The difference between the ecological criterion of a species and the morphological one. Physiological criterion of the species example. Type: criteria and structure

02.05.2020

Nature has created the living world in such a way that each type of organisms differs from the other in the way of feeding, as well as in the territory of residence. If we take, for example, birds, we can see that there are visible differences between the tit, the chickadee, and the blue tit in the choice of insects for providing themselves with food, as well as in the processes of obtaining food. Someone seeks out food for himself in the bark of a tree, and someone - in the leaves of plants. Moreover, they all belong to the genus of tits.

Of course, the ecological criterion is not multifunctional in terms of features, because science has proven that some animals of different species can have identical properties according to this criterion. For example, everyone eats small crustaceans, and their way of life also coincides, although they live in different seas.

What is a view?

Let us examine in detail what he means. In the scientific world, he assumes a set of living beings and plants that have the ability to interbreed with each other, as well as have offspring.

The species falls under the definition because today it is precisely a group of related organic formations that have the same root cause of occurrence, but at the moment they are endowed with certain signs of a morphological, physiological and biochemical nature, separated by natural or artificial selection from other species groups and adapted for a specific habitat.

Formation of new species

How are views created? - the main engines of the formation of new types. In the first case, the emergence of qualitatively new family groups and orders, which appeared as a result of long-term microevolutionary changes, is implied. In the second, a complex process of mutations takes place, which gradually separate entire families and orders, forming new species. And in this case they become a separate complex of organisms.

That is, thanks to microevolution, which is also defined as "supraspecific", species are even more divided in terms of their qualities, transforming into groups with the same set of features. This can be understood by the example of the ecological criterion of the species: there is also a hard variety, which means that in a general sense it is a genus of wheat, and there are grains of rye, wheat and barley, and all of them are representatives of the cereal family. From this we can conclude that all samples of any families descended from some common ancestor, thanks to microevolutionary processes that occurred in the population of this progenitor itself.

What is the ecological criterion of a species

The definition is the complex impact of ecological features on a species in its range. These signs are divided into groups: biotic factors (when living organisms influence each other, for example, by pollinating plants with bees), abiotic factors (the effect of temperature, humidity, light, topography, soil, water salinity, wind, and so on on the development of living organisms ) and anthropogenic factors (human impact on the surrounding flora and fauna).

In all species of the animal and plant world, constructive signs of adaptation to the environment are formed during evolution, and the nature of the habitat for the whole species is the same. What examples of the ecological criterion of a species can be given if it is considered from this point of view? The unity of the species is associated with the free crossing of individuals. Plus, historical development shows that over time, a species may develop a completely new adaptation, for example, giving certain signals to each other when a situation arises, or the appearance of a group defense against enemies.

An example of an ecological criterion for a species would be isolation. That is, when ecological conditions are different for the same species, differences in their behavior and morphological structure will be significant. A good illustration are urban and rural swifts. If they are planted in one cell, then there will be no offspring, because during their life in different ecological conditions, individuals of this species have developed various morphological, physiological and other characteristics. But they continue to be under the "roof" of the same species, and this is an example of the ecological criterion of an animal species.

Flora in ecological criteria

Examples of the ecological criterion of species in plants are those that can form several ecotypes, some of which will live in the plains, and others in the highlands. These include, for example, St. John's wort, some species of which, thanks to microevolution, quickly adapted to new growing conditions.

The influence of the external environment on the evolution of the species

The well-known researcher Lamarck believed that the inorganic environment, that is, its physical and chemical compositions (temperature, climatic conditions, water resources, soil composition, and so on) has the greatest influence on a living organism. Everything that fell under their influence could change the types of living organisms, giving them the characteristics inherent in a given ecological niche. Due to forced adaptation, the animal (plant) began to change, thereby forming a new species or subspecies. This can be called an example of the ecological criterion of a species.

Temperature regime within the ecological criterion

An example of a species according to an ecological criterion can be a living organism adapted to different temperature regimes. During adaptation, a biochemical change in internal organs and tissues occurs. Due to the fact that animals can live in low, high or fluctuating temperatures, they are divided into groups: cold-blooded, warm-blooded and heterothermal.

Given that heat sources are both external and internal factors, then, considering the first group using the example of lizards, you can see that they prefer to bask in the sun rather than hide in the shade. This means that their internal ability to thermoregulate is very low. Being under the heat flow, they increase the body temperature quickly enough. However, by evaporating the accumulated moisture, the lizard can reduce it to a comfortable level. Such species are organisms of lower development. But despite this, they cannot exist at low temperatures without external heat.

From examples of biology: the ecological criterion for the species of a warm-blooded group includes almost all mammals and birds. Thermoregulation in their bodies occurs on the physical (breathing, evaporation, etc.) and chemical (intensity in metabolism) plan. In addition, warm-blooded organisms can shiver, thereby raising their body temperature, in animals with feathers and undercoat, thermal insulation occurs when they are raised. Cold wind or hot sun, such organisms have to look for an alternative: a shade of coolness or good shelter from frostbite.

The third group is an intermediate stage between the first two. This usually includes species of primitive animals and birds, as well as those living organisms that have their own hibernation period, that is, they themselves can control body temperature, reduce or increase it. As an example, we can take a marmot, which in winter, falling into hibernation, lowers its body temperature to six degrees, and during the active period of life raises it to human.

The influence of soil on the development of the species

In addition to climatic conditions, the soil environment of the range is very important for the species. In this case, representatives of underground inhabitants can be taken as an example of the ecological criterion of a species. Little "diggers" have only one function for survival - it is to dig their own dwelling as best and as deep as possible so that not a single predator can get them.

They use their limbs, which are adapted to a certain type of soil, that is, with a change in the place of residence in the form of soil, the limbs must adapt from time to time. All living organisms like the mole have a similar paw structure, and living underground has adapted the animal to lack of oxygen and suffocation, and this is an inevitable situation.

The value of atmospheric precipitation on the example of the ecological criterion of the species

Creatures that have adapted to snow cover, frequent rainfall, hail, high humidity, and so on have special differences in the structure of the body. In biology, the ecological criterion of a species will be the change in the animal cover to match the color of the snow. This happens in birds, hares, for example, a white partridge turns really white, changing its feather plumage.

Winter "clothing" is much warmer, and constant exposure to snow increases heat transfer. How? It turns out that under a layer of snow the air temperature is much higher than outside. Therefore, hibernating bears endure the winter perfectly, spending the night in snow dens. Organisms develop special adaptations on their limbs for movement on snow, whether it be sharp claws for walking on ice or webbed feet for moving through tropical flooded forests.

Since the ecology on the planet is constantly changing, the processes of microevolution, during which living beings adapt to new living conditions, continue.

Species definition

Until the 17th century researchers relied on the concept of a species created by Aristotle, who considered species to be a collection of outwardly similar individuals. This approach, without fundamental changes, was used by many biologists, including Carl Linnaeus, the founder of modern biological systematics.

Linnaeus introduced binary, or binomial, nomenclature- the method of designating species accepted in biological taxonomy using a two-word name (binomen), consisting of a combination of two names (names): the name of the genus and the name of the species (according to the terminology adopted in zoological nomenclature) or the name of the genus and the specific epithet (according to botanical terminology).

rules for writing specific names

In Latin, the name of the genus is always written with a capital letter, the name of the species (specific epithet) is always with a small letter (even if it comes from a proper name). In the text, the species name is usually written in italics. The species name (specific epithet) should not be given separately from the genus name, since without the genus name it is meaningless. In some cases, the genus name can be shortened to a single letter or a standard abbreviation.

Further development of biology led to the formation biological concept of species. This concept suggests that a species is not a conditional category singled out by people for convenience, but a real-life community of organisms, characterized primarily by genetic unity and common origin. This genetic unity is the root cause of the external similarity of organisms of the same species, that is, for the selection of species, it is not the external similarity that is primary, but the genetic commonality.

For organisms with sexual reproduction, the boundary between species forms reproductive isolation- this is the inability of two different species, when crossed, to produce fertile offspring. The offspring may be quite healthy, but sterile, such as, for example, the offspring of crossing a horse and a donkey - mules and hinnies (although one of the sexes may retain partial fertility).

In asexual organisms, the species is more difficult to determine. For them, a species is a set of clones united by a common ecological niche and therefore evolving together, in a similar way. This primarily concerns prokaryotes and many plants.

According to the modern definition, view(lat. species)- the main unit of the biological systematics of living organisms, a group of individuals with common morphophysiological, biochemical and behavioral characteristics, capable of interbreeding, giving fertile offspring in a number of generations, regularly distributed within a certain area and similarly changing under the influence of environmental factors.

View criteria

Modern biology highlights type criteria, that is, the criteria by which one set of individuals is characterized as a species and differs from other species.

Morphological criterion of the species. It means the similarity of the external and internal structure of individuals of a species and their differences from representatives of other species.
Even a child can easily distinguish species that are evolutionarily distant from each other in appearance, but in the case of closely related species, this can be difficult even for a specialist.

The issue of identifying close, outwardly similar species often becomes a serious scientific problem. There are so-called sibling species, which are morphologically not different, but are genetically isolated.

It is believed that twin species are found among animals that primarily use smell to find a partner (insects, rodents). Using the example of twin species in Drosophila flies, however, the species-specific structure of the reproductive apparatus was shown, which may underlie the reproductive isolation of these species.

Species-twins of barbels.

Cytogenetic criterion.

Each species has a unique karyotype- a set of chromosomes, characterized by their number, size, position of the centromere, differential staining pattern.

Thus, the analysis of the chromosome set made it possible to separate the species common vole for 4 types:

common vole - 46 chromosomes,

Eastern European vole - 54 chromosomes,

Kirghiz vole - 54, but of a different morphology,

Transcaspian vole - 52 chromosomes.

However, there are cases when distant species have the same karyotypes, for example, representatives of the cat family, and it happens that, on the contrary, representatives of one species vary in the number of chromosomes (for example, the common shrew).

Molecular biological criterion.

There are molecular differences between species. These are, first of all, differences in the sequence of proteins and DNA that arose in the course of evolution. Before the advent of effective technologies for determining the DNA sequence, data on the mobility of proteins during electrophoresis (it characterizes the size and charge of protein molecules) were mainly used. Currently, DNA reading methods are rapidly developing and becoming cheaper, and a lot of data has already been accumulated on the DNA sequence of different organisms. These data are necessarily used to characterize the species.

According to DNA sequences, phylogenetic trees of organisms are built - reconstructions of the paths of evolutionary divergence (divergence), based on establishing the sequence of replacements that have occurred in DNA.

An example of a phylogenetic tree. The numbers are the date of the divergence time in MYA - million years ago, the length of the branches reflects the time.

In DNA, there are evolutionarily conserved regions, that is, they remain relatively unchanged during evolution, and variable regions are changeable. Conserved regions are mainly responsible for vital functions, encoding proteins and RNA, which practically do not differ within huge groups of organisms. For example, one of the main proteins of the cytoskeleton, actin, differs very little in all eukaryotes. Ribosomal RNAs are slowly changing. Their sequences are very convenient to use to build a phylogeny at the level of types and classes.

Variable regions can vary even among individuals within a species. They are used, for example, for genetic identification and genomic fingerprinting(“Genetic fingerprinting”) of people in forensic medicine and forensics.

biochemical criteria.
One of the main criteria for species in microorganisms, primarily in bacteria. Morphologically, bacteria differ little - there are only a few standard types of forms. A much greater variety is characterized by the morphology of bacterial colonies (color, luster, surface texture). But the types of their metabolisms are most diverse among prokaryotes. It is metabolism that determines the ecological niche of a bacterium, and this, in turn, is one of the main criteria for a species in the absence of sexual reproduction. The metabolic features of prokaryotes are easy to establish by growing them on selective media - media in which there is a certain set of substances (sources of carbon, nitrogen, etc.). On a certain medium, only those bacteria can grow that can use the substances present in it in their metabolism and synthesize all the missing substances on their own. Indicators are also added to many media, which change color if the bacteria transform the medium during growth and change its pH.
The figure shows a sterile tube with a set of media of different composition, in which the growth of bacteria is easy to observe, used to identify genera and species of Enterobacteriaceae.

Although the metabolism of multicellular organisms, as a rule, varies much less from species to species, nevertheless this criterion may be essential for them as well. For example, plant species may differ in the spectrum of synthesized alkaloids, flavonoids, essential oils, being very similar morphologically.

Ecological criterion of the species.
This is the ecological niche of a species - a set of environmental factors that are optimal for the species, its relationships with other organisms. Each species occupies its own ecological niche. According to Gause's principle of competitive exclusion, two species in the same ecosystem cannot occupy the same niche - one will inevitably be replaced by the other.

Geographic criterion of the species.
Each type has its own range- area of distribution. However, this criterion is not absolute. In particular, the ranges of different species may overlap strongly, and vice versa, the ranges of some species are broken.
A separate problem is ring ranges some types. “Ring species” are complexes of closely related forms that gradually settled around some geographical barrier, and the extreme, most strongly divergent forms, having met on the other side of the barrier, can no longer interbreed, although they are still connected by a continuous series of mutually compatible varieties. Green warbler Phylloscopus trochiloides considered a good example of an annular view - see picture.

The proposed sequence of settlement and evolution of green warblers. From the region of the Himalayas, where the trochiloides subspecies now lives, warblers settled north in two ways, western and eastern, bypassing the inhospitable Tibetan plateau. Two northern forms, viridanus and plumbeitarsus, by the time of their encounter in Siberia, diverged so much that hybridization between them in the zone of secondary contact almost does not occur.

The physiological criterion of the species is the features of the vital processes of the organism and individual organ systems. First of all, the physiology of reproduction is taken into account: the age of reaching puberty, the duration of pregnancy, the number of cubs, the duration of the feeding period (in mammals), etc.

reproductive isolation

reproductive isolation- the most essential criterion of the species. Individuals of different populations of the same species can interbreed and produce fertile offspring. As a result, there is a flow of genes between populations, and such flows link the species into a single genetic community. But there is no significant flow of genes from species to species due to the presence of reproductive isolation barriers between them.

The significant exception to this rule is horizontal gene transfer. Vertical gene transfer- this is the transfer of genes from the mother organism to the daughter during reproduction; horizontal, in contrast, is associated with the transfer of DNA between unrelated organisms. In particular, this happens with the participation of viruses that integrate into the genome, or by transformation - the capture of DNA fragments from the external environment (this is very typical for bacteria). Thus, when exposed to antibiotics, bacteria of various groups acquire resistance to them, since plasmids with resistance genes are easily transferred from one bacteria to another. The problem of antibiotic resistance is currently of paramount medical importance.
Horizontal gene transfer is extremely intense between prokaryotes, so many researchers currently do not consider the concept of species to be applicable to these organisms at all, since there is significant gene flow even between distant groups of bacteria and archaea. Eukaryotic organisms are characterized by a much lower level of horizontal gene transfer, although some groups are exceptions, for example, fully parthenogenetic invertebrates - bdelloid rotifers, which, apparently, by capturing foreign genes, compensate for the lack of genetic diversity in the absence of sexual reproduction.

Reproductive isolation can be carried out on different levels:

a) prezygotic level- before the fusion of gametes:

Geographic. The presence of geographical barriers prevents crossbreeding;

Behavioral. Marriage rituals, courtship, courtship are extremely important - they are species-specific and play a huge role in separating the species from others. It is also necessary to mention marriage attire, the release of certain substances that attract opposite sexes (pheromones), which are also, as a rule, specific to a given species;

Mechanical (difference in size, incompatibility of the genitals);

different breeding times;

gamete incompatibility. In many flowering plants, pollen grains do not germinate when they land on the stigmas of other species.

b) postzygotic level:

Death of the zygote or embryos, as well as miscarriage during internal development;

Non-viability or weakness of hybrids;

Complete or partial sterility of hybrids (sometimes one sex of hybrids is sterile, while the other is fertile, for example, ligers and taigons - see below).
The main reason underlying hybrid sterility, is the mismatch of karyotypes of crossing species, in particular, number of chromosomes. In the prophase of meiosis, during the formation of germ cells, pairing (conjugation) of homologous chromosomes. If this process is disturbed, meiosis, as a rule, does not occur or defective gametes are formed. Different species have different chromosome sets. They are present together in the genome of an interspecific hybrid. During gametogenesis in a hybrid, not all chromosomes can find a pair for conjugation, and meiosis does not occur.

As a rule, reproductive isolation first occurs at postzygotic levels, and then, since it is unprofitable to spend time and resources on courtship, mating, nesting with poor viability and fertility of the offspring, prezygotic barriers arise - for example, behavioral ones. However, in the case of geographic speciation, isolation barriers may not have time to fully form - crossing still does not occur due to the presence of territorial separation. Therefore, from many species isolated geographically, it is possible to obtain offspring in captivity or artificially.
For example, when crossing a male lion and a female tigress (different species of the same genus Panthera) born lgames(English) liger from English. lion- lion and eng. tiger- tiger). With the opposite direction of crossing, a hybrid that is very different in appearance is obtained - tigrolev, or taigon.
Ligers are the largest living members of the cat family. Ligers are not found in nature mainly because lions and tigers have almost no chance of meeting in the natural environment: the modern range of the lion includes mainly central and southern Africa, while the tiger is exclusively an Asian species. Crossing of species occurs when animals live in the same enclosure or cage for a long time, but only 1-2% of pairs give offspring, which is why no more than two dozen ligers live in the world today. Female ligers are usually fertile, while males are sterile.

ligers

Taigon

In some cases, postzygotic isolation may be absent in the presence of prezygotic isolation. As an example of species that do not interbreed in nature, but give fertile hybrids during artificial insemination, one can cite bester- a valuable hybrid of sturgeon beluga and sterlet.

species problem in prokaryotes

As already mentioned, there are difficulties with species definition in prokaryotes, for the following reasons:

Lack of sexual reproduction.

Weak applicability of the morphological criterion.

Widespread horizontal gene transfer.

In this regard, in microbiology, the molecular genetic criterion is mainly used. In many works it is accepted as a rule to consider the boundary of the species 97% or, according to more recent data, 98.7% of the sequence match of 16S RNA from the small subunit of ribosomes.

The qualitative stage of the evolution process is the species. Bud- is a collection individuals that are similar in morphophysiological characteristics, are able to interbreed, give fertile offspring and form a system of populations that form a common area.

Each type of living organisms can be described on the basis of a set of characteristic features, properties, which are called signs. Features of a species that distinguish one species from another are called criteria kind. There are six general species criteria most commonly used: morphological, physiological, geographical, ecological, genetic, and biochemical.

Morphological criterion involves a description of the external (morphological) features of individuals that are part of a particular species. In appearance, size and color of plumage, for example, it is easy to distinguish a large spotted woodpecker from a green one, a small spotted woodpecker from a yellow one, a great tit from a crested, long-tailed, blue and from a tit. By the appearance of the shoots and inflorescences, the size and arrangement of the leaves, the types of clover are easily distinguished: meadow, creeping, lupine, mountain.

The morphological criterion is the most convenient and therefore widely used in taxonomy. However, this criterion is not sufficient to distinguish between species that have significant morphological similarities. To date, facts have been accumulated that testify to the existence of twin species that do not have noticeable morphological differences, but do not interbreed in nature due to the presence of different chromosome sets. So, under the name “black rat”, two twin species are distinguished: rats with 38 chromosomes in the karyotype and living throughout Europe, Africa, America, Australia, New Zealand, Asia west of India, and rats with 42 chromosomes. the distribution of which is associated with the Mongoloid settled civilizations inhabiting Asia east of Burma. It has also been established that under the name "malarial mosquito" there are 15 outwardly indistinguishable species.

Physiological criterion lies in the similarity of life processes, primarily in the possibility of crossing between individuals of the same species with the formation of fertile offspring. There is a physiological isolation between different species. For example, in many species of Drosophila, the sperm of an alien species causes an immunological reaction in the female genital tract, leading to sperm death. At the same time, interbreeding is possible between certain types of living organisms; at the same time, fertile hybrids can form (finches, canaries, crows, hares, poplars, willows, etc.)

There are also species that have a broken range. So, for example, linden grows in Europe, is found in the Kuznetsk Alatau and the Krasnoyarsk Territory. The blue magpie has two parts of its range - Western European and East Siberian. Due to these circumstances, the geographical criterion, like others, is not absolute.

Environmental criterion is based on the fact that each species can exist only under certain conditions, performing the corresponding function in a certain biogeocenosis. In other words, each species occupies a specific ecological niche. For example, the caustic buttercup grows in floodplain meadows, the creeping buttercup grows along the banks of rivers and ditches, the burning buttercup grows in wetlands. There are, however, species that do not have a strict ecological confinement. First, these are synanthropic species. Secondly, these are species that are under human care: indoor and cultivated plants, pets.

Genetic (cytomorphological) criterion based on the difference between species according to karyotypes, i.e., according to the number, shape and size of chromosomes. The vast majority of species are characterized by a strictly defined karyotype. However, this criterion is not universal. First, in many different species, the number of chromosomes is the same and their shape is similar. So, many species from the legume family have 22 chromosomes (2n = 22). Secondly, individuals with different numbers of chromosomes can occur within the same species, which is the result of genomic mutations. For example, goat willow has a diploid (38) and tetraploid (76) chromosome number. In silver carp, there are populations with a set of chromosomes 100, 150,200, while their normal number is 50. specific type.

Biochemical criterion allows you to distinguish species by biochemical parameters (composition and structure of certain proteins, nucleic acids and other substances). It is known that the synthesis of certain macromolecular substances is inherent only in certain groups of species. For example, according to the ability to form and accumulate alkaloids, plant species differ within the families of nightshade, composite, lily, orchid. Or, for example, for two species of butterflies from the genus Amata, the diagnostic feature is the presence of two enzymes - phosphoglucomutase and esterase-5. However, this criterion is not widely used - it is laborious and far from universal. There is significant intraspecific variability in almost all biochemical parameters up to the sequence of amino acids in protein molecules and nucleotides in individual DNA regions.

Thus, none of the criteria alone can serve to determine the species. It is possible to characterize a species only by their totality.

Source : ON THE. Lemeza L.V. Kamlyuk N.D. Lisov "Biology manual for applicants to universities"

The qualitative stage of the process of evolution is the species. Bud- is a collection individuals | individuals that are similar in morphophysiological characteristics, are able to interbreed, produce fertile offspring and form a system of populations that form a common area.

Each type of living organisms can be described on the basis of a combination of characteristic | characteristic features | features, properties, which are called signs. Features of a species that distinguish one species from another are called criteria kind. There are six general species criteria most commonly used: morphological, physiological, geographical, ecological, genetic, and biochemical.

Morphological criterion involves a description of the external (morphological) features of individuals | individuals that are part of a particular species. In appearance, size and color of the plumage, for example, it is easy to distinguish the great spotted woodpecker from the green, the lesser spotted woodpecker from the yellow, the great | great tit from the crested, long-tailed, blue and from the chickadee. By the appearance of the shoots and inflorescences, the size and arrangement of the leaves, the types of clover | clover are easily distinguished: meadow, creeping, lupine, mountain.

The morphological criterion is the most convenient and is therefore widely used in taxonomy. However, this criterion is not sufficient to distinguish between species that have significant morphological similarities. To date, facts have been accumulated that testify to the existence of twin species that do not have noticeable morphological differences, but do not interbreed in nature due to the presence of different chromosome sets. So, under the name “black rat”, two twin species are distinguished: rats with 38 chromosomes in the karyotype and living throughout Europe, Africa, America, Australia, New Zealand, Asia west | west of India, and rats with 42 chromosomes, the distribution of which is associated with the Mongoloid settled civilizations inhabiting Asia east of Burma. It has also been established that under the name "malarial mosquito" there are 15 outwardly indistinguishable species.

Physiological criterion lies in the similarity of life processes, primarily in the possibility of crossing between individuals of the same species with the formation of fertile offspring. There is a physiological isolation between different species. For example, in many species of Drosophila, the sperm of individuals of a foreign species causes an immunological reaction in the female genital tract, which leads to the death of spermatozoa. At the same time, interbreeding is possible between certain types of living organisms; at the same time, fertile hybrids can form (finches, canaries, crows | crows, hares, poplars | poplars, willows, etc.)

Geographical criterion (geographical certainty of the species) based on the fact that each species occupies a certain territory or water area. In other words, each type is characterized by a certain geographic area. Many species occupy different ranges. But a huge number of species have coinciding (overlapping) or overlapping ranges. In addition, there are species that do not have clear distribution boundaries, as well as cosmopolitan species that live on vast expanses of land | land or ocean. Cosmopolitans are some inhabitants of inland waters - rivers and freshwater lakes (species of pondweed, duckweed, reed). An extensive set of cosmopolitans is found among weeds and garbage plants, synanthropic animals (species that live next to humans or his dwelling) - a bed bug, a red cockroach, a house fly, as well as a medicinal dandelion, a field yarutka, a shepherd's purse, etc.

There are also species that have a broken range. So, for example, linden grows in Europe, is found in the Kuznetsk Alatau and the Krasnoyarsk Territory. The blue magpie | magpie has two parts of its range - Western European and East Siberian. Due to these circumstances, the geographical criterion, like others, is not absolute.

Biochemical criterion allows you to distinguish species by biochemical parameters (composition and structure of certain proteins, nucleic acids and other substances). It is known that the synthesis of certain macromolecular substances is inherent only in certain groups of species. For example, according to the ability to form and accumulate alkaloids, plant species differ within the families of Solanaceae, Compositae, Liliaceae, and Orchids. Or, for example, for two species of butterflies from the genus Amata, the diagnostic feature is the presence of two enzymes - phosphoglucomutase and esterase-5. However, this criterion is not widely used - it is time-consuming and far from universal. There is significant intraspecific variability in almost all biochemical parameters up to the sequence of amino acids in protein molecules and nucleotides in individual DNA regions.

Thus, none of the criteria alone can serve to determine the species. It is possible to characterize a species only by their totality.

View (lat. species) is a taxonomic, systematic unit, a group of individuals with common morphophysiological, biochemical and behavioral characteristics, capable of interbreeding, producing fertile offspring in a number of generations, regularly distributed within a certain range and similarly changing under the influence of environmental factors. A species is a really existing genetically indivisible unit of the living world, the main structural unit in the system of organisms, a qualitative stage in the evolution of life.

For a long time it was believed that any species is a closed genetic system, that is, there is no exchange of genes between the gene pools of two species. This statement is true for most species, but there are exceptions to it. So, for example, lions and tigers can have common offspring (ligers and tigers), the females of which are fertile - they can give birth both from tigers and lions. Many other species are also interbred in captivity, which do not naturally interbreed due to geographic or reproductive isolation. Crossing (hybridization) between different species can also occur in natural conditions, especially in the case of anthropogenic disturbances of the habitat that violate the ecological mechanisms of isolation. Especially often plants hybridize in nature. A noticeable percentage of species of higher plants is of hybrid origin - they were formed during hybridization as a result of partial or complete merging of parental species.

Basic view criteria

1. Morphological criterion of the species. It is based on the existence of morphological features characteristic of one species, but absent in other species.

For example: in an ordinary viper, the nostril is located in the center of the nasal shield, and in all other vipers (nosed, Asia Minor, steppe, Caucasian, viper) the nostril is shifted to the edge of the nasal shield.
At the same time, there are significant individual morphological differences within species. For example, the common viper is represented by a variety of color forms (black, gray, bluish, greenish, reddish and other shades). These features cannot be used to distinguish species.

2. geographical criterion. It is based on the fact that each species occupies a certain territory (or water area) - a geographical area. For example, in Europe, some species of the malarial mosquito (genus Anopheles) inhabit the Mediterranean, others - the mountains of Europe, Northern Europe, Southern Europe.

However, the geographical criterion is not always applicable. The ranges of different species may overlap, and then one species smoothly passes into another. In this case, a chain of vicarious species (superspecies, or series) is formed, the boundaries between which can often be established only through special studies (for example, the herring gull, the black-backed gull, the western gull, the California gull).

3. ecological criterion. Based on the fact that two species cannot occupy the same ecological niche. Therefore, each species is characterized by its own relationship with the environment.

However, within the same species, different individuals can occupy different ecological niches. Groups of such individuals are called ecotypes. For example, one ecotype of Scotch pine inhabits swamps (marsh pine), another - sand dunes, the third - leveled areas of forest terraces.

A set of ecotypes that form a single genetic system (for example, capable of interbreeding with each other to form full-fledged offspring) is often called an ecospecies.

4. Molecular genetic criterion. Based on the degree of similarity and difference in nucleotide sequences in nucleic acids. As a rule, "non-coding" DNA sequences (molecular genetic markers) are used to assess the degree of similarity or difference. However, DNA polymorphism exists within the same species, and different species can be characterized by similar sequences.

5. Physiological and biochemical criterion. It is based on the fact that different species can differ in the amino acid composition of proteins. At the same time, protein polymorphism exists within a species (for example, intraspecific variability of many enzymes), and different species can have similar proteins.

6. Cytogenetic (karyotypic) criterion. It is based on the fact that each species is characterized by a certain karyotype - the number and shape of metaphase chromosomes. For example, all hard wheats have 28 chromosomes in the diploid set, and all soft wheats have 42 chromosomes. However, different species can have very similar karyotypes: for example, most species of the cat family have 2n=38. At the same time, chromosomal polymorphism can be observed within the same species. For example, in elks of Eurasian subspecies 2n=68, and in elks of North American species 2n=70 (in the karyotype of North American elks there are 2 less metacentrics and 4 more acrocentrics). Some species have chromosome races, for example, in a black rat - 42 chromosome (Asia, Mauritius), 40 chromosome (Ceylon) and 38 chromosome (Oceania).

7. reproductive criterion. It is based on the fact that individuals of the same species can interbreed with each other with the formation of fertile offspring similar to their parents, and individuals of different species living together do not interbreed with each other, or their offspring are sterile.

However, it is known that interspecific hybridization is often common in nature: in many plants (for example, willows), a number of fish species, amphibians, birds and mammals (for example, a wolf and a dog). At the same time, within the same species, there may be groupings that are reproductively isolated from each other.

8. ethological criterion. Associated with interspecies differences in behavior in animals. In birds, song analysis is widely used for species recognition. By the nature of the sounds produced, different types of insects differ. Different types of North American fireflies differ in the frequency and color of light flashes.

9. Historical (evolutionary) criterion. Based on the study of the history of a group of closely related species. This criterion is complex in nature, since it includes a comparative analysis of modern species ranges (geographical criterion), a comparative analysis of genomes (molecular genetic criterion), a comparative analysis of cytogenomes (cytogenetic criterion), and others.

None of the considered species criteria is the main or the most important one. For a clear separation of species, they must be carefully studied according to all criteria.

Due to unequal environmental conditions, individuals of the same species within the range break up into smaller units - populations. In reality, a species exists precisely in the form of populations.

Species are monotypic - with a weakly differentiated internal structure, they are characteristic of endemics. Polytypic species are characterized by a complex intraspecific structure.

Within species, subspecies can be distinguished - geographically or ecologically isolated parts of a species, individuals of which, under the influence of environmental factors, in the process of evolution have acquired stable morphophysiological features that distinguish them from other parts of this species. In nature, individuals of different subspecies of the same species can freely interbreed and produce fertile offspring.

species name

The scientific name of a species is binomial, that is, it consists of two words: the name of the genus to which the given species belongs, and the second word, called the species epithet in botany, and the species name in zoology. The first word is a singular noun; the second is either an adjective in the nominative case, agreed in gender (masculine, feminine or neuter) with a generic name, or a noun in the genitive case. The first word is capitalized, the second is lowercase.

Petasites fragrans- the scientific name of a species of flowering plants from the genus Butterbur ( Petasites) (the Russian name of the species is Fragrant Butterbur). The adjective is used as a specific epithet Fragrans("fragrant").
Petasites fominii- the scientific name of another species from the same genus (Russian name - Fomin Butterbur). The Latinized surname (in the genitive case) of the botanist Alexander Vasilyevich Fomin (1869-1935), a researcher of the flora of the Caucasus, was used as a specific epithet.

Sometimes entries are also used to designate indeterminate taxa at species rank:

Petasites sp.- the entry indicates that the taxon at the rank of species, belonging to the genus, is meant Petasites.
Petasites spp.- entry means that all taxa in the rank of species included in the genus are meant Petasites(or all other taxa in the rank of species included in the genus Petasites, but not included in any given list of such taxa).