Lesson summary on the topic: "Features of the structure and vital activity of insects." General characteristics of Insects
Insects are true terrestrial invertebrates. The class has about 1 million species. The body of insects is clearly divided into head, chest, and abdomen. The head is formed by four segments. The thoracic region consists of three segments, each with one pair of limbs. The second and third segments on the dorsal side usually bear a pair of wings. The abdomen consists of 8-12 segments.
general characteristics
A typical representative of this class is the cockchafer. Its length is 2-2.5 cm. The body shape is cylindrical. Color - light brown. There are characteristic triangular white spots on the sides of the abdomen.
The cockchafer is a typical representative of the class Insects
The cockchafer's head contains sensory organs and mouth parts. The sensory organs of insects are two compound eyes. In front of the eyes there is a pair of antennae with expanded plates at the end, which act as olfactory organs.
The organs of touch and taste are the palps. They are found in pairs on the lower lip and lower jaws. The oral organs include the upper and lower lips, upper and lower jaws. The upper lip and upper jaws are single-membered. The lower lip and lower jaws are polynomial.
Based on the nature of the structure of the oral organs in insects, they distinguish between gnawing, piercing-sucking, lapping, cutting-sucking and other oral apparatus, which is associated with the variety of food consumed by different insects.
The May beetle belongs to the order of beetles or Coleoptera. In insects belonging to this order, the first pair of wings has turned into hard elytra, which serve as a cover for the second pair of membranous wings used in flight.
Before taking off, the cockchafer lifts its elytra, moves them to the side and spreads the membranous wings folded under them. During flight, the wings perform the same role as the load-bearing planes of an airplane, and the elytra perform the same role as an airplane propeller.
The cockchafer's legs are equipped sharp claws, which helps it cling tightly to leaves and twigs.
The beetle's abdomen consists of 8 segments; they are visible only from the underside, since almost its entire upper part (with the exception of the pointed tip of the abdomen) is hidden by the elytra.
Insect feeding. The cockchafer feeds on young tree leaves. Swallowed food passes through the esophagus into a voluminous crop, and from it into the stomach, where it is ground by chitinous denticles. In the intestine, crushed food is finally digested and absorbed, and undigested remains enter the hind intestine and are thrown out through the anus.
Respiratory system in insects represented by tracheas. These are numerous branching tubes into which air enters through special openings - spiracles, or stigmas. The trachea distributes air throughout the body, reaching all organs. The work of the respiratory organs of insects is connected with the work of the muscular system of the abdomen: when it contracts, air is pushed out of the trachea, and when the abdomen expands, fresh air enters them.
Insect circulatory system represented by the heart and blood vessels. The heart and aorta are located on the dorsal side. Due to the fact that there is an extensive network of tracheas, the circulatory system is poorly developed and lacks the function of an oxygen carrier. The fluid circulating through the circulatory system is called hemolymph. It contains white blood cells.
Excretory organs of insects- numerous tubes (Malpighian vessels) flowing into the border of the middle and hind intestines. Their lumen is filled with grains of uric acid - the main product of dissimilation in insects. In addition, the fat body has an excretory function. Uric acid also accumulates in it, although it is not removed from the body, so its concentration in the fat body increases with age. The fat body is the “kidney” of storage. However, the main function of the fat body is the accumulation of reserve nutrients: fat, glycogen, protein.
Nervous system of insects built according to the type of abdominal nerve chain, but can reach a very high level of development and specialization. Central nervous system includes the brain, subpharyngeal ganglion and segmental ganglia of the ventral nerve cord located in the trunk. The brain has a very complex histological structure. In most insects, the ganglia of the ventral nerve cord are concentrated in the longitudinal direction.
May beetles reproduce sexually. The fertilized female burrows into the soil and lays eggs. Larvae develop in them and leave the egg shells at the end of summer. The larvae feed on humus.
In the fall, they penetrate deep into the soil, overwinter, and in the spring they rise to the soil surface and feed on the roots of herbaceous plants and pine seedlings throughout the summer. They overwinter again deep in the soil and only in the third summer the grown larvae are able to feed on the roots of shrubs and trees, as a result of which young trees often dry out.
The larva turns into a pupa only after it has overwintered for the third time and has greatly increased in size. This happens at the end of spring, and by autumn an adult cockchafer emerges from it. At first, its soft covers are colorless, then they harden and become colored. After overwintering in the ground again, the beetles crawl to its surface in the spring. Massive summers of them occur in the spring months at dusk.
The main damage to forestry is caused not by adult beetles, but by their larvae. This is due to the fact that starting from the second year, they feed on tree roots and destroy young plants and seedlings.
The natural enemies of cockchafers are birds (starlings, rooks) and mammals (moles, bats). These birds and animals must be protected in every possible way.
The class Insects unites more than 1 million species of arthropods, which are characterized by the division of the body into three sections: head, thorax and abdomen. There are three pairs of legs on the chest, the abdomen is devoid of limbs. Most have wings and are capable of active flight.
© External structure. On the head of insects there are complex (compounded) eyes; in some species, in addition to them, there are also simple eyes. There are four pairs of appendages on the head: the first pair are antennae (antennae), olfactory organs, the remaining three pairs form the oral apparatus. The upper lip covers the upper jaws. The second pair of oral appendages forms the upper jaws, the third pair - the lower jaws, the fourth pair fuses to form the lower lip. There may be a pair of palps on the lower jaw and lower lip. The oral apparatus includes the tongue, a chitinous protrusion of the floor of the oral cavity. Depending on the type of nutrition, oral apparatus can be of various types (Fig. 128):
¨ gnawing type - characteristic of insects that feed on tough plant foods (beetles, orthoptera, cockroaches, etc.) - the most ancient, original type of mouthparts;
¨ gnawing - sucking mouthparts of bees;
¨ piercing - sucking mouthparts of bedbugs and mosquitoes;
¨ sucking mouthparts of butterflies;
¨ licking mouthparts of flies.
The thorax consists of three segments: prothorax, mesothorax and metathorax. On each segment there is a pair of legs; on the meso- and metathorax in flying species there are most often two pairs of wings. The limbs are articulated, forming a system of levers with the help of joints. Due to the way of life, the legs are running, jumping, swimming, digging, grasping and others.
The abdomen of the most evolutionarily advanced ones is characterized by a decrease in the number of segments (from 11 to 4-5 in Hymenoptera and Diptera). Lower insects have paired limbs on their abdomen; in higher insects they are modified into an ovipositor or other organs.
The integument consists of a cuticle and hypodermis, which protect insects from mechanical damage, water loss, and are the exoskeleton.
Insect muscles, according to their histological structure, are striated; they are distinguished by high differentiation and the ability to contract at a very high frequency (up to 1000 times per second).
© Digestive system begins with the oral extremities and the oral cavity, into which the ducts of the salivary glands open. The salivary glands can mutate and produce a silky thread, turning into spinning glands (in the caterpillars of many species of butterflies). The foregut includes the pharynx, esophagus, and in some types of insects there is an extension - a goiter. In species that feed on solid food, behind the crop there is a chewing stomach, in which there are chitinous folds - teeth that facilitate the grinding of food. The midgut may have blind projections that increase the absorption surface. The hindgut ends at the anus. At the border between the midgut and hindgut, the intestinal lumen opens with numerous blindly closed Malpighian vessels (Fig. 129).
Many insects harbor protozoa and bacteria in their intestines that can digest fiber. Among insects there are omnivorous species (cockroaches), herbivorous, and predatory. There are species that feed on carrion, rotting products - manure, plant debris. Some species have adapted to digest low-nutrient substances such as wax and hair.
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Rice. 130. The structure of the trachea of insects.Actively moving insects can perform respiratory movements by expanding and contracting the abdomen. Many larvae living in water (dragonflies, mayflies) have so-called tracheal gills, there are no stigmas, the tracheal system is closed. Some larvae living in water have gills that do not have tracheae; gas exchange occurs only through the integument; in these cases, oxygen is transported by the hemolymph.
Circulatory system relatively poorly developed in insects. The heart is located in the pericardial sinus, on the dorsal side of the abdomen, and is a tube, blindly closed at the posterior end, divided into chambers and having paired openings with valves on the sides -ostia. Each chamber of the heart has muscles that provide its contraction. Hemolymph moves to the anterior part of the body, into a single vessel - into cephalic aorta- and pours into the body cavity. Through numerous openings, hemolymph enters the pericardial sinus, then through the ostia, with the expansion of the cardiac chamber, it is sucked into the heart (Fig. 131).
Hemolymph has no respiratory pigments and is a yellowish liquid containing phagocytes. Its main function is the transport of nutrients to all organs and metabolic products to the excretory organs. The respiratory function of the hemolymph is insignificant, but in some aquatic insect larvae (bloodworms, bell-bellied mosquito larvae) the hemolymph contains hemoglobin, is colored bright red and is responsible for the transport of gases.
© Excretory organs. In insects these include the Malpighian vessels and the fat body. Malpighian vessels (up to 200 or more) absorb metabolic products from the hemolymph. The products of protein metabolism are converted into uric acid crystals, the liquid is actively reabsorbed by the vascular epithelium and returned to the body, and the uric acid crystals enter the hindgut. The fat body of insects, in addition to its main function - the accumulation of reserve nutrients, also serves as a “storage kidney”; it contains special excretory cells that are gradually saturated with sparingly soluble uric acid.
© Nervous system. The central nervous system of insects consists of the brain, subpharyngeal ganglion and segmental ganglia of the ventral nerve cord (Fig. 132). The peripheral nervous system is represented by nerves extending from the central nervous system and sensory organs. The trend toward ganglion fusion continues; in some insects, the thoracic and abdominal segmental ganglia merge to form the thoracic and abdominal ganglia. The most complex brain develops in social insects: ants, bees, termites.
The sensory organs of insects are diverse and complex. They have compound eyes and simple eyes. Compound eyes are made up of ommatidia, the number of which is various types insects are not the same. In dragonflies, each eye consists of 28,000 ommatidia; in ants, especially in individuals living underground, the number of ommatidia is reduced to 8 - 9. Some insects have color vision, color perception is shifted towards short-wavelength rays: they see the ultraviolet part of the spectrum and do not see red colors. Mosaic vision. The role of simple ocelli has not been fully studied, but it has been proven that they perceive polarized light.
Many insects are able to make sounds and hear them. The hearing organs can be located on the shins of the front legs, at the base of the wings, and on the anterior segments of the abdomen. The organs that produce sounds in insects are also diverse.
The olfactory organs are located mainly on the antennae, which are most developed in males. The taste organs are located not only in the oral cavity, but also on other organs, for example, on the legs of butterflies, bees, flies, and even on the antennae of bees and ants.
On the entire surface of the insect's body there are sensory cells that are connected to the sensitive hair. When humidity, pressure, wind blow, or mechanical action changes, the position of the hair changes, the receptor cell is excited and transmits a signal to the brain.
Many insects perceive magnetic fields and their changes, but where the organs that perceive these fields are located is still unknown.
© Reproductive organs. Insects are dioecious. Many insects exhibit sexual dimorphism - males can be smaller (in many butterflies) or have a completely different color (gypsy moth butterflies), sometimes males have larger antennae, in some species they develop strongly individual organs- upper jaws of a male stag beetle. Males have testes in their abdomen, from which vas deferens extend, ending in an unpaired ejaculatory duct. Females have two ovaries; they open into paired oviducts, which below connect into an unpaired vagina.
During mating, the male's seed is introduced into the copulatory bursa and spermatic receptacle, from where it enters the vagina, where fertilization of the eggs occurs. In some species, sperm in the spermatic receptacle remain alive for several years. The queen bee, for example, has a mating flight once in her life, and she lives and lays eggs for 4-5 years.
There are known cases in insects parthenogenetic reproduction (without fertilization). Throughout the summer, female aphids give birth to larvae from unfertilized eggs, from which females develop; only in the fall, both males and females are formed from the larvae, mating occurs, and the fertilized eggs overwinter. From parthenogenetic The testicles of social Hymenoptera produce males. The gonads of drones in bees remain haploid, and the body cells restore diploidity.
© Development insect life is divided into two periods - embryonic, including the development of the embryo in the egg, and postembryonic, which begins from the moment the young animal emerges from the egg. Postembryonic development occurs with metamorphosis; according to its nature, they are divided into insects with incomplete transformation and insects with complete transformation.
To insects with complete transformation refer to insects in which the larva differs sharply from the adult stage of the imago; there is a stage pupae, during which the larva’s body undergoes a restructuring and the organs of an adult insect are formed. An adult insect emerges from the pupa. Insects that have fully metamorphosed as adults do not molt. Insects with complete transformation include, for example, the orders: Coleoptera, Hymenoptera, Diptera, Lepidoptera and others.
In insects with incomplete transformation there is no pupal stage; a larva (nymph) emerges from the egg, similar to an adult insect, but the wings and gonads are underdeveloped. The larvae molt several times, and after the last molt, winged adult insects with developed gonads emerge. Insects with incomplete transformation include, for example, the orders: Cockroaches, Mantisidae, Orthoptera, Lice, Homoptera and others.
In insects of the order Coleoptera(Coleoptera) the first pair of wings is transformed into hard elytra, mouthparts of the gnawing type. U chafer The development of the larva continues underground for several years. The larva has a well-defined head with a gnawing-type mouthparts, three pairs of jointed limbs, and is completely unlike a beetle. The first year the larva feeds on humus, the second - on the roots of grasses, the third - on the roots of shrubs and trees, which causes great harm to young tree plantations. In the fourth year, at the end of spring, the larva turns into a pupa and in the fall a young beetle emerges from the pupa. The beetle appears on the soil surface in the spring of next year. The larvae of bark beetles, longhorn beetles, cause great harm to forests and gardens, damaging the wood of trees; the Colorado potato beetle is a dangerous pest of potatoes, the leaves of which feed on both the larvae and adult beetles. The larvae of click beetles are called wireworms; they harm cereal crops by gnawing on the roots. Bread beetles feed on soft grains of cereals, and their larvae gnaw on the roots.
Predatory beetles are of great benefit ground beetles, ladybugs and their larvae feeding on aphids. Many beetles are orderlies, cleaning nature from corpses and manure ( scarabs, dung beetles, carrion eaters, gravediggers).
Butterflies have a sucking mouthparts; two pairs of large wings are covered with chitinous scales that form bizarre and complex patterns. Coloring may be cautionary, warning about inedibility, patronizing, expressed in resemblance to a protected animal or inedible object. At the same time, the color wears identification character.
Butterfly larvae - caterpillars - have a worm-like shape, with a gnawing-type mouthparts on their heads. On the thoracic segments they have three pairs of articulated legs, the rest are unsegmented false legs. Among Lepidoptera there are many species whose caterpillars are pests of forests and gardens. By feeding on leaves, they cause great harm to deciduous trees. By visiting flowers, lepidoptera play a significant role in pollination. Silkworm used by humans to produce natural silk. Currently, the silkworm is wildlife does not occur.
Many Lepidoptera have become rare and are listed in the Red Books.
The wings are membranous, two pairs, the second pair is smaller than the first, during flight they are linked into a single flying surface using hooks. The head has a pair of compound compound eyes and three simple ocelli. Among them there are pests ( sawflies, horntails, gallworms), and species useful to humans. Domestic bees are suppliers of honey, wax, propolis; bumblebees- excellent pollinators, ants destroy a huge number of harmful insects.
Riders ( trichogramma, telenomus, white-tailed ichneumon) lay their eggs in the eggs of other insects ( egg eaters), into their larvae ( larvae eaters) and even in adult insects ( imagoeders). The larvae that emerge from them eat their prey, reducing the number of insects harmful to humans. Controlling harmful activities through the use of natural enemies is called biological method of control.
This order includes the most highly organized insects, which have one pair of wings, the second pair is transformed into an organ of balance - halteres. Mouthparts piercing or licking. The larvae are legless, flies and headless. The negative significance of dipterans is great: they are mechanical carriers of pathogens of intestinal infections and helminth eggs; Some dipterans are bloodsuckers and can carry pathogens of serious diseases. For example, tsetse fly- carrier of the causative agent of sleeping sickness, mosquitoes- leishmaniasis, horseflies- tularemia and anthrax, malaria mosquito(genus Anopheles) - malaria.
Unlike other mosquitoes, the female analaria mosquito lays her testicles singly, without sticking them to each other. The eggs have air chambers and float on the surface. The eggs hatch into larvae that are located parallel to the surface of the water, and not at an angle, like the larvae of squeaking mosquitoes (of the Culex genus). When landing, the abdomen of the malaria mosquito is at an angle to the surface (Fig. 133), while that of the squeaking mosquito is parallel to the surface. But mosquitoes of the genus Culex also Far East spread heavy viral disease- Japanese encephalitis.
Cause great harm to livestock gadflies. These large flies do not feed, their mouthparts are not developed. Some lay their eggs or larvae on the surface of the body of sheep, horses, and cattle. Others go into the nasal cavities of animals. The larvae settle under the skin, in the stomach, nasopharynx, frontal and maxillary sinuses, bringing great suffering to their owners. Eventually, the larva enters the soil, where it pupates.More than 20,000 species of insects with incomplete metamorphosis. Characteristic are the hind legs of the jumping type and the gnawing mouthparts.
The most famous of this order are the insects from the Grasshopper family, the Cricket family, the Mole cricket family, and the Locust family. Grasshoppers have long antennae, feed on plant and animal matter, and are usually green in color. Great harm agriculture bring some types of locusts, destroying crops on hundreds of hectares. Their antennae are short and their ovipositor is short and hook-shaped. Mole crickets cause significant harm, often damaging the underground organs of plants.
Municipal budget educational institution
"Average comprehensive school No. 31 named after the Heroes of Svir"
G. Ulyanovsk
Biology lesson project for 7th grade
Biology teacher - Makarova I.V.
Subject: “Features of the structure and vital activity of insects”
Type of training session: discovery of new knowledge.
Forms of organization of the educational process: lesson - reflection, laboratory work.
Teaching methods: verbal - visual, research, problem presentation, heuristic conversation with elements of literary reading.
Forms of organizing students' educational activities: individual, group, frontal.
Goals : reveal the structural features of insects in connection with life in the ground-air environment; deepen knowledge about the parts of the insect’s body, the organs located on them, and their meaning; continue to develop the skills to work with a textbook, use natural objects and drawings to perform laboratory work; to form a scientific worldview based on knowledge about the relationship of the organism with its environment; contribute to the formation of an environmental culture based on the recognition of the value of life in all its manifestations and the need for a responsible, careful attitude towards environment; formation of communicative competence in communication and cooperation with peers in the process of educational, training and research activities.
Equipment: collections of insects, magnifying glasses, tables, exhibition of books and magazines, laboratory notebooks, " Great encyclopedia fauna" (Beiko V.B., M.: Rosman), interactive disc "Visual Biology", microslides "Mouthparts of a mosquito", "Limb of a bee", phonogram "A grasshopper sat in the grass", video fragment and illustrations http:// files.school-collection.edu.ru/dlrstore/.
Lesson plan: 1) Org. moment – 1 min
2) Knowledge test – 5 min
3) Studying new material – 20 min
4) Physical exercise – 1 min
5) Consolidation – 10 min.
6) Summing up the lesson – 2 min
7) Homework – 1 min
During the classes
1) Org. moment.
Hello guys! Today in the lesson you will learn about the structural features and vital functions of insects in connection with the ground-air habitat, about the parts of the body of insects, the organs located on them, and their significance. The result of our work will be the table “External structure of insects” in laboratory notebooks.
2) Check of knowledge.
At the beginning of the lesson, we will test your knowledge on the topic “Type Arthropods”.
Give a general description of Arthropods:
The body of arthropods is covered with a dense 1 (chitinous) covering - the exoskeleton.
They have 2 joints (limbs).
Body cavity 3 (mixed).
Circulatory system 4 (open).
The organs of the 5 senses are varied and well developed.
Arthropods are the 6th (most numerous) type of animal in terms of the number of species.
Arthropods descended from ancient 7 (polychaete) worms.
Originally there were 8 (aquatic) animals.
From them evolved modern crustaceans, arachnids and 9 (insects).
3) Learning new material
*Teacher's story with demonstration of visual aids.
Externally, insects are very diverse - beetles, butterflies, flies, dragonflies and others. The body of insects is divided into segments, the boundaries between which have the form of notches. From the word “to incise” the name “insects” arose. They have two characteristic features: a hard chitinous cover and the presence of three pairs of limbs. The compacted outer covers not only protect internal organs from damage, but also prevent the evaporation of water from the body. The design of the skeleton allows insects to have very small sizes (less than 1 mm), which contributed to their adaptation to living in a wide variety of conditions, and, consequently, to the emergence of more and more new groups and species in the process of evolution. Therefore, there are a lot of insects, more than 1 million species, which account for 70% of the total number of animal species. Insects are often called six-legged; with the method of walking and running that insects have developed, a further reduction in the number of legs is impossible. The fact is that when walking, at each individual moment in time, the insect’s body rests on 3 legs: the front and back on one side and the middle on the other. This achieves a stable body position with support on 3 points.
*Working with the textbook, paragraph 26.
The body of insects is divided into head, thorax and abdomen. On the head there is a pair of compound eyes, one pair of antennae and mouthparts, on the chest there are three pairs of legs and (in most) wings; Insects have no legs on their abdomen. The chitinous coverings of insects prevent water loss. Insects breathe using tracheas. The circulatory system is not closed; the nervous system consists of the peripharyngeal ring and the ventral nerve cord. Insects are the most numerous and diverse group of animals. More than a million species of insects live on Earth. They have mastered all habitats and are found everywhere (with the exception of seas and oceans).
Insects have sensory organs and mouthparts on their heads. What are they?
* Speech by 1 student:
The sense organs are primarily the organs of vision, smell and touch. Two eyes are located on the sides of the head and consist of many tiny facets of identical structure, each of which is like an optical tube; the image in insects is mosaic. In some insects, such as dragonflies and flies, the eyes occupy most of the head, which allows them to simultaneously see objects located in front of them, as well as from the side, below and partially behind. In dragonflies, the compound eye has up to 28,000 facets. Insects that live in the dark, such as in caves, do not develop eyes. In addition to compound eyes, bees also have simple eyes.
The main organs of smell and touch in insects are the antennae, which can have a variety of appearances: filamentous, feathery, lamellar, etc. The olfactory organs of males more often serve to search for unfertilized females, which release specific odorous substances (pheromones) into the air, perceived by males even a few minutes later. kilometers. In insects, the male olfactory organs ensure the meeting of the sexes. The olfactory organs of females are adapted to search for the habitat in which the larvae develop. Insects use odors to regulate their vital functions in such complex ways.
* Working with the textbook:
Look at Figure No. 99 “Structure of the oral apparatus.”
Find in the text of the paragraph which insects have which oral apparatuses are developed.
In a cockroach it is gnawing, in a bee it is gnawing-licking, in a butterfly it is sucking, in a fly it is filtering, in a mosquito it is piercing-sucking. Why do insects have different types mouthparts?
*Speech by 2 students:
Insects have different types of mouthparts, which is associated with the nature of the food consumed. In insects that feed on solid food, the gnawing mouthparts consist of the upper and lower jaws, upper and lower lips. All these are modified limbs. Beetles, dragonflies, locusts, and cockroaches have gnawing mouthparts. Some insects do not feed and their mouthparts are not developed. Fly larvae do not have heads and feed by secreting digestive juices into the accumulation of food and absorbing the already semi-digested liquid gruel with the surface of the body.
In insects that feed on liquid food - plant juices or animal blood, the oral organs of the sucking type are transformed into a thin and long proboscis with a channel inside through which food is absorbed. The sucking mouthparts with a long proboscis allow butterflies to extract nectar from the very thin corollas of flowers, while pollinating plants, so the extermination of butterflies will lead to the disappearance of beautiful flowering plants pollinated only by these insects.
* Working with the textbook
Look at Figure No. 98 B “Structure of the limbs of various insects.”
There are three pairs of legs on the chest. Find in the text of the paragraph what types of legs different insects have. The cockroach and most insects have running legs. The grasshopper, locust, and flea have a very long and powerful back pair of legs. These are jumping legs. In the swimming beetle and the smooth water bug, the back pair of legs are covered with long hairs that form a wide surface - a kind of paddle. These are swimming legs. The mole cricket's front pair of legs is powerful, flat and short. These are digging legs. The praying mantis has legs of the grasping type, covered with rows of spines; they are able to grab the victim, closing like scissors.
The tarsus end with claws, which insects use to cling to uneven surfaces when walking and running. The claws allow you to climb vertical surfaces and even the undersides of leaves and the ceilings of rooms. Some insects have suckers between their claws, which they use when moving on a smooth surface, such as glass. The main types of legs come down to options: the front legs can be digging or grasping, the hind legs can be jumping or swimming.
* Performance by 3 students:
Insects have wings on their chests - perfect flight organs. Among invertebrate animals, only insects have wings, which gave them a great advantage in competition with other organisms. Wings function only in adult insects. With the help of flight, they spread over considerable distances, including short time find an individual of the opposite sex or favorable conditions for the development of offspring. The flight speed of hawk moth butterflies is especially high - 15 m/s, and the distances these butterflies are capable of flying are measured in hundreds of kilometers. With the help of their wings, locusts migrate, covering 4000 km.
The names of insect orders are given mainly by the structure of their wings: “Coleoptera”, “Lepidoptera”, “Hymenoptera”, “Diptera”.
* Speech by 4 students:
The abdomen of insects is usually soft and consists of 8–11 segments. It serves mainly to accommodate internal organs, mainly the digestive system and reproductive organs, and reserve nutrients in the form of a fat body. The abdomen is attached to the thoracic region either motionlessly, like in beetles, or vice versa, with the help of a thin stalk, like in many Hymenoptera - ants, wasps, bees, in which the mobility of the abdomen is preserved, which is of utmost importance. On the sides of the abdomen there are small openings called spiracles. At the end of the abdomen there is an anus. Females may develop a long ovipositor, sometimes turning into a sting.
4) Fizminutka
5) Consolidation
* Laboratory work No. 5 “The external structure of an insect.”
Find a description of the work progress in the paragraph, read and complete it yourself.
Fill out the table “External structure of an insect” in your laboratory notebooks.
6) Summing up the lesson
What did you learn about in class today?
What new things have you learned about yourself?
What is the reason for the wide variety of insect species?
7) Homework
paragraph No. 26, question No. 3,4, prepare for the presentation competition “The World of Insects”.
Class Insects. General characteristics, internal and external structure, structure of a simple eye and a complex compound eye, reproduction, diversity and importance of Insects
Class Insects (Insecta). Structural features, digestion, respiratory and excretory systems, sensory organs and representatives
The cuticle of insects is covered with a thin layer of fat-like substance that prevents the body from losing moisture. On the surface of the cuticle there are movable hairs, scales, and bristles.
The body consists of a head, chest and abdomen. On the head there are a pair of segmented antennae, oral organs (a pair of upper jaws, a pair of lower jaws, a lower lip), a pair of complex compound eyes, and maybe 1 - 3 simple ocelli. The area between the compound eyes is called forehead . On the sides under the eyes there are cheeks . The back surface of the head is called the back of my head . The head and thoracic region are movably connected.
The chest consists of three segments. They have 3 pairs of limbs that extend from each thoracic segment and are movably attached. The types of limbs depend on the lifestyle: walking, running (in beetles), hock (in grasshoppers), digging (in mole crickets), swimming (in the diving beetle). On the last segment of the legs there are claws, and in some species there are also suckers.
Many insects (adults only) have wings (a fold of skin filled with hemolymph) that are attached to the second or second and third segments of the thorax. The wings have developed transverse and longitudinal veins that form a supporting frame. The trachea and nerves pass through the middle of the veins. The shape and structure of the wings are varied. In many species, the first pair of wings is transformed into hard elytra that protect the rear membranous, often transparent wings from damage. In the order Diptera only the first pair of wings is developed. The second is modified into club-shaped appendages, which provide a certain frequency of wing beats, stabilize the balance of the insect in flight and are called halteres . There are two known types of flight in insects: flapping and soaring. Flight is ensured by the coordinated work of the pectoral and wing muscles. By quickly working their wings, some insects are able to hover in the air (flies, dragonflies, etc.).
The abdomen consists of several segments (4 – 10) and an anal plate. It houses most of the internal organs. Each segment has a pair of spiracles. There are no limbs. In some species they are modified into an ovipositor, sting, etc. The paired appendages of the last abdominal segment are called churches.
Digestive system of insects
Class Insects (Insecta). Types of mouthparts: gnawing type (grasshopper), sucking type (butterfly) and licking type (fly)
Gnawing mouthparts is considered the most ancient (characteristic of primitive insects) and is common among insects that feed on solid plant or animal food (beetles, cockroaches, orthoptera, etc.). On top, the oral opening of such an apparatus is covered by an unpaired plate (upper lip), on the sides there are paired upper and lower jaws, and on the bottom – an unpaired lower lip. The upper lip is formed by a fold of the cuticle. The upper jaws are represented by plates with teeth on the inside. The lower jaws consist of two segments. On the upper segment there is a pair of ruminant lobes and a mandibular dissected palp (the organ of touch and taste). The lower lip was formed by the fusion of the lower jaws, consists of two segments and has a pair of lower labial palps and two pairs of ruminant lobes.
piercing-sucking the apparatus is typical for insects (bugs, mosquitoes, etc.) that feed on liquid food: plant juice, tissue, animal blood.
Sucking mouthparts in the form of a long tube of two halves, it is found in butterflies that feed on the juice of fruits and the nectar of flowers. Flies have a peculiar oral apparatus with a fleshy lower lip - licking (modified sucking).
Gnawing-licking mouthparts found in Hymenoptera (bees, wasps, etc.). These are mouthparts that have extended into a proboscis to suck up nectar. At the same time, the upper jaws remained almost unchanged (reduced ruminant teeth) and are used for the structure of cells. Sometimes adult insects do not feed (mulberry moths), their oral organs do not function and may be reduced.
Digestive system consists of the oral cavity, pharynx, esophagus, large crop, muscular stomach (in insects that feed on solid food, the walls are thick with chitinous teeth or plates for grinding food), midgut, hindgut, which ends in the anus.
The ducts of the salivary glands open into the oral cavity. Their secretion moistens and partially dissolves solid food. In bees, the secretion of the salivary glands turns into honey when mixed with nectar. In the caterpillars of butterflies, hymenoptera larvae and some other insects, the salivary glands are modified into silk-secreting or spinning glands. Silk thread is used to build a cocoon, protective formations, etc.
Worker bees feed the larvae of the future queen with the secretion of the pharyngeal glands.
The inside of the midgut is lined with glandular epithelium, which secretes digestive juice. Insects do not have a liver. Some insects, like spiders, are capable of extraintestinal digestion (ladybug larvae, diving beetles, etc.).
Excretory system of insects
The organs of excretion are the Malpighian vessels (blindly closed tubes that protrude into digestive system between the middle and hind intestines), the fat body (has a whitish, yellowish or greenish color and, in addition to the excretory buds - storage buds, performs a storage function).
Circulatory system of insects
The circulatory system is not closed. The heart is tubular, multi-chambered, located on the dorsal side of the abdomen. A pair of holes with valves opens into each chamber. Several chambers are capable of pulsation. One leaves the heart ahead blood vessel– aorta. Blood from the heart enters the aorta, from it into the head cavity, and then into the spaces between the organs. Blood (hemolymph) is colorless, greenish-yellow, sometimes red, and does not participate in the transport of gases.
Respiratory system of insects
They breathe using the trachea. They branch and entwine all organs, even entering individual cells in the form of tracheoles. 10 pairs of spiracles open outward or stigma - holes on the sides of the abdomen and chest. In the anterior part of the abdomen and chest, the trachea expands and forms air sacs. Gas exchange occurs through the trachea (oxygen is absorbed, carbon dioxide is removed), and water vapor is removed. Breathing occurs due to the rhythmic contraction and stretching of the lateral and longitudinal muscles of the abdomen. The larvae of some insects breathe using tracheal gills (dragonflies, day-olds). These are formations on the surface of the body or in the hindgut, which have the appearance of petals with branched trachea in the middle. The tracheal system is closed (there are no spiracles). Oxygen enters the trachea from the gills.
Nervous system of insects
It consists of the subpharyngeal (formed by the fusion of three ganglia) and suprapharyngeal ganglia, connected by peripharyngeal connectives, and the ventral nerve chain. The subpharyngeal node innervates the oral organs and the anterior intestine. The ventral chain is formed by three thoracic ganglia and eight abdominal ones. In some highly organized insects, adjacent nodes of the ventral nerve chain merge by combining the thoracic ganglia into one large node. The abdominal nodes can merge into 2 - 3 or 1 large node (in flies, lamellar beetles). The thoracic ganglia regulate the functioning of the legs and wings.
The suprapharyngeal ganglion forms a special development. It forms the brain, which includes three sections: anterior, middle and posterior. Innervates the antennae and eyes (it has a pair of large optic lobes on the sides). In the anterior section there are very well developed pairs stalked or mushroom-shaped , tel. They are believed to be responsible for the behavior of insects.
The complex structure of the nervous system causes complex behavior.
Sense Organs of Insects
On the head there is 1 pair of antennae (organs of smell and touch). Various structure of the antennae: comb-shaped, club-shaped, filamentous, lamellar, bristle-shaped, serrated, etc. The organ of vision is complex (compounded) eyes, sometimes there are simple ones (1 – 3). Each compound eye is made up of large quantity facets (several thousand). Most insects do not perceive red color, but they perceive ultraviolet radiation well. Simple eyes (not capable of perceiving images) react to the degree of illumination and can perceive polarized light. Insect larvae with complete metamorphosis have lateral eyes (from one to several pairs). Each such eye can perceive images of objects. The body and limbs are covered with hairs and scales, which are receptors for taste, touch, etc. Some insects have a hearing organ (in grasshoppers - on the front pair of legs, etc.).
Insect Reproduction
Types of insect development. Complete transformation (development with metamorphosis) and incomplete transformation (development without metamorphosis)
They reproduce only sexually (with or without fertilization). Reproductive organs are developed only in adult insects (imago). Insects are dioecious. In many species, sexual dimorphism is well expressed (beetle - deer, butterflies, etc.). The genital organs are located in the abdomen. In females they are represented by tubular ovaries, oviducts, accessory gonads, and spermatic receptacle. At the end of the abdomen, females have an ovipositor for laying eggs. In some insects of the order Hymenoptera, it is turned into a sting with a duct of a poisonous gland inside.
In males reproductive system represented by a pair of testes, vas deferens, vas deferens, and accessory reproductive organs. At the end of the abdomen the copulatory apparatus may be developed. Fertilization is predominantly internal.
There is only one genital opening, since the ducts of the gonads merge. Some insects are characterized by mating behavior (competition for a female, etc.).
Most insects lay eggs, sometimes they are viviparous (they give birth to live larvae - aphids, gadflies, etc.). Eggs are covered with a thick shell and contain a supply of nutrients (yolk) inside. They are laid by females singly or in groups on different surfaces, in soil, water or in animals, etc. The insects are very prolific (bees lay up to 1.5 million eggs every day for 10 - 12 years; termite queen - over 30 thousand eggs) . They can have several generations per year (depending on the species and living conditions).
Development with transformation (complete and incomplete). Stages incomplete transformations : egg – larva – adult insect (imago) . Characteristic of cockroaches, bedbugs, lice, orthoptera, etc. Insect larvae with incomplete metamorphosis are similar in appearance to an adult insect, but are smaller in size (after each molt they become more and more similar to an adult), primarily live where adults live, and feed on the same food. food. Sometimes the larvae live in a different environment (dragonflies, etc.), then they have certain adaptations and differ somewhat from adult insects.
Stages complete transformation : egg – larva – pupa – adult insect (imago). Characteristic of Lepidoptera, Hardiptera, Hymenoptera, Diptera, etc. The larva does not appearance, nor is its lifestyle similar to that of an adult insect. The larvae of such insects never have compound eyes, the limbs are mostly absent or underdeveloped, the mouthparts differ from those of adults, and they feed on different foods (which reduces competition with adults). The larvae of some species may have special larval organs (silk-secreting glands of a caterpillar, etc.). The pupa is motionless and does not feed. In it, the larval tissues are completely destroyed and new ones, characteristic of an adult insect, are formed. Only the nervous system, the rudiments of the gonads and special structures are not destroyed - imaginal discs , due to which the organs of an adult insect are formed.
The development of some insects can be very short, and in individual species last for several years (chafer bug, etc.).
The insect class is divided into approximately 30 orders.
Insect Orders
Types of insect development. Development of insects with incomplete transformation: egg - larva - adult insect (imago). Development of insects with complete transformation: egg - larva - pupa - adult insect (imago)
- Order Orthoptera (Orthoptera). Representatives: green, gray grasshoppers, locusts, mole cricket and others.
- Squad Cockroaches (Blattoptera). Representatives: black beetle, red cockroach or Prussian, Madagascar hissing cockroach, American cockroach and others.
- Squad Termites (Isoptera). Representatives: Mediterranean termite or harmful and etc.
- Troop Lice (Anoplura). Representatives: head louse, cootie and etc.
- Order Hemiptera or Bugs (Hemiptera). Representatives: turtle bugs, pine subcortical bug and etc.
- Order Homoptera (Homoptera). Representatives: mountain cicada and etc.
- Dragonfly Squad (Odonata). Representatives: dragonflies, beautiful dragonflies and etc.
- Order Beetles or Hardwings (Coleoptera). Representatives: ladybug, ground beetle, Chafer, Colorado beetle, stag beetle, swimming beetle and etc.
- Order Lepidoptera or Butterflies (Lepidoptera). Representatives: swallowtail, cabbage butterfly, silkworm and etc.
- Order Hymenoptera (Hymenoptera). Representatives: bee, wasp, bumblebee, ant and etc.
- Order Diptera (Diptera). TO long-whiskered dipteran relate mosquitoes, midges, mosquitoes etc. K short-whiskered dipteran – flies, gadflies and etc.
- Order Fleas (Aphaniptera). Representatives: human flea, rat flea and etc.
Meaning of Insects
The diversity and importance of insects
They are an important link in natural biocenoses. They surpass all other animals in biomass.
Class Insects. Pests of grain crops: Bread beetle, Cereal fly, Ground beetle, Thrips and Cereal aphid
Honey, royal jelly, bee venom, and glue are obtained from the honey bee. Widely used in industry (metallurgy, chemical production, electrical engineering) wax. Silk is obtained from the silkworm.
Many types of insects are pests of agricultural and forest crops. Dangerous pests of cultivated plants include about 300 species (chafer beetle, mole cricket, beet weevil, ringed silkworm, gypsy moth, fall armyworm, cabbage cutworm, pea weevil, Colorado potato beetle, etc.). About 200 species of insects damage human food supplies (peas and beans - grain beetles, flour - mill moth caterpillar, grain - grain moth, some weevils, etc.). Wooden products, buildings, and plants are damaged by termites. Fur, wool - house moths, leather - carpet beetles.
Explanation.
1. The ability to fly, allowing insects to quickly colonize new territories, overcome water spaces and other obstacles; greater mobility, ensured by developed striated muscles and jointed limbs.
2. Multilayer chitinized cuticle with an outer layer containing wax-like and fatty substances, protecting the body from moisture loss, mechanical damage, and exposure to ultraviolet rays.
3. A variety of mouthparts, allowing the use of various food materials, which reduces interspecific competition and helps maintain a high number of insects.
4. The small size of insects ensures survival and contributes to the creation necessary conditions for existence even in very small spaces (small fouling on rocks, cracks in tree bark, soil, etc.).
6. High fertility and ability for mass reproduction: the average number of eggs laid is 200−300. Some insects lay a small number of eggs, but produce several generations (up to 10 or more) during the growing season. This ability causes the massive appearance of many insects (beetles, flies, mosquitoes, locusts, etc.).
7. A variety of types of postembryonic development: incomplete, complete metamorphosis and other types of transformation. In the larval phase, the growth and development of the individual occurs, in the adult phase, reproduction and settlement occur. The ability to experience unfavourable conditions in a state of diapause - temporary physiological rest.
8. Change of habitat at different stages of ontogenesis: larvae live in the aquatic environment, adults live in the ground-air environment (for example, dragonflies, mosquitoes, etc.), which reduces intraspecific competition for food, living space and promotes better survival of insects.
9. The respiratory organs - the trachea - allow for intensive gas exchange and, if necessary (during flight), maintain a high level of vital processes.
10. A well-developed nervous system, diverse and perfect sense organs, complex innate forms of individual and social behavior - instincts. Features of the structure and life processes. The body of insects is divided into head, thorax and abdomen. On the head there is a pair of segmented antennae, a pair of upper and two pairs of lower jaws. In addition, they have a pair of compound compound eyes, and many have simple ocelli. The structure of the oral apparatus is varied and corresponds to the nature of nutrition. The initial one is considered to be the gnawing mouthparts, from which, as a result of food specialization, the other types evolved: piercing-sucking (in mosquitoes, bedbugs, aphids, etc.), sucking (in Lepidoptera), lapping (in bees, bumblebees), licking (in flies) . In particular, insects of the orders Coleoptera and Orthoptera, as well as many larvae, have a gnawing mouthpart.
Note.
Any 3-4 positions from those listed above can be counted as an answer.