Development of the baby in the uterus. Embryonic development of mammals

Animal reproduction and development

Most animals lay eggs or eggs. Animals give birth to cubs and feed them with milk. As they develop, the offspring turns into adult animals. Many parent animals care for their offspring.

Reproduction and development of insects
The nettle butterfly lays eggs on nettles. The eggs hatch into larvae. Butterfly larvae are called caterpillars. They look nothing like adult butterflies. The caterpillars feed on nettle leaves, grow quickly, and then turn into motionless pupae. A little time will pass, and an adult butterfly will emerge from each pupa.
Not all insects can have pupae. For example, grasshoppers do not have pupae. Their larvae are very similar to adult grasshoppers, only they are very small and do not have wings. Growing up, each larva sheds its skin several times. When this happens in last time, an adult insect emerges from the skin - large and with wings.

Reproduction and development of fish, amphibians and reptiles
In spring, female fish spawn eggs into the water. From the eggs emerge fry that are similar to adult fish, only very small. The fry feed, grow and gradually become adult animals.
In the spring in a pond, river, lake you can hear loud voices frogs and toads - real concerts! At this time, female frogs and toads lay eggs in the water. After a few days, the eggs hatch into tadpoles that look more like small fish than adult amphibians. Tadpoles live in water, feed, grow and gradually develop into adult frogs or toads.
Female lizards, snakes, turtles, and crocodiles lay eggs. The eggs hatch into small lizards, snakes, turtles, and crocodiles. They grow and gradually turn into adult animals.

Bird reproduction and development
Almost all birds build nests in the spring. Birds lay eggs in nests and incubate them - warming them with their warmth. Chicks emerge from the eggs. Some birds are already covered with down and very mobile, while others are helpless and naked. They grow quickly and need a lot of food. At the end of spring - beginning of summer, the chicks of many birds leave their nests.

Reproduction and development of animals
Animals, or mammals, give birth to young and feed them with milk.
Most mammals give birth to their young in the spring. For a fox they live in a hole, for a squirrel - in a hollow or in a nest in a tree. At the beaver's house - hut.
Most animals take care of their offspring: adults protect the cubs, and over time teach them to obtain food on their own.

What bird is the riddle talking about?

Who is this bird? Never
Doesn't build nests for itself,
Leaves eggs for neighbors
And he doesn’t remember the chicks.
Answer: Cuckoo

In what kind of houses do animals raise their offspring?

Consider the houses of some birds. Think about how they built them. Which bird did not build a house itself? Why?

WoodpeckersThey hollow out a new hollow in a tree trunk or clean and expand an existing one, but it is not large enough. A person will never see a woodpecker's nest on a green tree. These birds choose dead and diseased trees for their nests.
stork nest very large up to 1.5 m in diameter and can weigh up to 250 kg. It is usually found on the roofs of various human structures or on broken tree tops near wetlands. The nest has been used by the stork for more than one year, so it is built conscientiously and is annually repaired and updated. The height of a fresh nest reaches 40-50 cm, and old ones can be up to 1.5 meters high. The oldest nest is known in Germany, in which storks nested for 381 years in a row.
Martin builds his own nest from lumps damp earth. She finds earth in puddles, rolls them into balls, brings them in her beak to the construction site and firmly attaches them to the wall, gluing them with her own saliva. Barn Swallow for the strength of the structure, straws, stems, and horsehair are mixed into the soil.
Goldfinch builds nest very densely (cup-shaped) made of thin stalks of moss, lined inside with plant fluff (from the fruits of poplar, willow).
Starling people love it, it destroys many harmful insects, which benefits people. We are accustomed to the fact that starlings live in birdhouses.
Beregovushka- the smallest and most inconspicuously colored of our swallows. One of the birds that make nests in burrows and do not occupy other people’s homes, but dig them themselves. Even if last year’s home is intact, shore swallows still prefer to build a new one.

164) Look at the drawing. Label the names of the parts skin mammals, indicated by numbers.

I - epidermis

II - the skin itself

2) sebaceous gland

3) sweat gland.

165) What sense organs do mammals have?

Organs of touch - skin receptors; olfactory organ - nasal cavity; organ of taste - tongue; organ of vision - eyes; organ of hearing - ear.

1660 Study the table “Class Mammals. The structure of a rabbit." Look at the drawing. Write the names of the bones of the mammalian skeleton, indicated by numbers.

2) cervical vertebrae

3) thoracic vertebrae

4) caudal vertebrae

5) pelvic bones

9) chest

10) forearm

13) shoulder blade.

167) List the bones that make up the shoulder and pelvic girdle of mammals.

Shoulder girdle: paired shoulder blades and collarbones.

Pelvic girdle: paired iliac, ischial and pubic bones.

168) List the structural features of the skeleton associated with a terrestrial lifestyle.

1) The appearance of full-fledged limbs - paws built on the principle of levers ending in a hand with tenacious fingers - ensure effective movement on land. Belts of the limbs appear, and muscles are attached to them to ensure the movement of the paws.

2) Appearance cervical region spine - allows you to move your head in different directions, which contributes to better orientation in space

3) Bones become tubular - this gives increased strength and at the same time lightens the skeleton

4) Development of the jaw apparatus. Both herbivores and carnivores have a need for more careful processing of food. In this regard, differentiated teeth appear.

5) The number of cervical vertebrae is constant and equal to seven, the skull is more voluminous, which is associated with large sizes brain. The bones of the skull fuse quite late, allowing the brain to grow as the animal grows.

6) The limb is five-fingered. The methods of movement of mammals are different - walking, running, climbing, flying, digging, swimming - which is reflected in the structure of the limbs.

169) What are the structural features of the mammalian brain?

The mammalian brain has the same sections as the brains of other vertebrates, but is distinguished by its large size and very complex structure of the forebrain hemispheres. Their outer layer consists of nerve cells that form the cerebral cortex. It is in the cerebral cortex that the main processes of higher nervous activity. In more highly organized species of mammals, the cerebral cortex forms numerous convolutions and grooves, which sharply increases its area. The cerebellum and midbrain are well developed, since mammals are characterized by high motor activity and complex reflexes. The sense organs are distinguished by great complexity and perfection.

170) Study the table “Class Mammals. The structure of a rabbit." Look at the drawing. Write the names internal organs rabbit, indicated by numbers.

4) stomach

6) bladder

7) large intestine

8) small intestine

9) diaphragm

171) What is a diaphragm? What are its functions?

The diaphragm is an unpaired vastus muscle that separates the thoracic and abdominal cavities and serves to expand the lungs. Conventionally, its border can be drawn along the lower edge of the ribs. Formed by a system of striated muscles. Characteristic only of mammals.

172) Fill the table.

Mammalian organ systems.

Mammalian internal organ system	Organs	Functions
Muscular	muscles, diaphragm	active lifestyle and getting around
Sense organs	eyes, ears, skin and whiskers, tongue, nasal cavity	relationship with the environment
Digestive system	oral cavity, pharynx, esophagus, stomach, duodenum, intestines, rectum, anus	digestion
Respiratory system	nasal cavity, larynx, trachea, bronchi, alveolar lungs	gas exchange
Circulatory system	four-chambered heart, vessels (arteries, veins, capellars)	oxygen transport
Excretory system	kidneys, ureter, bladder, urethra	removal of harmful substances
Reproductive system	testes, vas deferens/ovaries, uterus, vagina	reproduction of one's own kind

173) Describe the function of the mammalian kidney.

The kidneys of mammals consist of an outer (cortical) and inner (medullary) layer. In the cortex there are convoluted tubules originating from Bowman's capsules, inside which there are glomeruli of blood vessels. The filtration process is carried out in them, and blood plasma is filtered into the renal tubules - primary urine is formed. The renal tubules form several knees, in which water, sugar and amino acids are reabsorbed from the primary urine - secondary urine is formed, which enters the collecting ducts, which form the medulla. The final product of protein metabolism is urea. Urine enters the ureters, then into the bladder and then through the urethra to the outside.

174) Draw a diagram of the structure of the mammalian heart and label its components.

175) Using the picture in the textbook on p. 236, describe how blood moves through blood vessels in mammals.

The pulmonary circulation begins in the right ventricle through the pulmonary trunk. Venous blood travels through the pulmonary trunk through the pulmonary arteries to the lungs. Enriched with oxygen in the lungs, the blood returns through the pulmonary veins to the left atrium, and from there enters the left ventricle.

The systemic circulation begins with the aorta, which emerges from the left ventricle. From there, the blood enters large vessels heading to the head, torso and limbs. Large vessels branch into small ones, which pass into intraorgan arteries, and then into arterioles and capillaries. Through capillaries, constant exchange of substances occurs between blood and tissues. The capillaries unite and merge into venules and veins, which merge into large venous vessels, forming the superior and inferior vena cava. Through them, blood returns to the right atrium.

176) What blood enters the right atrium?

Deoxygenated blood.

177) Look at the drawing and sign it. Describe how the baby develops in the uterus.

Fertilization is internal and occurs in the oviducts. During development, the placenta is formed in the uterus, through which a connection is established between the embryo and the mother’s body. As a result, gas exchange in the body of the embryo, its nutrition and removal of metabolic products are ensured. The duration of pregnancy depends on many factors: body size, readiness of the offspring for independent life etc. In some species, the cubs are born helpless, in others - capable of active action.

178) What is the placenta? What is its biological significance?

The placenta is an embryonic organ in all females placental mammals, some marsupials and a number of other groups of animals, allowing for the transfer of material between the circulatory systems of the fetus and mother.

1) Gas exchange

2) Excretory

3) Hormonal

4) Protective.

179) What is the structure of the reproductive system of mammals?

The reproductive system in males consists of paired testes, vas deferens, accessory glands and a copulatory organ. The testes (in which sperm are formed and mature) in most species are located in a special sac - the scrotum.
In females, the reproductive system consists of paired ovaries, oviducts, uterus and vagina. Oocytes are produced in the ovaries. As they mature, they are released and first enter the upper sections of the oviducts, where, as a rule, they are fertilized. The fertilized egg moves to the uterus, where, with the further development of the embryo, a child's place is formed - the placenta.

180) Provide evidence that mammals evolved from ancient reptiles.

Mammals have many similarities with reptiles, especially in embryonic development, skeletal structure, and horny integument. This suggests that mammals evolved from ancient reptiles. The similarity of adult animals with reptiles is also manifested in the abundance of horny skin formations in animals (fur, horns, hooves, claws, nails); presence of scales on the tails of mice, rats, beavers, similar to the scales of reptiles; in the similar development of these scales from the skin rudiments. The similarity with reptiles is especially noticeable in the primitive egg-laying primates - the platypus and the echidna.
Ancient toothed reptiles had a great resemblance to mammals. They were called that because they, like mammals, had differentiated teeth (incisors, canines and molars). In the process of evolution, mammals have developed such adaptations for survival as perfect thermoregulation, constant temperature bodies, viviparity and feeding of young with milk. Particularly important was the improvement of the central nervous system: strong development of the forebrain hemispheres in connection with complex behavior, improvement of the senses. This contributed to the wide geographical distribution of mammals and their development of all habitats, the emergence various forms bodies, high numbers.

181) Is it true that the first animals are closer to reptiles than other mammals? Why?

Right. In Australia and on the adjacent islands live oviparous mammals, which, in their structure and reproductive characteristics, occupy an intermediate position between reptiles and mammals. These include the primal beasts: the platypus and the echidna.

Similarities with reptiles:

1) When breeding, they lay eggs covered with a durable shell that protects the contents of the egg from drying out. (But the echidna carries a single egg in a special pouch, which is a fold of skin on the ventral side of the body).

2) The intestines and urogenital openings open into the cloaca.

3) There are no nipples. (But there are mammary glands).

4) The shoulder girdle is similar to that of reptiles.

5) Low temperature bodies.

6) The jaws are covered with a horny beak.

182) Name the representatives of marsupials. What is characteristic of them?

Marsupials: kaola, kangaroo, marsupial wolf, opossum.

Traits: no placenta, cubs are born underdeveloped and very small, and are borne in a pouch; the brain is very primitive; the temperature is lower than that of placentals and is not constant.

183) Name the main characteristics of placental mammals, which indicate their higher organization compared to proto-beasts and marsupials.

Placental, or higher beasts- the most common infraclass of mammals, considered the most highly developed. Distinctive feature placental is birth in a relatively developed stage. This is possible due to the presence of the placenta, through which the embryo receives from the mother nutrients and antibodies and gets rid of waste products. Their embryo develops in the mother's uterus, is covered by the placenta and feeds and breathes through the umbilical cord.
Placentals have a very well developed brain, especially the forebrain (gyri, cerebral cortex) and the cerebellum, characteristically challenging behavior, caring for offspring.

184) Which orders include: shrew, fruit bat, lynx, hippopotamus?

The shrew is a shrew order.

Krylan - order Chiroptera.

Lynx - carnivorous squad.

Hippopotamus - order Artiodactyls.

185) Complete the laboratory work “Structure of Mammals” presented in the notebook for laboratory work and independent observations “Biology. Diversity of living organisms. 7th grade".

All mammals feed their young with milk. It contains all the substances necessary for the development of the body and is very easily digestible. Depending on the characteristics of reproduction and development, mammals are divided into three groups.

Oviparous or primal beasts

Oviparous animals, or primal beasts, do not give birth to live young, but lay eggs. In addition, like reptiles and birds, they have a cloaca. These include the platypus and echidnas, which live in Australia and the surrounding islands.

Drawing: Oviparous mammals- platypus, echidna

Platypus- a completely unique animal. It is the size of a rabbit, and in front it has a horny protrusion, similar to a duck's beak (hence its name). When the stuffed animal was first brought to Europe, scientists mistook it for a fake and decided that the duck’s beak was sewn onto some kind of animal. Everyone was even more amazed when it turned out that the platypus... lays eggs and incubates them! Who is he: a bird or a mammal? However, it turned out that after hatching its cub still feeds on milk. The mammary glands do not have nipples. Therefore, milk, like sweat, is secreted onto the fur, from which the cub licks it off.

Echidnas in appearance they somewhat resemble a hedgehog with very long spines. They also lay eggs, but do not incubate them, but carry them in a pouch on their belly. Just like the platypus, the cubs lick the milk secreted over the entire surface of the abdomen.

The body temperature of oviparous birds ranges from 25-30 °C.

Marsupial mammals

Marsupials are mammals whose babies are born very small, weak and helpless (for example, a 2 m tall kangaroo has a baby born only 3 cm long). Therefore, for a long time the mother carries such a cub in a pouch on her belly. The bag contains mammary glands with nipples. A newborn baby usually hangs on the nipple without letting it out of its mouth. As he grows up, he begins to crawl out of the pouch and eat the same food as adult animals. However, for a long time, in case of danger, the cub hides in the pouch and is again reinforced with milk, although at this time its younger brother may already be hanging on the other nipple.

Drawing: Marsupial mammals- kangaroo, marsupial mouse, koala

Marsupials are widespread in Australia and America. In total, about 270 species are known. Among them, the most famous are kangaroos. They move by jumping on their hind legs, and their front legs only serve to move grass and branches towards their mouth.

Placental mammals

Placentals are mammals in which a small egg, after fertilization, develops in a special organ - uterus, and the embryo attaches to the wall of the uterus placenta. In the placenta through umbilical cord there is close contact between the blood vessels of the mother and the fetus. All the necessary nutrients and oxygen are supplied to the fetus from the mother's blood, and metabolic products are released back into the mother's blood.

Figure: Carrying an embryo inside the body in placental mammals

The process of intrauterine development of the embryo of viviparous animals and humans is called pregnancy. Gestation periods vary among mammals. As a rule, in small animals it is short (for example, in some mouse-like rodents it is 11-15 days), in medium-sized animals it is several months, in large animals it is a year or more. In addition, lifestyle affects these timings. Those that give birth to cubs in burrows, hollows and other shelters have a short pregnancy. Their cubs are born blind, helpless, numbering 5-6 in medium-sized animals and 8-12 in small ones. Those animals that do not live hiding in holes and moving quickly have a long pregnancy. The cubs of such mammals are born large, well-developed, and within a few hours they can follow their mother. Their number, due to their large size, is only 1-2.

The frequency of reproduction is also related to the size of the animal and the timing of pregnancy: the shorter the pregnancy, the more often reproduction is repeated. So, small mouse-like rodents can have 5-8 litters a year, large ones reproduce once every few years.

Feeding babies with milk

Nursing their young with milk is one of the most characteristic features of all mammals (hence the name of this class). Milk is produced in the female's mammary glands, which are usually located on the chest or belly. The ducts of the mammary glands open outward through small holes at the end of the nipples, the number of which varies (from 2 to 22) and depends on the fertility of the species. A domestic dog that produces 3-8 puppies has 8 teats.

Milk has a very high nutritional value and contains all the necessary substances for the growth and development of babies: water, fats, proteins, carbohydrates, vitamins and mineral salts. White color milk depends on the fact that the fat included in its composition has the form of microscopically small droplets. Such fat is easily digested and absorbed in the baby’s body.

At first, the female feeds her offspring with only milk. Grown-up cubs switch to regular food.

Our planet is inhabited by a large number of a wide variety of animals that have adapted to life in different parts of the Earth. As a result of such diversity, the reproduction and development of animals also has many differences and features.

Insects

Insects have males and females, which can differ in size and color. The female lays eggs and no longer cares for her offspring. She does not protect them from other animals, does not watch the larvae emerge from the eggs.

The larvae look completely different from their parents. These are small and incredibly voracious creatures that feed intensely and increase in size.

After some time it comes new period development: the larvae turn into immobile pupae, which attach to plants, waiting in the wings. After the allotted time, a fully formed adult insect emerges from the pupa, ready for a full life.

To leave offspring, the female and male must meet each other. But how to do that? Many insects use various tricks: they sing serenade songs, glow like tiny lanterns, and emit strong odors.

Rice. 1. Mantises.

Fish, amphibians and reptiles

The reproduction and development of fish occurs in stages:

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• In the spring, females lay eggs and the male fertilizes them.
• Each egg develops into a tiny larva.
• Over time, the larva turns into a fry.
• The fry, actively feeding, increases in size and turns into an adult.

Turtles, crocodiles, snakes, lizards lay eggs, from which small cubs are born, which are no different in appearance from their parents, except for size.

There are two types of reproduction in nature - sexual and asexual reproduction. The first option is used by all animals with a complex body structure: mammals, birds, fish, insects, reptiles and amphibians. Asexual type reproduction is characteristic of single-celled organisms that form their own kind through cell division.

Rice. 2. Baby turtles.

Birds

In the spring, many birds begin to build nests - this is how they prepare for the appearance of offspring. Birds lay eggs in nests and then hatch them, warming them with body heat.

After a while, baby birds emerge from the eggs - chicks. In some birds they are active and inquisitive, and their bodies are covered with down; in others, the chicks are born naked and completely helpless. But all of them, without exception, at first depend on parental care, since they do not know how to fly or get their own food.

To feed their insatiable babies, birds are forced to search for suitable food from morning to evening. However, such efforts quickly pay off - already at the beginning of summer, the matured chicks of many birds leave their parental nests.

Mammals

Mammals or animals, unlike other animals, give birth to live young and feed them with their milk. Until the kids get stronger and are ready for adult life, parents carefully look after them, protect them from enemies, teach them to get their own food. As a rule, all these functions rest on the shoulders of the mother, but there are mammals that raise their offspring together.

While the kids are helpless, they have many enemies. To avoid becoming easy prey, they hide in their home almost all the time. Fox and badger cubs hide in deep holes, squirrel cubs are securely hidden in a nest in a tree or in a hollow, bear cubs' home is a spacious den.

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