Interesting facts about shellfish. Interesting facts about shellfish II. Learning new material

Gastropods, or snails, are the richest class of mollusk species in representatives. Most gastropods are marine animals. Some representatives of this class in the course of evolution adapted to life in fresh water, others switched to terrestrial existence. In the seas, gastropods are found at various depths, on land in a variety of climatic conditions. They are tolerant of high and low temperatures, due in part 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 separated from the body, bears 12 pairs of tentacles and a pair of eyes. The foot is well developed and usually has a wide crawling sole. The trunk forms an outgrowth in the form of a large visceral sac. Feature of all gastropods, the asymmetry of the structure resulting from 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 mollusks leads into the oral cavity, which passes into the muscular pharynx, in which the tongue with the radula is located. In addition, there are local thickenings of the cuticle (the so-called jaws) in the oral cavity. The ducts of one pair of salivary glands open into the pharynx. The pharynx passes into the esophagus, some at its end an extension is formed - a goiter. The middle intestine has an extension - the stomach, followed by the small intestine, passing into the back, ending in powder. In some lower gastropods, the hindgut passes through the ventricle of the heart. The liver secretes secrets that promote the digestion of food (mainly carbohydrates), in addition, the liver is capable of absorbing food and storing glycogen and fats in it.

Most gastropods have one left atrium (the right one is sometimes completely reduced) and one ventricle. The heart of molluscs is surrounded by the pericardium. The aorta departs from the ventricle, which soon divides into the head aorta and the splanchnic aorta (goes to the intestines, liver and sex gland). 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 the lung and, having been oxidized, goes directly to the heart.

The nervous system of animals consists of several pairs of ganglia connected by commissures. Gastropods have eyes, organs of balance statocysts, organs of touch (tentacles) and chemical sense. excretory system molluscs consists most of all 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 the gastropods there are dioecious animals and hermaphrodites (snail). They always have one sex gland, fertilization is cross, and in hermaphrodites, each individual functions both as a male and as a female. Fertilization in most animals is internal. In lung molluscs, development is direct and proceeds to the end in the egg shell, in the rest - with the formation of a larva (trochophore or sailboat).

The economic importance of gastropods is small. Slugs and vine snails pests Agriculture. But grape snails in some countries, especially in France, are considered a delicacy and are specially bred. Many large sea snails (trumpeters) are also eaten. The shells of species with a well-developed mother-of-pearl layer are used for making jewelry.

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

Presentation on theme: "Mollusks. Gastropods. "Performed by: Student of the MAOU "Lyceum No. 28 named after. N.A. Ryabova" 7th class "B" Ermilova Elizaveta

Grape snail.

Origin of shellfish. The origin of mollusks - the ancient inhabitants of our planet - appeared about 450-500 million years ago. Among their characteristic features, a calcareous shell is noted. Mollusks are a large type of animals in terms of the number of species (130 thousand). Their ancestors appear to have been flatworms. Mollusks live mainly in the seas (mussels, oysters, squids, octopuses), fresh water bodies (toothless, pond snails, livebearers), less often in a humid terrestrial environment (grape snail, slugs). The body sizes of adult mollusks of different species vary considerably - 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 mollusk species, this is the most numerous class. Its representatives are relatively small in size: the Black Sea rapana mollusk 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.

The gastropod mollusks are slugs, which got their name because of the abundant secretion of mucus. They don't have sinks. They live on land in humid places and feed on plants, fungi, 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 mollusk caught by man, according to scientists, was around 405 years old, it may have been 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 of blue eyes around the edges of their shells. With the help of them, scallops can notice predators and escape in time. 8. Bivalves can move around. Scallops, for example, by rhythmically squeezing the valves and throwing out a jet of water, can swim far enough away from their enemies - starfish.

Thank you for your attention!

Lesson topic: gastropods .

(snails)

The purpose of the lesson:

• To get acquainted with the taxonomy of molluscs and their meaning.
• Show the complication of the level of organization of molluscs compared to annelids.
• Identify the features of the structure, life and origin of mollusks.
• Continue the formation of skills to analyze; establish causal relationships.

• Prudovik

• Coil horn

land molluscs

grape snail

Yantarka

Sea shellfish

• kauri

miter

Cone

Murex

Signs for comparison

gastropods

habitats

Bivalves

Sink

cephalopods

Division of the body into sections

organs of movement. Way to travel.

Lifestyle.

Type of food.

The method of getting food.

Breath

Most snails form open spiral shells when all its whorls are visible from the outside

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

kauri(Eng. Cowry) - shells of tropical mollusks used as money on the islands of Oceania. Kauri is a marine gastropod mollusk of the cyprian family (Cypraeidae). The peoples inhabiting the coastal regions have known them for several thousand years. Cowrie shells are known to have been used as money in China, India, the Arabian Peninsula and Africa. It was believed that they protect from evil, and therefore cowrie shells, their clay models were put into the walls of buildings and into graves. The tiger kauri is perhaps the most famous among the other species. Large sizes, with a shiny surface and a large spot on the shell, it attracts the eye of even a casual observer. Kauri are predators that feed on soft-bodied creatures that live on rocks. The foot wraps almost completely around the shell as the clam moves, and the siphon sticks out at the front like a small periscope. Female kauri lay their eggs in small capsules, attaching them in clusters to rocks. They guard these capsules by covering them with their foot until the offspring hatch.

Murex

Mureks, or crimsons, is one of the most popular groups among collectors. The shells of these snails are decorated with numerous outgrowths, ridges or spikes and are brightly colored. Many murex reach impressive sizes. Representatives of the family are distributed throughout the World Ocean from the polar latitudes to the equator, but the brightest and largest species inhabit the tropical zone. Murex are carnivorous snails. Their victims are bivalve mollusks, the valves of which they drill through with their radula.

Cone- a predatory snail, moreover, poisonous. They hunt with the help of a tooth - they pierce the victim with it, like with 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. Even death is possible. 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 gets its name from its bullet-shaped shell. In many of the cones, the surface of the shells is brightly colored. Of course, the shell is heavy, and the "leg" of the snail is only one, so these animals move extremely slowly. Which forces them to stop fast-moving prey with a poisonous harpoon. This harpoon is a modified tooth. But 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 oral cavity. The snail paralyzes the victim, the radulas draw it in, grind it. And indigestible material, including a disposable harpoon, remaining in the body of the victim, the snail spews back. Another tooth becomes a harpoon. In snails, they grow constantly.

Check

• Segmented.
• Head, body, leg.
• Mantle.
• Atrium (sometimes two) and ventricle.
• mantle cavity.

• Attachment of muscles, external skeleton, protection.
• Gastropods.
• Tongue with a "grater", liver.
• Open.
• Bud.
• Atmospheric.

Homework: 11.

Creative task:

• 1. Write a biological essay about the molluscs of Belarus.
• 2. Prepare a presentation on the diversity of shellfish.

Attach clam shells to the board using magnets according to your feelings:

White: learned everything, it was interesting

Orange: not understood everything, puzzled

Yellow: did not understand anything, tired

Reflection

Tasks:

1. To acquaint students with the diversity, organization and significance of gastropods.
2. To teach to establish cause-and-effect relationships between structural features, life activity and habitat of snails.
3. Develop the ability to listen carefully, analyze information.
4. Activate the cognitive activity of students through independent work on assignments.
5. Continue to teach children to recognize organs, organ systems of mollusks in drawings, diagrams and name them.
6. Develop a desire to know the animal world.

Equipment:

• a computer,
• projector,
• screen,
• separate material "Sinks of gastropods" (one per desk)
• DI. Traitak, S.V. Sumatokhin. Biology: Animals. Grade 7: Textbook for general education. institutions. - M.: Mnemosyne, 2008
• THEM. Gufeld. Zoology Grade 7: Workbook, 1997

Lesson plan:

I. Organizational moment and motivation of students' activities.

Checking knowledge on the topic "General characteristics of molluscs":

1. 1-2 students complete a test on a computer. At this time, 1-2 students talk at the blackboard general characteristics shellfish (from paragraph 15 of the textbook).

2. Frontal work according to the interactive scheme "The structure of mollusk organ systems" and the simulator "Mollusk organ systems".

II. Learning new material.

1. Actualization of the topic, the purpose of the lesson (the teacher sets the relevance of the topic and designates the problematic issue of the lesson. Students write the topic of the lesson and homework. Slides 1-2, presentation).

2. Characteristic features of gastropods. (Teacher's story with elements of conversation on the slides: slide 3 - the number of species of snails; slides 4-12 - the habitat of snails; slides 13-15 - body structure. Working with the handout "Gastropod Shells" (students examine gastropod shells under numbers indicated on slide 16 - gastropod shells).Slide 17 - respiratory organs and food specialization).

Dynamic pause.

3. The structure and lifestyle of the common pond snail, grape snail and field slug. ( Independent work by options: read and tell the text of the textbook on pages 64-65 about the structure and lifestyle of gastropods. Students' story. Discussion of the question: what is common in the structure of the studied mollusks. slides 19-20).

4. Marine mollusks: predatory snails cone and murex, planktonic gastropod - angelfish. (Teacher's story with elements of conversation on slides: 21-23).

5. Relationship between structural features, life activity and habitat of snails. (Front discussion of the problematic issue: what is the relationship between the structural features, life activity and habitat of snails. Students write down the features of adaptation to the habitat of gastropods. Slides 24 - 25.)

6. The value of snails in nature. (Story-conversation. Slide 26.)

7. The value of snails in human life. (Story-conversation. Slide 27. Independent work on the assignment: from the article “Do you know?” On page 45 of the workbook, find the answer to the question of what importance kauri and murex mollusks have in human life. Slide 28 - 29.)

III. Consolidation of the studied material(discussion on the questions: slide 30. Performing a test followed by self-assessment: slides 31-32).

IV. The result of the lesson, grades for the lesson.