Ringed worms, also called chainmets or annelids, include a huge number of animal species. Their body consists of numerous recurring rings (segments), which is why they received such a name. The general characteristics of the ringed worms unites about 18 thousand different species of them. They live on land in the soil and on the surface in tropical rain forests, in the sea water of the oceans and the fresh water of the rivers.
Classification
Annelides are a type of invertebrate animals. Their group is called primary movers. Biologists distinguish 5 classes of annelids:
- belt, or leeches,
- small-necked (the most famous representative of this class is the earthworm),
- mnogoshchetkovye (sand and Nereid),
There are also ectoparasites and mutualists. Among the ringed worms can be seen predators and blood-sucking individuals, scavengers and representatives of filter feeders. Especially a lot of representatives of this large type of animals distributed in the depths of the ocean. They are found at a depth of 11 km and at all latitudes of the planet. At the bottom of the ocean their density is 1 square. meter seabed up to 600,000 individuals.
The important role of such worms
Considering the general characteristics of annelids, you understand their important biological role in the processing and aeration of the soil. Earthworms loosen the soil, which is beneficial for the entire surrounding vegetation of the planet. To understand how many there are on earth, imagine that in 1 square. meter of soil aeration spend from 50 to 500 annelid. This increases the yield of agricultural land.
Ringed worms are one of the main links in the food chain of an ecosystem both on land and in the oceans. They feed and fish, and turtles, birds and other animals. Even people use them as top dressing when breeding commercial fish species in both fresh and marine waters. Fishermen put the worms in as bait hook when fishing with a fishing rod.
Everyone knows about the value of medical leeches that suck blood from diseased places, saving a person from hematomas. People understood their therapeutic value long ago. Apply leeches with hypertension, increased blood clotting. Leeches have the ability to produce hirudin. This is a substance that reduces blood clotting and dilates the blood vessels of a person.
Origin
Studying the general characteristics of annelids, scientists have established that they are already known from the Cambrian period. Considering their structure, biologists came to the conclusion that they were descended from a more ancient type of lower flatworms. The similarity is evident in certain features of the structure of the body.
Scientists believe that the first group appeared polychaete worms. In the process of evolution, when this type of animal came to life on the surface and in freshwater bodies, malleech, later called leeches, appeared.
Describing the general characteristics of annelids, we note that this is the most progressive type of worms. It was their first birthplace of the circulatory system and the ring-shaped body. On each segment appeared the paired organs of the movement, which later became the prototype of the limbs.
Archaeologists have found extinct ringed worms that had several rows of lime plates on their backs. Scientists believe that there is a definite connection between them and mollusks and brachiopods.
general characteristics
In grade 7, the type of annelids is studied in more detail. All representatives of this type have a rather characteristic structure. That from the front, that the back side of the body looks the same and symmetrical. Conventionally, it is divided into three main sections: the head lobe, numerous segments of the central part of the body and the back, or anal lobe. The central segmented part, depending on the size of the worm, can comprise from ten to several hundred rings.
The general characteristics of the ringed worms include the fact that their sizes vary from 0.25 mm to a length of 5 meters. Movement of worms is carried out in two ways depending on its type. The first method is due to the contraction of the muscles of the body, the second is using parapodia. These are the bristles that polychaete worms have. They have lateral bilobate processes on the walls of the segments. In small-necked worms, organs such as parapodia are absent altogether or have separately growing small bundles.
The structure of the head blade
Annelids have senses in front. These are eyes, olfactory cells, which are also found on tentacles. The ciliary fossa is the organs that distinguish the effects of various odors and chemical stimuli. There are organs of hearing that have a structure resembling locators. And, of course, the main organ is the mouth.
Segmented part
This part is the same general characteristic of the type of annelids. The central region of the body consists of rings, each of which is a completely independent part of the body. Such an area is called whole. It is divided by partitions into segments. They are noticeable when considering the appearance. The outer rings of the worm correspond to the internal partitions. It is by this feature that the worms got their main name - ringed or ringed.
Such a division of the body for the life of the worm is very important. If one or several rings are damaged, the rest remain intact, and the animal regenerates in a short period of time. The internal organs are also located in accordance with the segmentation of the rings.
Secondary body cavity, or whole
In the structure of the ringed worms, the general characteristic is as follows: the dermal-muscular sac has a coelomic fluid inside. It consists of the cuticle, cutaneous epithelium and the annular and longitudinal muscles. The fluid, which is contained in the body cavity, maintains the constancy of the internal environment. All the main functions of the body are carried out there: transport, excretory, musculoskeletal and sexual. This fluid is involved in the accumulation of nutrients, removes all waste, harmful substances and sexual products.
Type ringed worms has common characteristics in the field of the structure of the cells of the body. The upper (outer) layer is called the ectoderm, then the mesoderm is located with the secondary cavity covered with its cells. This space is from the walls of the body to the internal organs of the worm. The fluid that is contained in the secondary body cavity, due to pressure, maintains the constant shape of the worm and plays the role of a hydroskeleton. The last inner shell is called the endoderm. Since the body of annelids consists of three shells, they are also called three-layer animals.
Worm food system
The general characteristics of annelids in Grade 7 briefly describes the structure of the digestive system of the body of these animals. In the front of the mouth is located. It is located in the first segment of the peritoneum. The entire digestive tract has a through structure system. This is the mouth itself, then there is a pharyngeal ring separating the worm's throat. The long esophagus ends with goiter and stomach.
The intestine has a common characteristic for the class of annelids. It consists of three departments with different purposes. These are the anterior, middle, and posterior intestines. The middle section consists of endoderm, and the rest is ectodermal.
Circulatory system
The general characteristics of annelids are briefly described in the Grade 7 textbook. And the structure of the circulatory system can be seen in the schematic image above. Vessels are marked in red. The figure clearly shows that the circulatory system of annelids is closed. It consists of two long longitudinal vessels. It is spinal and ventral. Between themselves, they are connected by annular vessels in each segment that resemble veins and arteries. The circulatory system is closed, the blood does not leave the vessels and does not pour out in the body cavity.
The color of blood in different types of worms can be different: red, transparent and even green. It depends on the properties of the chemical structure of the respiratory pigment. It is close to hemoglobin and has a different oxygen content. Depends on the habitat of the ring worm.
The movement of blood through the vessels is due to contractions of some parts of the dorsal and less often - the annular vessels. After all, hearts have no worms. Kolchetsy contain special contractile elements in these vessels.
Excretory and respiratory systems
These systems in the type of annelids (a general description is briefly described in the textbook class 7) are associated with the skin. Breathing is carried out through the skin or gills, which are located on parapodia of marine polychaeta worms. The gills are branched thin-walled outgrowths on the dorsal lobes. They can be of different shapes: leafy, pinnate or bushy. The inner part of the gills is permeated with thin blood vessels. If the worms are weak-necked, then breathing occurs through the moist skin of the body.
The excretory system consists of metanephridium, protonephridia and mixonephridia, located in each segment of the worm in pairs. Mixonephridia are the prototype of the kidneys. Metanefridia have the shape of a funnel located in the coelom, from which a thin and short channel leads the excretion products to the outside in each segment.
Nervous system
If we compare the general characteristics of round and annelids, the latter have a more refined nervous system and sense organs. They have an accumulation of nerve cells above the pharyngeal ring of the anterior lobe of the body. The nervous system consists of ganglia. This is the epipharyngeal and subpharyngeal formations connected by nerve trunks in the pharyngeal ring. In each segment, one can see a pair of such ganglia of the ventral chain of the nervous system.
In the picture above you can see them. They are marked in yellow. Large ganglia in the pharynx play the role of the brain, from which impulses diverge along the abdominal chain. The nervous system of the worm's organs also belongs to the nervous system. He has a lot of them. These are eyes, and organs of touch on the skin, and chemical senses. Sensitive cells are located all over the body.
Breeding
Describing the general characteristics of the type of annelids (Grade 7), it is impossible not to mention the reproduction of these animals. They are mostly heterosexual, but some have developed hermaphroditism. The latter include well-known leeches and earthworms. In this case, conception occurs in the organism itself, without fertilization from the outside.
In many polychaetoid development occurs from the larva, and in the remaining subspecies it is direct. The gonads are under the coelom epithelium in each or nearly every segment. When a rupture occurs in these cells, the germ cells enter the coelom fluid and are expelled through the organs of the excretory system to the outside. For many, fertilization occurs on the outer surface, and in underground soil worms - inside.
But there is another kind of breeding. In conditions favorable for life, when there is a lot of food, individual parts of the body begin to grow. For example, several mouths may appear. Subsequently, the rest grows. The worm splits into several separate parts. This is an asexual type of reproduction, when a certain part of the body appears, and the rest is regenerated later. As an example, it is possible to cite the ability for this type of reproduction of auloforus.
In the article, you learned in detail all the main characteristics of annelids, which are studied in school grade 7. We hope that such a detailed description of these animals will help to learn more easily.
I. Class organization.
Ii. Test of knowledge and skills.
^ III. The study of new material.
Comparative characteristics of various classes of annelids.
Working with the text of the textbook on pages 129-131, tables and figures in the textbook, let's jointly fill in the following table (table heading on the board):
1. Habitat
sea and fresh water bodies
sea and fresh water bodies
direct development without larval stage
Independent work. Using the text of the textbook on pages 129-131, highlight a variety of environmental groups among different classes of kolchets:
Polychaetes:
1. bottom:
a) crawling (nereid),
b) digging (sand),
c) sessile (serpula).
2. free-floating (planktonic forms).
Mallechnitis:
1. freshwater:
a) bottom, crawling (pipe),
b) bottom, burrow.
2. ground:
a) soil, digging (earthworm).
Leech:
1. freshwater (medical leech).
2. inhabitants of brackish water of estuaries (fish leech).
3. terrestrial (tropical leeches).
Find in the text the answer to the question: What is the medical value of leeches? (Used in medical practice in the treatment of hypertension and atherosclerosis).
^ Iv. Consolidation studied.
^ V. Homework.
To study the material of the textbook, to prepare a message from the additional literature on the medical use of leeches.
^ Topic of the lesson:
Features of the organization of mollusks, their origin. The variety of mollusks, their importance in nature.
Lesson concept system:
Methodical techniques:
^ Means of visualization:
natural: wet preparations of the common pond snail or snail, mollusk shells, figurative: tables with the image of mollusks of different classes, drawings from the textbook and other books.
I. Class organization.
Theme of the lesson:
Variety of annelids. Clusters Polychaetae, Malaschetikovye and leeches.
Lesson concept system:
Methodical techniques:
^ Means of visualization:
natural: wet preparations of annelids, figurative: tables with the image of annelids, drawings from a textbook and other books.
I. Class organization.
Ii. Test of knowledge and skills.
^ III. The study of new material.
Comparative characteristics of various classes of annelids.
Working with the text of the textbook on pages 129-131, tables and figures in the textbook, let's jointly fill in the following table (table heading on the board):
1. Habitat
sea and fresh water bodies
sea and fresh water bodies
direct development without larval stage
Independent work. Using the text of the textbook on pages 129-131, highlight a variety of environmental groups among different classes of kolchets:
Polychaetes:
1. bottom:
a) crawling (nereid),
b) digging (sand),
c) sessile (serpula).
2. free-floating (planktonic forms).
Mallechnitis:
1. freshwater:
a) bottom, crawling (pipe),
b) bottom, burrow.
2. ground:
a) soil, digging (earthworm).
Leech:
1. freshwater (medical leech).
2. inhabitants of brackish water of estuaries (fish leech).
3. terrestrial (tropical leeches).
Find in the text the answer to the question: What is the medical value of leeches? (Used in medical practice in the treatment of hypertension and atherosclerosis).
^ Iv. Consolidation studied.
^ V. Homework.
To study the material of the textbook, to prepare a message from the additional literature on the medical use of leeches.
^ Topic of the lesson:
Features of the organization of mollusks, their origin. The variety of mollusks, their importance in nature.
Lesson concept system:
Methodical techniques:
^ Means of visualization:
natural: wet preparations of the common pond snail or snail, mollusk shells, figurative: tables with the image of mollusks of different classes, drawings from the textbook and other books.
I. Class organization.
Ii. The study of new material.
^ III. Consolidation studied.
^ Iv. Homework.
To study the text of the textbook, to answer the questions of the textbook.
Theme of the lesson:
Answers and explanations
Answers and explanations
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Ringed worms type:
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The type of annelids, or kolchtsov, covers a significant number of species (about 9000) of higher worms. The main signs of the type Annelida are:
1. The body of the annelids is composed of the head lobe (prostomium), the segmented torso and the posterior anal lobe (pygidium). On the head lobe mostly sense organs are located.
2. There is a well-developed skin-muscle bag.
3. Animals have a secondary body cavity, or whole, and each segment has its own pair of coelomic bags. Head and anal lobes lack coelom.
4. The oral opening lies on the ventral side of the first segment of the body. The digestive system, as a rule, consists of the oral cavity, pharynx, midgut and posterior intestine, which opens with the anus at the end of the anal lobe.
5. Most kolchets have a well-developed closed circulatory system.
6. The selection function is performed by segmental organs - nephridium. Usually in each segment there is one pair of Nephridians.
7. The nervous system consists of the paired brain, a pair of peripharyngeal nerve trunks, enveloping the pharynx from the sides and connecting the brain with the abdominal part of the nervous system.The latter consists of a pair of more or less contiguous, and sometimes merged together longitudinal nerve cords, in which paired ganglia are located in each segment (except for the most primitive forms). Many ringed worms have sensory organs - eyes, olfactory pits and various tentacle-like appendages.
8. The most primitive ringed worms are dioecious, part of the annelid appeared hermaphroditism a second time.
9. Crushing eggs goes on a spiral type and has a determinative nature.
10. In the lower representatives of the type, the development proceeds with metamorphosis, a typical larva — the trochophore.
Ring type is divided by
SECURITY (ACLITELLATA)
SUBTYPE CASTLE (CLITELLATA)
According to the more modern classification, the type Annelida (annelids) is a common land and water (mainly marine) worms. Like mollusks, they are coelomic primary movers, but, what strongly distinguishes them from mollusks, are clearly segmented animals. 4 classes:
Flat worms
In flatworms, a two-sided, symmetric, elongated and flattened body. They do not have body cavities, the gaps between organs are filled with loose connective tissue - parenchyma. About 12.5 thousand species belong to this type, among which there are both free-living species and dangerous parasites— pork and bull chainsbelonging to the class of tapeworms, liver flukerelated to the class of flukes, and many others. The smallest of these worms have a length of 0.2 mm, the largest - up to 18 m.
Planaria, widespread in the seas and freshwater bodies, belong to the class of ciliary worms (their body is covered with microscopic cilia). Planaria is a predator feeding on small invertebrates. It swallows prey by means of a retractable throat, undigested remnants are excreted through the mouth. Gas exchange is carried out all over the body. The planarian has eyes and organs of touch, tentacles, located at the head end of the body. Planarian reproduce sexually (like all flatworms, they are hermaphroditic) or asexual, sharing in half and recovering to a whole animal.
Roundworms
Nematodes, rotifers, scrapers, hairworms are a type of roundworm, including about 9 thousand species. They have a non-segmented body covered with a multilayer shell. Between the integuments and the intestines there is a cavity filled with fluid — this is the so-called primary body cavity, which performs a supporting and transport function, and internal organs are located in it. The digestive system begins with the mouth and ends with the anus.
Roundworms are antiseptic, reproduce sexually. They inhabit reservoirs, many of their representatives live in the soil, some species parasitize in the organs and tissues of plants and animals. Roundworms, pinworms are one of the most common and dangerous human parasites.
Worms that parasitize animals and humans are called worms. Their eggs get into the mouth with unwashed vegetables and fruits, when eating with dirty hands, and disregard of personal hygiene. Worms settle in the digestive tract, liver, kidneys, etc. Human ascaris lives in the intestines and grows up to 40 cm. It poisons the body and can damage individual organs. Children's pinworm, 5-10 mm long, parasitizes in the intestine. Infection with worms causes severe illness.
Ringed worms
The type of annelids (kolchets) are fairly highly organized animals, so they are often called the highest worms. All kolchetsov body consists of a plurality of segments, and all their internal organs are segmented. Inside the body there is a fluid-filled cavity that performs basic life functions.
Well-known rain (or earth) worms belong to the class of low-chained ringed worms. They are distributed throughout the world, most numerous in the tropics. The length of the body of various earthworms varies from a few centimeters to 2 m. These worms crawl due to the alternate contraction and relaxation of the muscles of the body. They lead a digging life, feed on organic remains and improve the quality of the soil through their activities. In polychaete annulate worms, each body segment has a pair of lobe-shaped protrusions, provided with tufts of elastic setae.
Sabellida dwells at the bottom of reservoirs, her long body is hidden in horn tubes, of which only painted in a variety of colors opened by a fan or rolled up in wide funnels of the gills protrude. With their help, this animal breathes and captures food particles. The shoots of the gills are littered with hundreds of small eyes that are sensitive to the approach of danger, in this case, the fans and funnels instantly fold and disappear in the depths of the tube.
