The mollusks are named so because... Game tasks in zoology. Theme: “Shellfish. Eyes are characteristic of representatives of classes
Mollusks are widespread secondary cavities, invertebrate animals. Their body is soft, undivided; in most it is divided into a head, torso and leg. The main characteristics of mollusks are the presence in most species limestone sink And mantle- folds of skin covering internal organs. The oral cavity of mollusks is filled with parenchyma. The circulatory system is not closed. Over 130,000 modern species and approximately the same number of fossil species are known. Mollusks are divided into classes: gastropods, bivalve, cephalopods.
Class Gastropods
Class Gastropods- this 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, this is the most numerous class. Its representatives are relatively small in size: Black Sea mollusk rapana up to 12 cm high, grape snail- 8 cm, some naked slugs- up to 10 cm, large tropical species reach 60 cm.
A typical representative of the class is big pond snail, living in ponds, lakes, quiet creeks. Its body is divided into a head, a torso and a leg, which occupies the entire ventral surface of the body (hence the name of the class).
The body of the mollusk is covered with a mantle and enclosed in a spirally twisted shell. The movement of the mollusk occurs due to the wave-like contraction of the leg muscles. There is a mouth on the underside of the head, and two sensitive tentacles on the sides, with eyes at their base.
The pond snail feeds on plant foods. In its throat there is a muscular tongue with numerous teeth on the underside, with which, like a grater, the pond snail scrapes off the soft tissues of plants. Through throat And esophagus food gets into stomach, where it begins to be digested. Further digestion occurs in liver, and ends in the intestines. Undigested food is thrown out through the anus.
The pond snail breathes with the help of lung- a special pocket of the mantle where air enters through the breathing hole. Since the pond snail breathes atmospheric air, it needs to rise to the surface of the water from time to time. The walls of the lung are woven with a network blood vessels. Here the blood is enriched with oxygen and carbon dioxide is released.
Heart The pond snail consists of two chambers - atria And ventricle. Their walls alternately contract, pushing blood into the vessels. From large vessels through capillaries blood enters the space between organs. This circulatory system is called open. From the body cavity, blood (venous - without oxygen) is collected in a vessel approaching the lung, where it is enriched with oxygen, from where it enters the atrium, then into the ventricle and then through arteries- vessels carrying oxygen-enriched blood (arterial) flows to the organs.
The excretory organ is bud. The blood flowing through it is freed from toxic metabolic products. These substances are excreted from the kidney through an opening located next to the anus.
The nervous system is represented by five pairs nerve ganglia located in different parts of the body, nerves extend from them to all organs.
Pond fish are hermaphrodites, but they undergo cross-fertilization. Eggs are laid on the surface of aquatic plants. Young individuals develop from them. Development is direct.
Gastropods include slugs, named because of the abundantly secreted mucus. 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.
Herbivorous gastropods include grape snail, which also harms agriculture. In some countries it is used as food.
Among the numerous species of gastropods, marine mollusks are especially famous for their beautiful shells. They are used as souvenirs, buttons are made from the mother-of-pearl layer, and some peoples of Africa and Asia make money and jewelry from the shell of a very small cowrie mollusk.
Class bivalve- exclusively aquatic animals. They pump water through their mantle cavity, selecting nutrients from it. This way of eating is called filtering. It does not require special mobility of organisms, so representatives of the class exhibit some simplification in structure compared to representatives of other classes. All mollusks of this class have bivalve shell(hence the name of the class). The shell valves are connected by a special elastic ligament located on the dorsal side of the mollusk. Muscles are attached to the shell valves - contactors, their contraction helps bring the valves closer together, closing the shell; when they relax, the shell opens.
Representatives of this class are , pearl barley, oysters, mussels. The largest sea mollusk is tridacna, weighing up to 300 kg.
The most common mollusk in fresh water bodies of the country is. The toothless body, consisting of torso And legs, covered with a mantle hanging from the sides in the form of two folds.
Between the folds and the body there is a cavity in which there are gills And leg. Toothless has no head. At the posterior end of the body, both folds of the mantle are pressed against each other, forming two siphon: lower (input) and upper (output). Through the lower siphon, water enters the mantle cavity and washes the gills, which ensures respiration. Various simple unicellular algae and the remains of dead plants are brought with water. Filtered food particles enter the mouth through the stomach And intestines where they are exposed enzymes. The toothless has a well developed liver, the ducts of which flow into the stomach.
Bivalves are used by humans. Mussels and oysters are eaten; others, for example, are bred to produce pearls and mother-of-pearl: pearl mussels, pearl barley.
Class Cephalopods
Modern cephalopods There are about 700 species, exclusively inhabitants of seas and oceans with a high concentration of salts, so they are not found either in the Black or Azov Seas.
Cephalopods are medium to large sized predators. Their body consists of torso And big head, the leg turned into tentacles that surround horn. Most of them have 8 identical tentacles, e.g. octopuses or 8 short and 2 long, like squid.
On the tentacles are suckers, with the help of which prey is retained. Only one tropical species does not have suckers - nautilus, but has a large number of tentacles. Representatives of the class have large eyes, resembling human eyes. Below, between the head and body, there is a gap connecting to the mantle cavity. A special tube called a tube opens into this gap. watering can, through which the mantle cavity connects with the environment and is a modified part of the leg.
Many representatives of cephalopods do not have a shell, only in the cuttlefish it is located under the skin, and in the nautilus there is a multi-chambered shell. The body is located in one of them, the others are filled with air, which contributes to the rapid buoyancy of animals. In many cephalopods, thanks to their jet mode of movement, the speed reaches 70 km per hour (squids).
The skin of many cephalopods can instantly change color under the influence of nerve impulses. Coloration can be protective (camouflaged to match the color of the environment) or threatening (contrasting color, often changing). This is due to the high level of development of the nervous system, which has a complex brain, protected by a cartilaginous shell - “ scull", sensory organs that determine complex behavior, in particular, the formation of conditioned reflexes.
For example, in case of danger, the salivary glands secrete a poison that kills prey, or the ducts of the ink gland secrete a liquid that forms a black spot in the water, under its cover the mollusk runs away from enemies.
Cephalopods are dioecious animals. They are characterized by direct development.
Cephalopods are of great industrial importance: they are used as food (squid, octopus, cuttlefish); brown paint, sepia, and natural Chinese ink are made from the contents of the ink sac of cuttlefish and squid. In the intestines of sperm whales, a special substance is formed from the undigested remains of cephalopods - ambergris, which is used in the perfume industry to impart stability to the smell of perfumes. Cephalopods are a food source for marine animals - pinnipeds, toothed whales, etc.
3. Complete the sentences:
A) Excretory organs of mollusks - ...
B) Mollusks breathe using...
C) The body of the mollusk is surrounded by a fold of skin...
D) The shell of a mollusk consists of three layers:...
D) Ducts open into the stomach..., its secretion dissolves...
4. Write down in a row the numbers of mollusks belonging to the class Bivalves:
7. Oyster 8. Octopus 9. Pearl barley 10. Nautilus
5. Tell us about the role of gastropods in nature and their significance in human life.
Test on the topic “Shellfish” Option 2.
1. Determine which class the mollusk shown in the figure belongs to. Name the characteristics of the class.
3. Complete the sentences:
A) In cephalopods, the leg is modified into..., located on...
B) Respiratory organs of mussels….
B) Type of nutrition of bivalve mollusks...
D) The brain of cephalopods is protected by..., at the base of the tentacles and fins there are...
D) In mollusks the circulatory system... consists of...
4 . Write down in a row the numbers of mollusks belonging to the class Gastropods:
1. Scallop 2. Pond snail 3. Slug 4. Cuttlefish 5. Mussel 6. Squid
7. Oyster 8. Octopus 9. Pearl barley 10. Reel
5. Tell us about the role of bivalves in nature and their significance in human life.
Option 1.
1. Prudovik, class Gastropods. They have a complete shell (except for slugs).
The body is asymmetrical, consisting of a torso, legs and head. The leg is muscular, with a wide sole. The glands of the leg secrete copious mucus. In the mouth there is a protrusion with teeth - the tongue. Respiratory organs - lungs and gills (most have only one - the left one). The heart is two-chambered. There is only one kidney - the left one. There are tentacles on the head - organs of touch. Hermaphrodites. Cross fertilization.
2. 1. Anterior muscle - closureExhaust siphon
2. Esophagus 10. Inlet siphon
3. Stomach 11. Mouth, oral cavity
4. Liver 12. Leg
5. Heart 13. Gut
6. Kidney 14. Sex gland
7. Posterior muscle - closureGills
8. Anal hole
3. A) kidneys B) lungs and gills C) mantle D) horny, pearlescent E) liver, carbohydrates
4. 1,5,7,9
Option 2.
1. Squid, class Cephalopods. Bilaterally symmetrical, they have tentacles around the head, formed from the legs. They have a highly developed brain, the structure of the eye is similar to the structure of the eye of vertebrates. They can quickly change color to match the color of their environment. They have an ink sac. They have a closed circulatory system and several hearts (two gills and a main one). Two digestive glands - liver and pancreas). Dioecious.
2. 1. Digestive gland 9. Gills
2. Mantle 10. Muscles
3. Gonad 11. Sole
4. Heart 12. Gut
5. Kidney 13. Nerves
6. Shell 14. Mouth opening
7. Mantle cavity 15. Radula (tongue)
8. Anus 16. Stomach
3. A) tube, on the ventral side B) gills C) filtering D) cartilaginous skull, plates E) open, two-chambered heart
4. 2, 3, 10
References:
Biology: 7th grade: textbook for students of general education institutions /, ; edited by prof. . – 3rd ed. reworked – M.: Ventana-Graf, 2009
Part 1
Read the text carefully.
Shellfish
Who walks on the bottom on one leg? Who carries the house? These are riddles about shellfish. The snail lives in the garden, the pond snail in the pond, the oyster in the sea, but all these animals are mollusks: they all have a soft body.
To protect itself from enemies, the naked, helpless slug hides in its shell: in the pond snail it is single-leafed, in the toothless slug it is double-leafed. The oyster passes 770 liters of sea water through its body to extract the calcium it needs for its shell from the water!
Sometimes a grain of sand or an insect gets into the shell of a bivalve mollusk. The nacre that the mollusk secretes gradually envelops the grain of sand, and the tiny matte ball grows and grows. This is how a pearl is born.
The clam is not only a homeowner, but also a housekeeper. Pushing off from the bottom with a single leg inserted through the doors, the toothless crawls 20 cm in an hour. And the abalone, a fast walker among snails, transports its home at a speed of a meter per second.
The octopus and squid do not have a shell, but they have tentacles that replace legs. They are located on the head, which is why these mollusks are called cephalopods. When the octopus sleeps, six of its tentacles are motionless, but two, guarding, describe circles. Each tentacle of a large octopus has 300 suckers; each sucker can hold a load of several kilograms.
Part 2
Answer options are given for each task. Choose the correct answer or enter your answer where required. When completing tasks, do not forget to use the text you read.
1. How many exclamatory sentences are there in this text?
1) 1; 2) 2; 3) 3.
2. Why are octopuses and squids called cephalopods? Formulate and write down the correct answer. ___________.
3. How many suckers do five octopuses have?
1) 150; 2) 1500; 3) 15 000.
4. Note the main characteristic of all mollusks.
1) They hide in shells; 2) everyone has a soft body; 3) there are tentacles.
5. Mark the paragraph to which you can select the heading “The Birth of Pearls.”
1) 1; 2) 2; 3) 3.
6. Who lives where? (Connect with arrows.)
oyster pond
snail sea
pond snail garden
7. How many hours will it take for toothless to cover a distance of 1 meter?
1) In 3 hours; 2) in 4 hours; 3) in 5 hours.
8. Supplement the problem statement with data from the text and solve it. One oyster passes ____ liters of seawater through its body. How many liters of water will 30 oysters hold?
1) 800; 2) 2310; 3) 23100.
9. From the first sentence of the third paragraph, write down the grammatical basis.
10. Match (connect with arrows):
squid shell
octopus
toothless tentacles
11. The speed of the abalone snail is 1 m/s. How far can this snail cover in 1 hour?
1) 60 m; 2) 360 m; 3) 3600 m.
12. Mark the word that matches the pattern: prefix, root, suffix, ending.
1) house mover; 2) toothless; 3) pond snail.
13. In a word mollusk:
1) 7 letters, 7 sounds; 2) 7 letters, 6 sounds; 3) 6 letters, 7 sounds.
14. Letter O missing from the group's words:
1) ...octopus, k...lmar;
2) pond...vik, m...mullusk;
3) tentacle...lance, cancer...wine.
15. How does Toothless move? Indicate the number of the paragraph in which the answer to the question posed can be found.
1) 4; 2) 5; 3) 6.
16. In the third paragraph all the verbs...
1) I conjugation; 2) II conjugation; 3) I and II conjugations.
17. Scientists count about eighty thousand species of mollusks. Mark the correct answer entry.
1) 8000; 2) 80 000; 3) 800 000.
18. Re-read the fifth paragraph. How many tentacles of the five octopuses will be motionless, and how many will guard and describe circles?
1) motionless tentacles _____________________;
2) guarding tentacles ______________________.
19. Determine the gender, number and case of the adjective matte (ball).
Gender, __________ number, _____________ case
20. To protect yourself from enemies, a naked slug...
1) hides in the shell;
2) passes water through its body;
3) describes circles.
Answers to the test
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Question no. |
No. of the correct answer |
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The octopus and squid do not have a shell, but they have tentacles that replace legs, which are located on the head, which is why these mollusks are called cephalopods |
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snail – garden, pond snail – pond, oyster – sea |
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a grain of sand or an insect gets caught |
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Squid, octopus - tentacles, toothless - shell |
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30 – stationary, 10 – guarding |
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M.r., units, I.p. |
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Competency assessment
1–9 points- low level;
10–13 points– satisfactory level;
14–17 points- good level;
18–20 points– excellent level.
Slugs, oysters, squids, octopuses and other slippery creatures.
The type name itself comes from the Latin word "mollusk" - soft. Indeed, they have no backbone or bones; their entire body is soft and covered with mucus. Otherwise, mollusks are quite diverse.
The most common class of mollusks is gastropods living both in water and on land. They have only one leg, with which they slowly move along the ground or river bottom - these are snails, sea limpets, slugs, and pond snails.
Mussels
Bivalve live in a shell of two halves that can open and close like a book - these are mussels, oysters, scallops. Cephalopods- mainly marine predators living in the seas and oceans: nautiluses, cuttlefish, octopuses.
Cuttlefish (Sepia). Photo by Alexander Semenov
Very beautiful nudibranchs. They live exclusively in water, are completely devoid of shell, and their body is painted in bright colors. They are poisonous- therefore they can afford to be colorful and noticeable.
Nudibranch dendronotus (Dendronotus frondosus). Photo by Alexander Semenov
Among the representatives of this type of animal there are truly amazing creatures. The heaviest bivalve mollusk (tridacna gigantea) can weigh up to 250 kilograms, and the giant squid can reach a length of 18 meters. The dwarf octopus weighs only one gram, and its largest relative, the Pacific octopus, weighs more than 50 kilograms. Many mollusks are so amazing in shape and color that it is difficult to believe in their existence.
OK. No. 13. Biology.
7th grade.
Shellfish - 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 range from a few millimeters to 20 m. Most are sedentary animals, some lead an attached lifestyle (mussels, oysters), and only cephalopods are able to move quickly in a reactive manner.
Some mollusks are bilaterally symmetrical
(bilateral) animals ( But: at gastropods
shellfish appeared swirled shell, their
body - asymmetrical)
Hard mineral sink, covers the body
mollusk from the dorsal side. It consists
from crystals of calcium carbonate, from above
covered with horn-like organic matter,
and the inside is lined with a hard, shiny
lime layer - mother of pearl.
In some mollusks the shell is reduced (underdeveloped) or absent altogether. This happens when the mollusk lives in places where it is difficult for predators to reach (for example, when it burrows deep into the sand of the seabed or drills passages in the trunks of trees that have fallen into the sea). Slugs and mollusks that swim well have lost their shells. 
Various shellfish:
A - gastropod;
B - bivalve;
B - cephalopod:
2 - sink;
3 - tentacles
The body of mollusks consists of torso,
head and feet. On head located
mouth opening, tentacles and eyes.
Leg- muscular unpaired outgrowth
bodies. It is located on the abdominal
side and is used for crawling.
In bivalves shellfish due to
sedentary lifestyle head
absent, leg reduced.
In cephalopods shellfish - leg
turned into a swimming organ.
Internal structure.
The body of the mollusk is surrounded by skin
fold - mantle. Space
between the walls of the body and the mantle
called mantle cavity. There
open organ openings
discharge, genitals and anal
hole . It contains organs
breathing - gills .
Secondary body cavity ( in general) y
adults - stored as
pericardial sac and cavity
gonad. Gaps between
organs are filled with connective tissue
Digestion.Oral opening leads 
V throat. In the pharynx, many species have
grater ( radula). Using a grater
herbivorous molluscs scrape
food from plants, and predators grab
prey. In the oral cavity for some
predatory mollusks open salivary
glands– their secret contains poison.
should stomach, into which they open
ducts liver. Liver secretion dissolves
carbohydrates, food absorption also occurs in the liver. The stomach goes into gut ending anus.In bivalves feeding on microscopic algae suspended in water and small organic particles the pharynx, grater and salivary glands are lost.
Breath. In aquatic mollusks, the respiratory organs are paired gills, lying in the mantle cavity. Terrestrial molluscs breathe with the help lung- This a pocket of the mantle that is filled with air and communicates with the external environment through the breathing hole.
Circulatory system. The heart of mollusks consists
usually from three departments(one ventricle and
two atria ). Circulatory system open.
Some mollusks have in their blood manganese
or copper, like iron in the blood of higher animals
Provide oxygen transfer.
Excretory organs presented paired buds, which at one end communicate with the cavity of the pericardial sac which surrounds the heart, and the other open into the mantle cavity.
Nervous system. central nervous system
consists of several pairs ganglia(nodes),
connected by nerve trunks, from which to
nerves extend to the periphery - the nervous system nodal
type.
Sense organs - well developed organs touch,
chemical sense and balance.In mobile
shellfish available organs of vision. Especially good
eyes are developed in fast-swimming cephalopods.
Reproduction. Most shellfish dioecious.
However, there is also hermaphrodites for whom it occurs
cross fertilization. Fertilization in
there are shellfish external(at the oyster, toothless) and
internal(at the grape snail).
Development is either with incomplete metamorphosis or direct.
From a fertilized egg develops or larva,
leading a planktonic lifestyle (the so-called
sailboat), or a formed small mollusk.
Diversity and importance of mollusks.
OK. No. 14. Biology.
7th grade.
Class Gastropods:
Representatives - Black Sea
ramen, grape snail,
Peculiarities:
spiral-twisted shell,
muscular tongue grater,
2-chambered heart
breathing - gills or lungs
food – herbivores or carnivores
Class Bivalve:
Representatives - mussels, toothless,
pearl barley, oysters.
Peculiarities:
lack of head,
double shell,
feeding method - filtration
respiratory organs - gills,
3-chambered heart,
mostly dioecious
Class Cephalopods:
Representatives - octopus, squid,
cuttlefish, nautilus. 
Peculiarities:
no sink,
the body is divided: head, tentacles,
respiratory organs - gills;
3-chambered heart;
well developed sense organs;
the nervous system is complex
food - predators
The importance of mollusks in nature and in human life.
|
Positive |
Negative |
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1. Food chain in biogeocenosis. 2. Man uses it for food. 3.Water purity indicators, filter water. 4. They form nacre and pearls. 5. Watercolor paint is obtained from the secretions of the cuttlefish’s ink sac. 6.People use it to create souvenirs and jewelry. |
1. Terrestrial mollusks destroy cultivated plants. 2. Prudovik is an intermediate host of the liver fluke. 3. Marine, fixed to the bottom of the ship. 4. Skin molluscs are harmful to human health. Laboratory research No. 2(demonstration material). The structure of the shell of gastropods and bivalves. Toothless:
Grape snail: The snail's body is covered with a shell - solid, spirally twisted to the right; the spiral forms several (four) turns.
1 - 5 - head and its appendages (1 - head, 2 - labial tentacle, 3 - eye tentacle, 4 - eyes, 5 - mouth opening): 6 - leg; 7 - genital opening; 8 - breathing hole; 9-13 - details of the shell structure (9 - apex, 10 - turns of the spiral, 11 - last whorl, 12 - mouth, 13 - edge of the mouth) |
The appearance of the sink; 1
- front edge of the shell; 2
- ventral edge; 3
- rear edge; 4
- dorsal (lock) edge; 5
- crown; 6
- external ligament (ligament); 
