"Features of the structure of the planaria" - The internal structure of the white planaria. White planaria or dairy. White planaria. General characteristics of the type. The structure of the white planaria. General signs. The excretory system of a planaria. Eyelash worms. Coelenterates. Manifold flatworms. Planarian body regeneration. White planaria. Various types of planarians. Bilateral and radial symmetry of the body. Body layers of planaria and hydra. The internal structure of a planaria.
"The structure of flatworms" - Movement. Digestive system of flukes. Nervous system. Sense organs. Eyelash worms. Turbellaria. excretory system. Sexual system. Life cycles of tapeworms. The reproductive system of flukes. Flukes are extremely prolific. Flukes class. Gas exchange and transport of substances. Digestive system of ciliaries. Type Flatworms. Tape worms. Development of flukes. The reproductive system is tape.
"The structure of planaria" - Type Flatworms. excretory system. The appearance in the process of development of the third germ layer. Eggs are covered with dense shells. Dairy planaria. Space between organs. Planarian movements. Sexual system. Digestive system. Signs of flatworms. Planarian body. Type Ciliary worms. Flatworms. The internal structure of a planaria. Ring muscles. Single layer epithelium. Nervous system.
"The structure of the white planaria" - Integuments of the body. Platehelminthes. Nephridia and accumulation kidneys. Variety of flatworms. Composition of the group. Flatworms. The structure of the planaria. Structure. Capturing food by white planaria. Location of muscles. Nervous system and sense organs. Musculature. Throat and intestine. Food and movement. Complication of the body cavity. Turbellaria class. Ringed worms. The nervous system of the white planaria.
§ 1 Habitats and external structure of Flatworms
Type Flatworms has about 15 thousand species of animals. Flatworms are found in all habitats: aquatic, soil, terrestrial-air and organismic. Their body sizes vary from half a millimeter to 15 meters. However, despite such a variety of species, all representatives of this type have a number of common features.
All representatives of Flatworms are multicellular animals and have bilateral body symmetry. Let's remember what symmetry is. Symmetry in biology is the regular arrangement of identical parts of the body relative to the center, which is called the axis of symmetry. Bilateral symmetry means that one side of the animal's body is a mirror image of the other side.
An important feature external structure representatives of this type of animal is also a flattened top and bottom body shape. Outside, the body of Flatworms is covered with only one layer of epithelium, under which there are 3 layers of muscles. The totality of the skin and muscles of the worms is commonly called the skin-muscular sac.
§ 2 Internal structure of Flatworms
Speaking about the internal structure of this type of animal, it must be remembered that the circulatory and respiratory systems are absent. They are characterized by aerobic or anaerobic respiration. Oxygen enters the body through the entire surface of the body.
The digestive system of Flatworms is represented by a mouth, pharynx and highly branched intestines. However, the posterior intestine and anus are absent, so undigested food remains are excreted through the mouth.
The work of the excretory system is aimed at removing excess water and some metabolic products from the body. In flatworms, it is represented by a whole network of branched tubules, which are located along the entire body, uniting into 1 or 2 excretory canals, they open at the posterior end of the body.
A pair of supraesophageal ganglions and longitudinal nerve trunks, connected by strands, form the nervous system. Of the sense organs, Flatworms have light-sensitive eyes, special balance organs, and tactile cells.
Most species of Flatworms are hermaphrodites. Hermaphrodites are called animals, in the body of which there are simultaneously organs of both the male and female reproductive systems. Despite this, 2 individuals are involved in the process of fertilization.
§ 3 Systematics of Flatworms
Type Flatworms are divided into 3 main Classes, namely Class Ciliary Worms, Class Flukes and Class Tapeworms.
The class Ciliary worms includes about 3.5 thousand species of animals. Most Ciliary worms are free-living, ie. they live in any habitat, with the exception of the organism. Their skin is covered with cilia, which gave the name to this class. Due to muscle contraction, the cilia move, thereby moving the body in space. The most famous representatives of the Class Ciliary worms are: Dairy Planaria, Black Planaria and Many-eyed.
List of used literature:
- Konstantinov V.M. lesson planning to the textbook "Biology. Animals ”for grade 7, Konstantinov V.M., Babenko V.G., Kumchenko V.S. / Konstantinov V.M. - M.: Ventana-Graf, 2005. - 304 p.
- World Encyclopedia: Biology / Ch. ed. M.V. Adamczyk: Ch. scientific Ed. V.V. Adamchik: Mn .: Modern writer, 2004. - 832 p.
- Iontseva A.Yu. Biology in schemes and tables / A.Yu. Iontseva, A.V. Torgalov. - M.: Eksmo, 2014. - 352 p.
- Sadovnichenko Yu.A. Biology / Yu.A. Sadovnichenko. – M.: Eksmo, 2013. – 512p.
- Biology: a guide for applicants to universities: In 2 vols. V.1. - 2nd ed., Rev. and additional - M .: RIA "New Wave": Publisher Umerenkov, 2012. - 512p.
Used images:
Structural features Bilaterally symmetrical - a single cavity of symmetry 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 in the course of evolution and gives rise to the development of parenchymal cells that fill the gaps between the organs and the muscular system. Left half Right half
Structural features Body sizes from 2-3 mm to 20 m. The body is elongated and flattened in the dorsal-abdominal direction; has a ribbon-like or leaf-like shape. The presence of developed organ systems is characteristic: muscular, digestive (absent in ribbon), excretory nervous and sexual.
Integuments of the body and the muscular system The cells of the epithelium and muscles 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: annular, 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 (ciliary worms).
The digestive system has two sections - anterior (mouth, pharynx) and middle (intestinal branches). The intestine is closed blindly, the posterior intestine and anus are absent. Undigested food remains are removed through the mouth. Tapeworms have no digestive system (represented by separate digestive cells).
Excretory system Formed by a system of tubules, one end of which begins in the parenchyma with a stellate cell with a bundle of cilia, and the other flows into the excretory duct. The duct unites into one or two common channels, ending in excretory pores.
Nervous system. Sense organs. It consists of supraglottic ganglions (ganglia) and longitudinal nerve trunks that run along the body and are connected by transverse nerve bridges. Sense organs - touch and chemical sense. Free-living people have organs of touch and balance.
Hepatic fluke Hepatic flukes, usually up to 3 cm long, 1.3 cm wide. Hepatic flukes of the order Opisthorchis cause opisthorchiasis, early symptoms - liver enlargement, allergic reactions and gastrointestinal disturbances; late stage symptoms - 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 The life cycles of different genera are different. In species of the genus Fasciola, development occurs with one intermediate host (freshwater snail), and infection of the final host occurs when swallowed with water or eaten with coastal plants of the resting stage - adolescaria. In species of the genera Opisthorchis and Clonorchis, the second intermediate host is freshwater fish, and infection of the final host occurs by eating raw fish with invasive stages. In species of the genus Dicrocoelium, terrestrial lung snails and ants serve as intermediate hosts, and infection of the final host (usually a herbivore) occurs when an infected ant is eaten with grass.
Bull tapeworm (tapeworm) Affects cattle and humans, causing teniarinhoz. Infection with bovine tapeworm is especially common in equatorial Africa, Latin America, in the Philippines and parts of Eastern Europe. An adult bull tapeworm consists of more than 1000 segments and reaches 4-40 meters in length. The laying of the reproductive apparatus begins at about the 200th segment. Length of mature proglottids mm, width 5-7 mm. The scolex (head section) is equipped with 4 suckers without hooks (therefore unarmed). The life span of bovine tapeworm in the human intestine, if no deworming measures are taken, is years. A tapeworm produces ~ 600 million eggs per year, ~ 11 billion in a lifetime.
Development cycle Segments containing eggs are excreted 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, which penetrate into the blood vessels of the intestine and then into the muscles. In the muscles, the larva turns into Finns (a vial with a tapeworm head inside). When a person eats poorly processed finoz meat, the tapeworm head attaches to the intestinal wall and begins to produce segments.
Structural features Bilaterally symmetrical. Sizes 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. Body filiform, fusiform, non-segmented, round in cross section.
The digestive system is formed by the anterior, middle and hindgut. The foregut is differentiated into sections: mouth with cuticular lips, pharynx and esophagus. The middle and hindgut are not divided into sections. The digestive tract ends at the anus.
The excretory system is represented by 1-2 skin glands (modified protonephridia). These are large cells, from which two channels depart on the sides of the cell. At the posterior end of the body, the channels end blindly, and in front they open into the external environment with an excretory pore.
Nervous system. Sense organs Ladder-type nervous system. It is represented by the head nerve nodes (ganglia), the peripharyngeal nerve ring and several nerve trunks (dorsal and abdominal), median transverse bridges. The sense organs are represented by the organs of touch and chemical sense. Marine forms have light-sensitive receptors. Scheme nervous system roundworms: 1 - oral papillae with tactile endings and the nerves innervating them, 2 - circumopharyngeal nerve ring, 3 - lateral head 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
Ascaris human Ascarids are large roundworms, their length can reach 40 centimeters. Most often affect the organs of the gastrointestinal tract, causing ascariasis. The favorite habitat of adults is the small intestine. Roundworms are bisexual worms. Ascaris females can produce more than 200 thousand eggs per day. Fertilized eggs from the human intestine enter the soil. They develop larvae. Infection occurs when drinking water from open reservoirs, eating poorly washed vegetables, fruits that have eggs with larvae. In the human body, the larva migrates: once in the intestine, it perforates its walls and enters the blood stream.
Structural features Bilateral symmetry of the body. Sizes from 0.5 mm to 3 m. The body is divided into the head lobe, trunk and anus. The polychaetes have a separate head with eyes, tentacles and antennae. The body is segmented (external and internal segmentation). The trunk 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 regeneration.
Integuments of the body 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 muscles (outer annular and inner longitudinal) and a single-layer epithelium of the secondary body cavity. With the contraction of the circular muscles, the body of the worm becomes long and thin, with the contraction of the longitudinal muscles, it shortens and thickens.
Body cavity Secondary - whole (has an epithelial vystilka). In most, the body cavity is divided by transverse partitions corresponding to body segments. The cavity fluid is a hydroskeleton and an 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, goiter), 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.
The circulatory system is closed. There are two vessels: dorsal and abdominal, connected in each segment by annular vessels. Through the dorsal vessel, blood moves from the posterior end of the body to the anterior, along the abdominal vessel from front to back. The movement of blood is carried out due to the rhythmic contractions of the walls of the spinal vessel and the annular vessels ("heart") in the pharynx. Many people have red blood.
The excretory system is of the Metanephidial type. Metanephridia look like tubes with funnels, two in each segment. The funnel, surrounded by cilia, and convoluted tubules are in one segment, and a short tubule that opens outwards with an opening - an excretory pore - is in the next segment.
Nervous system. Sense organs. It is represented by supraesophageal and subpharyngeal nerve nodes (ganglia), which are connected to the peripharyngeal nerve ring and the abdominal nerve chain, consisting of paired nerve nodes 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 hermaphodites. Sex glands develop only in certain segments. Insemination is internal. The type of development is direct. Asexual reproduction is carried out by budding and fragmentation (due to regeneration). Marine representatives are dioecious. Development with metamorphosis, trochophore larva.
With a little frown, let's start the description worms. What to do if there are such trump cards 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-layer has led to much more perfect forms of organisms with a three-layer body structure. And then nature had to tinker for a long time, creating not one, but whole.
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 layers)
…………………………………. K l . A. With. With. s
__________________________________________________________________________________
.. Ciliary worms……………………….. Flukes……………………….. Tapeworms
___________________________________________________________________________________
White planaria…. Liver fluke …… …………… Bull tapeworm ________________________________________________________________________________________________
………………………………………………..
More than 15 thousand species
Habitat : marine and fresh water bodies, moist soil, human and animal organisms.
……..
Structure: bilaterally symmetrical
. For the first time in embryos, a third
germ layer –
mesodermfrom which parenchymal cells and the muscular system develop. Body flattened.
………..
Integuments of the body and muscular system: skin-muscular sac - from a single-layer epithelium (may be with eyelashes) and three layers smooth muscles (circular, longitudinal and oblique).
Movement: muscle contraction (flukes, tapeworms) or movement of cilia andmuscles (ciliary worms).
body cavity: absent , the internal organs are located inparenchyma.
Digestive system:has two sections - anterior (mouth, pharynx) and middle (branches intestines). The bowel is closed anal opening is missing and leftover food is removed. through the mouth. At the tapeworms digestive system absent- absorption of food by all cells of the body. As you remember, this is one of the forms of biological progress -.
excretory system: appears for the first time formed by a system of tubules. one end starts in the parenchyma stellate cell with a bunch of cilia, and the other flows into excretory duct. ducts combined into one or two common channels ending excretory pores. Elementary unit of the system areprotonephridia.
Nervous system:from supraesophageal ganglions(ganglia) and longitudinal nerves trunks, related cross jumpers(ladder type).
Sense organs: touch And chemosensitive cells. Free-living people 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, yolk glands.
1. The 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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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 arose when trying to separate flatworms into different groups, scientists attribute them to the 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 colonize the organs of the definitive 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 mollusks. 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 become big problem for lovers of breeding fish in aquariums.
The habitat of flatworms is mostly aquatic. Being flukes, flatworms can attach by means of an attachment disc 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 settled in 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 may 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:
- Wash your hands thoroughly with soap and water before every meal and after visiting public places, toilet, street, communication 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.