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Topic : "Class arachnids"
Goals:
educational : To acquaint students with the diversity and lifestyle of arachnids, structural features and life activities that allowed them to become one of the first settlers of land, their significance in nature and human life.
Educational : Contribute to the continuation of the formation of skills in working with tests for further preparation for the GIA and the Unified State Examination, working with reference signals, making presentations on the topic.
Educational : Learn careful attitude to nature, showing that each organism has its own place in the ecosystem, significance in nature and human life, its own unique history and originality.
Equipment: presentation, cards, tests
During the classes
II . Check of knowledge
Test "Test yourself"
Cancer breathes with gills (Yeah)
Cancer is diurnal (No).
The body of cancer is made up of two sections (Yes).
Cancer has simple eyes (No).
Crayfish are herbivorous (No).
Cancer always moves backwards (No).
With the help of walking legs, the crayfish moves along the bottom (Yes).
The circulatory system of cancer is open (Yes).
The mobility of the cancer's eyes compensates for the immobility of the head (Yes).
Crayfish are "orderlies" of reservoirs (Yes).
Cancer traps food in the jaws and sends it to the mouth (Yes).
Claws are organs of defense, attack, food capture (Yes).
Cancer's blood is red (No).
Cancer females lay eggs in winter (Yes).
Let's check how you have learned this topic and do a little written check. So, pack up and get ready to work. Getting Started (1 min)
Now put your pens down, swap cards with your desk partner, grab some pencils, and evaluate your partner's work.
If there are no mistakes - we put 5, if there is 1 mistake - we put a mark of 4, for 2 mistakes, unfortunately, a mark of 3.
And now we return our leaves.
Stand up, please, those who received 5. Sit down. Excellent!
And who will have a mark of 4 for today's lesson? Have a seat. Good!
Is there a rating lower than 4? Stand up please. You have something to work on. But do not be upset, in the future you will definitely succeed. But at home you should repeat the theme "Class Crustacea". And if you have questions about your work, come after the lesson, we will discuss everything.
II I . Learning new material
– Let's list again the 3 classes of the phylum Arthropods that we study: Crustaceans; arachnids; Insects.
Listen to what one of the ancient Greek legends says.
In ancient times, Arachne lived in Lydia - the daughter of the purple dyer Idman. She was famous for the fact that she had no equal in the art of weaving patterned fabrics and weaving carpets. Soon Arachne imagined herself equal to the gods, equal to the sun.
Hey Pallas...
I predict, and what was said will soon come true,
Soon I will weave a carpet, which was not in the world,
And your skill cannot be compared with mine, O Athena,
I have no equal either on the sinful earth, or in the cloudless heights,
There is only one craftswoman in this world, and that is Arachne!
Arachne wove cloth no worse than Athena. But she, in punishment for the audacity to compete with the gods, did not recognize her merits and punished Arachne for pride and vanity.
Damn you, you spin a web for a century,
Be the ugly Arachne that people
They will persecute and persecute always and forever
They will be afraid of you, and crush, and tear the web.
And your skill, of which you were so proud,
May it remain with you in consolation forever with you:
You will sit in the corner and weave a web forever.
Here is such a legend!
Guys, on behalf of Arachne happened Latin name spiders, which are called in Latinarachnids.
The science of spiders is calledarachnology.
And as you probably already guessed, the topic of our lesson is the Class Arachnids.
– The task of our lesson: to find out not only the structure of spiders using the example of a cross, but also to talk about which arthropods are included in the class Arachnids, what role they play in nature and human life. Recording the topic: “Class Arachnids.”
The class Arachnida includes up to 62,000 species.
itharvestmen, ticks, spiders, scorpions and etc. almost all of them are terrestrial animals, except for some types of spiders. Many weave webs.
In this regard, the structure of their body differs from the structure of the body of other arthropods.(Not pop, but with a cross - who?) Consider it using the example of the structure of the body of a spider-cross.
1. Habitat and external structure of arachnids. (Performing the task below, conversation)
Use your textbook to prepare answers to the following questions:
How many body parts does a spider have? What are their names? (Head-thorax, abdomen)
How many pairs of walking legs does a spider have? What part of the body are they attached to?(4 pairs of walking legs attached to the cephalothorax)
What organs can be seen in a spider? Does a spider have antennae? How many eyes?(There are 4 pairs of eyes on the spider's head, and below, hook-shaped hard jaws - chelicerae. Next to the chelicerae are short, sensory hair-covered organs of touch - leg tentacles. Arachnids do not have antennae.)
Are there limbs on the abdomen?(Not).
The body consists of 2 sections - the cephalothorax and the abdomen. The abdomen is separated from the cephalothorax by constriction. They do not have antennae and compound eyes. There are 4 pairs of legs on the cephalothorax.
Also several pairs of simple eyes; and below the jaw - chelicerae. The spider grabs its prey with them. Inside there is a channel with poison. There are short hairy tentacles, or pedipalps (organs of touch).
I don't sew clothes for myself.
And the fabric is always weaving.
About whom in question?
Let's listen to the message about the web.
Weaving a diverse web - instinctive process. Each type of spider has its own web pattern. The web of spiders is especially strong and thin. The web is used to make sights (crossing threads in the eyepieces of various devices). Attempts to make fabrics from cobwebs have been made for a long time. Exceptional in strength, lightness and beauty, web fabric is known in China under the name "fabric east sea". Polynesians used cobwebs
large web spiders as threads for sewing and weaving fishing tackle. At the beginning of the XVIII century. in France, gloves and stockings were made from the web of crosses, presented to the Academy of Sciences and aroused universal admiration. It is known that the thread of the web can be wound directly onto the coil, and sometimes from one cross you can get a thread up to 500 m long. In 1899, they tried to get a fabric for covering
airship, a sample of luxurious fabric 5 m long was made. Production of gossamer silk
faces the difficulty of mass breeding of spiders, most importantly - with their feeding.
How do spiders weave webs?
From the bottom on the abdomen are arachnoid warts that produce cobwebs. These are modified abdominal legs. The liquid released from the spider web warts instantly hardens in the air and turns into a strong spider web.
There are comb-like claws on the hind legs, which help to pull the web threads from the glands and collect them into one. Up to 4 km of web can be pulled out of the web warts of one spider.
Why do spiders need a web?
They need the web to catch prey, to make cocoons, to protect the eggs from adverse effects. Therefore, it can be of several varieties: dry, wet, sticky, corrugated. It serves for different purposes. The web is thinner and stronger than the threads of the silkworm caterpillar.
Abbé Combouet lived in the world, he was such an inventor: he connected living spiders in small drawers directly to a special type of loom. The loom pulled threads from spiders and immediately wove the finest silk from them.
But industrial production such threads cannot be established, because spiders are very gluttonous and you will not get enough of flies, and the climate is not suitable everywhere.
Videos spider web
A spider weaves a trapping web from cobweb threads. First, a frame with rays converging towards the center, then a long, thin and very sticky thread, placing it in the center of the spiral. Then, in anticipation of prey, he sits near the net in a hidden nest made of cobwebs. A signal thread is stretched from the center of the network to it.
– Observations of the behavior of the spider show that it jumps out of its hiding place, rapidly heading towards the fly, only if there is a medium-sized fly: if a small fly hits, then the spider does not pay attention to it.
How does a spider know the size of its prey?
(The spider, with the help of special sensitive organs on its legs, perceives the vibrations of the web and, by their strength, learns how large the fly is. If the vibrations are strong, the spider rushes to the victim and breaks the threads, freeing it and saving the rest of the web)
He plunges the claws of the upper jaws into the victim and injects poison into the victim; but not only poison, but also digestive juices, tk. cannot eat solid food. An hour later, the spider returns and sucks up the prey with the help of a sucking stomach, and only the chitinous shell remains from the victim. Such digestion is called extraintestinal.
2. The internal structure of the spider - cross. (Teacher's story)
In the course of the explanation, students paint over the internal organs of the spider on the cards
1. Digestive system.
Consists of the mouth, pharynx, esophagus, stomach and intestines. In the intestine there are outgrowths that increase the volume and surface of absorption. Undigested residues are brought out through the anus. Digestion of food is extraintestinal.
2. Respiratory system.
The respiratory organs of the spider are the lungs and trachea. Lungs or pulmonary sacs are located below, in front of the abdomen. The cross spider has 2 pairs of tracheas - tubes that deliver oxygen to organs and tissues. They are located in the back of the abdomen.
3.Circulatory system like crabs. Which?
– Open. Hemolymph circulates in the body. The heart looks like a tube located on the back side of the abdomen. Blood vessels branch off from the heart
4. Excretory system. Tubules are Malpighian vessels. At one end they collect metabolic products, and at the other they flow into the intestines. Excreted through the Malpighian vessels harmful products life in liquid form. Water is absorbed in the intestines. Therefore, spiders save water and can do without it (a vicious circle of water consumption).
5.Nervous system. It consists of the cephalothoracic ganglion and numerous nerves extending from it.
6. Reproduction. Separate animals. In the gonads of the male, spermatozoa develop, and in females, eggs. Fertilization is internal in the body of the female. After some time, the female lays eggs either openly or braids them with cobwebs and forms a cocoon. The eggs develop into small spiders. In autumn, they release cobwebs, and on them, like on parachutes, they are carried by the wind - spiders are resettled.
3. Variety of arachnids (watch video)
– In addition to Spiders, ticks also belong to Arachnids (message)
dust mite indistinguishable to the naked eye. In an apartment, there are millions of these creatures per person. They live in carpets, in bedding, on clothes. The airborne microscopic bodies of dust mites and the enzymes they secrete are the most common cause of asthma and allergic reactions. Prevention of such diseases is frequent airing of the premises and heating it with sunlight.
And Nikita will tell us about one more detachment that belongs to arachnids
scorpions live in the subtropics and deserts, have a body up to 15 cm long. The body of scorpions also consists of the cephalothorax and abdomen. The abdomen has a fixed and wide anterior part and a narrow, long movable posterior part. At the end of the abdomen there is a swelling (the poisonous gland is located there) with a sharp hook. A poisonous apparatus is necessary for scorpions to kill prey and to protect themselves from enemies.It used to be believed that the scorpion kills itself at a critical moment with its poisonous sting. But, as it turned out, he is just pretending: he “twists”, taking the most incredible poses, after which he freezes for a long time. You can observe this behavior at home, surrounding the animal with hot coals. For some time, the scorpion will rush about in search of a way out, but, realizing the futility of its attempts, it will do exactly what it used to strike people so much,however, after a while, the scorpion "comes to life". For a person, a scorpion sting is very painful and can lead to death. The tentacles of scorpions are claw-shaped and resemble the claws of crayfish and crabs.
So we found out that spiders, ticks and scorpions actually belong to arachnids.
– Are arachnids necessary in nature?
– If there were no spiders, people could die from various diseases, as they are carried by flies, and as scientists calculated, armed with a microscope, there are 26,000,000 microbes on the body of one fly.
– They are food for birds.
– Participate in soil formation.
– Some are harmful to plants, animals and humans.
– They are carriers of diseases.
I V . Consolidation of knowledge
Task number 1. "Silent Drawings"
Task number 2 .If you were attentive in the lesson, then you can easily cope with
next task. I will name any sign and if this sign
refers to arachnids, then we raise a green card, if not, an orange one.
1. The body of animals outside has a chitinous cover.green
2. The body consists of two sections: cephalothorax and abdomen.green
3. The abdomen is jointed.orange
4. The abdomen is non-segmented.green
5. Animals have 4 pairs of legs.green
6. There are antennae on the head.orange
7. No antennae.green
8. Antennae 2 pairs - long and short.orange
9. Animals have simple eyes.green
10. Most animals have two compound compound eyes.orange
11. Respiratory organs - gills.orange
12. Tracheal-pulmonary breathing.green
13. The circulatory system is not closed.green
14. The nervous system consists of the peripharyngeal ring and the abdominal
nerve chain.green
15. Animals have a "sucking" stomach.green
16. Organs of excretion - Malpighian vessels.green
17. Dioecious animals.green
Answers: 1,2,4,5,7,9,12,13, 14, 15, 16,17.
Task number 3. Test execution (backup)
V. Summary of the lesson
What new did you learn abouttoday's lesson?
What conclusion is fashionable to draw?
Arachnids - predominantlyterrestrial, eight-leggedanimals, typical for spidersweb weaving. UnlikeCrustaceans breathe with lungs andtracheae, have simple eyes. Features of the structure are associated with the environment and lifestyle.
The lesson ends with a poem:
Everyone is afraid of spiders
More than anything in the world
And they are especially afraid
Small children;
Don't chase the spiders
Small children:
Catch flies and mosquitoes
Good neighbors!
Venomous spiders -
It is certain!
But not just touched
Let's be frank.
V I . Homework .
1) § 25 2) make a crossword "Arachnids"
About 25 thousand species of arachnids are known. These arthropods are adapted to living on land. They are characterized by respiratory organs. As a typical representative of the class Arachnids, consider the cross-spider.
The external structure and nutrition of arachnids
In spiders, the segments of the body merge, forming the cephalothorax and abdomen, separated by interception.
The body of arachnids is covered chitinized cuticle and the underlying tissue (hypoderm), which has a cellular structure. Its derivatives are spider and poisonous glands. The poisonous glands of the cross spider are located at the base of the upper jaws.
A distinctive feature of arachnids is the presence six pairs of limbs. Of these, the first two pairs - the upper jaws and leg tentacles - are adapted to capture and grind food. The remaining four pairs perform the functions of movement - these are walking legs.
During embryonic development, the abdomen is laid big number limbs, but later they are transformed into spider warts, opening the ducts of the spider glands. Hardening in air, the secretions of these glands turn into cobwebs, from which the spider builds a trapping web.
After the insect has got into the net, the spider wraps it in cobwebs, sticks the claws of the upper jaws into it and injects poison. It then leaves its prey and hides for cover. The secret of poisonous glands not only kills insects, but acts as digestive juice. After about an hour, the spider returns to its prey and sucks out semi-liquid, partially digested food. From the killed insect, one chitinous cover remains.
Respiratory system in the cross-spider, it is represented by lung sacs and tracheae. lung bags and the tracheae of arachnids open outward through special openings on the lateral parts of the segments. In the lung sacs there are numerous leaf-like folds in which blood capillaries pass.
Trachea They are a system of branched tubules that go directly to all organs, where tissue gas exchange takes place.
Circulatory system arachnids consists of a heart located on the dorsal side of the abdomen and a vessel through which blood moves from the heart to the front of the body. Since the circulatory system is not closed, the blood returns to the heart from the mixed body cavity (myxocele), where it washes the lung sacs and trachea and is enriched with oxygen.
excretory system The spider-cross consists of several pairs of tubes (Malpighian vessels) located in the body cavity. Of these, waste products enter the posterior intestine.
Nervous system arachnids are characterized by the fusion of nerve nodes with each other. In spiders, the entire nerve chain merges into one cephalothoracic ganglion. The organ of touch is the hairs that cover the limbs. The organ of vision is 4 pairs of simple eyes.
Reproduction of arachnids
All arachnids are dioecious. The female cross-spider lays eggs in autumn in a cocoon woven from a silky web, which she attaches in secluded places (under stones, stumps, etc.). By winter, the female dies, and spiders emerge from the eggs that have overwintered in a warm cocoon in the spring.
Other spiders also take care of their offspring. For example, a female tarantula carries her young on her back. Some spiders, having laid their eggs in a web cocoon, often carry it with them.
Task 1. "Arachnids"
Write down the question numbers and missing words (or groups of words):
1. The class Arachnida combines more than (_) species of animals.
The cephalothorax bears (_) pairs of limbs. Ticks have a body (_). On the abdomen of arachnid limbs (_). The first pair of limbs of the cephalothorax is called (_), consists of 2-3 segments, ends with a hook, claw or stylet. The second pair of limbs is called (_) and are used as: walking legs, organ of touch, lower jaw, claws for grabbing food, as a copulatory apparatus. Walking legs - (_). Spider saliva contains enzymes that aid digestion outside the spider's body - (_) digestion. The respiratory organs of the cross spider - (_) The excretory system is represented by (_), which open at (_). Development in spiders (_). More than (_) thousand species of spiders are known, ticks - (_) thousand species. oral apparatus ticks (_) or (_).
Task 2. "The structure of the spider-cross"
1. What is indicated in the figure by the numbers 1 - 17?
2. How is the circulatory system of a spider different from that of a cancer?
3. How do the respiratory organs of the cross differ from those of crayfish?
Task 4. "Variety of arachnids"
Look at the picture and answer the questions:
|
1. What are the representatives of the arachnids shown in the picture called?
2. Which units do these representatives belong to?
Task 5. "Arachnids"
Write down the numbers of tests, against each - the correct answers
**Test 1. What features are characteristic of external structure arachnids?
The body consists of three sections: head, thorax and abdomen. The body consists of two sections: the cephalothorax and abdomen, or all sections are fused. There are 5 pairs of limbs on the cephalothorax. There are six pairs of limbs on the cephalothorax. There are four pairs of walking legs. There are five pairs of walking legs. There are no mustaches. Antennae one pair. The eyes are simple. Faceted eyes.
** Test 2. What features are characteristic of the internal structure of arachnids?
The body cavity is secondary (as a whole). The body cavity is mixed (myxocoel). Gill breathing. Breathing through the lungs and trachea. The circulatory system is not closed. The circulatory system is closed. Heart in the head. Heart in the abdomen. The excretory system is represented by the anus. The excretory system is represented by malpighian vessels. The nervous system is represented by the supraglottic and subpharyngeal nodes and the cephalothoracic node. The nervous system is scattered-nodal type.
**Test 3. Indicate the features characteristic of the cross-spider:
The body consists of three sections: head, thorax and abdomen. The body consists of two sections: the cephalothorax and the abdomen. 4 pairs of walking legs. In total, there are 6 pairs of limbs on the cephalothorax. The first pair of limbs are the tentacles. The second pair of limbs are jaws, chelicerae. Digestion in the cross-spider is extraintestinal. There are three pairs of arachnoid warts on the abdomen. Spider warts are modified abdominal legs. There are two pairs of non-branching tracheae and lungs. Breathe only through trachea.
**Test 4. Ticks are characterized by the following features:
Test 5. In a spider-cross, poisonous glands are located:
In the jaws In toenails. In the mouth. At the end of the abdomen.
Test 6. What is the name of the second pair of limbs of the cross spider?
Jaws. Leg tentacles. Pincers. Walking legs.
Test 7. What are the organs of vision of the cross spider?
2 compound compound eyes. 2 compound and 2 simple eyes. 4 simple eyes. 8 simple eyes.
Test 8. Where is the heart of the cross spider?
In the back of the cephalothorax. In the abdominal part of the cephalothorax. At the top of the abdomen. At the bottom of the abdomen.
Test 9. What kind of digestion is typical for a spider-cross?
The main digestion is in the stomach. The main digestion is in the intestines. Food is digested in the long blind outgrowths of the midgut. Digestion of food begins outside the body and ends in the digestive system.
Test 10. The respiratory organs of the spider-cross are:
Only trachea. Gills and lungs. Tracheae and gills. Lungs and trachea.
Test 11. What departments does the body of ticks consist of?
From the head, chest and abdomen. From the head and abdomen. From the cephalothorax and abdomen. All parts of the body are merged into one.
Test 12. What ticks can infect a person with a serious disease - tick-borne encephalitis?
Ixodid ticks. Scabies mite. Spider mite. Varroa mite
Task 6. “Set-off. Class Arachnids»
Write down the question numbers and answer in one sentence:
How many species are in the class Arachnida? What antennae are found on the cephalothorax of a spider? How many and what kind of eyes are on the cephalothorax of a cross-spider? How many and what kind of limbs does a cross spider have? What organs open into the intestines of the cross? Where does digestion take place in the cross? What structural features of the midgut increase its absorption surface? In what part of the body is the heart of the cross? What kind of blood enters the heart of the cross? What are the respiratory organs of the cross? What are the excretory organs of the cross? What is the main product of protein metabolism in arachnids? What are the features of the nervous system of the cross? What kind of fertilization do spiders have? What is the development of spiders? In which representatives of arachnids, the head, chest and abdomen merged into one whole?
Task 7. "The most important terms and concepts of the topic"
Define the terms or expand the concepts (in one sentence, emphasizing the most important features):
1. Mandibles. 2. Maxillas. 3. Green glands. 4. Malpighian vessels. 5. Hemolymph. 6. Chelicerae. 7. Pedipalps. 8. Trachea. 9. Coxal glands. 10. Hemocyanin. 11. Guanine.
Answers:
Exercise 1. 1. Up to 60 thousand. 2. Six. 3. One-piece. 4. None. 5. Chelicerae. 6. Leg tentacles. 7. Four couples. 8. Extraintestinal. 9. Lung bags and tracheas. 10. Malpighian tubules opening into the intestine between the midgut and hindgut and coxal glands opening at the base of the walking legs. 11. Direct. thousand, 20 thousand. 13. Piercing-sucking or gnawing.
Task 2. 1. 1 - simple eyes; 2 - chelicerae, jaws; 3 - pedipalps (leg tentacles); 4 - walking legs; 5 - light; 6 - arachnoid warts. 2. Eight. 3. Four couples. 4. At the base of the chelicerae. 5. Behind chelicerae. 6. Three couples. 7. Missing. 8. Chitinized cuticle.
Task 3. 1. 1 - oral opening; 2 - pedipalps; 3 - chelicerae; 4 - poisonous gland; 5 - simple eyes; 6 - brain; 7 - stomach; 8 - anterior aorta; 9 - intestines; 10 - heart; 11 - ovary; 12 - anus; 13 - openings of arachnoid warts; 14 - spider glands; 15 - genital opening; 16 - lung 17 - four pairs of legs. 2. The heart is in the abdomen, not in the cephalothorax. 3. Represented by two lung sacs and two tracheal bundles.
Task 4. 1. 1 - scorpion; 2 - salpuga (phalanx); 3 - ticks (flour, shell and taiga); 4 - spider-cross. 2. Scorpio to the squad of Scorpions; solpuga to the Solpuga detachment; spider-cross to the Spider squad; ticks to the order Ticks.
Task 5 **Test 1: 2, 4, 5, 7, 9. **Test 2: 2, 4, 5, 8, **Test 3: 2, 3, 4, 7, 8, 9, 10. **Test 4: 1. 2, 4, 7, 8, 9. Test 5: 1. Test 6: 2. Test 7: 4. Test 8: 3. Test 9: 4. Test 10: 4. Test 11: 4. Test 12: 1.
Task 6. 1. 30 thousand species. 2. None. 3. Eight simple ones. 4. Six pairs: chelicerae, pedipalps and four pairs of walking legs. 5. Malpighian vessels and liver. 6. First - extraintestinal, ends in the intestine. 7. Blind outgrowths. 8. In the abdomen. 9. Arterial - from the respiratory system. 10. Tracheas and lungs. 11. Malpighian tubes and coxal glands. 12. Guanine. 13. Further concentration is observed - consists of the brain and cephalothoracic ganglion. 14. Internal. 15. Direct. 16. In ticks.
Task 7. 1. Upper jaws in arthropods. 2. Lower jaws in arthropods. 3. The excretory organs of crustaceans, modified coelomoducts, open at the base of the antennae or the second pair of maxillae. 4. Organs of excretion in land arthropods that flow into the intestines. 5. Fluid circulating in the vessels and intercellular cavities of invertebrates with an open circulatory system. 6. The first pair of jointed head limbs in chelicerates. They are used as jaws for grasping and tearing prey. 7. The second pair of jointed oral limbs of the cephalothorax in chelicerates. 8. Ectodermal invaginations in the form of tubules that conduct air from the external environment to the tissues. 9. Kidneys in arachnids, whose ducts open at the base of the legs. 10. The respiratory pigment of the hemolymph, which transports oxygen, contains copper, the oxidized form has a blue tint. 11. Purine nitrogenous base, the end product of nitrogen metabolism in arachnids.
The cross spider (Araneus) is an arthropod belonging to the genus of araneomorphic spiders and the family of orb-weavers (Araneidae). To date, there are more than one thousand species of crosses in the world, which live almost everywhere.
Description of the cross
The external structure of the cross is represented by the abdomen and arachnoid warts, the cephalothorax and walking legs, consisting of the thigh, knee joint, lower leg, pretarsus, paw and claw, as well as the chelicera and pedipalp, acetabular ring and coxa.
Appearance
Crosses are spiders quite small in size, however, the female of this arthropod is much larger than the male. The body length of the female is 1.7-4.0 cm, and the size of an adult male cross, as a rule, does not exceed 1.0-1.1 cm. time for another molt. Along with most arachnid species, spiders have ten limbs, represented by:
- four pairs of walking legs with relatively sharp claws at the ends;
- one pair of pedipalps, which perform a recognizing function and are necessary to hold the caught prey;
- one pair of chelicerae used in the capture and killing of the caught victim. The chelicerae of the crosses are directed downwards, and the hooks of the chelicerae are directed inward.
Adult males on the last segment of the pedipalps have a copulatory organ, which is filled immediately before mating with seminal fluid, which enters the seminal receptacle located on the female, due to which offspring appears.
It is interesting! The visual abilities of the cross are very poorly developed, so the arthropod sees poorly and is able to distinguish only blurry silhouettes, as well as the presence of light and shadows.
Cross spiders have four pairs of eyes, but are almost completely blind. An excellent compensation for such a visual deficiency is a well-developed sense of touch, for which special tactile hairs located on the entire surface of the body are responsible. Some hairs on the body of an arthropod are able to respond to the presence of chemical stimuli, other hairs perceive air vibrations, and still others capture all kinds of ambient sounds.
The abdomen of cross-spiders is rounded and completely devoid of segments. In the upper part there is a drawing in the form of a cross, and on the lower part there are three pairs of special spider warts, which contain almost a thousand glands that produce spider webs. Such strong threads have various purposes: building reliable trapping nets, arranging protective shelters or weaving a cocoon for posterity.
The respiratory system is located in the abdomen and is represented by two lung sacs, in which there is a significant number of leaf-shaped folds with air. Inside the folds, liquid hemolymph circulates, enriched with oxygen. Also included in respiratory system includes tracheal tubes. In the dorsal region of the abdomen is the heart, which, with its appearance resembles a rather long tube with outgoing, relatively large blood vessels.
Types of crosses
Despite the fact that there are a lot of varieties of cross-spiders, only thirty species are found on the territory of our country and in neighboring states, which are characterized by the presence of a pronounced “cross” located on the upper part of the abdomen. Common species include the four-spotted or meadow cross spider (Araneus quadratus), which settles in wet and open, grassy areas.
It is interesting! Of particular interest is the rather rare spider Araneus sturmi, which lives mainly in conifers on the territory of the Palearctic region, whose modest size is compensated by a rich variety of colors.
The common cross (Araneus diadematus), whose body is covered with a waxy substance that retains moisture, as well as a rare species listed in the Red Book called the angular cross (Araneus angulatus), which is characterized by the fetal absence of a cruciform pattern and a pair of small the size of the humps in the abdomen.
How long does a cross live
cross spiders different types, compared to many of their counterparts, live quite a short time. Males die immediately after mating, and females die immediately after weaving a cocoon for offspring.
Thus, the life expectancy of male crosses does not exceed three months, and females of this species can live for about six months.
Spider venom
The venom of the cross is toxic to vertebrates and invertebrates, as it contains thermolabile hemolysin. This substance can adversely affect the red blood cells of animals such as rabbit, rat and mouse, as well as human blood cells. As practice shows, a guinea pig, a horse, a sheep and a dog have a fairly high resistance to the toxin.
Among other things, the toxin has an irreversible effect on the synaptic apparatus of any invertebrate animal. For human life and health, crosses are in most cases absolutely harmless, but if there is a history of allergies, the toxin can cause a strong burning sensation or local tissue necrosis. Small cross-spiders are capable of biting through human skin, but the total amount of venom injected is most often harmless, so its presence under the skin is accompanied by mild or quickly passing pain symptoms.
Important! According to some reports, the bites of the largest crosses of some species are no less painful than the sensations after a scorpion sting.
Cross web
As a rule, crosses settle in the crown of a tree, between branches, where large trapping nets are arranged by a spider. The foliage of the plant is used to make shelter. Quite often, a spider web is found in shrubbery and among window frames in abandoned buildings.
The cross spider destroys its web every other day and starts making a new one, as the trapping nets become unusable because not only small, but also too large insects get into them. Usually, new network trudges at night, which allows the spider to catch prey for itself in the morning. The webs built by an adult female cross spider are distinguished by the presence of a certain number of spirals and radii woven from sticky threads. The distance between adjacent coils is also precise and constant.
It is interesting! Due to their very high strength and high elasticity, crosses have long been widely used in the manufacture of fabrics and various decorations, and among the inhabitants of the tropics they still serve as a material for weaving nets and fishing nets.
The building instinct of the spider-cross is brought to automatism and programmed in nervous system at the genetic level, so even young individuals are able to very easily build high-quality cobwebs and quickly catch the prey necessary for food. The spiders themselves use exclusively radial, dry threads for movement, so the cross is not able to stick to trapping nets.
Range and habitats
The most common representative is the common cross (Araneus diadematus), found throughout the European part and in some North American states, where spiders of this species inhabit coniferous forests, swampy and shrub plantings. Angular cross (Araneus angulatus) - disappearing and very rare view living in our country, as well as on the territory of the Palearctic region. The Australian cross spider Araneus albotriangulus also inhabits the territory of New South Wales and Queensland.
On the territory of our country, oak cross-spiders (Araneus seroregius or Aculeira seroregia) are most often found, which settle in tall grass on forest edges, in groves and gardens, as well as in fairly dense shrub thickets.
The Araneus savaticus cross, or barn spider, uses grottoes and rocky cliffs to equip the trapping net, as well as inlets in mines and barns. Quite often, this species settles in close proximity to human dwellings. The cat-faced cross-spider (Araneus gemmoides) lives in the western part of America and Canada, and India, Nepal, the territory of Bhutan and part of Australia became the natural habitat of a typical representative of the Asian fauna of the spider-spider Araneus mitificus or "Spider Pringles".
Food, mining of the cross
Spiders, along with most other spiders, have an external type of digestion.. In anticipation of their prey, spiders are usually located near the network, located in a hidden nest, which is made of a strong web. A special signal thread is stretched from the central part of the web to the spider nest.
The main diet of the cross is represented by a variety of flies, mosquitoes and other small insects, which an adult spider can eat about a dozen at a time. After a fly, a small butterfly or any other small insect enters the net and begins to beat inside it, a noticeable oscillation of the signal thread immediately occurs, and the spider leaves its hiding place.
It is interesting! If a poisonous or very large insect is caught inside the web trap, the cross spider quickly breaks the web to get rid of it. Also, crosses strenuously avoid contact with insects that can lay eggs in other arthropods.
The arthropod is unable to digest the caught prey on its own, therefore, as soon as the victim gets into the network, the cross spider quickly injects its very aggressive, caustic digestive juice into it, after which it wraps the prey in a cocoon from the web and waits for some time, during which the food is digested and turns into a so-called nutrient solution.
The process of digestion of food in a cocoon usually takes no more than one hour, and then the nutrient fluid is absorbed, and only a chitinous cover remains inside the cocoon.
Representatives of arachnids are eight-legged land arthropods, in which the body is divided into two sections - the cephalothorax and abdomen, connected by a thin constriction or fused. Arachnids do not have antennae. Six pairs of limbs are located on the cephalothorax - two front pairs (mouth organs), which serve to capture and grind food, and four pairs of walking legs. There are no legs on the abdomen. Their respiratory organs are lungs and trachea. The eyes of arachnids are simple. Arachnids are dioecious animals. The class Arachnida includes more than 60 thousand species. The body length of various representatives of this class is from 0.1 mm to 17 cm. They are widely distributed throughout the globe. Most of them are land animals. Among ticks and spiders there are secondary water forms.
The biology of arachnids can be considered using the example of a spider-cross.
External structure and lifestyle. The cross-spider (so named for the cross-shaped pattern on the dorsal side of the body) can be found in the forest, garden, park, on the window frames of village houses and cottages. Most of the time, the spider sits in the center of its trapping web of sticky thread - cobwebs.
The body of the spider consists of two sections: a small elongated cephalothorax and a larger spherical abdomen (Fig. 90). The abdomen is separated from the cephalothorax by a narrow constriction. At the anterior end of the cephalothorax, there are four pairs of eyes above, and below, a pair of hook-shaped hard jaws - a chelicerae. With them, the spider grabs its prey. There is a canal inside the chelicerae. Through the channel, poison from the poisonous glands located at their base enters the body of the victim. Next to the chelicerae are short, covered with sensitive hairs, the organs of touch - the leg tentacles. Four pairs of walking legs are located on the sides of the cephalothorax. The body is covered with a light, strong and rather elastic chitinous cover. Like crayfish, spiders periodically molt, dropping their chitinous cover. At this time they are growing.
Rice. 90. The external structure of the spider: 1 - leg tentacle; 2 - leg; 3 - eye; 4 - cephalothorax; 5 - abdomen
At the lower end of the abdomen there are three pairs of arachnoid warts that produce cobwebs (Fig. 91) - these are modified abdominal legs.
Rice. 91. Trapping nets of various types of spiders (A) and the structure (with magnification) of the spider web (B)
The liquid released from the spider web warts instantly hardens in the air and turns into a strong spider web. Various parts of arachnoid warts secrete cobwebs different types. Spider threads vary in thickness, strength, stickiness. different types The spider uses cobwebs to build a trapping net: at its base, the threads are stronger and not sticky, and the concentric threads are thinner and stickier. Spiders use the web to strengthen the walls of their shelters and to make cocoons for their eggs.
Digestive system the spider consists of a mouth, pharynx, esophagus, stomach, intestines (Fig. 92). In the midgut, long blind outgrowths increase its volume and absorption surface. Undigested residues are brought out through the anus. The cross spider cannot eat solid food. Having caught prey, such as some kind of insect, with the help of a web, he kills him with poison and lets digestive juices into his body. Under their influence, the contents of the caught insect liquefies, and the spider sucks it out. Only an empty chitinous shell remains from the victim. This type of digestion is called extraintestinal.
Rice. 92. The internal structure of the spider-cross: 1 - poisonous gland; 2 - mouth and esophagus; 3 - stomach; 4 - heart; 5 - lung sac; 6 "- sex gland; 7 - trachea; 8 - spider gland; 9 - intestine; 10 - Malpighian vessels; 11 - outgrowths of the intestine
Respiratory system. The respiratory organs of the spider are the lungs and trachea. Lungs, or lung bags, are located below, in front of the abdomen. These lungs evolved from the gills of distant ancestors of aquatic spiders. The spider-cross has two pairs of non-branching tracheas - long tubes that deliver oxygen to organs and tissues. They are located in the back of the abdomen.
Circulatory system spiders are open. The heart looks like a long tube located on the dorsal side of the abdomen. Blood vessels branch off from the heart.
In a spider, like in crustaceans, the body cavity has mixed nature- in the course of development, it occurs when the primary and secondary cavities of the chela are connected. Hemolymph circulates in the body.
excretory system It is represented by two long tubes - Malpighian vessels.
With one end, the Malpighian vessels blindly end in the body of the spider, with the other they open into the posterior intestine. Through the walls of the Malpighian vessels, harmful waste products come out, which are then brought out. Water is absorbed in the intestines. In this way, spiders conserve water, so they can live in dry places.
Nervous system The spider consists of the cephalothoracic ganglion and numerous nerves extending from it.
Reproduction. Fertilization in spiders is internal. The male carries the spermatozoa into the female genital opening with the help of special outgrowths located on the front legs. The female, some time after fertilization, lays eggs, braids them with cobwebs and forms a cocoon (Fig. 93).
Rice. 93. Female spider with a cocoon (A) and the resettlement of spiders (B)
The eggs develop into small spiders. In autumn, they release cobwebs, and on them, like on parachutes, they are carried by the wind over long distances - spiders are resettled.
Variety of arachnids. In addition to the cross-spider, about 20 thousand more species belong to the order Spiders (Fig. 94). A significant number of spiders build trapping webs from the web. Y different web spiders differ in shape. So, in a house spider living in a person’s housing, trapping net resembles a funnel, in a poisonous, deadly for humans karakurt, the trapping net resembles a rare hut. Among spiders there are also those that do not build trapping webs. For example, side-walker spiders sit in ambush on flowers and wait for small insects arriving there. These spiders are usually brightly colored. Jumping spiders are able to jump and thus catch insects.
Rice. 94. Various spiders: 1 - cross-spider; 2 - karakurt; 3 - spider regiment; 4 - crab spider; 5 - tarantula
Wolf spiders roam everywhere looking for prey. And some spiders sit in minks in ambush and attack insects crawling nearby. These include a large spider that lives in southern Russia - a tarantula. The bites of this spider are painful for humans, but not fatal. The Haymakers include very long-legged arachnids (about 3,500 species) (Fig. 95, 2). Their cephalothorax is indistinctly separated from the abdomen, the chelicerae are weak (therefore, haymakers feed on small prey), the eyes are located in the form of a “turret” on top of the cephalothorax. Harvestmen are capable of self-mutilation: when a predator grabs a haymaker by the leg, he discards this limb, and he runs away. Moreover, the severed leg continues to bend and unbend - “mow”.
Scorpions are well represented in the subtropics and deserts by small animals 4-6 cm long (Fig. 95, 3). Large scorpions up to 15 cm long live in the tropics. The body of a scorpion, like that of a spider, consists of a cephalothorax and abdomen. The abdomen has a fixed and wide anterior part and a narrow, long movable posterior part. At the end of the abdomen there is a swelling (the poisonous gland is located there) with a sharp hook. With it, the scorpion kills its prey and defends itself from enemies. For a person, the injection of a large scorpion with a poisonous sting is very painful, and can lead to death. The chelicerae and tentacles of scorpions are claw-shaped. However, chelicerae claws are small, while leg tentacle claws are very large and resemble those of crayfish and crabs. In total, there are about 750 species of scorpions.
Rice. 95. Various representatives of arachnids: 1 - tick; 2 - haymaker; 3 - scorpion; 4 - phalanx
Ticks. There are more than 20 thousand species of ticks. The length of their body usually does not exceed 1 mm, very rarely - up to 5 mm (Fig. 95, 1 and 96).
Unlike other arachnids, ticks do not have a body divided into cephalothorax and abdomen. Ticks that feed on solid food (microscopic fungi, algae, etc.) have gnawing jaws, while those that feed on liquid food form a piercing-sucking proboscis. Ticks live in the soil, among fallen leaves, on plants, in water, and even in human homes. They feed on decaying plant remains, small mushrooms, algae, invertebrates, suck plant juices, in living quarters of people, microscopic mites feed on dry organic residues contained in dust.
Rice. 96. Ixodid tick
The meaning of arachnids. Arachnids play a big role in nature. Known among them are both herbivores and predators that eat other animals. Arachnids, in turn, feed on many animals: predatory insects, birds, animals. Soil mites are involved in soil formation. Some ticks are carriers of serious diseases of animals and humans.
Arachnids are the first terrestrial arthropods that have mastered almost all habitat conditions. Their body consists of the cephalothorax and abdomen. They are well adapted to life in the ground-air environment: they have dense chitinous covers, they have pulmonary and tracheal breathing; save water, play an important role in biocenoses, have importance for a person.
Lesson learned exercises
- What are the signs of the external structure of arachnids that distinguish them from other representatives of arthropods
- Using the example of a spider-cross, tell about the methods of obtaining and digesting food. How are these processes related to the internal organization of the animal?
- Give a description of the structure and activity of the main organ systems, confirming the more complex organization of arachnids compared to annelids.
- What is the importance of arachnids (spiders, ticks, scorpions) in nature and human life?
