What is the main criterion of the species. Type, type criteria. Morphological criterion of the species

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 set of animals.

In this case, only hybrids can be added to the exceptions. They are one biological (see 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).

To date, the 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, 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, 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 biological species were 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 biological species of plants 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

It is customary to call birds a class of vertebrates, a characteristic feature of which is a feather cover. Previously, there were species that were born wingless. However, they died out long ago, and kiwis are considered their descendants.

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

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 the 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 able to have 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 ago, human life expectancy was about 20 years, and the population did not exceed 500 thousand years.

signs

Any characteristic of a biological species begins with the presentation of signs of belonging to a certain population of individuals. There are several such 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 separate the various chemical properties and functions of individuals.
• Geographical. The sign indicates where a particular 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 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 features are generally accepted and basic. However, in addition to them, there are others: the 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 in one area are unevenly distributed. 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.

Species criteria: morphological

Biological species have common features that are manifested in appearance. It allows you to combine 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 sufficiently competent 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. Otherwise, there will be chaos.

Cytogenetic and molecular biological features

To describe this criterion, it is necessary to recall 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 populations differ from each other. The common one has 46 chromosomes, the Eastern European and Kyrgyz - 54 (they differ in the structure of the structural unit), the Transcaspian - 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.

It also occurs due to the different structures of the genital organs, size and color. 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.

Examples include Petasites fragrans or Petasites fominii. As you can see, the first word is always written with an uppercase letter, and the second - with a lowercase letter. The names are translated into Russian as "fragrant butterbur" and "Fomin's butterbur", respectively.

Species variability

Any biological species is capable of genetic change. It can persecute both the entire population and be individual. There are also modifications. 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. does not affect further offspring in any way, since it does not affect the genes and chromosome set. The problem arises under 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. 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 no problems for existence will arise.

The set of properties and common features inherent in one species is called the species criterion. Typically, six to ten species definition criteria are used.

Systematization

A species is a systematic or taxonomic unit that has a common characteristic and unites a group of living organisms on its basis. To isolate a biological group into one species, one should take into account a number of features associated not only with distinctive external features, but also with living conditions, behavior, distribution, etc.

The concept of "species" was used to group outwardly similar animals into groups. By the end of the 17th century, a lot of information about species diversity had accumulated, and the classification system required revision.

Carl Linnaeus in the 18th century united species into genera, and genera into orders and classes. He proposed a binary nomenclature of designations, which helped to significantly shorten the names of species. According to Linnaeus, the names began to consist of two words - the names of the genus and the species.

Rice. 1. Carl Linnaeus.

Linnaeus was able to systematize species diversity, but he himself erroneously distributed animals by species, relying mainly on external data. For example, he attributed the male and female ducks to different species. Nevertheless, Linnaeus made a huge contribution to the study of species diversity:

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• classified plants by gender (dioecious, monoecious, polyecious);
• identified six classes in the animal kingdom;
• attributed man to the class of primates;
• described about 6000 animals;
• He was the first to conduct experiments on plant hybridization.

Later, the biological concept of the species appeared, confirming that the classification by species is natural, genetically determined, and not artificial, created by people for the convenience of systematization. In fact, the species is an indivisible unit of the biosphere.

Despite the possibilities of modern science, many species have not yet been described. As of 2011, about 1.7 million species have been described. At the same time, there are 8.7 million species of plants and animals in the world.

Criteria

According to the criteria, it is possible to determine whether individuals belong to the same or to different species. First of all, the morphological criterion of the species is distinguished, i.e. representatives of different species should differ in external and internal structure.

However, often this criterion is not enough to distinguish a group of living organisms into a separate species. Individuals may differ in behavior, lifestyle, genetics, so it is important to take into account a set of criteria and not draw conclusions based on one trait.

Rice. 2. Morphological similarity of barbel species.

The table “Criteria of species” describes the most important criteria by which a species can be recognized.

None of the criteria is absolute and has exceptions to the rules:

• outwardly dissimilar species have the same set of chromosomes (cabbage and radish - 18 each), while mutations can be observed within the species and populations with a different set of chromosomes can be found;
• black rats (twin species) are morphologically identical, but genetically they are not, and, therefore, cannot produce offspring;
• in some cases, individuals of different species interbreed (lions and tigers);
• ranges often intersect or are broken (the Western European and East Siberian range of the magpie).

Hybridization is one of the levers of evolution. However, for successful crossing and obtaining fertile offspring, many criteria must match - genetics, biochemistry, physiology. Otherwise, the offspring will not be viable.

Rice. 3. Liger - a hybrid of a lion and a tigress.

What have we learned?

From the 11th grade biology lesson, we learned about the concept of a species and the criteria for its definition, considered nine main criteria with examples given. The criteria should be considered together. Only if several criteria are met can similar organisms be combined into a species.

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The question of species and species criteria occupies a central place in the theory of evolution and is the subject of numerous studies.research in the field of systematics, zoology, botany and otherSciences. And this is understandable: a clear understanding of the essencespecies is necessary to elucidate the mechanisms of evolutionary process.

A strict generally accepted definition of the species has not yet been developed.nerd. In the biological encyclopedic dictionary, wewe go to the following definition of the form:

“A species is a set of populations of individuals capable of interbreedingwith the formation of fertile offspring inhabiting a certainarea, which have a number of common morphophysiological signs and remote from other similar groups of individuals in practiceby the complete absence of hybrid forms.

Compare this definition with the one in your textbook.(textbook by A.A. Kamensky, § 4.1, p. 134).

Let us explain the concepts that occur. in the view definition:

area- the area of ​​distribution of a given species or population in nature.

population(from lat. “Pop uius " - people, population) - totalthe number of individuals of the same species with a common gene pool and occupationcovering a certain territory - an area.

gene pool- the totality of genes that individuals haveof this population.

Consider the history of the development of views on the species in biology.

The concept of species was first introduced into science by an English botanist John Ray inXVII century. Foundational work on the species problemwas written by a Swedish naturalist and naturalistCarl Linnaeus in XVIII centuryin which he proposed the firstscientific definition of the species, clarified its criteria.

K. Linnaeus believed that the species is a unigreasy, really existing unit of living matter, morphologically homogeneous and unchanging . All individuals of the species, according to the scientist, have a typical morphological appearance, and variations are random deviations. , the result of an imperfect implementation of the idea of ​​the form (a kind of deformity). Scientistbelieved that species are unchanging, nature is unchanging. The idea is unchangedof nature rested on the concept of creationism, according towhich all things were created by God. Applied to biologyLinnaeus expressed this concept in his famous formulamule “There are as many kinds as there are different forms that the Infinite creature".

Another concept belongs Tom Baptiste Lamarck- ledto whom the French naturalist. According to his concept, the views are real not exist, is a purely speculative concept invented forin order to make it easier to consider a larger number ofindividuals, because, according to Lamarck, “in nature there is noanything but individuals. Individual variability is continuous, therefore, the boundary between species can be drawn here and there - where it is more convenient.

The third concept was prepared in the first quarter XIX century. She was justified Charles Darwin and subsequent biologistmi. According to this concept, species have an independent reality. Viewheterogeneous, is a system of subordinate units. Withamong them, the basic elementary unit is the population. Species, by Darwin, change, they are relatively constant and areultatum of evolutionary development .

Thus, the concept of "species" has a long history of formation in biological science.

Sometimes the most experienced biologists are at a dead end, determiningwhether these individuals belong to the same species or not . Why is that happens, are there precise and strict criteria thatcould resolve all doubts?

Species criteria are traits by which one species differs.comes from another. They are also isolation mechanisms.interbreeding, independence, independently hundreds of species.

We know that one of the main features of biological matter on our planet is discreteness. It's in expressed in the fact that it is represented by separate species, notinterbreeding with each other, isolated from each other gogo.

The existence of a species is ensured by its genetic unity.(individuals of the species are able to interbreed and produce viable fertile offspring) and its genetic independence (impossiblethe possibility of interbreeding with individuals of another species, not viablestability or sterility of hybrids).

The genetic independence of the species is determined by the totalthe intensity of its characteristic features: morphological, physiological, biochemical, genetic, lifestyle features, behavior, geographical distribution, etc. This is Crete series of the species.

View criteria

Morphological criterion

Morphological criterion is the most convenient and noticeable, thereforeand is now widely used in the taxonomy of plants and animals.

We can easily distinguish by the size and color of the plumage of a largespotted woodpecker from green woodpecker, lesser spotted woodpecker and yellow(black woodpecker), great tit from crested, long-tailed, blueand chickadees, meadow clover from creeping and lupine, etc.

Despite the convenience, this criterion does not always “work”. You can’t use it to distinguish between twin species, practicallymorphologically different. There are many such species among malarialmosquitoes, fruit flies, whitefish. Even birds have 5% of twin species, andThere are 17 of them in one row of North American crickets.

The use of morphological criteria alone canlead to erroneous conclusions. So, K. Linnaeus in particularexternal structure attributed the male and female mallard ducks to different species. Siberian hunters identified five variations based on the color of fox fur: gray foxes, moths, crosses, black-brown and black. In England, 70 species of butterflies, along with individuals with a light color, also have themes.nye morphs, the number of which in populations began to increase inconnection with forest pollution. Polymorphism is a widespreadphenomenon. It occurs in all species. It also affects those features by which species differ. In lumberjack beetles, for example, in barbeled flowersexact, found in late spring on a bathing suit, in addition to tiIn the peak form, up to 100 color aberrations occur in populations. In the days of Linnaeus, the morphological criterion was the main one, sincewaist that there is one typical form for the species.

Now that it is established that a species can have many forms, such asthe logical concept of species is discarded and the morphological criterion is notalways satisfies scientists. However, it must be recognized that this criterionis very convenient for systematizing species, and in most determinants of animals and plants it plays a major role.

Physiological criterion

Physiological features of various types of plants and bellynyh are often a factor that ensures their genetic selfvalue. For example, in many fruit flies, the sperm of individuals of a foreign speciesYes, it causes an immunological reaction in the female genital tract, which leads to the death of spermatozoa. Hybridization of various species andsubspecies of goats often leads to a violation of the periodicity of the fetuswearing - the offspring appears in winter, which leads to his death. Crossbreedsthe study of different subspecies of roe deer, for example, Siberian and European,sometimes leads to the death of females and offspring due to large size fetus.

Biochemical criterion

Interest in this criterion has emerged in recent decades in connection withdevelopment of biochemical research. It is not widely used, since there are no specific substances characteristiconly for one species and, in addition, it is very laborious and far not universal. However, they can be used in cases wherewhen other criteria do not work. For example, for two twin speciesbutterflies from the genus Amata (A. p h e g ea and A. g ugazzii ) diagnosticand signs are two enzymes - phosphoglucomutase and esterase-5, allowing even identify hybrids of these two species. Recentlywidely used comparative study of the composition of DNK in practical taxonomy of microbes. The study of the composition of DNA allowed to revise the phylogenetic system of various groups microorganisms. The developed methods make it possible to compare the compositionDNA in bacteria preserved in the depths of the earth and now livingforms. For example, a comparison was made of the composition of DNA in a lyingabout 200 million years in the thickness of salts of the Paleozoic bacterium pseudosalt-loving monads and in living pseudomonads. The composition of their DNA turned out to be identical, and biochemical properties are similar.

Cytological criterion

The development of cytological methods has allowed scientists to investigate theRmu and the number of chromosomes in many species of animals and plants. A new direction has appeared - karyosystematics, which has introduced somecorrections and clarifications to the phylogenetic system built on the basis of morphological criteria. In some cases, the number of chromosomes servescharacteristic feature of the species. Karyological analysis allowed, for example, to streamline the taxonomy of wild mountain sheep, whichry different researchers identified from 1 to 17 species. The analysis showedthe presence of three karyotypes: 54 chromosome - in mouflons, 56romosome - in argali and argali and 58-chromosome - in the inhabitantsmountains of Central Asia - urials.

However, this criterion is not universal. First, atmany different species have the same number of chromosomes and their shape is similar. Secondly, individuals with different numbers of chromosomes may occur within the same species. These are the so-called chromosomal and genomicpolymorphism. For example, goat willow has a diploid - 38 and a tetraploid the new number of chromosomes is 76. In silver carp, there are populations with a setrum chromosomes 100, 150, 200, while their normal number is 50. In the rainbow trout, the number of chromosomes varies from 58 to 64, in the White Seadi meet individuals with 52 and 54 chromosomes. In Tajikistan on the siteonly 150 km long, zoologists discovered a population of mole voles with a set of chromosomes from 31 to 54. In gerbils from different habitats, the number of chromosomes is different: 40 - in Algerian gerbils skian populations, 52 in Israeli and 66 in Egyptian. To infusion current time, intraspecific chromosomal polymorphism was found in 5% of ctotal genetically studied species of mammals.

Sometimes this criterion is incorrectly interpreted as genetic. Undoubtedly, the number and shape of chromosomes is an important feature that prevents crossbreedingof individuals of different species. However, this is rather a cytomorphologicalcriterion, since we are talking about intracellular morphology: the numberand the shape of chromosomes, and not about the set and structure of genes.

E tological criterion

For some animal species, a mechanism that preventsbaptism and leveling the differences between them are especiallybennosti their behavior, especially during the mating season. Partner recognition own species and rejection of courtship attempts by males of another speciesbased on specific stimuli - visual, auditorychemical, tactile, mechanical, etc.

In the widespread genus warblers, different species are very similarlive on top of each other morphologically, in nature they cannot be distinguished either by color or by size. But they all differ very well in song and by habits. The song of the willow warbler is complex, similar to the song of the chaffinch, only without his final knee, and the song of the chiffchaff is aboutstenky monotonous whistles. Numerous twin species of ameRican fireflies of the genus P hotinus were first identified bydifferences in their light signals. Male fireflies in flight flashes of light, the frequency, duration and alternation of whichspecific to each species. well known but that a number of species of orthoptera and homopterans living within,of the same biotope and breeding synchronously, differ onlythe nature of their calling signals. Such double species with acousticreproductive isolation are found, for example, in crickets, skating fillies, cicadas and other insects. Two closely related species of Americantoads also do not interbreed because of differences in the call of males.

Differences in demonstrative behavior often play a decisive role in reproductive isolation. For example, related species of Drosophila flies fromdiffer in the specifics of the ritual of courtship (according to the nature of the vibrationwings, leg trembling, whirling, tactile contacts). Two closespecies - herring gull and klusha have differences in the degree of pronouncedhundreds of demonstrative poses, and seven species of lizards of the genus S se1horns s differ in the degree of raising the head when courting sexual partners.

Environmental criterion

Behavioral features are sometimes closely related to the ecological specifics of the species, for example, to the peculiarities of nest construction. Three species of our common tits nest in hollows of deciduous trees, mainly birches. The great tit in the Urals usually chooses deep a hollow in the lower part of a birch or alder trunk, formed in a re as a result of rotting of the knot and adjacent wood. This hollow is inaccessible neither to woodpeckers, nor to ravens, nor to predatory mammals. Tit moskovka populates frost cracks in the trunks of birch and alder. Hathe egg prefers to build a hollow itself, plucking cavities into rottenor old birch and alder trunks, and without this time-consuming procedure, she will not lay eggs.

Features of the lifestyle inherent in each species determineits position, its role in the biogeocenosis, that is, its ecologicalniche. Even the closest species, as a rule, occupy different econiches, that is, they differ in at least one or two ecological signs.

Thus, the econiches of all our species of woodpeckers differ in the nature of their diet. Great spotted woodpecker feeds on larch seeds in winter tsy and pines, crushing cones in their "forges". black woodpeckerzhelna extracts barbel larvae and gold beetles from under the bark and from woodfir, and the small spotted woodpecker hammers soft alder wood or extracts nase lumps from the stems of herbaceous plants.

Each of the 14 species of Darwin's finches (named afterC. Darwin, who first paid attention to them), living on the Galapagos islands, has its own specific eco-niche, which differs from others primarily in the nature of food and ways of obtaining it.

Neither the ecological nor the ethological crite discussed aboverii are not universal. Very often individuals of the same species, but oncepopulations differ in a number of lifestyle featuresand behaviour. And vice versa, different species, even very distant ones, in the systemchemically, may have similar ethological characteristicsor play the same role in the community (for example, the role of a herbivorous mammal and insects, say, such as locusts, are quite comparable).

Geographic criterion

This criterion, along with the ecological one, takes the second (after the morphological) place in most determinants. When determining many species of plants, insects, birds, mammals and othergroups of organisms whose distribution is well studiedThe distribution of the range plays a significant role. In subspecies, the ranges, as a rule, do not coincide, which ensures their reproductive isolation and, in fact,, their existence as independent subspecies. many kindsoccupy different ranges (such species are called allopatric and). But a vast number of species have overlapping or overlappingexpanding ranges (sympatric species). In addition, there are typeshaving clear boundaries of distribution, as well as braid speciesmopolitans living on vast expanses of land or ocean. ATdue to these circumstances, the geographical criterion cannot be universal.

Genetic criterion

Genetic unity of the species and, accordingly, genetic isolationit from other species - the main criterion of the species, the main speciesa sign due to a complex of features of the structure and lifeactivities of this species. Genetic compatibilitybridge, similarity of morphological, physiological, cytologicaland other signs, the same behavior, living together - all thiso creates the necessary conditions for successful reproduction and reproductionspecies production. At the same time, all these traits provide geneticisolation of a species from other similar species. For example, oncelychia in the song of thrushes, warblers, warblers, finches and finches, deafand common cuckoo prevent the formation of mixed pairs,despite the similarity of their coloration and ecology (hybrids are almost never found in birds with a specific song). Even in those cases I, when, despite isolation barriers, interbreeding occurredthe formation of individuals of different species, a hybrid population, as a rule, does not arise, since a number of post-populationisolation mechanisms. The most important of them is the death of male gametes (genetical incompatibility), death of zygotes, non-viability of thereeds, their sterility, finally, the inability to find a sexualpartner and produce viable fertile offspring. We know thatEach species has its own set of specific features. An interspecific hybrid will have characters intermediate betweenfeatures of the two original parental forms. His song, for example will not be understood by either a chaffinch or a finch if it is a hybrid of these species, and he will not find a sexual partner. In such a hybrid,the formation of gametes, the finch chromosomes contained in its cells “do notfind the chromosomes of the finch and, not finding a homologous partner, do notconjugate. As a result, gametes with a disturbed set are formed.chromosomes, which are usually not viable. And as a resultThis hybrid will be sterile.

The raven is distributed almost throughout the northern hemisphere: it occursalmost throughout Europe, Asia, excluding Southeast, in NorthAfrica and North America. Everywhere he leads a settled way of life. Inhabits forests, deserts and mountains. In treeless areas keeps atrocks, coastal cliffs of river valleys. Mating and mating gamesin the south of the country are celebrated in the first half of February, in the north - inMarch. Couples are constant. Nests are usually placed on the tops of tall trees. In clutch from 3 to 7, more often 4-6, eggs are bluish-green in color. ki with dark markings.

Raven is an omnivorous bird. His main food is carrion, which he oftenfinds everything in landfills and slaughterhouses. Eating carrion, he performslike a sanitary bird. It also feeds on rodents, eggs,and chicks, fish, various invertebrates, and placesmi and grains of cereals.

The crow in general physique resembles a crow, but significantlysmaller than it: weighs from 460 to 690 g.

The described species is interesting in that, according to the color of the plumage, it breaks upinto two groups: gray and black. The hooded crow is well knownnew two-tone color: head, throat, wings, tail, beak and legs are black, the rest of the plumage is gray. Black Crow is all black, with a metallic blue and purple sheen.

Each of these groups has a local distribution. The gray crow is widespread in Europe, Western Asia, the black crow is widespread in Central and Western Europe, on the one hand, and in Central and Eastern Asia and North America, on the other.

The crow inhabits the edges and outskirts of forests, gardens, groves, thickets of river valleys, less often rocks and slopes of coastal cliffs. It is partly sedentary, partly migratory bird.

In early March, in the southern parts of the country and in April-May in the northern and eastern parts, egg laying begins. The clutch usually contains 4-5 pale green, bluish-green or partially green eggs with dark spots and speckles. The crow is an omnivorous bird. From animals, she eats various invertebrates - beetles, ants, mollusks, as well as rodents, lizards, frogs and fish. From plants, it pecks grains of cultivated cereals, seeds of spruce, field bindweed, bird buckwheat, etc. In winter, it feeds mainly on garbage.

White Hare and European Hare

The genus of hares proper, which includes the hare and hare, as well as another 28 species , quite numerous. The most famous hares in Russia are hare and hare. White hare can be found on the territory from the coast of the Arctic Ocean to the southern border of the forest zone, in Siberia - to the borders with Kazakhstannom, China and Mongolia, and in the Far East - from Chukotka to and North Korea. The hare is also common in the forests of Europe, as well as in the east of Northern America. Rusak lives on the territory of European Russia from Kareliasouth of the Arkhangelsk region to the southern borders of the country, in Ukraine and in the Zakavcasier. But in Siberia, this hare lives only in the south and west of Lake Baikal.

Belyak got its name due to snow-white winter fur. Only the tips of his ears remain black all year round. Rusak, in some northern areas, also brightens greatly by winter, but it never happens to be snow-white. And in the south it does not change color at all.

The hare is more adapted to life in open landscapes, since it is larger than the white hare, and it runs better. At short distances, this hare can developspeed up to 50 km/h. The hare's paws are wide, with dense pubescence to fall less into loose forest drifts. And the hare already has paws, after all, in open places, snow, as a rule, is hard, packed, “trodden down by the wind.”

The body length of the hare is 45-75 cm, weight - 2.5-5.5 kg. The ears are shorter than those of the hare. The body length of the hare is 50-70 cm, weight up to 5 (sometimes 7) kg.

breed hares usually two, and in the south three or even four times a year. Wu harebelyakovs in the output can be two, three five, seven hares, and the hare- usually only one or two hares. Browns begin to taste grass two weeks after birth, and whites even faster - a week later.

1. Biological species and its criteria.

All life on the planet is represented by separate species.

A species is a historically established set of individuals that have a hereditary similarity in morphological, physiological and biochemical features; able to freely interbreed with each other and produce fertile offspring; adapted to certain environmental conditions and occupying a certain area.

Each type of organism can be described by a set of characteristic features and properties, which are called features of the species. Features of a species that distinguish one species from another are called type criteria.

The most commonly used general view criteria are: morphological, physiological, genetic, biochemical, geographical and ecological.

Morphological criterion - based on the external and internal similarity of individuals of the same species.

The morphological criterion is the most convenient and is therefore widely used in species taxonomy.

However, the morphological criterion is insufficient to determine the difference sibling species with significant morphological similarity.

Twin species practically do not differ in appearance, however, individuals of such species do not interbreed.

Species-twins are quite common in nature. About 5% of all species of insects, birds, fish, etc. have twin species:

- black rats have two twin species;

- the malarial mosquito has six twin species.

The use of a morphological criterion is also difficult in cases where individuals of the same species differ sharply from each other in appearance, the so-called polymorphic species.

The simplest example of polymorphism is sexual dimorphism, when there are morphological differences between males and females of the same species.

It is difficult to use the morphological criterion in the diagnosis of domestic animal species. Breeds bred by humans can differ significantly from each other, remaining within the same species (breeds of cats, dogs, pigeons).

Thus, the morphological criterion is insufficient to determine the species belonging of individuals.

The physiological criterion characterizes the similarity of life processes in individuals of the same species, primarily the similarity of reproduction.

Between individuals of different species there is a physiological isolation, which is manifested in the fact that individuals of different species almost never interbreed with each other. This is due to differences in the structure of the reproductive apparatus, the timing and places of reproduction, in the rituals of behavior during mating, etc.

If interspecific crossing does occur, then the result is interspecific hybrids that are characterized by reduced viability or are infertile and do not produce offspring:

For example, a hybrid of a horse and a donkey is known - a mule, which is quite viable, but barren.

However, in nature there are such species that can interbreed with each other and produce fertile offspring. (for example, some species of canaries, finches, poplars, willows, etc.).

Consequently, the physiological criterion is insufficient to characterize the species.

A genetic criterion is a set of chromosomes characteristic of each species, a strictly defined number, size and shape.

Individuals of different species cannot interbreed, as they have different sets of chromosomes, differ in number, size and shape:

- for example, two closely related species of black rats differ in the number of chromosomes (one species has 38 chromosomes, and the other 48) and therefore do not interbreed.

However, this criterion is not universal:

- first, in many different species, the number of chromosomes can be the same (for example, many species of the legume family have 22 chromosomes each);

- secondly, within the same species, individuals with a different number of chromosomes can be found, which is the result of mutations (for example, in silver carp there are populations with a set of chromosomes 100, 150, 200, while their normal number is 50).

Thus, on the basis of a genetic criterion, it is also impossible to reliably determine the belonging of individuals to a particular species.

The biochemical criterion makes it possible to distinguish species according to biochemical parameters (the composition and structure of certain proteins, nucleic acids, and other substances).

It is known that the synthesis of certain macromolecular substances is characteristic only of certain species ( for example, many plant species differ in their ability to form and accumulate certain alkaloids).

However, there is significant intraspecific variability in almost all biochemical parameters, up to the sequence of amino acids in protein and nucleic acid molecules.

Therefore, the biochemical criterion is also not universal. In addition, it is not widely used, as it is very laborious.

The geographical criterion is based on the fact that each species occupies a certain territory or water area.

In other words, each species is characterized by a specific geographical area.

Many species occupy different ranges, but most species have overlapping ranges.

There are species that do not have a specific geographical range, i.e. living on vast expanses of land or ocean, the so-called cosmopolitan species :

- some inhabitants of inland waters - rivers and freshwater lakes (many species of fish, reeds);

- Cosmopolitans also include medicinal dandelion, shepherd's purse, etc.;

- cosmopolitans are found among synanthropic animals - species that live near a person or his dwelling (lice, bedbugs, cockroaches, flies, rats, mice, etc.);

- Cosmopolitans also include indoor and cultivated plants, weeds, pets that are under human care.

In addition, there are species that do not have clear distribution boundaries or have a broken geographical range.

Due to these circumstances, the geographical criterion, like others, is not absolute.

The ecological criterion is based on the fact that each species can exist only under certain conditions, fulfilling its functional role in a particular biogeocenosis.

In other words:

Each species occupies a certain ecological niche in a complex system of ecological relationships with other organisms and factors of inanimate nature.

An ecological niche is a set of all environmental factors and conditions within which a species can exist in nature.

It includes the whole complex of abiotic and biotic environmental factors necessary for the organism to live, and is determined by its morphological fitness, physiological reactions and behavior.

The classic definition of an ecological niche was given by the American ecologist J. Hutchinson (1957).

According to the concept formulated by him, an ecological niche is a part of an imaginary multidimensional space (hypervolume), individual dimensions of which correspond to the factors necessary for the normal existence of a species (Fig. 1).

two-dimensional niche three-dimensional niche

Rice. 1. Ecological niche model according to Hutchinson

(F 1, F 2, F 3 - the intensity of various factors).

For example:

- for the existence of a terrestrial plant, a certain combination of temperature and importance is sufficient (two-dimensional niche);

- for a marine animal, temperature, salinity, oxygen concentration (three-dimensional niche) are necessary.

It is important to emphasize that the ecological niche is not just the physical space occupied by a species, but also its place in the community, determined by its ecological functions and its position relative to the abiotic conditions of existence.

According to the figurative expression of Y. Odum, an “ecological niche” is the “profession” of a species, its way of life, and “habitat” is its “address”. ”

For example, a mixed forest is a habitat for hundreds of species of plants and animals, but each of them has its own and only one "profession" - an ecological niche. Elk and squirrel have the same habitat, but their ecological niches are completely different.

Consequently, the ecological niche is not a spatial, but a functional category.

At the same time, it is important to realize that the ecological niche is not something that can be seen. An ecological niche is an abstract abstract concept.

An ecological niche defined only by the physiological characteristics of organisms is called fundamental and the one within which the species actually occurs in nature - implemented.

However, the ecological criterion is also insufficient to characterize the species.

Some different species in different habitats may occupy the same ecological niches:

- antelopes in the savannas of Africa, bison in the prairies of America, kangaroos in the savannas of Australia, marten in the European and sable in the Asian taiga lead the same way of life, have a similar type of nutrition, i.e. in different biogeocenoses they perform the same functions and occupy similar ecological niches.

It often happens the other way around - the same species in different habitats is characterized by different ecological niches. Most often this is due to the availability of food and the presence of competitors:

In addition, the same species in different periods of its development can occupy different ecological niches:

- so, the tadpole eats plant food, and the adult frog is a typical carnivore, so they are characterized by different ecological niches;

- migratory birds in connection with migrations are also characterized by different ecological niches in winter and summer;

- among algae there are species that function either as autotrophs or as heterotrophs. As a result, at certain periods of their lives, they occupy certain ecological niches.

Thus, none of these criteria can be used to determine whether an individual belongs to a particular species. It is possible to characterize a species only by the totality of all or most of the criteria.

Species criteria determine how pronounced the traits and properties that distinguish one species from another.

A species is considered to be a historically formed association of populations, where individuals are endowed with genetic conformity, morphological, physiological similarity, freedom of interbreeding and further reproduction, stay in a certain area in special living conditions.

Genetic (genetic-reproductive) criterion of the species

Genetic connection is the initial reason for the external similarity of organisms and the primary sign for combining into a separate set of individuals.

Individuals within the same species are characterized by a certain set of chromosomes, their quantitative value, size and external outlines.

The cytogenetic criterion is the most important feature of the species. Due to the different set of chromosomes, living organisms of different species adhere to a special isolation in the production of offspring and do not have the opportunity to interbreed.

The study of the shape and number of chromosomes is performed using the cytological method. The number of structural elements of the cell nucleus is a distinctive feature of the species.

Morphological criterion of the species

According to the morphological method, individuals of the same species are combined according to similar shape and structure. In appearance, black and white crows are classified as different species.

Morphological features are one of the main, but often not decisive. In nature, there are aggregates of organisms that have common external features, but do not interbreed. They are twin species.

An example is the varieties of mosquitoes, previously classified as malarial. They are distinguished by a dissimilar food base, referring individuals to different ecological niches.

Ecological criterion of the species

Participation in the individual habitat is a fundamental principle of the ecological criterion.

One type of mosquito feeds on the blood of mammals, the other - birds, the third - reptiles. However, some populations of insects serve as carriers of malaria, while others do not.

Accordingly, two different species cannot coexist within the same ecological niche, but different living organisms of the same species can be found in dissimilar habitats. Groups of these homogeneous populations are called ecotypes.

Physiological (physiological-biochemical) criterion of the species

The physiological criterion is manifested in connection with the peculiarities of the complex complex of the life activity of the organism and its individual systems. According to this classification, individuals are grouped according to the similarity of their reproductive processes.

Organisms outside of the same species are practically incapable of interbreeding or produce infertile offspring. But there are individual representatives that are capable of reproduction and give viable offspring.

Therefore, the division into species, based only on a physiological trait, is erroneous.

Geographic criterion of the species

The geographical criterion is based on the allocation of distribution sites for individuals in certain territorial areas. But often the ranges of different species overlap or break, which calls into question the absolute application of the method.

Behavioral criterion of species

The behavioral or ethological criterion characterizes interspecies differences in the behavior of individuals.

Bird songs or sounds made by insects are used to recognize certain types of animals. An important role is played by behavior during mating, reproduction and the nature of care for offspring.

View criteria - table for biology lessons with examples

Morphological features of representatives of flora and fauna

common wolf

The wolf genus consists of seven species and 17 subspecies belonging to the common or gray wolf (Canis lupus). The division into subspecies groups occurred due to different body proportions and hair color.

Morphological features:

• large sizes;
• external resemblance to a dog, differences in a more sloping frontal part, elongated paws, a lowered back part of the body, a straight tail and a special structure of the hairline;
• dark gray stripe along the ridge, crown of the head with dark markings, characteristic "mask" on the muzzle;
• the color is gray-brown, ocher-rusty and fawn, the roots and tips of the hair are dark, the middle is light tones.

The geography of habitat differs in the breadth of ranges. Exists in flocks from 2 to 40 animals. Differs in high social development. They make various sounds that facilitate communication between individuals.

The wolf belongs to typical predators, but plant foods are also present in the diet.

The wolf is a monogamous animal that lives in pairs from mating to maturation of the offspring. Mating games last from January to March. Sexual maturity in males occurs from 2 to 3 years, in females - by 2 years.

Cactus

The numerous cactus family has approximately 2800 species and is divided into 3 subfamilies:

1. Peyresky cacti include deciduous representatives;
2. Opuntias consist of flat cacti and are divided into 3 groups according to their shape;
3. Cereus include plants lacking leaves and glochidia.

Distinctive morphological features:

• the presence of an areola, represented by spines or hairs;
• the unique structure of the fruit and flower, which is the tissue of the stem.

Cactus are native to North and South America.

Amur tiger

The Amur tiger differs from other tigers in geographical and morphological features. The area is the Far East and the northern part of China.

External differences include:

• thick and long fur;
• fewer lanes.

What type criterion is the most accurate

The most clear boundaries between species groups can be determined using the genetic method.

But in nature, complete genetic isolation cannot exist, therefore, to identify the belonging of an organism to a certain species category, several different criteria must be used.

The most ancient species criterion

The oldest and most widespread method of describing new species is the morphological criterion, which systematizes individuals according to external similarity.

This method is also the least accurate due to the frequent significant difference between organisms of a certain species and the morphological similarity of various individuals.

Conclusion

Species criteria contribute to a deep study, analysis and the most accurate systematization of organisms. On Earth, there are more than a million described species and a large number of still unknown and unexplored.

The study of species features contributes to understanding the process of evolution on Earth.