7. Type of flatworms

1. Fill out a summary table in your notebooks while studying representatives of all types of worms

2. Is the statement true: “Parasitic worms have cilia as adults”?

3. Find in the text of the paragraph a description of the skin-muscular sac. Explain why it was called that.

4. Remember the internal structure of coelenterates. Compare the internal structure of coelenterates and flatworms. Note what complications have occurred.

U flatworms there is no internal cavity, and the internal organs, combined into systems, are located inside the skin-muscular sac.

5. Write down the definitions of concepts:

Intermediate host - an organism in which worm larvae develop and reside for some time.

suction cups, hooks, proboscis

Worms produce many eggs to survive. Many eggs die either without finding an intermediate host, or after entering the body of an unusual animal.

8. List the characteristics that correspond to each class of flatworms

Answer:
A - 1, 7, 9, 6
B - 2, 3, 8, 11
B - 2, 4, 5, 8, 10

Guinea worm

There are worms that live in human blood. These include schistosomes. Their main habitat is blood vessels. However, they are able to penetrate various organs, causing symptoms of damage to the genitourinary system, liver, and kidneys.

The blood may contain larvae of some helminths. For example, in tapeworms this is how they spread throughout the body of the intermediate host. With the blood flow, the larvae migrate to various organs, where they attach and form cysts containing the heads of adult worms. When the latter enter the digestive tract of the final host, they attach to the intestinal wall, giving rise to a sexually mature individual.

Flatworms: general characteristics

The body of flatworms is capable of complex and varied movements.

All flatworms have common features buildings:

• The outer cover is represented by the cuticle. In free-living individuals, it is covered with cilia; the surface of the body of worms is usually smooth.
• Under the outer covering there are several layers of muscle fibers.
• There is no body cavity.
• The digestive system has only one opening - the mouth. The intestine ends blindly. Some worms lack digestive organs altogether. So, tapeworms absorbing nutrients the entire body from the host's intestinal lumen, they are not needed.
• There is no circulatory system or blood, as well as respiratory organs.
• The excretory system is represented by a network of tubes that penetrate the entire body.
• Nervous system primitive. Near the pharynx there are several ganglia from which nerve trunks connected by jumpers extend. Sense organs are formed only in free-living individuals and some worms at the larval stages of development.

The system that is really well developed is the sexual system. Flatworms are hermaphrodites. Reproduction is possible with the participation of 2 individuals or by self-fertilization.

Flukes

The development cycle of trematodes is one of the most complex. Miracidia emerge from eggs released into the external environment. The latter feel comfortable in water and exist for some time as free-living organisms. The next stage is the introduction of miracidia into the first intermediate host. The larva does this using a special cutting apparatus on the head. The host is usually a mollusk.

Their life cycle can take place in several hosts and is accompanied by regular alternation

Here the miracidium turns into a sporocyst, which gives rise to the next stage of the development cycle - redia. Those, in turn, are the predecessors of cercariae, which leave the intermediate host and again enter the aquatic environment. Next, the development cycle follows one of two options. Cercariae transform into cysts directly during external environment(attached to algae) or in the body of a second intermediate host (mollusk, fish, amphibian).

These are the longest worms with a transparent shell

Infection of the definitive host occurs when it eats infected organs of the intermediate host. The development cycle ends with the attachment of the head from the cyst to the intestinal wall and the development of the adult worm. The latter can reach significant sizes (for example, the wide tapeworm grows up to 10 m long).

For flukes, humans are the final host, but for tapeworms they can also be an intermediate host.

What symptoms occur when a person is infected with a helminth? The clinical picture of the disease is determined, first of all, by which organ is affected. Sexually mature worms usually live in the intestines, so the overall picture of the disease is dominated by symptoms characteristic of digestive disorders: nausea, gas formation, bowel problems, abdominal pain.

Helminths secrete waste products that, when released into the blood, cause poisoning and symptoms of intoxication (fever, fatigue, etc.). In addition, they are perceived by the immune system as an allergen. Therefore, helminthiasis is often accompanied by symptoms allergic reaction(skin rashes, itching).

“Structural features of planaria” - Internal structure white planaria. White planaria or milky planaria. White planaria. General signs type. The structure of a white planaria. General signs. Excretory system of planaria. Eyelash worms. Coelenterates. Variety of flatworms. Regeneration of the planarian body. White planaria. Various types planarian. Bilateral and radial symmetry of the body. Layers of the body of planaria and hydra. Internal structure of planaria.

“The structure of flatworms” - Movement. Digestive system of flukes. Nervous system. Sense organs. Eyelash worms. Turbellaria. Excretory system. Reproductive system. Life cycles of tapeworms. Reproductive system of flukes. Flukes are extremely fertile. Class Flukes. Gas exchange and transport of substances. Digestive system of ciliates. Type Flatworms. Tapeworms. Development of flukes. The reproductive system is tape.

“Structure of planaria” - Type Flatworms. Excretory system. The appearance of the third germ layer during development. The eggs are covered with dense shells. Milk planaria. Space between organs. Planarian movements. Reproductive system. Digestive system. Signs of flatworms. The body of a planaria. Type: Ciliated worms. Flatworms. Internal structure of planaria. Circular muscles. Single layer epithelium. Nervous system.

“Structure of a white planaria” - Body coverings. Plathelminthes. Nephridia and accumulation buds. Variety of flatworms. Group composition. Flatworms. The structure of planaria. Structure. Capture of food by a white planaria. Muscle location. Nervous system and sensory organs. Musculature. Throat and gut. Food and movement. Complication of the body cavity. Class Turbellaria. Annelids. Nervous system of a white planaria.

Let's start the description with a little wince. worms. What can we do if such trump cards are available in the thick “deck” of the natural diversity of life forms.

I write “trump cards” not only because “ worms". The evolution of multicellularity from two-layered cells led to much more advanced forms of organisms with a three-layered body structure. And then nature had to tinker for a long time, creating not just one, but entire ones.

Somehow it even becomes a shame for all mammals, which represent only a separate class of organisms in the type of chordates. And here, “some kind of worms” - and whole three types: flatworms, roundworms and annelids.

Well, let's start everything in order, so:

……………… Type Flatworms (three-layered)

…………………………………. K l . A. With. With. s

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.. Ciliary worms……………………….. Flukes……………………….. Tapeworms

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White planaria…. Liver fluke …… …………… Bovine tapeworm ___________________________________________________________________________________

……………………………………………….. More than 15 thousand species

Habitat: marine and fresh water bodies, wet soil, human and animal bodies.

……..
Structure: bilaterally symmetrical . For the first time, embryos develop third germ layer – mesoderm, from which parenchymal cells and the muscular system develop. Body flattened.

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Body coverings and muscular system: skin-muscular sac - made of single-layer epithelium (maybe be with eyelashes) and three layers smooth muscles (circular, longitudinal and oblique).

Movement: contraction of muscles (flukes, tapeworms) or movement of cilia andmuscles (cilia worms).

Body cavity: absent , internal organs are located inparenchyma.

Digestive system:has two sections - anterior (mouth, pharynx) and middle (branches intestines). The intestine is closed, no anal opening and food residues are removed through the mouth. In tapeworms digestive system absent- absorption of food by all cells of the body. As you remember, this is one of their forms biological progress —.

Excretory system: appears for the first time , formed by a system of tubules. One end begins in the parenchyma stellate cell with a bunch of cilia, and the other flows into excretory duct. Channels are combined into one or two common channels ending excretory pores. Elementary the unit of the system isprotonephridia.

Nervous system:from suprapharyngeal ganglia(ganglia) and longitudinal nerves trunks, related crossbars(ladder type).

Sense organs: touch And chemosensitive cells. Free-living animals have organsvision And balance.…………..

Reproductive system: To usually hermaphrodites.Men'sreproductive system: testes, vas deferens, ejaculatory duct and copulatory organ. Women'sreproductive system: ovary, oviduct, uterus, zheltochniki.

1. Appearance of the third germ layer -mesoderm.
2. The appearance of the excretory system - protonephridia.
3. Emergence of the nervous system ladder type.

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Integument of the body The outside of the body is covered with single-layer epithelium. In ciliated worms, or turbellarians, the epithelium consists of cells bearing cilia. Flukes, monogeneans, cestodes and tapeworms lack ciliated epithelium for most of their lives (although ciliated cells may be present in larval forms); their integument is represented by the so-called tegument, which in some groups carries microvilli or chitinous hooks. Flatworms that have a tegument are classified as Neodermata. Flatworms can regenerate 6/7 of their body.

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

Nervous system and sensory organs The nervous system is represented by nerve ganglia located in the front part of the worm's body, cerebral ganglia and nerve columns extending from them, connected by jumpers. Sense organs are usually represented by individual skin cilia - processes of sensory nerve cells. Some free-living representatives of the type, in the process of adaptation 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 caudal ends, somewhat flattened in the dorsoventral direction, in large representatives it is strongly flattened. The body cavity is not developed (except for some phases life cycle tapeworms and flukes). Gases are exchanged across the entire surface of the body; respiratory organs and blood vessels are absent.

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

Interesting facts 1. By digesting, flatworms are able to “learn.” A team of scientists has made an unusual discovery about the abilities of flatworms. It turns out that if planar worms are first trained to go through a maze, then ground into a puree and given to other worms to eat, then they will be able to go through this maze the first time.

Interesting facts 2. A heterosexual species of worms - schistosomes are inseparable throughout their lives. The female lives in the male's pocket all her life.

Interesting facts 3. Almost all types of flatworms can turn inside out. 4. Here are some more interesting facts about flatworms. For example, flatworms are truly almost immortal. If you cut off a very small piece of the worm, about 1/100 the size 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 discovered nettle cells that are very similar to the stinging cells found in coelenterates. It turns out that these cells actually previously belonged to coelenterates, which were subsequently eaten by ciliated worms. Stinging cells are not digested by worms. They enter their skin and serve both defensive and offensive functions.

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