There is living matter on planet Earth. Speaking of it, scientists immediately identify the biological species into which it is divided. Any organism has its own characteristics, name and characteristics. This is what allows it to be attributed to a certain set of animals.
To the exceptions in this case, you can add only hybrids. They are one biological species ( see definition below) mixed with another. However, at the moment, such mutations are quite rare, therefore, in real life, an ordinary person is unlikely to encounter such. But an interesting fact should be noted: some unusual subspecies are derived artificially by scientists. An example would be a mule (offspring of a donkey and a mare) and a horn (the result of a mating of a donkey 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 growing rapidly, as new representatives of flora and fauna are constantly opening up.
Types of Living Matter
So, in essence, a species 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, there was a need for ordering of names and the formation of a hierarchy. In 1735, the work of Linnaeus appeared, which made some adjustments. Closer to each other representatives were gathered in childbirth, and the latter were divided into units and classes. By the end of the XVIII century, leading biologists of the world 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 aggregates of living matter). More often, species crosses occur in plants. This process is easier to reproduce if only because they are able to “exchange” genes themselves without human intervention. 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 fertile). And others are not endowed with such a function (we are talking about mules and hinnies).
Birds
It is customary to call birds 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 became extinct long ago, and kiwi are considered their descendants.
Some species are able to fly, however, for example, ostriches and penguins lack this function.
Archaeological expeditions have revealed that dinosaurs are the direct ancestors of birds. There is a version that, perhaps, it is the feathered animals that are the only surviving representatives of the Mesozoic era in the world.
Thanks to classifications, organisms are divided into domestic and wild. Each of these steps is divided into types. Birds differ from other representatives of living matter by the presence of feather cover, the absence of teeth, the skeleton that is very non-burdensome in mass (but strong enough), a 4-chamber heart, etc.
Man
Many believe that man is the highest stage of the evolution of animals. 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 able to have a strong impact on the environment. However, the main difference between this representative of the animal world from other, less developed, is the presence of a strong intelligence. Thanks to him, answers were found to many questions. But the development process of the species is quite thorny. Just 1.5 million years ago, human 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 particular set 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. Thanks to this criterion, scientists share various chemical properties and functions of individuals.
- Geographical. The sign indicates where this or that species can live, as well as where exactly it is distributed and localized at the moment.
- Ecological. This criterion allows you to learn about attempts to take root on the ground, as well as to learn more about which zone for living is more suitable for certain organisms.
- Reproductive. He talks about so-called reproductive isolation. We are talking about factors that impede the transfer of genes even closely related individuals.
The listed signs are generally accepted and basic. However, in addition to them, there are others: a 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 are unevenly distributed in one area. They unite 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 that manifest themselves in appearance. It is a morphological trait that allows you to combine non-closely related individuals into one group. Each person, even a small child, will be able to distinguish a cat from a dog, an older one can distinguish a dog from a fox, but it will be difficult to separate a fox from a fox without 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 gather consultations and are closely engaged in the analysis of the proposed representatives. Double species are not very common, but they are still there, and they should be distinguished. Otherwise, chaos will come.
Cytogenetic and molecular biological characteristics
To describe this criterion, it is necessary to recall the school biology course. Teachers explained that each representative of a particular biological species has a specific set of chromosomes, called the karyotype. Related individuals have the same structure, function, quantity, size of structures containing genes. It is thanks to this feature that one can distinguish from each other the so-called twin species.
Using the example of a field vole, one can show how exactly the aggregates differ from each other. The common has 46 chromosomes, the East European and Kyrgyz - 54 (they differ in the structure of the structural unit), the Trans-Caspian - 52.
However, even in this case there are exceptions. The described method is not always particularly accurate. For example, the ancient feline 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 should be correctly understood. Representatives of one species from different populations are able to interbreed with individuals from another population. Thanks to this, genes go to completely different places of residence.
Reproductive isolation also occurs due to the different structures of the genitals, size and color. This applies not only to animals, but also to plants. One should look into botany - “alien” 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 highlight certain representatives, the generic name of the genus is taken, then a species epithet is added to it.
Examples include Petasites fragrans or Petasites fominii. As you can see, the first word is always capitalized, and the second is lowercase. Names are translated into Russian as “fragrant butterbur” and “Fomin butterbur”, respectively.
Species Variability
Any species can genetically change. This can pursue both the entire population and be individual. Distinguish between hereditary and modification. The first has the property of affecting genes and chromosomes, thereby changing the standard karyotype of an animal. This problem cannot be eliminated, and the body lives with it throughout the entire time. Modification variability does not affect further offspring, 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, 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 connections.
For modification - the reaction rate. This process means the influence of the environment on the genotype, due to which various changes in the karyotype occur. In that case, if the body adapts to it, then no problems for existence will arise.