Biological species: definition, names, signs

There is a living matter on the planet Earth. Speaking about it, scientists immediately identify the biological species to which it is divided. Any organism has its own characteristics, name and characteristics. This is what makes it possible to refer it to a certain set of animals.

To the exceptions in this case, you can add only hybrids. They are a single biological species ( see below for a definition ), mixed with another. However, at the moment such mutations are rare enough, therefore in real life an ordinary person can hardly encounter such a thing. But it should be noted an interesting fact: some unusual subspecies are derived artificially by scientists. An example can be a mule (offspring of a donkey and a mare) and a hound (the result of crossing an ass and a stallion).

To date, the concept of "biological species" unites more than 1 million animals and plants, not counting those that have not yet been studied. Every year this figure is rapidly growing, as new representatives of flora and fauna are constantly being opened.

Types of living matter

So, in essence, the species is a collection of similar individuals according to functions, behavior, general characteristics, appearance and other properties inherent in a given plant or animal.

Formation of the concept began closer to the XVII century. It was then that a sufficient number of representatives of living organisms were already known. But at that time the term "biological species" was used as a collective name (wheat, oak, oats, a dog, a fox, a crow, a tit, etc.). With the study of a larger number of organisms, there appeared the need for the ordering of names and the formation of a hierarchy. In 1735 the work of Linnaeus appeared, which introduced some corrections. Representatives closer to each other were gathered into childbirth, and the latter were divided into groups and classes. By the end of the 18th century, the leading biologists of the world had accepted these provisions as fundamental.

For a long time, biological species for scientists were a closed system. Previously, this phrase meant the impossibility of transferring genes from one organism to another (provided that they belong to different sets of living matter). More often, the cross between species is found in plants. This process is easier to reproduce, if only because they are able to "exchange" the genes themselves without the intervention of the human hand. That is why the biological species of plants is so rich.

However, today there are hybrids of animals, which have already been mentioned above. Some of them are able to reproduce their offspring (for example, females of ligers and tigons are prolific). And others do not have such a function (we are talking about mules and hinnies).

Birds

Birds are called a class of vertebrates, a characteristic feature of which is the feather cover. Previously, there were species of Moa birds that were born wingless. However, they have long been extinct, and their descendants are kiwis.

Some species are able to fly, however, for example, ostriches and penguins are deprived of this function.

Expeditions of archeologists made it possible to find out that the direct ancestors of birds are dinosaurs. There is a version and that, probably, feathered animals are the only survivors of the Mesozoic era in the world.

Due to classifications, organisms are divided into domestic and wild. Each of these stages is divided into views. Birds differ from other representatives of living matter by the presence of a feather coating, the lack of teeth, a very uneven skeleton (but sufficiently strong), a 4-chambered heart, etc.

Human

Many believe that man is the highest stage in the evolution of animals. However, some scientists, citing various facts, refute this statement. Neanthropines belong to the class of mammals and to the order of primates.

Man as a biological species is able to exert a strong influence on the environment. However, the main difference between this representative of the animal world and other less developed ones is the presence of strong intelligence. Thanks to him, there were answers to many questions. But the development process of the species is rather thorny. Only 1.5 million years ago, human life expectancy was about 20 years, and the population did not exceed 500 thousand.

Symptoms

Any characteristic of the biological species begins with the presentation of the attributes of belonging to a certain set of individuals. There are several similar criteria:

• Morphological. It allows you to distinguish one view from another, taking into account only external characteristics.
• Physiological and biochemical. Due to this criterion, scientists share different chemical properties and functions of individuals.
• Geographical. The sign indicates where the species can live, and also where it is distributed and localized at the moment.
• Ecological. This criterion allows you to learn about attempts to settle down on the ground, as well as learn more about what kind of living area is more suitable for certain organisms.
• Reproductive. He speaks of so-called reproductive isolation. These are factors that prevent the transfer of genes even closely related individuals.

The listed characteristics are generally accepted and basic. However, in addition to these, there are others: a chromosome criterion, etc.

Each species has an individual genetic system, which, in turn, is closed. This indicates the inability of natural mating between representatives of different populations.

Due to the fact that any biological species (examples are available in the article) are dependent on climatic conditions and other factors, individuals in one area are unevenly distributed. They unite in the population.

Species are also divided into subspecies. The latter are united by a common geographic location or environmental factor.

Criteria of the species: morphological

Biological species have common features that manifest themselves in appearance. It is the morphological feature that makes it possible to unite non-contiguous individuals into one group. Every person, even a small child, will be able to distinguish the cat from the dog, the older one is the dog from the fox, but it will be difficult to separate the fox from the Arctic fox without the appropriate knowledge.

However, the morphological criterion is not in all cases sufficiently competent. In the world there are biological species that are too similar to each other. With such problems, scientists collect consulations and are closely involved in the analysis of the proposed representatives. Species-twins are not very common, but they do exist, and they should be distinguished. Otherwise there will be chaos.

Cytogenetic and molecular-biological signs

To describe this criterion it is necessary to recall the school course of biology. Teachers explained that each representative of a particular species has a certain set of chromosomes, called karyotype. Related individuals have the same structure, functions, number, size of structures containing genes. It is thanks to this characteristic that the so-called twin species can be distinguished from each other.

Using the example of a voles, it is possible to show how the sets differ from each other. In the ordinary, there are 46 chromosomes, in the East European and Kirghizian - 54 (they differ in the structure of the structural unit), in the Trans-Caspian - 52.

However, even in this case there are exceptions. The method described does not always turn out to be particularly accurate. For example, the ancient felines had an absolutely identical karyotype, although they belonged to different species.

Reproductive isolation

This factor indicates the existence of a closed genetic system. It should be properly understood this criterion. Representatives of one species from different populations are able to interbreed with individuals from another population. Due to this genes pass to completely different places of residence.

Reproductive isolation also occurs because of different structures of genital organs, size and color. This applies not only to animals, but also to plants. It is necessary to look into botany - "alien" pollen is rejected by the flower and stigmas are not perceived.

Names of species

All names of species are added according to the general scheme and, as a rule, are written in Latin. In order to distinguish certain representatives, the general name of the genus is taken, then a species epithet is added to it.

For example, Petasites fragrans or Petasites fominii. As you can see, the first word is always written with a capital letter, and the second - with a lowercase letter. In Russian, the names are translated as "fragrant white-legged" and "Foumin's white-clover", respectively.

Variability of the biological species

Any biological species can genetically change. It can pursue both the entire population and be individual. Distinguish between hereditary variability and modification. The first has the property to act on genes and chromosomes, thus changing the standard karyotype of the animal. This problem can not be eliminated, and the organism lives with it throughout the whole time. Modification variability does not affect the further offspring in any way, since it does not affect genes and chromosome set. The problem arises from the influence of certain factors. It is worth getting rid of them, as soon as the changes disappear.

Genetic and modification changes

Each variability is divided into several types. For genetic problems, such processes are characteristic: mutations and gene combinations.

For modification - the reaction rate. This process implies the influence of the environment on the genotype, which causes various changes in the karyotype. In the event that the body adapts to it, then there will be no problems for existence.