and organs of the adult organism; Thus, in vertebrates, the central nervous system and receptors of sensory organs (for example, eyes) are ectoderm derivatives, muscles and the circulatory system are mesoderm, and the liver, pancreas and thyroid glands are endoderm.

Class oligochaetes (Oligochaeta, from Greek oligos little, chaete hair). These worms, which also include earthworms, live in water or damp soil. Their body segmentation is well expressed both inside and outside. There is no head or parapodia, but each segment usually bears several pairs of setae. In most species, respiration is cutaneous and there are no gills. Although oligochaetes are hermaphrodites, they do mate. The eggs are fertilized and laid in a cocoon of mucus secreted by the so-called glandular cells. belt on the body. Approximately 3,000 species have been described.Leech class(Hirudinea, from Latin hirudo leech). These worms live in water or damp places on land. The body is flattened. The large posterior sucker serves for attachment; sometimes there is a second front sucker. Tentacles, parapodia, and usually bristles are absent. Hermaphrodites, but mating occurs. From eggs surrounded by a cocoon, adult individuals develop, bypassing the larval stage.

Approximately 100 species are known. The length of most of them is from 10 to 85 cm, and the diameter usually does not exceed 2 mm. Depending on the species (only three exceptions are known), the head section (protosome) bears from one to more than 250 tentacles, forming something like a beard, which explains the scientific name of the group.

Due to the presence of many similarities with both annelids and arthropods, onychophorans are often called the link between these groups. Like ringlets, they have a segmented body with a soft wall, unsegmented appendages, paired nephridia (excretory tubes) in each segment and an unbranched digestive tract. They are similar to arthropods by tracheal breathing and reduction of the coelom: the space between the internal organs is occupied by the hemocoel, i.e. a large cavity filled with blood (open circulatory system).

Onychophorans are divided into two families with nine genera, the best known of which is peripatus (

Peripatus ). Approximately 75 species have been described.Phylum arthropod (Arthropoda, from Greek arthron joint, pus, podos leg). This is the largest group of animals, uniting, according to various estimates, 1.52 million modern and fossil forms. One of the main features that distinguishes it from all more primitive invertebrates is the articulated structure of the limbs. The segmented body consists of a head, thorax and abdomen. Initially, each segment bears a pair of articulated appendages. The external skeleton (exoskeleton) is represented by a dense cuticle; Its strength is given by chitin, an aminopolysaccharide similar in physical properties to horn. The exoskeleton is very weakly extensible, so body growth requires periodic molting, during which the old cover is shed and a new, more spacious one is secreted to replace it. The digestive tract is usually through. The coelom is greatly reduced, and most of the body is occupied by a blood-filled cavity called the hemocoel (an open circulatory system). The nervous system, as well as simple and compound eyes, antennae and other sensory organs are usually well developed.

Arthropods are characterized by dioeciousness and internal fertilization. In some species, eggs develop without fertilization (parthenogenesis). The type is divided into 9 classes.

Class arachnids (Arachnida, from Greek arachne spider). This group includes, among others, spiders, scorpions and ticks; all of them can be easily distinguished from other arthropods by their 4 pairs of legs; the cephalic and thoracic segments are fused together to form the cephalothorax. There are no antennae or real jaws. The first two pairs of modified limbs - chelicerae and pedipalps (lit. tentacles), and sometimes the first segments of walking legs - make it possible to grasp and grind food; When feeding, the animal sucks out only the liquid part of the food. The male is usually smaller than the female; most species are oviparous.Class Merostomaceae (Merostomata, from Greek meros part, stoma mouth). The oldest marine arthropods. Only 3 genera of horseshoe crabs have survived to this day. The body consists of a fused cephalothorax, covered with a horseshoe-shaped dorsal shield, and an unsegmented abdomen.Type bristle-jawed (Chaetognatha, from Greek chaete hair, gnathos jaw). Approximately 115 species of so-called. naval shooters, most of which stay near the surface of the ocean. The type received its name because of the bristles bordering their mouth. The body is translucent, arrow-shaped, non-segmented, without ciliated cover, from 5 mm to 10 cm in length. Other characteristic features: the presence of a head, trunk and caudal sections; through the digestive tract; nervous system with ganglion-bearing peripharyngeal ring, abdominal ganglion and sensory organs. The respiratory, excretory and circulatory systems are absent. Hermaphrodites with internal fertilization; the ovaries are located in the trunk region, the testes in the caudal region.

The phylogenetic relationships of chaetognaths are not entirely clear, since strongly pronounced adaptations to a predatory lifestyle among plankton mask their relationship with other groups. These are probably highly specialized pseudocoelomic animals, and not degenerated secondary cavities, as some researchers believe.

Sea lily class (Crinoidea, from Greek krinon lily). This class unites all living sessile echinoderms (subphylum Pelmatozoa ). Their movable rays, or arms, surround the superior oral surface of the body; resembling the long petals of a flower, they give the animal a plant-like appearance. An attachment stalk often extends from below, which appears segmented, because skeletal plates form rings in it. This group is very ancient, existing back in the Cambrian, i.e. 570510 million years ago. Extinct species approx. 5000, and modern ones are less than 700.Class sea urchins (Echinoidea, from Greek echinos hedgehog). The body is usually hemispherical or disc-shaped, protected by a solid shell (“shell”) of skeletal plates welded together and covered with movable needles, firmly attached to the shell with their bases. The mouth contains five strong teeth that make up the chewing apparatus (Aristotle's lantern). All animals are dioecious; have 45 gonads; external fertilization. Sometimes, especially in cold seas, the juveniles develop in special pouches on the female’s body. Approximately 2000 species are known.Type hemichordate (Hemichordata, from Greek hemi half, chorde string). Worm-like soft-bodied animals that live at the bottom of the sea. The length of some species reaches 2 m. The body consists of a proboscis, a short collar and an elongated torso. Paired gill slits on the anterior part of the latter and the dorsal nerve trunk indicate proximity to chordates, but their third main feature, the notochord, is missing. The similarity of the larvae covered with cilia - tornaria in hemichordates and bipinnaria in echinoderms - allows us to consider hemichordates as an intermediate link between echinoderms and chordates. There are two classes, including approx. 100 species.Class enteric-breathing (Enteropneusta, from Greek enteron intestine, pneuma breathing). Mobile bottom animals. Dioecious, but one species is also capable of asexual reproduction by transverse division of the body.Class pterobranchs (Pterobranchia, from Greek pteron wing, branchia gills). Sessile, usually colonial forms. Arms with numerous small tentacles extend from the collar.Phylum Chordata(Chordata, from Greek chorde string). These secondary cavities are characterized by three main features: 1) a dorsal nerve trunk in the form of a tube; 2) chord, which serves as the axial internal skeleton (endoskeleton); 3) the presence of gill slits at least in the early life stage. The fourth important sign is the heart located on the ventral side of the body. There are three (sometimes four) subtypes.Subphylum larval chordates, or tunicates (Urochordata, from Greek ura tail, chorde string), or Tunicata (from Latin tunica clothing such as a shirt). Marine animals with a diameter from 1 mm to 40 cm; single or colonial. Some species and all larval stages are free-swimming, but sessile forms are also known. All of them have a body covered with a thick transparent gelatinous membrane called a tunic. Hermaphrodites; Reproduction is sexual or asexual, by budding. There are three classes.Appendicular class (Appendicularia, from Latin appendicula clause). Free-swimming forms, from 0.3 to 8 cm long, retaining a tail in adulthood; hermaphrodites, reproduction is only sexual; development is direct (no larval stage). Also called Larvacea. Ascidian class(Ascidiacea, from Greek askidion pouch). Solitary and colonial sessile in adult form; in the latter case with a common tunic. Reproduction, both sexual and asexual, by external budding or the formation of gemmules (internal buds).Class pelagic tunicates (Thaliacea, from Greek thaleia flowering). Free-floating forms. The barrel-shaped body is surrounded by circular muscles; contracting, they push the water entering the body from its rear end, providing forward movement. They reproduce both sexually and by budding, in which one adult animal sometimes forms a chain of developing individuals trailing behind it.Subphylum cephalochordates (Cephalochordata, from Greek kefale head, chorde string). Representatives of this genus, lancelets, live in sand in the shallow waters of warm seas. The body is lanceolate with one dorsal and two fin folds located on the sides of the ventral side; tail behind the anus. Body length up to 10 cm. Dioecious creatures.Subphylum vertebrates (Vertebrata, from Latin vertere twirl). Vertebrates differ from other chordates in two ways: 1) in most, the notochord is replaced by a segmented (jointed) bone structure called the spine; 2) the brain is protected by a bony cranium, which is why vertebrates are often called cranial ( Craniata ), contrasting with tunicates and cephalochordates. These are, as a rule, large dioecious animals. They are divided into 7 classes.Class Cyclostomes (Cyclostomata, from Greek kyklos circle, stoma mouth). These animals, which include hagfishes and lampreys, are the most primitive vertebrates. They are closely related to the scutes ( Ostracodermi ) Devonian period (408362 million years ago), sometimes called the Age of Pisces; these two groups are combined into the superclass of agnathans ( Agnatha ), contrasting with all other vertebrates gnathostomes ( Gnathostomata ). Cyclostomes have neither jaws nor paired fins. The mouth is in the form of a funnel-shaped sucker with horny teeth for scraping the soft tissues of the animals on which they feed. The body is soft, cylindrical, without scales, covered with mucus; On top of the head there is an unpaired (median) nostril. The heart is two-chambered; cranial nerves 810 pairs; the notochord persists throughout life.Class cartilaginous fish (Chondrichthyes, from Greek chondros cartilage, ichthys fish). Usually these are marine predators: sharks, rays and chimeras. The length of some species reaches 15 m. The skeleton is cartilaginous. The notochord persists throughout life. As a rule, a caudal and paired ventral and pectoral fins are present. The mouth is almost always located on the ventral side. It is armed with jaws with teeth covered with enamel; 57 pairs of gill slits, two-chambered heart; cranial nerves 10 pairs; two nostrils in front of the mouth; in the lumen of the intestine along its entire length stretches the so-called. spiral valve fold that increases the suction area. Tooth-like (placoid) scales make the skin rough.

Cartilaginous fishes are possibly closely related to extinct armored fishes (

Placoderm ). Sharks and rays are classified into the subclass elasmobranchs ( Elasmobranchii ), contrasting with whole-headed ( Holocephali), i.e. chimeras. Class bony fish (Osteichthyes, from Greek osteon bone, ichthys fish). The skeleton is usually bony; most species have thin, flattened scales. The mouth is usually at the anterior end of the body, with well-developed jaws and teeth. The heart is two-chambered. The gills are attached to the gill arches in the lateral gill cavities, covered by a hard operculum. Most species have a swim bladder. There are 10 pairs of cranial nerves.

The sizes are very diverse - from 1 cm to 7 m. This class includes trout, catfish, perch and most other fish inhabiting the waters of the planet. Approximately 25,000 species are known.

class amphibians, or amphibians(Amphibia, from Greek amphi double, bios life). Amphibians, which include frogs, toads, salamanders and caecilians, were the first vertebrates with four legs for movement on land (sometimes the legs were lost a second time), and the first to have true lungs that allowed them to breathe air. These are cold-blooded (ectothermic) forms, i.e. their body temperature depends on environmental conditions (like all animals except birds and mammals). The skin is bare, more or less moist, involved in respiration. The heart is three-chambered, consisting of two atria and a ventricle; cranial nerves 10 pairs. With very few exceptions, they are oviparous, with larvae developing in water, and therefore live, as a rule, in damp places near water bodies.class reptiles, or reptiles(Reptilia, from Latin repere crawl). These animals include (in order of complexity of organization) turtles, lizards, snakes and crocodiles. They were the first to fully adapt to life on land: in addition to legs and lungs, they are characterized by: internal fertilization; eggs protected from drying out by a calcareous or leathery shell; dry skin covered with horny scales. There are 12 pairs of cranial nerves. The heart is usually three-chambered (but with a ventricle separated by an incomplete septum), but in crocodiles it is four-chambered, with two atria and two ventricles. During development, special embryonic membranes are formed: amnion, chorion and allantois, therefore reptiles are classified as amniotes, in contrast to the vertebrates discussed above, called anamnias. Modern reptiles are much inferior in size and diversity to their relatives who lived in the Mesozoic era (from 245 to 65 million years ago), which is called the Age of Reptiles.Bird class(Aves, from Latin avis bird). These animals differ from all others by the presence of feathers. They are warm-blooded (endothermic), i.e. body temperature is almost constant regardless of environmental conditions. The front pair of limbs are transformed into wings, although in some species the ability to fly is secondarily lost. Bones are light and usually hollow. There are no teeth, although fossil forms had them. In adult birds, only the right aortic arch is preserved; four-chambered heart; The respiratory organs are the lungs, connected to air sacs located throughout the body. There are 12 pairs of cranial nerves. Fertilization is internal, but there is usually no copulatory organ; all oviparous. The embryonic membranes are the same as those of reptiles (amniotes); lime eggshell. Sizes vary from hummingbirds weighing approx. 3 g to ostriches weighing 130140 kg. Many species are domesticated, and poultry farming constitutes an important branch of agricultural production.Class mammals or animals (Mammalia, from Latin mamma female breast). The characteristic features of these animals are hair (coat) and mammary glands, which serve to feed the offspring. The four limbs are differently specialized depending on the function they perform. Most species have auricles and teeth differentiated into several groups. The respiratory organs are only the lungs, the ventilation of which is facilitated by the diaphragm (the muscular partition between the chest and abdominal cavities). All species are warm-blooded. Heart four-chambered heart; In the adult body, only the left aortic arch is preserved. There are 12 pairs of cranial nerves. Fertilization is internal, using the copulatory organ (penis). The embryonic membranes are characteristic of amniotes, and the yolk sac is usually vestigial, because the vast majority of species (except for monotremes - platypus, echidna and proechidna) are viviparous. Mammals vary greatly in size: from shrews weighing 1.5 g, to whales over 30 m long and weighing up to 120 tons. The number of modern species is 4000. see also COMPARATIVE ANATOMY; HUMAN ANATOMY; BIOLOGY; AMPHIBIANS; COELENTERATES; CORAL; MAMMALS; SHELLFISH;INSECTS; PALEONTOLOGY; REPTIENTS; PROTOZOTS; BIRDS; CRUSTACEANS; FISH; ARTHOPODS;
LITERATURE Sokolov V.B. Mammal taxonomy

Read:

General Director Astakhov I How to freeze porcini mushrooms for the winter: raw, boiled, fried How to prepare porcini mushrooms at home Structure of the hand and wrist Honey mushroom soup is simple and healthy! The structure and atmosphere of the Sun