The relative nature of the criteria of the species. Type and its criteria

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- 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 belonging of individuals to a particular species is determined on the basis of a number of criteria.

View criteria- these are various taxonomic (diagnostic) characters that are characteristic of one species, but are absent in other species. The set of features by which one species can be reliably distinguished from other species is called the species radical (N.I. Vavilov).

Type criteria are divided into basic (which are used for almost all types) and additional (which are difficult to use for all types).

Basic view criteria

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

For example: in an ordinary viper, the nostril is located in the center of the nasal shield, and in all other vipers (nosed, Asia Minor, steppe, Caucasian, viper) the nostril is shifted to the edge of the nasal shield.

Species-twins. Thus, closely related species may differ in subtle characters. There are twin species that are so similar that it is very difficult to use morphological criteria to distinguish them. For example, the malarial mosquito species is actually represented by nine very similar species. These species differ morphologically only in the structure of the reproductive structures (for example, the color of the eggs in some species is smooth gray, in others - with spots or stripes), in the number and branching of hairs on the limbs of the larvae, in the size and shape of the wing scales.

In animals, twin species are found among rodents, birds, many lower vertebrates (fish, amphibians, reptiles), many arthropods (crustaceans, ticks, butterflies, Diptera, Orthoptera, Hymenoptera), mollusks, worms, coelenterates, sponges, etc.

Notes on sibling species (Mayr, 1968).

1. There is no clear distinction between ordinary species (“morphospecies”) and twin species: it is just that in twin species, morphological differences are minimally expressed. Obviously, the formation of sibling species follows the same patterns as speciation as a whole, and evolutionary changes in groups of sibling species occur at the same rate as in morphospecies.

2. Species-twins, when subjected to careful study, usually show differences in a number of small morphological characters (for example, male insects belonging to different species clearly differ in the structure of copulatory organs).

3. Reorganization of the genotype (more precisely, the gene pool), leading to mutual reproductive isolation, is not necessarily accompanied by visible changes in morphology.

4. In animals, twin species are more common if morphological differences have less effect on the formation of mating pairs (for example, if smell or hearing is used for recognition); if animals rely more on sight (most birds), then twin species are less common.

5. The stability of the morphological similarity of twin species is due to the existence of certain mechanisms of morphogenetic homeostasis.

At the same time, there are significant individual morphological differences within species. For example, the common viper is represented by a variety of color forms (black, gray, bluish, greenish, reddish and other shades). These features cannot be used to distinguish species.

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

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

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

For animals, instead of the concept of "ecological niche", the concept of "adaptive zone" is often used. For plants, the concept of "edapho-phytocenotic area" is often used.

adaptive zone- this is a certain type of habitat with a characteristic set of specific environmental conditions, including the type of habitat (water, ground-air, soil, organism) and its particular features (for example, in the ground-air habitat - the total amount of solar radiation, precipitation, relief , atmospheric circulation, the distribution of these factors by season, etc.). In the biogeographic aspect, adaptive zones correspond to the largest subdivisions of the biosphere - biomes, which are a collection of living organisms in combination with certain conditions of their habitat in vast landscape-geographic zones. However, different groups of organisms use the resources of the environment in different ways and adapt to them in different ways. Therefore, within the biome of the coniferous-broad-leaved zone of temperate forests, one can distinguish adaptive zones of large guarding predators (lynx), large catching predators (wolf), small tree-climbing predators (marten), small terrestrial predators (weasel), etc. Thus, the adaptive zone is an ecological concept that occupies an intermediate position between the habitat and the ecological niche.

Edapho-phytocenotic area- this is a set of bioinert factors (primarily soil, which are an integral function of the mechanical composition of soils, topography, the nature of moisture, the impact of vegetation and the activity of a microorganism) and biotic factors (primarily a combination of plant species) of nature, which constitute the immediate environment of the area of ​​interest. us kind.

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

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

Additional View Criteria

4. Physiological and biochemical criterion. It is based on the fact that different species can differ in the amino acid composition of proteins. Based on this criterion, for example, some types of gulls are distinguished (silver, klusha, western, Californian).

At the same time, within a species, there is variability in the structure of many enzymes (protein polymorphism), and different species may have similar proteins.

5. Cytogenetic (karyotypic) criterion. It is based on the fact that each species is characterized by a certain karyotype - the number and shape of metaphase chromosomes. For example, all hard wheats have 28 chromosomes in the diploid set, and 42 chromosomes in all soft wheats.

However, different species can have very similar karyotypes: for example, most species of the cat family have 2n=38. At the same time, chromosomal polymorphism can be observed within the same species. For example, in elks of Eurasian subspecies 2n=68, and in elks of North American species 2n=70 (in the karyotype of North American elks there are 2 less metacentrics and 4 more acrocentrics). Some species have chromosome races, for example, in a black rat - 42 chromosome (Asia, Mauritius), 40 chromosome (Ceylon) and 38 chromosome (Oceania).

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

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

Pacific salmon (pink salmon, chum salmon, etc.) live for two years and spawn just before death. Consequently, the descendants of individuals that spawned in 1990 will breed only in 1992, 1994, 1996 (the “even” race), and the descendants of individuals that spawned in 1991 will breed only in 1993, 1995, 1997 (“ odd" race). An "even" race cannot interbreed with an "odd" race.

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

8. Historical criterion. Based on the study of the history of a species or group of species. This criterion is complex in nature, since it includes a comparative analysis of modern species ranges, analysis

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.

Morphological criterion reflects the external and internal similarity of individuals of the same species.

So, black and white crows belong to different species, which can be determined by their appearance. But organisms that belong to the same species may differ from each other in some signs and properties. However, these differences are very small compared to those observed in individuals of different species. Meanwhile, there are species that have an external resemblance, but cannot interbreed with each other. These are the so-called twin species. So, in Drosophila, the malarial mosquito and the black rat, two twin species have been established. Twin species are also found in amphibians, reptiles, birds, and even mammals. Therefore, the morphological criterion is not decisive for the differentiation of species. However, for a long time this criterion was considered the main and the only one in determining species (Fig. 39).

At the core physiological criterion lies the similarity of life processes in individuals of each species, especially reproduction.

Representatives of different species do not interbreed, and if they interbreed, they do not give offspring. The non-crossing of species is explained by differences in the structure of the genital organs, different periods of reproduction, and other reasons. However, in nature there are cases when certain types of plants (poplar, willow), birds (canaries) and animals (hares) can interbreed and produce offspring. This also indicates that one physiological criterion is also not enough to distinguish between species.

Under this criterion understand the specific environmental conditions in which they live and to which individuals of a particular species have adapted. For example, a poisonous buttercup grows in fields and meadows, a creeping buttercup grows in damp places, along the banks of rivers, reservoirs, and in swampy places a burning ranunculus.

This criterion refers to the set of chromosomes, structure and coloration characteristic of each species. One twin of the black rat has 38, the other has 42 chromosomes. Although the genetic criterion is characterized by some constancy, this similarity is relative, since differences in the number and structure of chromosomes can be observed within a species. In addition, the number of chromosomes may be the same in different species. For example, cabbage and radish each have 18 chromosomes.

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

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

What is a view?

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

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

Formation of new species

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

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

What is the ecological criterion of a species

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

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

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

Flora in ecological criteria

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

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

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

Temperature regime within the ecological criterion

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

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

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

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

The influence of soil on the development of the species

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

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

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

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

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

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