What kind of criteria do you know. Characteristics of the type criteria. Genetic criterion of the species

1. What is a view?

Answer. View (lat. species) - taxonomic, systematic unit, a group of individuals with common morphophysiological, biochemical and behavioral signs, capable of interbreeding, giving fertile offspring in a number of generations, naturally distributed within a certain range and similarly changing under the influence of factors external environment. Species - a really existing genetically indivisible unit of the living world, the main structural unit in the system of organisms.

2. What types of plants and animals do you know?

Answer. Plant species: European bathing suit, Altai anemone, two-leafed love, needle-leaved carnation, venus slipper, etc.

Animal species: brown bear, Siberian roe deer, lynx, pine marten, black ferret, European mink. striped chipmunk, flying squirrel, gray partridge, black grouse and others.

Questions after § 53

1. Define a species.

Answer. Species- this is a set of individuals that have the ability to interbreed with the formation of fertile offspring; inhabiting a certain area; having a number of common morphological and physiological signs and similarities in relationships with the biotic and abiotic environment.

Biological species is not only a systematic category. This is a holistic and isolated element of wildlife from other species. The integrity of a species is manifested in the fact that its individuals can live and reproduce only by interacting with each other due to the mutual adaptations of organisms developed in the process of evolution: the peculiarities of the coordination of the structure of the mother's organism and the embryo, signaling and perception systems in animals, the common territory, the similarity of life habits and reactions to seasonal climate changes, etc. Species adaptations ensure the preservation of the species, although sometimes they can damage individual individuals. River perch, for example, feeds on their own young, due to which the species survives with a lack of food, even despite the loss of part of the offspring. Each species exists in nature as a historically emerged integral formation.

2. What kind of criteria do you know?

Answer. Characteristic features and properties by which some species differ from others are called species criteria.

Morphological criterion is the similarity of external and internal structure organisms. Carl Linnaeus, for example, defined species as whole groups of organisms distinct from others. life forms on the basis of the structure. In other words, the presence of structural features that make a certain group of organisms similar friend on a friend and at the same time different from all other groups, and there is a criterion for classifying them as a given species.

Individuals within a species are sometimes so variable that it is not always possible to determine the species by morphological criteria alone. There are species morphologically similar. These are twin species that are open in all systematic groups. For example, in black rats, two twin species are known - with 38 and 49 chromosomes; the malarial mosquito has 6 twin species, and the small loach fish, which is widespread in fresh water, has 3 such species. Twin species are found among a wide variety of organisms: fish, insects, mammals, plants, but individuals of such twin species do not interbreed.

A genetic criterion is a set of chromosomes characteristic of each species; their strictly defined number, size and shape, DNA composition. The chromosome set is the main species trait. individuals different types have different sets of chromosomes, so they cannot interbreed and are reproductively restricted from each other in natural conditions.

The physiological criterion is the similarity of the body's reactions to external influences, the rhythms of development and reproduction. This criterion is based on the similarity of all life processes, and above all reproduction. Representatives of different species, as a rule, do not interbreed or their offspring are sterile. However, there are exceptions. For example, dogs can produce offspring by mating with wolves. Hybrids of some species of birds (canaries, finches), as well as plants (poplars, willows) can be fruitful. Consequently, the physiological criterion is also insufficient to determine the species belonging of individuals.

An ecological criterion is a position characteristic of a species in natural communities, its relations with other species, sets of environmental factors necessary for existence.

Geographic criterion - the area of ​​distribution, a certain area occupied by a species in nature.

The historical criterion is the commonality of ancestors, a single history of the emergence and development of the species.

3. What is the integrity of the species, how does it manifest itself?

Answer. View is an integral system. The view is a single complete system. The integrity of the species is ensured by its isolation from other species due to a specific chromosome set (reproductive isolation).

The integrity of a species is also determined by the bonds that its individuals form in populations and subspecies. Relationships between males and females, parents and their offspring, individuals of different ages in a pack, herd and colony make it possible to successfully reproduce, take care of offspring, provide protection from enemies, etc. The totality of connections ensures the existence of the species as an integral system.

4. Why is it important to preserve species in nature?

Answer. Biodiversity on the planet is the presence on it a large number species of all kingdoms: animals, plants, fungi. The task of preserving them is one of the main ones in ecology. Planet Earth is really rich, therefore, a person is obliged to protect this wealth, at least so that it goes to the next generations of people. So that grandchildren and great-grandchildren can see wonderful animals, beautiful corners of nature, they can use medicinal plants. Any plant, animal (even the smallest) is part of the biogeocenosis, and in general, is included in the entire ecosystem of the Earth. The body participates in the circulation of substances, being a link in the food chain. Producing plants synthesize nutrients using solar energy. Consumers consume the energy accumulated by plants and other animals, deritophages “utilize” dead animals, decomposers finally decompose the nutrient residues. Thus, each organism occupies a certain place in nature and performs a certain role. The disappearance of one link can cause the disappearance of several more, changing the entire chain. There will be not only impoverishment the food chain, but also a violation of the balance of species in the ecosystem. Some species may increase disproportionately in numbers and cause ecological disaster. How, for example, an unprecedented breeding of locusts can deprive the harvest of entire areas. By preserving the richness of species on the planet, we thus maintain the stability of ecosystems, ensure the safety of life of all species, including human life. In addition, scientists want to keep and genetic information of each species, with the expectation of future technologies that will allow you to recreate animal world of the past, for example, in isolated recreations (parks), to recreate species of animals and plants that are extinct and are now dying out.

Vertyanov S. Yu.

Distinguishing supraspecific taxa is, as a rule, quite easy, but a clear distinction between the species themselves encounters certain difficulties. Some species occupy geographically separated areas of habitat (ranges) and therefore do not interbreed, but in artificial conditions give fertile offspring. Linneevskoe short definition species as a group of individuals that freely interbreed and produce fertile offspring, is not applicable to organisms that reproduce parthenogenetically or asexually (bacteria and unicellular animals, many higher plants), as well as extinct forms.

Aggregate hallmarks species is called its criterion.

The morphological criterion is based on the similarity of individuals of the same species in terms of a set of features of external and internal structure. Morphological criterion is one of the main ones, but in some cases morphological similarity is not enough. The malarial mosquito was previously referred to as six non-interbreeding similar species, of which only one carries malaria. There are so-called twin species. Two species of black rats, outwardly almost indistinguishable, live separately and do not interbreed. The males of many creatures, such as birds (bullfinches, pheasants), outwardly bear little resemblance to females. Adult male and female threadtail eels are so dissimilar that for half a century scientists placed them in different genera, and sometimes even in different families and suborders.

Physiological and biochemical criterion

It is based on the similarity of the life processes of individuals of the same species. Some species of rodents have the ability to hibernate, while others do not. Many related plant species differ in their ability to synthesize and accumulate certain substances. Biochemical analysis allows you to distinguish between types unicellular organisms that do not reproduce sexually. Anthrax bacilli, for example, produce proteins that are not found in other types of bacteria.

The possibilities of the physiological-biochemical criterion are limited. Some proteins have not only species, but also individual specificity. There are biochemical signs that are the same in representatives of not only different species, but even orders and types. Physiological processes can proceed in a similar way in different species. Thus, the metabolic rate of some arctic fish is the same as that of other fish species. southern seas.

Genetic criterion

All individuals of the same species have a similar karyotype. Individuals of different species have different chromosome sets, cannot interbreed and live in natural conditions separately from each other. In two twin species of black rats different amount chromosomes - 38 and 42. The karyotypes of chimpanzees, gorillas and orangutans differ in the location of genes in homologous chromosomes. The differences between the karyotypes of bison and bison, which have 60 chromosomes in the diploid set, are similar. Differences in the genetic apparatus of some species can be even more subtle and consist, for example, in the different nature of the switching on and off of individual genes. The use of only a genetic criterion is sometimes insufficient. One species of weevil combines diploid, triploid and tetraploid forms, the house mouse also has different sets of chromosomes, and the gene of the human nuclear histone H1 protein differs from the homologous pea gene by only one nucleotide. Such variable DNA sequences have been found in the genome of plants, animals and humans that people can distinguish between brothers and sisters by them.

Reproductive criterion

(Latin reproducere reproduce) is based on the ability of individuals of the same species to produce fertile offspring. Important role when crossing, the behavior of individuals plays - marriage ritual, species-specific sounds (birdsong, grasshoppers chirping). By the nature of the behavior, individuals recognize the marriage partner of their species. Individuals of similar species may not interbreed due to inconsistencies in mating behavior or inconsistencies in breeding sites. So, females of one species of frogs spawn along the banks of rivers and lakes, and the other - in puddles. Similar species may not interbreed due to differences mating periods or terms of mating when living in different climatic conditions. different dates flowering in plants is prevented cross pollination and serve as a criterion for belonging to different species.

Reproductive criterion is closely related to genetic and physiological criteria. The viability of gametes depends on the feasibility of conjugation of chromosomes in meiosis, and hence on the similarity or difference in the karyotypes of crossing individuals. Dramatically reduces the possibility of crossing the difference in daily physiological activity (daily or night image life).

The use of only the reproductive criterion does not always make it possible to clearly distinguish species. There are species that are clearly distinguishable by morphological criteria, but which, when crossed, give fertile offspring. From birds, these are some species of canaries, finches, from plants - varieties of willows and poplars. A representative of the order of artiodactyl bison lives in the steppes and forest-steppes North America and never in natural conditions is found with the bison living in the forests of Europe. In zoo conditions, these species produce fertile offspring. Thus, the population of European bison, which was practically exterminated during the world wars, was restored. They interbreed and give fertile offspring of yaks and large cattle, white and brown bears, wolves and dogs, sables and martens. In the plant kingdom, interspecific hybrids are even more common, among plants there are even intergeneric hybrids.

Ecological geographical criterion

Most species occupy a certain territory (range) and an ecological niche. Buttercup caustic grows in meadows and fields, in more damp places another species is common - creeping buttercup, along the banks of rivers and lakes - burning buttercup. Similar species living in the same range may differ in ecological niches - for example, if they eat different foods.

The use of the ecological-geographical criterion is limited by a number of reasons. The range of the species may be discontinuous. The species range of the white hare is the islands of Iceland and Ireland, the north of Great Britain, the Alps and north-west Europe. Some species have the same range, such as two species of black rats. There are organisms that are distributed almost everywhere - many weeds, a number of insect pests and rodents.

The problem of species definition sometimes grows into a complex scientific problem and is solved using a set of criteria. Thus, a species is a set of individuals occupying a certain area and possessing a single gene pool, providing hereditary similarity of morphological, physiological, biochemical and genetic traits, in natural conditions interbreeding and producing fertile offspring.

Superorganism systems. Evolution organic world

evolutionary doctrine

Basic concepts:

species, species criteria, population, taxonomy, classification, history evolutionary ideas, synthetic theory of evolution, driving forces of evolution, forms natural selection, population waves, genetic drift, artificial selection, types of struggle for existence, results of evolution, microevolution, speciation, isolation, fitness, relative nature fitness, forms and directions of evolution, biological progress and regression, macroevolution, aromorphosis, idioadaptation, degeneration, evidence of 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 based on the totality characteristic features, properties, which are called features. Species features that distinguish one species from another are called species criteria.

View criteria - set 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 included in the composition a certain kind. By appearance, size and color of plumage, for example, it is easy to distinguish a large spotted woodpecker from a green one, great tit from crested. 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 malarial mosquito previously named 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, the 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 significant intraspecific variability in almost all biochemical parameters (sequence of amino acids in protein molecules and nucleotides in individual DNA regions). At the same time, many biochemical features are conservative: some are found in all representatives of this 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- 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 different ages(correlation 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 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 the creation of the system, but also in the fact that he introduced double names of species: the first word is the name of the genus, the second is 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 modern system Organisms are classified into groups based on 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 milestone development of biology was the period of formation of systematization, which is associated with the name Carl Linnaeus(1707-1778). K. Linnaeus believed that Live nature 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;

Tried to figure out the reasons evolutionary process(according to Lamarck, the reason for 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, Agriculture. The successes of science and the practical activity of man laid the foundation on which evolutionary theory developed.

In biology, a species is a certain set of individuals that have a hereditary similarity of physiological, biological and morphological features, are able to freely interbreed and produce viable offspring. Species are stable genetic systems, because in nature they are separated by some series of barriers from each other. Scientists distinguish between them according to a number of basic features. Usually, the following species criteria are distinguished: morphological, geographical, ecological, genetic, physico-biochemical.

Morphological criterion

Such signs are the main ones in this system. Morphological criteria species are based on external differences between individual groups of animals or plants. This condition subdivides into species organisms that clearly differ from each other in internal or external morphological features.

Geographic criteria of the species

They are based on the fact that representatives of each stable genetic system live within limited spaces. Such areas are called areas. However, the geographical criterion has some shortcomings. It is not universal enough for the following reasons. First, there are some cosmopolitan species that are distributed all over the planet (for example, the orca whale). Secondly, in many biological aggregates, the ranges coincide geographically. Thirdly, in the case of some too rapidly dispersing populations, the ranges are very variable (for example, a sparrow or a house fly).

Ecological criterion of the species

It is assumed that each species is characterized by certain characteristics, such as the type of food, timing of reproduction, habitat, and everything that determines the ecological niche it occupies. This criterion is based on the assumption that the behavior of some animals differs from the behavior of others.

Genetic criterion of the species

This takes into account the main property of any species - its genetic isolation from others. Plants and animals of different stable genetic systems almost never interbreed. Of course, a species cannot be completely isolated from the influx of genes from related species. However, at the same time, he generally retains the constancy of his genetic composition over a really long period of time. It is in the genetic component that the clearest differences between representatives of different biological populations lie.

Physico-biochemical criteria of the species

Such criteria also cannot serve as an absolutely reliable way to distinguish between species, since fundamental biochemical processes
occur in similar groups in the same way. And in the environment of each individual species there is a certain number of adaptations to certain living conditions, which affects the change in biochemical processes.

conclusions

Thus, according to some single criterion, it is very difficult to distinguish between species. The belonging of an individual to any particular species should be determined only through a comprehensive comparison according to a number of criteria - all or at least the majority. Individuals that occupy a certain territory and are able to freely interbreed with each other are a species population.