Biography of cartilaginous fish

Mammals of Mammals of Nastrass of Pisces Fish are the lower maxillofacial primary water vertebrates. About 33 thousand species of fish are known. An independent section of biology is devoted to them - ichthyology from the Greek. The first burglated fish appeared in Ordovica, cartilaginous fish - at the turn of Silura and Devon, about a million fish live both in fresh and salty waters.

Nastrass of fish is divided into two classes: bone and cartilaginous fish. The common features of all fish are the presence of a streamlined shape of the body, life in water. The body is divided into the head, body and tail. The sensory organs are well developed: vision, hearing, touch, balance. Aromomorphoses of fish fish differ from previous evolutionary forms with new, progressive features of the structure that increased their level of organization.

Let's list them. The appearance of jaws and skulls in fish the first pair of gill arches is modified in the jaw. With the help of jaws, the hunt becomes more effective, and the food is diverse. The fish has a skull - the bone container of the brain and sensory organs, which reliably protects these structures of the nervous system. The pairing fins form the predecessors of the limbs, fins, paired appendages of the body, separate from the body and head, driven by muscular force.

Horde reduction and the formation of a bone spine in the chord fish is reduced, in its place the spine is formed. In cartilaginous fish, the spine has a cartilaginous structure throughout life, and in bone fish the spine ossifies: it is represented by bone tissue. Please note that in the skeleton of cartilage ganoids of sturgeon fish, as well as bicomens of the chord, it persists for life.

This includes the most important subclasses that we will analyze: cartilage, double -sucking and cysteper fish. The main detachments of the class of bone fish are widely known: sturgeon - sturgeon, sterlet, sterlet, beluga carp -like - crucian carp, carp, bream, salmon -shaped silver carpet - trout, salmon, cod, polish, perch -shaped - perch, pike perch for most bone fish are characteristic gill covers covering gills.

Zaberny petals are located directly on the gill arches, there is a swimming bladder. Fertilization external. Most of the bony fish is characterized by indirect development with metamorphosis. This class will be considered by us on the example of a typical representative - river perch. The covers, the musculoskeletal system shape of the body is streamlined, fish-shaped, due to which water friction is reduced.

The surface of the body is covered with leaning on each other like tiles with scales. Most types of scales of Ktenoid from the Greek. There are many glands in the skin that secrete mucus covering the whole body of the fish, which reduces the friction of water. Because of the mucus, it is difficult to hold the caught fish in her hands, it slips out. Plavniks are the organs of the movement of fish.

The fins are both paired chest, abdominal, and unpaired dorsal, tail, anal. The skull is the container of the brain, surrounds it from all sides. The presence of Rostrum from lat. The spine consists of two parts: torso and tail. There is a hole in the center of each vertebra. Add to each other, the blades of the vertebrae together are connected into a single spinal canal in which the spinal cord lies.

The skeleton of the chest fins is connected to the spine of the bones of the shoulder girdle, unlike the skeleton of the abdominal fins, which is not articulated with the spine. There are gill covers, there were no gill covers on the outside of the gill slits at the cartilaginous fish, 5 gill slits were opened separately to the outside. The body cavity is secondary to the whole. The muscle system is segmented, which is expressed in the occurrence of individual differentiated muscle beams.

The most striking example of differentiation is the muscles of the rotary apparatus and pair fins. The digestive system consists of an oral cavity, a pharynx, continuing in the esophagus, stomach, large and small intestines. Many fish in the oral cavity have a tongue and sharp teeth located on the jaws. The teeth are not intended for mechanical grinding of food, but mainly for grasping and retaining production.

There are no salivary glands, there are taste receptors. The ducts of the digestive glands, liver and pancreas, as well as the gall bladder, open in the lumen of the small intestine of fish. There is no spiral valve in the intestines characteristic of cartilaginous fish, the total absorption area increases due to the blindly ending intestinal outgrowths - pyloric appendages.

The breathing system of the pharynx is closely connected not only with the digestive, but also with the respiratory system: there is a gills of fish. With the help of gills, they adapted to pick up oxygen dissolved in it and saturate blood, from where oxygen comes to internal organs and tissues. The breathing process is carried out due to the fact that water through the rotary hole enters the throat.Due to the movements of the gill cover, water from the oropharyngeal cavity is drawn into the side gill cavity, washing the gills.

As a result of gas exchange, oxygen enters the blood of fish, and carbon dioxide leaves it and dissolves in water. The gills consist of a gill arc on which gill stamens and petals are located. Zaber stamens are directed towards the oropharyngeal cavity and prevent the penetration of food particles into the gills. The gill petals are directed outward and braided with a dense network of blood vessels - capillaries, in which gas exchange occurs.

The blood system, like cartilage, bone fish have one circulation circle. The heart is two -chamber, consists of one atrium and one ventricle. Remember that in the heart of fish venous blood. It is pumped with heart in the gills, where it is saturated with oxygen, after which the blood becomes arterial. Arterial blood is directed to the internal organs and tissues, blood moves inside the vessels: a circulatory system of a closed type.

The excretory system consists of paired ribbon torso kidneys of the mesonephros, or primary kidney. They are located on the sides of the body. The ureters that merge with each other and form an expansion - the bladder begins from the kidneys. Urine, containing by -products of metabolism, is excreted from the body of the fish through the anus in females, through the genitourinary hole in males.

The nervous system for all chordal nervous system of tubular type. The brain consists of an oblong, medium brain, cerebellum, intermediate and front brain. The development of the same departments in different classes of chordovs is not the same that you and I will clearly see as this section is studying. I recommend that you pay special attention to this topic. Regarding other classes of chordal brain in fish, it is poorly developed: the anterior cortex is absent, instead of it the surface of the brain is covered with epithelium.

The middle brain reaches the greatest development - the main coordinating center. The cerebellum is also well developed, which is responsible for coordination of movements and the orientation of the body in space. This is due to the complex movements of the fish, which “soars like a bird” is not in the air, but in the aquatic environment. 10 pairs of cranial nerves are taken from the brain.

The fish senses are represented by a special formation - a lateral line stretching in the form of a canal along the whole body from both sides. Sensitive cells of the neuromasts of the side line react to changes in the direction and speed of the water current near the fish. With it, the fish feels the direction and speed of the water. For the first time, a specialized hearing body arises in fish - the inner ear.

With it, they are able to distinguish between sounds, focusing in the aquatic environment. The inner ear is made of three semicircular tubules, upper and lower bags. Sometimes the inner ear is connected to the swimming bubble of somic, carp, due to which the hearing of such fish is more developed. The organs of vision are adapted to the aquatic environment: the lens has a spherical shape.

The cornea is flat, accommodation of configuration of the eye to the best vision of the object occurs only due to the movement of the lens. Pisces see well only at close range. There are organs of taste on the skin and lower jaw, as well as the organs of smell, which open into the oral cavity. The sexual system of fish is separately. The sex glands of males are testes, females are the only ovary.

The fertilization is external, occurs in water: the female scurries eggs of the egg, and the male emits spermatozoa into the water, which merge with the eggs. Over time, young individuals develop from caviar. The development of most fish bone fish is indirect, with metamorphosis. Remember that the process of giving away the caviar and its subsequent fertilization is called spawning, it is seasonal.

In freshwater fish, spawning occurs in the spring, at this time fishing is strictly prohibited. This organ is characteristic exclusively for bone fish: in the cartilaginous fish of the shark, it is absent. The floating bubble is an air bag filled with a mixture of gases: nitrogen, oxygen, carbon dioxide. It performs a number of most important functions: hydrostatic - helps to take a certain position in the water column.

So, when the bubble is expanded, the fish pops up, and when it is reduced, it falls to the bottom. Respiratory - capable of performing the function of lungs baro -receptor - perceives acoustic pressure changes - perceives sounds, plays the role of a similar ear when gas filling the bubble expands: it changes the specific gravity of the fish, it decreases and the fish pops up.

The reverse scheme occurs with a decrease in the bubble. But where does the gas come from, which fills the bubble if the fish lives in the water? Answering this question, we note that all fish are divided into two types: open -bearing and closed -bellied.