What is a historical criterion. View criteria. The most ancient species criterion

View- a set of individuals with a hereditary similarity of morphological, physiological and biological features, freely interbreeding and producing offspring, to certain living conditions and occupying a certain area in nature.

Species are stable genetic systems, as in nature they are separated from each other by a number of barriers.

A species is one of the main forms of organization of living things. However, it is sometimes difficult to determine whether these individuals belong to the same species or not. Therefore, to decide whether individuals belong to this species, a number of criteria are used:

Morphological criterion- the main criterion based on external differences between animal or plant species. This criterion serves to distinguish organisms that are clearly distinguished by external or internal morphological characters. But it should be noted that very often there are very subtle differences between species, which can be revealed only with a long study of these organisms.

Geographic criterion- based on the fact that each species lives within a certain space (). The area is the geographical boundaries of the distribution of the species, the size, shape and location of which is different from the areas of other species. However, this criterion is also not universal enough for three reasons. Firstly, the ranges of many species coincide geographically, and secondly, there are cosmopolitan species for which the range is almost the entire planet (killer whale). Thirdly, in some rapidly spreading species (house sparrow, house fly, etc.), the range changes its boundaries so quickly that it cannot be determined.

Environmental criterion- assumes that each species is characterized by a certain type of food, habitat, timing, i.e. occupies a certain niche.
Ethological criterion - lies in the fact that the behavior of animals of some species differs from the behavior of others.

Genetic criterion- contains the main property of the species - its isolation from others. Animals and plants of different species almost never interbreed. Of course, a species cannot be completely isolated from the flow of genes from closely related species, but at the same time it maintains a constant genetic composition over a long time. The clearest boundaries between species are precisely from a genetic point of view.

Physiological and biochemical criterion- this criterion cannot serve as a reliable way to distinguish between species, since the main biochemical processes proceed in similar groups of organisms in the same way. And within each species there are a large number of adaptations to specific living conditions by changing the course of physiological and biochemical processes.
According to one of the criteria, it is impossible to accurately distinguish species from each other. It is possible to determine whether an individual belongs to a particular species only on the basis of a combination of all or most of the criteria. Individuals occupying a certain territory and freely interbreeding with each other are called a population.

population- a set of individuals of the same species occupying a certain territory and exchanging genetic material. The totality of the genes of all individuals in a population is called the gene pool of the population. In each generation, individual individuals contribute more or less to the total gene pool, depending on their adaptive value. The heterogeneity of the organisms included in the population creates the conditions for the action, therefore, the population is considered the smallest evolutionary unit, from which the transformation of the species begins -. The population, therefore, is a supra-organismal formula for the organization of life. The population is not a completely isolated group. Sometimes interbreeding occurs between individuals of different populations. If a population turns out to be completely geographically or ecologically isolated from others, then it can give rise to a new subspecies, and subsequently a species.

Each population of animals or plants consists of individuals of different sexes and different ages. The ratio of the number of these individuals may be different depending on the time of year, natural conditions. The size of a population is determined by the ratio of births and deaths of its constituent organisms. If for a sufficiently long time these indicators are equal, then the population size does not change. Environmental factors, interaction with other populations can change the size of the population.

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 exists, 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. Last timewidely 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.

In order to study the diversity of life, man needed to develop a classification system for organisms to divide them into groups. As you already know, the smallest structural unit in the taxonomy of living organisms is the species.

A species is a historically established set of individuals that are similar in morphological, physiological and biochemical characteristics, interbreed freely and produce fertile offspring, are adapted to certain environmental conditions and occupy a common territory in nature - an area.

In order to attribute individuals to the same or to different species, they are compared with each other according to a number of specific characteristic features - criteria.

View criteria

The set of characteristic features of the same type, in which individuals of the same species are similar, and individuals of different species differ from each other, is called the species criterion. In modern biology, the following main criteria for a species are distinguished: morphological, physiological, biochemical, genetic, ecological, geographical.

Morphological criterion reflects a set of characteristic features of the external structure. For example, clover species differ in the color of the inflorescences, the shape and color of the leaves. This criterion is relative. Within a species, individuals can differ markedly in structure. These differences depend on gender ( sexual dimorphism), stages of development, stages in the breeding cycle, environmental conditions, belonging to varieties or breeds.

For example, in the mallard, the male is brightly colored, and the female is dark brown; in the red deer, the males have antlers, while the females do not. In the cabbage white butterfly, the caterpillar differs from the adult in external signs. In the male thyroid fern, the sporophyte has leaves and roots, and the gametophyte is represented by a green plate with rhizoids. At the same time, some species are so similar in morphological features that they are called twin species. For example, some species of malarial mosquitoes, fruit flies, North American crickets do not differ in appearance, but do not interbreed.

Thus, on the basis of one morphological criterion, it is impossible to judge whether an individual belongs to one species or another.

Physiological criterion- a set of characteristic features of life processes (reproduction, digestion, excretion, etc.). One of the important features is the ability of individuals to interbreed. Individuals of different species cannot interbreed due to the incompatibility of germ cells, the mismatch of the genital organs. This criterion is relative, since individuals of the same species sometimes cannot interbreed. In Drosophila flies, the impossibility of mating may be due to differences in the structure of the reproductive apparatus. This leads to disruption of the reproduction processes. Conversely, there are known species whose representatives can interbreed with each other. For example, a horse and a donkey, representatives of some species of willows, poplars, hares, canaries. From this it follows that in order to determine the species affiliation of individuals, it is not enough to compare them only according to a physiological criterion.

Biochemical criterion reflects the characteristic chemical composition of the body and metabolism. This is the most unreliable criterion. There are no substances or biochemical reactions that are specific to a particular species. Individuals of the same species can vary significantly in these indicators. Whereas in individuals of different species, the synthesis of proteins and nucleic acids occurs in the same way. A number of biologically active substances play a similar role in the metabolism of different species. For example, chlorophyll in all green plants is involved in photosynthesis. This means that the determination of the species affiliation of individuals on the basis of one biochemical criterion is also impossible.

Genetic criterion characterized by a certain set of chromosomes, similar in size, shape and composition. This is the most reliable criterion, as it is the reproductive isolation factor that maintains the genetic integrity of the species. However, this criterion is not absolute. In individuals of the same species, the number, size, shape, and composition of chromosomes may differ as a result of genomic, chromosomal, and gene mutations. At the same time, when crossing some species, viable fertile interspecific hybrids sometimes appear. For example, a dog and a wolf, a poplar and a willow, a canary and a finch, when crossed, produce fertile offspring. Thus, the similarity according to this criterion is also not enough to classify individuals as one species.

Environmental criterion is a set of characteristic environmental factors necessary for the existence of a species. Each species can live in an environment where climatic conditions, soil features, topography and food sources correspond to its tolerance limits. But under the same environmental conditions, organisms of other species can also live. Human breeding of new breeds of animals and plant varieties has shown that individuals of the same species (wild and cultivated) can live in very different environmental conditions. This proves the relative nature of the ecological criterion. Therefore, there is a need to use other criteria when determining whether individuals belong to a particular species.

Geographic criterion characterizes the ability of individuals of one species to inhabit in nature a certain part of the earth's surface (range).

For example, Siberian larch is common in Siberia (Trans-Urals), and Dahurian larch - in Primorsky Krai (Far East), cloudberries - in the tundra, and blueberries - in the temperate zone.

This criterion indicates the confinement of the species to a particular habitat. But there are species that do not have clear boundaries of settlement, but live almost everywhere (lichens, bacteria). In some species, the range coincides with the range of humans. Such types are called synanthropic(house fly, bed bug, house mouse, gray rat). Different species may have overlapping habitats. Hence, this criterion is also relative. It cannot be used as the only one for determining the species of individuals.

Thus, none of the described criteria is absolute and universal. Therefore, when determining whether an individual belongs to a particular species, all its criteria should be taken into account.

The area of the species. The concept of endemics and cosmopolitans

According to the geographical criterion, each species in nature occupies a certain territory - an area.

area(from lat. area- area, space) - part of the earth's surface, within which individuals of a given species are distributed and go through a full cycle of their development.

The area may be continuous or intermittent, extensive or limited. Species that have a vast range within different continents are called cosmopolitan species(some types of protists, bacteria, fungi, lichens). When the distribution area is very narrow and is located within a small region, then the species inhabiting it is called endemic(from Greek. endemos- local).

For example, kangaroo, echidna and platypus live only in Australia. Ginkgo in natural conditions grows only in China, spiky rhododendron and Daurian lily - only in the Far East.

Species - a set of individuals that are similar in morphological, physiological and biochemical characteristics, interbreed freely and produce fertile offspring, are adapted to certain environmental conditions and occupy a common territory in nature - an area. Each species is characterized by the following criteria: morphological, physiological, biochemical, genetic, ecological, geographical. All of them are relative in nature, therefore, when determining the species affiliation of individuals, all possible criteria are used.

Superorganism systems. Evolution of the organic world

evolutionary doctrine

Basic concepts:

species, species criteria, population, systematics, classification, history of evolutionary ideas, synthetic theory of evolution, driving forces of evolution, forms of natural selection, population waves, genetic drift, artificial selection, types of struggle for existence, results of evolution, microevolution, speciation, isolation, fitness, relative nature of fitness, forms and directions of evolution, biological progress and regression, macroevolution, aromorphosis, idioadaptation, degeneration, evidence for evolution

There are about 2 million species of animals on Earth, more than 500 thousand species of plants, hundreds of thousands of species of fungi, microorganisms. A species is a collection of organisms that actually exists in nature.

View – This is a collection of individuals that are similar in structure, have a common origin, freely interbreed with each other and give fertile offspring. All individuals of the same species have the same karyotype - a set of chromosomes of a somatic cell (2n), similar behavior, occupy a certain territory - area (from Latin area - area, space). Carl Linnaeus (17th century) introduced the concept of "view".

A species is one of the main forms of organization of living things. Each type of living organisms can be described on the basis of a set of characteristic features, properties, which are called signs. Species features that distinguish one species from another are called species criteria.

View criteria - a set of characteristic features, properties and features by which one species differs from another. There are six general species criteria most commonly used: morphological, physiological, genetic, biochemical, geographical, and ecological. At the same time, none of the criteria is absolute; to determine the type, the presence of the maximum number of criteria is necessary.

Morphological criterion- description of external (morphological) features and internal (anatomical) structure 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 great tit from a crested one. By the appearance of the shoots and inflorescences, the size and arrangement of the leaves, the types of clover are easily distinguished: meadow and creeping. The morphological criterion is widely used in taxonomy. However, this criterion is not sufficient to distinguish between species that have significant morphological similarities. For example, in nature there are twin species that do not have noticeable morphological differences (black rats have two twin species - with a set of chromosomes 38 and 42, and the malarial mosquito used to be called six similar species, of which only one carries malaria).

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. At the same time, interbreeding is possible between certain types of living organisms; in this case, fertile hybrids can be formed (canaries, hares, poplars, willows, etc.)

Geographic criterion- each species occupies a certain territory - range. Many species occupy different ranges. But many species have coinciding (overlapping) or overlapping ranges, some have a broken range (for example, linden grows in Europe, is found in Kuznetsk Alatau and Krasnoyarsk Territory). In addition, there are species that do not have clear distribution boundaries, as well as cosmopolitan species that live on vast expanses of land or ocean. Cosmopolitans are some inhabitants of inland waters - rivers and freshwater lakes (duckweed, reed). There are cosmopolitans among weeds, synanthropic animals (species that live near a person 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. Thus, a geographical criterion, like others, is not absolute.

Environmental criterion is based on the fact that each species can exist only under certain conditions: each species occupies a certain 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. However, there are species that do not have a strict ecological criterion; synanthropic species are an example.

Genetic 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. For example, 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). Also, within the same species, individuals with a different number of chromosomes can be found (the result of genomic mutations): goat willow has a diploid (38) and tetraploid (76) number of chromosomes; 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 not always possible to determine whether individuals belong to a particular species.

Biochemical criterion is the composition and structure of certain proteins, nucleic acids and other substances. For example, the synthesis of certain macromolecular substances is inherent only in certain species: alkaloids are formed by plant species of the nightshade and lily families. But this criterion is not widely used - it is laborious and not always universal. There is a significant intraspecific variability in almost all biochemical parameters (sequence of amino acids in protein molecules and nucleotides in individual sections of DNA). At the same time, many biochemical features are conservative: some are found in all representatives of a given type or class.

Thus, none of the criteria separately can serve to determine the species: to determine the species, it is necessary to take into account the totality of all criteria. In addition to these features, scientists identify historical and ethological criteria.

Characteristics of the type criteria

View criteria	Criteria characteristics
Morphological	The similarity of the external (morphological) and internal (anatomical) structure of individuals of the same species.
Physiological	The similarity of all life processes, and, above all, reproduction. Representatives of different species, as a rule, do not interbreed with each other, or give sterile offspring.
Genetic	A characteristic set of chromosomes inherent only to this species, their structure, shape, size. Individuals of different species with an unequal set of chromosomes do not interbreed.
Biochemical	The ability to form species-specific proteins; similarity of chemical composition and chemical processes.
Ecological	The adaptability of individuals of a given species to certain environmental conditions is a set of environmental factors in which the species exists.
Geographical	A certain area, habitat and distribution in nature.
Historical	Origin and development of the species.
ethological	Certain specific features in the behavior of individuals: differences in mating songs, in mating behavior.

View- a set of individuals characterized by a common origin, having a hereditary similarity of morphological, physiological and biochemical characteristics, freely interbreeding and producing fertile offspring, adapted to existing living conditions and occupying a certain territory - area. All species are composed of populations, that is, a population is the structural unit of a species.

Populations – These are groups of organisms of the same species, relatively isolated from each other, with the ability to freely interbreed with each other and produce fertile offspring.

View - a set of individuals that have common morphophysiological features and are united by the ability to interbreed with each other, forming a system of populations that form a common area.

Populations are characterized by certain properties:

1) abundance - the total number of organisms in the population;

2) birth rate - the rate of population growth;

3) mortality - the rate of reduction in numbers as a result of the death of individuals;

4) age composition - the ratio of the number of individuals of different ages (the ratio of age groups);

5) sex ratio - based on the genetic definition of sex, the sex ratio in the population should be 1:1, the violation of this ratio leads to a decrease in the population size;

6) population dynamics - under the influence of various factors, periodic and non-periodic fluctuations in the number and size of the range are possible, which can affect the nature of crossings;

7) population density - the number of individuals per unit of space occupied by the population.

Populations do not exist in isolation: they interact with populations of other species, forming biotic communities.

Studying nature, scientists discovered and described previously unknown organisms, giving them names. At the same time, it often turned out that different scientists called the same organism differently. The more materials accumulated, the more difficulties appeared in using the accumulated knowledge. There was a need to bring all the diversity of living organisms into a single system. The branch of biology that deals with the description and classification of organisms is called taxonomy .

The first systems were artificial, as they were built on several arbitrarily taken signs. One of the classification systems for plants and animals was proposed by Carl Linnaeus (1707-1778). The merit of the scientist is not only in creating the system, but also in the fact that he introduced double species names: the first word is the name of the genus, the second - the species, for example, Aurelia aurita - eared jellyfish, Aurelia cyanea - polar jellyfish. This system of names still exists today. Subsequently, the system of the organic world, proposed by K. Linnaeus, was significantly changed. At the heart of the modern classification, which is natural, the principle of kinship of species with both living and extinct lies.

Thus, the goal of natural classification- creation of a unified system of living organisms, which would cover all the diversity of living organisms, reflect the origin and history of their development. In the modern system, organisms are divided into groups based on the relationships between them by origin. Systematic categories, or taxa, are the names of groups of living organisms that are united by similar characteristics. For example, the class Birds are highly organized vertebrates, the body of which is covered with feathers, and the forelimbs are turned into wings. The largest systematic categories of organisms are empires (precellular and cellular organisms). Empires are divided into kingdoms.

organic world

Kingdom Viruses

Kingdom of Prokaryotes Kingdom of Eukaryotes

(non-nuclear) (nuclear)

Kingdom Bacteria

Kingdom Plants Kingdom Animals Kingdom Fungi Kingdoms in animals unite types, and in plants departments. Examples of systematic categories:

Systems in which the higher categories consistently include lower and lower categories are called hierarchical (from the Greek hieros - sacred, arche - power), that is, systems whose levels obey certain rules.

An important stage in the development of biology was the period of formation of systematization, which is associated with the name Carl Linnaeus(1707-1778). K. Linnaeus believed that living nature was created by the Creator, the species are immutable. The scientist based the classification on signs of similarity, and not relationship between species. Despite the mistakes made by K. Linnaeus, his contribution to the development of science is enormous: he streamlined ideas about the diversity of flora and fauna.

At the end of the 18th century, changes took place in views on the origin of life: ideas appeared about the origin of modern organisms from distant ancestors.

The idea of the evolution of the organic world is expressed by Jean Baptiste Lamarck(1744-1829). The main merits of Lamarck include the following:

Introduced the term "biology";

Improved the classification already existing at that time;

He tried to determine the causes of the evolutionary process (according to Lamarck, the cause of evolution is the desire for self-improvement - an exercise and not an exercise of organs);

He believed that the process of historical change occurs from simple to complex; species change under the influence of environmental conditions;

He expressed the idea of the origin of man from ape-like ancestors.

Lamarck's fallacies include:

The idea of internal striving for self-improvement;

The assumption of the inheritance of changes that have arisen under the influence of the external environment.

The merit of Lamarck is the creation of the first evolutionary doctrine.

In the 19th century, science, industry, and agriculture were intensively developing. The successes of science and the practical activity of man laid the foundation on which evolutionary theory developed.

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:

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.

*Name*	*Description*	*Examples*
Morphological	The similarity of the external and internal structure and difference from other species. Not to be confused with sexual dimorphism	Titmouse titmouse and moskovka
Physiological	The similarity of life processes in cells and organs, the ability to one type of reproduction	The difference in the composition of insulin in a bull, horse, pig
Biochemical	The composition of proteins, nucleotides, biochemical reactions, etc.	Plants synthesized various substances - alkaloids, essential oils, flavonoids
Ecological	Single ecological niche for one species	Intermediate host of bovine tapeworm - only cattle
ethological	Behavior, especially during mating season	Attracting a mate of one's own species by special birdsong
Geographical	Settlement in one area	The ranges of humpback whales and dolphins do not match
Genetic	A certain karyotype is the similarity in the number, shape, size of chromosomes	The human genotype consists of 46 chromosomes
reproductive	Individuals of the same species can only interbreed, reproductive isolation	Drosophila sperm, falling into a female of a different species, is destroyed by immune cells
Historical	A set of genetic, geographical, evolutionary data about one species	The presence of a common ancestor and differences in evolution

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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