Our planet is inhabited by a wide variety of birds, animals, fish, frogs, snakes, crocodiles, which together form one group - vertebrates.
Why are animals vertebrates?
All living vertebrate creatures within the body have a bone or cartilage skeleton. Therefore, animals were called vertebrates, because the basis of the entire skeleton is nothing more than a vertebral column consisting of bones and a skull. And only in the lower forms there is a peculiar dense rod called the chord.
Features of vertebrates are the presence of the following symptoms. The spinal cord is located inside the spinal column; together with the brain located in the skull, it forms the central nervous system. This is characteristic only of vertebrates.
There are characteristic signs of vertebrates. These are two pairs of legs, fins, paws, wings (extremities), which can sometimes be underdeveloped. By what signs are all animals grouped in groups?
Vertebrate animals and their division into classes
Very different in structure, and in appearance, vertebrates are divided into five classes: fish, amphibians, reptiles, birds and mammals.
Classes of vertebrates are not determined randomly. Of course, all animals are very diverse, but they have similar characteristics. When breathing, absolutely everything absorbs oxygen, and exhale carbon dioxide.
Also, they all eat, receiving nutrients, grow like all living things, and develop. They respond to environmental irritants. A similar feature in most animals is associated with the presence of the nervous system, as well as sensory organs such as eyes and ears.
In addition, they multiply, which means they can reproduce their own kind. Most representatives of absolutely all classes are of great importance in people's lives.
It should be noted that all domestic animals familiar to us belong to vertebrates. These are cows, sheep, horses, chickens, dogs, pigs, cats, etc. Yes, and wild game animals are also vertebrates: hares, foxes, fish, ducks, etc. There are pests among them: hamsters, ground squirrels voles.
We see how different vertebrates are.
Fishes
The rivers, ponds, seas and oceans surrounding us are inhabited by fish. They have their own structural features and adaptability to existence in water conditions.
I must say that fish are aquatic vertebrates. Most of them are covered with scales. They do not have a constant body temperature, and they always breathe only with gills, which take dissolved oxygen from the water and emit, respectively, carbon dioxide. They have a two-chamber heart, but they have only one circle of blood circulation.
The organs of fish movement include fins. In other vertebrates it will already be limbs. In addition, there are also unpaired fins that are located along the body. Their tail is very developed. Interestingly, the fish have such a sensory organ as the lateral line. Most representatives of this group of vertebrates also have a swim bladder.
Fish for humans are of great economic importance. In addition to very useful food products, fat is obtained from fish, which is extracted from cod liver. Expensive and valuable caviar is taken from sturgeon fish. A person receives a lot of more valuable products from fish, and therefore, care must be taken to protect fish stocks and increase them.
Huge fish farming work is being done around the world.
Fish spawn a sufficient amount of caviar, but very few fry are obtained from it under natural conditions. For example, in chum salmon, only one percent of fry leave the whole caviar. Therefore, people with might and main began to use artificial insemination of eggs, which gives a large number of offspring. Fry develops under observation in artificial conditions, and then young growth is released into natural habitat. Of course, the most popular breeding of sturgeon and salmon fish.
Reptiles
Who are reptiles? Their list is quite large and varied. This class was called so because its representatives, moving on the ground, drag their body, as if they were reptiles. Here comes the name.
What species are reptiles in the class? The list is very diverse:
- Lizards.
- Snakes.
- Crocodiles.
- Turtles.
- Dinosaurs
Most often we can meet a lizard in nature. Snakes are also considered reptiles, although they are very different from lizards, however, they have a similar internal structure.
Most of this class is good for humans. Lizards, for example, destroy harmful insects, snakes - rodents, which damage crops.
However, there are also species that are very harmful. Poisonous snakes are especially dangerous for humans.
The reptile class includes cold-blooded vertebrates. Their bodies are covered with plates. They breathe atmospheric air using their lungs. Many reptiles lead a land life. But even those who have adapted to dwell in water (crocodiles, turtles) breed in the same way as the rest of the class, laying eggs in the sand on land. And this suggests that their distant ancestors were still land animals.
The occurrence of reptiles was due to climate changes that occurred at the end of the ancient era. It became drier, which led to the loss of many reservoirs that turned into deserts. All these changes led to the fact that, after passing through some stages of development, the first reptiles appeared.
In general, reptiles are the first class of terrestrial amphibians. They developed so quickly that they soon began to dominate and pushed into the background amphibians.
The developmental stages of reptiles in the middle era were particularly rapid. It was during that period that dinosaurs (reptiles) were of impressive size. They lived both on land and in air and in water. Their fossil remains are very interesting, because birds and mammals subsequently arose from them.
Amphibians
Amphibians adapted to life on land, acquired many features that distinguish them from fish. Considering the structure of vertebrates of this class and their lifestyle, it is worth focusing on frogs and toads. They are very useful for people, because they eat a lot of harmful insects, which means they help in the fight against pests. They are combined into a group of tailless amphibians. They got this name due to the lack of a tail. In our rivers and lakes you can find other amphibians, which belong to the group of caudate. This is an ordinary newt.
The class of amphibians includes toads, frogs, newts and other animals - vertebrates that already live on land, and not like fish - in water, but their habitat is still very closely connected with water, because the process of reproduction and development takes place in it.
The body of amphibians is covered with skin, only very mucous. The limbs have five fingers. Adults breathe through the skin and lungs, but the larvae have gill breathing. The eggs do not have any protection, and therefore an aquatic environment is chosen for their development. Later, the offspring acquire gills, because small tadpoles live and feed in water. Then, in the process of development, the lungs and paws appear, which gives adults the opportunity to move on land. Amphibians do not know how to chew, they swallow food entirely.
Another group belongs to this class - legless amphibians (worms).
Mammals
Vertebrate mammals are characterized by the presence of a very important trait. Cubs of animals belonging to this group are fed with milk. Hence the name of the class.
Mammals have a huge number of species. These include the simplest animals, and exotic ones: a cow, a dog, a wolf, a fox, a tiger, a giraffe, a lion. The evolutionary process has greatly changed mammals. And today it is the most common species of all animals. And everything is explained by the fact that representatives of this class are able to adapt to a variety of environmental conditions. Groups of vertebrates of this class live all over the globe.
It should be noted that mammals in their structure are the most developed animals. The characteristic distinguishing features of mammals are hairline, warm-bloodedness, a four-chambered heart and, of course, a special structure of the brain.
The ancestors of mammals are considered ancient reptiles. Some modern individuals still have a striking resemblance to the latter. The main distinguishing feature of mammals and reptiles is the peculiar structure of the skeleton.
It should be noted that mammals have a more developed brain. And some are endowed with amazing abilities, such as dolphins and primates. All representatives of this class move on limbs that have fingers.
The division of mammals into groups
In general, this group has about 4200 species. All of them are very different in appearance and behavior. Some animals are very small, one might even say tiny, while others are just real giants. Nevertheless, they all live and reproduce well, some, however, are on the verge of extinction, but to a greater extent due to human activity.
In general, all mammals, depending on how they reproduce their offspring, are divided into three groups: placental, marsupial and cloacal. It should be noted that the person belongs to the placental group. The most unusual animals are cloacal. They lay eggs for reproduction and then hatch them.
But marsupials reproduce cubs underdeveloped, and complete the development process in their bag. But as for the placental animals, they are born fully formed. This group is most widely represented.
Birds
In forests, meadows, in big cities, on poultry farms, wherever we are at any time of the year, we encounter birds everywhere. They are of great economic importance to us. How much food only poultry give us! It is hard to imagine our life without them. And since birds are of such interest to humans, it makes them study them.
The whole class of birds can be divided into such groups: ostrich, typical birds, penguins.
Ostriches mainly live in South America, Australia, Africa. Birds of this group do not know how to fly, their wings are not adapted for this, but they run very well and are able to reach speeds of up to seventy kilometers per hour.
Penguins include seventeen species. Birds of this species are quite peculiar. They differ from other representatives of this class. Their entire body is covered with hard feathers. The forelimbs are either wings or fins. And the lower (hind) limbs have membranes. Penguins on the lower extremities move, helping themselves with their tail.
Such birds feed on the sea, because they swim perfectly. There they can get small fish, crustaceans, mollusks. They move to the sea with the help of fins, and the legs are the steering device.
Although penguins and birds, but most of the time they spend in the water. That is why they have a specific color, like marine animals. In water, penguins are capable of speeds of more than thirty kilometers per hour.
The largest representative of this group is the emperor penguin. Its height reaches one hundred twenty centimeters, and the mass reaches forty-five kilograms. Emperor penguins breed eggs. However, as a rule, they have only one chick.
Typical birds
The third systematic group of the bird class is typical birds. There are mainly flying species. They are perfectly adapted to flight. Such birds are widespread around the world. In doing so, they migrate. And this happens with the onset of the cold season, then the birds look for a convenient place for wintering, and with the advent of spring they return home. Some representatives of this group remain for the winter and do not fly away, but they do not always manage to survive the cold, although they have dense plumage.
Invertebrates of our world
As we said above, there are vertebrate animals, and there are invertebrates.
So, invertebrates are characterized by a more simplified structure. These include mollusks, crayfish, insects, spiders. At this stage, humanity knows more than one million different species of invertebrates.
It should be noted that many of the invertebrates are inherently parasites of either vertebrates or plants. Such animals are distributed quite unevenly throughout the earth.
These animals are extremely important for the biosphere. The hardened remains of ancient invertebrates that lived in prehistoric times fell into various geological formations. They are of considerable importance for people. People consume many of them as food, in addition, they are used as food for industrial animals. And some invertebrates have long been used by people in pest control.
In general, vertebrate and invertebrate animals carry out their functions in the biosphere. All of them are important for humans.
Comparative characteristics of vertebrates and invertebrates
If we talk about vertebrates and invertebrates, it should be noted that they have a number of distinguishing features.
So, vertebrates, as we said, have an internal bony or cartilaginous shaft, which is not observed in invertebrates. In addition, the spinal cord is presented in the form of a tube, and the brain already has five sections. In the process of breathing vertebrates involved gills, lungs, skin. There is a two-chamber, three-chamber or four-chamber heart, and the circulatory system has a closed structure. The senses are located on the head. Nutrition occurs through the use of jaws.
As for invertebrates, they naturally have a much more simplified structure. They do not have an internal skeleton, and the nervous system has a nodular type, the circulatory system is not closed. The heart of invertebrates can be either single-chamber or multi-chamber. The senses are found throughout the body.
