Integuments of the body Outside, the body is covered with a single-layer epithelium. In ciliary worms, or turbellaria, the epithelium consists of cells that carry cilia. Flukes, monogeneans, cestodes, and tapeworms lack ciliated epithelium for most of their lives (although ciliated cells may occur in larval forms); their covers are represented by the so-called tegument, in a number of groups bearing microvilli or chitinous hooks. Tegumented flatworms belong to the Neodermata group. Flatworms can regenerate 6/7 of their body.

Musculature Under the epithelium there is a muscular sac, consisting of several layers of muscle cells that are not differentiated into individual muscles (a certain differentiation is observed only in the region of the pharynx and genital organs). The cells of the outer muscle layer are oriented across, the inner - along the anterior-posterior axis of the body. The outer layer is called the layer of circular muscles, and the inner layer is called the layer of longitudinal muscles.

Nervous system and sensory organs The nervous system is represented by nerve nodes located in the anterior part of the body of the worm, cerebral ganglia and nerve columns extending from them, connected by jumpers. The sense organs, as a rule, are represented by separate skin cilia - processes of sensitive nerve cells. Some free-living representatives of the type, in the process of adapting to living conditions, acquired light-sensitive pigmented eyes - primitive organs of vision and organs of balance.

Structure The body is bilaterally symmetrical, with clearly defined head and tail ends, somewhat flattened in the dorsoventral direction, in large representatives it is strongly flattened. The body cavity is not developed (with the exception of some phases of the life cycle of tapeworms and flukes). The exchange of gases is carried out through the entire surface of the body; respiratory organs and blood vessels are absent.

Questions: How many flatworms live in Russia? What are the body coverings of flatworms? What kind of muscles? What are the sense organs? Briefly describe the structure of the body. How do flat people eat? How do they breathe? How do they reproduce?

Interesting Facts 1. By digestion, flatworms are able to "learn". A group of scientists have made an unusual discovery regarding the abilities of flatworms. It turns out that if planar worms are first taught to go through the maze, then grind them into a puree and let other worms eat it, then such worms will be able to go through this maze the first time.

Interesting facts 2. Heterogenous species of worms - schistosomes are inseparable throughout life. The female lives in the pocket of the male all her life.

Interesting facts 3. Almost all types of flatworms can turn inside out. 4. And here are some more interesting facts about flatworms. For example, flatworms are truly almost immortal. If you cut off a very small piece from the worm, approximately 1/100 of the whole worm, it is still able to recover to the whole organism.

Interesting facts 5. On the skin of some planarians living in fresh water, scientists have found nettle cells, which are very similar to stinging cells found in coelenterates. It turns out that these cells really belonged to coelenterates, which subsequently ate the ciliary worms. Stinging cells are not digested by worms. They get into their skin and serve to perform a protective function and attack.

L i

Worms are a fairly common species on earth. Roundworms differ from flatworms both in appearance and in the construction of internal vital systems. However, there are not only differences between these species. Worms of these classes do not have a circulatory and excretory system in the traditional sense, but their life cycle is the same. Adults become dangerous.

The differences between roundworms and flatworms are not significant, but the harm to human health is significant.

General information on the comparison of flatworms and roundworms

Flat individuals have a flattened body (often ribbon-like). They also differ in the presence of 3 muscle layers:

• annular;
• diagonal;
• longitudinal.

roundworms

• A cylindrical thin body, consisting of the so-called outer cuticle, under which there is an epithelial layer and muscles running along.
• Fluid fills the body (hydroskeleton).
• The structure of the digestive system is simple. This is a tube with mouth and excretory openings. It is conditionally divided into 3 parts - front, middle and back.
• The nervous system is represented by the pharyngeal ganglion (a kind of brain). The nerve trunks branch off from the ganglion. Roundworms have a sense of touch and taste.

The main differences between roundworms within a species are their habitat. It should be noted that, unlike flat ones, round ones are bisexual. Males and females are usually distinguishable. This type has more than 15 thousand species living almost everywhere. Some can be seen under a microscope, but there are, in comparison, giants.

flatworms

• ciliary;
• tape;
• flukes.

The structure of flatworms is somewhat different from roundworms. Namely:

Flat representatives, with rare exceptions, are same-sex. Their breeding system is quite complex. In addition to the present symbiosis of male and female genital organs, this includes additional appendages and formations that fully ensure the process of fertilization and development of the embryo, by providing it with all the necessary substances.

What is the difference?

What common?

Any worms that have entered the human body are dangerous for him, especially if they are not noticed in time and adequate treatment is not applied. Helminths can cause many diseases, including: ulcers, colitis, intestinal obstruction, cysts, damage to the central nervous system, meningitis. Among the most dangerous species are flukes, paragonims and schistosomes, echinococci, roundworms, hookworms, trichinella.

The causative agent of opisthorchiasis: what it looks like, structure, habitat

The first case of the appearance of opisthorchis was recorded in 1884, when a helminth, previously unknown to science, was found in a cat in the northern part of Italy. S. Rivolta called the helminth a cat fluke.

7 years after the first case, the cat fluke was already found in the human body in Russian Siberia. In 1891, professor-pathologist K. N. Vinogradov conducted research on the liver and found a leaf-shaped worm in it, which he gave the name of the Siberian fluke. Further studies have shown that the Siberian fluke is nothing more than a previously caught cat fluke. Subsequently, the helminth was given the name opisthorchis, and the disease began to be referred to as opisthorchiasis.

The structure and appearance of the helminth

Unlike other representatives of its class, opisthorchis is much smaller. This is what a helminth looks like: the body of a feline fluke is shaped like an oblong flat leaf or lancet, its length rarely exceeds 18 millimeters, and its width varies from 1.5 to 2 millimeters.

There are two suckers on the body of the helminth, one is the abdominal sucker, and the other is the oral sucker, with the help of which the opisthorchis is attached to the mucous membranes of the damaging organs and sucks out nutrients. The oral sucker of the helminth serves as the beginning of its digestive tract. At the rear end of the body there is a special channel through which the excretion of processed waste products of the worm is carried out.

The reproductive system of the causative agent of opisthorchiasis is based on the hermaphroditic principle. The helminth has two pairs of genital organs. Reproduction of opisthorchis occurs by the release of eggs. One individual of the worm in the body of its final host is capable of producing 900-1000 eggs daily.

The eggs of opisthorchis are pale yellow in color, have a delicate double-circuit shell, there is a special cap on one pole of the eggs, and the other pole is slightly thickened. The size of helminth eggs varies from 0.011 to 0.019 in width and from 0.023 to 0.034 in length.

Habitat and endemic foci

The habitat of opisthorchis eggs is freshwater reservoirs, in such conditions they are able to maintain their vital activity for one year. It should be noted that opisthorchis develop with the participation of three carriers - one final host and two intermediate ones.

Considering that the helminth develops in freshwater reservoirs, special endemic foci are distinguished, where the probability of infection with opisthorchiasis is high. These endemic foci include:

1. Yamalo-Nenets Aut. district, Khanty-Mansiysk Aut. district, regions of Siberia, Altai Republic. Endemic foci in Russia are also confined to the basins of the Irtysh, Ob, Volga, Northern Dvina, Kama, Don, Dnieper, Biryusa.
2. Ukraine and Kazakhstan.
3. Italy, France, Holland.
4. India, Thailand, other countries of Southeast Asia where fishing prevails.
5. Canada and Northern regions of the USA.

The development of the causative agent of opisthorchiasis

The causative agent of opisthorchiasis belongs to biohelminths, which means that a change of owners is necessary for its successful life. In this case, as mentioned above, the trematode has one final and two intermediate hosts; in their organisms, it goes through a complete life cycle.

The cycle of opisthorchis begins in the body of the final host, which is a person, as well as some mammals (cats, dogs, pigs, foxes, and others). Sexually mature individuals lay eggs, together with the host's feces they enter the environment, under favorable conditions they continue their development.

Once in water bodies, opisthorchis eggs settle to the bottom, where they are eaten by freshwater mollusks. In their organisms, the larvae of opisthorchis, miracidia, emerge from the eggs. Miracidia have special cilia, penetrating into the intestinal wall of the mollusk, they lose them and turn into the maternal sporocyst. The sporocyst gives rise to rediae, which in turn develop into cercariae. Tailed cercariae exit the body of mollusks through the cover or mouth opening and begin hunting for the second intermediate host.

The second intermediate host of the pathogen of opisthorchiasis is a fish of the carp family. The fish swallows them through the mouth opening, and cercariae can also enter its body through the lateral lines and integument. In the organisms of cyprinids, cercariae are localized in the muscles and subcutaneous tissue, turning into metacercariae. Metacercaria larvae are slightly oval in shape, measuring 0.34 mm long and 0.24 mm wide. Metacercariae develop in the body of fish for a month and a half, during which time they become invasive to humans.

How does the infection of the final host occur? The causative agent of opisthorchiasis enters the human (animal) body when eating raw or insufficiently thermally processed fish. In the human body, metacercariae reach their sexual maturity as early as 10-14 days. The main centers of impact are the liver, its ducts, gallbladder and pancreas. Characteristic symptoms appear two to three weeks after the onset of the invasion.

Opisthorchiasis proceeds in two stages, this is due to the peculiarities of the life cycle of the helminth. This implies the difference in the clinical picture for the period of invasion and the later period. Entering the human body in the stage of metacercaria, the helminth develops to the stage of puberty, and then for many years lives in its usual places of localization.

In the early stages, the causative agent of opisthorchiasis provokes the development of an allergic reaction, which is very pronounced. A similar reaction of the human body is due to the fact that the helminth secretes enzymes and metabolic products that have a toxic effect.

• In the lymphatic system, inflammatory processes occur, the same phenomena are observed in the spleen.
• Purulent-inflammatory reactions can be found in the mucous membranes of the gastrointestinal tract, respiratory system.
• There is a violation of blood microcirculation in the internal organs, first of all, the part of the circulatory system located in the liver suffers.
• Hypoxic signs develop, gas exchange is disturbed.
• Dystrophic changes are observed in the liver, heart and other organs.

The rate of development of pathological changes in the human body directly depends on the degree of intensity of invasion.

The chronic stage of opisthorchiasis is characterized by mechanical, allergic and neuro-reflex harmful effects of the helminth. There is a secondary influence of the microbial flora, as well as the influence of the decay products of their own cells and tissues, most of all the cells of the gallbladder. Without timely diagnosis and treatment, the development of chronic cholangitis, pericholangitis, hepatitis, cirrhosis of the liver is likely.

Neuro-reflex exposure is fraught with violations of the tone of the gallbladder and biliary tract, secretory dysfunction, impaired motor function of the stomach and intestines.

Symptoms of opisthorchiasis, as a rule, include the clinical picture of a disease such as chronic gastroduodenitis. The peculiarity is associated with a pathological change in the functions of the pancreas and adrenal glands, as well as with the development of inflammatory processes in the mucous membranes of organs. The causative agent of opisthorchiasis also provokes hormonal instability.

Treatment of opisthorchiasis should be immediate and mandatory, neglected cases of the disease lead to the development of liver cancer. Prevention of opisthorchiasis consists in the correct and sufficient processing of freshwater fish before eating it.

source

Tapeworms (cestodes)

The oldest traces of cestodes are found in the remains of sharks living 270 million years ago.

Human infection

People can become infected with several types of tapeworms in different ways. When eating undercooked meat: pork (pork tapeworm), beef (bovine tapeworm) and fish (wide tapeworm). Or when living and eating in conditions of poor hygiene - pygmy and rat tapeworms, echinococcus.

Treatment

Now for the treatment of tapeworms, the main drugs are Praziquantel and Albendazole. Praziquantel is an effective agent that is more preferable than the obsolete Niclosamide. Cestodosis can also be treated with certain types of antibiotics. Doctors after a course of drugs can give enemas to patients to completely remove the worms from the intestines.

Structure

The main common elements of the cestode body. Others may differ (the presence of a rim with hooks, suction cup types may be slit-like, etc.)

Larvae, in contrast, show a wide range of habitat preferences and can be found in almost any organ of both vertebrate and invertebrate hosts. Although most larval species have a preference for a particular organ.

The absence of a gastrointestinal tract markedly separates cestodes from nematodes and trematodes. The outer tegument (special epithelium) of the body serves not only as a protective covering, but also as a metabolically active layer through which nutrients are absorbed, along with secretions and waste products transported out of the body. To facilitate this process, the entire surface of the body is covered with microscopic wrinkles or protrusions, which greatly increase the surface area available for absorption of nutrients.

Worms do not need to move inside the host body, so they do not have any organs of the musculoskeletal system and external bristles.

They also lack circulatory and respiratory systems.

The excretory and nervous systems of cestodes are similar to those of other representatives of flatworms.

Proglottid

The body of helminths of this class consists of a chain of segments (proglottids), which can be immature or mature, the last of which are at the end of the body and contain a fully formed uterus filled with eggs.

The totality of all proglottids (from two to several thousand) is called a strobila. It is thin and resembles a strip of tape. This is where the common name “tape” comes from.

New segments grow from the neck, containing an independent digestive and reproductive system. By the time the segment reaches the end of the worm's tail, only the reproductive organs remain. In fact, such segments are already just egg bags. The segment then separates from the body, carrying the tapeworm eggs out of the definitive host along with the feces.

Thus, each cestode consists of a series of segments that have a complete set of reproductive organs in a progressive degree of sexual maturity, which bud from the body from the side of the tail.

scolex

Life cycle

The life cycle of cestodes includes an intermediate and definitive host (with the exception of the pygmy tapeworm, which can develop in the same organism). It consists of several stages.

At the first stage, sexually mature individuals of tapeworms are in the body of the final host (vertebrates and humans), multiply and produce eggs, which are subsequently excreted into the environment along with feces.

At the second stage (depending on the type of cestodes), a larva (embryo) is formed in the eggs on land or in water.

At the third stage, the larvae enter the organism of the intermediate host (vertebrates and invertebrates), where Finns are formed from them. Finna is a spherical bubble (less often worm-shaped), filled with liquid, inside of which there is one or more heads. Depending on the number of heads, as well as on the presence of child bubbles inside, there are 5 forms of Finns:

• cysticercus;
• cysticercoid;
• tsenur;
• echinococcus;
• plerocercoid.

At the fourth stage, the Finns enter the body of the final host, their shell disappears, and segments begin to grow from the heads attached to the walls of the intestine. Thus, at this stage, the growth and development of adults occurs.

The most common representatives

Pork and bovine tapeworm (tapeworms)

Infections caused by ingestion of larvae of representatives of the genus Tepni, in humans or animals, are called teniidoses. The presence of an adult worm in the body (taeniasis and teniarhynchosis) rarely causes symptoms other than minor intestinal disorders (diarrhea, constipation or indigestion).

Bovine tapeworm does not cause human cysticercosis.

dwarf tapeworm

The pygmy tapeworm (Hymenolepis nana) is the smallest member of the tapeworm genus that infects humans. This cestode belongs to a large family known as Hymenolepis. Diagnostic features of this family: scolex contains 24-30 hooks; the adult has one to three large testes and a sac-like uterus.

The dwarf tapeworm is cosmopolitan, i.e. widely distributed throughout the world. Infection is more common in children, although adults can also be infected (developing hymenolepiasis). The disease may not cause any symptoms even with significant infection. However, some cases of anxiety, irritability, anorexia, abdominal pain, and diarrhea have been reported in hymenolepiasis.

The life cycle of Hymenolepis nana does not necessarily require an intermediate host, full development occurs within the gut of a single host (the "direct" life cycle). It may also use insects as an intermediate host.

wide ribbon

As a rule, they have a scolex, which is characterized by two shallow elongated bothria (slits), located one dorsally (on the back) and the other ventrally (on the ventral side). The proglottids are flattened dorsoventrally, i.e. from dorsal to ventral.

Flatworms, which are included in the group of bilaterally symmetrical, are studied by the science of biology. Flatworms (Platyhelminthes) are not the only representatives of this group; more than 90% of animals belong to it, including annelids and roundworms, arthropods, mollusks, etc.

Types of flatworms are diverse and distributed throughout the world. There are about 25 thousand of them.

Scientific classification of flatworms

Flatworms belong to the kingdom Bilateral (symmetrical on both sides). In connection with some disputes that have arisen when trying to divide flatworms into different groups, scientists attribute them to a paraphyletic group. It includes representatives of a small part of the descendants of the same ancestors.

The structure of the internal organs of a flatworm

The body of flatworms is elongated and flattened, without a cavity inside. That is, its entire space is filled with cells. Inside are layers of muscles, which, together with the shell of the worm, form a musculocutaneous sac.

There are systems of internal organs:

• The digestive system is represented by a mouth and a blind (having no exit) intestine. Nutrients enter through the mouth, and can be absorbed through the entire surface of the body.
• The nervous system consists of brain ganglia and nerve columns. Some classes of flatworms have primitive organs of balance and vision.
• The excretory system consists of special tubules, but most often the excretion occurs over the entire surface of the body.
• The reproductive system is represented by both female (ovaries) and male (testes) reproductive organs. Flatworms are hermaphrodites.

Differences between flat and roundworms

Roundworms differ from flatworms in that their body has a round shape in cross section. Roundworms are also called nematodes. Possessing a bilaterally symmetrical body structure, they have developed muscles. But the main difference from flatworms is that round ones have an internal body cavity, while flat ones do not.

Variety of classes of flatworms

The table "Flatworms" clearly shows the division of the species into classes, of which modern science has seven.

class name	Habitat		Life cycle
Monogeneans (flukes)	With the help of an attachment disc at the posterior end of the worm, Monogenea is attached to the gills of fish and the skin of amphibians and turtles.	Very small, on average no more than 1 mm	For the whole life, the worm has one host, to which it enters in the form of a free-swimming larva
cestoid		Length ranges from 2.5 to 38 cm	The larvae develop in the body of crustaceans when the egg is swallowed. After eating a crustacean by aquatic vertebrates, an already adult individual easily moves from the intestines of a new host to the body cavity, where it lives and reproduces.
aspidogaster	They live in the bodies of molluscs, freshwater and marine fish	An adult rarely reaches a size of more than 15 mm	Changes of hosts occur several times during the life cycle of worms
Trematodes (flukes)			They have multiple owners throughout their lives. The larva lives first in which it subsequently dies. Ingested by ingestion of cercariae (ready to settle in the organs of the final larval host)
Gyrocotylides		2 to 20 cm	Hypothetically, the larvae first develop in the body of the intermediate host, and only then move into the fish. But due to the fact that chimeric fish are deep-sea, the hypothesis has not been experimentally confirmed.
Tape	The habitat of flatworms is the intestines of a mammal and a person, to the wall of which they firmly stick with the help of a head.	They can reach sizes up to 10 m.
Eyelash	Mostly free-living worms, live in fresh and salt water bodies, sometimes in moist soil	Body length ranges from microscopic to 40 cm	A larva that looks like an adult worm emerges from the egg, living among plankton until it grows up.

Eyelash worms

They are predators that eat small invertebrates, arthropods and even large molluscs. They swallow small prey whole or tear off pieces from it with strong sucking movements.

The body of worms is able to regenerate itself. A prominent representative is the planarian, in which even a small part of the body grows anew into a full-fledged individual.

Flatworms in home aquariums

Helminths can be a big problem for aquarium hobbyists.

The habitat of flatworms is mostly aquatic. Being flukes, flatworms can attach by means of an attachment disk to the surface of the gills and skin of aquarium fish.

Adult worms lay eggs, which hatch into larvae that live on the skin of the fish. Gradually, they crawl onto the gills, where they grow, reaching puberty.

Some types of flatworms get into the home aquarium with soil, live food. Their larvae can be on the surface of algae, on the skin of new fish inhabiting the aquarium.

• Pseudophyllidea (wide tapeworm). Infection with them can occur if raw, poorly salted fish is present in the diet. In the human small intestine, the tapeworm can live for decades, reaching a length of up to 20 m.
• Aeniarhynchus saginatus ( bull tapeworm). The habitat of flatworms is the intestines of humans and cattle. Sticking to its walls, the helminth grows up to 10 m. The larvae can be in other internal organs, in hard-to-reach places (brain, muscles, liver), so it is often impossible to completely get rid of them. The patient may be fatal. Infection occurs when helminth eggs enter the stomach with insufficiently thermally processed food, from dirty hands.
• Echinococcus (Echinococcus) is often found in dogs and cats, from them passing into the body to humans. Despite their small size - only 5 mm - the ability of its larvae to form Finns that paralyze internal organs is deadly. The larvae are able to penetrate into the respiratory, bone, urinary systems. Echinococcus flatworms are often found in the brain, liver and other internal organs. A person can easily become infected with larvae excreted in the feces of a dog, which spread to the coat, and from there to all household items and food.
• The liver fluke is the culprit of cholecystitis, hepatic colic, disruption of the stomach and intestines, and allergies. The habitat of flatworms is mainly the liver of humans and warm-blooded animals, the biliary tract. The body length of the fluke does not exceed 3 cm. The peculiarity is that not only mature individuals, but also their larvae, are capable of reproduction.

Prevention of helminth infection

Preventive measures for the entry of eggs and larvae of helminths into the human body are as follows:

• It is necessary to wash hands thoroughly with soap and water before each meal, after visiting public places, toilets, streets, communicating with pets.
• Wash raw vegetables and fruits with warm soapy water.
• Do not eat raw meat and fish.
• Long-term heat treatment of food, especially meat, fish.
• Pay attention to the timely prevention of helminthic invasions of domestic animals.
• Regularly, at least once a year, take a stool test for worm eggs.

check yourself 1. name the main groups included in the type of flatworms and characteristic distinguishing features using the example of representatives of each

2. What is the way of life of representatives of various groups of flatworms? how are the features of the structure of worms related to the image life. And habitat?

1) Name the main groups included in the type Flatworms, and their characteristic distinguishing features using the example of representatives of each group.

2) what kind of lifestyle do representatives of various groups of flatworms lead? How are the structural features of worms related to the way of life and habitat?

.Name the main classes of the type Flatworms and their characteristic distinguishing features using the example of representatives of each class. 2. What lifestyle do they lead

representatives of different classes? How are the structural features of worms related to their way of life and their habitat? 3. Using the example of the structural features of flat, round and annelids, list the signs of organization complication in comparison with intestinal cavities. 4. What diseases do flatworms cause? What is their prevention? 5. What features of the structure and lifestyle are typical for representatives of the type Roundworms? 6. Why did annelids get such a name? What is characteristic of the structure of each segment? 7. Based on what features do annelids belong to more complex animals than previously studied

11 Flatworms a) have bilateral symmetry b) a skin-muscular sac c) a special excretory system d) all answers are correct

12 Ascaris body cavity a) filled with connective tissue b) filled with liquid c) filled with air d) absent
13 In each segment of the body of an earthworm, a) nerve nodes b) excretory tubes c) annular blood vessels d) all answers are correct
14 An earthworm from the sense organs has a) smell b) taste c) hearing d) no special sense organs
15 An earthworm breathes a) in an oxygen-free environment b) atmospheric air c) both options are possible d) there is no breathing
16 The shell of an ordinary pond snail is covered with a layer of a) lime b) a horn-like substance c) chitin d) silicon
17 In the circulatory system of the pond snail there are
a) two-chamber heart and one circle of blood circulation b) two-chamber heart and open circulatory system c) open circulatory system, the function of the heart is performed by two vessels in the front of the body d) one-chamber heart and open circulatory system
18 Gastropods include a) naked slug b) livebearer c) bitinia d) all answers are correct
19 The chitinous cover of arthropods performs the functions of a) protection b) thermoregulation c) gas exchange d) all answers are correct
20 Cancer heart has a) two sections: atrium and ventricle b) three sections: two atria and one ventricle c) one section d) the heart is absent
21 The nervous system in cancer consists of a) supraoesophageal ganglion b) suboesophageal ganglion c) ventral nerve cord d) all answers are correct
22 The abdomen of the cross-spider has a) three segments b) five segments c) non-segmented structure d) none of the answers is correct
23 The process of digestion in a cross-spider:
a) intracavitary b) partially extracavitary c) completely extracavitary d) liquid components are digested outside the digestive system, and solid ones in the stomach of a spider
24 The body of arthropods consists of:
a) head, chest and abdomen b) head and trunk c) cephalothorax and trunk d) head, chest and abdomen; cephalothorax and abdomen.
25 In insects, the number of pairs of motor limbs can be equal to
a) 3 b) 4 c) 5 d) all answers are correct
26 Oxygen to the tissues of insects is supplied by diffusion through
a) the walls of the capillaries b) the walls of the trachea c) the walls of the lung sacs d) enters first into the trachea, then into the capillaries
27 Fish are of the type:
a) chordateless b) semichordate c) chordate
28 The body is covered with bony scales: a) only in cartilaginous fish b) only in bony fish c) in all fish, with rare exceptions
29 Fish eyes are always open because they have:
a) the eyelids have grown together and turned into a transparent shell b) the eyelids are absent c) the eyelids are motionless
30 The spinal cord in fish is located
a) under the spine b) in the spinal canal, which forms the upper arches of the vertebrae c) above the spine
31 The circulatory system in fish
a) closed b) open c) open in cartilage and closed in bone
32 Fish body temperature
a) constant, and does not depend on the temperature of the medium b) variable, but does not depend on the temperature of the medium c) non-constant and depends on the temperature of the medium
33 skin of reptiles
a) has sebaceous glands b) dry (without glands) c) has a small amount of glands that secrete mucus
34 The heart of reptiles
a) three-chamber b) three-chamber, except crocodiles c) four-chamber
35 Fertilization in reptiles
a) external b) internal c) both external and internal
36 Snake is
a) legless lizards b) snakes c) a special group of reptiles
37 In all mammals, the thoracic cavity is separated from the abdominal septum
a) mesentery b) ganglion c) diaphragm d) cuticle
38 The following element does not belong to the skeleton of the lower limb
a) tarsus b) thigh c) lower leg d) radius
39 Animals are characterized by ray symmetry of the body
a) mollusks b) flatworms c) coelenterates d) fish
40 Eliminate the excess
a) scapula b) clavicle c) crow bones d) humerus
41 Bird Science is
a) poultry farming b) ornithology c) cynology d) zoology
42 Keel on the sternum of birds
a) contributes to the dissection of air during flight b) increases the area of ​​attachment of the pectoral muscles c) does not matter as an adaptation to flight
43 What digestive organs arose in birds due to the absence of their jaws and teeth
a) goiter b) glandular part of the stomach c) muscular part of the stomach d) small intestine
44 Mammals spread across the Earth due to the fact that
a) were small in size b) fed their young with milk c) were warm-blooded d) all answers are correct
45 Fabrics first appeared in
a) protozoa b) coelenterates c) flatworms d) annelids
46 Darwin's theory states that all organisms
a) immutable and created by higher powers b) were first created and then evolved naturally c) arose and

1) name the main systematic groups of the type of flatworms and their characteristic distinguishing features, signs, using the example of representatives of each group.