Types of insects and their orders. §29

The class insects has two subclasses: primary wingless And winged.

TO subclass primary wingless These include insects whose ancestors never had wings (silverfish, springtails, etc.). Silverfish live in sheds and closets. basements. It feeds on decaying substances and is harmless to humans. IN flower pots With excessive watering, wingless insects - springtails - often appear. They feed on rotted plants or their lower plants. The best way to combat them is to reduce watering.

Subclass of winged divided into insects with incomplete transformation and insects with complete transformation.

The distribution of species into orders is carried out taking into account such characteristics as the nature of development, structural features of the wings, and the structure of the oral apparatus. The main characteristics of some orders of insects are presented below.

Some characteristics of the most important orders of insects

Units	Type of development	Number of pairs of wings	Oral apparatus	Features of wing development	Some representatives
Cockroaches	With incomplete transformation	Two pairs	Gnawing	Elytra	Red and black cockroaches
Termites	With incomplete transformation	Two pairs	Gnawing	Mesh	Termite
Orthoptera	With incomplete transformation	Two pairs	Gnawing	Elytra	Locusts, grasshoppers, crickets
Lice	With incomplete transformation	No wings	Prickly-sucking	Wingless	Head louse, body louse
Bedbugs	Louse	Two pairs	Prickly-sucking	Elytra	Turtle bug, staring bug, water strider bug
Homoptera	With incomplete transformation	Two pairs	Prickly-sucking	Mesh	Cicadas
Grandmas	With incomplete transformation	Two pairs	Gnawing	Mesh	Grandma-watch, grandma-yoke
Beetles, or Coleoptera	With a complete transformation	Two pairs	Gnawing	Elytra are hard	May beetle, Colorado potato beetle, burying beetles, bark beetles
Butterflies, or Lepidoptera	With a complete transformation	Two pairs	Sucking	Mesh with scales	White cabbage, hawthorn, silkworm
Hymenoptera	With a complete transformation	Two pairs	Gnawing, lapping	Mesh	Bees, bumblebees, wasps, ants
Diptera	With a complete transformation	1 pair	Prickly-sucking	Mesh	Mosquitoes, flies, gadflies, midges
Fleas	With a complete transformation	No	Prickly-sucking	Wingless	Human flea, rat flea

Insects with incomplete metamorphosis

The most common are: squad of cockroaches- typical representative - red cockroach. The appearance of cockroaches in homes is a sign of sloppiness. They come out of their hiding places at night and feed on carelessly stored food, contaminating it. Female cockroaches carry a brown egg “suitcase” at the end of their abdomen - ooteku. They throw it in the trash. Eggs develop in it, from which larvae are born - small white cockroaches similar to adults. Then the cockroaches turn black, molt several times and gradually turn into adult cockroaches.

Termite squad- this includes social insects that live in large families in which there is a division of labor: workers, soldiers, males and females (queens). Termite nests - termite mounds - can be of considerable size. Thus, in African savannas, the height of termite mounds reaches 10-12 m, and the diameter of their underground part is 60 m. Termites feed mainly on wood, and can damage wooden buildings and agricultural plants. There are about 2,500 species of termites.

Order Orthoptera- most representatives of the order are herbivorous, but there are also predators. This includes grasshoppers, cabbage, locusts. The green grasshopper lives in the grass in the meadows and steppes. It has a long club-shaped ovipositor. Kapusyanka - has burrowing legs, flies and swims well. Causes great damage to the underground parts of garden plants, such as cucumbers, carrots, cabbage, potatoes, etc. Some types of locusts are prone to mass reproduction, then they gather in huge flocks and fly over a considerable distance (up to several thousand kilometers), destroying all green vegetation in the area. your way.

Squad of bedbugs- this includes known pests of agricultural crops - turtle bug, sucking the contents of the grains of cereal plants. Found in homes flea bug- a very unpleasant insect for humans. The water strider bug lives in fresh water bodies or on their surface, feeding on insects that fall into the water. Predatory bug attacks various invertebrate animals and fish fry.

Order Homoptera- all its representatives feed on plant juices. Many types aphids cause great harm to cultivated plants. Many Homoptera are carriers viral diseases plants. This includes a variety of cicadas, whose sizes range from a few millimeters to 5-6 cm. They live in the crowns of trees.

Granny squad- exceptional predatory insects. Adults attack prey in flight. The best flyers. Their flight is highly maneuverable: they can hover in the air, be mobile and can reach speeds of up to 100 km per hour. This includes rocker head, grandmother-watchman and etc.

Insects with complete metamorphosis

Squad of beetles, or Coleoptera, is the most numerous order of insects, with up to 300,000 species. Beetles are common in a wide variety of land and freshwater environments. Their sizes range from 0.3 to 155 mm in length. Many beetles cause great damage to cultivated plants. One of the pests of potatoes and other plants is Colorado beetle, brought to us from America. Beetle beetle- pest of grains; Chafer- its larvae damage tree roots and potato tubers; beet weevil- affects sugar beets. In addition, this includes bark beetles, grinding passages in the bark and bast fibers valuable species trees, and the larvae goldenrod and i live in dead wood and cause great damage to forestry industries.

Many beetles spoil food supplies: pea weevil, bread beetle, carpet beetle, damaging leather and wool products. Another small beetle belongs to the order of beetles tube gun. The biology of these beetles is very interesting. In spring, the pipe cutter cuts the leaf down to the main vein in a special way. The cut part of the leaf fades and loses its elasticity. Then the beetle rolls it up into a ball and lays its eggs there. Something like a cigar is formed. This is how the tubeweaver expresses concern for its offspring.

Individual beetles feed on the remains of plants and animals and play the role of orderlies in nature, for example: pustule beetles And gravestones. Some can be used to control pests. So, ladybug destroys aphids, and large green ones paint beetles- caterpillars.

Beetles can be extremely beautiful, large in size, for example stag beetle, or stag, listed in the Red Book, reaches a length of up to 8 cm, its larvae develop in rotten stumps for about five years and grow up to 14 cm in length. The reservoirs are inhabited by beetles of various sizes and feeding methods - the swimming beetle and the black water lover. The swimming beetle is a predator, the black water lover is a herbivore.

Butterfly squad, or Lepidoptera, - representatives of this order are distinguished by the varied colors of their wings. This includes hives, cabbage butterfly, silkworm etc. Among the species living on Far East, there are very large moths, whose wingspan corresponds to the width of an unfolded notebook. The wings of butterflies are covered with modified hairs - scales, which have the ability to refract light. The iridescent color of the wings of many butterflies depends on this phenomenon. Butterfly larvae are called caterpillars. They have a gnawing apparatus and a long body. Their salivary glands, in addition to saliva, also secrete silk threads, from which a cocoon is woven before pupation. Adult butterflies are very good plant pollinators. The caterpillars of most butterflies are herbivorous, eating leaves of plants, causing significant harm, for example, cabbage whites, apple moths, lacewings, ringed silkworms, etc. The caterpillar of the house moth feeds on woolen products, damaging them, some caterpillars spoil flour, etc. food products.

Mulberry and oak silkworms- people have been breeding them for a long time in order to obtain silk (from cocoons). A lot of big butterflies extraordinarily beautiful, for example swallowtail, Apollo etc. The large butterfly is very interesting night peacock eye, on the wings of which there are ocellated spots. Its caterpillar is large, fleshy, green in color, and before pupation it weaves a cocoon the size of a chicken egg.

Large moths with sharp-angled wings, characterized by very fast flight - hawkmoths, - so named because they readily feed on fermented and odorous tree sap, especially birch sap, which appears on wounds and stumps.

Order Hymenoptera- unites a variety of insects: bees, bumblebees, OS, riders, sawflies etc. The lifestyle of these insects is varied. Some of them are herbivorous, as their larvae (very similar to caterpillars) cause great damage to crops and other plants, e.g. bread and pine sawflies . Sawfly larvae feeding on leaves become so similar to butterfly caterpillars that they are called false caterpillars. An amazing adaptation is the ovipositor of sawflies, which serves to cut out pockets in plant tissues in which female sawflies hide their eggs, thereby showing original care for their offspring.

Excellent plant pollinators are bumblebees. This is a social insect. The bumblebee family only exists for one summer. Nests are built in mouse holes, hollows, squirrel nests, in birdhouses. The female builds the nest, equipping wax cells in it for laying eggs. A supply of food is placed in the cell - a mixture of pollen and honey. The larvae emerging from the eggs eat food and after two to three weeks weave silk cocoons, turning into pupae. Working bumblebees, females and males, emerge from the pupae. By the end of summer, there are up to 500 bumblebees in large nests. In autumn, the old queen, males and workers die, and the young queens hide for the winter.

Lifestyle OS looks like a bumblebee. They also exist for one summer. Wasps benefit by destroying harmful insects, and the damage from damage to fruits is small. More harm from hornets(one of the types of swarming wasps): they gnaw the bark of young trees and eat bees. Having settled near an apiary, they destroy thousands of bees over the summer.

Of the social insects of the order Hymenoptera, it is most beneficial honey bee. It is both a wonderful plant pollinator and produces an extremely healthy food product - honey, as well as wax and royal jelly, which are widely used by humans in perfumery. medicine, for the manufacture of varnishes, paints, etc.

A bee family is a surprisingly complex whole, in which all members of the family are very closely related to each other. Life and prosperity of the entire species are equally impossible without the queen and without drones, without worker bees. Using knowledge about the lives of all members of the bee family, beekeepers have learned to create specialized houses for bees - hives, conditions for feeding bees (taken to the fields where honey plants are grown) and at the same time receive not only honey good quality, but also quantities.

Representatives of the order Hymenoptera are used as a biological method of combating harmful insects. These include various riders, as well as Trichogramma, which is bred artificially

Order Diptera. This includes well-known insects: flies, mosquitoes, midges, gadflies, horseflies and other insects similar to them, having one pair of transparent wings. The second pair of wings turned into the so-called halteres. The common mosquito lives in swampy and damp areas. Mosquitoes are especially numerous in mid-summer. Residents of the taiga and tundra call their clusters vile. With their piercing mouthparts, mosquitoes easily pierce human skin and suck his blood. Worm-like mosquito larvae live in stagnant water. While feeding, the larvae grow, molt and turn into mobile pupae. Mosquito pupae also live in water; they cannot feed, so they soon turn into adults.

The malaria mosquito and the common mosquito are distinguished by their position.

Common mosquito (squeaker) keeps his body parallel to the surface on which he sits, and malarial- at an angle to her, raising the rear end of the body high. The malaria mosquito lays eggs in a pond one at a time, while the common mosquito lays eggs in packs, floating on the surface in the form of rafts. Fungus gnat larvae live in the fruiting bodies of cap mushrooms.

flies, unlike mosquitoes. have short antennae. Their larvae are white, usually legless and headless. The housefly's worm-like larvae live and develop in kitchen waste, in piles of manure and sewage, where the fly lays its eggs. Before pupation, the larvae crawl out of the sewage, penetrate the soil and turn into pupae.

Adult flies hatching from pupae fly everywhere in search of poverty. From latrines and cesspools they fly onto openly lying food products and contaminate them. Flies transmit gastrointestinal disease bacteria and roundworm eggs to human food. Therefore, it is very important to combat flies. Protect food from flies with gauze or hoods, wash vegetables and fruits before consumption.

Midges- long-whiskered bloodsuckers of small size, the larvae of which develop at the bottom of reservoirs with running water. In the tropics and subtropics, in the Crimea there are very small mosquitoes - mosquitoes. Their larvae develop in moist soils, rodent burrows, etc. Mosquitoes are carriers of many diseases (malaria, etc.). We have a Hessian fly that destroys cereal plants.

Gadflies, horseflies They cause great harm to humans and domestic animals with their bites, as well as their ability to transmit pathogens of such dangerous diseases as tularemia and anthrax.

At the same time, flies are pollinators of many plants.

Rat flea can transmit plague pathogens from sick rodents - a very dangerous disease that once claimed thousands of human lives.

None Living being is not born in vain. And even in relation to mosquitoes and insects, this statement is true. But there are so many of them - there’s a whole table. Insect orders, however, also bring both benefit and harm in their own way. Today we will talk about their features.

Nature's fantasy is limitless

It is not easy to classify all insects existing on our planet. And all because this is the largest group of organisms. Moreover, its diversity is so great that entomologists-systematists have to do a tremendous amount of work dividing all this crawling, flying and jumping diversity into groups and classes.

Typically used to facilitate recording and sorting the characteristics possessed by orders of insects, table. It is not surprising that it is so easy to get confused, because in nature there are more than a million species of individuals, and every year from 3 to 10 thousand new species are added that have not yet been included in the “register” and are not yet known to science.

Live and reproduce even in the cold

The largest number of discoveries occurs in tropical regions that are poorly studied and rich in insects. But oddly enough, in cold places, for example in the north of our country, there are also a lot of them, judging by the list that grows every year. And therefore, using various groups, subsections, and so on, scientists are trying to bring this numerous brethren to a system that is understandable for study. For example, the biology table (grade 7) “Orders of insects” subdivides all new species according to common characteristics, which are indicated in the list below.

List for compiling characteristics

Body segmentation.
Mouth organs.
Limbs.
Presence of shedding.
Body parts.
Symmetry.
Methods of transportation.
Development of sense organs.
Dioecy.
Development.
Circulatory system.
Having a heart.
Number of wings.
Nervous system.
Respiratory system.
Excretory organs.

For such an impressive species diversity There are several reasons for insects. And first of all, it should be noted that, having a typically terrestrial organism, as can be seen even from the points classifying orders of insects (table, grade 7), they are perfectly adapted to the living conditions of land.

Reasons for the large-scale species extravaganza

The entire life organization of insects is closely intertwined with protection from drying out and rational saving of moisture. The surface of the integument, both in specimens long known to science and in specimens that have only just been discovered, is protected by a thin wax-like film called the epicuticle. This is what prevents the evaporation of water. Plus, tracheal breathing in insects is very effective in terms of saving moisture, compared to pulmonary breathing. This is explained by the fact that the spiracles, which is what the respiratory openings are called in the representatives of the fauna we are considering, are very small in size and are distinguished by their ability to close.

Defense system

The excretory system, which is discussed in paragraph 16 of the above-mentioned table classifying insect orders (class 7 school curriculum), represented by Malpighian vessels. The idea is to produce uric acid crystals that can bind small amounts of water.

The anus of insects is distinguished by the presence of special rectal glands, which are capable of drawing moisture from the forming excrement and returning it back to the body cavity. In addition, for most individuals, even the eggs they lay are also perfectly protected from loss of moisture. Conclusion: insects are perfectly adapted to living in a terrestrial environment, as they easily cope with one of the most important tasks - protection from drying out.

Rapid evolution

The ancestors of modern insects were already terrestrial organisms, and therefore among them there are no inhabitants of the seas and oceans. There is, of course, a part of insects that is associated with fresh water bodies, where the larvae they deposit develop. These include caddisflies, mayflies, dragonflies, stoneflies, and some other species of beetles and dipterans. But scientists believe that this is just a secondary connection with the aquatic environment. And their very formation as a class occurred approximately 350 million years ago (Devonian period). The rapid evolution allowed them already in the next, Carboniferous period to form all the modern orders of insects adapted to the environment (as the table indicates).

Impact of plant evolution

The process of evolution of all these jumping, flying and biting hordes is closely intertwined with the time of plant development. When some mastered the land, others settled further from the coastal areas, conquering the hills. The Cretaceous period, marked by the appearance of flowering plants, also marked the beginning of the close connections that formed between insects and plants. Most modern flowering representatives of the flora are also pollinated by them.

And for the class of phytophages, this particular plant species is the main food item. Features of insect orders, the table of which is presented in the article, their formation and differentiation as separate groups occurred during the period of transition from living in the soil to living at higher elevations, with which the emergence of flight is associated.

Fly - don't crawl

If we consider all invertebrates, then only the class of insects acquired wings and mastered the air environment. It is clear that flight is not comparable in efficiency to movement on land. This is an opportunity to choose from above the most attractive place and, moreover, a significant saving of effort. For example, scientists have calculated that for a 3-meter walk a bee expends an amount of energy equal to a 78-meter flight. Agree, there is a noticeable difference. In general, the very ability of insects to spread over long distances can impress anyone. The Bible also describes cases of global migrations migratory locust. Surprisingly, this species is easily able to cross the Mediterranean Sea, and hordes of them have been seen from ships at least 1000 km from land. And laboratory tests and experiments show that locusts can spend 6 days in flight without sitting down for a second, while rotating a small mini-carousel to which they are tied with a thread.

Traveler

Of the individuals described in the Insect Orders table, the leading position is occupied by perhaps the most famous American migratory butterfly, called the monarch. This representative of the species makes regular flights from America to winter in Mexico, after which it returns to its homeland again, ready to reproduce.

Individual specimens of monarchs were found even on the coasts of England and France. They were carried there by air currents, which is why they had to cross the Atlantic Ocean.

The most important and main orders of insects (table)

The class of insects includes up to 40 orders, which, in turn, are divided according to the type of development into 2 separate groups:

Units with full transformation.
Insect orders (table below) with incomplete metamorphosis.

Homoptera	This order includes copperheads, aphids and scale insects. These individuals feed on plant juices. The head of these representatives is inactive, and the mouthparts are piercing-sucking and have a proboscis. Most homoptera have two pairs of thin, transparent wings. Clusters of greenish small aphids can be observed on young shoots of bushes, trees and other herbaceous plants. And adult honeysuckers can usually be seen in early summer on the leaves of apple and pear trees. At this time, if you accidentally touch a branch, a lot of these small leaf fleas immediately appear in the air. Scale insects can often be found on indoor plants or on garden shrubs
Orthoptera	The order of Orthoptera includes grasshoppers, locusts, crickets, mole crickets and the like. The oral apparatus of these representatives in its structure belongs to the category of gnawing. Their two pairs of wings are different in appearance: the first are fan-shaped, and the second are narrow in shape, having longitudinal venation. The structure of the hind legs belongs to the category of pushing-jumping legs. Orthoptera have filiform antennae. Most representatives of this order not only perfectly perceive sounds, but also produce them themselves. For example, grasshoppers: they have both a sound-producing apparatus, which is located on the wings, and an auditory apparatus, located on the shins of the front legs. Female Orthoptera have an ovipositor. It is also worth mentioning that some insects of these orders lead a burrowing-earthen lifestyle, for example mole crickets
Hemiptera	Representatives of the order Hemiptera, or bedbugs, are terrestrial and aquatic insects with piercing-sucking mouthparts. Individuals received this name for the possession of two pairs of wings, the upper ones are semi-rigid, and the lower ones are delicate, membranous. Summer residents and gardeners can often see these individuals in the summer when harvesting. They are especially often found on the leaves of strawberries, raspberries, and currants. These are green forest bugs that have an unpleasant odor.

Group of units with full transformation

Now let us pay attention to how the table classifies orders of insects with complete metamorphosis. This group includes Coleoptera, Diptera, Lepidoptera, Hymenoptera and fleas.

Coleoptera	This order includes May beetles, ground beetles, dung beetles, woodcutters, ladybugs, longhorned beetles, or weevils. This division is distinguished by the fact that in most representatives, when they are at rest, the hind membranous wings are completely covered with hard ones on top, which serves as protection for them from damage. The mouths of beetles are gnawing.
Diptera	The order of Diptera includes flies and mosquitoes. They have only one pair of membranous wings. The flask-shaped organs, which are called halteres, according to scientists, were once hind wings. The mouthparts of representatives of this class are piercing-sucking, as well as licking. Their young larvae have no legs. Individuals develop in the rotting remains of plants, in water, soil, in the bodies of not only living but dead animals.
Lepidoptera	The order Lepidoptera, or so-called butterflies, includes insects that differ from others in two ways: 1. By the presence of scaly covering of the wings. 2. By the oral apparatus of the sucking type and at the same time curled into a spiral. The scales on their wings are hollow inside, flattened and modified hairs. The antennae of diurnal butterflies are usually club-shaped, while those of nocturnal butterflies are feathery. Butterfly larvae are worm-like caterpillars. Butterflies have three pairs of legs, as well as growths that scientists define as false legs. The mouthparts are gnawing.
Hymenoptera

Some more species of individuals with incomplete transformation

The most common individuals representing orders of insects with incomplete transformation, the table of which is presented above, are red cockroaches. These individuals help people, hinting that it is time to pay attention to their home. Their appearance in homes has always been considered a sign of sloppiness. Cockroaches quietly emerge from their hiding places at night and feed on food scraps, crumbs and carelessly stored food left on tables, contaminating them in the process.

Termites

This order includes insects that live in large families. These are organized communities in which there is a dividing labor hierarchy - from simple workers to the female queen. The nests of these individuals, called termite mounds, are usually large, sometimes even quite significant.

For example, their height in African savannas reaches 10-12 m, and the diameter of the underground base can reach up to 60 m. Termites eat mainly wood, thereby causing damage to wooden buildings. In addition, their diet includes agricultural plants. Today, approximately 2,500 species of termites are known and recorded. If in school textbook was introduced Comparative characteristics orders of insects, a table even for these individuals alone would take up half of its pages.

A little more about beetles

Beetles, or Coleoptera, are the most numerous army among insect orders. Today there are up to 300,000 species of them. Most of their representatives are large in size and are extremely beautiful. For example, the stag beetle listed in the Red Book, popularly known as the “stag beetle,” reaches a length of up to 8 cm, and its larvae, when placed in a favorable development environment - rotten stumps - can remain there for up to 5 years and grow into length up to 14 cm.

The biology table (grade 7) “Orders of insects” divides these representatives into many more subgroups according to the characteristics given in it. Beetles also live in bodies of water; they also differ from each other in size and feeding method. For example, swimming beetles are predators, while black water beetles are herbivores.

The role of beetles on the planet

Beetles, as is already known, are included in the main orders of insects (their table is presented above). They bring both harm and benefit in their own way. Individuals of this group that spoil food products include beetles called “bread borer” and “pea weevil”. The carpet beetle spoils wool and leather products. And its smaller brother, called the tubeweed, spoils the leaves of plants. In the spring, he cuts them down to the main vein. Starting to fade, the cut part ceases to be elastic, which is what this beetle needs. Next, he rolls it up into a ball and lays eggs there. This folded leaf resembles a small cigar. This is his nature, this is how he takes care of his offspring.

But there are beetles that can be called orderlies, because they feed on the rotting remains of plants and living creatures. The names of these representatives correspond to their functions: grobarik and pustule. This is the characteristic of insect orders. A table of such individuals is compiled by scientists separately. Because such representatives can be used to establish a balance where there are too many harmful insects, and this poses a threat to the future harvest. For example, ladybugs destroy aphids, and paint beetles destroy caterpillars.

Diversity in nature

What species does biology not study? The table "Orders of Insects" is the clearest example of this. It was impossible to even imagine the existence of such generous diversity. For example, butterflies, or lepidoptera, are distinguished by the magnificent coloring of their wings. Among them there are nocturnal representatives living in the Far East, whose wingspan is equal to the width of an unfolded notebook. And people have been breeding mulberry and oak silkworms since ancient times in order to obtain silk from their cocoons. Most butterflies are extremely beautiful, for example, Apollo, swallowtail and the like. They represent the class "Insects". The units, the table of which is quite impressive, have their own characteristics. Just remember how attractive a large butterfly called the night peacock's eye looks. On its wings there are oval spots resembling an eye.

Conclusion

Insects, no matter what is said about them, are not considered major representatives of the natural world. Many of them are beneficial by pollinating flowering plants and destroying pests of crops. Most of this large fraternity have a fairly organized lifestyle, where hierarchy is strictly observed. Even those that do not have obvious benefits, still tell us something by their existence, warn us about something. Perhaps someday all living beings on the planet will learn to understand each other without words, and then representatives of this class will tell us a lot of interesting things.

Habitats, structure, lifestyle

Insects are the largest class of animals. It includes more than 1 million species. Insects live everywhere: in forests, gardens, meadows, fields, vegetable gardens, on livestock farms, in human homes. They can be found in ponds and lakes, on the body of animals.

The body of insects consists of a head, thorax and abdomen. There are a pair of compound eyes on the head, a pair of antennae, three pairs of legs on the chest, and most have one or two pairs of wings, and spiracles on the sides of the abdomen.

Insects differ in the shape of their body parts, the size of their eyes, the length and shape of their antennae and other characteristics. Their antennae, mouthparts, and legs are especially diverse. Some insects have lamellar antennae (many beetles), others have filamentous antennae (grasshoppers), others have feathery or club-shaped antennae (butterflies), etc. The mouthparts can be gnawing, like those of cockchafers, piercing-sucking, like mosquitoes, sucking, like butterflies, etc. The hind legs of grasshoppers are jumping, while those of swimming beetles are swimming; The front legs of the mole cricket are digging. All these and other structural features have developed in insects in connection with adaptation to certain living conditions.

Rice. Bombardier (beetle). Family - ground beetles

The internal structure of insects is mainly related to the respiratory, excretory and nervous systems. The respiratory organs of insects - the trachea - are highly branched. U small insects Gas exchange occurs by diffusion. Large insects ventilate the trachea (when the abdominal walls relax, air is sucked into the trachea, and when contracted, it exits into external environment). The excretory organs of insects are numerous tubes, the free ends of which are closed. The excretory products entering them flow into the posterior intestine. Insects have fat cells that store nutrients and water. Some substances unnecessary for the body are deposited in them.

Differences in the nervous system of insects are associated with the enlargement of the suprapharyngeal nerve ganglion (it is often called the brain), a decrease in the number and enlargement of the nodes of the ventral nerve chain. The more complex structure of the nervous system is manifested in the complexity of insect behavior. A bee, for example, having found flowering nectar-bearing plants, upon returning to the hive, crawls on the honeycomb, “dances,” describing certain figures, by which other bees establish the direction to the place of honey collection. The ants close the entrances to the anthill at night, bring wet needles to the surface, and after drying, drag them into the depths of the anthill.

Types of insect development

Insects are dioecious animals. In some insects (locusts, bedbugs), fertilized eggs laid by females develop into larvae that are similar in appearance to adults. Feeding heavily, they grow, molt several times and become adult insects. In other insects (butterflies, beetles, flies), the larvae are not similar in appearance and nutrition to adults. The larvae of the cabbage butterfly, for example, are worm-like and do not feed on nectar, like butterflies, but on cabbage leaves. Their mouthparts are not sucking, but gnawing. After several molts, the caterpillars turn into pupae that do not feed or move, but complex changes occur under their chitinous cover. After some time, the pupa’s body cover bursts and an adult insect emerges.

Development that occurs in three phases, and the insect larvae are similar to adults, is called incomplete transformation. The development of insects, which occurs in four phases (including the pupal phase), and the larvae do not resemble adults, is called complete metamorphosis.

Development with transformation makes it possible for insects to survive under unfavorable living conditions (low temperature, lack of food) at one or another less vulnerable stage of development. Insects with complete metamorphosis have the greatest advantages. Their larvae do not compete with adults: they usually use different food and develop in different habitats.

The main orders of insects

In the class of insects there are from 30 to 40 orders. The largest of them are the orders of Orthoptera, Homoptera, Hemiptera, Coleoptera, Lepidoptera, Hymenoptera, and Diptera.

Orders of insects with incomplete metamorphosis. The order Orthoptera includes locusts, grasshoppers, crickets, and mole crickets. They are characterized by a chewing mouthpart, two pairs of longitudinally veined wings, and a (usually) hopping hind pair of legs. Many Orthoptera produce and perceive sounds (in grasshoppers, the sound apparatus is located on the front wings, and the auditory apparatus is on the shins of the front legs). Their antennae are thread-like. Females of many species have an ovipositor. The order Homoptera includes aphids, cicadas, etc., feeding on plant sap, having a piercing-sucking proboscis and 2 pairs of transparent wings.

The order Hemiptera, or bugs, includes terrestrial and aquatic insects with piercing-sucking mouthparts, two pairs of wings (semi-rigid upper and membranous lower), and highly developed scent glands. Of the representatives of this order, the most common are green forest bugs and long-legged water strider bugs. The same order includes the bedbug, which feeds on the blood of people and animals living in human housing.

Orders of insects with complete transformation. The order Coleoptera, or beetles, includes insects with rigid front wings and membranous hind wings. In most beetles, when at rest, hard wings completely cover the membranous wings and protect them from damage. Beetles have gnawing mouthparts. The order Coleoptera includes chafer beetles, ground beetles, ladybugs, and weevils.

Butterfly Papilio demoleus. Photo: Jeevan Jose

The vast majority of insects of the order Lepidoptera, or butterflies, are characterized by two features: scaly cover on two pairs of wings and a sucking mouthpart, usually coiled. The antennae of daytime butterflies are usually club-shaped, while those of nighttime butterflies are feathery. Worm-like butterfly larvae (caterpillars), in addition to three pairs of jointed legs, have false legs - outgrowths of the body. Caterpillars have gnawing mouthparts.

Diptera - flies, mosquitoes, horseflies, etc. - have one pair of membranous wings. The hind wings are transformed into flask-shaped organs - halteres. The mouthparts of dipterans are piercing-sucking or licking. Larvae have no legs. They develop in water, soil, rotting remains of plants, living animals and corpses.

Insect with complete transformation (with metamorphosis) goes through four stages in its development: egg - larva - pupa - adult insect (imago).

Pay attention!

Orders of insects with complete transformation: butterflies (Lepidoptera), beetles (Coleoptera), Diptera, Hymenoptera, fleas.

Most species of insects are characterized by development with complete transformation. In insects with complete metamorphosis (butterflies, beetles, flies, wasps, ants), the larvae do not at all resemble adults. They have no compound eyes (there are only simple eyes, or no visual organs at all), often no antennae, no wings; the body is most often worm-shaped (for example, butterfly caterpillars).

In insects with complete metamorphosis, the larvae often live in completely different places and feed on different foods than adult insects. This eliminates competition between different stages of the same species.

Insect larvae with complete metamorphosis molt several times, grow and, having reached their maximum size, turn into doll. The pupa is usually motionless. An adult insect emerges from the pupa.

Watch a video that shows a Monarch butterfly emerging from its chrysalis.

Order Butterflies, or Lepidoptera

Butterflies differ from other insects mainly in two ways: scaly covering of wings and sucking mouthparts, rolled up in a spiral.

Butterflies are called Lepidoptera because they have small chitinous structures on their wings. scales. They refract the incident light, creating a bizarre play of shades.

The coloring of the wings of butterflies helps them recognize each other, camouflages them in the grass and on the bark of trees, or warns enemies that the butterfly is inedible.

Mouthparts of butterflies sucking- This is a proboscis curled into a spiral. Butterflies feed on the nectar of flowers.

Butterfly larvae (caterpillars) have gnawing mouthparts and feed on plant tissue (most often).

When pupating, the caterpillars of some butterflies secrete silk threads. The silk thread is secreted by a special silk gland located on the lower lip of the caterpillar.

Order Beetles, or Coleoptera

Representatives of this group have dense, hard elytra covering the second pair of leathery wings, with which they fly. The mouthparts are gnawing.

Among the beetles there are many herbivores, there are predators and carrion eaters.

Beetles live in the ground-air environment (on plants, the surface of the earth, in the soil) and in water.

Beetle larvae are both very mobile predators, living openly, and sedentary, worm-like, living in shelters and feeding on plants, fungi, and sometimes decomposing remains of organisms.

Order Diptera

These insects have only one pair of wings. The second pair is greatly reduced and serves to stabilize the flight. This group includes mosquitoes and flies. They have piercing-sucking or licking mouthparts. Some dipterans feed on pollen and nectar of flowers (syrphid flies), there are predators (quackers) and bloodsuckers (mosquitoes, midges, midges, horseflies). Their larvae live in the decaying remains of cesspools, composts (house flies), in water (mosquitoes and midges) or lead a wandering lifestyle and prey on small insects.

Order Hymenoptera

The group includes such well-known insects as bumblebees, wasps, bees, ants, sawflies, and wasps. They have two pairs of membranous wings (some have no wings).

By modern classification animal world, the following orders of insects with complete transformation (metamorphosis) are distinguished: order Reticuloptera, order Caddisflies, order Coleoptera, order Lepidoptera, order Diptera, order Fleas, order Hymenoptera, etc.

All species of these orders have stages in the development cycle: egg - larva - pupa - imago.

Order Reticulata– 4 wings, long, narrow, with few longitudinal and numerous transverse veins. The head is extended downwards into the proboscis. The mouthparts are gnawing. Species: Antlion. Its larvae live in holes they dig, where they catch ants that fall there. Adults look like small dragonflies.

Squad Caddisflies – There are 4 wings, the rear ones are larger and fold fan-shaped. The jaws form a proboscis. There are no mandibles. The larvae are similar to butterfly caterpillars and live in water, breathe through tracheal gills, and build tubular houses from grains of sand and plant parts. Species: caddisfly.

Order Coleoptera– there are 4 wings, the front ones are turned into elytra and are not used for flight. The mouthparts are gnawing. The pupae are free (movable). View - bark beetles. Plant pests.

Order Lepidoptera– there are 4 wings, they are covered with colored scales. The oral apparatus is sucking. The larvae are equipped with false legs and are called caterpillars. The pupae are not free (immobile). Species – different types of butterflies, moths, silkworms. Most species (adults and caterpillars) are plant pests. The silkworm is used by humans to produce silk.

Order Diptera– 2 wings, the hind ones are rudimentary and turned into ground beetles. The mouthparts are licking or piercing-sucking. The larvae are legless and headless. Pupae are free or barrel-shaped (immobile). Species – mosquitoes, flies, sand flies. They are pathogens or carriers of pathogens in humans and animals.

Flea Squad- no wings, body flattened laterally. The mouthparts are piercing-sucking. Species: dog flea, human flea. They are carriers of human and animal pathogens (plague, etc.).

Order Hymenoptera– 4 wings, lapping mouthparts. The larvae are often legless. Species: ants, bees, wasps, bumblebees. Meaning: give honey, propolis, wax (bees); ants are carriers of aphids, intermediate hosts in the development cycle of some helminths.

general characteristics orders of insects with incomplete metamorphosis

According to the modern classification of the animal world, the following orders of insects with incomplete transformation are distinguished: order Orthoptera, order Termites, order Dragonflies, order Bedbugs (hemiptera), order Homoptera, order Lice.

Order Orthoptera– the elytra are leathery, straightened along the back at rest, the hind wings are of a delicate structure. Sometimes the wings are underdeveloped. The mouthparts are gnawing. Species: locusts, cockroaches, grasshoppers. 3 purpose: plant pests (economic damage - locusts); mechanical carriers of human and animal pathogens (cockroaches).

Squad Termites- the front and rear wings disappear; they are present only in sexual individuals (there are also workers and soldiers). They live in communities, building termite mounds taller than a person. The mouthparts are gnawing. Meaning: pests of wooden buildings, furniture, books.

Dragonfly Squad– 2 pairs of wings, with a continuous mesh network of veins. The mouthparts are gnawing. In the development cycle there is a mobile nymph. The larvae live in water. Meaning: destroy insects (daytime predators).

Squad Bedbugs– there are 4 wings, the front ones are half rigid, and membranous towards the free end. The mouthparts are piercing-sucking. Species - water striders (harmless), bed bug - mechanical carrier of human pathogens.

Order Homoptera– 4 wings, all identical, with a sparse network of veins. The mouthparts are piercing. Species: aphids, cicadas. Meaning: plant pests.

Troop Lice– no wings (secondary wingless). The mouthparts are piercing-sucking. Types: head, body, pubic lice. Meaning: head and body lice are carriers of pathogens of human diseases, and are also the causative agents of human disease - pediculosis.

GENERAL CHARACTERISTICS

TYPE OF SHELLFISH

The phylum Mollusca belongs to the subkingdom Multicellular, the kingdom Animals, the superkingdom Eukaryotes, and the empire Cellular. The phylum includes 7 classes, of which three are the most common: the Gastropod class (small pond snail, bitinia), the Bivalve class (toothless, pearl barley), and the Cephalopod class (squid, octopus). In total, there are about 100,000 species in the phylum (Fig. 60).

Mollusks live mainly in seas and fresh water bodies, less often on land. They lead a free lifestyle. These are three-layered animals. Dimensions – a few cm.

The body is solid (non-segmented). Consists of a head, torso and legs. In most species it is enclosed in a calcareous shell various shapes. The shell consists of 3 layers: outer – organic, horny; middle – calcareous; internal – mother-of-pearl.

On the inside of the shell, the entire body is covered by a skin fold - the mantle, due to the activity of which the shell is formed. The space between the body and the mantle is called the mantle cavity. The respiratory organs, secretions, ducts of the gonads and intestines open into it.

The organ of movement is the leg. This is a muscular unpaired outgrowth of the ventral side of the body.

The secondary body cavity in most species is reduced and is represented by the pericardial sac and the cavity of the gonads. In the spaces between the organs there is a loose layer of cells connective tissue– parenchyma.

The nervous system is of a scattered nodular type or in the form of cords dotted with nerve cells. Nerves extend to all organs. In species leading an active lifestyle, at the head end there are large nerve nodes - the “brain” and complex sensory organs: touch (tentacles), vision (eyes).

Digestive system begins with the oral opening, followed by the pharynx (in gastropods, a muscular grater tongue is placed in it). Next comes the esophagus, stomach, intestines, into which the liver duct opens, and the digestive tube ends with the anus.

Excretory system - kidneys of the metanephridial type, which are highly modified metanephridia. One end of the tubular kidney faces the pericardial sac (coelom), and the second opens into the mantle cavity.

The circulatory system is not closed. The heart consists of one ventricle and one or more atria. The blood washes all the organs, then collects in the vessels leading to the gills, and then the oxygenated blood enters the heart.

Respiratory system - in most species, the respiratory organs are gills located in the mantle cavity. Land and freshwater mollusks have lungs.

3 purpose: commercial (for food, for obtaining pearls); crushed shells - feeding birds; pests of agricultural plants; intermediate hosts of helminths; destroyers of wood structures.

General characteristics of the class Gastropods

The class Gastropods belongs to the phylum Mollusca, subkingdom Multicellular, kingdom Animalia, superkingdom Eukaryotes, empire Cellular. There are about 90,000 species in the class (grape snail, slugs, small pond snail, etc.). According to their lifestyle, these are free-living organisms, they live in the seas and fresh water bodies, and there are terrestrial species. The body of gastropods is three-layered, asymmetrical, ranging in size from 2-3 mm to 60 cm, oblong in shape, convex on the back.

The body is divided into head, torso and leg; covered with a mantle and enclosed in a shell. The shell is entire, sometimes reduced. The head on the ventral side has a mouth, and on the dorsal side there are 1-2 pairs of tentacles and a pair of eyes. The front pair of tentacles is the organ of touch; at the top of the second pair there are eyes. The front part of the head, which bears the mouth, often extends into a long trunk. The leg is a muscular abdominal outgrowth with a flat, crawling sole. Movements are carried out by contracting the leg muscles. The trunk or visceral sac in most species protrudes above the leg in the form of a large curled sac. On the body, in a downward direction, a fold of integument is formed - a mantle fold, under which there is a mantle cavity.

The nervous system is of a scattered-nodular type. There are 5 pairs of large nerve ganglia located in different parts body and interconnected by cords. Nerves extend from the nodes to the organs. The sense organs - touch and vision - are located on the head.

The digestive system is represented by the intestinal tube, which is divided into sections: mouth, pharynx, esophagus (in some species it has an extension - goiter), stomach, midgut and hindgut. In the pharynx there is a tongue with cuticular thickenings, the so-called jaws. The ducts of the salivary glands flow into the pharynx; their secretion in some predatory species contains free sulfuric acid (up to 4% strength). The duct of the liver flows into the saccular stomach. Liver secretions break down carbohydrates. The process of absorption of nutrients, deposition of glycogen and fat occurs in the liver. The hindgut opens with powder outwards.

The excretory system is a kidney of the metanephridial type, which removes liquid metabolic products from the coelom to the mantle region.

The circulatory system is not closed. There is a heart, consisting of a ventricle and atrium, and blood vessels. The blood in the heart is arterial.

The respiratory system in most aquatic species is represented by gills, in terrestrial species - by primitive lungs, and some species breathe over the entire surface of the body. The lungs are special pockets of the mantle. Their walls are densely intertwined with a network of blood capillaries.

Reproductive system. Most species are hermaphrodites, but there are also dioecious species. Cross fertilization. Development is direct. Meaning: harmful– pests of agricultural crops, intermediate hosts in the development cycle of helminths, useful– commercial object (food, shells for crafts).

General characteristics of the class Bivalve

The class Bivalves belongs to the phylum Molluscs, subkingdom Multicellular, kingdom Animalia, superkingdom Eukaryotes, empire Cellular. There are 16,000 species in the class - the toothless mussel, sea and freshwater pearl mussels, oysters, mussels, blackbird (shipworm), etc.

Bivalves live in marine and fresh waters, lead a free lifestyle. The body dimensions of bivalve mollusks range from several cm to 2 m. The body of bivalve mollusks is three-layered, bilaterally symmetrical, consisting of a trunk and legs (the head is reduced), enclosed in a bivalve shell. The shell valves are connected to each other by an elastic ligament, which is located on the dorsal side of the animal. In addition, the doors are connected with a “lock”. This is a connection with the help of odontoid processes of the dorsal edge of one valve, which enters the corresponding pits of the dorsal edge of the other valve. To close the shell valves, there are closing muscles. The shell consists of three layers: a thin outer stratum corneum, a thick middle calcareous layer and a thin inner nacreous layer.

The body of bivalves is covered with a mantle, which forms two folds on the sides. Between the body and the folds is the mantle cavity. In many species, the mantle folds can grow together in places, forming openings (siphons), usually three or two small posterior ones and one large one. The upper rear opening serves to remove water and excrement from the mantle cavity, the lower one serves to introduce water into the mantle cavity, which serves for respiration and brings food. A leg sticks out through a large hole. Along the free edge of the mantle there may be tentacles and eyes. Both shell valves are distinguished by the outer epithelium of the mantle.

The leg is a muscular outgrowth. In many species it is equipped with a flat crawling sole. In some species it is flattened on the sides and sharpened like a knife blade, so it is used not so much for crawling as for digging sand or silt in which animals hide. In immobile forms (mussels, oysters), the leg is reduced or disappears. A number of species have a special gland (byssus) on the sole of the foot, which secretes viscous threads of secretion that quickly hardens in water. With the help of these threads the animal is attached to underwater objects.

The nervous system is scattered and nodular. It usually consists of 3 pairs of ganglia: peripharyngeal, pedunculated and located under the hindgut. The ganglia are connected to each other by nerve trunks. Sense organs are poorly developed: eyes, balance organs, chemical sense organs.

The digestive system begins with the mouth opening, surrounded by two pairs of tentacles, followed by a short esophagus, which passes into a rounded stomach, followed by the midgut and hindgut, which opens powdery into the mantle cavity. Bivalves do not have a tongue, pharynx, jaws, or salivary glands in their digestive system. Their food is plankton.

The excretory system consists of two kidneys of the metanephridial type - tubular sacs that carry liquid metabolic products from the coelom (pericardial space) to the outside.

The circulatory system is not closed. The heart consists of a ventricle and two atria, located on the dorsal side. The respiratory system is represented by gills. Reproductive system - most species are dioecious. Sex glands: testes and ovaries are paired and open into the mantle cavity, where insemination occurs. There is no sexual dimorphism. Development is external, with incomplete metamorphosis.

Meaning: useful– commercial (oysters, scallops, mussels are used as food; lime flour is prepared from the shells, which is used as animal feed; pearls and nacre are obtained from barley and pearl mussels); harmful– pests of woody structures (ships, piles, houses).

GENERAL CHARACTERISTICS

TYPE CHORDATES

The integument of the body is represented by skin, consisting of multilayered epithelium, skin itself and their derivatives (scales, feathers, hair).

Despite the diversity of species, all chordates have a common structural plan and differ from representatives of other types in four main characters.

1. They have an internal axial skeleton, represented by a notochord. It either remains in adult animals for life, or is replaced by a cartilaginous or bony skeleton - the spinal column. The notochord is a flexible elastic rod that develops from the endoderm and consists of highly vacuolated cells.

2. The central nervous system is located on the dorsal side above the notochord. It looks like a tube stretching along the body and has an internal cavity - the neurocoelum. The neural tube develops from the ectoderm and in vertebrates differentiates into the brain and spinal cord.

3. On the anterior section of the digestive tube (pharynx) of the embryo, the gill apparatus develops. It is represented by gill slits that pierce the wall of the pharynx, and a skeleton (visceral arches). The gill apparatus either remains throughout life as an organ water breathing, or is reduced during the development of the embryo.

4. The central circulatory organ - the heart or a vessel replacing it - is located on the abdominal side and is formed in the embryo under the digestive tube.

All chordates are three-layered animals, have bilateral symmetry of the body, have a secondary body cavity and a secondary mouth. They have major organ systems: musculoskeletal, nervous, digestive, excretory, circulatory, respiratory, reproductive and endocrine.

3meaning: are a link in the general food chain, used by humans (meat, eggs, fat, fluff, feathers, wool, leather, snake venom); are intermediate hosts or carriers of human pathogens, etc.

General characteristics of the Lancelets class

The class Lancelets belongs to the subphylum Lancelets, the phylum Chordata, the subkingdom Multicellular, the kingdom Animalia, the superkingdom Eukaryotes, and the empire Cellular. Modern lancelets include 20 species of small fish-like animals. They live in the seas in the zone of coastal sands. They lead a bottom lifestyle, burying themselves in the sand. They feed passively on plankton.

The body of lancelets is narrow, elongated, flattened laterally. Dimensions 8-10 cm. On the dorsal side there is a fold of skin - the dorsal fin. The caudal end of the body is edged with an unpaired caudal fin, which continues on the ventral side only in the posterior part, and paired metapleural folds run along the sides of the body (Fig. 61).

The skin of the lancelet is formed by smooth skin, consisting of two layers: single-layer epithelium and the skin itself, consisting of gelatinous tissue. Under the skin, striated muscles are located in the form of separate segments, with connective tissue layers lying between them. The axial skeleton of lancelets is the notochord. It lasts the entire life of the animal. There are supporting septa around the notochord and neural tube and between muscle segments. The skeleton of the unpaired fin consists of dense gelatinous rods. Similar rods form the skeleton of the gill apparatus. The internal organs of lancelets lie in a secondary cavity - the coelom.

The central nervous system is represented by a tube located above the notochord. It is not differentiated into the brain and spinal cord. The neural tube contains the light-sensitive ocelli of Hesse. Peripheral nerves arise from the neural tube in the form of paired dorsal and ventral roots, one pair for each segment.

The digestive system begins with the mouth, which lies deep in the preoral funnel, followed by the pharynx, midgut and hindgut, which opens outward through the anus. The voluminous pharynx makes up half the entire length of the intestinal tube. Its walls are cut through by 150 pairs of gill slits leading into the peribranchial cavity, which opens outwards with an opening - the atrial pore. At the bottom of the pharynx there is a groove covered with ciliated epithelium. Food particles are carried by a current of water into the oral cavity, then along the groove of the pharynx by the cilia of the epithelium they move into the midgut. The duct of the intestinal outgrowth opens into it, performing the functions of the digestive gland. The process of digestion and absorption of nutrients occurs in the midgut. Fecal masses are formed in the hindgut, which are thrown out. At the same time, the pharynx performs the function of breathing. The gill septa are densely intertwined with capillaries. Water, washing the gill membranes, releases oxygen into the blood of the capillaries.

The circulatory system is closed, there is one circle of blood circulation, there is no mixed blood. There is no heart; its role is played by the pulsating abdominal aorta. The blood is colorless.

The excretory system of lancelets is represented by paired metamerically arranged nephridia located on the sides of the pharynx. Each nephridia is a tube, one end facing the whole; the opposite end of the nephridia opens into the atrial cavity, from where excretory products are discharged out through the atrial pore.

The reproductive system is represented only by gonads: testes in males and ovaries in females. The gonads are located in paired metameric rows on the sides of the body. The reproductive system does not have excretory ducts. After maturation, the germ cells, when the gonad wall ruptures, enter the atrial cavity and are then released into the external environment. Insemination and development in lancelets is external.

Meaning: are a link in the overall food chain; are of great theoretical importance for understanding the origin of vertebrates.

General characteristics of the class Bony fish

The class Bony fish belongs to the superclass Pisces, the Anamnia group, the embryo does not have an aquatic shell), the subphylum Vertebrates, the phylum Chordata, the subkingdom Multicellular, the kingdom Animalia, the superkingdom Eukaryotes, the empire Cellular. There are about 20,000 species in the class. All of them live in water, lead a free lifestyle, many species are predators. Fish are three-layered, bilaterally symmetrical animals. Body sizes range from several cm to several meters. The body shape is streamlined, flattened laterally, which promotes rapid movement in the water (Fig. 62).

The body is divided into head, trunk and tail. The integument of the body is skin, consisting of two layers: stratified epithelium and the skin itself with its derivatives (scales). The skin contains many glands that secrete mucus, which reduces friction when the fish moves. Movement is carried out by paired pectoral and ventral fins, as well as unpaired dorsal, caudal and anal fins. The mobility of fins, gill covers and body bends are provided by striated muscles that lie under the skin. The muscular system retains a metameric structure.

The skeleton of a fish consists of a spine, ribs, fins and a skull. The spine is divided into the trunk and caudal sections, formed by numerous vertebrae, the upper arches of which limit the spinal canal, where the spinal cord is located. In the trunk section of the spine, the ribs are attached to the vertebrae. There are no ribs in the caudal region. The skull is divided into a dorsal part (the cranium), where the brain, organs of vision, smell and taste are located, and an abdominal part, which forms gill arches and jaws with conical teeth for holding food. The body cavity is secondary.

The nervous system is represented by the brain and spinal cord and the nerves extending from them. The brain is divided into 5 sections: forebrain, intermediate, midbrain, cerebellum and medulla oblongata. The forebrain hemispheres are poorly developed and serve as the highest olfactory center. Most large sizes reaches the midbrain. Due to the complex coordination of movements, the cerebellum is well developed. Well developed sense organs. The olfactory organ is represented by a pair of closed olfactory sacs. The eyes are equipped with eyelids, the lens is almost spherical in shape, adapted for vision at close distances. The organ of hearing and balance is represented only by the paired inner ear. The taste organs - microscopically small taste buds - are located not only in the oral cavity, but also on the surface of the body. The peculiar sensory organs of fish are the lateral line organs. They are located in a special channel running along the sides of the body from the head to the caudal fin. The channel communicates with the external environment through numerous small holes. The lateral line organs allow the fish to orient itself in relation to the direction of water movement.

The digestive system begins with the oropharyngeal cavity, from which the esophagus arises. The stomach is not always separated from the midgut, but is highly extensible, especially in predatory fish. Some of them can swallow prey equal in size to themselves. The duodenum extending from the stomach sometimes forms several blindly ending appendages. It receives secretions from the liver and pancreas. The intestinal tube is differentiated into the small and large intestine. The latter opens with the anus outward.

Many species of bony fish have a hydrostatic organ - a swim bladder. When the bubble is filled with gas, the specific gravity of the fish decreases, and it passively rises to the surface of the water, and when the amount of gas in the bubble decreases, it sinks to the bottom of the reservoir. Gas enters the swim bladder from the blood capillaries that surround the wall of the bladder.

The excretory system is represented by paired primary (trunk) kidneys. They lie on both sides of the spine in the form of ribbon-like bodies. From the kidneys come the ureters, which merge into one unpaired duct that flows into the bladder. The latter opens outward with a special opening behind the anus.

The circulatory system of bony fish is closed, with one circle of blood circulation. Either arterial or venous blood flows through the vessels. The heart is two-chambered, consisting of one ventricle and one atrium. The blood in the heart is venous; it is collected from internal organs and tissues into a common vessel that flows into the atrium. From it, blood enters the ventricle, and then through the abdominal aorta is sent to the gills, where gas exchange occurs. Arterial blood from the gills collects in the dorsal aorta, which, breaking up into smaller arteries, delivers arterial blood to organs and tissues.

The respiratory system of bony fishes is represented by the gill apparatus - gill arches, gill filaments and gill covers. Water washes the gill filaments through the gill slits, releases the oxygen dissolved in it into the blood, and becomes enriched carbon dioxide and comes out from under the gill cover. Each gill septum bears a gill consisting of two semi-branchs.

The reproductive system is represented by paired testes in males, and paired ovaries in females. The vast majority of fish are dioecious animals, but there are also hermaphrodites (sea bass, sea crucian carp). Insemination and development external.

Eggs (eggs) and seminal fluid with sperm are released into the external environment, where fertilization occurs. This process is called spawning. In the fertilized egg, the embryo develops, which then leaves the egg shell and turns into a larva. The latter grows into a fry, which, upon reaching sexual maturity, turns into an adult.

General characteristics of the class Amphibians

The class Amphibians (Amphibians) belongs to the Anamnia group, the subphylum Vertebrates, the phylum Chordata, the subkingdom Multicellular, the kingdom Animalia, the superkingdom Eukaryotes, and the empire Cellular. The class is divided into 3 groups: the Legless group (caecilians), the Tailed group (newts, salamanders); detachment Tailless (frogs, toads). In total there are about 2000 species in the class. This is a dying class (Fig. 63).

The distribution of amphibians is limited to areas of high temperature and humidity. Habitat: shores of fresh water bodies, damp soils. In tropical rainforests, some species have adopted an arboreal lifestyle. Most amphibians are sedentary. Their movements are monotonous (which is due to unstable body temperature, poor development of the lungs and circulatory system).

According to their lifestyle, they are free-living insectivores. Tailless amphibians have a short body, flattened in the dorsoventral direction. The hind limbs are longer than the forelimbs. In caudates, the body is elongated, laterally compressed, with a long tail and short legs.

The skin consists of two layers: the epidermis and the dermis with numerous glands that secrete mucus. Mucus covers the entire body, protecting the skin from drying out and promoting better gliding in water. In some species, mucus is poisonous, i.e. protective function. The skin of amphibians is penetrated by a dense network of blood vessels and performs the function of respiration in water.

The skeleton of amphibians is bony, consisting of a braincase, spine and limbs. The spine is divided into 4 sections: cervical, trunk, sacral and caudal. The cervical and sacral regions appear for the first time and have one vertebra each. In tailless animals, the vertebrae of the caudal region merge into one bone. The trunk vertebrae of tailed amphibians bear short ribs that do not reach the sternum. Anurans have no ribs. The free forelimbs include: shoulder, forearm, hand; rear - thigh, lower leg, foot. In typical cases, the limbs have five fingers. The forelimb girdle consists of paired crow bones, scapulae and clavicles. The hind limb girdle consists of three pairs of fused pelvic bones: the ilium, the ischium and the pubis. The braincase is small and flattened.

The muscles are striated, located in segments and provide movement. The muscles of the limbs are more significantly developed. The body cavity is secondary.

Nervous system - consists of the brain and spinal cord and the nerves extending from them. The brain consists of 5 sections: the forebrain, intermediate, midbrain, cerebellum and medulla oblongata. The forebrain is better developed than in fish and is clearly divided into two hemispheres. The cerebellum is poorly developed. The midbrain has visible thalamus. There are 10 pairs of cranial nerves leaving the brain. Spinal nerves arise from the spinal cord and form the brachial and lumbosacral plexuses.

Amphibians' sense organs become more complex. Paired olfactory capsules communicate not only with the external environment (nostrils), but also with the oral cavity, where the choanae open. In this regard, the nasal cavity becomes a through path through which air enters the lungs. The eyes are equipped with three pairs of eyelids, which protect them from drying out on land. The third eyelid is transparent, which allows you to see well in water, while at the same time protecting the eyeball from damage. The lens flattens, which increases the distance at which the animal sees objects. The structure of the hearing organ becomes significantly more complicated. It consists of two sections: the inner and middle ear, closed by the eardrum. In water, the middle ear is covered by a fold of skin.

Digestive system - begins with the oropharyngeal cavity, which passes into the esophagus. The oral cavity contains conical teeth and a tongue. The ducts of the salivary glands also flow here. A short esophagus leads to a separate stomach. This is followed by the duodenum, where the ducts of the liver and pancreas flow. The large intestine receives the ducts of the reproductive and urinary systems and forms the cloaca.

The excretory system is represented by two primary kidneys, two ureters and a bladder. The kidneys of amphibians in the form of ribbons are located along the spine and remove liquid waste products partly from the body cavity, and mostly from the blood through the ureter into the cloaca, where the bladder opens.

Respiratory system: breathing in amphibians is cutaneous-pulmonary. On land, the respiratory organs are the lungs - paired bags with a highly extensible cellular wall, permeated with dense blood vessels. In water, the function of respiration is performed by the skin.

The circulatory system is closed. In connection with the appearance of lungs, a second (pulmonary, pulmonary) circulation develops in amphibians, but the separation of the circulation circles is incomplete and there is only one ventricle, so in most of the arteries of the systemic circle the blood is mixed (with the exception of the carotid arteries, which carry blood to the head).

The heart is three-chambered, consisting of two atria and one ventricle. One large vessel departs from the heart - the conus arteriosus, which divides into two aortic arches. The latter, bending around the heart on the right and left, merge into one large vessel - the dorsal aorta, from which smaller vessels depart to all organs and tissues.

Reproductive system - all amphibians are dioecious animals. Gonads are paired. The seminiferous tubules open into the ureter. Eggs from the ovary enter the body cavity, from there they are released through the oviducts into the cloaca. Insemination is external, development is external with complex metamorphosis.

3limited value. Destroy harmful insects, their larvae, small rodents; are a link in the overall food chain; used in some countries for human food; are the object of scientific research (frog). Aromorphoses of amphibians - a five-fingered limb of the terrestrial type; lungs – organ of atmospheric respiration, second (small, pulmonary) circle of blood circulation, 3-chamber heart; middle ear and complication of the organ of vision.

General characteristics of the class Reptiles

Class Reptiles (Reptiles) are true terrestrial animals. The class belongs to the Amniota group (their embryo has a water membrane - the amnion), to the Vertebrate subphylum, the Chordata type, the Multicellular subkingdom, the Animal kingdom, the Eukaryotic superkingdom, and the Cellular empire. Modern reptiles are divided into 4 orders: the Beaked order (Gatteria), the Scaly order (snakes, lizards, chameleons), the Turtle order, and the Crocodiles order. In total, there are about 6000 species in the class (Fig. 64).

Reptiles are cold-blooded animals, so they have adapted to live in tropical forests, deserts, and waterless steppes. Reptiles living in water (crocodiles, turtles) are secondary aquatic, since their ancestors switched from a terrestrial lifestyle to life in the water. Among reptiles leading a free lifestyle, there are herbivores and predators. Body sizes range from several cm to several meters.

The body of reptiles is divided into head, neck, torso, tail and limbs. It is covered with dry skin, devoid of glands, which gives appendages - scales, scutes. Only some species have preserved odorous glands, the secretion of which repels or, conversely, attracts other animals. The skeleton is bony and is represented by the skull, spine, chest skeleton, girdles of the front and hind limbs, bones of the front and hind limbs. Skull with elongated jaws in the form of a snout.

The spine is divided into 5 sections: cervical, thoracic, lumbar, sacral and caudal. There are up to 8 vertebrae in the cervical region. The thoracic vertebrae are joined by ribs, which on the ventral side are attached to the sternum, forming the rib cage.

The lumbar vertebrae also bear ribs, the ends of which end freely.

The girdle of the forelimbs is formed by the sternum, two crow bones, two clavicles, and two shoulder blades. The free forelimbs consist of the shoulder, forearm and hand. The girdle of the hind limbs is formed by three pairs of fused pelvic bones: the ilium, the ischium and the pubis. The free hind limbs consist of the thigh, tibia and foot. The humerus and femur bones are located horizontally to the surface of the earth, so the body of reptiles sags and drags along the ground. The body cavity is secondary.

The muscular system is represented by striated and smooth muscles. For the first time, the intercostal muscles appear, taking part in the act of breathing. Powerful chewing and neck muscles develop.