Man as a habitat: flatworms and other helminths. Flatworms meaning of name and habitat Structure of the internal organs of a flatworm

Number of types: about 25 thousand.

Habitat: They live everywhere in humid environments, including the tissues and organs of other animals.

Structure: Flatworms are the first multicellular animals in which, during the course of evolution, bilateral symmetry, three-layer structure, and real organs and tissues appeared.

Bilateral(bilateral) symmetry - this means that an imaginary axis of symmetry can be drawn through the animal’s body, with the right side of the body being a mirror image of the left.

During embryonic development in three-layer animals have three layers of cells: outer - ectoderm, average - mesoderm, internal – endoderm. From each layer certain organs and tissues develop:

the skin (epithelium) and the nervous system are formed from the ectoderm;

from the mesoderm - muscle and connective tissue, reproductive and excretory systems;

from the endoderm - the digestive system.

U flatworms the body is flattened in the dorso-abdominal direction, there is no body cavity, the space between the internal organs is filled with mesoderm cells (parenchyma).

Digestive system includes the mouth, pharynx and blind intestine. Absorption of food and excretion of undigested residues occurs through the mouth. Tapeworms have no digestive system at all. nutrients they are absorbed by the entire surface of the body, being in the intestines of the host.

excretory organs – protonephridia. They consist of thin branching tubules, at one end of which there are flame (flickering) cells star-shaped, immersed in the parenchyma. A bunch of cilia (flickering flame) extends inside these cells, the movement of which resembles the flickering of a flame (hence the name of the cells). Flame cells capture liquid decay products from the parenchyma, and cilia drive them into the tubule. The tubules open on the surface of the body as an excretory pore, through which waste products are removed from the body.

Nervous system ladder type ( orthogon). It is formed by a large head paired nerve ganglion (ganglion) and six nerve trunks extending from it: two on the ventral side, two on the dorsal and two on the sides. The nerve trunks are connected to each other by jumpers. Nerves extend from the ganglion and trunks to organs and skin.

Reproduction and development:

Flatworms are hermaphrodites. Sex cells mature in the sex glands (gonads). A hermaphrodite has both male glands - testes, and female glands - ovaries. Fertilization is internal, usually cross-fertilization, i.e. worms exchange seminal fluid.

CLASS cilia worms

Milk planaria, a small aquatic animal, the adult is ~25 mm long and ~6 mm wide, with a flat, milky white body. At the front end of the body there are two eyes that distinguish light from darkness, as well as a pair of tentacles (chemical sense organs) necessary for searching for food. Planarians move, on the one hand, thanks to the work of the cilia covering their skin, and on the other hand, thanks to the contraction of the muscles of the skin-muscular sac. The space between the muscles and internal organs is filled with parenchyma, in which they meet intermediate cells, responsible for regeneration and asexual reproduction.

Planarians are predators that feed on small animals. The mouth is located on the ventral side, closer to the middle of the body, from it comes a muscular pharynx, from which three branches of a closed intestine extend. Having captured the victim, the planaria sucks out its contents with its throat. Digestion occurs in the intestines under the action of enzymes (intestinal), and intestinal cells are able to capture and digest pieces of food (intracellular digestion). Undigested food remains are removed through the mouth.

Reproduction and development. Ciliated animals are hermaphrodites. Cross fertilization. Fertilized eggs fall into a cocoon, which the worm lays on underwater objects. Development is direct.

CLASS FLUKES

4 - sporocyst; 5 - redia; 6 - cercariae; 7 - adolescary.

CLASS TAPPEWORMS

Bull tapeworm– a tapeworm, reaches a length of 4 to 12 meters. The body includes a head with suckers, a neck and a strobila - a band of segments. The youngest segments are located at the neck, the oldest are sacs filled with eggs, located at the posterior end, where they come off one by one.

Reproduction and development. The bovine tapeworm is a hermaphrodite: each of its segments has one ovary and many testes. Both cross-fertilization and self-fertilization are observed. The posterior segments, filled with mature eggs, open and are excreted with feces. Cattle (intermediate host) can swallow eggs along with grass; in the stomach, microscopic larvae with six hooks emerge from the eggs, which enter the blood through the intestinal wall and are carried throughout the animal’s body and carried into the muscles. Here the six-hooked larva grows and turns into Finn- a bubble containing the head of the tapeworm with its neck. A person can become infected with finches by eating undercooked or undercooked meat from an infected animal. In the human stomach, a head emerges from the finca and attaches to the intestinal wall. New segments bud from the neck - the worm grows. Bovine tapeworm secretes toxic substances that cause intestinal disorders and anemia in humans.

Development pork tapeworm has a similar character, its intermediate host, in addition to pigs and wild boars, can also be humans, then finches develop in its muscles. Development broad tapeworm is accompanied by a change of two intermediate hosts: the first is a crustacean (Cyclops), the second is a fish that has eaten the crustacean. The definitive host may be a person or a predator that eats the infected fish.

New concepts and terms: mesoderm, skin-muscle sac, tegument, hypodermis, reduction, protonephridia (flame cells), orthogon, strobila, ganglion, gonads, hermaphrodite, direct and indirect development, final and intermediate host, miracidium, cercaria, finna, segment, armed and unarmed tapeworm.

Questions for consolidation.

1. Who is called the intermediate host? Final?

6. Why is it dangerous to drink raw water or swim in bodies of water near livestock grazing? Why is it necessary to wash your hands with soap after interacting with animals?

7. For which worms is oxygen harmful?

8. What aromorphoses led to the appearance of the Flatworm type?

Lectures on zoology

Type Roundworms

Response Plan:

· General characteristics Roundworms

Body structure of human roundworm

· Reproduction and development of Ascaris human

· Classification of Roundworms, variety of species

· The importance of Roundworms in nature and human life

Structural features Bilaterally symmetrical - a single symmetry cavity divides the body into left and right halves. Development occurs from three germ layers: ectoderm, endoderm and mesoderm. The third germ layer appears for the first time during evolution and gives rise to the development of parenchymal cells that fill the spaces between organs and the muscular system. Left half Right half

Structural features Body dimensions from 2-3 mm to 20 m. The body is elongated and flattened in the dorsal-ventral direction; has a ribbon-like or leaf-shaped form. It is characterized by the presence of developed organ systems: muscular, digestive (absent in ribbon-like), excretory, nervous and reproductive.

Integument of the body and the muscular system Epithelial and muscle cells are separate formations. The skin-muscle sac consists of a single-layer epithelium (in aquatic forms the epithelium has cilia) and three layers of smooth muscles: circular, longitudinal and oblique). Some representatives also have dorso-abdominal muscles. Movement is provided by muscle contraction (flukes and tapeworms) or by cilia of the integumentary epithelium and muscle contraction (ciliated worms).

The digestive system has two sections - the anterior (mouth, pharynx) and middle (branches of the intestine). The intestine is closed blindly, the hind intestine and anus are absent. Undigested food remains are removed through the mouth. Tapeworms do not have a digestive system (represented by individual digestive cells).

Excretory system Formed by a system of tubules, one end of which begins in the parenchyma with a stellate cell with a bunch of cilia, and the other ends into the excretory duct. The duct is united into one or two common channels, ending with excretory pores.

Nervous system. Sense organs. It consists of suprapharyngeal nerve ganglia (ganglia) and longitudinal nerve trunks running along the body and connected by transverse nerve bridges. Sense organs - touch and chemical sense. Free-living animals have organs of touch and balance.

Liver fluke Liver flukes usually reach 3 cm in length and 1.3 cm in width. Liver flukes of the order Opisthorchis cause opisthorchiasis, early stage symptoms are liver enlargement, allergic reactions and gastrointestinal disorders; symptoms of the late stage - pain radiating to the back, biliary colic, headaches and dizziness, insomnia. Treatment is with anthelmintic, choleretic and enzyme preparations. High frequency electromagnetic radiation is also used.

Development cycle Life cycles different genera differ. In species of the genus Fasciola, development occurs with one intermediate host (a freshwater snail), and infection of the final host occurs when ingested with water or eaten with coastal plants of the dormant stage - Adolescaria. In species of the genera Opisthorchis and Clonorchis, the second intermediate host is freshwater fish, and infection of the definitive host occurs when eating raw fish with invasive stages. In species of the genus Dicrocoelium, land pulmonate snails and ants serve as intermediate hosts, and infection of the final host (usually a herbivore) occurs when an infected ant eats grass.

Bovine tapeworm (tapeworm) Affects cattle and humans, causing teniahrynchiasis. Infestation with bovine tapeworm is particularly common in equatorial Africa, Latin America, the Philippines and some parts Eastern Europe. An adult bull tapeworm consists of more than 1000 segments and reaches 4-40 meters in length. The formation of the reproductive apparatus begins approximately from the 200th segment. The length of mature proglottids is mm, width is 5-7 mm. The scolex (head section) is equipped with 4 suckers without hooks (therefore unarmed). The lifespan of a bovine tapeworm in the human intestine, if no deworming measures are taken, is years. The tapeworm produces ~600 million eggs per year, and ~11 billion over its lifetime.

Development cycle Segments containing eggs are released from the human intestine (the main host). Together with the grass, they enter the stomach of the cow (intermediate host). Six-hooked larvae emerge from the eggs and penetrate into blood vessels intestines and then into the muscles. In the muscles, the larva turns into finn (a vesicle with the head of the tapeworm inside). When a person consumes poorly processed fino meat, the head of the tapeworm attaches to the intestinal wall and begins to produce segments.

Structural features Bilaterally symmetrical. Sizes range from a few micrometers (soil) to several meters (sperm whale nematode). They have a non-segmented body with a dense cuticle. The ciliary cover is partially or completely reduced. The body is filiform, fusiform, unsegmented, round in cross section.

The digestive system is formed by the foregut, middle and hindgut. The foregut is differentiated into sections: the mouth with cuticular lips, the pharynx and the esophagus. The midgut and hindgut are not divided into sections. The digestive tract ends with the anus.

Excretory system Represented by 1-2 skin glands (modified protonephridia). These are large cells from which two channels extend on the sides of the cell. At the posterior end of the body, the canals end blindly, and at the front they open into the external environment with an excretory pore.

Nervous system. Sense organs Nervous system of the ladder type. It is represented by the head nerve ganglia (ganglia), the peripharyngeal nerve ring and several nerve trunks (dorsal and ventral), and median transverse bridges. The sense organs are represented by the organs of touch and chemical sense. Marine forms have photosensitive receptors. Diagram of the roundworm nervous system: 1 - oral papillae with tactile endings and the nerves innervating them, 2 - peripharyngeal nerve ring, 3 - lateral cephalic ganglia, 4 - abdominal nerve trunk, 5 - lateral nerve trunks, 6 - ring nerves, 7 - posterior ganglion , 8 - sensitive papillae with corresponding nerves, 9 - anus, 10 - dorsal nerve trunk

Human roundworm Roundworms are large roundworms, their length can reach 40 centimeters. Most often they affect the gastrointestinal tract and cause ascariasis. The favorite habitat of adults is the small intestine. Roundworms are bisexual worms. Female roundworms can produce more than 200 thousand eggs per day. Fertilized eggs from the human intestine enter the soil. Larvae develop in them. Infection occurs by drinking water from open reservoirs, eating poorly washed vegetables and fruits that contain eggs with larvae. In the human body, the larva migrates: once in the intestine, it drills through its walls and enters the bloodstream.

Structural features Bilateral symmetry of the body. Dimensions from 0.5 mm to 3 m. The body is divided into the head lobe, trunk and anus. Polychaetes have a separate head with eyes, tentacles and antennae. The body is segmented (external and internal segmentation). The body contains from 5 to 800 identical ring-shaped segments. The segments have the same external and internal structure(metamerism) and perform similar functions. The metameric structure determines a high degree of regeneration.

Body integument and muscular system The body wall is formed by a skin-muscular sac, consisting of a single-layer epithelium covered with a thin cuticle, two layers of smooth muscle (external circular and internal longitudinal) and single-layer epithelium of the secondary body cavity. When the circular muscles contract, the body of the worm becomes long and thin; when the longitudinal muscles contract, it shortens and thickens.

Body cavity Secondary - coelom (has epithelial lining). In most, the body cavity is divided by transverse partitions corresponding to body segments. Cavity fluid is a hydroskeleton and internal environment; it is involved in the transport of metabolic products, nutrients and reproductive products.

The digestive system consists of three sections: anterior (mouth, muscular pharynx, esophagus, crop), middle (tubular stomach, midgut) and posterior (hindgut, anus). The glands of the esophagus and midgut secrete enzymes to digest food. Absorption occurs in the midgut.

Circulatory system Closed. There are two vessels: dorsal and abdominal, connected in each segment by ring vessels. Blood moves through the dorsal vessel from the rear end of the body to the front, and through the abdominal vessel from front to back. The movement of blood is carried out thanks to the rhythmic contractions of the walls of the spinal vessel and the annular vessels (“heart”) in the pharynx. Many people have red blood.

Excretory system of Metanefidial type. Metanephridia look like tubes with funnels, two in each segment. A funnel surrounded by cilia and convoluted tubules are located in one segment, and a short tubule opening outward with an opening, the excretory pore, is in the adjacent segment.

Nervous system. Sense organs. It is represented by suprapharyngeal and subpharyngeal nerve ganglia (ganglia), which are connected into a peripharyngeal nerve ring and an abdominal nerve chain, consisting of paired nerve ganglia in each segment, connected by longitudinal and transverse nerve trunks. Polychaetes have organs of balance and vision (2-4 eyes). Most have only olfactory, tactile and light-sensitive cells.

Reproduction and development Soil and freshwater forms are mainly hermaphoditic. The gonads develop only in certain segments. Insemination is internal. Type of development - direct. Asexual reproduction is carried out by budding and fragmentation (due to regeneration). Marine representatives are dioecious. Development with metamorphosis, larva-trochophore.

All worms can be divided into three types (flat, annelid, round), each of which has its own characteristic features. This type refers to invertebrate animals that lack a body cavity and have bilateral symmetry.

The main signs of the type of flatworms

• digestive;
• nervous;
• sexual;
• excretory

This type has several systems and even the rudiments of organs

Circulatory system

Not present, but the function of blood is performed by the parenchyma, consisting of connective cells. It is she who transports nutrients in the body.

Digestive system

Quite simplified, consists of a pharynx and intestines.

The pharynx is powerful and can:

• suck in;
• twist and envelop its victim.

The intestine consists of two sections - anterior and middle, most often branched. It has a closed structure, so that all undigested waste exits through the mouth. The mouth opening is located closer to the middle of the worm's body.

Free worms are mostly predators and they even have a peculiar device for capturing prey. This system is not observed in all classes; more primitive worms do not have it. For example, tapeworms feed on the entire surface.

Excretory system

The excretory system is quite large and consists of many tubules that unite and lead to excretory pores.

The parenchyma contains special cells, which drive harmful substances into the tubules. For humans, these excretory products are very dangerous and toxic, along with poison.

Muscular system

It is represented by muscle fibers covered with epithelium. By contracting these fibers, the worms can move.

Nervous system

At the top of the worm there are two head nodes, from which two nerve trunks descend. Longitudinal nerve trunks completely penetrate the body of the worm and are connected to each other by transverse nerves, similar to a ladder.

With the help of skin cilia, some worms can:

• feel the temperature;
• other external stimuli.

And among free worms there are representatives who have developed organs of vision (pigments that react to light) and balance.

Variety of species

There are three classes of this type:

1. Flukes.
2. Tape.
3. Eyelash worms.

Flukes: representatives of the class and characteristics

Class representatives:

General characteristics of the fluke class:

Tapeworms: representatives of the class and characteristics

General characteristics of the class tapeworms:

Class representatives:

• found in standing water - ponds, ditches, very active. Covered with cilia, it uses them to move on the water surface and attach to the bottom. Length is about 35 cm. The digestive system is developed, feeding mainly on crustaceans and small invertebrates. Reproduction can be sexual or asexual (divided in half, and then each half is completed). Wide habitat, found almost everywhere.
• Ehrenberg's mesostomy- a flat leaf-shaped body, slightly convex, transparent and colorless, in old worms it is brown. Unlike planaria, the intestine is straight and not branched. They live attached to aquatic plants. Mesostoma is predatory, hunting crustaceans, worms, insects and even freshwater hydras. Able to tolerate drying out of water bodies, live in flooded meadows and puddles, and after they dry out, the mesostome eggs remain capable of development.
• Land worm rhynchodemus- a soil worm, lives in damp places, most often under stones. Habitat Europe and North America. It can reach 12 mm, the color is brown with red longitudinal spots. The cilia are preserved on the ventral side of the body; it moves by contracting muscles. Predator, eats insects.

General characteristics of eyelash worms:

Brief description

Habitat and appearance	Dimensions 10-15 mm, leaf-shaped, live in ponds and low-flowing reservoirs
Body cover and skin-muscle bag	The body is covered with single-layer (ciliated) epithelium. The superficial muscle layer is circular, the inner layer is longitudinal and diagonal. There are dorso-abdominal muscles
Body cavity	There is no body cavity. Inside there is spongy tissue - parenchyma
Digestive system	Consists of the anterior section (pharynx) and the middle section, which looks like highly branched trunks ending blindly
excretorysystem	Protonephridia
Nervous system	The cerebral ganglion and the nerve trunks coming from it
Sense organs	Tactile cells. One or more pairs of eyes. Some species have balance organs
Respiratory organs	No. Oxygen is supplied through the entire surface of the body
Reproduction	Hermaphrodites. Fertilization is internal, but cross-fertilization - two individuals are needed

Typical representatives of eyelash worms are planarians(Fig. 1).

Rice. 1.Morphology of flatworms using the example of milk planaria. A - appearance of planaria; B, C - internal organs (diagrams); D - part of a cross section through the body of a milk planaria; D - terminal cell of the protonephridial excretory system: 1 - oral opening; 2 - pharynx; 3 - intestines; 4 - protonephridia; 5 - left lateral nerve trunk; 6 - head nerve ganglion; 7 - peephole; 8 - ciliated epithelium; 9 - circular muscles; 10 - oblique muscles; 11 - longitudinal muscles; 12 - dorsoventral muscles; 13 - parenchyma cells; 14 - cells forming rhabdites; 15 - rhabdites; 16 - unicellular gland; 17 - a bunch of eyelashes (flickering flame); 18 - cell nucleus

General characteristics

Appearance and covers . The body of ciliated worms is elongated, leaf-shaped. Dimensions vary from a few millimeters to several centimeters. The body is colorless or white. Most often, eyelash worms are colored with grains of different colors pigment, embedded in the skin.

Body covered single-layer ciliated epithelium. In the integument there are skin glands, scattered throughout the body or collected in complexes. Of interest are the types of skin glands - rhabditis cells, which contain light-refracting rods Rhabdites. They lie perpendicular to the surface of the body. When an animal is irritated, the rhabdites are thrown out and swell greatly. As a result, mucus forms on the surface of the worm, possibly playing a protective role.

Skin-muscle bag . Under the epithelium is basement membrane, which serves to give the body a certain shape and to attach muscles. The combination of muscles and epithelium forms a single complex - skin-muscle sac. The muscular system consists of several layers smooth muscle fibers. Most superficially located circular muscles, somewhat deeper - longitudinal and the deepest - diagonal muscle fibers. In addition to the listed types of muscle fibers, ciliary worms are characterized by dorso-abdominal, or dorsoventral, muscles. These are bundles of fibers running from the dorsal side of the body to the ventral side.

The movement is carried out due to the beating of the cilia (in small forms) or the contraction of the skin-muscular sac (in large representatives).

Clearly expressed body cavities ciliated worms do not. All spaces between organs are filled parenchyma- loose connective tissue. The small spaces between the parenchyma cells are filled with aqueous fluid, which allows the transfer of products from the intestines to the internal organs and the transfer of metabolic products to the excretory system. In addition, parenchyma can be considered as supporting tissue.

Digestive system eyelash worms blind. Mouth also serves for swallowing food, and for throwing out undigested food debris. The mouth is usually located on the ventral side of the body and leads into throat. In some large ciliated worms, such as the freshwater planaria, the mouth opening opens into pharyngeal pocket, in which it is located muscular throat, capable of stretching and protruding out through the mouth. Midgut in small forms of ciliated worms it is canals branching in all directions, and in large forms the intestine is represented three branches: one front, going to the front end of the body, and two rear, running along the sides to the rear end of the body.

Main feature nervous system ciliated worms compared to coelenterates is concentration of nerve elements at the anterior end of the body with the formation of a double node - the cerebral ganglion which becomes coordinating center of the whole body. They depart from the ganglion longitudinal nerve trunks, connected by transverse ring jumpers.

Sense organs in ciliated worms they are relatively well developed. Organ of touch All skin serves. In some species, the function of touch is performed by small paired tentacles at the anterior end of the body. Balance sense organs represented by closed sacs - statocysts, with hearing stones inside. Organs of vision are almost always available. There may be one pair of eyes or more.

Excretory system for the first time appears as separate system. She is presented two or several channels, each of which one end opens outwards, A the other is heavily branched, forming a network of channels various diameters. The thinnest tubules or capillaries at their ends are closed by special cells - star-shaped(see Fig. 1, D). From these cells, they extend into the lumen of the tubules bunches of eyelashes. Thanks to their constant work, there is no stagnation of fluid in the body of the worm; it enters the tubules and is subsequently excreted. The excretory system in the form of branched canals closed at the ends by stellate cells is called protonephridia.

Reproductive system quite diverse in structure. It can be noted that, in comparison with coelenterates, ciliated worms special excretory ducts appear For

excretion of germ cells. Eyelash worms hermaphrodites. Fertilization - internal.

Reproduction. In most cases sexually. Most worms direct development, but in some marine species development occurs with metamorphosis. However, some eyelash worms can reproduce and asexually through transverse division. In this case, in each half of the body there is regeneration missing organs.

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

2. What kind of life do representatives of different groups of flatworms lead? How are the structural features of worms related to the image life. And the habitat?

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

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

.Name the main classes of the type Flatworms and their characteristic distinctive features using the example of representatives of each class. 2.What kind of life do they lead?

representatives of different classes? How are the structural features of worms related to their lifestyle and habitat? 3. Using the example of the structural features of flat, round and annelid worms, list the signs of increased complexity of organization compared to coelenterates. 4.What diseases are caused by flatworms? What is their prevention? 5.What structural features and lifestyle are characteristic of representatives of the Roundworm type? 6.Why did annelids get this name? What is characteristic of the structure of each segment? 7. Based on what characteristics do annelids belong to more complexly organized animals than those previously studied?

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

12 The body cavity of the roundworm a) filled with connective tissue b) filled with liquid c) filled with air d) absent
13 In every segment of the body earthworm repeated a) nerve ganglia b) excretory tubes c) annular blood vessels d) all answers are correct
14 An earthworm has a) sense of 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 the common pond snail is covered with a layer of a) lime b) 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 an open circulatory system c) an open circulatory system, the function of the heart is performed by two vessels in the front part of the body d) a single-chamber heart and an 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 The cancer heart has a) two sections: an atrium and a ventricle b) three sections: two atria and one ventricle c) one section d) there is no heart
21 The nervous system in cancer consists of a) suprapharyngeal ganglion b) subpharyngeal 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 the cross spider:
a) intracavitary b) partially extracavitary c) completely extracavitary d) liquid components are digested outside the digestive system, and solid ones in the spider’s stomach
24 The body of arthropods consists of:
a) head, chest and abdomen b) head and torso c) cephalothorax and torso 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 reaches insect tissues through diffusion through
a) walls of capillaries b) walls of trachea c) walls of pulmonary sacs d) enters first into the trachea, then into the capillaries
27 Pisces belong to the type:
a) achordates b) hemichordates c) chordates
28 The body is covered with bone scales: a) only in cartilaginous fish b) only in bony fish c) in all fish, with rare exceptions
29 Fish's eyes are always open because they:
a) the eyelids have grown together and turned into a transparent membrane 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 Circulatory system in fish
a) closed b) open c) open in cartilaginous 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) not constant and depends on the temperature of the medium
33 skin in reptiles
a) has sebaceous glands b) dry (without glands) c) has a small number of glands that secrete mucus
34 The heart of reptiles
a) three-chamber b) three-chamber, except for crocodiles c) four-chamber
35 Fertilization in reptiles
a) external b) internal c) both external and internal
36 Snakes
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) anthema b) ganglion c) diaphragm d) cuticle
38 The following element does not belong to the skeleton of the lower limb
a) tarsus b) femur c) tibia d) radius
39 Animals are characterized by radial symmetry of the body
a) mollusks b) flatworms c) coelenterates d) fish
40 Eliminate unnecessary things
a) scapula b) clavicle c) crow bones d) humerus
41 Bird Science is
a) poultry b) ornithology c) cynology d) zoology
42 Keel on the sternum of birds
a) promotes cutting through 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 their lack of jaws and teeth
a) goiter b) glandular section of the stomach c) muscular section 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) unchangeable 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 distinctive features using the example of representatives of each group.