Body density in annelids. Annelids: general characteristics of the type
TO annelids belong primary annulus, polychaete and oligochaete worms, leeches and echiurids. In the type of annelids, there are about 8 thousand species. These are the most highly organized representatives of the group of worms. The sizes of the rings range from fractions of a millimeter to 2.5 m. Mostly these are free-living forms. The body of the annulus is subdivided into three parts: the head, the trunk, consisting of rings, and the anal lobe. Such a clear division of the body into sections is not found in animals that are lower in their organization.
The head of the rings is equipped with various sense organs. Many ringlets have well developed eyes. Some have particularly sharp eyesight, and their lens is capable of accommodation. True, the eyes can be located not only on the head, but also on the tentacles, on the body and on the tail. The rings also have developed taste sensations. On the head and tentacles, many of them have special olfactory cells and ciliary pits that perceive various smells and the action of many chemical stimuli. The organs of hearing, arranged according to the type of locators, are well developed in the rings. Recently, auditory organs, very similar to those of the lateral line in fish, have been discovered in Echiurid marine rings. With the help of these organs, the animal subtly distinguishes the slightest rustles and sounds, which are heard much better in water than in air.
The body of the rings consists of rings, or segments. The number of rings can reach several hundred. Other rings consist of only a few segments. Each segment to some extent represents an independent unit of the whole organism. Each segment includes parts of vital organ systems.
Special organs of movement are very characteristic of rings. They are located on the sides of each segment and are called parapodia. The word "parapodia" means "feet-like". Parapodia are lobe-shaped outgrowths of the body, from which tufts of bristles stick out. In some pelagic polychaetes, the length of the parapodia is equal to the diameter of the body. Parapodia are not developed in all annulus. They are present in primary annulus and polychaete worms. In oligochaetes, only bristles remain. Primitive Leech acanthobdella has bristles. The rest of the leeches do without parapodia and bristles in motion. At echiuride no parapodia, and setae present only at the posterior end of the body.
Parapodia, nodes of the nervous system, excretory organs, sex glands, and, in some polychaetes, paired pockets of the intestine, are systematically repeated in each segment. This internal segmentation coincides with the external annulus. The repeated repetition of body segments is called the Greek word "metamerism". Metamerism arose in the process of evolution in connection with the elongation of the body of the ancestors of the annulus. The elongation of the body necessitated multiple repetition first, the organs of movement with their muscles and nervous system, and then the internal organs.
The segmented secondary cavity of the body, or the whole, is extremely characteristic of the rings. This cavity is located between the intestines and the body wall. The body cavity is lined with a continuous layer of epithelial cells, or coelothelium. These cells form a layer that covers the intestines, muscles, and all other internal organs. The body cavity is divided into segments by transverse partitions - dissipations. A longitudinal septum passes along the midline of the body - the mesentery, which divides each compartment of the cavity into the right and left parts.
The body cavity is filled with fluid, which in its own way chemical composition very close to sea water. The fluid filling the body cavity is in continuous motion. The body cavity and cavity fluid perform important functions. The cavity fluid (like any fluid in general) does not compress and therefore serves as a good "hydraulic skeleton". The movement of the cavity fluid can transport various nutritious products, secretions of the endocrine glands, as well as oxygen and carbon dioxide involved in the breathing process inside the body of the rings.
Internal partitions protect the body in case of severe injuries and ruptures of the body wall. For example, an earthworm cut in half does not die. The partitions prevent the cavity fluid from flowing out of the body. The internal partitions of the rings thus protect them from death. Marine ships and submarines also have internal hermetic partitions. If the board is pierced, then the water that rushes into the hole fills only one damaged compartment. The remaining compartments, not filled with water, retain the buoyancy of the damaged ship. Similarly, in annuli, a violation of one segment of their body does not entail the death of the entire animal. But not all annelids have well-developed septa in the body cavity. For example, in Echiurids, the body cavity does not have partitions. A puncture of the body wall of an echiurida can lead to its death. In addition to the respiratory and protective role, the secondary cavity acts as a receptacle for the reproductive products that mature there before being brought out.
ringlets, with few exceptions, have a circulatory system. However, they have no heart. The walls of large vessels themselves contract and push blood through the thinnest capillaries. In leeches, the functions of the circulatory system and the secondary cavity coincide so much that these two systems are combined into a single network of lacunae through which blood flows. In some rings, the blood is colorless, in others it is colored green by a pigment called chlorcruorin. Often the rings have red blood, similar in composition to the blood of vertebrates. Red blood contains iron, which is part of the hemoglobin pigment. Some rings, burrowing into the ground, experience an acute oxygen deficiency. Therefore, their blood is adapted to bind oxygen especially intensively. For example, the polychaete Magelona papillicornis has developed the pigment hemerythrin, which contains five times more iron than hemoglobin.
In annuli, compared with lower invertebrates, metabolism and respiration proceed much more intensively. Some polychaete rings develop special respiratory organs - gills. In the gills, a network of blood vessels branches, and through their wall oxygen penetrates into the blood, and then spreads throughout the body. Gills can be located on the head, on the parapodia and on the tail.
The end-to-end intestine of the annulus consists of several sections. Each section of the intestine has its own specific function. The mouth leads to the throat. Some ringlets have strong horny jaws and denticles in the throat, which help to grasp live prey more firmly. In many predatory rings, the throat serves as a powerful weapon of attack and defense. The esophagus follows the pharynx. This department is often supplied with a muscular wall. Peristaltic movements of the muscles slowly push the food into the following sections. In the wall of the esophagus there are glands, the enzyme of which serves for the primary processing of food. The esophagus is followed by the midgut. In some cases, goiter and stomach are developed. The wall of the midgut is formed by an epithelium very rich in glandular cells that produce a digestive enzyme. Other cells in the midgut absorb the digested food. In some rings, the midgut is in the form of a straight tube, in others it is curved in loops, and still others have metameric outgrowths from the sides of the intestine. The hindgut ends with an anus.
Special organs - metanephridia - serve to excrete liquid metabolic products. Often they serve to bring out the germ cells - sperm and eggs. Metanephridia begin as a funnel in the body cavity; a convoluted canal runs from the funnel, which opens outward in the next segment. Each segment contains two metanephridia.
Ringworms reproduce asexually and sexually. Aquatic rings frequently reproduce asexually. At the same time, their long body breaks up into several parts. After a while, each part regenerates its head and tail. Sometimes a head with eyes, tentacles, and a brain forms in the middle of the worm's body before it splits apart. In this case, the detached parts already have a head with all the necessary sense organs. Polychaetes and oligochaetes are relatively good at restoring lost body parts. Leeches and echiurids do not have this ability. These rings have lost their segmented body cavity. This is partly why, apparently, they do not have the ability to reproduce asexually and restore lost parts.
Fertilization of eggs in sea rings occurs most often outside the body of the mother's organism. In this case, males and females simultaneously release germ cells into the water, where fertilization occurs.
In marine polychaetes and echiurids, the crushing of fertilized eggs leads to the development of a larva that does not at all resemble adult animals and is called a trochophore. Trochophora lives for a short time in the surface layers of water, and then settles to the bottom and gradually turns into an adult organism.
Freshwater and terrestrial rings are most often hermaphrodites and have direct development. There are no free larvae in freshwater and terrestrial rings. This is due to the fact that fresh water has a salt composition of a completely different property than sea water. Sea water is more favorable for the development of life. Fresh water even contains some poisonous waters (for example, magnesium) and is less suitable for the development of organisms. Therefore, the development of freshwater animals almost always occurs under the cover of special, low-permeability shells. Even more dense shells - shells - are formed in eggs of ground rings. Dense shells here protect the eggs from mechanical damage and from drying out under the scorching rays of the sun.
The practical importance of annelids is growing more and more in connection with the development of the intensity of biological research.
In the USSR, for the first time in the history of world science, acclimatization of some invertebrates has been carried out to strengthen the food supply of the sea. For example, the Nereis polychaete, acclimatized in the Caspian Sea, has become the most important food item for sturgeon and other fish.
Earthworms not only serve as bait for fishing and food for birds. They bring great benefits to man, loosening the soil, making it more porous. This favors the free penetration of air and water to the roots of plants and increases crop yields. Rummaging in the ground, the worms swallow pieces of soil, crush them and throw them to the surface well mixed with organic matter. The amount of soil brought to the surface by worms is amazingly large. If we were to distribute the soil plowed by earthworms every 10 years over the entire surface of the land, we would get a layer of fertile earth 5 cm thick.
Leeches are used in medical practice for hypertensive diseases and the risk of hemorrhage. They let the substance hirudin into the blood, which prevents blood clotting and promotes the expansion of blood vessels.
ring type includes several classes. The most primitive are marine primary rings - archiannelides. Polychaete rings and echiurids- inhabitants of the sea. Small-bristle rings and leeches- mainly inhabitants of fresh water and soil.
Animal life: in 6 volumes. - M.: Enlightenment. Edited by professors N.A. Gladkov, A.V. Mikheev. 1970 .
The type of annelids, uniting about 12,000 species, is, as it were, a node of the genealogical tree of the animal world. According to existing theories, annelids originate from ancient ciliary worms (turbellar theory) or from forms close to ctenophores (trochophore theory). In turn, arthropods arose from annelids in the process of progressive evolution. Finally, in their origin, annelids are connected by a common ancestor with molluscs. All this shows the great importance that the type under consideration has for understanding the phylogeny of the animal world. Medically, annelides are of limited value. Only leeches are of some interest.
General characteristics of the type
The body of annelids consists of a head lobe, a segmented body, and a posterior lobe. Segments of the trunk throughout almost the entire body have external appendages similar to each other and a similar internal structure. Thus, the organization of annelids is characterized by structural repeatability, or metamerism.
On the sides of the body, each segment usually has external appendages in the form of muscular outgrowths equipped with bristles - parapodia - or in the form of setae. These appendages are important in the movement of the worm. Parapodia in the process of phylogenesis gave rise to the limbs of arthropods. At the head end of the body there are special appendages - tentacles and palygs.
A skin-muscular sac is developed, which consists of a cuticle, one layer of skin cells underlying it and several layers of muscles (see Table 1) and a secondary body cavity, or coelom, in which internal organs are located. The whole is lined with peritoneal epithelium and divided by septa into separate chambers. At the same time, each segment of the body has a pair of coelomic sacs (only the head and posterior lobes are devoid of the coelom).
The coelomic sacs in each segment are placed between the intestine and the body wall and are filled with a watery fluid in which the amoeboid cells float.
In general, it performs a supporting function. In addition, coelomic fluid from the intestine receives nutrients which are then distributed throughout the body. In general, they accumulate harmful products metabolism, which are removed by the excretory organs. Male and female gonads develop in the walls of the coelom.
Central nervous system represented by the supraesophageal ganglion and the ventral nerve cord. Nerves from the sense organs pass to the supraglottic node: eyes, balance organs, tentacles and palps. The abdominal nerve cord consists of nodes (one pair in each segment of the body) and trunks that connect the nodes to each other. Each node innervates all the organs of this segment.
The digestive system consists of the anterior, middle and hindgut. The foregut is usually divided into a number of sections: the pharynx, esophagus, crop and gizzard. The mouth is on the ventral side of the first body segment. The hindgut opens with an anus on the posterior lobe. In the wall of the intestine there is a musculature that ensures the movement of food.
The organs of excretion - metanephridia - are paired tubular organs, metamerically repeated in body segments. Unlike protonephridia, they have a through excretory canal. The latter begins with a funnel that opens into the body cavity. The cavity fluid enters the nephridium through the funnel. A tubule of nephridium departs from the funnel, sometimes opening outwards. Passing through the tubule, the liquid changes its composition; it concentrates the end products of dissimilation, which are ejected from the body through the outer pore of the nephridium.
In annelids, for the first time in the phylogenesis of the animal world, a circulatory system. The main blood vessels run along the dorsal and ventral sides. In the anterior segments they are connected by transverse vessels. The dorsal and anterior annular vessels are able to contract rhythmically and perform the function of the heart. In most species, the circulatory system is closed: blood circulates through a system of vessels, nowhere interrupted by cavities, lacunae or sinuses. In some species, the blood is colorless, in others it is red due to the presence of hemoglobin.
Most species of annelids breathe through skin rich in blood capillaries. A number of marine forms have specialized respiratory organs - gills. They usually develop on the parapodia or on the palps. Vessels carrying venous blood approach the gills; it is saturated with oxygen and enters the body of the worm in the form of arterial blood. Among annelids there are dioecious and hermaphroditic species. The sex glands are located in the body cavity.
Annelids have the highest organization in comparison with other types of worms (see Table 1); for the first time they have a secondary body cavity, a circulatory system, respiratory organs, and a more highly organized nervous system.
| Table 1. Characteristic features of various types of worms | ||||||
| Type | Skin-muscular sac | Digestive system | Circulatory system | reproductive system | Nervous system | body cavity |
| flatworms | Includes layers of longitudinal and circular muscles, as well as bundles of dorso-abdominal and diagonal muscles | From the ectodermal foregut and endodermal midgut | not developed | hermaphroditic | Paired brain ganglion and several pairs of nerve trunks | Absent, filled with parenchyma |
| roundworms | Only longitudinal muscles | From the ectodermal foregut and hindgut and endodermal midgut | Same | Dioecious | Periopharyngeal nerve ring and 6 longitudinal trunks | Primary |
| From external circular and internal longitudinal muscles | From the ectodermal foregut and hindgut and endodermal midgut | Well developed, closed | Dioecious or hermaphrodites | Paired brain ganglion, peripharyngeal nerve ring, ventral nerve cord | Secondary | |
|
Animals belonging to the type of annelids, or annelids, are characterized by:
Ringed worms live in fresh and sea waters, as well as in the soil. Several species live in the air. The main classes of the type of annelids are:
Class polychaetal ringsFrom the point of view of the phylogenesis of the animal world, polychaetes are the most important group of annelids, since the emergence of higher groups of invertebrates is associated with their progressive development. The body of polychaetes is segmented. There are parapodia, consisting of dorsal and ventral branches, each of which bears a tendril. The muscular wall of the parapodia has thick supporting setae, and tufts of thin setae protrude from the apex of both branches. The function of the parapodia is different. Usually these are locomotor organs involved in the movement of the worm. Sometimes the dorsal barnacle grows and turns into a gill. The circulatory system of polychaetes is well developed and always closed. There are species with cutaneous and gill respiration. Polychaetes are dioecious worms. They live in the seas, mainly in the coastal zone. Nereid (Nereis pelagica) can serve as a characteristic representative of the class. It is found in abundance in the seas of our country; leads a bottom way of life, being a predator, captures prey with its jaws. Another representative - sandworm (Arenicola marina) - lives in the seas, digs holes. It feeds by passing sea silt through its digestive tract. Breathe with gills. Class low-bristle ringsThe oligochaetes are descended from polychaetes. The external appendages of the body are setae, which sit directly in the wall of the body; no parapodia. The circulatory system is closed; skin breathing. Small-bristle rings are hermaphrodites. The vast majority of species are inhabitants of fresh water and soil. An earthworm (Lumbricus terrestris) can serve as a characteristic representative of the class. Earthworms live in the soil; during the day they sit in holes, and in the evening they often crawl out. Rummaging in the soil, they pass it through their intestines and feed on the plant residues contained in it. Earthworms play an important role in soil-forming processes; they loosen the soil and contribute to its aeration; leaves are dragged into holes, enriching the soil with organic substances; they extract deep layers of soil to the surface, and superficial ones carry them deeper. The structure and reproduction of the earthworm The earthworm has an almost round body in cross section, up to 30 cm long; have 100-180 segments or segments. In the front third of the body of the earthworm there is a thickening - a girdle (its cells function during the period of sexual reproduction and oviposition). On the sides of each segment, two pairs of short elastic bristles are developed, which help the animal when moving in the soil. The body is reddish-brown in color, lighter on the flat ventral side and darker on the convex dorsal side. A characteristic feature of the internal structure is that earthworms have developed real tissues. Outside, the body is covered with a layer of ectoderm, the cells of which form the integumentary tissue. The skin epithelium is rich in mucous glandular cells. Under the skin there is a well-developed musculature, consisting of a layer of annular and a more powerful layer of longitudinal muscles located under it. With the contraction of the circular muscles, the body of the animal is stretched and becomes thinner; with the contraction of the longitudinal muscles, it thickens and pushes the soil particles apart.
The digestive system begins at the front end of the body with a mouth opening, from which food enters sequentially into the pharynx, esophagus (in earthworms, three pairs of calcareous glands flow into it, the lime coming from them into the esophagus serves to neutralize the acids of rotting leaves that animals feed on). Then the food passes into an enlarged goiter, and a small muscular stomach (the muscles in its walls contribute to the grinding of food). From the stomach almost to the rear end of the body stretches the middle intestine, in which, under the action of enzymes, food is digested and absorbed. Undigested residues enter the short hindgut and are thrown out through the anus. Earthworms feed on half-decayed plant remains, which they swallow along with the earth. When passing through the intestines, the soil mixes well with organic matter. Earthworm excrement contains five times more nitrogen, seven times more phosphorus and eleven times more potassium than ordinary soil. The circulatory system is closed and consists of blood vessels. The dorsal vessel stretches along the entire body above the intestines, and under it - the abdominal one. In each segment, they are united by an annular vessel. In the anterior segments, some annular vessels are thickened, their walls contract and pulsate rhythmically, due to which blood is distilled from the dorsal vessel to the abdominal one. The red color of blood is due to the presence of hemoglobin in the plasma. For most annelids, including earthworms, skin respiration is characteristic, almost all gas exchange is provided by the body surface, therefore earthworms are very sensitive to soil moisture and are not found in dry sandy soils, where their skin dries out soon, and after rains, when in soil a lot of water, crawl to the surface. The excretory system is represented by metanephridia. Metanephridium begins in the body cavity with a funnel (nephrostome) from which a duct extends - a thin loop-shaped curved tube that opens outward as an excretory pore in the side wall of the body. Each segment of the worm has a pair of metanephridia - right and left. The funnel and duct are equipped with cilia that cause the movement of excretory fluid. The nervous system has a structure typical of annelids (see Table 1), two ventral nerve trunks, their nodes are interconnected and form an ventral nerve chain. The sense organs are very poorly developed. The earthworm does not have real organs of vision, their role is performed by individual light-sensitive cells located in the skin. The receptors for touch, taste, and smell are also located there. Like hydra, earthworms are capable of regeneration. Reproduction occurs only sexually. Earthworms are hermaphrodites. In front of their body are the testes and ovaries. Fertilization of earthworms is cross. During copulation and oviposition, the cells of the girdle on the 32-37th segment secrete mucus, which serves to form the egg cocoon, and a protein liquid to nourish the developing embryo. The secretions of the girdle form a kind of mucous sleeve. The worm crawls out of it with its rear end forward, laying eggs in the mucus. The edges of the muff stick together and a cocoon is formed, which remains in the earthen burrow. Embryonic development of eggs occurs in a cocoon, young worms emerge from it. The passages of earthworms are mainly in the surface layer of the soil to a depth of 1 m, for the winter they descend to a depth of 2 m. Through the minks and passages of earthworms, atmospheric air and water penetrate the soil, which are necessary for the roots of plants and the vital activity of soil microorganisms. Through its intestines, the worm passes as much soil per day as its body weighs (an average of 4-5 g). On each hectare of land, earthworms process an average of 0.25 tons of soil daily, and annually they throw out from 10 to 30 tons of soil processed by them to the surface in the form of excrement. In Japan, specially bred breeds of fast-reproducing earthworms are bred and their excrement is used for the biological method of tillage. Vegetables and fruits grown on such soil have an increased sugar content. Charles Darwin was the first to point out the important role of earthworms in soil formation processes. Annelids play a significant role in the nutrition of bottom fish, since in some places worms make up to 50-60% of the biomass of the bottom layers of water bodies. In 1939-1940. The nereis worm was moved from the Sea of Azov to the Caspian Sea, which now forms the basis of the diet of sturgeons in the Caspian Sea.
Leech classThe body is segmented. In addition to true metamerism, there is false ringing - several rings in one segment. Parapodia and setae absent. The secondary body cavity was reduced; instead, there are sinuses and gaps between the organs. The circulatory system is not closed; blood only part of its path passes through the vessels and pours out of them into the sinuses and lacunae. There are no respiratory organs. The reproductive system is hermaphrodite. Medical leeches are specially bred and then sent to hospitals. They are used, for example, in the treatment of eye diseases associated with an increase in intraocular pressure (glaucoma), with cerebral hemorrhage and hypertension. With thrombosis and thrombophlebitis, hirudin reduces blood clotting and promotes the dissolution of blood clots. |
Type Annelids (Annelida)
Let's get acquainted with a very interesting group of animals, the structure and behavior of which did not leave even Charles Darwin indifferent. He devoted a lot of time to the study of annelids and wrote several scientific papers about them.
Among the worms, it is the annelids that are considered the most progressive group. This conclusion is made primarily on the basis of the structure of animals.
Type Annelids includes deuterated animals, the body of which consists of repeating segments, or rings. Annelids have closed circulatory system .
Secondary body cavity , or in general (from Greek. koiloma- "deepening", "cavity"), develops in the embryo from the mesoderm layer. This is the space between the body wall and internal organs. Unlike the primary body cavity, the secondary is lined with its own internal epithelium. The secondary cavity of the body is filled with fluid, which creates a constancy of the internal environment of the body. This fluid is involved in metabolism and ensures the activity of the digestive, circulatory, excretory and other organ systems.
Annelids have a segmented body structure, that is, their body is divided into successive segments -segments , or rings (hence the name - annelids). Such segments in individuals different types maybe a few or hundreds. The body cavity is divided into segments by transverse partitions.
Each segment is to some extent an independent compartment, because it contains nodes of the nervous system, excretory organs ( paired nephridia) and sex glands. Each segment may have lateral outgrowths with primitive limbs - parapodia armed with setae.
The secondary cavity of the body, or the whole, is filled with fluid, the pressure of which maintains the shape of the body of the worm and serves as a support during movement, that is, it serves as a wholehydroskeleton . The coelomic fluid carries nutrients, accumulates and removes substances harmful to the body, and also removes reproductive products.
Musculature consists of several layers of longitudinal and circular muscles. Breathing is done through the skin. The nervous system consists of the "brain", formed by paired ganglia, and the ventral nerve chain.
The closed circulatory system consists of the abdominal and dorsal vessels connected in each segment by small annular vessels. Several of the thickest vessels in the anterior part of the body have thick muscular walls and act as "hearts". In each segment, the blood vessels branch, forming a dense capillary network.
Some annelids are hermaphrodites, while others have different males and females. Development is direct or with metamorphosis. Asexual reproduction (budding) also occurs.
Their sizes range from a few millimeters to 3 m. In total, there are 7,000 species of annelids.
Interactive lesson simulator (Go through all the pages of the lesson and complete all the tasks)
Ringed worms - progressive a group of worms. Their body is made up of many ring segments. By The cavity of the body is divided by internal fences according to the number segments. Ringed worms have various organ systems. They have the circulatory system appears paired organs of movement - the prototype of future limbs .
1. Continue filling in the pivot table on p. 13
2. Argue the statement: "Among the various worms, annelids are the most highly organized"
Annelids for the first time have a secondary body cavity and a cellular structure of the skin. The circulatory system appears in the internal structure. The excretory system is represented by more developed metanephridia. Most of the rings are free-living, some have a semblance of legs - parapodia. All are bilaterally symmetrical. Have sense organs
3. Prove that the partitions in the body of an annelids perform a protective function
Each segment of annelids is separated by a septum and has a complete set of nerve nodes, nephridia, annular vessels and gonads. If the integrity of one segment is violated, this affects the vital activity of the worm to a small extent.
4. List structural features that help rings move well in various habitats
Some types of rings have parapodia and setae for locomotion. Those species that do not have parapodia have bristles or their body is covered with mucus for better gliding. The muscular system of all rings is represented by annular and longitudinal muscles
5. After studying the text of the paragraph, complete the diagrams
a) Digestive system of the rings
b) Nervous system of rings
c) Sense organs of rings
6. What happens if the body of the ring is divided into several parts?
Regeneration can occur and the worm will restore the lost parts. That is, asexual reproduction occurs.
7. Is sexual reproduction of rings possible without the formation of a girdle?
Maybe. In some polychaete worms living in the seas and belonging to the type Annelids, reproduction occurs in water, fertilization is external. But in most rings, reproduction occurs with the help of a girdle.
8. How are the number of eggs laid in caring for offspring related?
There is a direct relationship between the number of eggs laid and the care of offspring. Some polychaetes lay few eggs, and the female guards them. This means that the annelids are more advanced than the previous types of worms.
9. Name all possible ways of feeding polychaetes
Among the polychaete worms there are predators that feed on small marine animals. There are omnivores that filter water and feed on plants.
10. Complete the sentences
The development of polychaetes occurs with the alternation of life forms. Their larvae do not look like adults. Each life form performs various functions: reproduction, resettlement, self-preservation. Some polychaetes have care of offspring
11. Finish the scheme
The value of polychaetes in nature
1. Filter water
2. They are fish food
3. They feed on the remains of dead animals
12. What are the differences in the nutrition of polychaete and oligochaete worms?
Small bristle worms feed on organic matter from plant residues of the soil, and among polychaetes there are predators, omnivores, and herbivores.
13. What do protozoa and oligochaetes have in common in adaptations to endure adverse conditions?
To endure unfavorable conditions, many protozoa form a cyst, and oligochaetes form a protective capsule, and fall into diapause. These formations are similar in their functions.
14. Using the text and drawings of the textbook, study the structure of the earthworm, and then do laboratory work No. 3 "The external structure of the earthworm." Make a drawing of an earthworm, marking the anterior and posterior ends of the body, segments, girdle, bristles.
Draw a conclusion about what structural features allow worms to lead an underground lifestyle
Conclusion: The primary cavity of the body is the supporting one. It contains a liquid that gives the body of the worm elasticity.
15. List the characteristic features of leeches:
1) Constant number of body segments
2) The presence of suction cups for attaching to the body of the victim or the substrate
3) Absence of bristles on the body
4) All leeches live in the aquatic environment
16. Name 2 types of food for leeches
17. Look at the pictures. Sign what type and class these worms belong to
18. After studying the text of the paragraph, explain why leeches are more sensitive than other worms to changes in the environment.
Leeches have a better developed nervous system
19. Is the statement true: “It is difficult for oligochaetes to breathe in dirty water, but leeches feel good”?
The statement is not correct. Leeches are very sensitive to the purity of water and die when it is contaminated. Oligochaetes, on the other hand, endure water pollution and can live in such reservoirs for a long time.
20. What happens if leeches stop producing hirudia?
Hirudin is necessary to prevent blood clotting on the wound of the victim and in the stomach of the leech itself. If it is not produced, the leech will not be able to feed, as the blood will clot
21. What is the purpose of buying leeches in a pharmacy?
Leeches are used in medicine to reduce blood pressure in hypertension and the threat of hemorrhage, stroke
22. Specify the characteristics corresponding to each class of annelids
A - 1, 2, 8, 10, 16
B - 4, 6, 11, 12, 17
B - 3, 5, 7, 9, 14, 15
Crossword #1. "Worms"
1. Capsule
3. Polychaetes
4. Cavity
5. Chain
6. Oligochetes
8. Breath
Keyword: rings
Annelids, or annelids (from Latin annulus - ring) - a class of worms with external and internal segmentation. All of them have annular projections, usually corresponding to the internal division of the body. The type has about 18 thousand species.
They belong to primary animals, the body is divided into segments, the number of which in some species reaches several hundred. Let's start studying annelid worms with classification.
The appearance of annelids (annelids) was accompanied by large, significant aromorphoses.
Aromorphoses of annelids
The main details of the structure of annelids will be studied by us using the example of a typical representative - an earthworm (in the oligochaete section).
©Bellevich Yury Sergeevich
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