Animals with an exoskeleton

Lesson #5.

Subject: Evolution of the musculoskeletal system in animals.

Class: 7 B

Goals:

Study the features of the musculoskeletal system of mammals.

To study the complication of the musculoskeletal system during evolution.

Tasks:

educational:

Study the structure and functions of the musculoskeletal system of mammals.

Study the structure and functions of the musculoskeletal system during evolution.

To find out the features of complexity in representatives of the musculoskeletal system of different taxa.

developing:

Formation of the ability to establish cause-and-effect relationships.

Development of skills in working with books and tables.

educational:

To summarize the body of knowledge about the evolution of the musculoskeletal system.

Lesson type: explanation of new material.

Method: visually illustrative.

Form: group.

Should know after the lesson:

The structure and functions of the musculoskeletal system, from unicellular organisms to chordates.

Traits of increasing complexity of the structure of the musculoskeletal system in representatives of different taxa.

During the classes:

Organizational start:

Teacher: Hello guys, sit down! Please open your notebooks and write down the topic of our lesson: “Evolution of the musculoskeletal system.”

Learning new material:

Teacher: Over the course of a long evolutionary path, animals mastered new territories, types of food, and constantly adapted to the conditions environment. In order to survive, animals had to look for food, hide better or defend themselves from enemies, and move faster. Changing along with the body, the musculoskeletal system had to ensure all these evolutionary changes.

Which animals do you think are the most noticeable?

Student: The most primitive are the rhizomes, which do not have support system, move slowly, flowing with the help of pseudopods, while constantly changing shape.

Teacher: For the first time, the speed of movement changes in flagellates and ciliates. Guys, you must remember which animals formed exoskeleton?

Student: The exoskeleton was formed in crustaceans, arachnids and insects. It is represented by a chitinous cuticle, a chitinous shell that is impregnated with lime. Muscles are attached to this cover, which allows these animals to move quite quickly. Currently, arthropods are the most common type of animal.

Teacher: What disadvantages does such a skeleton have?

Student: It should be noted that the exoskeleton also has its drawbacks: it does not grow with the animal, and during growth the animal must molt several times, while the animal becomes completely defenseless and becomes easy prey for enemies.

Teacher: Guys, let's write down the information that we talked about in the table:

Teacher: Guys, along with the external skeleton there is an internal skeleton. Please tell me what advantages does the internal skeleton have?

Student: The internal skeleton is devoid of such disadvantages - it grows with the animal and allows for further specialization of individual muscles and their groups, while achieving record speeds of body movement. All chordates have an internal skeleton.

Teacher: The skeleton of most vertebrates is formed by bones, cartilage, and tendons. The bones of the skeleton can be connected either motionlessly - by fusion, or movably - with the help of a joint. Muscles are attached to bones in such a way that the bones are set in motion. The skeleton has the following parts:

Axial skeleton;

Skeleton of limbs;

Skeleton of the skull.

Fish, amphibians, reptiles, birds and mammals have a well-developed spine, which consists of vertebrae. Each vertebra consists of a body, upper and lower arches. The ends grow together and form a canal in which the spinal cord is located. The notochord is maintained throughout life in beluga and sturgeon.

Guys, what parts does the spine of a fish consist of?

Student: The spine of fish consists of the trunk and caudal sections.

The spine is formed by biconcave vertebrae, between which remains of the chord are preserved. The vertebrae of the trunk have an upper arch and a superior process, and the ribs are attached to them below. In the caudal region, the vertebrae have an upper, lower arch and spinous processes.

The skull consists of the brain and facial sections. The facial section is represented by the jaws, hyoid arch and gill apparatus.

The skeleton of the fins is represented by bony rays, the girdle of the forelimbs is connected to the skull. In addition to paired fins - pectoral and ventral, there are unpaired fins - dorsal and anal.

Teacher: Guys, let's write down what we just said.

Systematic group	Dept. Skeleton	Skeletal departments	Bones forming the skeleton
Superclass: Pisces		Medullary department	Consists of many bones fused together immovably.
		facial section	Represented by jaws, hyoid arch and gill apparatus.
	Spine	Trunk section Tail section
	Skeleton free finite	Unpaired fins (dorsal, caudal, anal)	Presented radius bones. There are supporting bones inside the body.
		Paired fins (pectoral and ventral)	Represented by bone rays.
	Limb belts	Forelimb belt	The girdle of the forelimbs is connected to the skull. The pectoral and pelvic fins are attached to both belts by means of small bones.
		Hind limb belt

What do you think are the main skeletal features of amphibians?

Student: In amphibians, due to the aquatic-terrestrial way of life, the axial skeleton has become more complex and is represented by a cervical region, consisting of one vertebra, and a trunk - of seven vertebrae with ribs that end freely. The sacrum consists of one vertebra, the pelvic bones are attached to it. Tailed amphibians have several vertebrae in the caudal region. The skull movably articulates with the cervical vertebra.

The muscles lose their metameric structure and are represented by many individual muscles.

The frog skeleton, like that of all vertebrates, is divided into four sections: the axial skeleton, the skeleton of the skull, the skeleton of the limbs and the skeleton of the limb girdles.

The axial skeleton is represented by the spine, which in addition to trunk And tail divisions characteristic of fish appeared cervical And sacral departments.

The frog's skull movably articulates with a single cervical vertebra, which ensures movement of the head in the vertical plane (the head cannot move in the horizontal plane).

The number of vertebrae of the trunk region of a frog is seven. The frog has no ribs, but in tailed amphibians, short upper ribs develop on the vertebrae of the trunk, and in legless amphibians, real ribs develop.

The sacral section includes one vertebra bearing long transverse processes to which the iliac bones of the pelvis are attached.

The tail section of a frog ends in the tail bone - urostyle- a bone, which is several vertebrae fused during embryonic development.

The forelimbs are four-fingered (the first finger is reduced) and consist of three sections: shoulder- brachial bone, forearm- fused radius and ulna bones and brush, represented by bones wrists, metacarpus and phalanges.

The hind limbs consist of three sections: hips, shins And feet. The thigh consists of the femur, the lower leg is made of fused tibia and fibula bones, the foot is made of bones tarsus, metatarsus and phalanges.

Shoulder girdle the frog encircles the body in a wide semi-ring and is fixed in the muscles. It is represented by several paired bones: scapulae ending in wide suprascapular cartilages, crow bones and clavicles, as well as one unpaired bone - the sternum.

Pelvic girdle consists of three paired bones fused due to heavy loads: ilium, pubis and ischium. With the help of the iliac bones, the pelvic girdle is attached to the transverse processes of the sacral vertebra.

Teacher: Guys, please fill out your sign with your help.

Systematic group	Dept. Skeleton	Skeletal departments	Bones forming the skeleton
Class: Amphibians		Brain department Facial department	The number of bones is less because there are no gill covers.
	Spine	Cervical region (1 section) Trunk section (7 parts) Sacral section (1 section) Tail section	Formed by vertebrae of different structures. (False) ribs are attached to the trunk vertebrae.
	Skeleton free finite	Forelegs
		Hind limbs
	Limb belts	Forelimb belt
		Hind limb belt

Now, let's figure out what features the musculoskeletal system of reptiles has. I'm listening to your answers.

Students: The spine of reptiles has five sections: cervical; chest; lumbar; sacral; tail.

In the cervical region the vertebrae are connected movably. They provide head mobility - necessary condition existence on earth. The thoracic and lumbar vertebrae bear ribs. In some, the ribs connect to the sternum, forming the rib cage, providing protection to the organs and better air flow to the lungs. The sacral section consists of two vertebrae. The tail section is well developed. In snakes, all parts of the spine have ribs, except the caudal one. It should be noted that the ribs end freely, which allows them to swallow large food.

Teacher: Using the textbook, please write down the listed features on a table.

Systematic group	Dept. Skeleton	Skeletal departments	Bones forming the skeleton
Class: Reptiles		There are no differences	There are no differences
	Spine	Cervical region (more than 1 digit) Thoracic region Lumbar region Sacral region (2 parts) Tail section	Formed by vertebrae of different structures. The ribs are attached to the trunk vertebrae.
	Skeleton free finite	Forelegs	Shoulder (humeral bone), forearm (radius and ulna), hand (wrist, metacarpus and 4th phalanges).
		Hind limbs (No differences from amphibians)	Thigh (femur), lower leg (tibia and fibula), foot (tarsus, metatarsus and 5 phalanges)
	Limb belts	Forelimb belt (No differences from amphibians)	The shoulder blades to which the bones of the forelimbs are attached.
		Hind limb belt (No differences from amphibians)	Consists of 3 paired fused bones (iliac, pubic and ischial)

Let's figure it out, what is the complication of the musculoskeletal system in birds?

Students: The spine of birds has five sections, like those of reptiles. The cervical region has from 9 to 25 vertebrae, movably connected. The fused thoracic vertebrae and ribs connected to the sternum form the rib cage. The sternum of many birds has a special protrusion - the keel. Muscles that actively work during flight are attached to the keel. The terminal thoracic, lumbar, sacral and first caudal vertebrae are fused, creating a powerful sacrum that serves to support the hind limbs, which increases the strength of the skeleton - adaptability to flight. Bird bones are light, many of them are hollow inside.

Despite some differences, the skeleton performs similar functions:

body support;

protection internal organs;

movement of a body in space.

But at the same time, the skeleton is light and strong due to the thinness of the bones and their pneumatic properties.

Brain department The skull is large, articulates with the spine with one condyle, as in reptiles.

IN facial area huge eye sockets and elongated jaws modified into a beak.

The skeleton of the body consists of spine And chest. The spine includes five sections: cervical, thoracic, lumbar, sacral and caudal. The cervical vertebrae are characterized by saddle-shaped joints, which provides greater mobility of the neck (in owls, the angle of rotation of the head reaches 270 degrees).

The posterior thoracic, lumbar, 2 sacral and anterior caudal are fused into a complex sacrum.

The middle caudals remained free, the latter fused to form the coccygeal bone.

The rib cage is formed by ribs, consisting of two bones connected by a joint at an angle to each other. Thanks to this structure of the ribs, the sternum can move closer and further in relation to the spine during breathing movements.

On the top of the ribs there are flat projections that overlap the rear ribs, which increases the strength of the chest.

Most birds have a keel on the sternum, to which the pectoral muscles are attached, driving the wings.

The forelimbs consist of the humerus, the forearm is represented by the ulna and radius, the hand consists of fused bones of the wrist and metacarpus, forming a common bone - buckle, and three fingers: second, third and fourth.

Bird pelvis open, the ischial and pubic bones do not fuse, this is due to the laying of large eggs.

Due to the fact that the main load when walking falls on hind limbs, the pelvic bones are massive, firmly fused with the posterior thoracic, lumbar, sacral vertebrae, as well as with part of the caudal vertebrae, forming a complex sacrum.

Teacher: Well done guys, let's fill in the remaining columns of the table using your textbook.

Systematic group	Dept. Skeleton	Skeletal departments	Bones forming the skeleton
Class: Birds		Facial department Brain department	Formed by bones fused together. There are huge eye sockets and a horny beak without teeth.
	Spine	Cervical region (from 9 to 25 vertebrae) Thoracic region Lumbar Sacral region Tail section	Formed by vertebrae of different structures. The ribs are attached to the trunk vertebrae, which are fused with the sternum, and it forms a keel to which the muscles are attached. In birds, the posterior pectoral, lumbar, 2 sacral and anterior caudal are fused into a complex sacrum.
	Skeleton free finite	Forelegs
		Hind limbs	The femur (femur), tibia (tibia), the tarsus (fused bones of the tarsus and metatarsus) and the 1st to 4th phalanges of the fingers appear.
	Limb belts	Forelimb belt	The shoulder blades and collarbones have fused and formed a fork.
		Hind limb belt	The pelvic bones are fused and attached to the lumbosacral spine.

Teacher: Now guys, let's look at the skeleton of mammals and describe it in the same way:

Systematic group	Dept. Skeleton	Skeletal departments	Bones forming the skeleton
Class: Birds		Facial department Brain department	There is a movable mandibular bone. Formed by bones fused together.
	Spine	Cervical region (7 parts) Thoracic region (From 9 to 24 digits) Lumbar (from 2 to 9 digits) Sacral section (3–4 parts) Tail section	Formed by vertebrae of different structures. Ribs are attached to the trunk vertebrae, which are fused with the sternum; below there are false ribs. The sacral vertebrae fuse together to form the sacrum.
	Skeleton free finite	Forelegs (Like reptiles)	The shoulder (humeral bone), forearm (radius and ulna bones), hand are modified. The bones are reduced and only 1 phalanx remains.
		Hind limbs

Question 1.
Skeleton performs the following functions:
1) supporting - for all other systems and organs;
2) motor - ensures the movement of the body and its parts in space;
3) protective - protects the thoracic and abdominal cavity, brain, nerves, blood vessels.

Question 2.
Distinguish two types of skeleton– external and internal. Some protozoa, many mollusks, arthropods have an exoskeleton - these are the shells of snails, mussels, oysters, the hard shells of crayfish, crabs, and the light but durable chitinous coverings of insects. Invertebrate radiolarians have an internal skeleton, cephalopods and vertebrates.

Question 3.
The body of mollusks is usually enclosed in a shell. The sink may consist of two doors or be of another shape in the form of a cap, curl, spiral, etc. The shell is formed by two layers - the outer, organic, and the inner, made of calcium carbonate. The calcareous layer is divided into two layers: behind the organic layer lies a porcelain-like layer formed by prismatic crystals of calcium carbonate, and below it is a mother-of-pearl layer, the crystals of which have the shape of thin plates on which light interference occurs.
The shell is an external hard skeleton.

Question 4.
The body and limbs of insects have a chitinized cover - the cuticle, which is the exoskeleton. The cuticle of many insects is equipped big amount hairs that perform the function of touch.

Question 5.
Protozoa can form external skeletons in the form of shells or shells (foraminifera, radiolarians, armored flagellates), as well as internal skeletons of various shapes. The main function of the protozoan skeleton is protective.

Question 6.
The presence of hard covers in arthropods prevents the continuous growth of animals. Therefore, the growth and development of arthropods is accompanied by periodic molting. The old cuticle is shed, and until the new one hardens, the animal grows.

Question 7.
Vertebrates have an internal skeleton, the main axial element of which is the notochord. In vertebrates, the internal skeleton consists of three sections - the skeleton of the head, the skeleton of the trunk and the skeleton of the limbs. Vertebrates (amphibian fish, reptiles, birds, mammals) have an internal skeleton.

Question 8.
Plants then they also have supporting structures with the help of which they carry the leaves towards the sun and support them in such a position that the leaf blades are illuminated as best as possible sunlight. U woody plants serves as the main support mechanical fabric. There are three types of mechanical fabrics:
1) collenchyma is formed from living cells of various shapes. They are found in young plant stems and leaves;
2) the fibers are represented by dead elongated cells with uniformly thickened membranes. Fibers are part of wood and bast. An example of non-lignified bast fibers is flax;
3) stony cells have irregular shape and highly thickened lignified shells. These cells form nut shells, stones of drupes, etc. Stony cells are found in the pulp of pear and quince fruits.
In combination with other tissues, mechanical tissue forms a kind of “skeleton” of the plant, especially developed in the stem. Here it often forms a kind of cylinder running inside the stem, or is located along it in separate strands, providing bending strength to the stem. In the root, on the contrary, the mechanical tissue is concentrated in the center, increasing the root's tensile strength. Wood also plays a mechanical role; even after dying, wood cells continue to perform a supporting function.

Question 1. What underlies the evolutionary changes in the musculoskeletal system?

The basis of evolutionary changes in the musculoskeletal system lies, first of all, in the transition of animals from aquatic environment habitats in the ground and air. The new environment required greater strength from the musculoskeletal system and the ability to carry out more complex and varied movements. An example is the appearance of compound paired limbs with movable (articular) joints of parts and complex muscles in representatives of the class of amphibians - the first land vertebrates.

Question 2. Which animals have an exoskeleton?

All representatives of the phylum Arthropods have an exoskeleton: insects have a chitinous shell, arachnids and crustaceans have integuments impregnated with lime.

Question 3. Which vertebrates do not have a bony skeleton?

Representatives of the classes of cyclostomes and cartilaginous fish do not have a bony skeleton.

Question 4. What does the similar structure of the skeletons of different vertebrates indicate?

The general plan of the structure of the skeletons of different vertebrates indicates a common origin and evolutionary relationship. And the presence of similar private formations means that animals lead a similar lifestyle in similar environmental conditions. For example, both flying birds and bats have a bony ridge (keel) on the sternum.

Question 5. What conclusion can be drawn after getting acquainted with general functions musculoskeletal system in animal organisms?

Despite significant differences in the structure of musculoskeletal structures in different animals, their skeletons perform similar functions: supporting the body, protecting internal organs, moving the body in space.

37. Musculoskeletal system

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What are the functions of the musculoskeletal system?

The musculoskeletal system performs the functions of support, maintaining a certain shape, protecting organs from damage, and movement.

Why does the body need musculoskeletal system?

The musculoskeletal system is necessary for the body to maintain vital functions. It is responsible for maintaining shape and protecting the body. The most important role of the musculoskeletal system is movement. Movement helps the body in choosing habitats, searching for food and shelter. All functions of this system are vital for living organisms.

Questions

1. What underlies the evolutionary changes in the musculoskeletal system?

Changes in the musculoskeletal system had to fully ensure all evolutionary changes in the body. Evolution has changed the appearance of animals. In order to survive, it was necessary to search for food more actively, to hide or defend better from enemies, and to move faster.

2. Which animals have an exoskeleton?

The exoskeleton is characteristic of arthropods.

3. Which vertebrates do not have a bony skeleton?

Lancelets and cartilaginous fish do not have a bony skeleton.

4. What does the similar structure of the skeletons of different vertebrates indicate?

The similar structure of the skeletons of different vertebrates indicates the unity of origin of living organisms and confirms the evolutionary theory.

5. What conclusion can be drawn after becoming familiar with the general functions of the musculoskeletal system in all animal organisms?

The musculoskeletal system in all animal organisms performs three main functions - supporting, protective, and motor.

6. What changes in the structure of protozoa led to an increase in the speed of their movement?

The first supporting structure of animals - the cell membrane - allowed the body to increase the speed of movement due to flagella and cilia (outgrowths on the membrane)

Tasks

Prove that the complication of the amphibian skeleton is associated with changes in the habitat.

The skeleton of amphibians, like other vertebrates, consists of the following sections: the skeleton of the head, torso, limb girdles and free limbs. Amphibians have significantly fewer bones than fish: many bones are fused, and in some places cartilage is preserved. The skeleton is lighter than that of fish, which is important for terrestrial existence. The wide flat skull and upper jaws are a single formation. The lower jaw is very mobile. The skull is movably articulated to the spine, which plays important role during terrestrial food production. The spine of amphibians has more sections than that of fish. It consists of the cervical (one vertebra), trunk (seven vertebrae), sacral (one vertebra) and caudal sections. The tail of a frog consists of a single tail bone, while that of tailed amphibians consists of separate vertebrae. The skeleton of the free limbs of amphibians, unlike fish, is complex. The skeleton of the forelimb consists of the shoulder, forearm, wrist, metacarpus and phalanges of the fingers; hind limb - thigh, tibia, tarsus, metatarsus and phalanges. The complex structure of the limbs allows amphibians to move in both aquatic and terrestrial environments.

The purpose of the lesson:
Study the structure of the musculoskeletal system of various representatives of the animal kingdom.
Tasks:

consider the type of skeletons: internal and external types;

determine differences in structure and functions;

During the classes:
Over the course of a long evolutionary path, animals mastered new territories, types of food, and constantly adapted to environmental conditions. In order to survive, animals had to look for food, hide better or defend themselves from enemies, and move faster. Changing along with the body, the musculoskeletal system had to ensure all these evolutionary changes.
The most primitive rhizomes, which do not have a support system, move slowly, flowing with the help of pseudopods, while constantly changing shape.
For the first time, the speed of movement changes in flagellates and ciliates.
Exoskeleton formed in crustaceans, arachnids and insects. It is represented by a chitinous cuticle, a chitinous shell that is impregnated with lime. Muscles are attached to this cover, which allows these animals to move quite quickly. Currently, arthropods are the most common type of animal. It should be noted that the exoskeleton also has its drawbacks: it does not grow with the animal, and during growth the animal must molt several times, while the animal becomes completely defenseless and becomes easy prey for enemies.
Internal skeleton free from such disadvantages it grows with the animal and allows for even more specialization of individual muscles and their groups, while achieving record speeds of body movement. All chordates have an internal skeleton.
The skeleton of most vertebrates is formed by bones, cartilage, and tendons. The bones of the skeleton can be connected either motionlessly by fusion, or movably by means of joint. Muscles are attached to bones in such a way that the bones are set in motion. The skeleton has the following parts:

Axial skeleton;

Skeleton of limbs;

Skeleton of the skull.
In fish, amphibians, reptiles, birds and mammals, it is well developed spine, which consists of vertebrae. Each vertebra consists of a body, upper and lower arches. The ends grow together and form a canal in which the spinal cord is located. The notochord is maintained throughout life in beluga and sturgeon.
The spine of fish consists of the trunk and caudal sections.
In amphibians, due to the aquatic-terrestrial way of life, the axial skeleton has become more complex and is represented by a cervical region, consisting of one vertebra, and a trunk - of seven vertebrae with ribs that end freely. The sacrum consists of one vertebra, the pelvic bones are attached to it. Tailed amphibians have several vertebrae in the caudal region.
The spine of reptiles has five sections:

cervical;

chest;

lumbar;

sacral;

tail.
In the cervical region the vertebrae are connected movably. They provide head mobility a necessary condition for existence on earth. The thoracic and lumbar vertebrae bear ribs. Some people have ribs that connect to sternum, forming chest, provides protection to organs and better air supply to the lungs. The sacral section consists of two vertebrae. The tail section is well developed. In snakes, all parts of the spine have ribs, except the caudal one. It should be noted that the ribs end freely, which allows them to swallow large food.
Spine birds has five sections, like those of reptiles. The cervical region has from 9 to 25 vertebrae, movably connected. The fused thoracic vertebrae and ribs connected to the sternum form the rib cage. The sternum of many birds has a special protrusion keel. Muscles that actively work during flight are attached to the keel. The terminal thoracic, lumbar, sacral and first caudal vertebrae are fused, creating a powerful sacrum that serves to support the hind limbs, which increases the strength of the skeleton and adaptability to flight. Bird bones are light, many of them are hollow inside.
The mammalian spine also consists of five sections. The skeletons of paired limbs of vertebrates have a similar structure. The forelimbs consist of shoulder, forearm, hand. The hind limbs consist of thighs, legs, feet. The humerus of the forelimb is attached to the thorax with the help of forelimb belts, in some animals it consists of a collarbone and scapulae (primates), in others only scapulae, since there are no clavicles (dogs and equids). Using a belt of the hind limbs, consisting of pelvic bones fused with the sacral spine, the hind limbs are attached to the spine. The skull consists of the brain and facial sections. The brain is located in the medulla.
Despite some differences, the skeleton performs similar functions:

body support;

protection of internal organs;

movement of a body in space.