Type Annelids(Annelida)
Let's get acquainted with a very interesting group of animals, the structure and behavior of which did not leave even Charles Darwin indifferent. He devoted a lot of time to the study of annelids and wrote several scientific papers about them.
Among worms, it is the annelids that are considered the most progressive group. This conclusion is made primarily on the basis of the structure of animals.
Type Annelids includes secondary cavity animals whose body consists of repeating segments, or rings. Annelids have closed circulatory system .
Secondary body cavity , or in general (from Greek koiloma- “recess”, “cavity”), develops in the embryo from the mesoderm layer. This is the space between the body wall and the internal organs. Unlike the primary body cavity, the secondary cavity is lined with its own internal epithelium. The secondary body cavity is filled with fluid, creating permanence internal environment body. This liquid is involved in metabolism and ensures the functioning of the digestive, circulatory, excretory and other organ systems.
Annelids have a segmented body structure, that is, they the body is divided into next friend after another plots -segments , or rings (hence the name - annelids). Such segments in individuals different types there may be several or hundreds. The body cavity is divided into segments by transverse partitions.
Each segment is to some extent an independent compartment, because it contains nodes of the nervous system and excretory organs ( paired nephridia) and gonads. Each segment may have lateral outgrowths with primitive limbs - parapodia, armed with setae.
The secondary body cavity, or coelom, is filled with fluid, the pressure of which maintains the shape of the worm's body and serves as a support when moving, that is, the coelom serveshydroskeleton . Coelomic fluid carries nutrients, accumulates and removes substances harmful to the body, and also removes sexual products.
The musculature consists of several layers of longitudinal and circular muscles. Breathing is carried out through the skin. The nervous system consists of a “brain” formed by paired ganglia and a ventral nerve cord.
The closed circulatory system consists of abdominal and dorsal vessels connected in each segment by small annular vessels. Several of the thickest vessels in the anterior part of the body have thick muscular walls and act as “hearts.” In each segment, blood vessels branch, forming a dense capillary network.
Some annelids are hermaphrodites, while others have different males and females. Development is direct or with metamorphosis. Asexual reproduction (by budding) also occurs.
Their sizes range from a few millimeters to 3 m. There are 7,000 species of annelids in total.
Interactive lesson-simulator (Go through all pages of the lesson and complete all tasks)
Annelids - progressive group of worms. Their body consists of many ring segments. By body cavity is divided by internal parts partitions according to the number segments. Annelids have various organ systems. They have the circulatory system appears and paired organs of movement - a prototype of future limbs .
Main characteristic features annelids are:
Secondary, or coelomic, body cavity;
The appearance of the circulatory and respiratory systems;
Excretory system in the form of metanephridia.
a brief description of
|
Habitat |
Marine and freshwater, terrestrial and underground animals |
|
Body structure |
The body is elongated, worm-shaped, metameric in structure. Bilateral symmetry. Three-layer. Polychaetes have parapodia |
|
Coverings of the body |
Cuticle. Each segment has 8 or more setae for locomotion. There are many glands in the skin. In the skin-muscle sac, longitudinal and transverse muscles |
|
Body cavity |
The secondary body cavity - the whole, is filled with fluid that acts as a hydroskeleton |
|
Mouth, pharynx, esophagus, crop, stomach, intestines, anus |
|
|
Respiratory system |
Breathing through the entire surface of the body. Polychaetes have external gills |
|
Closed. One circle of blood circulation. There is no heart. Blood is red |
|
|
excretorysystem |
A pair of tubes in each metamere - metanephridia |
|
Nervous system |
Peripharyngeal nerve ring, ventral scalene nerve cord |
|
Sense organs |
Tactile and photosensitive cells; polychaetes have eyes |
|
Reproductive system and development |
Hermaphrodites. Cross fertilization. Development without metamorphosis. Fertilization is internal. Polychaete dioecious, external fertilization, development with metamorphosis |
The main classes of the type are Oligochaetes, Polychaetes, Leeches.
A.G. Lebedev “Preparing for the biology exam”
Main aromorphoses:
1. The appearance of a secondary body cavity-coelom.
2. Metomeric body structure.
3. The appearance of a closed circulatory system.
4. Excretory system of metonephridial type.
5. More highly organized nervous system and sense organs.
6. The emergence of respiratory organs.
7. The emergence of organs of movement.
General characteristics of annelids.
A large group of animals, including about 12k species.
They live mainly in the seas, as well as in fresh water oh and on land.
They are characterized by the following organizational features:
1. Metamiria (correct repetition of similar organs along the axis of the animal’s body). Outwardly, this is expressed in the fact that the entire body of the worm is divided by constrictions into separate segments (rings). Therefore, annelids are also called ringworms. Along with the external one, there is an internal segmentation, which is expressed in the repetition of many internal organs.
As a result, each segment, to some extent, represents an independent unit of the entire system.
Metamiria can be homonomous (all segments are the same) and heteronomous (if the segments are different from each other). Annelids are characterized mainly by homonomic segmentation.
Metamiria arose with the need to increase mobility by building muscles and muscle mass in length. However, this raises a new problem - managing and increasing the number of organs to ensure full functioning.
Thus, biological meaning metaworld as a whole is:
a) solving the problem of body control;
b) all vital processes are enhanced, since the same organs are repeated;
c) the margin of biological strength increases;
d) due to the presence of metomerism, annelids are capable of regeneration.
From an evolutionary point of view, segmentation opens the way for cell specialization and differentiation, which leads to reduced energy costs. And the emergence of heteronomous segmentation. The emergence of heteronomous segmentation is observed in some annelids, for example, in nereids.
2. For the first time, ringlets show a process of cephollization, that is, the formation of the head section.
3. The skin-muscle sac is well developed.
Due to this, annelids perform complex wave-like and restatic movements. An important role is played by the lateral outgrowths of the body-paropodia, which are organs of movement. Parapodia are another way of increasing the mobility of annelids. The parapodia are best developed in polychaete ringlets.
In oligochaete worms and leeches, paropodia have undergone reduction to varying degrees.
4. Annelids have a secondary body cavity called the coelom. Unlike the primary body cavity of the schizocoel, the coelom is lined with a special coelomic epithelium. In fact, it is an internal organ and has its own walls.
The coelom, like the entire body of annelids, is segmented.
5. The digestive system is well differentiated into sections.
Some species have salivary glands. The anterior and posterior sections of the intestine are of ectodermal origin, the middle section is of endodermal origin.
6. The main excretory organs are metanephridia. This is an open excretory system associated with the coelom and providing not only the function of excretion, but also the regulation of water regime.
Metanephridia are arranged in segments. In this case, the metanephridium funnel is located in one segment, and the excretory canal opens in the adjacent segment.
7. Most annelids have a closed circulatory system. This means that blood flows only through the vessels and there is a network of capillaries between the arteries and veins.
8. Breathing occurs through the skin, but some representatives have new respiratory organs - gills.
The dorsal antennae-parapodium turns into a gill.
9. The nervous system consists of paired dorsal ganglia and the ventral nerve cord.
The paired dorsal ganglia along the brain are divided into anterior, middle and posterior ganglia. This is a change from previous groups of worms.
10. The sense organs are better developed than those of flatworms and roundworms.
Many ringlets have eyes that are capable of accommodation. Organs of touch, organs of balance (statocysts), organs of chemical sense, and in some also organs of hearing, arranged like locators.
Annelids are mostly dioecious, but hermaphroditism is often observed. Development often occurs with metamorphosis. A typical sea ringlet larva is called a trochophore (cilia bearing).
Thus, annelids exhibit progressive organizational features: the presence of a coelom, metamerism of structure, the appearance of a circulatory system, metonephridia, a more highly organized nervous system and sensory organs. Along with these features, there are signs that bring them closer to lower worms (primitive characters: the trochophore larva has a primary body cavity, protonyphridia, an orthogonal nervous system, and early stages development, cecum).
These features are also found in adult ringlets from primitive groups.
The type includes 3 classes:class polychaetes or polychaete worms, class olegochaetes or oligochaete worms, class leeches.
Class Polychaetes (Polychaetes)
The central class of annelids, distinguished by the largest number species.
Some annelids swim freely in water, for example, nereids, while others burrow into the sand, for example, sandworm. There are sessile polychaetes living in calcareous tubes, for example, serpulids and aphrodites crawling along the bottom.
External structure of polychaetes.
The body consists of a head section, a segmented trunk and an anal lobe (pegidium).
The head section is formed by the head lobe, prostomium and oral segment - peristomium. Many polychaetes have eyes and sensory appendages on their heads. For example, a nereid has 2 pairs of ocelli, tentacles, two-segmented palps and olfactory pits. On the peristomium there is a mouth below, and on the sides there are several pairs of antennae. The body consists of segments, the number of which can reach up to 800.
In freely mobile vagrant polychaetes, homonomic segmentation is best expressed. Heteronomous segmentation is characteristic of sessile and partly burrowing forms.
On the body segments there are paropodia, with the help of which polychaetes swim, crawl or burrow into the ground. Each paropodium consists of a basal part and two lobes: dorsal (notopodia) and ventral (neuropodia). At the base of the paropodium there is a dorsal barbel on the dorsal side, and a ventral barbel on the ventral side. In some species, the dorsal barbel of the paropodium develops into feathery gills. Paropodia armed with tufts of bristles consisting of organic matter close to chitin.
One of the setae of each lobe is the most developed and is called the acicula. This is the supporting bristle. Muscles that move the entire bundle are attached to its base. In some species leading a burrowing or attached lifestyle, paropodia are reduced. The anal lobe does not bear any appendages.
Skin-muscle bag.
The body of polychaetes is covered with a monosyllabic epithelium, which secretes a thin cuticle onto the surface. The epithelium may be ciliated. It is rich in unicellular glands that secrete mucus and substances from which many sessile polychaetes build their tubes. Under the epithelium lies the circular and longitudinal muscles. The longitudinal muscles form 4 highly developed ribbons: 2 on the dorsal side and 2 on the abdominal side.
In addition, there are oblique muscles that run obliquely from the dorsal part of the skin-muscular sac to the abdominal part. Secondary body cavity - whole. Essentially, it is a sac filled with cavity fluid, which is separated from all tissues and organs by coelomic epithelium of mesodermal origin.
Thus, longitudinal muscles, intestines and internal organs covered with single-layer epithelium.
Another feature of the coelom in polychaetes is its metomeric structure.
This means that each segment of the polychaete’s body essentially has its own cavity, completely separated from the cavities of neighboring segments by special partitions consisting of double-layer epithelium.
In addition, the coelomic cavity in each segment is completely divided into right and left halves by a longitudinal, also two-layer septum. The intestine runs inside this septum, and above and below the intestine, also inside this septum, are the dorsal and abdominal blood vessels.
That is, in each internal segment of polychaetes there are 2 coelomic sacs. The epithelial walls of these sacs are closely adjacent on one side to the muscles of the skin-muscular sac, and on the other to the intestines and each other, covering the intestine and blood vessels on both sides. This part of the walls of the coelomic sacs is called the dorsal and ventral mesentery or mesentery.
Overall it performs several functions:
Previous20212223242526272829303132333435Next
SEE MORE:
1. Let's continue filling out the table.
2. Let us explain the above statement.
Annelids for the first time have a secondary body cavity and cellular structure skin. A circulatory system appears in the internal structure. The excretory system is represented by more developed metanephridia. Most ringlets are free-living, some have something like legs - parapodia. Everyone has bilateral symmetry. There are sense organs.
Let's write about protective function partitions.
Each segment of annelids is separated by a septum and has a full set of nerve ganglia, nephridia, annular vessels and gonads. If the integrity of one segment is violated, this affects the life of the worm to a small extent.
4. Let us list the structural features of the rings.
Some types of ringbills have parapodia and setae for locomotion.
Those species that do not have parapodia have bristles or their body is covered with mucus for better gliding. Muscular system All rings are represented by circular and longitudinal muscles.
5. Let's finish the diagrams.
a) Digestive system of ringlets
b) Nervous system of ringlets
c) Sense organs of rings
6.
Let's write about the division of the ring body.
Regeneration may occur and the worm will restore the lost parts. That is, asexual reproduction will occur.
7. Let's write an answer about the formation of the belt.
Maybe. In some polychaete worms living in the seas and belonging to the phylum Annelids, reproduction occurs in water, fertilization is external.
But in most ringlets, reproduction occurs with the help of a belt.
8. Let's explain the relationship.
There is a direct relationship between the number of eggs laid and care for the offspring. Some polychaetes lay a few eggs, and the female guards them. This means that Annelids are more advanced than previous types of worms.
Let us list the feeding methods of polychaetes.
Among polychaete worms there are predators that feed on small marine animals. There are omnivores that filter water and eat plants.
10. Let's finish the sentences.
The development of polychaetes occurs with alternation of life forms.
Their larvae do not resemble adults. Each life form performs various functions: reproduction, resettlement, self-preservation. Some polychaetes show care for their offspring.
11. Let's finish the diagram.
The meaning of polychaetes in nature
Filter the water.
2. They are fish food.
3. They feed on the remains of dead animals.
12. Let’s write down the differences in the nutrition of different worms.
Oligochaete worms feed organic substances from plant remains of the soil, and among polychaetes there are also predators, omnivores, and herbivores.
Let's write down the common adaptations of protozoa and oligochaetes.
To withstand unfavorable conditions, many protozoa form a cyst, and oligochaetes form a protective capsule, and enter diapause. These formations are similar in their functions.
14. Let us indicate in the figure the structure of an earthworm. Let's draw a conclusion.
Conclusion: The primary body cavity is a supporting one. It contains a liquid that gives the worm's body elasticity.
Let us list the features of leeches.
1) Constant number of body segments (33)
2) The presence of suction cups for attachment to the victim’s body or substrate.
3) Lack of bristles on the body.
4) All leeches live in an aquatic environment.
16. Let's name the types of food of leeches.
17. Let's determine the type and class of worms. 
Let us explain the peculiarity of leeches.
Leeches have a better developed nervous system.
19. Let us explain the statement.
The statement is not true. Leeches are very sensitive to the purity of water and die if it is polluted. Oligochaetes withstand water pollution and can live for a long time in such reservoirs.
Will write an answer about hirudia.
Hirudin is necessary to prevent blood clotting in the wound of the victim and in the stomach of the leech itself. If it is not produced, the leech will not be able to feed, as the blood will clot.
21. Let's name the role of leeches in medicine.
Leeches are used in medicine to reduce blood pressure in cases of hypertension and the threat of hemorrhage and stroke.
Let us indicate the characteristics of the classes of annelids.
Classes of the type Annelids.
A - 1, 2, 8, 10, 16
B - 4, 6, 11, 12, 17
B - 3, 5, 7, 9, 14, 15
Let's write down the answers to crossword No. 1.
Answers:
1. Capsule
2. Belt
3. Polychaetes
4. Cavity
5. Chain
6. Oligochaetes
7. Tapeworm
8.
Breath
Keyword: rings
Type Annelids
Aromorphoses type:
1) the presence of movement organs;
2) the appearance of respiratory organs and a closed circulatory system;
3) secondary body cavity.
The phylum Annelids includes about 8,000 species of higher worms, which have a much more complex organization than previous types.
Main characteristics of the type:
The body of worms is composed of a head lobe (prostomium), a segmented body, and a posterior anal lobe (pygidium). The sensory organs are located on the head lobe.
There is a well-developed skin-muscle sac.
3. In annelids, for the first time, a secondary body cavity or coelom appears (the space between the body wall and internal organs with its own epithelial lining, which separates the cavity fluid from all surrounding tissues and organs). It is divided into cameras according to external segmentation.
4. The oral opening lies on the ventral side of the first segment of the body.
The digestive system is made up of oral cavity, pharynx, midgut and hindgut, opening with the anus at the end of the anal lobe.
5. The majority have a well-developed closed circulatory system.
6. Excretory functions are performed by metanephridia.
Metanephridia are open excretory organs, in contrast to closed protonephridia.
Metanephridia begins with a more or less expanded funnel - nephrostomy, seated with cilia and opening into the cavity of the segment. The nephridial canal begins from the nephrostomy, which passes into the next segment. Here the canal forms a complex ball and opens with an excretory opening to the outside.
The nervous system consists of paired supra- and subpharyngeal ganglia connected to the peripharyngeal nerve ring and the ventral nerve cord. The latter is a pair of longitudinally close trunks, forming nerve nodes in each segment.
The most primitive annelids are dioecious; In some cases, hermaphroditism appears for the second time.
9. Crushing of the egg follows a spiral type.
10. In the lower representatives of the type, development proceeds with metamorphosis; the typical larva is a trochophore.
According to the most common view, annelids evolved from lower, unsegmented worms.
The phylum is divided into three classes - Oligochaetes (representative of the earthworm), Polychaetes (Nereis, sandworm) and Leeches.
It is believed that in the course of evolution, polychaetes gave rise to arthropods.
1. Flatworms:
a) two-layer animals;
b) three-layer animals.
Specify the excretory organs of the bovine tapeworm:
a) protonephridia;
b) metanephridia;
3. Intermediate host of the liver fluke:
a) cow;
b) small pond snail;
c) person.
4. The complication of roundworms compared to flatworms is associated with the appearance of:
a) three-layer body structure;
b) nervous system;
c) hermaphroditism;
d) through the digestive system.
a) type Roundworms;
b) class Tapeworms;
c) class Flukes?
How many layers of muscle do roundworms have?
a) one; b) two; at three o'clok.
7. How many segments does an earthworm have in its body?
a) 20-30; 6)250; c) up to 180; d) 50.
8. Among annelids, only the following have true parapodia:
a) oligochaetes; b) polychaetes; c) leeches.
Polychaetes are characterized by:
a) dioeciousness;
b) hermaphroditism;
c) budding.
10. What is the body cavity of the Nereid:
a) intestinal; b) primary;
c) secondary; d) filled with parenchyma
Literature
R.G. Zayats, I.V. Rachkovskaya et al. Biology for applicants. Minsk, Unipress, 2009, p. 129-177.
2. L.N. Pesetskaya. Biology.
Minsk, “Aversev”, 2007, pp. 195-202.
3. N.D. Lisov, N.A. Lemeza et al. Biology. Minsk, “Aversev”, 2009, pp. 169-188.
4. E.I. Shepelevich, V.M. Glushko, T.V. Maksimova. Biology for schoolchildren and applicants. Minsk, “UniversalPress”, 2007, p.404-413.
The type of annelids, uniting about 12,000 species, represents, as it were, a node in the family tree of the animal world. According to existing theories, annelids originate from ancient ciliated worms (turbellar theory) or from forms close to ctenophores (trochophore theory). In turn, arthropods arose from annelids in the process of progressive evolution. Finally, in their origin, annelids are related by a common ancestor to mollusks. All this shows that great importance, which has the type in question for understanding the phylogeny of the animal world. From a medical point of view, annelids are of limited importance. Only leeches are of particular interest.
General characteristics of the type
The body of annelids consists of a head lobe, a segmented body and a posterior lobe. Segments of the body throughout almost the entire body have external appendages similar to each other and a similar internal structure. Thus, the organization of annelids is characterized by repeatability of structure, or metamerism.
On the sides of the body, each segment usually has external appendages in the form of muscular outgrowths equipped with bristles - parapodia - or in the form of bristles. These appendages are important in the movement of the worm. Parapodia in the process of phylogenesis gave rise to the limbs of arthropods. At the head end of the body there are special appendages - tentacles and sticks.
A skin-muscular sac is developed, which consists of a cuticle, an underlying layer of skin cells and several layers of muscles (see Table 1) and a secondary body cavity, or whole, in which the internal organs are located. The coelom is lined with peritoneal epithelium and divided by septa into separate chambers. Moreover, in each body segment there is a pair of coelomic sacs (only the head and posterior lobes are devoid of coelom).
The coelomic sacs in each segment are placed between the intestine and the body wall and are filled watery liquid, in which amoeboid cells float.
Overall it performs a supporting function. In addition, nutrients enter the coelomic fluid from the intestines, which are then distributed throughout the body. As a whole they accumulate harmful products metabolism, which are removed by the excretory organs. Male and female gonads develop in the walls of the coelom.
The central nervous system is represented by the suprapharyngeal ganglion and the ventral nerve cord. Nerves from the sensory organs pass to the suprapharyngeal node: eyes, balance organs, tentacles and palps. The abdominal nerve cord consists of nodes (one pair in each body segment) and trunks connecting the nodes to each other. Each node innervates all organs of a given segment.
The digestive system consists of the foregut, middle and hindgut. The foregut is usually divided into a number of sections: the pharynx, esophagus, crop and gizzard. The mouth is located on the ventral side of the first body segment. The hindgut opens with the anus on the posterior lobe. The intestinal wall contains muscles that move food along.
The excretory organs - metanephridia - are paired tubular organs, metamerically repeated in body segments. Unlike protonephridia, they have a through excretory canaliculus. The latter begins with a funnel that opens into the body cavity. Cavity fluid enters the nephridium through the funnel. A tubule of nephridium extends from the funnel, sometimes opening outward. Passing through the tubule, the liquid changes its composition; the final products of dissimilation are concentrated in it, which are released from the body through the external pore of nephridium.
For the first time in the phylogenesis of the animal world, annelids have a circulatory system. The main blood vessels run along the dorsal and ventral sides. In the anterior segments they are connected by transverse vessels. The dorsal and anterior annular vessels are capable of contracting rhythmically and perform the function of the heart. In most species, the circulatory system is closed: blood circulates through a system of vessels, nowhere interrupted by cavities, lacunae or sinuses. In some species the blood is colorless, in others it is red due to the presence of hemoglobin.
Most species of annelids breathe through skin rich in blood capillaries. A number of marine forms have specialized respiratory organs - gills. They usually develop on the parapodia or palps. Vessels carrying venous blood approach the gills; it is saturated with oxygen and enters the body of the worm in the form of arterial blood. Among annelids there are dioecious and hermaphroditic species. The gonads are located in the body cavity.
Annelids have the highest organization compared to other types of worms (see Table 1); For the first time, they have a secondary body cavity, a circulatory system, respiratory organs, and a more highly organized nervous system.
| Table 1. Characteristics various types worms | ||||||
| Type | Skin-muscle bag | Digestive system | Circulatory system | Reproductive system | Nervous system | Body cavity |
| Flatworms | Includes layers of longitudinal and circular muscles, as well as bundles of dorso-abdominal and diagonal muscles | From the ectodermal foregut and endodermal midgut | Not developed | Hermaphrodite | Paired brain ganglion and several pairs of nerve trunks | Absent, filled with parenchyma |
| Roundworms | Only longitudinal muscles | From the ectodermal anterior and posterior gut and the endodermal midgut | Same | Dioecious | Peripharyngeal nerve ring and 6 longitudinal trunks | Primary |
| From the external circular and internal longitudinal muscles | From the ectodermal foregut and hindgut and the endodermal midgut | Well developed, closed | Dioecious or hermaphrodite | Paired medullary ganglion, peripharyngeal nerve ring, ventral nerve cord | Secondary | |
|
Animals belonging to the type of annelids, or ringworms, are characterized by:
Annelids live in fresh and sea waters, as well as in the soil. Several species live in the air. The main classes of the annelid phylum are:
Class polychaete ringletsFrom the point of view of phylogeny of the animal world, polychaetes are the most important group annelids, since their progressive development is associated with the emergence of higher groups of invertebrates. The body of polychaetes is segmented. There are parapodia consisting of dorsal and ventral branches, each of which carries an antennae. The muscular wall of the parapodia contains thick supporting setae, and tufts of thin setae protrude from the apex of both branches. The function of parapodia is different. Typically these are locomotor organs involved in the movement of the worm. Sometimes the dorsal barbel grows and turns into a gill. The circulatory system of polychaetes is well developed and always closed. There are species with cutaneous and gill respiration. Polychaetes are dioecious worms. They live in the seas, mainly in the coastal zone. A typical representative of the class is the Nereid (Nereis pelagica). It is found in abundance in the seas of our country; leads a bottom lifestyle, being a predator, it captures prey with its jaws. Another representative, the sandbill (Arenicola marina), lives in the seas and digs holes. It feeds by passing through its digestive tract marine silt Breathes through gills. Class oligochaete ringletsOligochaetes originate from polychaetes. The external appendages of the body are setae, which sit directly in the body wall; no parapodia. The circulatory system is closed; skin breathing. Oligochaete ringlets are hermaphrodites. The vast majority of species are inhabitants of fresh water and soil. A typical representative of the class is the earthworm (Lumbricus terrestris). Earthworms live in soil; During the day they sit in holes, and in the evening they often crawl out. Rummaging in the soil, they pass it through their intestines and feed on the plant debris contained in it. Earthworms play a large role in soil-forming processes; they loosen the soil and promote its aeration; they drag leaves into holes, enriching the soil with organic matter; deep layers of soil are removed to the surface, and superficial layers are carried deeper. The structure and reproduction of an earthworm The earthworm has an almost round body in cross section, up to 30 cm long; have 100-180 segments or segments. In the anterior third of the earthworm's body there is a thickening - the girdle (its cells function during the period of sexual reproduction and egg laying). On the sides of each segment there are two pairs of short elastic setae, which help the animal when moving in the soil. The body is reddish-brown in color, lighter on the flat ventral side and darker on the convex dorsal side. Characteristic feature internal structure is that earthworms have developed real tissues. The outside of the body is covered with a layer of ectoderm, the cells of which form the integumentary tissue. The skin epithelium is rich in mucous glandular cells. Under the skin there is a well-developed muscle, consisting of a layer of circular muscles and a more powerful layer of longitudinal muscles located under it. When the circular muscles contract, the animal’s body elongates and becomes thinner; when the longitudinal muscles contract, it thickens and pushes the soil particles apart.
The digestive system begins at the front end of the body with the mouth opening, from which food enters sequentially into the pharynx and esophagus (in earthworms, three pairs of calcareous glands flow into it, the lime coming from them into the esophagus serves to neutralize the acids of rotting leaves on which the animals feed). Then the food passes into the enlarged crop, and a small muscular stomach (the muscles in its walls help grind the food). The midgut stretches from the stomach almost to the posterior end of the body, in which, under the action of enzymes, food is digested and absorbed. Undigested residues enter the short hindgut and are thrown out through the anus. Earthworms feed on half-rotten remains of plants, which they swallow along with the soil. As it passes through the intestines, the soil mixes well with organic matter. Earthworm excrement contains five times more nitrogen, seven times more phosphorus and eleven times more potassium than regular soil. The circulatory system is closed and consists of blood vessels. The dorsal vessel stretches along the entire body above the intestines, and below it - the abdominal vessel. In each segment they are united by a ring vessel. In the anterior segments, some annular vessels are thickened, their walls contract and pulsate rhythmically, thanks to which blood is driven from the dorsal vessel to the abdominal one. The red color of blood is due to the presence of hemoglobin in the plasma. Most annelids, including earthworms, are characterized by cutaneous respiration; almost all gas exchange is provided by the surface of the body, therefore earthworms are very sensitive to soil moisture and are not found in dry areas. sandy soils, where their skin soon dries out, and after rains, when there is a lot of water in the soil, they crawl to the surface. The excretory system is represented by metanephridia. Metanephridia begins in the body cavity with a funnel (nephrostom) from which a duct emerges - a thin loop-shaped curved tube that opens outward with an excretory pore in the side wall of the body. In each segment of the worm there is a pair of metanephridia - right and left. The funnel and duct are equipped with cilia, causing the movement of excretory fluid. The nervous system has a structure typical of annelids (see Table 1), two abdominal nerve trunks, their nodes are interconnected and form the abdominal nerve chain. The sense organs are very poorly developed. The earthworm does not have real organs of vision; their role is played by individual light-sensitive cells located in skin. The receptors for touch, taste, and smell are also located there. Like hydra, earthworms are capable of regeneration. Reproduction occurs only sexually. Earthworms are hermaphrodites. At the front of their body are the testes and ovaries. Earthworms undergo cross fertilization. During copulation and oviposition, girdle cells on the 32-37th segment secrete mucus, which serves to form an egg cocoon, and protein fluid to nourish the developing embryo. The secretions of the girdle form a kind of mucous muff. The worm crawls out of it with its back end first, laying eggs in the mucus. The edges of the muff stick together and a cocoon is formed, which remains in the earthen burrow. Embryonic development of eggs occurs in a cocoon, and young worms emerge from it. Earthworm tunnels are located mainly in the surface layer of soil to a depth of 1 m; in winter they descend to a depth of 2 m. Through the burrows and tunnels of earthworms, atmospheric air and water penetrate into the soil, necessary for plant roots and the vital activity of soil microorganisms. During the day, the worm passes through its intestines as much soil as its body weighs (on average 4-5 g). On each hectare of land, earthworms process an average of 0.25 tons of soil every day, and over the course of a year they throw out 10 to 30 tons of soil they processed to the surface in the form of excrement. In Japan, specially bred breeds of fast-reproducing earthworms are bred and their excrement is used for biological soil cultivation. The sugar content of vegetables and fruits grown in such soil increases. Charles Darwin was the first to point out the important role of earthworms in soil formation processes. Annelids play a significant role in the nutrition of bottom fish, since in some places worms make up up to 50-60% of the biomass of the bottom layers of reservoirs. In 1939-1940 The Nereis worm was transplanted from the Azov Sea to the Caspian Sea, which now forms the basis of the diet of sturgeon fish in the Caspian Sea.
Leech classThe body is segmented. In addition to true metamerism, there is false ringing - several rings in one segment. There are no parapodia or setae. The secondary body cavity was reduced; instead there are sinuses and gaps between organs. The circulatory system is not closed; the blood passes only part of its path through the vessels and pours out of them into the sinuses and lacunae. There are no respiratory organs. The reproductive system is hermaphroditic. Medical leeches are specially bred and then sent to hospitals. Used, for example, in the treatment of eye diseases associated with enlargement intraocular pressure(glaucoma), with cerebral hemorrhage and hypertension. For thrombosis and thrombophlebitis, hirudin reduces blood clotting and promotes the dissolution of blood clots. |
1. In annelids, a circulatory system appears for the first time. 2. The circulatory system serves to transport oxygen and nutrients to all organs of the animal. 3. Annelids have two main blood vessel. Through the abdominal vessel, blood moves from the anterior end of the body to the posterior. 4. Blood moves through the spinal vessel from the posterior end of the body to the anterior. 5. The dorsal vessel passes above the intestine, the abdominal vessel - below it. In each segment, the dorsal and abdominal vessels are connected to each other by annular vessels.
Circulatory system 6. Annelids do not have a heart. Several thick annular vessels have muscular walls, due to the contraction of which blood moves. From the main vessels, thinner vessels depart, which then branch into the finest capillaries. Oxygen enters the capillaries from skin epithelium and nutrients from the intestines. And from other similar capillaries that branch in the muscles, “waste” is released. Thus, the blood moves all the time through the vessels and does not mix with the cavity fluid. Such a circulatory system is called closed. 7. There is an iron-containing protein in the blood, similar to hemoglobin.
Circulatory system of annelids 1. Annelids have a circulatory system for the first time. 2. The circulatory system is closed 3. two main blood vessels: abdominal and dorsal. They are connected at each segment by an annular vessel 4. There is no true heart
The circulatory system of mollusks: Unclosed (blood from the vessels enters the body cavity) A heart has appeared, which has increased the speed of blood circulation, which significantly increased the intensity metabolic processes. Three-chambered or two-chambered heart (1 or 2 atria and a ventricle) the aorta departs from the heart, it branches into arteries Colorless blood is saturated with oxygen in the lung (gills) and returns to the heart through the veins Functions: blood carries oxygen and takes in carbon dioxide
Unlike other mollusks, cephalopods have an almost closed circulatory system. In many places (skin, muscles) there are capillaries through which arteries pass directly into veins. A highly developed circulatory system allows cephalopods to reach gigantic sizes. Only in the presence of a capillary system is the existence of very large animals possible, since only in this case is a complete supply of oxygen and nutrients to massive organs ensured. The blood is driven by three hearts. 1. The main one, consisting of a ventricle and two atria (the nautilus has four atria). The main heart pumps blood throughout the body. 2. And two gills. 3. Rhythmic contractions of the gill hearts push venous blood through the gills, from where it, enriched with oxygen, enters the atrium of the main heart. The heart rate depends on the water temperature. For example, an octopus at a water temperature of 22°C has a heart rate of 40-50 beats per minute. 4. There are special vessels to supply blood to the head. The blood of cephalopods is blue due to the presence of the respiratory pigment hemocyanin, which contains copper. Hemocyanin is produced in special gill glands.
The circulatory system in arthropods is not closed and is represented by the heart and large vessels, from which hemolymph (a fluid much like the blood of vertebrates) pours into the body cavity, washes the internal organs and returns to the heart. 1. The heart is capable of rhythmic contractions. Hemolymph enters it from the body cavity through the lateral openings, ostia, and washes the internal organs, supplying them with nutrients. 2. In crustaceans, hemolymph also performs respiratory function. It contains oxygen-carrying substances - red hemoglobin or blue hemocyanin. There are special gill vessels for this purpose.
Circulatory system 1. When the heart contracts, the ostial valves close. 2. And the blood, moving through the arteries, enters the body cavity. Here it supplies oxygen and nutrients to the internal organs. 3. Saturates carbon dioxide and products of exchange. 4. Blood then flows to the gills. 5. Gas exchange occurs there, and the blood, freed from carbon dioxide, is again saturated with oxygen. 6. After this, the blood enters the relaxed heart through the open ostia.
Circulatory system The circulatory system is not closed. Blood practically does not participate in the transfer of oxygen in insects. the long, tubular heart of insects is located on the dorsal side of the abdomen and is divided into several chambers; each chamber has openings with valves - ostia. Through them, blood from the body cavity enters the heart. adjacent chambers are connected to each other by valves that open only forward. Consecutive contraction of the heart chambers from the back to the front ensures the movement of blood.
Lancelet Circulatory system: closed, no heart, contracting walls of the abdominal aorta Function: blood carries oxygen and nutrients throughout the body, takes away decay products
Circulatory system of fish The circulatory system is closed, one circle of blood circulation, the heart is two-chambered (consists of a thin-walled atrium and a muscular ventricle) Deoxygenated blood it first collects in the venous sinus - an expansion that collects blood from the venous vessels, then enters the atrium and is pushed out of the ventricle. From the heart, venous blood flows through the abdominal aorta to the gills, arterial blood collects in the dorsal aorta. From all organs, venous blood enters the common venous sinus through the vessels.
Circulatory system of an amphibian Circulatory system. Two circles of blood circulation (large and small). Since the lungs have appeared, a pulmonary (lesser) circulation occurs. The heart of amphibians becomes three-chambered (formed by two atria and one ventricle), three pairs of arterial arches extend from it. Metabolism is not yet very intense; amphibians are poikilothermic (cold-blooded) animals.
The circulatory system of an amphibian Arterial blood enters the left atrium from the lungs through the pulmonary veins, and mixed blood enters the right atrium, since venous blood enters the vena cava from the internal organs, and the cutaneous veins bring arterial blood. In the ventricle, the blood is only partially mixed due to the presence of special separation mechanisms (various processes and the spiral valve of the conus arteriosus).
Circulatory system Big circle blood circulation From the ventricle, blood enters three pairs of arterial vessels. When the ventricle contracts, venous blood is first pushed out, which fills the first two pairs of arteries. Blood with the maximum oxygen content enters the third pair of arteries, from which they branch carotid arteries supplying blood to the brain. Then venous blood (from the internal organs through the vena cava) and arterial blood (through the cutaneous veins) enter the right atrium.
Circulatory system Pulmonary circulation. The pulmonary arteries carry oxygen-poor blood to the lungs, where gas exchange occurs, then the pulmonary veins carry arterial blood to the left atrium. Large branches depart from each pulmonary artery - cutaneous arteries, which carry blood to the skin, where it is oxidized and then enters the right atrium. Red blood cells in amphibians are large, biconvex, and have a nucleus. Metabolism is higher than that of fish, but not high enough to maintain constant temperature body
Circulatory system There is a further separation of arterial and venous blood flow due to the appearance of an incomplete septum in the ventricle of the heart. The septum partially prevents the mixing of arterial and venous blood. Three vessels independently branch off from the ventricle: the pulmonary artery, which carries venous blood to the lungs, and the right and left aortic arches.
Circulatory system The systemic circulation begins with the aortic arches. The right aortic arch emerges from the left side of the ventricle and carries arterial, oxygenated blood. The carotid arteries, which carry blood to the brain, depart from it and subclavian arteries, supplying blood to the forelimbs. The left aortic arch originates from the middle part of the ventricle and carries mixed blood. Both arches merge into the dorsal aorta, which supplies blood to the rest of the organs.
Circulatory system The small circle begins with the pulmonary artery, which arises from right side ventricle Venous blood is delivered to the lungs, gas exchange occurs there, and arterial blood returns through the pulmonary veins to the left atrium. Although the circulatory system is more advanced than that of amphibians, the metabolism is insufficient to maintain a constant body temperature, so reptiles do not have a constant body temperature and are poikilothermic.
Circulatory system. The heart becomes four-chambered, the septum divides the heart into two parts - right and left. Each part of the heart consists of an atrium and a ventricle. Venous blood returns to the right half of the heart through the vena cava (superior and inferior) from the systemic circulation. Pulmonary circulation. When the right ventricle contracts, venous blood flows through pulmonary arteries into the lungs, where gas exchange occurs, and arterial blood returns through the pulmonary veins from the pulmonary circulation to the left atrium.
Circulatory system Great circle. Blood leaves the left ventricle through the right aortic arch. The carotid arteries, which carry blood to the head, are separated from it, the subclavian arteries - to upper limbs. The right aortic arch passes into the dorsal aorta, supplying blood to the internal organs. The venous blood then collects in the vena cava and enters the right atrium. Unlike the circulatory system of reptiles, in birds blood from the heart to the organs in a large circle flows not through two arteries (the left and right aortic arches), but only through the right one. The oxygen capacity of the blood in birds is 2 times higher than in reptiles. The average body temperature of birds is about 42 degrees.
The circulatory system in the right half of the heart is venous, while in the left half it is arterial, i.e. there is no mixing of blood. The pulmonary circulation begins in the right ventricle, venous blood is carried through the pulmonary arteries to the lungs, where gas exchange occurs, and arterial blood through the pulmonary veins enters the left atrium. The systemic circulation begins in the left ventricle, the blood is ejected into the left aortic arch. Arteries supply blood to all internal organs. Venous blood enters the right atrium through the superior and inferior vena cava.
Loading...