According to the shape of the body, worms are divided into three types: Flat, Round and Ringed. All worms are three-layer animals. Their tissues and organs develop from three germ layers - ectoderm, endoderm and mesoderm.

Type Flatworms their characteristics

Type Flatworms unites about 12,500 species. In their organization, they are higher than the coelenterates, but among the three-layered animals they are the most primitive. These animals can crawl slowly. Most feature flatworms - a flattened (flattened) body, in the form of a long ribbon.

The figure below shows the structure of the Flatworm using the example of Planaria.

Structure	The body is flattened in the dorsal-abdominal direction, the space between the organs is filled with a special tissue - the parenchyma (there is no body cavity)
body integuments	Skin-muscular sac (skin fused with muscle fibers)
Nervous system	Two nerve trunks connected by nerves ("ladders")
sense organs	Ocelli in front of body, tactile cells scattered throughout body
	The digestive system is blindly closed; have mouth --> pharynx --> branched intestine
	Whole surface of the body
Selection	A system of tubules that open outward on the sides of the body
Reproduction of a flatworm	Hermaphrodites; spermatozoa ripen in the testicles, eggs - in the ovaries; the female lays eggs that hatch into young worms

Variety of Flatworms, their main classes

Type Roundworms and their characteristics

Type Roundworms- a large group of animals with a long, round body in cross section, which is pointed at the front and rear ends. Roundworms are characterized by the presence of free space inside the body - the primary cavity. It contains internal organs surrounded by abdominal fluid. Washing the cells of the body, it is involved in gas exchange and the transfer of substances. The body of roundworms is covered with a strong shell - cuticle. This group includes about 20 thousand species.

The figure below shows the structure of the Roundworm using the example of Ascaris.

Structure	An elongated cylindrical body, pointed at both ends, round in cross section, is a body cavity
	Skin-muscular sac
Nervous system	Abdominal nerve cord
	Mouth (3 hard lips) --> pharynx --> intestinal tube --> anus
	Whole surface of the body
Selection	Through the surface of the body
reproduction	Most are dioecious; the female lays eggs that hatch into young worms
Representatives

Type annelids their characteristics

Type Annelids- a group of animals whose representatives have a body divided into segments resembling rings folded one after another. There are about 9 thousand species of annelids. Between the skin-muscle sac and internal organs they have in general- secondary body cavity filled with fluid.

Structure	The body consists of segments, there is a body cavity
	Leather; muscles - longitudinal and circular
Nervous system	Supraglottic and subpharyngeal nerve ganglions and the ventral nerve cord, from which the nerves depart in each segment
	Mouth --> pharynx --> esophagus --> crop --> stomach --> intestine --> anus
	the entire surface of the body; marine have special outgrowths of the body - gills
Selection	In each segment - a pair of tubules that open outwards with excretory pores
Reproduction of annelids	Hermaphrodite; the female lays eggs in a cocoon, from which young worms emerge
Manifold	1. Class Small-haired - live mainly in soil and fresh water, have small bristles on each segment (representative - earthworm) 2. Class Multi-haired - live in the seas; have paired outgrowths with bristles on the sides of the body (representative - nereid, sandworm)

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The source of information: Biology in tables and diagrams. / Edition 2e, - St. Petersburg: 2004.

All flatworms are three-layer animals (Fig. 79). They have a skin-muscular sac that forms the cover and muscles of the body. The excretory and digestive systems appear. The nervous system consists of two nerve nodes and nerve trunks. Free-living worms have eyes and tactile lobes. All flatworms are hermaphrodites and lay their eggs in a cocoon. Flatworms are divided into ciliary, tape and flukes.

Rice. 79. Worms are flat: 1 - liver fluke; 2 - pork tapeworm; 3 - echinococcus; round: 4 - roundworm, 5 - pinworm; ringed: 6 - leech, 7 - earthworm

Representative ciliary worms is a free-living white planaria. This animal is 2 cm long, milky white in color, living in ponds, slowly flowing rivers, quiet backwaters. Her body is covered with cilia, the main movement of which ensures the movement of the planaria along the bottom of the reservoir. Planaria is a predator that feeds on protozoa, coelenterates, daphnia and other small animals. The pharynx of the planaria is able to turn outward and, due to the suction cup, stick tightly to the victim.

All ciliary worms have the ability to regenerate. At adverse conditions they can break up into pieces, each of which is subsequently restored into a whole organism.

The length of echinococcus is only 1-1.5 cm. A person can become infected with it from dogs and other animals. Finn echinococcus is able to multiply, forming daughter blisters. Sometimes it grows to the size of a walnut, and in some cases it happens with the head of a child. This bubble can destroy tissue and can only be removed by surgery.

Ringed worms. These are more highly organized animals than those considered earlier. The body of annelids is segmented. The nervous system of the nodal type, the excretory system are well developed, the circulatory system of the closed type appears. There are tactile and light-sensitive cells.

Most famous earthworm. This worm lives in the soil, its body is segmented, on the underside there are bristles that are directly involved in the movement. If you put an earthworm on paper, you can hear the rustle produced by the bristles when the worm moves. It refers to class of small-bristle.

Worms do not have special respiratory organs. They breathe through their skin. Often after rain, earthworms crawl out to the surface of the earth: rainwater floods the worm's burrows, displacing oxygen from the soil, which makes it difficult to breathe.

Earthworms are bisexual animals, but their fertilization is cross. When mating, two individuals approach each other, overlap each other with their front ends and exchange male reproductive products. In a special belt - a clutch formed from mucus, eggs are injected on the 13th segment, which, moving with the clutch, are fertilized by sperm on the 9th segment. The clutch with fertilized eggs slides off the front and forms an egg cocoon. The eggs in the cocoon develop in the soil.

Earthworms are capable of regeneration. In a worm cut in half, the missing part can be restored.

Earthworms feed on fallen leaves, grass, passing through a large amount of soil, thereby loosening it, aerating and enriching it with humus. They play a very important role in soil formation.

Lives in polluted water bodies pipemaker, serving as food for fish and purifying water from organic contaminants.

In our fresh waters are found false horse leech black and gray-green medicinal leech. At medicinal leech in the depths of the oral cavity there are three ridges with pointed chitinous teeth. They are located at the vertices of the triangle, teeth to each other. While sucking, the leech cuts through the skin with them, releasing hirudin, preventing blood clotting. Hirudin stops the development of blood clots, is useful for hypertension, sclerosis, strokes, resolves subcutaneous hemorrhages.

Previously, medical leeches were widely used, but now they have become a rarity.

The large false-horse leech attacks earthworms, molluscs, and tadpoles. It does not cause any harm to a person, although it is sometimes sucked by the back sucker to the body of a person bathing in a pond.

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§ 58. Animal kingdom. Multicellular: sponges and coelenterates§ 60. Arthropods

There are three main types of worms: flat, round and annelids. Each of them is divided into classes into which the types of worms are combined according to the similarity of certain signs. In this article, we will describe types and classes. We will also touch on their individual types. You will learn basic information about worms: their structure, characteristics, role in nature.

Type Flatworms

Black, brown and live in silted places of ponds, lakes and streams. At the front end of the body, they have 2 eyes, with which they distinguish darkness from light. The pharynx is located on the ventral side. Planarians are predators. They prey on small aquatic animals that are torn apart or swallowed whole. They move thanks to the work of cilia. From 1 to 3 cm is the body length of freshwater planarians.

Their body is covered with elongated cells with special cilia (which is why they are also called ciliary worms). Deeper are 3 layers of muscle fibers - diagonal, annular and longitudinal. The worm (species related to planarians), due to their relaxation and contraction, shortens or lengthens, can lift parts of the body. A mass of small cells is located under the muscles. This is the main tissue in which the internal organs are located. A mouth with a muscular pharynx, as well as a three-branched intestine, make up the digestive system. The walls of the intestine are formed by a layer of flask-shaped cells. They capture food particles and then digest them. Digestive enzymes secrete glandular cells in the intestinal wall into the intestinal cavity. The nutrients formed as a result of the breakdown of food penetrate immediately into the tissues of the body. Undigested residues are removed through the mouth.

Ciliary worms breathe oxygen dissolved in water. This process is carried out by the entire surface of the body. they consist of clusters of cells - head paired nodes, nerve trunks extending from them, as well as nerve branches. Most planarians have eyes (from 1 to several tens of pairs). They have tactile cells in their skin, and some representatives of this class have small paired tentacles at the front end of the body.

Flukes class

Class Tapeworms

The nervous and muscular systems of this class are poorly developed. Skin cells represent their sense organs. Their digestive system has disappeared: tapeworms absorb nutrients from the host's intestines with the entire surface of their body.

Echinococcus

Class Nematodes

Nematodes are herbivorous worms that live on the roots of beans, garlic, onions and other garden plants, in underground shoots of potatoes (the species Stem potato nematode), in the organs of strawberries (Strawberry nematode). About 1.5 mm is the length of their almost transparent body. The nematodes pierce the tissues of plants with the mouth apparatus of the stabbing type, after which they introduce substances that dissolve the contents and walls of the cells. Then they absorb the resulting substances, using the expanded part of the esophagus for this. As a pump, its muscular walls act. Food is digested in the intestines. Many nematodes live in the ground and use plant debris as food. They play an important role in soil formation.

Roundworm

Its representatives live in fresh water, seas, soil. Their body is long, divided into annular segments (segments) by transverse constrictions. We are all well aware of the appearance of earthworms. Their length ranges from 2 to 30 cm. The body is divided into segments, which can be from 80 to 300.

The internal segmentation corresponds to the external segmentation. The body cavity of representatives of this type is lined with a layer of integumentary cells. A delimited area of ​​this cavity is located in each segment. Annelids have a circulatory system, and many of them also have a respiratory system. Their digestive, muscular, nervous, excretory systems, as well as the sense organs, are more perfect than those of round and flatworms. Their "skin" consists of a layer of integumentary cells. Under it are the longitudinal and circular muscles. In annelids, the digestive system is divided into the pharynx, oral cavity, esophagus, stomach (in some groups), and intestines. Undigested food remains are removed through the anus.

The circulatory system of annelids

All types of annelids have a circulatory system formed by the abdominal and dorsal blood vessels, which are interconnected by annular. Small vessels depart from the latter, which branch and form a network of capillaries in the internal organs and skin. Blood moves mainly due to the relaxation and contraction of the walls of the annular vessels covering the esophagus. It carries oxygen and nutrients that enter it to all organs, and also frees the body from metabolic products. Types of annelids are characterized by a closed circulatory system (this biological fluid is located within the vessels and does not pour into the body cavity). Breathing takes place through the skin. Some species have gills.

annelids

The nervous system in representatives of this type consists of paired sub-pharyngeal and supra-pharyngeal nerve nodes, which are connected into a ring by nerve cords, as well as nodes of the chain (abdominal). A paired node is located in each segment of annelids. Nerves go to all organs. Various stimuli (for example, light) affect sensitive cells. The excitation that has arisen in them is transmitted to the nearest nerve node along the nerve fibers, and then to the muscles (via other fibers) and causes their contraction. In this way, reflexes are carried out. Most representatives of this type have no sense organs.

The main classes of annelids

Ringed can be both hermaphrodites and dioecious. How many worms (species) does this type include? Today there are about 9 thousand of them, among which the main classes stand out: Polychaete and Low-bristle. The former live mainly in the soil (for example, such a type of earthworm as burrow), as well as in fresh water (in particular, tubifex). Polychaete worms - a class that includes sandworms, nereids and sickles. Sandworms live in the burrows dug by them, Nereids - mainly in silty soil, in the coastal parts of the seas, sickles - in "houses" that they build from various materials.

Nereids

Nereids are worm species that are most diverse in the seas. Their color is green or reddish. The head is formed by the anterior segments of the body. She has palps, a mouth, tentacles (organs of touch), as well as 2 pairs of eyes and 2 pits behind them (these are the organs of smell). On the segments on the sides of the body there are paired muscular short lobe-like outgrowths with tufts of setae. These are limbs. In addition, nereids develop gills - special outgrowths of the skin. Often they are dioecious animals. In the water, fertilization of eggs occurs, from which free-swimming larvae appear, having a belt of cilia. They eventually turn into adult worms.

Meaning of annelids

They are the food of many species of crabs, fish (nereids and other marine worms). Earthworms are the main food of hedgehogs, moles, starlings, toads and other animals. Ringed, feeding on silt, as well as various suspensions, free water from excess organic matter. In addition, earthworms and some other soil worms eat plant debris and also pass soil through their intestines. By doing this, they contribute to the formation of humus.

on the topic: "Characteristics of the types of worms: flat, round and ringed"

TYPE FLAT WORMS

CLASS PLANARIA, OR CIL WORMS

In the silted places of lakes, ponds and streams live white, brown, black planaria. At the front end of their body, two eyes are noticeable (distinguish light from darkness); on the ventral side is the pharynx. Planarians are predators. They attack small aquatic animals, "crush" them under themselves and swallow them whole or tear them apart. They move thanks to the coordinated work of cilia. The body length of freshwater planarians is 1-3 cm.

The world of marine ciliary worms is the richest and most diverse. Their large, wide, leaf-shaped body has a wide variety of colors. Large soil planarians (bipals) live in the wet litter of tropical forests, the body length of which reaches a length of 60 cm.

Internal structure and life. The body of flatworms is covered with elongated cells with cilia. Deeper are three layers of muscle fibers (annular, diagonal and longitudinal). Due to their contraction and relaxation, the worm lengthens or shortens, raises one or another part of the body, and flattens. Under the muscles there is a mass of small cells - the main tissue, and in it - the internal organs. The digestive system consists of a mouth with a muscular pharynx and a three-branched intestine, the walls of which are formed by a single layer of flask-shaped cells capable of capturing food particles and digesting them. The glandular cells of the wall secrete digestive substances into the intestinal cavity. The resulting nutrients penetrate into all cells of the body, and undigested food residues are removed through the mouth.

Ciliary worms breathe oxygen dissolved in water through the entire surface of the body. Substances that are unnecessary for the body, formed during life, are excreted, entering the tubules, which begin with large stellate cells with bundles of cilia inside (they create a fluid flow into the tubules). Small tubules gather into one or two large tubules with excretory pores.

The nervous system of ciliary worms is formed by clusters of nerve cells - paired head nodes, nerve trunks and nerve branches extending from them. Most ciliary worms have eyes (from one pair to several dozen), tactile cells in the skin, and some have small paired tentacles at the front end of the body.

Reproduction of eyelash worms. Flatworms are usually hermaphrodites. Freshwater ciliary worms, such as planarians, lay their fertilized eggs in cocoons formed from solidified mucus. Developed small worms break the walls of cocoons and come out. In marine ciliary worms, floating larvae emerge from fertilized eggs, which then acquire the features of adults.

CLASS TRUCKS AND CLASS TAPED WORMS

The muscular and nervous systems of tapeworms are poorly developed, and the sense organs are represented by sensitive skin cells. Their digestive system has disappeared: they absorb nutrients from the host's intestines by the entire surface of the body.

The reproductive system has the greatest development in tapeworms. Almost all of them are hermaphrodites. Their last segments seem to be stuffed with eggs with developing embryos. The segments are separated from the body of the worm and come out with the feces of the host or on their own (due to muscle contraction). Up to 28 segments containing up to 5 million eggs are excreted per day by a sick person. Together with the grass, the eggs enter the stomach of the intermediate host - cows (bovine tapeworm), pigs (pork tapeworm). In the stomach, six-hooked larvae emerge from the eggs, which penetrate into the blood vessels of the intestine, and then into the muscles. Here the larvae turn into Finns, which look like a bubble the size of a pea. When eating insufficiently fried or boiled Finnose meat, a person becomes the main host of the worm. In the human stomach, the head turns out of the Finn, and the bubble itself is digested. A small worm enters the intestine, sticks to its wall, and its neck begins to form segments.

The development of a wide tapeworm is associated with the change of two intermediate hosts (Cyclops crustaceans and fish). The main owner is a human.

Echinococcus- small worm (length up to 6 mm). Unlike tapeworms and tapeworms, the segments do not separate from its body. The main hosts of Echinococcus are dogs, wolves, foxes, cats; intermediate - a sheep, a cow, a goat, a deer, a pig (maybe a person). In the liver, lungs, muscles, bones of intermediate hosts, large blisters develop (a variety of Finns), in each of which child and granddaughter blisters with heads inside develop. The main hosts become infected by eating meat with echinococcal blisters, and the intermediate hosts become infected by eating food contaminated with the feces of sick dogs, wolves and other main hosts of echinococcus.

TYPE ROUND, OR CAVITY WORMS

Roundworms have a non-segmented, usually long body, rounded in cross section. On the surface of the skin there is a dense non-cellular formation of the cuticle. These worms had a body cavity formed as a result of the destruction of the cells of the main tissue between the body wall and internal organs (primary body cavity). The musculature of roundworms consists of a layer of longitudinal fibers. Therefore, they can only bend. The intestine of roundworms, having the form of a tube, begins with the oral opening and ends with the anal (anal).

Herbivorous nematodes live on the roots of onions, garlic, beans and some other garden plants (onion nematode), in underground shoots of potatoes (stem potato nematode), in various organs of strawberries (strawberry nematode). The length of their almost transparent body is about 1.5 mm. Nematodes use their piercing mouthparts to pierce plant tissues, introducing substances into them that dissolve the contents of plant cells. They suck up the dissolved substances with the help of an expanded part of the esophagus, the muscular walls of which act as a pump. Food is digested in the intestines. Many nematodes live in the soil, feed on various plant debris and have great importance in soil formation.

Roundworms live in the small intestine of the host. The body length of the female is up to 40 cm (males are smaller). Ascaris feed on semi-digested food. The eggs laid by females (about 200 per day) are excreted in human feces. In the external environment, mobile larvae develop in eggs. Human infection with roundworm eggs occurs when eating poorly washed vegetables, food frequented by flies.

In the intestines of the host, the larvae emerge from the eggs, invade the blood vessels, and enter the liver, heart, and lungs. Grown up larvae from the lungs enter the mouth, and then into the intestines, where they become adults. Roundworms feed on the host's food, poison it with their secretions, cause ulcers to form on the intestinal walls, and in large numbers - intestinal obstruction and rupture of its walls.

Adult Trichinella (the body length of females is about 4 mm) live in the lumen of the small intestine, and the microscopic larvae they give birth to penetrate into the muscles, where they grow, twist into a spiral and, having formed a capsule around themselves, go into a resting state. The source of human infection is the meat of animals, especially pigs, which acquire Trichinella by eating small mammals, such as rats.

TYPE ANNELS

GENERAL CHARACTERISTICS OF ANELLATED WORMS

Ringed worms live in the seas, fresh water, soil. They have a long body, divided by transverse constrictions into annular segments (segments). External segmentation corresponds to internal segmentation. The body cavity of these worms is lined with a layer of integumentary cells (secondary body cavity). Each segment contains a delimited portion of this cavity. Annelids have a circulatory system, and many have a respiratory system. Their muscular, digestive, excretory, nervous systems and sense organs are more perfect than those of flat and round worms.

The skin of annelids consists of a single layer of integumentary cells (some of which secrete mucus). Under the skin are circular and longitudinal muscles. The digestive system is noticeably divided into the oral cavity, pharynx, esophagus (in some, its expansion is formed - goiter), stomach (in some groups) and intestines. Undigested food remains are removed through the anus. The circulatory system of annelids is formed by the dorsal and abdominal blood vessels, interconnected by annular vessels. Small blood vessels branch off from these vessels. They branch and form in the skin and internal organs a dense network of tiny vessels - capillaries. Blood (usually red) moves mainly due to the contraction and relaxation of the walls of the annular vessels covering the esophagus. It carries nutrients and oxygen to all organs of the body and frees the organs of the body from unnecessary metabolic products. The circulatory system of annelids is closed (blood does not leave the blood vessels). Respiration in annelids occurs through the skin. Some marine worms have gills.

The excretion of substances (metabolic products) unnecessary for the body in earthworms occurs with the help of excretory tubes, starting with funnels with cilia (a pair in each segment). The excretory ducts open outwards on the ventral side of the next segment. In some annelids, the tubules begin with cells with a bundle of cilia inside.

The nervous system of annelids consists of paired supraesophageal and subpharyngeal ganglions, connected by nerve cords into a peripharyngeal ring, and nodes of the abdominal nerve chain (each segment of the worm contains a paired ganglion). Nerves extend from nerve nodes to all organs of the body. Light and other stimuli act on sensitive cells. The excitation that has arisen in them is transmitted along the nerve fibers to the nearest nerve node, and then along other nerve fibers to the muscles and causes their contraction. So this or that reflex is carried out. The sense organs of most annelids are absent.

Among annelids, there are both dioecious and hermaphrodite. The development of marine worms occurs with the larval stage.

The ability to regenerate in annelids is worse than in flatworms.

The type of annelids includes 9 thousand species. Main classes: Small-bristle worms and Polychaete worms.

CLASS LITTLE WORMS

Habitat, structure and lifestyle.

Small-bristle worms live mainly in the soil (earthworms) and in fresh water (tubifex). Earthworms (about 1500 species) have a long body, consisting of 80 or more rings. Setae (usually two bundles) are located on the sides of each ring, except for the mouth ring. There are no sense organs (there are olfactory, tactile, gustatory, photosensitive cells). Earthworms feed mainly on decaying organic residues containing bacteria. Food is captured by the mouth located on the first segment of the body. Earthworms come to the soil surface at dusk and at night. They move by alternately contracting and relaxing the circular and longitudinal muscles. The bristles have a reference value when moving and making passages in the soil. Moving in loose soil, the worm pushes its particles apart, and in dense soil it passes them through the intestines. With the onset of drought or cold weather, earthworms go deep into the soil. Tubifex live at the bottom of water bodies, forming dense settlements. The anterior part of their filamentous body (2/3) is usually located in a tube of mucus and soil particles, the posterior part is free and makes "breathing" movements. Tubifex feed on the organic remains of the soil. Reproduction. Earthworms are hermaphrodites. Before laying eggs, two worms approach each other by the front ends of the body and exchange seminal fluid containing spermatozoa, which enters their seminiferous receptacles. Then, when the eggs mature, each worm on the girdle (this is a glandular thickening of the skin of several specific segments) begins to form a cocoon: the girdle secretes mucus, which forms a muff. By contractions of the body of the worm, the muff is shifted to the front end of the body. Eggs and liquid with spermatozoa get into it. The muff turns into a cocoon, where the fertilization of the eggs takes place. The developed worms break the cocoon and come out of it.

CLASS POLYCHETATE WORMS

Polychaete worms include various types of nereids, sandworms, sickles. Nereids live mainly in the coastal parts of the seas, in muddy soil; sandworms - in the minks dug by them; serpules sit in "houses" built of various materials. At their front end there is a sultan of tentacles with which they filter the water.

The most diverse Nereids in the seas. They have a reddish or green color, shimmering with all the colors of the rainbow. The anterior segments of the body form a head with a mouth, palps and tentacles (organs of touch), two pairs of eyes and two pits behind them (organs of smell). On the sides of the body of nereids on the segments are short, muscular paired lobe-like outgrowths - parapodia with tufts of setae. These are Nereid limbs. Nereids develop special outgrowths of the skin - gills.

Nereids are dioecious animals. The eggs are fertilized in water. The eggs hatch into free-swimming larvae with a band of cilia. Over time, the larvae take on the appearance of adult worms.

ORIGIN AND SIGNIFICANCE OF ANNELS

Origin. Scientists believe that ancient annelid worms evolved from ancient free-living flatworms. Evidence of this is, for example, the presence of cilia in the larvae of marine annelids, excretory organs beginning with stellate cells with a ciliary flame, and the similarity of the nervous system with the nervous system of planarians. Polychaete worms are older than oligochaetes, although they have the most complex structure. The simplification of the structure of oligochaete worms occurred mainly in connection with the transition to life in the soil.

Meaning. Nereids and other marine worms are the main food of many species of fish, crabs and other inhabitants of the seas; many fish and freshwater invertebrates feed on tubifex; earthworms are the main food of moles, hedgehogs, toads, starlings and other land animals. Feeding on silt, various suspensions, annelids free water from excess organic matter. Earthworms and some other soil worms, eating various plant debris and passing soil through their intestines, contribute to the formation of humus. The minks they make are filled with air necessary for the respiration of plant roots and various soil-forming organisms living in the ground.

TYPES FLAT, ROUND AND RINGED WORMS.

FOR ONE REPRESENTATIVE FROM THE TYPE OF FLAT, ROUND AND ANELLATED WORMS CHOOSE THE APPROPRIATE CHARACTERISTICS:

1. Representatives

1. White planaria. 4. Roundworm.

2. Liver fluke. 5. Earthworm.

3. Bull tapeworm. 6. Nereid.

1. Type flatworms.

2. Type roundworms.

3. Type annelids.

1. Class flukes.

2. Class tapeworms.

3. Class ciliary worms.

4. Class oligochaete worms.

5. Class polychaete worms.

4. Habitat.

1. Settle in organs rich in blood.

2. Settle in the intestines of humans and animals.

3. Lives in fresh water: ponds, rivers, lakes.

4. Lives in salt water: seas and oceans.

5. Lives in soil rich in humus.

5. Body shape.

1. The body is elongated, round in cross section.

2. The body is flattened - leaf-shaped.

3. The body is flattened-elongated.

4. Body flattened-ribbon.

5. The body is elongated, oval in cross section.

6. Division of the body into segments.

1. The body is divided by constrictions into segments.

2. There are no constrictions. The body is not divided into segments.

7. The presence of a cavity between the organs.

1. Internal organs located in a body cavity filled with

liquid.

2. There is no body cavity. Gaps between organs

filled with cells.

8. Integuments of the body.

1. There are numerous cilia on the skin.

2. On the segments of the body there are lobes with long setae.

3. Short bristles are located on the segments of the body.

4. There are no bristles and cilia on the body. Covers are smooth and

5. There are no bristles and cilia on the body. Covers are smooth and

9. Musculature of the body.

1. There are longitudinal, annular and dorsal-abdominal layers

2. There are longitudinal and circular elephant muscles.

3. There is only a longitudinal layer of muscles.

10. Nutrition.

1. They feed on the tissues of human and animal organs.

2. Eat prepared, digested food.

3. They feed on decayed plant residues.

4. They feed on small invertebrates.

11. Digestive organs.

1. Mouth, pharynx, esophagus, intestines ending in anal

hole.

2. Mouth, pharynx, esophagus with goiter, stomach, intestines

ending in anus.

3. Mouth, pharynx, esophagus, intestinal branches ending

4. There are no digestive organs. Food is absorbed through

the entire surface of the body.

12. Circulatory organs.

1. The circulatory system is closed. Consists of dorsal and

abdominal vessels with ring bridges.

2. There are no circulatory organs.

13. Respiratory organs.

1. Breathes oxygen dissolved in water with the help of gills.

2. There are no respiratory organs. Oxygen enters the body

across the entire surface of the body.

14. Nervous system.

1. Consists of a cerebral ganglion and nerves extending from it

trunks with branches.

2. Consists of a peripharyngeal nerve ring and outgoing from

its nerve trunks with branches.

3. Consists of a peripharyngeal nerve ring and abdominal

nerve chain with branches.

15. Sense organs.

1. The sense organs are well developed.

2. The sense organs are poorly developed.

16. Reproduction,

1. They reproduce asexually, breaking up into parts,

regenerating to a whole worm. known and sexual

reproduction by the fusion of sperm with eggs.

2. They reproduce only sexually. Animals are bisexual

Hermaphrodites.

3. They reproduce only sexually. Animals

dioecious.

17. Oviposition.

1. Eggs are laid openly.

2. Eggs are laid in a cocoon.

18. Development.

1. Development is direct, proceeds without transformation.

2. Development is indirect, proceeds with transformation. There is

larval stages. The ultimate master is man,

intermediate host - cattle.

3. Development is indirect, proceeds with transformation. There is

larval stages. Definitive host - large

cattle, intermediate host - gastropod mollusk.

4. Development is indirect, proceeds with transformation. Larva

free-floating in the water column.