21.04.2020

Download the presentation on the topic of gastropods. Interesting facts about shellfish. Organs of movement. Way to travel

TYPE
M O L L Y S K I Performed by: Gurov Anton
7 B grade, school No. 49

Moscow 2011

Teacher: Khanova I.B.

ORIGIN OF MOLLUSCS

The problem of the origin of the type of mollusks is debatable. Some biologists derived the hypothetical ancestor of mollusks from annelids, others - from flatworms.
Currently, the most widespread hypothesis is the origin of mollusks from primary coelomic trochophore animals, from which annelids also originate. Some people talk about the relationship between mollusks and annelids common features organizations. Thus, a number of lower mollusks have retained the features of metamerism and have a scalene nervous system. The ontogenesis of mollusks also shows similarities with annelids, inherited from common ancestors (spiral fragmentation, metamerism of some rudiments, etc.)

MAIN CHARACTERISTICS OF MOLLUSKS I

MOLLUSCS are a large type of animal in terms of the number of species (130 thousand). They live mainly in the seas (mussels, oysters, squids, octopuses), fresh water bodies (toothless snails, pond snails, livebearers), and less often in a humid terrestrial environment (grape snail, slugs).
Body sizes of adult mollusks different types vary significantly - from a few millimeters to 20 m. Most of them are sedentary animals, some lead an attached lifestyle (mussels, oysters), and only cephalopods able to move quickly in a reactive manner.
Mollusks are bilaterally symmetrical animals, however, in some mollusks, due to a peculiar displacement of organs, the body becomes asymmetrical. The body of mollusks is unsegmented; only a number of lower representatives show some signs of metamerism.
Mollusks are secondary cavity animals with a non-metameric residual coelim, represented in most forms by the pericardial sac (pericardium) and the gonad cavity. All spaces between organs are filled with connective tissue.

MAIN CHARACTERISTICS OF MOLLUSKS II

The body of mollusks, as a rule, consists of three sections - head, trunk and legs. Very often the body grows onto the dorsal side in the form of an internal sac. The leg is a muscular unpaired outgrowth of the abdominal wall of the body, used for movement. The base of the body is surrounded by a large fold of skin - the mantle. Between the mantle and the body there is a mantle cavity in which the gills, some sensory organs lie, and the openings of the hindgut, kidneys and reproductive apparatus open. All these formations, together with the kidneys and heart (located in close proximity to the mantle cavity) are called the mantle organ complex. On the dorsal side of the body, as a rule, there is a protective shell secreted by the mantle, usually solid, less often bicuspid, or consisting of several plates.
Most mollusks are characterized by the presence in the throat of a special apparatus for grinding food - a grater (radula). Circulatory system characterized by the presence of a heart consisting of a ventricle and atria; it is not closed, that is, part of its path the blood passes through a system of lacunae and sinuses that are not formed into vessels. The respiratory organs are usually represented by primary gills - ctenidia. The latter, however, disappear in a number of forms or are replaced by respiratory organs of a different origin.

HABITAT OF MOLLUSKS

Mollusks live in rivers, seas, oceans and other bodies of water, as well as on land - in fields, forests and other land areas

STRUCTURE OF MOLLUSKS

BODY
The body of mollusks does not bear traces of true segmentation, despite the fact that some organs (for example, the gills of chitons and monoplacophorans) may be characterized by a serial structure.
The body of mollusks, as a rule, consists of three sections: head, legs and torso. Representatives of the class Caudofoveata lack a leg. Bivalve mollusks lose their heads for the second time.
The leg is a muscular unpaired outgrowth of the abdominal wall of the body, and, as a rule, serves for movement.
The torso contains all the main internal organs. In the Conchifera group, it grows strongly on the dorsal side during embryonic development, resulting in the formation of the so-called visceral sac.
The mantle extends from the base of the body - an epithelial fold that forms the mantle cavity associated with external environment. The mantle cavity contains the so-called mantle complex of organs: the excretory tracts of the reproductive, digestive and excretory systems, ctenidium, osphradium and hypobranchial gland. In addition, the mantle complex of organs includes the kidney and pericardium, located next to the mantle cavity.

STRUCTURE OF MOLLUSKS

COVERS
It is believed that in the hypothetical ancestor of mollusks, the integument was represented by the so-called protoperinotum: a cuticle with aragonite spicules. A similar structure of the integument is characteristic of representatives of the classes Caudofoveata and Solenogastres. However, in all classes of mollusks, except for Caudofoveata, a ciliated crawling surface appears - a leg (on this basis they are united in the Adenopoda group). In Solenogastres, the foot is represented by a pedal groove.
Chitons (Polyplacophora) also have cuticular integuments, but only on the lateral surfaces, called perinatal folds. The dorsal surface is covered with eight shell plates.
In the group Conchifera (which includes the classes Gastropoda, Cephalopoda, Bivalvia, Scaphopoda and Monoplacophora) there are no cuticles and the shell consists of a single plate.

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STRUCTURE OF MOLLUSKS

NERVOUS SYSTEM
Nervous system mollusks of the tetraneural type. It consists of a peripharyngeal ring and four trunks: two pedal (innervate the leg) and two visceral (innervate the visceral sac). However, this structure is characteristic only of the lower groups of mollusks: Caudofoveata, Solenogastros and Polyplacophora.
In most other representatives of mollusks, the formation of ganglia and their displacement to the anterior end of the body are observed, and greatest development receives the suprapharyngeal nerve ganglion "brain". As a result, a scattered-nodular type nervous system is formed.
Accommodation occurs due to changes in the shape of the eye - moving away or bringing together the retina and lens.
Smell and taste are not separate.

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STRUCTURE OF MOLLUSKS

CIRCULATORY SYSTEM
Unclosed (except for cephalopods). It includes the heart (the organ that ensures the movement of blood through the vessels and cavities of the body) and blood vessels. The heart consists of a ventricle and one or two atria (the nautilus has 4 atria).
Blood vessels pour blood into the space between the cells of the organs. The blood then collects again in the vessels and enters the gills or lungs.
It is worth noting the unusual bluish color of the blood of mollusks. This color comes from hemocyanin, which performs functions similar to those of hemoglobin in the blood of chordates and annelids

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STRUCTURE OF MOLLUSKS

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STRUCTURE OF MOLLUSKS

EXCRETORY SYSTEM
One, usually two kidneys, in which excretory products accumulate in the form of lumps of uric acid.
They are released every 14-20 days.

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STRUCTURE OF MOLLUSKS

GENITAL SYSTEM
Mollusks can be either hermaphrodite (snails) or dioecious (toothless).
Development can be direct or indirect.
The larvae of some mollusks are called sailfish, or veliger, because they resemble a sail.

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DIVERSITY OF SHELLFISHES

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CLASSES OF MOLLUSCS I

GASTROPODA, a class of invertebrate animals such as mollusks.
The body is divided into the head, visceral sac and leg. The head bears 1 or 2 pairs of tentacles and a pair of eyes. The internal sac and the shell covering it are spirally twisted to the right or (rarely) to left side(asymmetrical animals).
The shell is distinguished by a wide variety of shapes and sculptures: from highly conical to flat-spiral and saucer-shaped; consists of three layers: the outer one is horny, the middle one is porcelain-like and the inner one is mother-of-pearl. In some gastropods, the shell becomes internal or disappears.
The anterior part of the visceral sac is bounded externally by a fold of skin - the mantle. The mantle cavity contains a complex of organs consisting of primitive forms of symmetrically lying: rectum with anus, two hypobranchial glands, two ctenidia, two osphradiae (chemical sense organs), a heart with two atria and two kidneys.

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CLASSES OF MOLLUSCS II

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CLASSES OF MOLLUSCS III

Presentation on the topic: “Shellfish. Gastropods. » Graduated: Student of MAOU “Lyceum No. 28 named after. N.A. Ryabova" 7th class "B" Ermilova Elizaveta

Grape snail.

Origin of mollusks. The origin of mollusks - the ancient inhabitants of our planet - appeared about 450-500 million years ago. Among their characteristic features is a calcareous shell. Mollusks are a large type of animal in terms of the number of species (130 thousand). Their ancestors, apparently, were flatworms. Mollusks live mainly in the seas (mussels, oysters, squids, octopuses), fresh water bodies (toothless snails, pond snails, livebearers), and less often in a humid terrestrial environment (grape snail, slugs). The body sizes of adult mollusks of different species vary significantly - from a few millimeters to 20 meters.

Mollusks are divided into 3 classes: Gastropods Cephalopods Bivalves

Gastropods.

The gastropod class is the only class whose representatives have mastered not only water bodies, but also land, therefore, in terms of the number of species of mollusks, it is the most numerous class. Its representatives are relatively small in size: the Black Sea mollusk rapana is up to 12 cm tall, the grape snail is 8 cm, some naked slugs are up to 10 cm, large tropical species reach 60 cm.

External and internal structure.

Gastropods include slugs, which are named because of the abundant mucus they secrete. They don't have a sink. They live on land in damp places and feed on plants, mushrooms, some are found in vegetable gardens, causing harm to cultivated plants.

Field slug.

Interesting and educational.

1. The largest clam ever caught weighed about 340 kilograms. It was caught in Okinawa, Japan in 1956.

2. The oldest clam caught by humans was estimated to be around 405 years old, possibly making it the oldest marine animal3. The age of mollusks can be determined by the number of rings on the shell valve. Each ring differs from the previous one due to the characteristics of the food consumed during this period, the state of the environment, temperature and the amount of oxygen in the water.

6. An oyster can produce about a million eggs in one season. However, only a few will be able to survive and grow to adulthood.

7. Some varieties of scallops have dozens blue eyes along the edges of the shell. With their help, scallops can notice predators and escape in time. 8. Bivalves can move. Scallops, for example, by rhythmically squeezing their valves and throwing out a stream of water, can swim quite far from their enemies - starfish.

Thank you for your attention!

Gastropods, or snails, are the richest class of mollusc species. Most gastropods are marine animals. Some representatives of this class, in the course of evolution, adapted to life in fresh water bodies, while others switched to terrestrial existence. In the seas, gastropods are found on various depths, on land in a variety of climatic conditions. They are tolerant of high and low temperatures, partly due to their ability to hibernate: in the north in winter, in the south in summer and often in winter.

The body shape of gastropods is varied. The head is clearly separate from the body, bears 12 pairs of tentacles and a pair of eyes. The leg is well developed and usually has a wide crawling sole. The body forms an outgrowth in the form of a large internal sac. Characteristic All gastropods have an asymmetry in structure that arises as a result of the formation of a spirally twisted shell. The sizes of gastropods range from 23 mm to several centimeters (grape snail, slug, pond snail

The mouth of the mollusk leads into the oral cavity, which turns into a muscular pharynx, in which the tongue with the radula is located. Besides, in oral cavity there are local thickenings of the cuticle (the so-called jaws). The ducts of one pair open into the pharynx salivary glands. The pharynx passes into the esophagus, and some at its end an extension is formed - a goiter. The midgut has an extension - the stomach, followed by small intestine, turning into the back, ending with powder. In some lower gastropods, the hindgut passes through the ventricle of the heart. The liver secretes secretions that facilitate the digestion of food (mainly carbohydrates), in addition, the liver is capable of absorbing food and stores glycogen and fats in it.

Most gastropods have one left atrium (the right one is sometimes completely reduced) and one ventricle. The heart of mollusks is surrounded by pericardium. The aorta departs from the ventricle, which soon divides into the cephalic aorta and the splanchnic aorta (going to the intestines, liver and gonads). From the branches of the arteries, the blood enters the lacunae, loses oxygen and collects in the venous lacunae, from here the blood returns to the gills or lung and, oxidized, enters directly into the heart.

The nervous system of animals consists of several pairs of ganglia connected by commissures. Gastropods have eyes, statocyst balance organs, organs of touch (tentacles) and chemical senses. The excretory system of mollusks most often consists of one left kidney, one end communicating with the pericardium, and the other opening into the mantle cavity on the side of the powder.

Among gastropods there are dioecious animals and hermaphrodites (snail). They always have one gonad, fertilization is cross-fertilization, and in hermaphrodites, each individual functions both as a male and as a female. Fertilization in most animals is internal. In pulmonary mollusks, development is direct and proceeds to the end in the egg shell, in the rest - with the formation of a larva (trochophore or swallowtail).

Economic importance There are few gastropods. Slugs and snails pests Agriculture. But in some countries, especially in France, grape snails are considered a delicacy and are specially bred. Many large sea snails (trumpet snails) are also eaten. Shells of species with a well-developed mother-of-pearl layer are used to make jewelry.

In the old days, special cowrie shells southern countries served as a bargaining chip. A number of gastropod species are the first intermediate hosts parasitic flatworms that are also dangerous to humans. Two genera of tropical mollusks, cone and terebra, have poisonous glands and can seriously “sting” a careless person who picks them up.

Lesson topic: Gastropods .

(snails)

The purpose of the lesson:

Get acquainted with the taxonomy of mollusks and their significance.
Show the complexity of the level of organization of mollusks compared to annelids.
Identify the features of the structure, life activity and origin of mollusks.
Continue to develop analytical skills; establish cause-and-effect relationships.

Prudovik

Horn coil

Terrestrial molluscs

Grape snail

Yantarka

Sea shellfish

cowrie

miter

Cone

Murex

Features for comparison

Gastropods

Habitats

Bivalve

Sink

Cephalopods

Division of the body into sections

Organs of movement. Way to travel.

Lifestyle.

Type of food.

Method of obtaining food.

Breath

Most snails develop open-spiral shell, when all its revolutions are visible from the outside

In some snails, the last larger curl covers all the previous ones. Such shells are called cryptospiral

Cowrie(eng. Cowry) - shells of tropical mollusks, used as money on the islands of Oceania. Kauri - sea gastropod cyprae family (Cypraeidae). The peoples inhabiting the coastal regions have been familiar with them for several thousand years. Cowrie shells are known to have been used as money in China, India, the Arabian Peninsula and Africa. They were believed to protect against evil, and therefore cowrie shells and clay models of them were placed in the walls of buildings and in graves. The tiger cowrie is perhaps the best known of the other species. Large sizes, shiny surface and large stain on the sink, it attracts the attention of even a casual observer. Cowries are predators that feed on soft-bodied creatures that live on rocks. The leg almost completely wraps around the shell as the clam moves, and the siphon sticks out from the front like a small periscope. Female cowries lay eggs in small capsules, attaching them in clusters to rocks. They guard these capsules, covering them with their feet, until the offspring hatch.

Murex

Murexes, or crimsons, are one of the most popular groups among collectors. The shells of these snails are decorated with numerous projections, ridges or spines and are brightly colored. Many murexes reach impressive sizes. Representatives of the family are distributed throughout the World Ocean from polar latitudes to the equator, but the brightest and large species inhabit tropical zone. Murexes are carnivorous snails. Their victims are bivalves, the valves of which they drill with the help of their radula.

Cone- a predatory snail, and a poisonous one at that. They hunt with the help of a tooth - they pierce the victim with it, like a harpoon. They feed on sea worms, mollusks and small fish.. They can sting no worse than a bee - and the consequences can be quite unpleasant. It's even possible fatal outcome. There are about 600 types of cones. They are concentrated in tropical seas and oceans around the world. Most cones live on or near coral reefs. The snail got its name from its bullet-shaped shell. Many of the cones have brightly colored shell surfaces. Of course, the shell is heavy, and the snail has only one “leg,” so these animals move extremely slowly. Which forces them to stop fast-moving prey with a poisonous harpoon. This harpoon is a modified tooth. In general, teeth (in snails they are called radulas) are needed in order to better grind and digest food. Each tooth is located in the back wall of the mouth. The snail paralyzes the victim, the radulas retract it and grind it. And the snail spews back the indigestible material, including the disposable harpoon, which remains in the victim’s body. Another tooth becomes the harpoon. In snails they grow constantly.