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 have a bone or cartilage skeleton inside the body. Therefore, animals are called vertebrates, because the basis of the entire skeleton is nothing more than the vertebral column, consisting of bones and a skull. And only the lower forms have a kind of dense core, called a chord.
Features of vertebrates are that they have the following features. Inside the spinal column is the spinal cord, together with the brain located in the skull, it makes up 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 (limbs), which can sometimes be underdeveloped. By what signs are all animals combined into groups?
Vertebrates and their division into classes
Very different in structure and appearance, vertebrates are divided into five classes: fish, amphibians, reptiles, birds and mammals.
Classes of vertebrates are not definedby chance. Of course, all animals are very diverse, but they also have similar features. When breathing, absolutely everything absorbs oxygen and exhales carbon dioxide.
Also, they all eat, get nutrients, grow like all living things, and develop. They react to environmental stimuli. A similar feature in most animals is associated with the presence of a nervous system, as well as sensory organs such as eyes and ears.
Besides, they reproduce, 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 vertebrates include all domestic animals familiar to us. These are cows, sheep, horses, chickens, dogs, pigs, cats, etc. And commercial wild animals are also vertebrates: hares, foxes, fish, ducks, etc. There are pests among them: hamsters, ground squirrels, voles.
We see how different vertebrates are.
Pisces
The rivers, ponds, seas and oceans around us are inhabited by fish. They have their own structural features and adaptability to existence in water conditions.
It must be said 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 release carbon dioxide, respectively. They have a two-chambered heart, but they have only one circle of blood circulation.
Fins should be attributed to the organs of movement of fish. Other'svertebrates, these will already be limbs. In addition, there are also unpaired fins that are located along the body. Their tail is very developed. Interestingly, fish have such a sensory organ as the lateral line. Most representatives of this group of vertebrates also have a swim bladder.
Fish are of great economic importance for humans. In addition to very he althy foods, fish are used to obtain fat, which is extracted from cod liver. Expensive and valuable caviar is taken from sturgeon fish. A person receives many more valuable products from fish, and therefore it is necessary to take care of the protection of fish stocks and increase them.
Great fish farming work is going on all over the world.
Fish throw a sufficient amount of caviar, but fry from it in natural conditions, very little is obtained. For example, in chum salmon, only one percent of fry comes out of the entire caviar. Therefore, people began to use artificial insemination of eggs with might and main, which gives a large number of offspring. The fry develop under supervision in artificial conditions, and then the grown-up young animals are released into natural habitat conditions. Of course, the breeding of sturgeon and salmon is the most popular.
Reptiles
Who are reptiles? Their list is quite large and varied. This class was named so due to the fact that its representatives, moving along the ground, drag their body, as if groveling. That's where the name comes from.
What individuals are included in the class of reptiles? The list is very diverse:
- Lizards.
- Snakes.
- Crocodiles.
- Turtles.
- Dinosaurs.
Most often we can meet a lizard in nature. Snakes are also classified as reptiles, although they are very different from lizards, but they have a similar internal structure.
Most of this class is useful to humans. Lizards, for example, destroy harmful insects, snakes - rodents that damage crops.
However, there are also species that are very harmful. Poisonous snakes are especially dangerous for humans.
The class of reptiles includes cold-blooded vertebrates. Their bodies are covered with plates. They breathe atmospheric air using their lungs. Many reptiles lead land life. But even those who have adapted to live in the water (crocodiles, turtles) reproduce 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 terrestrial animals.
The emergence 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 water bodies, which turned into deserts. All these changes led to the fact that, having passed some stages of development, the first reptiles appeared.
In general, reptiles are the first class of terrestrial amphibians. They developed so rapidly that they soon became dominant and overshadowed the amphibians.
Especially rapidly passed the stages of developmentreptiles in the middle era. It was during that period that dinosaurs (reptiles) were of impressive size. They lived both on land and in the air and in the water. Their fossil remains are very interesting, because birds and mammals later arose from them.
Amphibians
Amphibians have adapted to life on land, have acquired many features that distinguish them from fish. Considering the structure of vertebrates of this class and their way of life, 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 pest control. They are combined into a group of tailless amphibians. They got this name because of the lack of a tail. In our rivers and lakes, you can also find other amphibians that belong to the caudate group. This is a common newt.
Toads, frogs, newts and other animals - vertebrates that already live on land, and not like fish - in water, got into the class of amphibians, 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 the aquatic environment is chosen for their development. Later, the offspring acquire gills, because small tadpoles live and feed in the water. Then, in the process of development, lungs and paws appear, which gives adultsthe ability to move on land. Amphibians do not know how to chew, they swallow food whole.
This class includes another group - legless amphibians (worms).
Mammals
Vertebrate mammals are characterized by the presence of a very important feature. The 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 both the simplest animals and exotic ones: a cow, a dog, a wolf, a fox, a tiger, a giraffe, a lion. The process of evolution 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 are the most developed animals in their structure. The characteristic hallmarks of mammals are hair, warm-bloodedness, a four-chambered heart and, of course, a special structure of the brain.
Ancient reptiles are considered to be the ancestors of mammals. 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 generally endowed with amazing abilities, such as dolphins and primates. All representatives of thisclass move on limbs that have fingers.
Division of mammals into groups
In general, this group has about 4200 species. They are all 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 perfectly, 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 a person belongs specifically to the placental group. The most unusual animals are cesspools. They lay eggs for breeding and then incubate them.
But marsupials reproduce cubs underdeveloped, and complete the development process in their bag. But as for placental animals, they are born fully formed. This group is the most widely represented.
Birds
In the forests, in the meadows, in large 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 is given to us only by poultry! It is difficult to imagine our life without them. And since birds are of such interest to humans, this makes them study them.
The whole class of birds can be divided into the following groups: ostriches, typical birds, penguins.
Ostrich live mainly in South America, Australia, Africa. The birds of this group do not know how to fly, their wings are not adapted for this, but they run great and are able to reach speeds of up to seventy kilometers per hour.
Seventeen species are classified as penguins. Birds of this species are quite peculiar. They are different from other representatives of this class. Their whole body is covered with hard feathers. The forelimbs are either wings or flippers. And the lower (hind) limbs have membranes. Penguins move on their lower limbs, helping themselves with their tails.
Such birds feed in the sea, because they are excellent swimmers. There they can get themselves small fish, crustaceans, mollusks. They move in the sea with the help of wings-fins, and their legs are the steering device.
Although penguins are birds, they spend most of their time in the water. That is why they have a specific color, like marine animals. In the water, penguins are capable of reaching speeds of more than thirty kilometers per hour.
The largest representative of this group is the emperor penguin. Its height reaches one hundred and twenty centimeters, and its mass reaches forty-five kilograms. Emperor penguins breed with eggs. In this case, as a rule, they have only one chick.
Typical birds
The third systematic group of the class of birds is typical birds. There are mainly flying species. They are perfectly adapted to flight. These birds are distributed throughoutthe world. At the same time, 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 back home. Some representatives of this group stay 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 vertebrates and there are invertebrates.
So, invertebrates are characterized by a more simplified structure. These include molluscs, crayfish, insects, spiders. At this stage, more than one million different species of invertebrates are known to mankind.
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 eras fell into various geological rocks. They are important to people too. Many of them are eaten by people, in addition, they are used as food for industrial animals. And some invertebrates have long been used by humans in pest control.
In general, vertebrates and invertebrates perform their functions in the biosphere. All of them are important for a person.
Comparative characteristics of vertebrates and invertebrates
If we talk about vertebrates and invertebratesanimals, it should be noted that they have a number of distinctive features.
So, vertebrates, as we said, have an internal bone or cartilage core, 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 respiration of vertebrates, gills, lungs, and skin are involved. There is a two-chamber, three-chamber or four-chamber heart, and the circulatory system has a closed structure. The sense organs are located on the head. Nutrition occurs through the use of the 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 knotty type, the circulatory system is not closed. The heart of invertebrates can be both single-chambered and multi-chambered. The sense organs are all over the body.
Instead of afterword
All structural features of vertebrates give them the opportunity to lead an active lifestyle. That is, vertebrates can move well, and this is very important for finding food. This, in turn, pushed them to the fore in the process of evolution. A higher level of vitality, the ability to defend themselves from enemies provided these animals with the opportunity to settle around the world.
Schoolchildren to understand the nuances of the structure and life of vertebrates will help such a subject as biology. Vertebrates are studied in the eighth grade. This topic helps to understand the patterns of evolutionaryprocess, showing by example how living beings developed from the simplest to highly organized organisms.
Having gone through many changes and transformations, vertebrates have reached a level of development that allows them to lead a fairly active lifestyle, get their own food, defend themselves from enemies, and raise offspring.
