Comparative anatomy and morphology of animals in the first third of the 19th century. Comparative anatomy What comparative anatomy studies

And organ systems by comparing them in animals of different taxa at different stages of embryogenesis.

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Literature [ | ]

• Shimkevich V.M., Course of comparative anatomy of vertebrate animals, 3rd ed., M. - P., 1922;
• Dogel V. A., Comparative anatomy of invertebrates, L., parts 1-2, 1938-40;
• Shmalgauzen I.I., Fundamentals of comparative anatomy of vertebrate animals, 4th ed., M., 1947;
• Severtsov A.N., Morphological patterns of evolution. Collection Op. , vol. 5, M. - L., 1949;
• Blyakher L. Ya., Essay on the history of animal morphology, M., 1962;
• Beklemishev V.N., Fundamentals of comparative anatomy of invertebrates, 3rd ed., parts 1-2, M., 1964;
• Development of biology in the USSR, M., 1967;
• Ivanov A.V., Origin of multicellular animals, Leningrad, 1968;
• History of biology from ancient times to the present day, M., 1972;
• Bronn's Klassen und Ordnungen des Thierreichs, Bd I - ,Lpz., 1859-;
• Gegenbaur C., Grundriss der vergleichenden Anatomie, 2 Aufl., Lpz., 1878;
• Lang A., Lehrbuch der vergleichenden Anatomie der wirbellosen Thiere, Bd 1-4, Jena, 1913-21;
• Handbuchder Zoologie, gegr. von W. Kukenthal, Bd I - ,B. - Lpz., 1923-;
• Handbuch der vergleichenden Anatomie der Wirbelthiere, Bd 1-6, V. - W., 1931-39;
• Traite de zoologie, publ, par P.P. Grasse, t. 1-17, P., 1948-;
• Cole F.J. A History of comparative anatomy from Arisotle to eighteenth century. London, 1944.
• Remane A., Die Grundlagen des natlirlichen Systems der vergleichenden Anatomie und der Phylogenetik, 2 Aufl., Lpz., 1956.
• Schmitt, Stéphane (2006). Aux origines de la biologie moderne. L'anatomie comparée d'Aristote à la théorie de l'évolution. Paris: Éditions Belin. ISBN.

Comparative anatomy, also called comparative morphology, is the study of the patterns of structure and development of organs by comparing different types of living beings. Data from comparative anatomy are the traditional basis of biological classification. Morphology refers to both the structure of organisms and the science of it. We are talking about external signs, but internal features are much more interesting and important. Internal structures are more numerous, and their functions and relationships are more significant and diverse. The word "anatomy" is of Greek origin: the prefix ana with the root tom means "cutting". Initially, this term was used only in relation to the human body, but now it is understood as a branch of morphology that deals with the study of any organisms at the level of organs and their systems.

All organisms form natural groups with similar anatomical characteristics of the individuals within them. Large groups are successively divided into smaller ones, the representatives of which have an increasing number of common features. It has long been known that organisms of a similar anatomical structure are similar in their embryonic development. However, sometimes even significantly different species, such as turtles and birds, are almost indistinguishable in the early stages of individual development. Embryology and the anatomy of organisms are so closely correlated that taxonomists (specialists in the field of classification) use data from both of these sciences equally when developing schemes for the distribution of species into orders and families. This correlation is not surprising, since the anatomical structure is the end result of embryonic development.

Comparative anatomy and embryology also serve as the basis for the study of evolutionary lineages. Organisms that descended from a common ancestor are not only similar in embryonic development, but also successively go through stages in it that repeat - although not with absolute accuracy, but in general anatomical features - the development of this ancestor. As a result, comparative anatomy is critical to understanding evolution and embryology. Comparative physiology also has its roots in and is closely related to comparative anatomy. Physiology is the study of the functions of anatomical structures; the stronger their similarity, the closer they are in their physiology. Anatomy usually refers to the study of structures that are large enough to be visible to the naked eye. Microscopic anatomy is usually called histology - this is the study of tissues and their microstructures, in particular cells.

Comparative anatomy requires dissection (dissection) of organisms and deals primarily with their macroscopic structure. Although it studies structures, it uses physiological data to understand the connections between them. Thus, in higher animals there are ten physiological systems, the activity of each of which depends on one or more organs. Below, these systems are considered sequentially for animals of different groups. First of all, external features are compared, namely the skin and its formations. The skin is a kind of “jack of all trades”, performing a wide variety of functions; in addition, it forms the outer surface of the body, therefore it is largely accessible to observation without opening it. The next system is the skeleton. In mollusks, arthropods and some armored vertebrates it can be either external or internal. The third system is the musculature, which provides skeletal movement. The nervous system is placed in fourth place, since it is it that controls the functioning of the muscles. The next three systems are digestive, cardiovascular and respiratory. All of them are located in the body cavity and are so closely interconnected that some organs function simultaneously in two of them or even in all three. The excretory and reproductive systems of vertebrates also use some common structures; they are placed in 8th and 9th places. Finally, a comparative analysis of the endocrine glands that form the endocrine system is given. Comparisons of other glands, such as skin glands, are made as the organs in which they are located are considered.

Principles of comparative anatomy

When comparing animal structures, it is useful to consider some general principles of anatomy. Among them, the following are considered especially important: symmetry, cephalization, segmentation, homology and analogy.

Symmetry refers to the features of the arrangement of body parts in relation to any point or axis. In biology, there are two main types of symmetry - radial and bilateral (bilateral). In radially symmetrical animals, such as coelenterates and echinoderms, similar body parts are arranged around a center, like spokes in a wheel. Such organisms are inactive or generally attached to the bottom, and feed on food objects suspended in the water.

With bilateral symmetry, its plane runs along the body and divides it into mirror-like right and left parts. The dorsal (upper, or dorsal) and ventral (lower, or ventral) sides of a bilaterally symmetrical animal are always clearly distinguished (however, the same is true for forms with radial symmetry).

Cephalization is the dominance of the head end of the body over the tail. The head end is usually thickened, located in front of a moving animal and often determines the direction of its movement. The latter is facilitated by the sensory organs almost always present on the head: eyes, tentacles, ears, etc. The brain, mouth opening, and often the animal’s means of attack and defense are also associated with it (bees are a well-known exception). In addition, it has been shown that physiological processes (metabolism) occur here more intensively than in other parts of the body. As a rule, the separation of the head is accompanied by the presence of a tail at the opposite end of the body. In vertebrates, the tail was originally a means of locomotion in water, but over the course of evolution it began to be used in other ways.

Segmentation is characteristic of three types of animals: annelids, arthropods and chordates. In principle, the bodies of these bilaterally symmetrical animals consist of a number of similar parts - segments, or somites. However, although the individual rings of an earthworm are almost identical to each other, there are differences even between them. Segmentation can be not only external, but also internal. In this case, the organ systems within the body are divided into similar parts, arranged in rows in accordance with the externally noticeable boundaries between the somites. Segmentation of chordates appears to be genetically unrelated to that observed in worms and arthropods, but arose independently during evolution. Bilateral symmetry, cephalization and segmentation are characteristic of animals that move quickly in water, on land and in the air.

Homology and analogy. Homologous animal organs have the same evolutionary origin, regardless of the function performed in a given species. These are, for example, human hands and bird wings or the tails of fish and monkeys, which are the same in origin, but are used differently.

Similar structures are similar in their functions, but have different evolutionary origins. These are, for example, the wings of insects and birds or the legs of spiders and horses.

Organs can be homologous and analogous at the same time if they have the same genetic sources and similar functions, but they are located in different segments. These are, for example, various pairs of legs of insects and crustaceans. In these cases, they talk about serial homology (homodynamy), since similar structures form series (series).

When similar organs, which developed from dissimilar previous structures, exhibit a noticeable similarity in structure, they speak of their parallel, or convergent, development. The Law of Convergence states that organs that perform the same functions and are used in the same way become morphologically similar during evolution, no matter how different they may have started out. One of the most remarkable examples of convergence is the eyes of squids and octopuses, on the one hand, and vertebrates, on the other. These organs arose from completely different rudiments, but acquired significant similarities due to the identity of their function.

Animal classification

Before presenting the results of an anatomical comparison of organ systems, it is useful to briefly characterize the main groups of animals, emphasizing the differences that exist between them. These groups are called types; the evolutionary series from the most primitive to the most evolutionarily advanced of them can be represented as follows: Porifera, Mesozoa, Cnidaria (Coelenterata), Ctenophora, Platyhelminthes, Nemertinea, Acanthocephala, Aschelminthes, Entoprocta, Bryozoa, Phoronidea, Brachiopoda, Mollusca, Sipunculoidea, Echiuroidea, Annelida , Arthropoda, Chaetognatha, Echinodermata, Hemichordata and Chordata.

When discussing comparative anatomy, it is not necessary and even undesirable to compare the structure of all representatives of the types. It is necessary to consider only the types that have the most important anatomical features for understanding evolution. Since vertebrates traditionally occupy the first place among the objects of comparative anatomy, all the classes that make up this group will be briefly characterized.

Sponges (Porifera) are considered the most primitive among multicellular animals and are divided into 3 classes in accordance with the characteristics of the material that forms their skeleton. In calcareous sponges these are spicules of calcium carbonate; in ordinary sponges - elastic, flexible fibers of spongin, similar in chemical composition to horn; glass sponges have a thin network of flint needles resembling glass.

Coelenterata, or Cnidaria, include hydroid polyps, jellyfish, sea anemones and corals. The body of these predominantly marine animals consists of only two layers of cells, ectoderm (outer layer) and endoderm (inner layer), surrounding a body cavity called the intestine, with a single mouth opening. An important feature of the group is radial symmetry.

Ctenophora are marine animals somewhat reminiscent of jellyfish. Their significance for comparative anatomy is small, except for the fact that they are the most primitive group, having a true third (middle) germ layer - the mesoderm. Thus, all animals above the level of coelenterates pass through the stage of three germ layers in their embryonic development.

The phylum of flatworms (Platyhelminthes) includes planarians, flukes, tapeworms, etc. All of them, indeed, are flat-bodied and, like coelenterates, lack an anus: undigested food remains are “belched” through the mouth. In these animals, the beginning of brain formation (cephalization) is already noticeable.

The phylum of mollusks (Mollusca) includes snails, bivalves, squids and other so-called. soft-bodied animals. They are usually protected by a shell secreted by an ectodermal layer of tissue. All these animals are equipped with a full set of the organ systems listed above and are distinguished by a very high level of organization.

Annelida are segmented worm-like forms. The phylum Arthropoda includes animals with an exoskeleton and jointed limbs, including crustaceans, centipedes, insects, and arachnids. Both of these types are highly organized and in many ways comparable to vertebrates.

Hemichordata, sometimes considered a subphylum of chordates, are worm-like animals that live on the seabed.

The phylum Chordata consists of the following subphyla: larval chordates (Urochordata), cephalochordates (Cephalochordata) and vertebrates (Vertebrata). The type as a whole is characterized by three main features: the presence, at least in the larvae, of a cartilaginous rod running along the dorsal side of the body and called the notochord; the tubular central nervous system located above it and, finally, the gill slits connecting the pharynx with the left and right surfaces of the body behind the head. In vertebrates, the notochord is replaced by a spine, consisting of cartilage in lower fish and bone in evolutionarily more advanced groups.

Larval chordates are also called tunicates. This subphylum unites several hundred species - from sea squirts attached to the bottom to free-swimming appendiculars and salps.

Cephalochordates, or skullless ones, are represented mainly by the genus Amphioxus, i.e. lancelets, so named because their body is pointed at the head and tail ends. They have numerous gill slits, a notochord and a hollow spinal cord located above it. All three characteristic features of chordates are expressed here in the most primitive form, and lancelets are usually considered close to the ancestors of this entire group of animals.

To consider the comparative anatomy of fish, it is convenient to divide them into 3 groups: cartilaginous, lobe-finned (fleshy-lobed) and bony. The first are represented mainly by sharks and rays. They have thick skin with placoid scales, which are fundamentally different from the scales of other fish. The skeleton is cartilaginous; gill slits open outward; the mouth is located on the underside of the head; the tail is equipped with an unequal-bladed fin. In their internal anatomy, cartilaginous fish are primitive and unspecialized; They have neither lungs nor a swim bladder.

The living lobe-finned species belong to two categories: lobe-finned species (coelacanths) and lungfishes. Lozenge-finned fish are now represented by one genus, Latimeria, in the Indian Ocean off the coast of Africa. They are close to the ancestors of amphibians, therefore they are interesting from an anatomical point of view. Three genera of lungfish have survived to this day: Neoceratodus in Australia, Protopterus in Africa and Lepidosiren in South America. They can breathe through both gills and lungs.

Bony fishes are extremely diverse and numerous; These include more than 90% of all modern fish species. Typically, they have a swim bladder, and the skeleton contains a lot of bone tissue. Usually the body is covered with scales, but many exceptions are known. African polypterus (Polypterus), sturgeons, mud fishes (Amia) and armored pikes are representatives of primitive groups that have survived to this day. They are interesting because the features of their anatomy make it possible to connect modern fish with ancient ones.

Amphibians, or amphibians, are salamanders, newts, toads, frogs and legless forms, the so-called. caecilians. Typically, their larvae live in water and breathe with gills, like fish, and adults come to land and breathe with the help of lungs and skin, although there are many exceptions. The moist skin of amphibians is devoid of scales, feathers and hair; only caecilians have small bone scales embedded in it.

Reptiles, or reptiles, are crocodiles, turtles, lizards and snakes. Their body is covered with scales. They represent the remains of a group of animals that dominated in ancient times, some of them reaching very large sizes. Subsequently, reptiles gave way to more active mammals.

Birds are very close to reptiles. True, they all have feathers, a constant body temperature, excellent lungs and a 4-chambered heart, and most birds can fly. However, their anatomy still reveals many ancestral reptilian features.

Mammals, or animals, are covered with hair and feed their young with milk, which is secreted by special glands. They are descended from reptiles, but like birds, they are warm-blooded and have a 4-chambered heart. Their limbs are turned forward and brought under the body for more efficient locomotion. All mammals, with the exception of three oviparous genera, reproduce by viviparity. People also belong to this class, which increases interest in its study.

Ten physiological organ systems

Leather and its derivatives

The external tissues of any animal can be called skin, but, according to the concepts of comparative anatomy, true skin is characteristic only of chordates. It consists of two tissues, the epidermis on the outside and the dermis (actually the skin, cutis, or corium) underneath.

The epidermis is a derivative of the ectoderm, one of the three original germ layers. In vertebrates it is always multilayered; in the depth there is a germ layer, and on the outside there is a stratum corneum. The latter consists of flat, dead cells that have lost their nuclei. It is constantly exfoliated - either in the form of dandruff, as in higher vertebrates, or in a continuous layer, as in amphibians and reptiles. The cells of the stratum corneum are rich in the protein keratin, which also forms nails and hair. It prevents moisture from evaporating through the skin and, due to its strength, protects it from damage; The integument of reptiles is especially rich in it. The germinal, or malpighian, layer consists of living, multiplying cells. As their number increases, they are pushed to the surface and become part of the stratum corneum.

In mammals, between the germinal and horny layers, two more are distinguished - granular and shiny. The granular one is adjacent to the germinal one and consists of dying cells with pigment granules. The stratum pellucida is located under the stratum corneum and contains dead cells with transparent inclusions. Thus, in mammals the epidermis has four layers: one layer is living, one is dying and two are dead.

The dermis is the thick and relatively soft inner tissue of the skin. It is formed from the middle germ layer, mesoderm, provides nutrition to the epidermis, contains nerve endings, blood vessels, and is often rich in fatty deposits. The bases of hair and feathers are also located here, as well as glands, which are invaginations of the epidermis.

Typically, the skin fits more or less loosely around the body and is separated from the underlying structures by a layer of loose connective tissue - subcutaneous tissue, containing many intercellular spaces.

Arthropods have an external skeleton formed by ectoderm cells. Its outer layer is periodically shed due to body growth. In mollusks, the soft and often ciliated ectoderm usually secretes a protective calcareous shell. The first animal in the evolutionary series with real skin is the lancelet. Its epidermis is formed by a single layer of densely packed cubic cells; however, the cells of the dermis degenerate and fuse, so that it appears structureless and the skin as a whole appears single-layered.

Fish. The skin of fish contains many mucous glands and is usually covered with numerous scales. Several types are known. The scales of sharks and similar forms develop like teeth and are called placoid. The scales of modern bony fishes are formed from the inner layer of skin and are ctenoid (toothed, comb-shaped) or cycloid (round).

The scale primordium is a calcareous deposit in the dermis layer. As it grows, its edge extends out through the epidermis, so that the scales overlap each other like tiles. In some fish, such as the American shell pike, the scales do not overlap each other, but cover the body like tiles. They are called ganoids and increase in size as the fish grows. On cycloid and ganoid scales, seasons of intense growth leave layers resembling tree rings.

Amphibians. The skin of these animals is an additional respiratory organ: it is soft, moist and equipped with a dense network of blood vessels. It contains a huge number of mucous and poisonous glands; characterized by local accumulations of pigment, creating a camouflage color. All amphibians shed their outer layer of skin in a single layer as they grow. At least in the very early stages of development of aquatic amphibian larvae, their ectoderm cells bear cilia that facilitate locomotion and respiration. Keratin is first deposited in the outermost layer of the skin, preventing moisture loss through evaporation. However, amphibians have not yet made significant progress in terms of protection from desiccation and inhabit more or less humid places. The skin of some ancient amphibians contained large bony plates.

Reptiles. The main property of their skin is its ability to resist drying out. It is entirely covered with scales, hard and dry, which is associated with adaptation to life on land, but it can also be elastic, for example in lizards and snakes. In addition, it may contain bony plates, forming an armored covering, as in turtles or on the back and head of crocodiles. Snakes and lizards shed the outer layer of skin in a single layer, while in turtles it comes off in separate flaps.

Reptiles have few skin glands. Scent glands are located on the chin and along the edges of the shell in some turtles, on the back of the thighs and around the cloaca in alligators and crocodiles, and near the cloaca opening in a number of snakes.

Claws on the fingers first appear in some amphibians, but in them they do not play a significant role. All reptiles with limbs, except sea turtles, have well-developed claws.

Birds. The skin of birds cannot be called strong or dense, but it is rich in fat. There are few skin glands, but there is almost always a large sebaceous (coccygeal) gland above the base of the tail. Earwax glands may be located near the external opening of the ear. The feet of birds are covered with the same scales as those of reptiles. Their claws are also similar in origin.

Beak. The horny covers of the jaws of turtles and birds are formed by a modified outer layer of the epidermis. A similar beak was also characteristic of some extinct dinosaurs from the class of reptiles. Among birds, toucans shed their superficial horny layers, like reptiles' skin when molting. The beaks of birds vary in shape and size, which is associated with adaptation to a certain method of feeding. The forelimbs of birds are adapted for flight, so tasks usually performed by the hands of other animals are transferred to the beak. In addition, animals with beaks lack teeth. It can be used as a weapon, for cleaning feathers, for climbing, courtship, nest building, etc.

Feathers are a derivative of reptile scales and a characteristic feature of bird skin. Like scales, a feather begins its growth in the form of a connective tissue protrusion (papilla) of the corium. However, it does not flatten, but stretches into a cylinder, which, rising above the epidermis, splits along one side and unfolds, forming beards along the free edges.

There are three main types of feathers: contour, down and filament. Contour feathers cover the entire body and reach their greatest size on the wings and tail. Downy feathers protect chicks, and in adult birds they form a heat-insulating layer under the contour ones. Powdered down, characteristic of herons and a number of other birds, is distinguished by fragile beards that crumble into powder used in cleaning the plumage. The filament feathers are located along with the down feathers under the contour feathers and can protrude to the surface near the corners of the mouth, forming sensitive hairs. For example, the fringed beard of a turkey is made up of thread-like feathers.

A typical contour feather includes 6 components: the quill, which is immersed in the skin and secures the feather in it; the rod, which is a continuation of the edge and the main axis of the feather; a flat fan of beards connected to each other; an additional feather extending near the junction of the rod and the rim; lower navel - hole at the base of the eye; The superior umbilicus is the second opening at the base of the accessory feather, allowing air to flow in and out of the hollow shaft.

Mammals. In mammals, the skin is usually quite loosely connected to the body by a thick and elastic layer of subcutaneous tissue. It contains numerous glands, such as milk, sebaceous, sweat and odorant. The glands of the last three categories can be very numerous.

Mammary glands, characteristic of mammals, are large structures that serve to feed their young. They are usually located in two rows on the sides of the underside of the body, but can be grouped between the hind limbs, as in cows, horses and many other herbivorous animals, or placed in front, at chest level, as in elephants, monkeys and humans.

Hair represents the second unique feature of mammalian skin. Hair is absent only in some of their aquatic forms, for example whales and sirens (the latter have developed facial setae). A number of animals, such as elephants and pangolins, have very sparse hair; Depending on the species, they vary in thickness - from the delicate fur of a beaver to the long quills of a porcupine. The hair serves for thermal insulation and protection from damage. In addition, hair may be specialized to perform specific functions; for example, on the muzzle of many animals there are tactile hairs (“whiskers”) called vibrissae.

Horns. In giraffes, deer and bovids, horns are bony outgrowths on the frontal bones of the skull, covered with skin or its derivatives. In giraffes they are constantly covered with skin, but in deer they branch out as they grow and eventually lose their skin. The horns of rhinoceroses and the scales of pangolins are formed by a mass of fused hairs. In bovids, such as cows and antelopes, as well as in the American pronghorn, the horns are covered with keratin (horny) sheaths, derivatives of the stratum corneum of the epidermis. Pronghorn has these sheaths, while deer have entire antlers shed each year and grow back.

Claws. In mammals, claws reach the peak of their development and diversity. The nails of monkeys and humans and the hooves of large herbivorous animals are modified claws.

Skeletal system

The skeleton supports, protects and connects the animal's body parts. It comes in different types and is formed from different materials.

Invertebrates. Among the simplest, radiolarians have a complex, geometrically regular flint skeleton, and foraminifera are protected by calcareous shells of a peculiar shape.

Sponge skeletons can be built from three different materials: lime, the horn-like protein spongin, and silica. Lime and spongin are sometimes combined, but glass sponges have a purely flint skeleton. In coelenterates, the skeleton is rare, except for corals, in which it is formed by both external and internal calcareous structures. Coral reef limestones are mainly deposits of the skeletons of dead corals. In all primitive groups, the skeleton plays a supporting and protective role, but is not used for locomotion. Flatworms and roundworms lack it. Some annelids live in calcareous tubes formed by their own secretions. Different types of worms have setae, which are considered skeletal structures. Calcareous shells of mollusks are mainly external formations; the exception is the inner shell of the cuttlefish. Slugs and octopuses lack skeletons.

Arthropods are characterized by a composite skeleton that covers the outside of their entire body, including antennae (antennae) and legs. It consists of the carbohydrate chitin, and in crustaceans it can contain large amounts of calcium. The chitinous shell, which develops from the ectoderm during embryogenesis, is a dead formation and cannot grow, therefore, increasing in size, all arthropods periodically shed the outer layer of the skeleton (molt). Roundworms also repeatedly change their tough outer covering, called the cuticle, as they grow.

Vertebrates. The vertebrate skeleton is formed not only by bones: it includes cartilage and connective tissue, and sometimes it includes various skin formations.

In vertebrates, it is customary to distinguish the axial skeleton (skull, notochord, spine, ribs) and the skeleton of the limbs, including their girdles (shoulder and pelvic) and free sections. Lancelets have a notochord, but no vertebrae or limbs. Snakes, legless lizards and caecilians lack the skeleton of limbs, although some species of the first two groups retain their rudiments. In eels, the pelvic fins corresponding to the hind limbs have disappeared. Whales and sirenians also have no external signs of hind legs.

Scull. Based on their origin, there are three categories of skull bones: replacement cartilage, integumentary (overhead, or skin) and visceral. Invertebrates lack a structure comparable to the skull of vertebrates. In hemichordates, tunicates and cephalochordates there are no signs of a skull. Cyclostomes have a cartilaginous skull. In sharks and their relatives, it may once have contained bones, but now its box is a single monolith of cartilage with no seams between the elements. Bony fish have more different types of bones in their skulls than any other class of vertebrates. In them, like all higher groups, the central bones of the head are embedded in cartilage and replace it, and therefore are homologous to the cartilaginous skull of sharks.

Integumentary bones arise as calcareous deposits in the dermal layer of the skin. In some ancient fish, they were plates of shell that protected the brain, cranial nerves and sensory organs located on the head. In all higher forms, these plates migrated into the depths, were incorporated into the original cartilaginous skull and formed new bones, closely related to the replacement ones. Almost all of the outer bones of the skull come from the dermal layer of the skin.

The visceral elements of the skull are derivatives of the cartilaginous gill arches that arose in the walls of the pharynx during the development of gills in vertebrates. In fish, the first two arches have changed and turned into the jaw and hyoid apparatus. In typical cases, they retain 5 more gill arches, but in some genera their number has decreased. The primitive modern sevengill shark (Heptanchus) has as many as seven gill arches behind the jaw and hyoid arches. In bony fishes, the jaw cartilages are lined with numerous integumentary bones; the latter also form gill covers that protect the delicate gill filaments. During the evolution of vertebrates, the original jaw cartilages were steadily reduced until they disappeared completely. If in crocodiles the remainder of the original cartilage in the lower jaw is lined with 5 paired integumentary bones, then in mammals only one of them remains - the tooth, which completely forms the skeleton of the lower jaw.

The skull of ancient amphibians contained heavy integumentary plates and was similar in this respect to the typical skull of lobe-finned fish. In modern amphibians, both applique and replacement bones are greatly reduced. There are fewer of them in the skull of frogs and salamanders than in other vertebrates with a bony skeleton, and in the latter group many elements remain cartilaginous. In turtles and crocodiles, the skull bones are numerous and tightly fused to each other. In lizards and snakes they are relatively small, with the external elements separated by wide intervals, as in frogs or toads. In snakes, the right and left branches of the lower jaw are very loosely connected to each other and to the cranium by elastic ligaments, which allows these reptiles to swallow relatively large prey. In birds, the skull bones are thin but very hard; in adults they have fused so completely that several sutures have disappeared. The orbital sockets are very large; the roof of the relatively huge braincase is formed by thin integumentary bones; the light jaws are covered with horny sheaths. In mammals, the skull is heavy and includes powerful jaws with teeth. The remains of the cartilaginous jaws moved to the middle ear and formed its bones - the hammer and the incus.

In birds and reptiles, the skull is attached to the spine using one of its condyles (articular tubercle). In modern amphibians and all mammals, two condyles located on the sides of the spinal cord are used for this.

The spine, or vertebral column, is present in all chordates, with the exception of the skullless and tunicates. In embryonic development, it is always preceded by a notochord, which is preserved for life in lancelets and cyclostomes. In fish, it is surrounded by vertebrae (in sharks and their closest relatives - cartilaginous) and looks clear-shaped. In mammals, only rudiments of the notochord are preserved in the intervertebral discs. The notochord is not transformed into vertebrae, but is replaced by them. They arise during embryonic development as curved plates that gradually surround the notochord in rings and, as they grow, almost completely displace it.

A typical spine has 5 sections: cervical, thoracic (corresponding to the rib cage), lumbar, sacral and caudal.

The number of cervical vertebrae varies greatly depending on the group of animals. Modern amphibians have only one such vertebra. Small birds can have as few as 5 vertebrae, while swans can have up to 25. The Mesozoic marine reptile plesiosaur had 72 cervical vertebrae. In mammals there are almost always 7 of them; the exception is sloths (from 6 to 9). In cetaceans and manatees, the cervical vertebrae are partially fused and shortened in accordance with the shortening of the neck (according to some experts, manatees have only 6 of them). The first cervical vertebra is called the atlas. In mammals and amphibians it has two articular surfaces, which include the occipital condyles. In mammals, the second cervical vertebra (epistropheus) forms the axis on which the atlas and skull rotate.

Ribs are usually attached to the thoracic vertebrae. Birds have about five, mammals have 12 or 13; snakes have a lot. The bodies of these vertebrae are usually small, and the spinous processes of their upper arches are long and inclined backwards.

There are usually from 5 to 8 lumbar vertebrae; in most reptiles and all birds and mammals they do not bear ribs. The spinous and transverse processes of the lumbar vertebrae are very powerful and, as a rule, directed forward. In snakes and many fish, the ribs are attached to all the trunk vertebrae, and it is difficult to draw the boundary between the thoracic and lumbar regions. In birds, the lumbar vertebrae are fused with the sacral vertebrae, forming a complex sacrum, which makes their backs more rigid than those of other vertebrates, with the exception of turtles, in which the thoracic, lumbar and sacral regions are connected to the shell.

The number of sacral vertebrae varies from one in amphibians to 13 in birds.

The structure of the caudal region is also very diverse; in frogs, birds, apes and humans it contains only a few partially or completely fused vertebrae, and in some sharks it contains up to two hundred. Toward the end of the tail, the vertebrae lose their arches and are represented by only bodies.

Ribs first appear in sharks as small cartilaginous projections in the connective tissue between muscle segments. In bony fishes they are bony and homologous to the haemal arches located below on the caudal vertebrae. In four-legged animals, such fish-type ribs, called lower, are replaced by upper ones and are used for breathing. They are laid in the same connective tissue partitions between muscle blocks as in fish, but are located higher in the body wall.

Skeleton of limbs. The limbs of tetrapods developed from the paired fins of lobe-finned fish, the skeleton of which contained elements homologous to the bones of the shoulder and pelvic girdle, as well as the front and hind legs.

Originally there were at least five separate ossifications in the shoulder girdle, but in modern animals there are usually only three: the scapula, the clavicle and the coracoid. In almost all mammals, the coracoid is reduced, attached to the scapula, or absent altogether. In some animals, the scapula remains the only functional element of the shoulder girdle.

The pelvic girdle includes three bones: the ilium, the ischium and the pubis. In birds and mammals they completely merged with each other, in the latter case forming the so-called. innominate bone. In fish, snakes, whales and sirens, the pelvic girdle is not attached to the spine, which therefore lacks the typical sacral vertebrae. In some animals, both the shoulder and pelvic girdles include accessory bones.

The bones of the front free limb in quadrupeds are basically the same as those in the hind limb, but they are called differently. In the forelimb, if you count from the body, first comes the humerus, followed by the radius and ulna, then the carpals, metacarpals and phalanges of the fingers. In the hind limb they correspond to the femur, then the tibia, tibia, tarsus, metatarsal bones and phalanges of the fingers. The initial number of fingers is 5 on each limb. Amphibians have only 4 toes on their front paws. In birds, the forelimbs are transformed into wings; the bones of the wrist, metacarpus and fingers are reduced in number and partially fused to each other, the fifth finger on the legs is lost. The horses only have their middle finger left. Cows and their closest relatives rest on the third and fourth toes, and the rest are lost or reduced. Ungulates walk on their toes and are called phalangeal walkers. Cats and many other animals, when walking, rely on the entire surface of their fingers and belong to the digitimate type. Bears and humans press their entire sole to the ground when moving and are called plantigrade walkers.

Exoskeleton. Vertebrates of all classes have an exoskeleton in one way or another. The head plates of scutes (extinct jawless animals), ancient fish and amphibians, as well as the scales, feathers and hair of higher tetrapods, are skin formations. The shell of turtles is of the same origin - a highly specialized skeletal formation. Their skin bone plates (osteoderms) moved closer to the vertebrae and ribs and merged with them. It is noteworthy that the shoulder and pelvic girdles parallel to this have shifted inside the chest. In the crest on the back of crocodiles and the shell of armadillos there are bone plates of the same origin as the shell of turtles.

Muscular system.

The main function of the muscular system is to move parts of the skeleton; the corresponding muscles are called skeletal. However, there are other types and functions. By contracting, the muscles create a pulling force; they cannot push. At the same time, they become thicker and shorter, but their volume does not change noticeably. Muscle activity is controlled by the nervous system and can be voluntary or involuntary. Skeletal muscles are of the voluntary type.

Types of muscles. In vertebrates, there are three categories of muscle tissue: striated, cardiac and smooth.

The striated muscles, which form the bulk of the body's tissue, act voluntarily.

They are connected to the skeleton, contract with great speed and force, but with prolonged work they always get tired and require rest. By their nature they are segmental, and in color they can be red, like beef, or light (“white”), like in fish and in the “breast” of chickens. Their fibers are multinucleated and collected in bundles, surrounded by a connective tissue film called perimysium.

Smooth muscles are not attached to the skeleton; they are located in the walls of blood vessels, the digestive tract and in the dermal layer of the skin. These muscles are devoid of transverse stripes, contract involuntarily, slowly and weakly, but do not know fatigue. Their cells are mononuclear and are not grouped into bundles surrounded by perimysium. In this respect they resemble the muscle cells of lower invertebrates.

The heart muscle (myocardium) is formed by cells that develop from the same embryonic tissue as the smooth muscle cells of the blood vessels, but here they are multinucleated, red in color and capable of rapid and strong contraction. In lower vertebrates they are somewhat elongated, while in higher ones they are wide and connected by jumpers into a narrow-loop network.

Invertebrates. It is difficult to say when muscles arose during the evolution of the animal kingdom. Contractile fibers are found in the cells of protozoa, sponges, and coelenterates, but specialized muscle cells appear only in flatworms and roundworms. In all invertebrates up to the level of mollusks, they lack cross-striations and resemble the smooth muscle cells of vertebrates. They do not contract very strongly and always relatively slowly. The exception here is mollusks: the closing muscles in bivalves can be considered skeletal. Developed muscles are characteristic of annelids, especially earthworms. In the wall of their body there are circular muscles, which reduce its diameter, and longitudinal muscles, which shorten it. There are also microscopic muscles (there are 4 pairs of them in each body segment) that move the bristles and are capable of sticking them into the soil. An earthworm crawls in its characteristic way due to contractions of all three categories of muscles - circular, longitudinal and microscopic.

Excellent striated muscles, capable of rapid and powerful contraction, are characteristic of arthropods. The flight muscles of some insects are the fastest-acting of all known: in this sense they surpass even the similar muscles of hummingbirds. It is interesting to note that the skeletal muscles of arthropods control the movements of the exoskeleton, being inside it, under its protection.

Vertebrates. Vertebrate muscles can be divided into five groups depending on their embryonic origin: segmental (skeletal), visceral, ocular, cutaneous, and branchiomeric muscles.

The segmental muscles never cross the midline of the abdomen; they are located in overlapping layers on the sides of the body in accordance with the original segments, or somites, of the embryo. The muscles of the limbs also develop from these axial blocks.

In lancelets, cyclostomes and fish, the segmental muscles remain in their original and most elementary state. In fish fins they are simple and consist mainly of lifters and lowerers. In the limbs of tetrapods they are numerous and varied in function. Segmental muscles are attached to the bones of the skeleton either directly or with the help of tendons (strands of connective tissue).

Visceral muscles, acting involuntarily and devoid of transverse stripes, are located primarily in the walls of the digestive tube. They are responsible for the peristaltic movements that push food through the digestive tract.

In the region of the pharynx in fish, their non-segmental blocks are attached to the gill arches and turn into the striated muscles of the branchiomeres. In higher vertebrates they extend onto the surface of the head, becoming voluntary facial and jaw structures. This is a remarkable example of the convergent transformation of involuntary smooth muscles into voluntary striated muscles in the process of their adaptation to the role of skeletal muscles.

Eye muscles. The mobility of the eyeballs is ensured by the fact that six thin muscles are attached to them. In all vertebrates they arise from three paired somites in the head of the embryo. By their origin, the ocular muscles are related to the segmental ones, but are usually considered separately because of their uniqueness. Their work is controlled by the third, fourth and sixth cranial nerves.

The cutaneous muscles are very unique in origin. When segmental muscles arise from the middle germ layer, mesoderm, free cells are separated from its outer edge, losing their segmental distribution. They form a vaguely defined layer of tissue called the dermatome, which completely surrounds the developing body of the embryo, adjacent to the ectoderm from the inside. From it the corium is formed along with the muscles located in it. They should not be confused with those that cause, for example, the trembling of the skin on the shoulders of a horse that drives away flies: such skin movements are caused by voluntary muscles - derivatives of skeletal muscles, and the skin muscles themselves are involuntary. In birds, they are attached to the bases of feathers and, when contracted, raise them. Similar muscles make the hair on the body of animals stand on end. So-called pimples “Goose bumps” in humans are also the result of contraction of involuntary skin muscles.

Nervous system

To regulate and coordinate the activities of all parts of the body, evolutionarily advanced animals have a highly specialized nervous system. In low-organized forms it is arranged relatively simply.

Invertebrates. In sponges, sensory (“sensitive”) mechanisms are not localized in strictly defined cells of the body, i.e. They don't have a real nervous system. Specialized nerve cells (neurons) appear in coelenterates. In Hydra they form a homogeneous network serving all parts of the body. In sea stars, the mouth is surrounded by a nerve ring, from which nerve trunks of ectodermal origin extend into each of the five arms. In flatworms and annelids, the head contains a paired collection of nerve cells called a ganglion (nerve ganglion) and serves as a primitive brain. A paired nerve trunk also stretches from it along the lower side of the body. In the earthworm, its branches are united and form the abdominal nerve cord with the ganglia. In arthropods, the nervous system is basically the same, the brain is enlarged and divided into lobes, the ventral nerve trunk is shortened, and some of its ganglia are fused with each other.

Vertebrates differ from invertebrates in three important features of the central nervous system: it occupies a dorsal position, develops from the dorsal ectoderm of the embryo, and is represented by a tube. It is laid as a longitudinal groove along the midline of the back. Later, the edges of the groove rise, bend towards each other and connect into the neural tube. At the head end it swells and forms protrusions, which turn into various parts of the brain.

The structural basis of the nervous system is the neuron. It consists of a compact cell body and sensory and motor processes extending from it. Sensory processes called dendrites are highly branched and conduct nerve impulses into the body of the neuron. Along motor fibers, axons, impulses travel from the neuron body to another cell.

The nervous system of vertebrates is usually divided into two parts - central and peripheral. The first consists of the brain and spinal cord; the second is from the cranial (cranial) nerves, spinal nerves and the autonomic nervous system.

Brain. In the lancelet, only the cavity at the anterior end of the neural tube is expanded, and there is no brain as such. In all vertebrates, it is divided into 5 sections: the terminal, intermediate, midbrain, hindbrain and medulla oblongata.

The main components of the telencephalon are the olfactory lobes, responsible for the corresponding “feeling,” and the cerebral hemispheres, the main center of nervous coordination. The diencephalon connects the telencephalon to the midbrain. The parietal organ (parietal eye) and the pineal gland (epiphysis) extend from its dorsal surface, and the optic nerves form below it. The main parts of the midbrain are the paired optic lobes, especially important for lower vertebrates. The hindbrain forms the cerebellum, which lies on the dorsal side of the medulla oblongata, which is responsible for the coordination of movements. All cranial nerves after the fourth arise on the sides of the medulla oblongata in front of its transition to the spinal cord.

The brain of the Squalus shark is elongated in length, and its olfactory and visual lobes are noticeably prominent. The large hemispheres are small, which indicates low development of “intelligence”; The cerebellum, which is hollow inside, is relatively large. All actively swimming (pelagic) fish have large optic lobes and cerebellum, since these animals require good vision and fine coordination of movements. The same is true for birds. In amphibians, the cerebellum is very poorly developed. In salamanders, the optic lobes are almost invisible, but in frogs and toads they are large, and they see perfectly. The main feature of the brain of birds and mammals is the large and complex cerebral hemispheres.

Mammals are also characterized by a large, massive cerebellum; its cavity, free in lower forms of vertebrates, is here occupied by the branches of nerve fibers, forming a peculiar pattern in the section - the “tree of life”. The optic lobes are transformed into a pair of anterior tubercles called quadrigeminal and play a subordinate role in providing vision. Its main center moved in mammals to the occipital lobe of the cerebral hemispheres.

In vertebrates, the spinal cord extends from the brain along the spinal canal formed by the upper (neural) arches of the vertebrae. A deep and narrow dorsal and shallower and wider abdominal slits run along its entire length. Paired spinal nerves extend from the lateral surfaces, also along its entire length. Each begins with two roots - dorsal and ventral, which then merge. The dorsal root carries a ganglion (nerve ganglion), while the ventral root does not have one. In lower vertebrates, both roots contain motor nerve fibers, and the dorsal one, in addition, contains sensory fibers. In mammals, the dorsal root is purely sensory, and the ventral root is motor.

The number of paired spinal nerves varies widely - from 10 in frogs to several hundred in snakes. In three places on each side of the body they are connected to each other into plexuses: cervical, brachial (at the level of the shoulder girdle) and sacral (in the pelvis). The interconnections of nerves within the plexuses are weak in fish, more developed in amphibians and reptiles, and extremely complex in mammals.

Cranial nerves. A typical cranial nerve originates from the brain and exits the skull through a small opening. It was traditionally believed that fish and amphibians have 10 pairs of such nerves, and reptiles, birds and mammals have 12. However, this generalization requires some corrections. In 1895, in front of the first, the terminal (terminal) nerve was discovered, which, as it turned out, is present in all vertebrates except birds. It was called zero to avoid confusion in the existing numbering system.

The names and numbers of the cranial nerves are as follows: 0 - terminal, I - olfactory, II - visual, III - oculomotor, IV - trochlear, V - trigeminal, VI - abducens, VII - facial, VIII - auditory, IX - glossopharyngeal, X – vagus, XI – accessory, XII – sublingual.

These nerves are serially homologous to the spinal nerve roots, but are more specialized. The thin terminal nerve is considered sensory. The olfactory sense determines sensitivity to odors (in proto-aquatic vertebrates, it reacts to odorous substances in the water and not in the air). The optic nerve is formed as an outgrowth of the brain and initially represents a branch of the neural tube. At its peripheral end is the retina of the eye, from which it transmits impulses to the brain. The third, fourth and sixth nerves are motor nerves that control the eye muscles. The trigeminal nerve, which combines sensory and motor functions, arises as two separate nerves that unite at the gasserian (lunate) ganglion. In fish it is divided into 4 main branches going to different parts of the head, and in reptiles, birds and mammals it is divided into three, which is why it is called trigeminal. The facial nerve, also mixed (motor and sensory), innervates the hyoid arch, jaws and lateral line organs on the surface of the head in fish. In its functions it is similar to the trigeminal, but is located more superficially. The sensory auditory nerve is connected to the inner ear. In higher terrestrial vertebrates, it is divided into two branches: the cochlear branch goes to the auditory receptors, and the vestibular branch goes to the vestibule and semicircular canals (vestibular apparatus), therefore it is also called the vestibular-cochlear branch. The nerve as a whole serves hearing and spatial orientation. The mixed glossopharyngeal nerve in fish innervates the region of the first gill slit. In higher vertebrates, its branches go to the tongue and pharynx. The large, also sensory-motor, vagus nerve, part of the parasympathetic nervous system, controls the branchial region behind the first slit and sends large branches to the internal organs, particularly the lungs and stomach. It arose as a result of the union of at least four spinal nerves, the roots of which shifted forward - onto the medulla oblongata. During evolution, the motor accessory nerve separated from the vagus nerve, the branches of which go to the neck and shoulders. In snakes it degenerates. The hypoglossal nerve controls the muscles of the tongue. It has already been noted in sharks, but in other fish and amphibians the XI and XII nerves are unknown.

The autonomic nervous system consists mainly of a paired chain of nerve ganglia, which stretches along the dorsal side of the abdominal cavity. It is connected to the cranial nerves, to each spinal nerve near the junction of its roots, and to all internal organs. This involuntary (autonomous) system controls smooth muscles, cardiac muscle, iris and ciliary muscles of the eye, all glands, as well as cutaneous muscles associated with the roots of feathers and hair.

It consists of two systems that are opposite in their action - parasympathetic and sympathetic. If any organ controlled by these nerves receives a stimulating signal from one of them, then the other inhibits its activity. This dual nervous control of the glands, blood vessels, heart, intestines and intrinsic muscles of the eye ensures the harmonious functioning of all organs of the body.

The parasympathetic system is connected to three centers - in the midbrain and medulla oblongata and in the sacral region of the spinal cord, and the sympathetic system is connected to the spinal nerves along the entire spinal cord from the medulla oblongata to the sacral region. The autonomic nervous system of all vertebrates is structured similarly, but in higher forms it is more complex.

Sense organs. Everyone knows such sensory organs of different animals as antennas (antennae, ears), ears, nose and eyes. There are many others - bristles, statocysts, sensory bodies, chemoreceptor (taste) buds, etc. Vertebrates typically have five senses: vision, hearing, taste, smell and touch; however, they also have a sense of balance (body position in space) and a corresponding organ, represented by the three semicircular canals of the inner ear and extremely important, for example, for birds and fish. In pit snakes, there is a small depression in front of each eye where a thermoreceptor organ is located that senses heat from a distance. There are also so-called general (i.e. not associated with special organs) sensations: thirst, hunger, cold, pain, pressure, muscle and tendon feelings.

In typical cases, sensory impulses reach the central nervous system either through the cranial nerves or through the dorsal roots of the spinal nerves, and from the internal organs through the fibers of the autonomic nervous system. The lateral line organs, represented by special canals in the skin on the head and body of fish, are clearly visible even in the larvae of amphibians and their aquatic forms, but in all terrestrial vertebrates they have disappeared without a trace. The organs of the chemical senses - smell and taste - are not always easily distinguishable in aquatic vertebrates, but, as a rule, are located in the mouth and nasal cavity in terrestrial ones. In insects they are located in the antennae, and in some fish they are on the skin.

Eyes. In lower invertebrates these may be just slightly specialized pigment spots. Spiders usually have 8 simple eyes at the top of their heads. In millipedes, simple eyes form two clusters on the sides of the head. Crayfish, lobsters and crabs are characterized by two compound eyes, consisting of a large number of small “eyes”. Insects usually have three simple and two compound eyes, but many small forms lack simple eyes. In cephalopods and vertebrates, the eyes, despite their high specialization, are striking in their similarity. They arise from completely different embryonic rudiments, but in their final form they are almost identically structured, down to the level of the eyelids, pupils, irises, lenses, fluid media and retinas containing rods and cones; True, the optic nerves are no longer the same. This is a striking example of the convergence of similar structures.

Ears. Hearing organs appear in some insects in the form of eardrums on the body or legs and associated structures. The vertebrate ear is a dual sense organ—hearing and balance.

Digestive system

The digestive system is the intestinal tube (digestive tract) with all its auxiliary parts. It is most developed in vertebrates, in which it consists of a mouth, followed by a pharynx, esophagus, stomach, intestines and anus or cloaca. In addition, their digestive system includes the salivary glands, liver and pancreas.

Invertebrates. In protozoa, so-called digestive vacuoles inside the cell. Ciliates have many of them, and they act like small stomachs. Sponges do not have formations comparable to a stomach or intestines. These animals feed on plankton, i.e. microscopic living creatures suspended in water, which are drawn into their body through numerous pores as a result of the beating of special flagella, the so-called. collar cells. In coelenterates, the body wall has only two layers - ectoderm and endoderm, and it can be compared to a two-layer sac. The inner layer, endoderm, lines the intestinal cavity in all animals more complex than sponges. Thus, coelenterates have a kind of stomach (or intestines), but the rest of the digestive organs are absent, except for the mouth corresponding to the blastopore. In the embryos of all animals, the blastopore is the primary opening leading to the digestive tract. In almost all invertebrates, with the exception of echinoderms and some small groups, it turns into a mouth opening. In echinoderms and chordates, the blastopore becomes the anus, and the oral opening breaks through the digestive system later. In echinoderms it appears in the center of the body on its underside, and in chordates it occurs where the head develops. It seems that this change in mouth position indicates that the cephalic end of the body of invertebrates is homologous to the caudal end of chordates.

Vertebrates. The components of the digestive system in invertebrates and vertebrates are named the same according to their functions. However, most likely, only the stomachs are homologous among them, since the oral and anal openings have swapped places. Apparently, the ancestral line of chordates, echinoderms and other “deuterostomes” among invertebrates includes only protozoa and coelenterates. At the level of the latter, the evolutionary paths of the animal kingdom diverged sharply.

Fish. The digestive system of spiny sharks (Squalus) is a good illustration of a variant that is primitive for fish. The large mouth is located on the underside of the head. The teeth, which are modified placoid scales, form several successive rows. Their shape is adapted only for cutting prey, although the ability to grind food before swallowing is extremely advantageous. Many bony fish have long and pointed teeth, suitable only for catching and holding prey; Some species of this group are toothless, but there are also those armed with pressing-type teeth.

It can hardly be said that sharks have a tongue, except for a rather loose fold of skin that covers the inside of the cartilaginous hyoid arch. In bony fishes, this arch can protrude from below into the oral cavity, but never forms a muscular structure.

The shark's pharynx is an extended extension of the oral cavity. Its side walls are supported by five gill arches. All fish have 5 gill slits. Almost all sharks and their close relatives have a modified gill slit behind the eye, connected to the hyoid arch. This is the so-called spray: through it, water enters the pharynx, which then washes the gills, which is necessary if the mouth is busy with food. In all cartilaginous fish, not counting chimeras, each gill slits, including the squirter, opens on the lateral surface of the body behind the head. In chimeras and bony fishes, these openings are covered from the outside by an operculum.

In almost all fish, the pharynx leads directly to the stomach, and it is difficult to talk about the presence of an esophagus here. Sharks have a J-shaped stomach and are relatively very large. Like many other fish, the inner surface of the wall of its cardial (head) section is lined with long multi-branched papillae. These glandular formations secrete powerful digestive juices necessary for animals that swallow their prey whole or in large pieces. When the stomach is free of contents, it collapses and the middle and lower zones of its internal surface form longitudinal folds. When the stomach stretches, they flatten.

The shark's intestines are short, which is generally typical for carnivorous (meat-eating) animals, while in herbivorous forms it is long. In the short intestine, meat does not stay long, otherwise it would begin to rot. The pyloric valve (a slightly modified circular sphincter muscle) separates the stomach from the small intestine. Immediately behind it, the ducts of the gallbladder and pancreas flow into it. The short small intestine continues with a wide thick intestine, with a spiral fold inside, the so-called. spiral valve. This formation significantly increases the internal surface of the intestine and thereby the rate of absorption. The spiral valve is found in lampreys, sharks, lungfishes, ganoids and some primitive bony fishes. In the latter, the intestines are often elongated, highly convoluted and surrounded by layers of fat.

In sharks, it ends in a large chamber, the cloaca, into which the ducts of the kidneys and reproductive organs open. The cloaca is characteristic of cartilaginous and lungfishes, amphibians, reptiles, birds, as well as primitive oviparous mammals. In typical bony fish and mammals, the intestinal and genitourinary tracts are separated from each other. Many bony fish have three such openings: for feces, urine and reproductive products.

In all aspects of anatomy, amphibians occupy a transitional position between ancient pulmonary fish and reptiles. They are characterized by small, uniform teeth and a fleshy tongue. In frogs, toads and some tailed forms, it is sticky and is able to quickly be thrown out of the mouth to catch small insects. In tailless animals, it is attached to the anterior edge of the lower jaw and at rest lies in the mouth with its apex backwards. Such a tongue is thrown out passively - when the mouth is sharply opened, and is retracted back due to the contraction of its muscles. In tailed amphibians, the tongue moves forward in a forward motion.

The pharynx of amphibians is formed in the gill region, present in their aquatic larvae and adults of some aquatic species, but in terrestrial forms the gills disappear before reaching land. The stomach, like in fish, is almost not separated from the oropharyngeal cavity, and the esophagus is poorly defined. Salamanders have a long stomach that matches the shape of their body, and their intestines form loops and are slightly twisted into a spiral. In frogs and toads, the stomach is curved so that its posterior section is oriented approximately across the spine, as in many mammals, and the intestines are curled into a ball.

Reptiles differ little from amphibians in their digestive system, except for the oral cavity. The large conical teeth of crocodiles are covered with a layer of enamel. In both crocodiles and lizards they are all the same in shape - this system is called homodont (in mammals they are different and the dental apparatus is heterodont). The poisonous teeth of snakes are equipped with a longitudinal channel, or groove, and form something like an injection needle.

Snakes and lizards are not capable of chewing. Crocodiles tear off pieces of prey, and turtles take bites. Some snakes have mouths so extensible (the jaws are connected by elastic ligaments) that they can swallow prey four times the diameter of their resting head.

The snake's long and retractable forked tongue is very sensitive. It constantly thrusts out and retracts and vibrates in front of her nose when she is aroused. The chameleon has a long, sticky tongue that extends far out of its mouth to catch small prey. Turtles and crocodiles have short and fleshy tongues.

All reptiles have a pronounced esophagus and stomach, followed by a long, coiled intestine.

Birds have a specialized digestive system, partly due to the presence of a beak, which does not allow them to chew food: the jaws with teeth must be strong, and therefore heavy, which is incompatible with flight. The inner lining of the oral cavity is usually hard and dry, and there are few taste buds. The shape of the tongue varies greatly: it is often forked or serrated towards the rear end (this helps push food towards the esophagus). The pharynx is not clearly defined: this area is distinguished by a respiratory opening leading from it into the larynx. The esophagus is a long tube that almost always includes an extended area for storing food, the so-called. goiter. In geese, owls and some other birds, the entire posterior part of the esophagus is expanded, and we can say that either there is no goiter, or this entire expanded region corresponds to it. Pigeons are the only birds that can drink water with their heads lowered below the body thanks to the peristaltic movements of the esophagus, like in mammals.

From the esophagus (crop), food enters the anterior section of the stomach, the glandular section that was previously mistakenly considered part of the esophagus. This is an extension of the digestive tube, in the thick walls of which there are glands that secrete gastric juice. This is followed by the gizzard (“umbilicus”), a unique anatomical formation. Its muscles are a derivative of the light, involuntary muscles of the intestinal wall, but due to their high activity they have become dark red and appear striated, although they retain their involuntary character. In granivorous birds, the muscular stomach is especially well developed and is lined on the inside with horn-like tissue that does not contain glands. In carnivores, its walls are weaker, and their lining is soft. It is believed that some dinosaurs also had a muscular stomach like a bird's.

Birds of prey have a short intestine, while herbivores have a very long and convoluted intestine. Near its posterior end, a pair of hollow outgrowths extends, the so-called. caecum. In owls they are very extensive, in chickens they are represented by long tubes, and in pigeons they are rudimentary.

Mammals are characterized by a diverse and highly efficient digestive system. First of all, their lips reached their highest development. They appear in amphibians, and, with the exception of turtles, birds and whales, steadily increase during the evolution of vertebrates, culminating in rodents in the form of their huge cheek pouches.

Mammalian teeth can be almost identical and conical (like those of dolphins and other toothed whales), adapted only for grasping and holding prey, but, as a rule, they are heterogeneous and complex in structure.

A typical animal tooth consists of a crown covered with a layer of enamel. Beneath it there is dentin, which continues into the root, which is surrounded by a layer of cement. In the center of the dentin there is a cavity containing the so-called. pulp - soft tissue with artery, vein and nerve. Typically, tooth growth stops after reaching a certain size, but the tusks of some animals, the incisors of rodents, and the molars of bulls and horses wear heavily at the apex of the crown and, in order to continue to function, grow continuously at the base, where dentin, cementum, and enamel are formed. The pulp cavity of the latter type of teeth is open (it is not closed in the root, which is actually absent). Such teeth are called hypsodont.

Typically, mammals have two sets of teeth. The first, so-called milk ones fall out and are replaced by permanent ones. Sirens and toothed whales have only one set of teeth. Mammals are characterized by 4 types of teeth: incisors, canines, premolars (premolars) and molars (molars). The latter appear only once - in the second change of teeth. Canines are especially strongly developed in carnivores, absent in rodents, and small or absent in bovids, deer and horses. The molars and premolars of predatory animals have specialized cutting edges. In pigs and humans, the tops of these teeth are relatively flat and are used for crushing food. In bovids, elephants and horses, layers of enamel, dentin and cement form complex folds in the flat-topped grinding teeth. Here the outer layer of cementum not only surrounds the root but also extends to the apex of the crown.

The tongue in mammals develops mainly from a tubercle at the bottom of the pharynx. It grows forward and combines with other tissues in the area to form a complex and multifunctional muscular structure. This is a good organ of touch and the main area where taste buds are located. Usually the tongue is flattened and moderately stretchable. In anteaters it is round in cross section and can extend far from the mouth, like in woodpeckers; in whales it is almost motionless; in cats it is covered with horny papillae for scraping meat from bones.

The esophagus stretches from the pharynx to the stomach in the form of a soft tube, varying slightly within the class. Food and liquids can be pushed through it by peristaltic muscle contractions.

The relatively large stomach of mammals is usually located transversely in the anterior part of the abdominal cavity. Its anterior, cardiac end is wider than the posterior, pyloric end. The rest of the inner surface of the stomach wall, when unstretched, is folded, like in sharks and reptiles. In ruminants (cows, sheep, etc.) the stomach consists of four sections. The first three - scar, mesh and book - are derivatives of the esophagus, and the last - abomasum - corresponds to the stomach of most groups (according to some authors, the esophagus gave rise only to the scar and mesh). Ruminants eat quickly, filling a huge rumen with food, from which individual portions of cud are then formed in the mesh. Each of them is regurgitated, thoroughly chewed again and swallowed again, this time ending up in a book, from where it is sent to the abomasum and further to the intestine.

In mammals, the small and large intestines are clearly distinguishable. In typical cases, the first consists of three parts: duodenum, jejunum and ileum. The duodenum is so named because its length in humans approximately corresponds to the total width of 12 fingers (20–30 cm). The human jejunum is approximately 2.4 m long, and the ileum is approx. 3.4 m. There are no clear boundaries between these departments. In the jejunum, food is mainly digested, and in the ileum, absorption occurs.

The large intestine consists of the cecum, colon and rectum; the latter ends with the anus. The cecum is a hollow outgrowth at the beginning of the large intestine. This variable formation, characteristic of mammals, was not inherited by them from reptilian ancestors, but developed during the evolution of the class as a place of accumulation of food that requires particularly long digestion. The cecum reaches its largest size in primitive herbivorous forms, which are characterized by its large hollow protrusion - a vermiform appendix (appendix). For a rabbit, this is a sac 36 cm long; in a pig, the blind tube is 90 cm long; in humans the appendix is ​​vestigial; the cat does not have it. The ileum is located at a right angle to the cecum. The main function of the colon is to retain the remains of digested food and remove as much water as possible from them. The rectum is always represented by a short straight tube that ends in the anus, surrounded by two rings of sphincter muscles. The first works involuntarily, the second - voluntarily.

Vascular system

The typical vascular system in higher groups of animals consists of two parts - circulatory and lymphatic. In the first of them, blood pumped by the heart circulates through a closed network of tubes (blood vessels - arteries, capillaries and veins): arteries carry blood from it, veins - to it. The lymphatic system includes lymph vessels, sacs, and glands (nodes). Lymph is a colorless liquid, similar in composition to blood plasma. Its source is liquid filtered through the walls of blood capillaries. It circulates in the intercellular spaces, enters the lymphatic vessels, and through them into the general bloodstream. The vascular system supplies all organs with nutrition and oxygen, while simultaneously removing waste products from them. The walls of lymphatic capillaries are more permeable than those of blood capillaries, so some substances, such as proteins, enter the lymph and are transported by it, and not by blood.

Invertebrates. Circulation in one form or another is characteristic of all animals. In ciliates (protozoa), digestive vacuoles move in the cytoplasm in approximately circles (so-called cyclosis). Flagellar collar cells push water through the sponge's body, allowing for respiration and filtering out food particles. Coelenterates do not have a special circulation system, but their digestive cavities diverge through channels to all parts of the body. In Hydra and many other cnidarians, they even extend into the tentacles. Thus, the body cavity plays a dual role here - digestive and circulatory.

Nemerteans are the most primitive modern animals with a true vascular system. It consists of three blood vessels that stretch along the entire body. In echinoderms, blood simply washes the vast body cavities. Annelids are characterized by red blood and the organs that pump it (the heart). Invertebrates have red blood: a red respiratory pigment, hemoglobin, is dissolved in its plasma. Squids, octopuses and some other mollusks and crustaceans have a different respiratory pigment - hemocyanin (gives the blood a blue color). An excellent vascular system with a complex network of arteries and veins and a well-developed heart is characteristic of mollusks. Arthropods also have a blood-pumping organ, which can be called a heart, but their circulatory system is not closed: the blood freely washes the spaces, or sinuses, inside the body, and the vessels are poorly developed, especially in insects. In the latter, the tracheal network frees the blood from the function of gas exchange.

Vertebrates. Lancelets are the only representatives of chordates that lack a heart, but the general layout of their primitive circulatory system is typical of higher groups.

In all vertebrates, the heart is located closer to the ventral side of the body. Blood is colored red by hemoglobin, which is contained in special cells (erythrocytes); plasma is colorless. Fish, with the exception of lungfish, are characterized by a two-chambered heart, consisting of an atrium and a ventricle. The ventricle pumps blood to the gills, where it becomes oxygenated and turns bright red (arterial). From there it flows to the head through the carotid arteries, and to the remaining parts through the dorsal aorta, which continues in the tail in the form of the caudal artery. Two pairs of large branches are separated from the aorta - the subclavian and iliac arteries. The former go to the pectoral fins and the body walls adjacent to them, the latter to the pelvic region and ventral fins. Other paired arteries supply blood to the back muscles, kidneys and reproductive organs. Unpaired arteries branching from the aorta go to the internal organs in the body cavity. The largest of them - the celiac - sends its branches to the swim bladder, liver, spleen, pancreas, stomach and intestines. The fact that the swim bladder in fish is supplied with blood differently from the lungs serves as an additional argument against recognizing these organs as homologous.

Having passed through the capillaries of all organs of the body, except the gills and lungs, the blood, losing oxygen, becomes dark (venous). From the head it enters the atrium through two large anterior cardinal veins. In sharks, it first fills the large venous sinus located immediately in front of the atrium. Venous blood flowing from the body and fins enters it through four pairs of large veins: subclavian (from the shoulder girdle and pectoral fins), lateral abdominal (from the side walls of the body and abdominal fins), hepatic (from the liver) and posterior cardinal (from the back and kidney).

In the abdominal cavity, the portal vein carries venous blood to the liver from the stomach, intestines and spleen. In fish, most of the blood from the tail vein passes through the kidneys on its way to the heart. As vertebrates evolve, less and less venous blood is sent to them. In amphibians it goes mainly to the liver. In mammals, venous blood from all parts of the body behind the shoulder girdle does not enter the kidneys, but moves directly to the heart through the posterior vena cava.

This is a large azygos vein that runs in the upper part of the abdominal cavity. It is absent in fish, with the exception of lungfish. In amphibians it is already well expressed and in the American proteus (Necturus) it functions along with the posterior cardinal veins. In tailless amphibians, reptiles, birds and mammals, the latter are reduced.

Heart. In typical fish, all the blood from their two-chambered heart is directed to the body through the gills. In lungfish and amphibians, after the appearance of the lungs, only part of the blood flows from the heart to the gills. In its upper left part a second atrium appears, receiving arterial (oxygen-rich) blood from the lungs; the heart becomes three-chambered. Its same structure is preserved in typical reptiles. However, in crocodiles a septum appears in the ventricle, dividing it into two parts, i.e. the heart turns into a 4-chambered one. It is the same in birds and mammals.

In animals with a 4-chambered heart, blood, making a full circle around the body, passes through the heart twice. From the head and the region of the shoulder girdle, it enters the right atrium through one or two anterior vena cava, and from other organs through the posterior vena cava. From the right atrium, blood enters the right ventricle and travels through the pulmonary arteries to the lungs. It returns from them through the pulmonary veins to the left atrium, from there it is pushed into the left ventricle, and from there it is distributed throughout the body along the aorta and its branches.

Aortic arches. If we count the squirter as the first gill slits, then modern sharks have six of them. In a typical embryo of any vertebrate, six arterial arches appear from the aorta; thus, this number can be considered as the initial number for the entire group, although the lancelet larva has 19, and some sharks have more than six. Modern sharks as adults have 5 pairs of gill arteries, which branch from the abdominal aorta and go to the gills, carrying blood to them from the heart. However, from the gills to the dorsal aorta, blood flows only through 4 pairs of gill arteries (the anterior one directs it to the head). In its middle part, each arterial arch breaks up into gill capillaries, dividing it into the afferent and efferent gill arteries. In typical bony fishes, only 4 pairs of aortic arches lead to the gills; there are the same number of efferent branchial arteries flowing into the dorsal aorta. In amphibians that retain gills, the first 3 of 6 arches are involved in the development of the internal and external carotid arteries. The same is observed in all higher animals, although in a greatly modified form. The fourth arches are large vessels that are the same on both sides of the body in amphibians, but different in reptiles. Birds do not develop a left aortic arch, while mammals do not develop a right one. The fifth arch disappeared along with the gill in adult frogs and toads. It is also absent in adult reptiles, birds and mammals. The outer end of the sixth arch also disappeared in almost all tetrapods, and its inner (closest to the heart) section turned into the pulmonary artery. In snakes, the left pulmonary artery is small or absent. In lungfishes and amphibians with gills, the pulmonary artery branches off from the preserved sixth arch.

Respiratory system

The main function of the respiratory system is to provide the body with oxygen and remove one of the oxidation products from it - carbon dioxide (carbon dioxide).

Invertebrates. Protozoa breathe across the entire surface of the cell. Coelenterates and sponges also lack a specialized respiratory system. Some annelids use gills, but generally they do not have respiratory structures. The body of some echinoderms is covered with numerous small dermal gills. Mollusks breathe either through gills or pulmonary sacs. Insects are characterized by tracheal tubes that penetrate their entire body. Crustaceans breathe through gills. Spiders use the so-called to breathe. pulmonary books with leaf-like gas exchange structures.

Vertebrates can breathe through gills, lungs, and through the surface of the skin.

Their gills are soft, thread-like outgrowths, abundantly washed with blood, in the wall of the gill slits leading from the pharynx to the sides of the body. Such pharyngeal gills are a unique feature of chordates. Huge in relation to the overall size of the body, the lancelet's pharynx is pierced by approximately 90 pairs of gill slits. Tunicates also have a similar pharyngeal chamber. Lampreys are characterized by 7 pairs of gill pouches, while hagfishes have from 6 to 14 pairs. The typical number of gill slits in fish is 5, although some primitive sharks have 7. In most sharks, another one, the anterior one, is modified in the squirter and noticeably separated from the rest. Ganoid fish also have a squirter.

In ancient times, one of the groups of primitive freshwater fish (lobe-finned fish) acquired lungs as additional respiratory organs. They arise in the embryo as a protrusion of the abdominal wall of the pharynx, which takes on a tubular shape, grows backward and bifurcates, turning into two hollow sacs. Later they move to the dorsal wall of the body cavity and are surrounded by a special membrane, the pleura. The lungs lie below the epithelial lining of this wall (as opposed to the swim bladder, which is located above it) and receive blood from the pulmonary artery, which arises from the sixth branchial arterial arch.

The swim bladder developed in the ancestors of modern bony fish. It arose as an unpaired protrusion of the upper wall of the pharynx and was eventually located along the entire body cavity above the lining of its dorsal wall, but below the kidneys (mesonephros). The swim bladder is supplied with blood not through the pulmonary artery, but through the celiac artery; The exception is mud fish (amiya). The listed differences between the lungs and the swim bladder indicate that they arose independently of each other and are non-homologous structures. However, the swim bladder is sometimes used as an additional organ of air respiration, especially in ganoids (mud fish, armored pikes and sturgeons). In African polypterus (Polypterus), the swim bladder is double, abdominal, necessary for breathing along with the gills and is served by the pulmonary arteries, i.e. is essentially lightweight. Cartilaginous fish have neither lungs nor swim bladders.

The tube leading from the ventral side of the pharynx to the lungs is retained in adult animals as the trachea. In lungfish and amphibians this is a short channel with soft walls, and in reptiles, birds and mammals it is a hard tube with cartilaginous rings in the walls that prevent it from collapsing.

The mammalian vocal chamber, the larynx, develops at the back of the pharynx at the entrance to the trachea and esophagus. In birds, the source of sounds produced is the additional lower larynx, located deep in the chest, where the trachea branches into two bronchi leading to the lungs. Thus, the vocal organs in birds and mammals are not homologous.

Amphibian larvae living in water develop 3 pairs of external gills of ectodermal origin, not entirely homologous to the internal gills of fish. The larvae of African and South American lungfish are equipped with 4 pairs of external gills, while the polyfin larva has only one. Amphibians at different stages of their lives can breathe through moist skin, external gills, internal gills and lungs. Frogs and salamanders lacking a thorax, i.e. not capable of costal respiratory movements, they push air into the lungs, as if swallowing it, and exhale by contracting the muscles of the abdominal wall. Turtles breathe in a similar way due to the immobility of their shell, but other reptiles, as well as birds and mammals, ventilate their lungs by rhythmically expanding and contracting the chest.

In birds, the lungs are directly connected to the chest. In addition, many air sacs extend from them, which are located between the internal organs and even in hollow bones. In mammals, the lungs are suspended freely in the chest cavity and fill as pressure drops in them. This cavity is separated from the abdominal cavity by a unique flat muscle, the diaphragm, which in a relaxed state forms a dome directed towards the head. Contracting during inhalation, it flattens, thereby enlarging the chest cavity and creating the pressure difference necessary for inhalation.

Excretory system

The excretory system removes metabolic waste from the body. Excretion products can be undigested food, sweat, carbon dioxide, bile (from the liver) or urine produced in the kidneys. Here only the kidneys and functionally related structures will be considered, i.e. specialized excretory organs of vertebrates.

Invertebrates. Excretion in protozoa is ensured by contractile vacuoles. In flatworms and some other invertebrates, primitive nephridia, or protonephridia, consisting of large “flame” cells and associated tubules, are used for this purpose. “Flame” cells function simultaneously as a filter and as a “motor” that ensures the flow of liquid excreta through the excretory system: metabolic waste and water enter them from the surrounding tissues, and they drive the resulting fluid into the tubules and further along the ducts to the excretory pores. In the recess of each “flame” cell there is a bunch of cilia (“flickering flame”), the beating of which drives liquid excrement through the excretory tubes from the body. In annelids, the excretory system is represented by nephridia of another type - the so-called. metanephridia. These are paired, metamerically located tubules, usually long and convoluted; one end of each tubule opens with a ciliated funnel into the coelomic cavity of the previous body segment, and the other - outward. The beating of the cilia creates a flow of fluid through the tubule, and as it moves, urine is formed. The excretory system of terrestrial invertebrates is structured differently. Their liquid excretory products exit through the Malpighian vessels into the hindgut, where water is absorbed; dehydrated excreta is expelled through the anus. This system allows you to reduce water loss by the body.

Vertebrates. In vertebrates, three types of kidneys appear successively: pronephros, mesonephros, and metanephros. The pronephros develops in the early embryo in the form of a cluster of a few tubes - nephrons (renal tubules) - along the anterior-superior part of the inner wall of the body cavity. From these, urine enters the primary ureter, called the pronephric, or Wolffian, canal. In all vertebrates, except hagfish, the pronephros functions only temporarily. Following this, similar but more complex tubes of the mesonephros are formed, which in fish and amphibians becomes a functional kidney. At the same time, the Wolffian canal is still used to excrete urine into the external environment or into the cloaca. In reptiles, birds and mammals, the third type of kidney, or metanephros, develops behind the mesonephros. It is even more complex histologically, works more efficiently and forms its own excretory channel, the secondary ureter. The Wolffian canal is preserved in males for the removal of sperm, but degenerates in females. Some reptiles (such as snakes and crocodiles) and birds do not have a bladder, and their ureters open directly into the cloaca. In mammals, they lead to the bladder, from which urine is excreted through the unpaired duct - the urethra. All animals, with the exception of oviparous animals, lack a cloaca.

Mesonephros of fish are long ribbons running along the dorsal side of the body cavity between the swim bladder and the bases of the ribs. In amphibians they are more compact and attached to the body wall by the mesentery. In snakes, the kidneys are very elongated and divided into lobules. In birds they are densely packed in paired cavities of the pelvic bones. In mammals they are bean-shaped or lobed. The kidneys of all gnathostomes, except mammals, are supplied with blood flowing through both arteries and veins; the latter form gate systems there. The portal system is the second network of capillaries that receives blood on its way from the dorsal aorta to the heart. It is always located in glandular organs, such as the liver, adrenal glands or kidneys. In mammals, kidney function requires high blood pressure, and it enters them only from the arteries.

BREEDING SYSTEM

The reproductive organs (gonads) are the testes of males and the ovaries of females. Within the animal kingdom, one can find many specialized variants of the structure of both these organs themselves and the ducts that carry their products out of the body.

Vertebrates. If the lancelet's gonads, located segmentally on both sides of the body cavity, are devoid of ducts, then all higher vertebrates have reproductive ducts, often quite complexly arranged.

In sharks, large paired gonads are located in front near the dorsal side of the body cavity. The eggs are also large and after fertilization or develop in special chambers of the oviducts, the so-called. uterus, or are deposited in water, covered with a dense protective shell. The embryonic stage takes quite a long time, and by the time of birth or hatching, sharks manage to reach quite large sizes. In bony fishes and amphibians, the ovaries are relatively large; in a typical case, many small, shell-less eggs are swept into the water, where fertilization occurs. Reptiles and birds lay large, shell-covered eggs. In female birds, the ovary and oviduct develop only on the left side of the body, but in males both testes are retained. Some snakes and lizards give birth to live young, but most reptiles lay eggs, almost always burying them in the ground. The excretion of reproductive products or the birth of young in most vertebrates occurs through the cloaca, but in typical bony fish and mammals a separate opening is used for this.

All tetrapods and some fish have a channel for the exit of sperm from the testes, i.e. The vas deferens serves as the Wolffian canal, i.e. primary ureter protonephros. In females of higher vertebrates, the same channels as in sharks continue to function as oviducts, although with significant changes. In all vertebrates, except mammals and bony fishes, they open into the cloaca separately. In evolutionarily advanced mammals, both oviducts are, to one degree or another, united and form an unpaired chamber for bearing the baby - the uterus.

During the evolution of vertebrates, their gonads increasingly move towards the posterior end of the abdominal cavity. In many mammals, the testes migrate from it to a special sac, the scrotum.

Endocrine glands

Animal glands can be divided into two categories - with excretory ducts (exocrine) and without them. In the second case, the released products enter the blood. Such glands are called endocrine, or endocrine glands. Many exocrine glands are located in the skin and secrete their secretions onto its surface (sometimes there are practically no formed ducts here). These include, for example, mucous, sebaceous, poisonous, sweat, mammary glands, and the coccygeal gland of birds. Inside the body of vertebrates there are exocrine glands such as the salivary, pancreas, prostate, liver and gonads. Some glands, such as the pancreas, ovaries, and testes, function as both glands at the same time.

Endocrine glands secrete hormones that, together with the nervous system, coordinate the work of different parts of the body. In humans, this category includes the pineal gland (epiphysis), pituitary gland, thyroid gland, parathyroid glands, thymus gland, secretin-producing cells of the duodenum, islets of Langerhans in the pancreas, adrenal glands, testes and ovaries.

The pituitary gland has a dual origin. During its formation, a protrusion grows down from the base of the diencephalon, which meets the upward-directed outgrowth of the roof of the oral cavity and forms a single whole with it. The pituitary gland produces several hormones and is present in all vertebrates. In sharks this is a large lobular gland.

Thyroid and parathyroid glands. The bilobed thyroid gland develops from an outgrowth of the pharyngeal fundus and is present in all vertebrates, starting with fish. The intensity of metabolism and the level of heat production, the condition of the skin and its derivatives, as well as molting processes in those animals to which it is characteristic depend. The parathyroid glands also develop from the wall of the pharynx. Their number varies in different vertebrates from 2 to 6. In humans there are 4, immersed in the posterior surface of the thyroid gland. They are involved in the regulation of calcium metabolism in the body.

Thyroid and pancreas. The thymus gland also develops from the embryonic pharynx, and in lower vertebrates it is one of the cervical glands. In mammals, it moves to the front of the chest. Its size is relatively large in newborns and young animals, and gradually decreases in adults. It plays an important role in the body's immune defense.

The pancreas contains two types of secretory cells: exocrine, which produce digestive enzymes, and endocrine, which secrete the hormone insulin. In cyclostomes, these cells exist separately. The pancreas first appears as a single organ in fish.

The adrenal glands are dual in nature and consist of two tissues, each of which secretes its own hormones. Their internal (brain) part develops from the nervous tissue of the embryo and secretes adrenaline. In lower vertebrates it can be distributed along the upper wall of the body cavity, remaining separate. The outer layer (cortex) of the adrenal glands secretes corticosteroids.

The gonads produce three important hormones: testosterone (in the testes), estrogens (in the ovaries and placenta) and progesterone (in the corpus luteum of the ovary). Testosterone and estrogens stimulate the development of secondary sexual characteristics, male and female, respectively. All female sex hormones together control the sexual cycle. However, in females the physiology of sex is under triple control of the pituitary gland, thyroid gland and gonads. and other articles on the anatomy of organs and various groups of animals.

Biology is one of the largest and largest sciences in the modern world. It includes a number of different sciences and sections, each of which studies certain mechanisms in the functioning of living systems, their vital functions, structure, molecular structure, and so on.

One of these sciences is the interesting, very ancient, but still relevant science of anatomy.

What does he study?

Anatomy is a science that studies the internal structure and morphological characteristics of the human body, as well as human development in the process of phylogenesis, ontogenesis and anthropogenesis.

The subject of studying anatomy is:

• the shape of the human body and all its organs;
• structure of human organs and body;
• origin of people;
• individual development of each organism (ontogenesis).

The object of study of this science is man and all his external and internal structural features.

Anatomy itself as a science developed a very long time ago, since interest in the structure and functioning of internal organs has always been relevant for humans. However, modern anatomy includes a number of related sections that are closely related to it and are considered, as a rule, comprehensively. These are such sections of anatomy as:

1. Systematic anatomy.
2. Topographical or surgical.
3. Dynamic.
4. Plastic.
5. Age.
6. Comparative.
7. Pathological.
8. Clinical.

Thus, human anatomy is a science that studies everything that in any way relates to the structure of the human body and its physiological processes. In addition, this science is closely connected and interacts with such sciences that have spun off from it and have become independent, such as:

• Anthropology is the study of man as such, his position in the system of the organic world and interaction with society and the environment. Social and biological characteristics of a human being, consciousness, psyche, character, behavior.
• Physiology is the science of all processes occurring inside the human body (mechanisms of sleep and wakefulness, inhibition and excitation, nerve impulses and their conduction, humoral and nervous regulation, and so on).
• Comparative anatomy - studies the embryonic development and structure of various organs, as well as their systems, while comparing animal embryos of different classes and taxa.
• Evolutionary doctrine is the doctrine of the origin and formation of man from the time of his appearance on the planet to the present day (phylogeny), as well as proof of the unity of all the biomass of our planet.
• Genetics - the study of the human genetic code, the mechanisms of storage and transmission of hereditary information from generation to generation.

As a result, we see that human anatomy is a completely harmonious, complex combination of many sciences. Thanks to their work, people know a lot about the human body and all its mechanisms.

History of the development of anatomy

Anatomy finds its roots in ancient times. After all, from the very appearance of man, he was interested in knowing what was inside him, why, if he gets hurt, blood comes out, what it is, why a person breathes, sleeps, eats. All these questions have haunted many representatives of the human race since ancient times.

However, answers to them did not come immediately. It took more than one century to accumulate a sufficient amount of theoretical and practical knowledge and to give a complete and detailed answer to most questions about the functioning of the human body.

The history of the development of anatomy is conventionally divided into three main periods:

• anatomy of the ancient world;
• anatomy of the Middle Ages;
• new time.

Let's look at each stage in more detail.

Ancient world

The peoples who became the founders of the science of anatomy, the first people interested in and describing the structure of human internal organs, were the ancient Greeks, Romans, Egyptians and Persians. Representatives of these very civilizations gave rise to anatomy as a science, comparative anatomy and embryology, as well as evolution and psychology. Let's look at their contribution in detail in the form of a table.

Time frame	Scientist	Discovery (contribution)
Ancient Egypt and Ancient China XXX - III centuries. BC e.	Doctor Imhotep	He was the first to describe the brain, heart, and the movement of blood through the vessels. He made his discoveries based on autopsies during the mummification of the corpses of pharaohs.
	Chinese book "Neijing"	Human organs such as liver, lungs, kidneys, heart, stomach, skin, and brain are described.
	Indian scripture "Ayurveda"	A fairly detailed description of the muscles of the human body, descriptions of the brain, spinal cord and canal, types of temperaments are defined, and types of figures (physiques) are characterized.
Ancient Rome 300-130 BC e.	Herophilus	The first who dissected corpses to study the structure of the body. He created a descriptive and morphological work "Anatomy". Considered the father of the science of anatomy.
	Erasistratus	He believed that everything consists of small particles, not liquids. He studied the nervous system by dissecting the corpses of criminals.
	Doctor Rufiy	He described many organs and gave them names, studied the optic nerves, and drew a direct relationship between the brain and nerves.
	Marin	He created descriptions of the palatine, auditory, vocal and facial nerves, and some parts of the gastrointestinal tract. In total he wrote about 20 essays, the originals of which have not survived.
	Galen	He created more than 400 works, 83 of which were devoted to descriptive and comparative anatomy. He studied wounds and the internal structure of the body on the corpses of gladiators and animals. Doctors were trained on his works for about 13 centuries. The main mistake was in theological views on medicine.
	Celsus	He introduced medical terminology, invented a ligature for ligating blood vessels, studied and described the basics of pathology, diet, hygiene, and surgery.
Persia (908-1037)	Avicenna	The human body is controlled by four main organs: the heart, testicle, liver and brain. He created a great work, “The Canon of Medical Science.”
Ancient Greece VIII-III centuries. BC e.	Euripides	Using animals and corpses of criminals, he was able to study the portal vein of the liver and describe it.
	Anaxagoras	Described the lateral ventricles of the brain
	Aristophanes	Discovered the presence of two meninges
	Empedocles	Described the ear labyrinth
	Alcmaeon	Described the ear tube and optic nerve
	Diogenes	Described many organs and parts of the circulatory system
	Hippocrates	He created the doctrine of blood, mucus, yellow and black bile as the four fundamental fluids of the human body. A great doctor, his works are still used today. Recognized observation and experience, denied theology.
	Aristotle	400 works from various branches of biology, including anatomy. He created many works, considered the soul to be the basis of all living things, and spoke about the similarities of all animals. Drew a conclusion about the hierarchy in the origin of animals and humans.

Middle Ages

This period is characterized by devastation and decline in the development of any sciences, as well as the dominance of the church, which prohibited dissections, research and the study of anatomy on animals, considering it a sin. Therefore, no significant changes and discoveries were made at this time.

But the Renaissance, on the contrary, gave many impetus to the modern state of medicine and anatomy. The main contributions were made by three scientists:

1. Leonardo da Vinci. He can be considered the founder of his artistic talents for the benefit of anatomy, created over 700 drawings accurately depicting muscles and skeleton. The anatomy of organs and their topography are shown to them clearly and correctly. I studied for work
2. Jacob Silvius. Teacher of many anatomists of his time. He opened grooves in the structure of the brain.
3. Andeas Vesalius. A very talented doctor who has devoted many years to a thorough study of anatomy. He made his observations based on autopsies of corpses, and learned a lot about the bones from materials collected at the cemetery. The work of his entire life is the seven-volume book “On the Structure of the Human Body.” His works caused opposition among the masses, since in his understanding anatomy is a science that should be studied in practice. This contradicted the works of Galen, which were held in high esteem at that time.
4. His main work was the treatise “Anatomical study of the movement of the heart and blood in animals.” He was the first to prove that blood moves through a closed circle of vessels, from large to small through tiny tubes. He also made the first statement that every animal develops from an egg and in the process of its development repeats the entire historical development of living things as a whole (modern biogenetic law).
5. Fallopius, Eustachius, Willis, Glisson, Azelli, Pequet, Bertolini are the names of those scientists of this era who, through their works, gave a complete understanding of what human anatomy is. This is an invaluable contribution that gave rise to a modern start in the development of this science.

New time

This period dates back to the 19th - 20th centuries and is characterized by a number of very important discoveries. All of them could be accomplished thanks to the invention of the microscope. Marcello Malpighi supplemented and substantiated practically what Harvey had predicted in his time - the presence of capillaries. The scientist Shumlyansky confirmed this with his work, and also proved the cyclicality and closedness of the circulatory system.

Also, a number of discoveries made it possible to reveal the concept of “anatomy” in more detail. These were the following works:

• Galvani Luigi. This man made a huge contribution to the development of physics, since he discovered electricity. However, he was also able to examine the presence of electrical impulses in animal tissues. Thus he became the founder of electrophysiology.
• Kaspar Wolf. He refuted the theory of preformationism, which stated that all organs exist in a reduced form in the reproductive cell, and then simply grow. Became the founder of embryogenesis.
• Louis Pasteur. As a result of many years of experiments, he proved the existence of bacteria. Developed vaccination methods.
• Jean Baptiste Lamarck. He made a huge contribution to evolutionary teachings. He was the first to express the idea that man, like all living things, develops under the influence of the environment.
• Karl Baer. He discovered the reproductive cell of the female body, described it and gave rise to the development of knowledge about ontogenesis.
• Charles Darwin. He made a huge contribution to the development of evolutionary teachings and explained the origin of man. He also proved the unity of all life on the planet.
• Pirogov, Mechnikov, Sechenov, Pavlov, Botkin, Ukhtomsky, Burdenko are the names of Russian scientists of the 19th-20th centuries who gave a complete understanding that anatomy is a whole science, complex, multifaceted and all-encompassing. Medicine owes their work in many respects. It was they who became the discoverers of the mechanisms of immunity, higher nervous activity, the spinal cord and nervous regulation, as well as many issues of genetics. Severtsov founded a direction in anatomy - evolutionary morphology, which was based on the basis (authors - Haeckel, Darwin, Kovalevsky, Baer, ​​Muller).

Anatomy owes its development to all these people. Biology is a whole complex of sciences, but anatomy is the oldest and most valuable of them, since it affects the most important thing - human health.

What is clinical anatomy

Clinical anatomy is an intermediate section between topographic and surgical anatomy. It considers the issues of the general plan structure of any specific organ. For example, if we are talking about the larynx, then before the operation the doctor needs to know the general position of this organ in the body, what it is connected to and how it interacts with other organs.

Today, clinical anatomy is very widespread. You can often find the expression clinical anatomy of the nose, pharynx, throat or any other organ. Clinical anatomy will tell you what components a given organ is made of, where it is located, what it borders on, what role it plays, and so on.

Each specialist doctor knows the full clinical anatomy of the organ he is working on. This is the key to successful treatment.

Age anatomy

Age anatomy is a section of this science that studies human ontogenesis. That is, it considers all the processes that accompany it from the moment of conception and the stage of the embryo until the end of the life cycle - death. At the same time, the main foundation for age-related anatomy is gerontology and embryology.

Karl Bar can be considered the founder of this section of anatomy. It was he who first suggested the individual development of each living creature. Later this process was called ontogeny.

Age-related anatomy provides insight into the mechanisms of aging, which is important for medicine.

Comparative anatomy

Comparative anatomy is a science whose main task is to prove the unity of all life on the planet. Specifically, this science is concerned with comparing embryos of different animal species (not only species, but also classes and taxa) and identifying general patterns in development.

Comparative anatomy and physiology are closely related entities that study one common question: how do embryos of different creatures look and function in comparison to each other?

Pathological anatomy

Pathological anatomy is a scientific discipline that deals with the study of pathological processes in the cells and tissues of a human being. This makes it possible to study various diseases, view the impact of their course on the body and, accordingly, find treatment methods.

The tasks of pathological anatomy are as follows:

• study the causes of various diseases in humans;
• consider the mechanisms of their occurrence and progression at the cellular level;
• identify all possible complications of pathologies and variants of disease outcome;
• study the mechanisms of death from diseases;
• consider the reasons for the ineffectiveness of treatment of pathologies.

The founder of this discipline is the one who created the cellular theory, which speaks about the development of diseases at the level of cells and tissues of the human body.

Topographic anatomy

Topographic anatomy is a scientific discipline, otherwise called surgical. It is based on the division of the human body into anatomical regions, each of which is located in a specific part of the body: the head, torso or limbs.

The main objectives of this science are:

• detailed structure of each area;
• syntopy of organs (their location relative to each other);
• connection of organs with skin (holotopia);
• blood supply to each anatomical region;
• lymphatic drainage;
• nervous regulation;
• skeletotopia (in relation to the skeleton).

All these tasks are formed in terms of the principles: study taking into account diseases, pathologies, age and individual characteristics of organisms.

Animals. In the 17th century, one of the earliest treatises on comparative anatomy was the treatise “Democritus Zootomy” (1645) by the Italian anatomist and zoologist M.A. Severino. At the beginning of the 19th century, Georges Cuvier summarized the accumulated materials in a five-volume monograph, Lectures on Comparative Anatomy, published in 1800-1805. Karl Baer also worked in the field of comparative anatomy, establishing the law of similarity of embryos. Materials accumulated since the time of Aristotle were some of the first evidence of evolution used by Charles Darwin in his work. In the 19th century, comparative anatomy, embryology and paleontology became the most important pillars of evolutionary theory. In the field of comparative anatomy, the works of Muller and Haeckel were published, who developed the doctrine of the recapitulation of organs in ontogenesis - the Biogenetic Law. In Soviet times, academician worked in the field of comparative anatomy. Severtsov, Shmalhausen and their followers.

Homologous and similar organs

In comparative anatomy the following concepts are often used:

1. Homologous organs are similar structures in different species that have a common ancestor. Homologous organs can perform different functions. For example, dolphin fins, tiger paws and bat wings. The presence of homologous organs indicates that the common ancestor had an original organ that changed depending on the environment.
2. Analogous organs are similar structures in different species that do not have a common ancestor. Similar organs have a similar function, but have different origins and structures. Similar structures include the body shape of dolphins and sharks, which evolved under similar conditions but had different ancestors; wing of a bird, fish and mosquito; human eye, squid and dragonfly. Analogous organs are examples of the adaptation of organs of different origin to similar environmental conditions.

The rules for the development of private characteristics were first described by Karl Baer.

Literature

• Shimkevich V.M., Course of comparative anatomy of vertebrate animals, 3rd ed., M. - P., 1922;
• Dogel V. A., Comparative anatomy of invertebrates, L., parts 1-2, 1938-40;
• Shmalgauzen I.I., Fundamentals of comparative anatomy of vertebrate animals, 4th ed., M., 1947;
• Severtsov A.N., Morphological patterns of evolution. Collection Op. , vol. 5, M. - L., 1949;
• Blyakher L. Ya., Essay on the history of animal morphology, M., 1962;
• Beklemishev V.N., Fundamentals of comparative anatomy of invertebrates, 3rd ed., parts 1-2, M., 1964;
• Development of biology in the USSR, M., 1967;
• Ivanov A.V., Origin of multicellular animals, Leningrad, 1968;
• History of biology from ancient times to the present day, M., 1972;
• Bronn's Klassen und Ordnungen des Thierreichs, Bd I - ,Lpz., 1859-;
• Gegenbaur C., Grundriss der vergleichenden Anatomie, 2 Aufl., Lpz., 1878;
• Lang A., Lehrbuch der vergleichenden Anatomie der wirbellosen Thiere, Bd 1-4, Jena, 1913-21;
• Handbuchder Zoologie, gegr. von W. Kukenthal, Bd I - ,B. - Lpz., 1923-;
• Handbuch der vergleichenden Anatomie der Wirbelthiere, Bd 1-6, V. - W., 1931-39;
• Traite de zoologie, publ, par P.P. Grasse, t. 1-17, P., 1948-;
• Cole F.J. A History of comparative anatomy from Arisotle to eighteenth century. London, 1944.
• Remane A., Die Grundlagen des natlirlichen Systems der vergleichenden Anatomie und der Phylogenetik, 2 Aufl., Lpz., 1956.
• Schmitt, Stéphane (2006). Aux origines de la biologie moderne. L'anatomie comparée d'Aristote à la théorie de l'évolution. Paris: Éditions Belin. ISBN.

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See what “Comparative Anatomy” is in other dictionaries:

COMPARATIVE ANATOMY- deals with the comparative study of animal organs and 43S establishes their morphology. similarity based on their common origin (homology). Thus S. a. makes it possible to establish the historical nature (phylogeny) of family ties...

Comparative anatomy- (anatomia comparativa) is not essentially a special science, but a method. Its content is the same as that of zoology, but in S. anatomy the factual material is presented in a different order. S. anatomy, choosing one or another organ, monitors its modifications in everyone... Encyclopedic Dictionary F.A. Brockhaus and I.A. Ephron

Comparative anatomy- a section of morphology and anatomy that studies the patterns of development and structure of organs and their systems by comparing different objects (for example, animals from different systematic groups). Some tasks: obtaining new data for construction... ... Physical Anthropology. Illustrated explanatory dictionary.

COMPARATIVE ANATOMY- a section of plant anatomy, the task of which is the comparative study of representatives of various systematic groups (species, genera, etc.) to clarify their phylogenetic relationships and establish the homology of individual structures... Dictionary of botanical terms

Comparative animal anatomy- comparative morphology, a science that studies the patterns of structure and development of organs and their systems by comparing animals of different systematic groups. Comparing the structure of organs in connection with their functions makes it possible to understand... ... Great Soviet Encyclopedia

COMPARATIVE ANATOMY OF ANIMALS- comparative morphology, a section of animal morphology that studies the patterns of structure and development of organs and their systems by comparing animals of different systematics. groups. Comparing the structure of organs in connection with their functions makes it possible... ...

ANATOMY- (from the Greek ana tome dissection, dismemberment), a section of morphology that studies the form and structure of the department. organs, systems and the body as a whole. Basic method used in A., dissection method; They also use morphometry, radiography, etc. methods... ... Biological encyclopedic dictionary

ANATOMY- (from the Greek anatemno I dissect), originally denoted the knowledge that could be obtained by dissecting corpses; Later, the immediate and most important task of A. began to be considered the study of individual systems or mechanisms, from the totality of... ... Great Medical Encyclopedia

ANATOMY Modern encyclopedia

Anatomy- (from the Greek anatome dissection), the science of the structure (mainly internal) of the body, a section of morphology. There are animal anatomy, plant anatomy, human anatomy (the main sections are normal anatomy and pathological anatomy) and... ... Illustrated Encyclopedic Dictionary

Books

• Comparative anatomy of seeds. Volume 7. Dicotyledons. Lamiidae, Asteridae, The book is the seventh volume of a multi-volume publication on the anatomy of seeds of flowering plants. It examines the most important anatomical characteristics of seeds of 43 families of the subclass... Category: Botany Publisher: Nauka, Buy for 1335 rub.
• Comparative anatomy of invertebrates. Lower mollusks. Cephalopods. Kolchetsy, N.A. Zarenkov, This manual represents the third part of the author’s four-volume work devoted to a comparative analysis of the anatomy of invertebrates. The book examines the structure of lower mollusks,... Category: Textbooks for universities Publisher:

Rudiments- organs that were well developed in ancient evolutionary ancestors, and now they are underdeveloped, but have not completely disappeared yet, because evolution is very slow. For example, a whale has pelvic bones. In humans:

• body hair,
• third eyelid
• coccyx,
• muscle that moves the pinna,
• appendix and cecum,
• wisdom teeth.

Atavisms- organs that should be in a rudimentary state, but due to developmental disorders have reached a large size. A person has a hairy face, a soft tail, the ability to move the auricle, and multiple nipples. Differences between atavisms and rudiments: atavisms are deformities, and everyone has rudiments.

Homologous organs- externally different, because they are adapted to different conditions, but have a similar internal structure, since they arose from the same original organ in the process divergence. (Divergence is the process of divergence of characteristics.) Example: bat wings, human hand, whale flipper.

Similar bodies- externally similar, because they are adapted to the same conditions, but have a different structure, because they arose from different organs in the process convergence. Example: the eye of a person and an octopus, the wing of a butterfly and a bird.

Convergence is the process of convergence of characteristics in organisms exposed to the same conditions. Examples:

• aquatic animals of different classes (sharks, ichthyosaurs, dolphins) have a similar body shape;
• Fast running vertebrates have few fingers (horse, ostrich).

1. Establish a correspondence between an example of an evolutionary process and the ways in which it is achieved: 1) convergence, 2) divergence. Write numbers 1 and 2 in the correct order.
A) the forelimbs of a cat and the upper limbs of a chimpanzee
B) a bird's wing and a seal's flippers
B) an octopus tentacle and a human hand
D) penguin wing and shark fins
D) different types of mouthparts in insects
E) butterfly wing and bat wing

Answer

2. Establish a correspondence between the example and the process of macroevolution that it illustrates: 1) divergence, 2) convergence. Write numbers 1 and 2 in the order corresponding to the letters.
A) the presence of wings in birds and butterflies
B) coat color in gray and black rats
B) gill breathing in fish and crayfish
D) different shapes of beaks in great and tufted tits
D) the presence of burrowing limbs in moles and mole crickets
E) streamlined body shape in fish and dolphins

Answer

3. Establish a correspondence between animal organs and the evolutionary processes as a result of which these organs were formed: 1) divergence, 2) convergence. Write numbers 1 and 2 in the order corresponding to the letters.
A) limbs of a bee and a grasshopper
B) dolphin flippers and penguin wings
B) bird and butterfly wings
D) the forelimbs of a mole and a mole cricket insect
D) limbs of a hare and cat
E) the eyes of a squid and a dog

Answer

4. Establish a correspondence between animal organs and the evolutionary processes as a result of which these organs were formed: 1) convergence, 2) divergence. Write numbers 1 and 2 in the order corresponding to the letters.
A) limbs of a mole and a hare
B) butterfly and bird wings
B) eagle and penguin wings
D) human nails and tiger claws
D) gills of crab and fish

Answer

Choose one, the most correct option. The development of a small number of digits in the limbs of the horse and ostrich is an example
1) convergence
2) morphophysiological progress
3) geographical isolation
4) environmental insulation

Answer

Choose one, the most correct option. An example of a vestigial organ in humans is
1) cecum
2) multi-nipple
3) gill slits in the embryo
4) scalp

Answer

Choose three correct answers out of six and write down the numbers under which they are indicated. Rudiments include
1) human ear muscles
2) belt of the hind limbs of the whale
3) underdeveloped hair on the human body
4) gills in embryos of terrestrial vertebrates
5) multiple nipples in humans
6) elongated fangs in predators

Answer

Choose one, the most correct option. As a result of what evolutionary process aquatic animals of different classes (sharks, ichthyosaurs, dolphins) acquired a similar body shape
1) divergence
2) convergence
3) aromorphosis
4) degeneration

Answer

Choose one, the most correct option. Which pair of aquatic vertebrates supports the possibility of evolution based on convergent similarities?
1) blue whale and sperm whale
2) blue shark and bottlenose dolphin
3) fur seal and sea lion
4) European sturgeon and beluga

Answer

Choose one, the most correct option. The development of limbs of different structures in mammals belonging to different orders is an example
1) aromorphosis
2) idioadaptations
3) regeneration
4) convergence

Answer

Look at a picture of wings on different animals and determine: (A) what evolutionists call these organs, (B) what group of evolutionary evidence these organs belong to, and (C) what mechanism of evolution resulted in their formation.
1) homologous
2) embryological
3) convergence
4) divergence
5) comparative anatomical
6) similar
7) driving
8) paleontological

Answer

Establish a correspondence between examples of objects and methods of studying evolution in which these examples are used: 1) paleontological, 2) comparative anatomical. Write numbers 1 and 2 in the correct order.
A) cactus spines and barberry spines
B) remains of beast-toothed lizards
B) phylogenetic series of the horse
D) multiple nipples in humans
D) human appendix

Answer

Choose one, the most correct option. What sign in a person is considered an atavism?
1) grasping reflex
2) the presence of an appendix in the intestine
3) abundant hair
4) six-fingered limb

Answer

1. Establish a correspondence between the example and the type of organs: 1) Homologous organs 2) Similar organs. Write numbers 1 and 2 in the correct order.
A) Forearm of a frog and a chicken
B) Mouse legs and bat wings
B) Wings of a sparrow and wings of a locust
D) Whale fins and crayfish fins
D) Burrowing limbs of moles and mole crickets
E) Human hair and dog fur

Answer

2. Establish a correspondence between the forms of adaptation of organisms to their environment and the organs that they have formed: 1) homologous, 2) similar. Write numbers 1 and 2 in the order corresponding to the letters.
A) streamlined shape of the head of a shark and dolphin
B) owl wing and bat wing
C) a horse’s limb and a mole’s limb
D) human eye and octopus eye
D) carp fins and fur seal flippers

Answer

Establish a correspondence between the characteristics of organs and comparative anatomical evidence of evolution: 1) homologous organs, 2) similar organs. Write numbers 1 and 2 in the order corresponding to the letters.
A) lack of genetic relatedness
B) performing various functions
B) a single plan for the structure of five-fingered limbs
D) development from identical embryonic rudiments
D) formation under similar conditions

Answer

1. Establish a correspondence between the example and the sign: 1) rudiment, 2) atavism. Write numbers 1 and 2 in the order corresponding to the letters.
A) wisdom teeth
B) multi-nipple
B) muscles that move the auricle
D) tail
D) highly developed fangs

Answer

2. Establish a correspondence between the evolutionary characteristics of humans and their examples: 1) rudiment, 2) atavism. Write numbers 1 and 2 in the order corresponding to the letters.
A) muscles of the auricle
B) caudal vertebrae
B) facial hair
D) outer tail
D) vermiform appendix of the cecum

Answer

3. Establish a correspondence between the structural features of the human body and comparative anatomical evidence of its evolution: 1) atavisms, 2) rudiments. Write numbers 1 and 2 in the order corresponding to the letters.
A) folds of the nictitating membrane
B) accessory pairs of mammary glands
B) continuous hair on the body
D) underdeveloped ear muscles
D) appendix
E) caudal appendage

Answer

4. Establish a correspondence between the structures of the human body and evidence of evolution: 1) rudiment, 2 atavism. Write numbers 1 and 2 in the order corresponding to the letters.
A) ear muscles
B) appendix
B) coccygeal vertebrae
D) thick hair all over the body
D) multiple nipples
E) the rest of the third century

Answer

Consider the drawing depicting the inhabitants of the waters of different classes of vertebrates and determine (A) what type of evolutionary process the picture illustrates, (B) under what conditions this process occurs and (C) what results it leads to. For each lettered cell, select the appropriate term from the list provided. Write down the selected numbers in the order corresponding to the letters.
1) homologous organs
2) convergence
3) occurs in related groups of organisms that live and develop in heterogeneous environmental conditions
4) vestigial organs
5) occurs in the same conditions of existence of animals belonging to different systematic groups, which acquire similar structural features
6) similar bodies
7) divergence

Answer

Choose two correct answers out of five and write down the numbers under which they are indicated. The terms of evolutionary teaching include
1) divergence
2) monitoring
3) natural selection
4) plasmid
5) panspermia

Answer

Read the text. Select three sentences that indicate comparative anatomical methods for studying evolution. Write down the numbers under which they are indicated in the table. (1) Similar organs indicate the similarity of adaptations to the same environmental conditions in different organisms that arise during evolution. (2) Examples of homologous organs are the forelimbs of a whale, mole, and horse. (3) Rudiments are laid down during embryogenesis, but do not fully develop. (4) Embryos of different vertebrates within a phylum have a similar structure. (5) Currently, phylogenetic series have been compiled for elephants and rhinoceroses.

Answer

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