Why did single-pass get such a name. Oviparous mammal: a brief description, features, reproduction and species. Origin and diversity of mammals. Oviparous and true animals

The most primitive of modern mammals. Females lay 1 or 2 eggs, which are incubated in a pouch formed on the belly during the breeding season (echidnas) or “hatch” (platypus). The cubs are fed with milk, which is secreted in two glandular fields of the female's belly.

Teeth are available only in young animals or absent.

The average body temperature is lower than that of other mammals and varies between 25 and 36 degrees.

Monotremes live in forests, steppes, plains and mountains up to 2.5 thousand meters above sea level.

Distributed in Australia, New Guinea, Tasmania.

There are 2 families in the detachment: echidnas and platypuses.

Echidna family - Tachygloossidae

Platypus family - Ornitorhynchidae

The platypus is the only member of the family. Therefore, it makes no sense to describe the family of platypuses. The platypus was discovered at the very end of the 18th century. during the colonization of New South Wales. In the list of animals of this colony published in 1802, the platypus was first mentioned as “an amphibious animal from the genus of moles ... Its most curious quality is that it has a duck's beak instead of the usual mouth, allowing it to eat in the mud, like birds. ..". It was also noted that this animal digs a hole for itself with its claws. In 1799 Shaw and Nodder gave it a zoological name. The head of the platypus is round and smooth; there is no external ear. The front paws are strongly webbed, but the web that serves as an animal when swimming is folded when the platypus walks on land or if it needs claws to dig a hole. The webs on the hind legs are much less developed. The main role in digging and swimming is played by the front paws, the hind limbs are of great importance when moving on land. The platypus usually spends about two hours a day in the water. It feeds twice: early in the morning and in the evening twilight. He spends most of his time in his hole, on land. The platypus feeds on small aquatic animals. He stirs up the silt at the bottom of the reservoir with his beak and catches insects, crustaceans, worms and mollusks. Under water, he feels free, unless, of course, it is possible to catch his breath on the surface from time to time. Diving and rummaging in the silt, he is guided mainly by touch; his ears and eyes are protected by fur. On land, the platypus, in addition to touch, is guided by sight and hearing. Platypus burrows are located outside the water, including the entrance, located somewhere under the overhanging shore at a height of 1.2-3.6 m above the water level. Only an exceptionally high flood can flood the entrance to such a hole. An ordinary hole is a semicircular cave dug under the roots of trees, with two or more entrances. Every year, the platypus goes into a short winter hibernation, after which it has a breeding season. Male and female platypus meet in the water. The cubs are blind for 11 weeks, then their eyes open, but they remain in the hole for another 6 weeks. These babies, which feed only on milk, have teeth; as the animal grows, the milk teeth disappear and are replaced by simple horny plates. Only after 4 months, young platypuses go on their first brief excursion into the water, where they begin to clumsily search for food. The transition from dairy to adult nutrition is gradual. Platypuses are well tamed and live up to 10 years of age in captivity.

lesson type - combined

Methods: partially exploratory, problem presentation, reproductive, explanatory-illustrative.

Target: mastering the skills to apply biological knowledge in practical activities, use information about modern achievements in the field of biology; work with biological devices, tools, reference books; conduct observations of biological objects;

Tasks:

Educational: the formation of a cognitive culture, mastered in the process of educational activities, and aesthetic culture as an ability to have an emotional and valuable attitude towards objects of wildlife.

Developing: development of cognitive motives aimed at obtaining new knowledge about wildlife; cognitive qualities of the individual associated with the assimilation of the basics scientific knowledge, mastering the methods of studying nature, the formation of intellectual skills;

Educational: orientation in the system of moral norms and values: recognition of the high value of life in all its manifestations, the health of one's own and other people; ecological consciousness; education of love for nature;

Personal: understanding of responsibility for the quality of acquired knowledge; understanding the value of an adequate assessment of one's own achievements and capabilities;

cognitive: the ability to analyze and evaluate the impact of environmental factors, risk factors on health, the consequences of human activities in ecosystems, the impact of one's own actions on living organisms and ecosystems; focus on continuous development and self-development; ability to work with various sources information, convert it from one form to another, compare and analyze information, draw conclusions, prepare messages and presentations.

Regulatory: the ability to organize independently the execution of tasks, evaluate the correctness of the work, reflection of their activities.

Communicative: the formation of communicative competence in communication and cooperation with peers, understanding the characteristics of gender socialization in adolescence, socially useful, educational, research, creative and other activities.

Technologies : Health saving, problematic, developmental education, group activities

Activities (elements of content, control)

Formation of students' activity abilities and abilities to structure and systematize the studied subject content: collective work - study of the text and illustrative material, compilation of the table "Systematic groups of multicellular organisms" with the advisory assistance of expert students, followed by self-examination; pair or group performance of laboratory work with the advisory assistance of a teacher, followed by mutual verification; independent work on the studied material.

Planned results

subject

understand the meaning of biological terms;

describe the features of the structure and the main processes of life of animals of different systematic groups; compare the structural features of protozoa and multicellular animals;

recognize organs and systems of organs of animals of different systematic groups; compare and explain the reasons for similarities and differences;

to establish the relationship between the features of the structure of organs and the functions that they perform;

give examples of animals of different systematic groups;

to distinguish in figures, tables and natural objects the main systematic groups protozoa and multicellular animals;

characterize the direction of evolution of the animal world; give evidence of the evolution of the animal world;

Metasubject UUD

Cognitive:

to Work with different sources information, analyze and evaluate information, convert it from one form to another;

draw up abstracts, various types of plans (simple, complex, etc.), structure educational material, give definitions of concepts;

make observations, set up elementary experiments and explain the results obtained;

compare and classify, independently choosing criteria for the specified logical operations;

build logical reasoning, including the establishment of cause-and-effect relationships;

create schematic models highlighting the essential characteristics of objects;

identify possible sources of necessary information, search for information, analyze and evaluate its reliability;

Regulatory:

organize and plan your learning activities- determine the purpose of the work, the sequence of actions, set tasks, predict the results of the work;

independently put forward options for solving the tasks set, foresee the final results of the work, choose the means to achieve the goal;

work according to a plan, compare your actions with the goal and, if necessary, correct mistakes yourself;

own the basics of self-control and self-assessment for making decisions and making a conscious choice in educational and cognitive and educational and practical activities;

Communicative:

listen and engage in dialogue, participate in a collective discussion of problems;

integrate and build productive interaction with peers and adults;

adequately use speech means for discussion and argumentation of one's position, to compare different points of view, to argue one's point of view, to defend one's position.

Personal UUD

Formation and development of cognitive interest in the study of biology and the history of the development of knowledge about nature

Receptions: analysis, synthesis, conclusion, transfer of information from one type to another, generalization.

Basic concepts

Diversity of mammals, division into orders; general characteristics of units, the relationship of lifestyle and external structure. The importance of mammals in nature and human life, the protection of mammals.

During the classes

Knowledge update ( concentration of attention when learning new material)

Choose the correct answer in your opinion.

1. What is the common feature of all vertebrates?

the presence of a spine

habitation air-ground environment

multicellularity

2. How is the brain of vertebrates protected?

sink

shell

skull

3. How many types of vertebrates are there?

4. What is the special respiratory organ in fish?

leather

5. What are the respiratory organs of amphibians?

lungs and skin

6. What vertebrates first appeared on earth?

reptiles

Amphibians

7. How do reptiles reproduce?

give birth to cubs

spawn

lay eggs

8. What distinguishing feature birds?

inhabit the air-ground environment

body covered with feathers

only they lay eggs

9. Which group of vertebrates is the most organized on earth?

mammals

10. How do mammals differ from other vertebrates?

feed babies with milk

breathe with lungs

warm-blooded

Learning new material(teacher's story with elements of conversation)

Monotreme mammals: general characteristics, features and origin .

Amazing organisms that lay eggs and feed their young with milk are monotreme mammals. In our article, we will consider the systematics and features of the life of this class of animals. general characteristics class Mammals.

The class Mammals, or Beasts, includes the most highly organized representatives of the Chordata type. Their hallmark is the presence of mammary glands in females, the secret of which they feed their cubs. TO external features their structures include the location of the limbs under the body, the presence hairline and various derivatives of the skin: nails, claws, horns, hooves

Most mammals are also characterized by the presence of seven cervical vertebrae, a diaphragm, exclusively atmospheric breathing, a four-chambered heart, and the presence of a cortex in the brain.

Subclass of the First Beasts. This subclass of Mammals includes a single order called Monotremes.. They got this name due to the presence of a cloaca. This is one opening into which the ducts of the reproductive, digestive and urinary systems open. All these animals reproduce by laying eggs. How can animals with such features be representatives of the class Mammals? The answer is simple. They have mammary glands that open directly to the surface of the body, since monotremes do not have nipples. Newborns lick it off their skin. The primitive features of the structure, inherited from reptiles, are the absence of the cortex and convolutions in the brain, as well as the teeth, the function of which is performed by the horny plates. In addition, their body temperature fluctuates within certain limits depending on its changes in environment from +25 to +36 degrees. Such warm-bloodedness can be considered quite relative. The egg-laying of monotremes cannot be called real. It is often referred to as an incomplete live birth. The fact is that the eggs do not immediately leave the genital ducts of the animal, but linger there for a certain time. During this period, the embryo develops already by half. After leaving the cloaca, monotremes incubate eggs or carry them in a special leathery bag.

Mammals are monotremes: fossil species Paleontological finds of monotremes are rather few. They belong to the Miocene, Upper and Middle Pleistocene epochs. The oldest fossil of these animals is 123 million years old. Scientists have come to the conclusion that the fossil remains practically do not differ from modern species. Monotreme mammals, whose representatives are endemic, live only in Australia and on the adjacent islands: New Zealand, Guinea, Tasmania.

Echidnas First Beasts- represented by only a few species. The echidna is a monotreme mammal. Due to the fact that its body is covered with long hard needles, outwardly this animal resembles a hedgehog. In case of danger, the echidna curls up into a ball, thus protecting itself from enemies. The body of the animal is about 80 cm long, its front part is elongated and forms a small proboscis. Echidnas are nocturnal predators. During the day they rest, and at dusk they go hunting. Therefore, their eyesight is poorly developed, which is compensated by an excellent sense of smell. Echidnas have burrowing limbs. With the help of them and a sticky tongue, they extract invertebrates in the soil. Females usually lay a single egg, which they hatch in a skin fold.

prochidni These are also representatives of the class Mammals, detachment Monotremes. From their closest relatives, echidnas, they differ in a more elongated proboscis, as well as the presence of three fingers instead of five. Their needles are shorter, most of them hidden in the wool. But the limbs, on the contrary, are longer. Prochidnas are endemic to the island of New Guinea. The basis of the diet of these monotremes is earthworms and beetles. Like echidnas, they catch them with a sticky long tongue, on which numerous small hooks are located.

Platypus. This animal seems to have borrowed its body parts from other representatives of this kingdom. The platypus is adapted to a semi-aquatic lifestyle. Its body is covered with dense thick hair. It is very rigid and practically impermeable. This animal has a duck's beak and a beaver's tail. The fingers have swimming membranes and sharp claws. In males, horny spurs develop on the hind limbs, into which ducts of poisonous glands open. For a person, their secret is not fatal, but it can cause severe swelling, first of a certain area, and then of the entire limb.

No wonder the platypus is sometimes called "God's joke". According to legend, at the end of the creation of the world, the Creator had unused parts from various animals. From them he created the platypus. It is not just an Australian endemic. This is one of the symbols of the continent, the image of which is found even on the coins of this state. This mammal hunts well in the water. But it builds nests and burrows exclusively on land. He swims at a considerable speed, and grabs his prey almost at lightning speed - within 30 seconds. Therefore, aquatic animals have very few chances to hide from a predator. Thanks to valuable fur, the number of platypus has been significantly reduced. On this moment hunting them is prohibited.

V.V. Latyushin, E. A. Lamekhova. Biology. 7th grade. Workbook to the textbook by V.V. Latyushina, V.A. Shapkin "Biology. Animals. 7th grade". - M.: Bustard.

Zakharova N. Yu. Control and verification work in biology: to the textbook by V. V. Latyushin and V. A. Shapkin “Biology. Animals. Grade 7 "/ N. Yu. Zakharova. 2nd ed. - M.: Publishing house "Exam"

Presentation Hosting

Amazing organisms that lay eggs and feed their young with milk are monotreme mammals. In our article, we will consider the systematics and features of the life of this class of animals.

General characteristics of the class Mammals

The class Mammals, or Beasts, includes the most highly organized representatives of the Chordata type. Their characteristic feature is the presence of mammary glands in females, the secret of which they feed their cubs. The external features of their structure include the location of the limbs under the body, the presence of hair and various derivatives of the skin: nails, claws, horns, hooves.

Most mammals are also characterized by the presence of seven cervical vertebrae, a diaphragm, exclusively atmospheric breathing, a four-chambered heart, and the presence of a cortex in the brain.

Monotremes, marsupials, insectivores: the origin of the Mammals

Mammals differ significantly species diversity. Platypus, kangaroo, mole, dolphin, whale, monkey, man - all these are representatives of this class. All of them descended from ancient reptiles. The proof of this fact is the similarity of their embryonic development, the presence of cloaca and crow bones in some representatives, and the laying of eggs.

As a result evolutionary processes and further divergence, orders of mammals arose: monotremes, marsupials, insectivores. The origin of mammals, as well as their subsequent development, has led to the fact that at present given class occupies a dominant position in the system of the animal world. Its representatives have mastered both ground-air and aquatic environment a habitat.

Subclass Firstbeasts

This subclass of Mammals includes a single order called the Monotremes. They got this name due to the presence of a cloaca. This is one opening into which the ducts of the reproductive, digestive and urinary systems open. All reproduce by laying eggs.

How can animals with such features be representatives of the class Mammals? The answer is simple. They have mammary glands that open directly to the surface of the body, since monotremes do not have nipples. Newborns lick it off their skin.

The primitive features of the structure, inherited from reptiles, are the absence of the cortex and convolutions in the brain, as well as the teeth, the function of which is performed by the horny plates. In addition, their body temperature fluctuates within certain limits depending on its changes in the environment from +25 to +36 degrees. Such warm-bloodedness can be considered quite relative.

The egg-laying of monotremes cannot be called real. It is often referred to as an incomplete live birth. The fact is that the eggs do not immediately leave the genital ducts of the animal, but linger there for a certain time. During this period, the embryo develops already by half. After leaving the cloaca, monotremes incubate eggs or carry them in a special leathery bag.

Mammals are monotremes: fossil species

Paleontological finds of monotremes are rather few. They belong to the Miocene, Upper and Middle Pleistocene epochs. The oldest fossil of these animals is 123 million years old. Scientists have come to the conclusion that the fossil remains practically do not differ from modern species. Monotreme mammals, whose representatives are endemic, live only in Australia and on the adjacent islands: New Zealand, Guinea, Tasmania.

echidnas

Pervozveri - this is which is represented by only a few species. The echidna is a monotreme mammal. Due to the fact that its body is covered with long hard needles, outwardly this animal resembles a hedgehog. In case of danger, the echidna curls up into a ball, thus protecting itself from enemies. The body of the animal is about 80 cm long, its front part is elongated and forms a small proboscis. Echidnas are nocturnal predators. During the day they rest, and at dusk they go hunting. Therefore, their eyesight is poorly developed, which is compensated by an excellent sense of smell. Echidnas have burrowing limbs. With the help of them and a sticky tongue, they extract invertebrates in the soil. Females usually lay a single egg, which they hatch in a skin fold.

prochidni

These are also representatives of the class Mammals, detachment Monotremes. From their closest relatives, echidnas, they differ in a more elongated proboscis, as well as the presence of three fingers instead of five. Their needles are shorter, most of them hidden in the wool. But the limbs, on the contrary, are longer. Prochidnas are endemic to the island of New Guinea.

The basis of the diet of these monotremes is made up of earthworms and beetles. Like echidnas, they catch them with a sticky long tongue, on which numerous small hooks are located.

Platypus

This animal seems to have borrowed its body parts from other representatives of this kingdom. The platypus is adapted to a semi-aquatic lifestyle. Its body is covered with dense thick hair. It is very rigid and practically impermeable. This animal has a duck's beak and a beaver's tail. The fingers have swimming membranes and sharp claws. In males, horny spurs develop on the hind limbs, into which ducts of poisonous glands open. For a person, their secret is not fatal, but it can cause severe swelling, first of a certain area, and then of the entire limb.

No wonder the platypus is sometimes called "God's joke". According to legend, at the end of the creation of the world, the Creator had unused parts from various animals. From them he created the platypus. It is not just an Australian endemic. This is one of the symbols of the continent, the image of which is found even on the coins of this state.

This mammal hunts well in the water. But it builds nests and burrows exclusively on land. This is not harmless. He swims at a considerable speed, and grabs his prey almost at lightning speed - within 30 seconds. Therefore, aquatic animals have very few chances to hide from a predator. Thanks to valuable fur, the number of platypus has been significantly reduced. At the moment, hunting for them is prohibited.

Subclass Real Beasts

Monotreme mammals are primarily characterized by the presence of a cloaca. Real animals have separate openings for the digestive, reproductive and urinary systems. In this subclass, marsupial and placental mammals are distinguished.

Order Marsupials

Representatives of this systematic unit have a leather bag on their belly. Some monotreme mammals also have this structural feature. But in marsupials, the ducts of the mammary glands open into it. Most of these animals live in Australia, but the opossum is also found in North America.

The most famous member of the marsupials is the kangaroo. This large mammal, which moves by jumping. Their length can reach up to 1.5 m. Thanks to well-developed hind limbs and tail, they move very quickly. Kangaroos can reach speeds up to 50 km/h. These herbivores are often attacked by various predators. They defend themselves with their hind limbs, leaning on their tail.

Lives in southern Australia marsupial bear, which is also called a koala. This cute animal sits motionless in the trees all day long. And at night he switches to an active lifestyle. The diet of koalas consists of leaves and young shoots of eucalyptus. These animals are quite greedy. They can eat up to a kilogram of food per day. Koala meat is inedible, but fur is of great value to humans. For this reason, this species was practically on the verge of extinction. IN given period This animal is listed in the International Red Book.

Marsupials have mastered several habitats. Most of them are terrestrial animals. Some live in trees. This is a koala and marsupial flying squirrel. Some species live underground. They include the opossum.

placental mammals

And marsupials are dioecious animals with internal fertilization. Placental representatives of this class have the most progressive structural features. They are the most widespread in nature. During embryonic development, they form a child's place or placenta. This is the organ that provides communication between the fetus and the mother's body. The placental gestation period ranges from 11 days in murine rodents to 24 months.

This group of mammals is represented by a large number of orders. So, representatives of insectivores are hedgehogs, moles, desmans, shrews, shrews. Their common feature is not only the nature of the food, but also appearance. The anterior part of the head of insectivores is elongated and forms a short proboscis, on which there are sensitive hairs.

Placentals have mastered all habitats, except for the organism. Chiropterans are capable of flight due to the presence of a skin fold between the fingers, which serves as their wing. Pinnipeds spend most of their lives in the water, and cetaceans live there all the time. Terrestrial placentals include Rodents, Lagomorphs, Parno- and Odd-hoofed, Carnivores and Primates. The man represents the last squad.

Mammals - monotremes, marsupials and placentals feed their young with milk. Each of the listed superclasses has its own character traits. In monotremes, a cloaca is preserved, in marsupials a skin fold is formed, in which a newborn develops for a certain period. All of them are endemic to Australia. Marsupials and monotremes do not have a placenta. Due to the presence of an organ that connects the body of the mother and child during fetal development, quite viable individuals are born. Therefore, placentals are the most highly organized representatives of the class.

"Grade 7 Reptiles" - Completed by a student of 7 "A" class Kurmasheva Malika. You don't like snakes? Missouri, USA. The sense organs are better adapted to the terrestrial way of life. . Order: turtles. A detachment of aquatic reptiles live in rivers, lakes and swamps. well developed ribs and rib cage. The modern representative is the tuatara.

"Mushrooms biology" - Riddle. fruit body. Proverbs and sayings. Plants. Porcini. Sprinkle the resulting hole with leaves and needles. - serve as food for animals; Mushroom rules. Diagram of the structure of a cap mushroom. - Some mushrooms are a medicine for animals and humans. 1. Carefully unscrew the mushroom. Lesson topic: Aspen. Leg.

"The structure of arthropods" - Class Arachnids (subclasses: Haymakers, Scorpions, Ticks, Spiders). Spiders-tarantulas. Orb-weaving spiders. Wolf spider. Presentation for 7th grade. General characteristics of the type. Type systematics. Class Crustaceans (subclasses Lower and Higher or Decapods). banana spiders. Jumping spiders. Type Arthropods. More than 1.5 million species; 2/3 of all kinds of living beings. Sidewalk spiders. Spider-haymaker. Crab spider.

"Mammals Grade 7" - Order Insectivores. Detachment Single pass. Eared hedgehog. Colony of water bats. At bats during hibernation the temperature drops to +1 - +5 degrees. Yes, I really p…….k! Mole ordinary. You recognized me? Bats are an ancient, morphologically primitive group of animals. Primates. In winter they hibernate.

"Lesson Reproduction of organisms" - Moon-fish. Amoeba division. Termite mound. Fish breeding. cartilaginous fish: stingray, shark. Teacher: Bobyleva N.P. Let's find out what biological role various ways reproduction and fertilization in nature. Lesson goals. Learn to Compare different types reproduction and fertilization. Malaria parasite in blood cells. Cleavage of vertebrate eggs. Reproduction of the liver fluke. Summary of the lesson.

• Class: Mammalia Linnaeus, 1758 = Mammals
• Infraclass: Prototheria = cloacal, primitive, oviparous
• Order Monotremata Bo
• Family: Ornithorhynchidae Burnett, 1830 = Platypuses
• Family: Tachyglossidae Gill, 1872 = Echidna

Order Monotremata Bo naparte, 1838 = Monotreme oviparous

A small group of the most primitive living mammals. Monotreme females lay 1 or 2, rarely 3 eggs of the telolecital type (a large amount of yolk is characteristic, the main mass of which is located at one of the poles of the egg). The hatching of the young from the eggs occurs with the help of a special egg "tooth", which is formed on a small ovoid bone (os carunculae). Young animals hatched from eggs are fed with milk. During the breeding season, a brood pouch can form on the belly of the female, in which the deferred matures. The dimensions of monotremes are small: body length is 30–80 cm. The head is small, with an elongated "beak", covered with a cornea. The eyes are small, the external auricles are barely visible or absent altogether. The body is covered with coarse hair and spines or soft thick fur. Vibrissae are absent. In the calcaneal region of the hind limbs there is a horny spur, which is especially strongly developed in males. The spur is pierced by a canal - a special duct associated with the so-called shin gland, the function of which is not entirely clear. Apparently, it has some significance in reproduction. It is also suggested (unconvincingly) that the secret of the shin gland is poisonous and the spur serves as a weapon of defense. Mammary glands are tubular. There are no true nipples, and the excretory ducts of the glands open separately from each other on two glandular fields of the female's belly.

The skull is flattened. The front section is elongated. The cartilaginous skull and the ratio of bones in the roof of the skull are to a certain extent similar to reptiles. Skull roof with anterofrontal and posterior frontal bones; the presence of these bones in the roof of the skull is the only case among mammals. The tympanic bone has the form of a flattened ring that does not fuse with the skull. The bony auditory meatus is absent. The malleus and incus in the middle ear fuse together and have a long process (processus folii). The lacrimal bone is absent. The zygomatic bone is greatly reduced in size or absent. Only monotremes among all mammals have a pre-vomer (praevomer). The premaxilla has a process similar to that of reptiles (processus ascendus); this is the only case among mammals. The articular fossa for the lower jaw is formed by the squamous bone. Lower jaw with only two weakly expressed processes - coronal and angular.

Teeth are present only in young animals or are completely absent. The shape of the teeth to a certain extent resembles the shape of the teeth of the Mesozoic Microleptidae. The skeleton of the forelimb girdle is characterized by a coracoid (coracoideum) and a procoracoid (procoracoi-deum) that are unique among mammals. In the presence of these bones, the similarity of the shoulder girdle of monotremes with the shoulder girdle of reptiles is manifested. Sternum with large breastplate (episternum). The clavicle is very large. Blade without comb. The humerus is short and powerful. The ulna is much longer than the radius. The wrist is short and wide. The fore and hind limbs are five-fingered. Fingers end in claws. In the pelvic girdle of males and females there are so-called marsupial bones (ossa marsupialia), which are attached to the pubic bones. Their function is unclear. The symphysis of the pelvic bones is greatly elongated. The proximal tibia with a large flattened process (peronecranon). The spinal column consists of 7 cervical, 15-17 thoracic, 2-3 lumbar, 2 sacral, 0-2 coccygeal and 11-20 caudal vertebrae. The whole body is covered with a highly developed layer of subcutaneous muscles (rap-niculus carnosus). Only in the region of the head, tail, limbs, cloaca and mammary glands, the subcutaneous muscles are not developed. The lower jaw has a musculus detrahens attached to it. inside; this is the only case in mammals. The larynx is primitive and does not have vocal cords.

The brain is generally large, has mammalian features, but retains a number of reptilian features. Large hemispheres with numerous, sometimes few furrows. The structure of the cerebral cortex is primitive. Olfactory lobes are very large. The cerebellum is only partially covered by the cerebral hemispheres. The corpus callosum (corpus callosum) is absent; it is presented only as commissura dorsalis. The sense of smell is highly developed. Jacobson's organ is well developed. The structure of the hearing organs is primitive. Eyes with or without nictitating membrane. The sclera has cartilage. The vascular membrane is thin. Musculus dilatatorius and Musculus ciliaris are absent. The retina has no blood vessels.

The salivary glands are small or large. The stomach is simple, without digestive glands, which is the only case in mammals. Its function appears to be food storage, similar to that of the crop of birds. The digestive tract is divided into small, large intestines, there is a caecum. The intestines open into the cloaca, which is present in both sexes. The liver is multilobed, with a gallbladder. The heart of monotremes has a structure characteristic of mammals, however, it also retains some reptile-like features, which consist, for example, in the fact that the right atrioventricular opening is equipped with only one valve.

The average body temperature is lower than that of other mammals (platypus on average 32.2 ° C, echidnas - 31.1 ° C). Body temperature can vary between 25° and 36°C. Bladder, into which the ureters flow, opens into the cloaca. The oviducts enter the cloaca separately (there is no vagina or uterus). The testicles are located in the abdominal cavity. The penis is fixed on the ventral wall of the cloaca and serves only to remove sperm.

Monotremes live in forests different type, in the steppes, overgrown with shrubs, on the plains and in the mountains, rising up to 2.5 thousand meters above sea level. They lead a semi-aquatic (platypus) or terrestrial (echidna) lifestyle; twilight and nocturnal activity; feed on insects and aquatic invertebrates. Life expectancy up to 30 years. Distributed in Australia, Tasmania, New Guinea. There are 2 families in the order: echidnas - Tachyglossidae Gill, 1872 platypuses - Ornithorhynchidae Burnett, 1830. In comparison with all other modern mammals, modern monotremes are closest to reptiles. However, they are not the ancestors of marsupials or placental mammals, but represent a separate specialized branch in the evolution of mammals.

Fossil remains of representatives of the monotreme order are known only from Australia. The most ancient finds date back to the Pleistocene and do not differ significantly from modern forms. There are two possible theories explaining the origin of the monotremes. According to one of them, monotremes developed independently and in complete isolation from other mammals, starting from the early period of the emergence of mammals, possibly from their reptile-like ancestors. According to another theory, a group of monotremes separated from the ancient marsupials and acquired its features due to specialization, retaining a number of features characteristic of marsupials, underwent degeneration and, possibly, to a certain extent, returned to the forms of their ancestors (reversion). The first of the theories seems more plausible. Significant differences in morphology between echidnas and platypus emerged in a relatively short period of time - starting from the upper Eocene. Echidnas are secondary land mammals, separated from ancient aquatic platypuses (Gregory, 1947).