Plural number gender case of nouns. "Spelling noun endings in the genitive plural form". §2.3. Fractional numbers

The type of roundworms or Nemathelminthes is one of the most numerous among the animal kingdom. There are over 20,000 species.

Turbellarians are considered their ancestors, but in the course of evolution, roundworms acquired special features building, which allowed them to form a separate group.

The following classes of roundworms are distinguished:

1. Class Nematodes;
2. class ventral;
3. Kinoryncha class;
4. Hairy class;
5. Class Rotifers.

Features of the structure of roundworms

Sizes vary from 80 microns to 8 meters. Females are usually larger than males. All representatives have bilateral symmetry.

The body shape is often cylindrical or fusiform, characterized by the absence of segmentation. A dense cuticle completely covers the body from the outside. The body cavity of roundworms is surrounded by a skin-muscular sac. It contains a liquid that fills the space between internal organs. Serves as a support and performs a transport function.

Digestive organs

The digestive system of roundworms has a more progressive structure. Roundworms are different from flatworms the presence of an anus. They also have a separate hindgut.

The digestive tract is divided into three parts: anterior, middle and posterior. Food is absorbed through the mouth opening, enters the pharynx and esophagus. Digestion of the food bolus takes place in the middle section, and after absorption nutrients, the remainder is expelled.

The movement of food is now carried out only in one direction, which contributed to better digestion.

excretory system

The excretory function is performed by the cervical gland, a large unicellular formation, from which a pair of lateral tubules departs. They open outward through the excretory pore.

Ammonia is able to leave the body of roundworms through the skin by diffusion.

reproduction

Most representatives of the type are dioecious organisms. Often females and males have a different appearance (the phenomenon of sexual dimorphism). Development is direct, without a larval stage, and indirect with a change of hosts.

reproductive system roundworms are presented in the form of tubes. In males, this is more often one tube, which is divided into specialized departments. At the beginning, the testis is located, where the production of spermatozoa takes place, which enter the ejaculatory canal through the vas deferens. It opens into the distal part of the intestine - the cloaca. With the help of copulatory organs (cuticular needles), spermatozoa are brought out.

The female genital tract consists of two paired tubes. They are blindly closed in the initial section, here are the ovaries, where there is a constant reproduction of germ cells. The gametes travel through the oviducts and enter the uterus, where internal fertilization occurs.

Roundworm eggs are surrounded by a thin shell rare cases she's fat. There are species capable of viviparity.

Nervous system

It is represented by the peripharyngeal ring and longitudinal nerves. The ring is located in the pharynx and serves as the main associative organ. The ventral and dorsal nerves arise directly from the main ganglion and lie in the hypodermis, others nerve fibers not related to him.

The sense organs of roundworms are poorly developed. There is a chemical reception, organs of touch, free-living sea ​​views have photosensitive cells.

At the distal end of the body of roundworms are tail glands, the secreted fluid of which is necessary for attachment to the substrate.

Also, roundworms in their life cycle often use intermediate hosts for full development. This is not typical for ringed worms. annelids differ from roundworms in the presence of a closed circulatory system, represented by the abdominal and dorsal vessels.

Comparison of flat and roundworms, their similarities and differences

The nutrition of nematodes depends on the lifestyle, some consume algae and bacteria, others feed on the host's body, there are also predatory species.

Significance in nature and human life

Roundworms are an integral part of food chains. Free-living individuals absorb bacteria, protozoa, and themselves become food for fish and crustaceans.

Species living in the ground feed on decayed organic matter, thus participating in soil formation.

Roundworms can infect fungi and plants, significantly reducing yields. The nematodes enter root system and lead to the death of the rhizome, thereby inhibiting plant growth. Cereal and vegetable crops (onion, potato, wheat nematodes) are most often infected.

Type Roundworms

Answer plan:

• General characteristics of roundworms
• The structure of the body of Ascaris human
• Reproduction and development of Ascaris human
• Classification of Roundworms, variety of species
• The value of roundworms in nature and human life

General characteristics of roundworms

Covers. Outside skin-muscle sac covered with a protective sheath - cuticle. During the growth of the worms, it is periodically reset, and then resumed. Under the cuticle is the hypodermis, which is the result of the fusion of skin cells. Under the hypodermis are 4 ribbons of longitudinal muscles. During contraction, the dorsal and ventral bands act oppositely, and the body of the worm can bend in the dorsal-ventral direction. The cuticle, hypodermis, and muscles form the skin-muscular sac.

Digestive system. At the level of Roundworms, a grand event occurs in the evolution of the digestive system, which made all subsequent types of animals happy. It is in Roundworms that the hindgut and anus first appear. Now them digestive system consists of three sections: anterior, middle and posterior intestines. The anterior section is usually divided into the mouth, muscular pharynx, and esophagus. Digestion takes place in the middle part of the intestine. With the appearance of the anus, food begins to move in one direction, which allows different departments to specialize and more effectively perform their function of digestion.

excretory organs- in some protonephridia, in the anterior part of the body on the ventral side there is an excretory opening. Some representatives have modified skin glands, they are called "neck glands". Some excretory organs are absent.

Nervous system and sense organs. Nervous system of ladder type (orthogon). It consists of a near-pharyngeal nerve ring surrounding the pharynx, and 6 nerve trunks extending forward and backward, of which the dorsal and abdominal are most strongly developed. The trunks are connected by jumpers (commissures). There are organs of touch, organs of chemical sense (smell). Free-living people have primitive eyes.

Reproduction. Most Roundworms are dioecious organisms, which ensures the genetic diversity of offspring. There is sexual dimorphism (females look different from males) Development is indirect, that is, with larval stage without a change of owner.
Sexual organs in the form of tubes. Male - testes, open with a vas deferens into the final section of the intestine - the cloaca. The male has copulatory organs - cuticular needles, with the help of which he injects spermatozoa into the female genital tract. Fertilization is internal. In the female, the paired ovaries continue into the oviducts, which pass into two uteruses, which open with a genital opening on the ventral side of the body.

Representatives: The type is divided into several classes, the most numerous among them is the Nematode class: Ascaris, pinworms.

The structure of the body of Ascaris human

New concepts and terms: cuticle, helminth, invasion, copulatory organs, sexual dimorphism, hydroskeleton, anus, detritus feeder.

Questions for reinforcement.

Literature:

1. Bilich G.L., Kryzhanovsky V.A. Biology. Full course. In 3 volumes - M .: LLC Publishing House "Onyx 21st Century", 2002
2. Pimenov A.V., Pimenova I.N. Zoology of invertebrates. Theory. Tasks. Answers.: Saratov, JSC publishing house "Lyceum", 2005.
3. Chebyshev N.V., Kuznetsov S.V., Zaichikova S.G. Biology: a guide for applicants to universities. T.2. - M .: New Wave Publishing LLC, 1998.
4. www.collegemicrob.narod.ru
5. www.deta-elis.prom.ua

The characteristic features of the type organization are as follows:

The body is thin, cylindrical, elongated and pointed at the ends. On a transverse section, it is round (which gave the name to the type).

The skin-muscular sac consists of an outer multilayer without cellular structure cuticles, below it single layer epithelium And layer longitudinalmuscle fibers thanks to the contractions of which the body can bend serpentine.

body cavity - primary, filled with liquid under greater than atmospheric pressure. The cavity fluid gives the body elasticity and, due to this, plays the role hydroskeleton. It also provides transport of nutrients and waste products.

For the first time in the animal kingdom, the digestive system is represented through digestive tube, divided into three sections - the anterior, middle and hindgut. beforedepartment starts mouth opening, leading to the oral cavity and pharynx, capable of working as a pump. The pharynx is separated from the midgut by a valve. IN midgut food is digested and absorbed. The midgut is followed by the ectodermal posterior intestine, opening on the ventral side of the body anus.

The excretory system is represented by a pair of lateral longitudinal canals that merge under the pharynx into one duct and open on the ventral side of the body as an excretory opening. The end products of vital activity accumulate in the cavity fluid, and from it they enter the excretory canals.

The nervous system is represented annular parapharyngeal ganglion and several longitudinal ones extending from it nerve trunks, interconnected by semicircular nerve bridges. There are organs of taste, touch, and free-living roundworms have light-sensitive eyes.

roundworms - dioecious animals that reproduce only sexually. In roundworm, males and females are outwardly distinguishable (sexual dimorphism). The reproductive system has a tubular structure: in the female - paired ovaries, oviducts, uterus and unpaired vagina, in the male - unpaired testis, vas deferens, ejaculatory canal, copulatory apparatus. Fertilization is internal, development usually proceeds with incomplete transformation (with the larval stage).

A

Rice. 14. Appearance(a) and internal structure (b) roundworm: 1 - mouth opening; 2 - pharynx; 3 - intestines; 4 - vagina; 5 - uterus; 6 - oviduct; 7 - ovary; 8 - ejaculatory canal; 9 - testis; 10 - seed tube.

The development cycle is complex, associated with the release of eggs during external environment and migration of larvae in the human body. Fertilized eggs, covered with dense protective shells, from the human intestine enter the soil. In the presence of oxygen and a sufficiently high temperature, a larva develops in them for about a month. The egg becomes contagious (invasive). With contaminated water and food, eggs enter the human small intestine. Here the larvae are released from the shell, pierce the intestinal mucosa with their elastic body and penetrate into the blood vessels. With the blood flow through the portal and inferior vena cava, they enter the right atrium, right ventricle and lungs (through the pulmonary arteries). From the lung tissue penetrate into the bronchi, from them into the trachea, and then into the pharynx. During migration, the larvae develop in the presence of oxygen. From the pharynx, they enter the intestines, where they complete their development cycle. Life expectancy is about a year.

At whipworm the front end of the body is so thin that it looks like a hair. The posterior end is sharply thickened. The length of the male reaches 30 - 40 mm, and the female - 35 - 50 mm. The thin part of the body contains only the mouth and esophagus with 1-2 rows of large glandular cells; muscles are poorly developed. In the back, thicker part of the body are the intestines and genitals. The females produce very typical eggs, the presence of which in human stool is an unmistakable indication of whipworm infestation.

A person becomes infected with whipworm by drinking water that contains its eggs. In water, especially warm, eggs develop in about one or one and a half months. After the eggs enter the intestines, young whipworms (larvae) emerge from them, developing into adult forms upon reaching normal localization, i.e. in the large intestine. The expulsion of the whipworm is not an easy task precisely because it “pierces” the mucous membrane and is firmly held in place. It can cause indigestion, anemia, nervous phenomena.

Much more dangerous trichinella. This nematode has achieved a very high specialization.

How to protect yourself from infection with trichinosis? Rats become infected by eating trichinosis pork meat, pigs become ill with trichinosis by eating rats. Therefore, the fight against rats, their indispensable destruction in pig farms is one of the most important anti-Trichinellosis measures. The purchase of pork must be made only through the state trade network or markets controlled by the veterinary medical center.

Roundworms have a ubiquitous distribution and a high number of individuals, which indicates the biological progress of this group of animals. Their ancestors are considered ancient ciliary worms.

Control questions:

1. What are the features of the external and internal structure of Roundworms?

   What way of life is characteristic of human ascaris?

   Which life cycle has roundworm human?

   What features of development are inherent in pinworms?

   Why is whipworm dangerous for humans?

   What preventive measures to prevent helminthic diseases (ascariasis, trichinosis) should be observed?

1. In the genitive plural of nouns with a stem, the hissing is not written b: dachas, groves, circuses, conflagrations.

2. In the unstressed ending of the genitive plural of nouns on -ya, -ya, -ya and usually -e spelled -th: station - stations, songstress - songstress, village - villages, estate - estates (but: gun - guns, dress - dresses, mouth - mouths; also apprentice (noun male gender) - apprentices).

3. In the genitive plural after en not spelled b: cherry, slaughter.

Exception: young ladies, hawks, villages.

205. Write by opening brackets. Explain the use of the letter b after hissing.

Water (tornadoes), caustic (alkali), (bitterness) of separation, waterproof (cloaks), ancient (swords), drive past birch trees (grove), joy of unexpected (meetings), alpine greenery (pasture), buy black (carcasses), perform several times (carcasses), the glow of the distant (fire), the construction of winter (vegetable storage), viewing (telecast).

206. Write using the words in brackets in the genitive plural form. Explain their spelling.

1) Most of all, the hares liked to feast on young seedlings and shoots (apple), (plum) and (cherry) in orchards. (M.-S.) 2) It is easy to imagine what impression Alexei must have made in our circle (young lady). (P.) 3) In the garden, the orchestra struck a potpourri of Russians (song). (Ch.) 4) Birds left their native places (nesting). (Ch.) 5) Thunder (gun) rolled dully over the smoky horizon. (A. N. T.) 6) Field haze (kitchen) curled behind the wood. 7) Mud-splattered houses flashed from the sides of the road (suburb). (A. N. T.) 8) Sharp tops (tower) are visible. (A. N. T.) 9) The storm was spraying through the windows of the low port (building). (paust.)

207. Form the genitive plural from the following masculine nouns. Make up 7 phrases with formed words.

1) Bashkirs - Bashkirs, Bulgarians, Buryats, Georgians, Ossetians, Romanians, Tatars, Turkmens, Gypsies, Turks.

2) Kirghiz - Kirghiz, Kazakhs, Uzbeks, Tajiks, Yakuts.

3) > felt boots - felt boots, boots, stockings, shoes. Straps - straps, socks.

4) Volts - volt, amperes, microns, arshins. Meters - meters, grams, kilograms, hectares. Lemon - lemons, oranges, eggplant, tangerines, tomatoes, tomatoes.

208. From the following nouns of the middle and female form the genitive plural. Make up 10 phrases with formed words.

I. Neuter nouns:

1) Windows - windows, grains. Troop - Troops, apple. 2) Number - numbers, armchair, log, canvas, fiber, rib, core. 3) Blanket - blanket, towel, saucer. Swamp - swamps, lace, hoof, trough.

II. Feminine nouns:

1) Shutter - shutters, fable, song, blast furnace. Foot - foot, trap, nostril. 2) Skittles - skittles, saklya, strife. Waffle - waffles, shoes, shafts. Wedding - weddings, manor.

209. Form the genitive form of the following nouns that are used only in plural. Set the accent. Make up six phrases with formed words.

1) Hours - hours, tongs, bridges, glasses, vise. Frosts - frosts, memoirs, pliers, abacus. Wallpaper - wallpaper, beatings.

2) Spray - spray, pants, beads, holidays, pasta. Money - money, darkness, stretcher, sled.

3) Weekdays - weekdays, ticks, manger. Yeast - yeast, people, bran, sleigh.

210. Read. Indicate which part of the sentence the underlined nouns are. Write with the missing punctuation marks.

1) Music is like the soul of the song her wings on which she flies. (Isak.) 2) To read is to enrich oneself with language with words. (M. G.) 3) My friend engineer asked me to go to him in the north of Polissya. (Cupr). 4) The clock in the kitchen showed nine. (A. N. T.) 5) With its green dams, the forest blocks the way for the free-flowing sands of the desert scouts. (Paust.) 6) young man the warrior goes to battle. (L.) 7) His father [Arkady] Nikolai Petrovich Kirsanov is a man of about forty years old. (D.P.) 8) Ancient lindens contemporaries Peter the Great, who once gave this park along with the palace to his beloved nobleman, is so fabulously so incredibly high that a person walking under them involuntarily feels small. (Cupr.)

211. Write the sentences using the nouns given in brackets in the genitive plural form. Identify the stem and ending of these nouns.

1) Travelers traveled without any (adventure). (G.) 2) A crowd of visitors (foreigner): (Frenchman), (German), Englishmen - everything merged into one picture in the dark and dense alleys. (L.) 3) A pig once wormed its way into the manor's yard, around (the stable) there and (the kitchen) leaned over. (Cr.) 4) Our camping equipment consisted of (a gun), an ax, two linen tents. (Ars.) 5) A month of late (kiss), late (rose) and (lightning) late! (Shower) stellar - August! (Color) 6) Small trees (mandarin) bring up to four thousand fruits every year. (paust.)