The chordate type includes a huge number of animals, they include both primitive and very developed species, from which man originated.
Nervous system
Chordates differ from other types in having a central nervous system located above the notochord. Initially, it was simple, but in the process of evolution it has developed to an extreme degree of complexity.
Habitat and distribution
Chordates are divided into three subtypes, and only vertebrates have managed to adapt to life both in water and on land; tunicates, or urochords, and non-cranial live only in sea water.
general characteristics
Chordates are distinguished by bilateral symmetry: they have a special internal organ - an axial skeleton, the so-called chord, or dorsal string. The notochord is present in some animals in the embryonic or larval stage.
All chordates have a dorsal chord - a strong and at the same time elastic structure that supports their body and muscles. The oral apparatus of chordates is not adapted to chewing and swallowing large prey. Content with the smallest living organisms, chordates have special organs for capturing and filtering them, the main of which is the gill pharynx. The water drawn in by the mouth passes through the gill slits, and the nutrient microorganisms contained in it are retained. The gill pharynx, which also serves for respiration, undergoes fundamental changes in adults.
The circulatory system consists of a pulsating organ, the heart and blood vessels through which blood circulates. This structure is constantly becoming more complex and is becoming more and more connected with the respiratory system. With the exception of the urochordates, which are hermaphrodites, all other chordates are heterosexual.
The chordate type is divided into three subtypes: urochordates, or tunicates, non-cranial, and vertebrates.
Urochordates, or tunicates, include many different marine animals ranging in length from a few millimeters to 10 cm. Some are sessile, like sea squirts, while others lead a free lifestyle. Outwardly, the body of the urochords resembles a bag. The dorsal chord is present only in the caudal part, and in some species only in the larval stage. The circulatory and nervous systems are reduced.
The structure of non-cranial has many similarities with vertebrates. The body, laterally compressed, is covered with epidermis. The dorsal chord runs through the entire body and is also present in adults. The non-cranial do not have limbs, but they do have fins with which they swim, and various metameric organs along the entire body. In front of the abdominal cavity is a mouth without jaws, but with numerous fibers that retain food that is filtered from the water. The closed circulatory system consists of only vessels: non-skullans do not have a heart.
Fertilization in these heterosexual animals occurs in water.
Vertebrates are the most highly organized representatives of the chordate type. The dorsal notochord is present only in embryos; in adults, it is replaced by an axial spine, consisting of a series of cartilaginous or bony vertebrae. From this solid base, two pairs of limbs extend, serving for movement. The skin is formed by the dermis and epidermis, which perform a protective function.
The nervous system consists of the brain protected by the cranium, the spinal cord and the peripheral nervous system. The blood, pushed by the pulsating movements of the heart, circulates through a dense network of vessels, arteries and capillaries. The respiratory apparatus consists of gills in aquatic vertebrates and lungs in terrestrial ones. A rather complex digestive system is formed in different animals by different organs.
Vertebrates are heterosexual and can be oviparous (females lay eggs), ovoviviparous (eggs develop in the body of the female) and viviparous (the embryo develops in the uterus, receiving food directly from it).
Kinds
Ascidia belongs to the subphylum Urochordaceae. A very primitive bag-shaped animal, “dressed” in a dense “dead end” - living tissue with two openings: a mouth siphon adapted for water absorption, respiration and retention of nutrient particles, and a cloacal siphon for waste ejection.
One of the most primitive vertebrates. She has a yoke-like body without jaws and limbs. The mouth is a funnel studded with numerous molars, which are arranged in concentric circles, in the center of these circles is the tongue. Lamprey tenaciously, like a sucker, attaches its mouth to its prey and sucks blood from it.
Lancelet from the non-cranial subtype - a small, almost transparent marine animal that lives at the bottom of the sea and represents a transitional species between invertebrates and vertebrates. The dorsal nerve cord and tail muscles of the lancelet are similar to the chord and muscles of fish, but, on the other hand, it has neither sensory organs, nor jaws, nor a skeleton.
| Type of | Subtype | Class | Detachment | Family | Genus | View |
| chordates | urochordaceae (tunicates) | sea squirt | ||||
| non-cranial | lancelet | |||||
| vertebrates | cyclostomes | lamprey | ||||
| fish | ||||||
| amphibians | ||||||
| reptiles | ||||||
| birds | ||||||
| mammals |
Chordates ( Chordata listen)) is a phylum of animals that includes vertebrates, larval-chordates, and non-cranial. Vertebrates such as birds and fish are the best known, and are the subtype of animals to which humans belong.
Chordates are bilaterally symmetrical, which indicates the existence of a line of symmetry that divides their body into two halves that are almost mirror images of each other.
Bilateral symmetry is found not only in chordates, but also in and (although in the case of echinoderms they are bilaterally symmetrical only during the larval stage of their life cycle, and pentaradial symmetry is shown in adults).
All chordates have a notochord that is present during some or all of their life cycle. The chord (or dorsal string) is a semi-flexible rod to which the large muscles of the animal are attached. It also plays an important role in signaling and coordinating development.
The chord consists of flat, enclosed in a fibrous sheath. In vertebrates, the dorsal string is present only during the embryonic stage of development, and then the vertebrae develop around it and the spine forms. In tunicates, the notochord remains throughout the entire life cycle of the animal.
Chordates have a single hollow dorsal nerve cord that runs down the back of the animal and, in most species, forms the brain at the front of the body. They also have gill slits that serve as openings between the pharyngeal cavity and the external environment, as well as for filtering water.
Another characteristic of chordates is a structure called the endostyle, a groove-like organ that sits against the wall of the pharynx and secretes mucus and also catches small food particles that enter the pharyngeal cavity. Endostyle is present in tunicates and lancelets. In vertebrates, the endostyle is replaced by the thyroid gland, an endocrine gland located in the neck.
Main characteristics
- chord;
- neural tube (strand);
- gill slits;
- endostyle or thyroid gland;
- muscular tail.
Species diversity
More than 75,000 animal species belong to the chordate phylum.
Classification
Chordates are classified in the following taxonomic hierarchy:
- Domain: eukaryotes ( Eukaryota);
- Kingdom: Animals ( Animalia);
- Type of: Chordates ( Chordata).
Chordates, in turn, are divided into the following subtypes:
- Skullless ( Acrania) : now there are about 32 species of non-cranial. Representatives of this subtype have chords that persist throughout their life cycle. Lancelets are the only non-cranial family whose members are marine animals with long, narrow bodies. Earliest known fossil lancelet, Yunnanozoon, lived about 530 million years ago at the time. Fossils of these organisms have also been found in the famous Burgess Shale in British Columbia.
- Larval chordates, or tunicates ( Urochordata) : currently there are about 1600 species of tunicates. This subtype is subdivided into classes such as ascidians and appendiculars. Tunicates are marine filter feeders, most of which do not move, but attach themselves to rocks or other hard surfaces on the seabed.
- (Vertebrata) - Today there are about 57,000 species of vertebrates. Members of this group include lampreys, mammals, birds, amphibians, reptiles, and fish. During development, the notochord of vertebrates is replaced by the vertebral column.
The Chordata phylum is one of the largest in terms of the number of species in the animal kingdom. In total, it contains about 42 thousand modern species. Chordates appeared at the beginning of the Paleozoic, more than 500 million years ago. It is believed that they originated from some ancient annelids. Representatives of this type have common features and a single structure plan.
The internal axial skeleton is the chord - an elastic, dense and elastic cord. With the development of the embryo, the notochord is formed from the endoderm layer, separating from the dorsal part of the embryonic gut. In lower chordates, it performs the role of the internal axial skeleton for life, in higher animals it functions as an axial skeleton only in embryonic development, and in adult animals it is replaced by the spine.
The central nervous system, where the nerve centers (clusters of neuron bodies) are located, in chordates is represented by the neural tube, which, during the development of the embryo, is formed from the ectoderm layer. The neural tube is located above the chord. In lower chordates, it is not divided into sections, while in higher ones it is divided into the spinal cord and brain.
The anterior part of the digestive tube is the pharynx. It has gill openings and functions as a common division of the digestive and respiratory systems. In lower chordates, gills develop on the interbranchial septa, which function throughout life. In higher chordates, gill rudiments appear at certain stages of embryonic development, and lungs develop in adult animals.
In addition to these main features, chordates have other characteristic features. Chordates are deuterostome, secondary cavity, bilaterally symmetrical animals. The secondary mouth occurs in them at the early stages of embryonic development, when an anus is formed in the place of the primary mouth, and a mouth is formed at the opposite end of the body (from invertebrates to deuterostomes include echinoderms). In chordates, striated muscles develop, and the head section with sensory organs separates. The circulatory system is closed; higher chordates develop a muscular pumping organ - the heart.
Such a structure of chordates turned out to be evolutionarily progressive. This allowed them to master all habitats, spread throughout the globe. Chordates are very diverse (Fig. 111) and are represented by various ecological groups, an abundance of species, many of which reach a high abundance.
The chordate type is divided into three subtypes. Two of them - Cranial and Cranial, or Vertebrates, are considered in this course of zoology. The non-cranial subtype includes one class - Lancelets, the cranial or vertebrate subtype includes: Fish, Amphibians, Reptiles, Birds and Mammals.
Subtype Cranial (Acrania)
Skullless- marine, mainly bottom animals, retaining characteristics of the chordate type for life. These are the most primitive chordates, so their study is important for understanding the origin of chordates and the initial stages of their evolution.
The lancelet is a primitive chordate
Class Representatives lancelets live in shallow waters, in the coastal part of warm seas and oceans. In our country lancelets found in the shallows of the Black and Japan Seas. Only about 30 modern species are known.
In terms of external structure, the lancelet resembles a small translucent fish 4-8 cm long. It stretches along the body from the upper side dorsal. He goes into tail , which is similar in shape to a medical instrument lancet. For this similarity, the lancelet got its name. It was first described by the Russian academician P.S. Pallas in 1774. The lancelet does not have paired fins. The skin is very thin, through them translucent internal organs.
The lancelet retains all the signs of chordates for life.
Its internal axial skeleton is represented by a chord stretching along the body. The notochord and the neural tube lying above it are surrounded by a connective tissue sheath. The central nervous system is the neural tube. Numerous sensory and motor nerves depart from it, forming the peripheral nervous system. In the skin there are tactile cells, in the neural tube, among other nerve cells, light-sensitive eyes.
Under the notochord is the digestive tube. Its anterior part - the pharynx - has gill openings. Therefore, the pharyngeal intestine performs the functions of both the digestive and respiratory systems. Gill arteries (thin blood vessels, capillaries) pass through the interbranchial septa, through which oxygen enters the blood, and carbon dioxide is released into the water. Gas exchange occurs due to the difference in pressure between gases.
At the bottom of the pharynx is a groove lined with ciliated cells. The movements of the cilia create a stream of water that washes over the gills. Small food particles that have fallen into the pharynx stick together and are sent by a stream of water into the digestive tube. Under the influence of digestive juices, food is digested, and undigested residues are removed through the anus.
The circulatory system is closed. Through a large abdominal vessel, blood moves forward to the gills, where it is oxidized (enriched with oxygen). Through the dorsal vessel (spinal aorta), this arterial blood is carried to all organs of the body. The lancelet has no heart. Blood moves by contraction of the so-called "gill hearts" - the walls of the abdominal vessel at the base of the gill arteries.
The excretory organs of the lancelet are similar to the excretory organs of annelids and are excretory tubes that open into the body cavity at one end, and flow into the common canal at the other. Several common excretory canals open outwards.
Most of the time lancelets spend burrowing into the sand and exposing the front end of the body with a preoral funnel surrounded by tentacles. The lancelet feeds on protozoa and unicellular algae. The anterior end of its body is surrounded by a fold of skin that forms the peribranchial cavity. This protects the gill slits from solid particles entering them.
Lancelets, like most other chordates, are dioecious animals. In females, eggs are produced in the ovaries; in males, spermatozoa are produced in the testes. Fertilization is external: the penetration of spermatozoa into the eggs occurs in water. Lancelets breed in the warm season, from spring to autumn.
The lancelet is one of the most primitive representatives of the chordates and retains all of their main features throughout their lives. The notochord serves as its axial skeleton, the neural tube serves as the central nervous system, the pharynx has gill openings, and there is no heart in the circulatory system. The lancelet is a dioecious animal that is characterized by external fertilization.
Subtype Cranial, or Vertebrate (Vertebrata)
General features of the subtype
The subtype Cranial, or Vertebrates, includes most of the chordates: the classes Cartilaginous and Bony Fish, Amphibians, Reptiles, Birds and Mammals.
Vertebrates are distinguished by a higher level of development than non-cranial ones. Their body is supported by the spine, which in adult animals replaces the notochord. The central nervous system is especially improved: the neural tube is divided into the brain and spinal cord. The sense organs are well developed. The skull develops to protect the brain. Paired limbs are formed: in fish - paired fins, in terrestrial vertebrates - five-fingered limbs. Unlike non-cranial vertebrates, a muscular heart appears in the circulatory system. The excretory organs are the kidneys. Vertebrates lead an active lifestyle, sometimes making distant migrations. They are distributed throughout the globe, have mastered all habitats. Many modern vertebrate species reach high numbers.
Type Chordates combines animals that are different in appearance, living conditions, lifestyle. Representatives of this type are found in all the main environments of life: in water, on land, in the thickness of the soil, in the air. They are distributed throughout the earth. The number of species of modern representatives of chordates is about 40 thousand.
The phylum Chordata includes non-cranial, cyclostomes, fish, reptiles, amphibians, mammals, and birds. Tunics can also be attributed to this type - this is a peculiar group of organisms that lives on the bottom of the ocean and leads an attached lifestyle. Sometimes included in the phylum Chordates are enteropneas, which have some of the characteristics of this type.
Characters of the chordate type
Despite the great diversity of organisms, they all have a number of common structural and developmental features.
The structure of chordates is as follows: all these animals have an axial skeleton, which first appears in the form of a chord or dorsal string. The notochord is a special non-segmented and elastic cord that embryonic develops from the dorsal wall of the embryonic intestine. The origin of the notochord is endothermal.
Further, this cord can develop in different ways, depending on the organism. For life it remains only in the lower chordates. In most higher animals, the notochord is reduced, and the vertebral column is formed in its place. That is, in higher organisms, the notochord is an embryonic organ that is displaced by the vertebrae.
Above the axial skeleton is the central nervous system, which is represented by a hollow tube. The cavity of this tube is called the neurocoel. Almost all chordates are characterized by a tubular structure of the central nervous system.
In most organisms of the chordate type, the anterior section of the tube grows to form the brain.
The pharyngeal section (anterior) of the digestive tube comes out with two opposite ends. The outgoing openings are called visceral fissures. Lower type organisms have gills on them.
In addition to the above three features of chordates, it can also be noted that these organisms have a secondary mouth, like echinoderms. The body cavity in animals of this type is secondary. Chordates also have bilateral body symmetry.
The phylum Chordates is divided into subtypes:
- Skullless;
- tunicates;
- Vertebrates.
Subtype Cranial
This subtype includes only one class - the Head Chordidae, and one order - the Lancelets.
The main difference of this subtype is that these are the most primitive organisms, and all of them are exclusively marine animals. They are distributed in the warm waters of the oceans and seas of temperate and subtropical latitudes. Lancelets and epigonichites live in shallow water, mainly burying themselves with the back of the body in the bottom substrate. They prefer sandy soil.
This type of organism feeds on detritus, diatoms or zooplankton. They always breed in the warm season. Fertilization is external.
The lancelet is a favorite object of study, since all the signs of chordate organisms are preserved in it for life, which makes it possible to understand the principles of the formation of chordates and vertebrates.
Subtype Shellers
The subtype includes 3 classes:
- salps;
- ascidians;
- Appendiculars.
All animals of the subtype are exclusively marine.
The main difference between these chordates is that in almost all organisms in the adult state there is no chord and neural tube. In the larval state, all type traits in tunicates are pronounced.
Tunicates live in colonies or singly, attached to the bottom. There are much fewer free-swimming species. This subtype of animals lives in the warm waters of the tropics or subtropics. They can live both on the surface of the sea and deep in the ocean.
The body shape of adult tunicates is rounded barrel-shaped. The organisms got their name due to the fact that their body is covered with a rough and thick shell - a tunic. The consistency of the tunic is cartilaginous or gelatinous, its main purpose is to protect the animal from predators.
Tunicates are hermaphrodites, they can reproduce both sexually and asexually.
It is known that the ancestors of these organisms were free-swimming, while at the present time only tunicate larvae can move freely in the water column.
Subtype Vertebrates
Skull animals are the highest subtype. Compared to other subtypes, they have a higher level of organization, which is evident from their structure, both external and internal. Among vertebrates, there are no species that lead a completely attached lifestyle - they actively move in space, looking for food and shelter, a mate for reproduction.
By moving, vertebrate organisms provide themselves with the opportunity to change their habitat depending on changing external conditions.
The above general biological features are directly related to the morphological and physiological organization of vertebrates.
The nervous system of the cranial is more differentiated than that of the lower animals of the same type. Vertebrates have a well-developed brain, which contributes to the functioning of higher nervous activity. It is the higher nervous activity that is the basis of adaptive behavior. These animals have well-developed sense organs, which are necessary for communication with the environment.
As a result of the emergence of the sense organs and the brain, such a protective organ as the skull has developed. And instead of a chord, this subtype of animals has a vertebral column, which performs the function of supporting the entire body and a case for the spinal cord.
All animals of the subtype develop a mobile jaw apparatus and oral fissure, which develop from the anterior intestinal tube.
The metabolism of this subtype is much more complicated than that of all the animals discussed above. Cranials have a heart that provides fast blood flow. The kidneys are essential for removing waste products from the body.
The subtype Vertebrates appeared only in the Ordovician-Silurian, but in the Jurassic, all currently known types and classes already existed.
The total number of modern species is slightly more than 40 thousand.
Vertebrate classification
Very diverse type of chordates. The classes that exist in our time are not so numerous, but the number of species is enormous.
The cranial subtype can be divided into two groups, these are:
- Primary organisms.
- Terrestrial organisms.
Primary aquatic organisms
Primary aquatic differ in that they either have gills throughout their life, or only in the larval stage, and during the development of the egg, embryonic membranes are not formed. This includes representatives of the following groups.
Section Jawless
- Class Cyclostomes.
These are the most primitive cranial animals. They actively developed in the Silurian and Devonian; at present, their species diversity is not high.
Section Jaws
Superclass Pisces:
- Class Bony fish.
- Class Cartilaginous fish.
Superclass Quadrupeds:
- Class Amphibians.
These are the first animals in which the jaw apparatus appears. This includes all known fish and amphibians. All of them actively move in water and on land, hunt and capture food with their mouths.
Terrestrial organisms
The group of terrestrial animals includes 3 classes:
- Birds.
- Reptiles.
- Mammals.
This group is characterized by the fact that embryonic membranes are formed in animals during the development of the egg. If the species lays its eggs on the ground, then the embryonic membranes protect the embryo from external influences.
All chordates of this group live mainly on land, have internal fertilization, which indicates that these organisms are more evolutionarily developed.
They lack gills at all stages of development.
Origin of chordates
There are several hypotheses for the origin of chordates. One of them suggests that this type of organisms originated from the larvae of the enteropretis. Most representatives of this class lead an attached lifestyle, but their larvae are mobile. Considering the structure of the larvae, one can see the beginnings of the notochord, the neural tube and other features of the chordates.
Another theory is that the Chordata phylum is descended from the crawling, worm-like ancestors of the intestinal-breathers. They had the beginnings of a chord, and in the pharynx, next to the gill slits, there was an endostyle - an organ that contributed to the secretion of mucus and catching food from the water column.
The article considered the general characteristics of the type. Chordates are united by many similar features of all organisms, but still each class and each species has individual characteristics.
The main terms and concepts tested in the examination paper: non-cranial, gill slits, internal skeleton, amphibians, skin, limbs and limb girdle, circulation, lancelet, mammals, neural tube, vertebrates, reptiles, birds, reflexes, adaptations to lifestyle, fish, bone skeleton, cartilaginous skeleton, notochord .
To type Chordates include animals that have an internal axial skeleton - a chord or a vertebral column. Chordate animals have reached in the process of evolution the highest, in comparison with other types, the level of organization and flourishing. They live in all areas of the globe and occupy all habitats.
chordates are bilaterally symmetrical animals with a secondary body cavity and a secondary mouth.
In chordates, there is a general plan for the structure and location of internal organs:
- the neural tube is located above the axial skeleton;
- under it is a chord;
- under the chord is the digestive tract;
- under the digestive tract - the heart.
In the phylum Chordates, two subtypes are distinguished - Cranial and Vertebrate. Refers to the non-skull lancelet. All other chordates known today, considered in the school biology course, belong to the subtype Vertebrates.
The subtype Vertebrates includes the following classes of animals: Fish, Amphibians, Reptiles, Birds, Mammals.
General characteristics of chordates.Skin vertebrates protect the body from mechanical damage and other environmental influences. The skin is involved in gas exchange and excretion of decay products.
Derivatives of the skin are hair, claws, nails, feathers, hooves, scales, horns, needles, etc. Sebaceous and sweat glands develop in the epidermis.
Skeleton, representatives of the chordate type can be connective tissue, cartilaginous and bone. The non-cranial have a connective tissue skeleton. In vertebrates - cartilaginous, bone-cartilaginous and bone.
musculature- divided into striated and smooth. The striated muscles are called skeletal. Smooth muscles form the muscular system of the jaw apparatus, intestines, stomach and other internal organs. The skeletal muscles are segmented, although less than in lower vertebrates. Smooth muscle has no segmentation.
Digestive system It is represented by the oral cavity, pharynx, always associated with the respiratory organs, esophagus, stomach, small and large intestines, digestive glands - the liver and pancreas, which develop from the wall of the anterior intestine. In the process of evolution of chordates, the length of the digestive tract increases, it becomes more differentiated into sections.
Respiratory system formed by gills (in fish, amphibian larvae) or lungs (in terrestrial vertebrates). The skin serves as an additional respiratory organ for many. The gill apparatus communicates with the pharynx. In fish and some other animals, it is formed by the gill arches, on which the gill filaments are located.
The lungs during embryonic development are formed from outgrowths of the intestine and are of endodermal origin.
The circulatory system is closed. The heart consists of two, three or four chambers. Blood enters the atria, and is sent to the bloodstream by the ventricles. There is one circulation circle (in fish and amphibian larvae) or two (in all other classes). The heart of fish, amphibian larvae is two-chambered. Adult amphibians and reptiles have a three-chambered heart. However, reptiles develop an incomplete interventricular septum. Fish, amphibians and reptiles are cold-blooded animals. Birds and mammals have a four-chambered heart. These are warm-blooded animals.
Blood vessels are divided into arteries, veins and capillaries.
Nervous system ectodermal origin. It is laid in the form of a hollow tube on the dorsal side of the embryo. The central nervous system is made up of the brain and spinal cord. The peripheral nervous system is formed by cranial and spinal nerves and interconnected ganglions that lie along the spinal column. Spinal cord is a long cord lying in the spinal canal. Spinal nerves branch off from the spinal cord.
sense organs well developed. Primitive aquatic animals have organs sideline, perceiving pressure, direction of movement, speed of water flow.
excretory organs all vertebrates are represented by kidneys. The structure and mechanism of functioning of the kidneys changes in the process of evolution.
Reproductive organs. Vertebrates are dioecious. The sex glands are paired and develop from the mesoderm. The genital ducts are connected with the excretory organs.
Superclass Pisces
Fish appeared in the Silurian - Devonian from jawless ancestors. There are about 20,000 species. Modern fish are divided into two classes - cartilaginous and Bone. Cartilaginous fish include sharks and rays, characterized by a cartilaginous skeleton, the presence of gill slits, and the absence of a swim bladder. Bony fish include animals that have bony scales, a bone skeleton, gill slits covered with a gill cover. The appearance of fish is due to the following aromorphoses :
- the appearance of a cartilaginous or bone spine and a skull that covers the spinal cord and brain from all sides;
- the appearance of the jaws;
- the appearance of paired limbs - ventral and pectoral fins.
All fish live in water, have a streamlined body, divided into a head, body and tail. The sense organs are well developed - sight, smell, hearing, taste, organs of the lateral line, balance. The skin is two-layered, thin, mucous, covered with scales. The muscles are almost undifferentiated, with the exception of the muscles of the jaws and the muscles attached to the gill covers of bony fish.
Digestive system well differentiated into departments. There is a liver with a gallbladder and a pancreas. Many have developed teeth.
Respiratory organs fish have gills, and lungfish have gills and lungs. An additional function of breathing is performed by the swim bladder in bony fish. It also performs a hydrostatic function.
Circulatory system closed. One circle of blood circulation. The heart consists of an atrium and a ventricle. Venous blood from the heart through the afferent branchial arteries enters the gills, where the blood is saturated with oxygen. Arterial blood flows through the efferent branchial arteries into the dorsal aorta, which supplies blood to the internal organs. Fish have a portal system of the liver and kidneys, which cleans the blood of harmful substances. Fish are cold-blooded animals.
excretory system represented by ribbon-like primary kidneys. Urine flows through the ureters to the bladder. In males, the ureter is also the vas deferens. Females have an independent excretory opening.
gonads represented by paired testes in males and ovaries in females. Many fish show sexual dimorphism. Males brighter than females attract them with their appearance, mating dances.
In the nervous system the development of the diencephalon and midbrain should be noted. Most fish have a well-developed cerebellum, which is responsible for coordinating movements and maintaining balance. The forebrain is less developed than in the higher classes of animals.
Eyes have a flat cornea, a spherical lens. Century no.
hearing organs represented by the inner ear - the membranous labyrinth. There are three semicircular canals. They contain lime stones. Fish make and pick up sounds.
sense organs represented by sensitive cells scattered throughout the body.
Lateral line perceives the direction of flow and water pressure, the presence of obstacles, sound vibrations.
taste cells are in the oral cavity.
The value of fish in nature and human life. Consumers of plant biomass, consumers of the second and third orders; food sources, fats, vitamins.
EXAMPLES OF TASKS
Part A
A1. The non-skull animals are
3) lancelet
4) octopus
A2. The main feature of chordates is
1) closed circulatory system
2) internal axial skeleton
3) gill breathing
4) striated muscles
A3. The bone skeleton is
1) white shark 3) stingray
2) katrana 4) piranhas
A4. Warm-blooded animals include
1) whale 2) sturgeon 3) crocodile 4) toad
A5. There are bony gill covers
1) dolphin 3) tuna
2) sperm whale 4) electric stingray
A6. Have a four-chambered heart
1) turtles 2) pigeons 3) perches 4) toads
1) single chamber heart and two circles of blood circulation
2) two-chambered heart and one circle of blood circulation
3) three-chambered heart and one circle of blood circulation
4) two-chambered heart and two circles of blood circulation
A8. Cold-blooded animals are
1) beaver 3) squid
2) sperm whale 4) otter
A9. The coordination of fish movements is regulated
1) forebrain 3) spinal cord
2) midbrain 4) cerebellum
A10. No swim bladder
1) katrans 2) pike 3) perch 4) sturgeon
Part B
IN 1. Choose the right statements
1) fish have a three-chambered heart
2) the transition of the head to the trunk in fish is clearly visible
3) there are nerve endings in the organs of the lateral line of fish
4) the chord in some fish lasts a lifetime
5) fish are not capable of forming conditioned reflexes
6) the nervous system of fish consists of the brain, spinal cord and peripheral nerves
IN 2. Select the features related to non-cranial animals
1) the brain is not differentiated into sections
2) the internal skeleton is represented by a chord
3) excretory organs - kidneys
4) the circulatory system is not closed
5) the organs of vision and hearing are well developed
6) the pharynx is pierced by gill slits
VZ. Establish a correspondence between the signs of animals and the type to which these animals belong.
Part C
C1. Where can deep sea fish store oxygen? Why do they need to do this?
C2. Read the text carefully. Indicate the numbers of sentences in which errors were made. Explain and correct them.
1. Type of chordates - one of the largest in terms of the number of species in the animal kingdom. 2. The internal axial skeleton in all representatives of this type is the chord - a bone, dense, elastic strand 3. The Chordata type is divided into two subtypes - Vertebrates and Invertebrates. 4. In the nervous system, the anterior part of the brain is most developed. 5. All chordates have radial symmetry, a secondary body cavity, and a closed circulatory system. 6. An example of primitive chordates is the lancelet.
