There is living matter on planet Earth. Speaking about it, scientists immediately identify the biological species into which it is divided. Any organism has its own signs, name and characteristics. This is what allows us to attribute it to a certain population of animals.
Only hybrids can be added to the exceptions in this case. They are one species (see definition below) mixed with another. However, at the moment, such mutations are quite rare, so in real life, an ordinary person is unlikely to encounter such a thing. But an interesting fact should be noted: some unusual subspecies are artificially bred by scientists. An example would be a mule (offspring of a donkey and a mare) and a hinny (the result of crossing a donkey and a stallion).
Today, 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 growing rapidly, as new representatives of flora and fauna are constantly being discovered.
Types of living matter
So basically the view is -a collection of similar individuals in terms of functions, behavior, general characteristics, appearance and other properties inherent in a given plant or animal.
The 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 concept of "biological species" was used as a collective name (wheat, oak, oats, dog, fox, crow, tit, etc.). With the study of more organisms, the need arose for the ordering of names and the formation of a hierarchy. In 1735, a work by Linnaeus appeared, which made some adjustments. Representatives closer to each other were collected into genera, and the latter were divided into detachments and classes. By the end of the 18th century, the leading biologists of the world accepted these provisions as fundamental.
For a long time, species have been a closed system for scientists. Previously, this phrase implied the impossibility of transferring genes from one organism to another (provided that they belong to different sets of living matter). More often, crossbreeds of species are found in plants. This process is easier to reproduce, if only because they are able to “exchange” genes themselves without the intervention of a human hand. That is why the plant species is so rich.
However, today there are also hybrids of animals, which have already been mentioned above. Some of them are able to reproduce their offspring (for example, female ligers and taigons are fertile). And others are not endowed with such a function (we are talking about mules and hinnies).
Birds
Birds are usually called a class of vertebrates, a characteristic feature of which is a feather cover. Previously, there were species of the moa bird that were born wingless. However, they died out long ago, and kiwis are considered their descendants.
Some species are able to fly, but ostriches and penguins, for example, lack this ability.
Expeditions of archaeologists made it possible to find out that the direct ancestors of birds are dinosaurs. There is a version that, perhaps, it is feathered animals that are the only surviving representatives of the Mesozoic era in the world.
Due to the classifications, organisms are divided into domestic and wild. Each of these steps is divided into types. Birds differ from other representatives of living matter in the presence of a feather covering, the absence of teeth, a skeleton that is not burdensome in terms of mass (but strong enough), a 4-chambered heart, etc.
Man
Many believe that man is the highest stage of animal evolution. However, some scientists, citing various facts, refute this statement. Neoanthropes belong to the class of mammals and to the order of primates.
Man as a biological species is capable of exerting a strong impact on the environment. However, the main difference between this representative of the animal world and other less developed ones is the presence of a strong intellect. Thanks to him, answers to many questions were found. But the process of development of the species is quite thorny. Just 1.5 million years agohuman life expectancy was about 20 years, and the population did not exceed 500 thousand.
Signs
Any characteristic of a biological species begins with the presentation of signs of belonging to a certain population of individuals. There are several similar criteria:
- Morphological. It allows you to distinguish one species from another, taking into account only external characteristics.
- Physiological and biochemical. Through this criterion, scientists separate the various chemical properties and functions of individuals.
- Geographic. The sign indicates where this or that species can live, as well as where exactly it is distributed and localized at the moment.
- Environmental. This criterion allows you to learn about attempts to take root in the area, as well as learn more about which area to live in is more suitable for certain organisms.
- Reproductive. He talks about the so-called reproductive isolation. We are talking about factors that prevent the transfer of genes even of closely related individuals.
The listed signs are generally accepted and basic. However, there are others besides them: chromosomal 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) is dependent on climatic conditions and other factors, individuals inin the same area are distributed unevenly. They come together in a population.
Species are also divided into subspecies. The latter are combined due to a common geographical location or environmental factor.
View criteria: morphological
Biological species have common features, manifested in appearance. It is the morphological trait that makes it possible to unite non-closely related individuals into one group. Every person, even a small child, will be able to distinguish a cat from a dog, an older person - a dog from a fox, but it will be difficult to separate a fox from an arctic fox without proper knowledge.
However, the morphological criterion is not competent enough in all cases. There are biological species in the world that are too similar to each other. With such problems, scientists gather councils and closely deal with the analysis of the proposed representatives. Species-twins are not very common, but they still exist, and they should be distinguished. Because otherwise there will be chaos.
Cytogenetic and molecular biological features
To describe this criterion, you need to remember the school biology course. The teachers explained that each representative of a particular biological species has a certain set of chromosomes, called a karyotype. Related individuals have the same structure, functions, number, size of structures containing genes. It is thanks to this feature that the so-called twin species can be distinguished from each other.
Using the example of a vole, one can show exactly how aggregatesdiffer from each other. The common one has 46 chromosomes, the Eastern European and Kyrgyz have 54 (they differ in the structure of the structural unit), the Transcaspian has 52.
However, even in this case, there are exceptions. The method described is not always particularly accurate. For example, ancient cats had exactly the same karyotype, although they belonged to different species.
Reproductive isolation
This factor indicates the presence of a closed genetic system. This criterion must be properly understood. Representatives of one species from different populations are able to interbreed with individuals from another population. Thanks to this, genes move to completely different places of residence.
Reproductive isolation also occurs due to different structures of the genital organs, sizes and colors. This applies not only to animals, but also to plants. You should look into botany - "foreign" pollen is rejected by the flower and is not perceived by the stigmas.
Species names
All species names are formed according to the general scheme and, as a rule, are written in Latin. In order to distinguish certain representatives, the common name of the genus is taken, then the specific epithet is added to it.
An example would be Petasites fragrans or Petasites fominii. As you can see, the first word is always capitalized and the second word is always lowercase. The names are translated into Russian as "fragrant butterbur" and "Fomin's butterbur", respectively.
Species variation
Any species can genetically change. It can persecute both the entire population and be individual. Distinguish between hereditary variability and modification. The first has the ability to act on genes and chromosomes, thereby changing the standard karyotype of the animal. This problem cannot be eliminated, and the body lives with it throughout the entire time. Modification variability does not affect further offspring in any way, since it does not affect genes and the chromosome set. The problem arises under the influence of certain factors. Once you get rid of them, the changes will immediately disappear.
Genetic and modification changes
Each variability is divided into several types. Genetic problems are characterized by such processes: mutations and combinations of genes.
For modification - the rate of reaction. This process refers to the influence of the environment on the genotype, due to which various changes in the karyotype occur. In the event that the body adapts to it, then there will be no problems for existence.
