Type Flatworms. Classes: Ciliated, Flukes, Banded. Type flatworms

Basic classes, structure, nutrition and reproduction. Radial symmetry in the organization of coelenterates in connection with their lifestyle. Metagenesis in hydroid and scyphoid polyps. The importance of movement in the origin of the muscular and nervous systems with sensory organs in jellyfish. Coral polyps, distribution and biological significance. Ctenophores are classified as a separate type). Phylogeny of coelenterates.

REFERENCES: 2, p. 66-84.

Self-test questions

1. Describe coelenterates as multicellular animals.

Why are animals of this type called coelenterates?

What classes is the type of coelenterates divided into?

Lifestyle of coelenterates (feeding, reproduction, development, ability to regenerate, etc.).

The importance of coelenterates in the general evolution of many cellular animals.

Flatworms

General characteristics and division into main classes.

Ciliated worms Morphology and phylogeny of ciliated worms. The origin of bilateral (bilateral) symmetry in the organization of worms and its significance in the evolution of animals.

Flukes (trematodes). (Monogeneas are classified as a separate type).

Reproduction, development with alternation of generations and change of hosts. The relationship between ontogeny and phylogeny in flukes. The main representatives of trematodes, their development cycles and the diseases they cause in domestic animals and humans. Fighting flukes.

Tapeworms (cestodes). Their structure, reproduction and development (ontogenesis), fertility. Tapeworms and tapeworms, their most important representatives and development cycles. Tapeworms as causative agents of invasive diseases in animals and humans. Fight against cestodes. The significance of the works of K. I. Scriabin

Roundworms

General characteristics and division into main classes: nematodes.

Annelids

Ringworms are like higher worms. Metamerism as the main feature of annelid organization. The origin of the secondary body cavity, the circulatory system and their significance in evolution. Development and structure of the ganglion nervous system of annelids. Main classes annelids. Polychaetes. Structural features and lifestyle of polychaetes (polychaetes). Their importance in fish nutrition. Oligochaetes (oligochaetes). The role of annelids in soil formation and its fertility.

Phylogeny of annelids and their significance in the evolution of invertebrates. The role of Russian scientists in the history of the study of annelids. (I. I. Mechnikov, A. O. Kovalevsky, P. P. Ivanov)

REFERENCES: 2, p. 327-351.

Self-test questions

Classification of worms into separate types (flat, round and annelid worms).

List the main features of the differences (according to organ systems) between the types of flat, round and annelid worms.

Origin and connection various types worms with other groups of invertebrates (flat worms with coelenterates, the relationship of annelids with arthropods, etc.).

Give general characteristics and classification of flatworms.

Describe the structure, reproduction and development of flukes (Fasciola hepatica), tapeworms (wide tapeworm, pork and bovine tapeworms) and echinococcus.

Give a general description and classification of roundworms.

Describe the structure, nutrition, reproduction and development of roundworms using the example of the horse roundworm.

Give a general description and classification of annelids.

Describe the structure and biology of ringlets using the example of an earthworm.

Basic information: planaria are free-moving worm-like creatures. Class: animals. The worm is a multicellular organism with a flat body. Systematic position: included in the class of ciliated worms - primitive invertebrates, which are characterized by bipolar symmetry of the body.

Bilateral symmetry allows worms to live both in water and on land. If planaria had a different body structure (radical), then it could fully exist only in an aquatic environment.

The family planariidae has 12 genera, white planaria belongs to planaria (there are 25 more species of invertebrates in this category).

Habitat and lifestyle

Habitat: marine and terrestrial. Common habitat: freshwater reservoir. Worms can be found under pebbles at the very bottom. White planarians can live in different conditions. Sometimes they end up in aquariums along with untreated soil, snails and small fish (live food). Flatworms can crawl, so they move freely along the surface of the bottom or land.

The freshwater milky white planaria constantly consumes protein because it needs it to maintain normal life functions. It feeds on caviar, small fish and crustaceans.

This worm-like predator makes the process of obtaining food easier for itself in every possible way. The creature releases threads into the water, which swell due to exposure to the liquid. With their help, the worm captures and, if necessary, holds prey.

External structure of planaria (planarii)

This worm-like animal usually does not exceed 2-2.5 cm in length. The milk planaria, like many representatives of its species, has a pointed body, similar in shape to an oblong leaf. The thickness of its body is from 2 to 5 mm. At the base of the extended part of the body there are two eyes. At the front end there are also tentacles resembling ears.

Planaria has an ideal white-milky, more often white, color. The body cover is strewn with cilia, but they can only be clearly seen in close-up photos.

The worm has a transverse cut that divides its body into two (unequal) parts. In this case, one side of the body is mirror image the other due to bipolar symmetry.

What systems and organs does a worm have?

The milky white planaria has characteristics that set it apart from the group of flatworms. This creature has additional tissue (mesoderm) located between the ento and ectoderm. This factor indicates the development of a multicellular organism.

Worm sensory organs:

• vision;
• touch (due to the tentacles on the front of the body);
• equilibrium;
• chemical feelings.

Digestive system

This creature has an unusual structure of the mouth opening - it is located in the center of the abdomen and leads into a cavity with a retractable pharynx. When a worm eats prey, it presses tightly and swallows it with the help of a “catching apparatus”. Subsequently, food is distributed through 2 branches of the blind intestine: anterior and posterior. At the same time, the posterior part of the intestine is also divided into 3 branches.

Thus, the digestive system of the worm includes: the mouth, the hindgut and the foregut, connected to the pharynx.

Nervous system

The worm has a paired brain, from which two chains of nerves extend, connected by jumpers. The nerve trunks form a thickening (knot) in the front of the body. Nervous system planaria differs in that the cells are not scattered throughout the body, as, for example, in hydra, but are collected in 2 compactions.

Reproductive system

Planaria is a hermaphroditic (bisexual) creature, since male and female reproductive cells are formed in its body. In the front part of the body of the worm there are ovaries in which eggs develop. The testes are located along the body, presented in the form of small bubbles. The testes contain sperm.

The eggs develop in the inner part of a kind of mucous cocoon. The worm lays several eggs at once, protected by a dense shell (cocoon) from exposure environment. The worm-like animal, as a rule, attaches its future offspring to plants located at the bottom of the reservoir.

The internal reproductive organs of the worm are the ovaries and testes.

Excretory system

This system is presented in the same way as in all flatworms. The main organs responsible for the release of breakdown products are branched tubules, which in large quantities penetrate the body of the animal. The worm also has excretory pores and protonephridia.

How does he move? The skin-muscle sac is responsible for movement - a muscle layer located under the epithelium and tightly adjacent to it. It consists of longitudinal, circular and spinal muscles. The movement and change in shape of the worm-like animal is carried out through contraction of the skin-muscular sac.

Development cycle

The development of the white planaria can be considered unique, since this animal, unlike its closest brothers, does not require definitive or intermediate hosts. The development scheme consists of only 2 stages: first an egg is formed, and then a small worm emerges from it. Over time, the creature grows and grows into an adult.

How do white planaria reproduce?

Since planaria is a bisexual animal, its reproduction can occur in 2 ways:

1. Asexual. The worm's body is divided in half. Subsequently, an adult individual grows from each particle.
2. Sexual. To carry out this method of reproduction, 2 individuals must touch their abdomens for a few seconds (at this moment fertilization occurs). After contact, the female reproductive system of one worm contains male cells of the other. Eggs that have been fertilized form zygotes and begin to accumulate the necessary substances. Final stage: formation of a protective shell and release into external environment. After 2-3 weeks, small worms emerge from the cocoons.

This worm is characterized by pronounced and rapid regeneration. It is for this reason that the creature is highly durable.

The white planaria is characterized by nocturnal and evening activity. These animals move very smoothly in the water due to the constant movement of cilia on the body.

Why flatworms got that name?

Flatworms got their name because of their specific body shape.

Which flatworms are dangerous to humans?

Bovine tapeworm, echinococcus, and pork tapeworm are dangerous for humans.

Questions

1. What are the differences between flatworms and coelenterates?

Flatworms, unlike coelenterates, have bilateral body symmetry. Their body consists of several layers. Organs appeared.

2. What structural and life features allow us to divide the type of flatworms into classes?

The type of flatworms can be divided into classes due to the features of the external structure of the body, specific features of the internal structure, different development cycles and habitats.

3. Why do tapeworms lack digestive organs?

The following measures serve to prevent helminthiasis:

Maintaining personal hygiene (washing hands before eating)

Using only quality food products

Sufficient heat treatment of meat.

5. The larvae of flatworms are able to move independently. What does it matter?

The mobility of larvae contributes quick search intermediate host.

Tasks

Using various sources of information, prepare a report on modern achievements in helminthology.

Helminthology

Applied problems cover: a detailed study of all pathomorphological and pathophysiological processes associated with infection of humans, beneficial animals and plants by various helminths, in order to find the most effective methods diagnosis, prevention and treatment of diseases caused by them, Main sections of Helminthology: general Helminthology (study of Helminthology, fauna, morphology, taxonomy, biological cycles and physiology of helminths); medical Helminthology (human helminth infections, measures to combat them); veterinary Helminthology (helminthiases of domestic and game animals, measures to combat them); agronomic helminthology, or phytohelminthology (study of the influence of helminths on plants, development of measures to combat phytohelminths).

Question 1 . List the differences between flatworms and coelenterates.

Firstly, unlike coelenterates, which have radial symmetry, flatworms have bilateral symmetry.

Secondly, coelenterates are two-layered animals that do not have internal organs. The body of flatworms consists of many layers of cells. Inside the skin-muscle sac are internal organs, united into organ systems: digestive, excretory, nervous and reproductive. The space between these organs is filled with cells, so there is no internal cavity.

Question 2. What structural features and lifestyle allow us to divide the type of flatworms into classes?

Question 3. Why do tapeworms lack digestive organs?

Question 1 ■ How do roundworms differ from flatworms?

Unlike flatworms, which have a dorsoventrally flattened body, all roundworms have a body that is round in cross section.

Flatworms do not have an internal cavity, the space between the skin-muscular sac and internal organs filled with cells, and in roundworms these cells have disintegrated and an internal cavity has formed, which is filled with liquid under pressure and ensuring the constancy of the body shape.

The muscles of roundworms are located only along the body in four strands. These worms can only bend, but not stretch or wriggle like flatworms, which have a skin-muscular sac consisting of bundles of muscles that provide movement in all directions.

Roundworms are usually heterosexual, and most flatworms are hermaphrodites.

Unlike flatworms, many of whose representatives are characterized by the presence of cilia, representatives of roundworms are completely devoid of ciliated formations.

Question 2. What are the similarities between flatworms and roundworms?

^ 9. Type Annelids, or Ringworms. Class Polychaetes

Question 1 What are the differences in the structure of roundworms and annelids?

In annelids, the body consists of rings - segments, and roundworms have a non-segmented body structure.

The movement of roundworms is carried out thanks to longitudinal bundles of muscles,

and in annular fish it is provided by bundles of circular and longitudinal muscles. Some annelids have specialized locomotion organs called parapodia. Roundworms do not have special locomotion organs.

Roundworms do not have a circulatory system, the functions of which are performed exclusively by intracavitary fluid, while most annelids have a closed circulatory system.

Among annelids there are dioecious and hermaphrodites; They can reproduce asexually and sexually. Roundworms are often dioecious; They are incapable of asexual reproduction.

Question 2. Why did Polychaetes get this name?

In polychaete ringlets, each body segment bears a pair of primitive legs - parapodia. Each parapodia contains tufts of setae. For these numerous setae located on the parapodia, the class Polychaete ringlets, or Polychaetes, got its name. Parapodia with bristles allow them to move well in the water and along the bottom surface.
Question 3. What is the significance of polychaetes in nature?

^ 10. Classes of rings. Oligochaetes, or Oligochaetes, and Leeches

Question 1 What features of annelids allowed them to colonize most planets?

Annelids acquired a number of features in structure and physiology that allowed them to survive in various conditions environment.

Firstly, annelids developed specialized locomotion organs, which gave them relative independence from physical properties habitats. These are parapodia in polychaetes, which enable movement in the water column and along the bottom, and setae in oligochaetes, which help with movement in the soil.

Secondly, the nervous system and sensory organs have achieved significant development in annelids. Which allows you to increase your active lifestyle.

Thirdly, annelids have mechanisms that make it possible to tolerate unfavorable environmental conditions. For example, soil species of oligochaetes are characterized by diapause (see answer to question 2), and some types of leeches are capable of falling into suspended animation (see answer to question 2).

Question 2. What adaptations do annelids have to cope with unfavorable conditions? How does this happen?

In soil species, in the event of unfavorable conditions, the worms crawl to depth, curl up into a ball and, secreting mucus, form a protective capsule, they experience diapause - a condition in which the processes of metabolism, growth and development slow down.

Leeches that live in cold waters can enter into anabiosis - a state of the body in which life processes are so slow that all visible manifestations of life are absent.
Question 3. What allows scientists to classify polychaetes, oligochaetes and leeches into the same phylum?

All these animals have a number of characteristics that characterize them as belonging to the same type - annelids. All of them are multicellular animals with an elongated worm-like body, which has bilateral symmetry and consists of individual rings (segmented structure). The internal cavity of these worms is divided by partitions into separate segments, inside of which there is liquid.

^ 11. Type Molluscs

Question 1 . What is the function of the shell in mollusks?

The main function of a mollusk shell is supporting, i.e. the shell plays the role of an exoskeleton. Mollusks do not have a skin-muscle sac; separate bundles of muscles are attached to the shell. In addition, the sink performs the function of passive protection.

Question 2. What does the unequal development of sensory organs in different mollusks indicate?

The unequal development of sensory organs in different mollusks indicates differences in

the lifestyle of these animals. Sense organs are most developed in mollusks leading active image life, especially in predators (cephalopods).

Question 3 What are the structural features of mollusks compared to annelids?

Unlike annelids, the body of mollusks does not have a segmental structure, but in most, a head, torso and leg can be distinguished.

The body of most species of mollusks is completely or partially covered with a shell, but annelids do not have a shell. The shell plays the role of an exoskeleton in mollusks. And in annelids, the supporting function is performed by an internal cavity filled with liquid. The movement of mollusks is ensured by individual muscles, and in annelids - by a skin-muscular sac.

Circulatory system in mollusks (except for cephalopods) it is open, whereas in most annelids it is closed.

Mollusks, unlike annelids, have special organs such as kidneys and digestive and salivary glands.

The nervous system of mollusks is represented by individual ganglia interconnected by nerves, while annelids have an abdominal nerve cord with nerve branches in each segment.
^ 12. Classes of mollusks: Gastropods, Bivalves, Cephalopods

Question 1 Explain how mollusks are adapted to their environment.

Among the mollusks there are inhabitants of the aquatic and land-air environment.

Many both terrestrial and aquatic mollusks have a shell, which in both of them acts as a passive defense.

The most important adaptation to the terrestrial lifestyle of land mollusks is lung breathing.

Aquatic mollusks are adapted to obtain oxygen from water - they breathe through gills or the surface of the mantle.

Cephalopods have developed a special - reactive - method of movement, which is very effective in the aquatic environment.

Question 2. What are the similarities and differences between gastropods and bivalves?

Gastropods and bivalves are multicellular animals whose bodies do not have a segmental structure. The body of most species of these classes of mollusks is completely or partially covered with a shell. In gastropods the shell is solid, often asymmetrical and twisted, in bivalves it consists of two valves.

The head, trunk and leg can only be distinguished in gastropods; in bivalves the head is absent.

Gastropods have well-developed sense organs - touch, chemical sense, balance and vision. In bivalves, the sense organs are poorly developed.

Bivalves are exclusively aquatic animals, while among gastropods there are inhabitants of both aquatic and terrestrial-air environments.

Question 3. List ways to protect mollusks known to you from enemies.

Some gastropods and almost all bivalves are capable of fully or partially hiding in a shell - this is a passive method of defense.

When escaping from persecution, squids can fly several tens of meters above the water.

Some mollusks, for example cuttlefish, octopuses, in case of danger, are capable of changing color or throwing out an ink substance produced in a special organ - the ink sac.

ke. Before using this remedy, the mollusk first darkens, then releases ink in a film shaped like its body. The pursuer grabs an ink “bomb” - the film breaks, the ink stains a large volume of water and paralyzes the enemy’s sense of smell. This saves the life of the mollusk: after releasing the ink, it quickly turns pale and swims away almost invisible.

Question 4. What allows cephalopods to move quickly in water and escape from enemies?

The rapid movement of cephalopods in water is ensured by the pulsating ejection of water from the mantle cavity (jet movement). This method of movement allows you to develop significant swimming speeds: squids - up to 40 km/h, octopuses - up to 15 km/h.
^ 13. Type Echinodermata. Classes: Sea lilies, Starfish, Sea urchins. Holothurians, Brittle stars

Question 1 Why did echinoderms manage to populate all seas and oceans in deep and shallow waters?

Firstly, echinoderms are practically omnivorous animals - they feed on what they find in the bottom layers.

Secondly, they have a unique water-vascular system. Considering that sea water fills the channels inside the body of an echinoderm almost by gravity, the pressure inside it corresponds to the pressure at the depth at which it is located. Therefore, the depth of habitat for echinoderms has practically no significance.

Thirdly, echinoderms are little sensitive to water salinity, especially holothurians, which live in the seas at various depths.

Question 2. By what characteristics did the phylum of echinoderms and its classes get their names?

All echinoderms have a calcareous skeleton, often with numerous needles, projections, spines, etc., hence the name of the type - Echinoderms.

Class Sea lilies. Among them there are sessile and free-swimming forms. The body of sea lilies looks like a flower. It looks like a cup (often on a calcareous stalk), in the center of which the mouth is located. Usually five tentacles originate from the calyx, which bifurcate and can further branch.

Starfish class. Their flattened body consists of central disk and from five to fifty rays. The mouth opening is on the underside of the body. Starfish are predators that eat sedentary animals, mainly bivalves.

Class Sea urchins. These animals are very similar in appearance famous hedgehogs. They have a spherical body with a hard shell covered with movable needles that perform a protective function and take part in movement. The mouth, like that of starfish, is located on the underside of the body and is equipped with a gnawing apparatus.

Class Holothuria, or Sea Cucumbers. The body of these animals, the length of which is different types ranges from a few millimeters to 2 meters, has a bag-like or worm-like shape, similar to a cucumber. The mouth is at the front end.

Ophiura class. The name "brittle star" literally means "snaketail". Animals belonging to this class are similar in appearance to starfish. They have the same flat body, consisting of a central disk and rays. But these rays are sharply separated from the central disk, and in some forms they really look like snake tails attached to the disk.
Question 3. What is the significance of echinoderms?

Echinoderms are part of natural communities. Most often, they feed on various dead animals that sink to the bottom, and silt, i.e. they are orderlies. This primarily applies to sea ​​urchins and the stars. Starfish also eat sedentary and sessile bottom animals.

Sea lilies and brittle stars feed on small planktonic organisms, i.e. they act as filter feeders.

Sea urchins and sea cucumbers, sea cucumbers, are edible. They are caught and even specially bred on marine plantations for sale.

Some sea ​​stars destroy edible shellfish, thereby causing significant harm to their fisheries.

2.What structural features and lifestyle allow us to divide the type of flatworms into classes.
3.Why do tapeworms lack digestive organs?

1. In contrast to the radial symmetry of coelenterates, such symmetry is called bilateral. (Bilateral or bilateral symmetry first appears in this type of animal).
Unlike coelenterates, the nervous system of flatworms is not diffuse. It consists of the head nerve ganglion and several longitudinal nerve trunks, of which the most developed are the 2 lateral or abdominal trunks.


2. The body of Coelenterates looks like a sac open at one end, surrounded by tentacles. The body cavity is gastric (represented by a blindly closed primary intestine).


5. A variety of types of gastrulation - the formation of a two-layer embryo (gastrula).

Character traits coelenterates:
1. The ectoderm contains various types of stinging cells.
2. The body of Coelenterates looks like a sac open at one end, surrounded by tentacles. The body cavity is gastric (represented by a blindly closed primary intestine).
3. The respiratory, circulatory and excretory systems are absent.
4. There are no permanent sex glands (gonads); their functions are performed by single (interstitial) cells, from which both eggs and sperm are formed.
5. A variety of types of gastrulation - the formation of a two-layer embryo (gastrula).
6. Metagenesis is widespread - alternation of sexual and asexual generations. The sexual generation is usually represented by the jellyfish stage, and the asexual generation by the polyp stage.

Characteristic features of the Flatworm type:
1. The integument of the body and the underlying layers of muscles form a musculocutaneous sac.
2. The spaces between organs are filled with connective tissue parenchyma.
3. The digestive system consists of two sections: the foregut and the blindly closed midgut.
4. The nervous system is of the ladder (orthogonal) type.
5. Protonephridial type excretory system.
6. Hermaphroditism. Fertilization is internal.

In contrast to the radial symmetry of coelenterates, this symmetry is called bilateral. (Bilateral or bilateral symmetry first appears in this type of animal).
Also, unlike coelenterates, in the process of development from a fertilized egg, they form not two, but three layers of cells: the outer - ectoderm, the inner - endoderm, and the intermediate - mesoderm, from which various organ systems subsequently develop.
Unlike coelenterates, the nervous system of flatworms is not diffuse. It consists of the head nerve ganglion and several longitudinal nerve trunks, of which the most developed are the 2 lateral or abdominal trunks.

Answer