Natural and artificial classification. Natural and artificial ecosystems The natural classification system is based on

Remember:

What does taxonomy study?

Answer. Systematics studies the distribution of living organisms into certain groups (taxa) according to the commonality of their structure with maximum preservation of evolutionary connections.

Why was Carl Linnaeus' system artificial?

Answer. Linnaeus was the first to create a convenient, accurate and strict plant system, albeit on an artificial basis. It is artificial because when determining the similarity of plants and classifying them, he did not take into account all the features of similarity and difference, not the totality of all morphological characteristics of a plant - a totality that alone can determine the true relationship of two forms, but built his entire system solely on the basis of one only an organ - a flower.

Questions after § 27

What is the difference between a natural system and an artificial one?

Answer. There are two types of classification - artificial and natural. In artificial classification, one or more easily distinguishable features are taken as a basis. It is created and used to solve practical problems, when the main thing is ease of use and simplicity. Linnaeus's classification is also artificial because it did not take into account important natural relationships

Natural classification is an attempt to use the natural relationships between organisms. In this case, more data is taken into account than in artificial classification, and not only external, but also internal characteristics are taken into account. Similarities in embryogenesis, morphology, anatomy, physiology, biochemistry, cellular structure and behavior are taken into account.

What is the system of living organisms proposed by K. Linnaeus? Why?

Answer. The system proposed by K. Linnaeus was artificial. Linnaeus based it not on the relationship of plants, but on several external, easily distinguishable characteristics. He based the classification of plants only on the structure of the generative organs. When classified according to 1-2 arbitrarily chosen characteristics, systematically distant plants sometimes ended up in the same class, and related ones - in different ones. For example, when counting the number of stamens in carrots and flax, Linnaeus placed them in the same group on the basis that they each had five stamens per flower. In fact, these plants belong to different genera and families: carrots are from the Apiaceae family, flax is from the flax family. The artificiality of the classification “by stamens” is in many cases so obvious that it cannot be ignored. Linnaeus’s family of “eight-stamens” included buckwheat, maple and raven’s eye.

In the 5th grade (5 stamens) there were carrots, flax, quinoa, bellflower, forget-me-not, currant, viburnum. In the 21st class, next to duckweed there were sedge, birch, oak, nettle and even spruce and pine. Lingonberries, bearberry, which is similar to it, and blueberries are cousins, but they fall into different classes, since the number of stamens is different.

But with all its shortcomings, the Linnaean plant system made it easy to understand the huge number of species already known to science.

Based on the similarity and shape of the beak, the chicken and the ostrich fell into the same order, while chickens belong to the keel-breasted species, and ostriches belong to the ratite species (and in its type “worms” 11 modern types are collected). His zoological system was built on the principle of “degradation” - from complex to simple.

K. Linnaeus, recognizing the artificiality of his system, wrote that “the artificial system will exist before the creation of the natural one.”

What is binary nomenclature and what is its significance for taxonomy?

Answer. Binary nomenclature is the designation of species of animals, plants and microorganisms in two Latin words: the first is the name of the genus, the second is the specific epithet (for example, Lepus europaeus - brown hare, Centaurea cyanus - blue cornflower). When a species is described for the first time, the author's surname is also given in Latin. Proposed by K. Baugin (1620), formed the basis of taxonomy by K. Linnaeus (1753).

The name of the genus is always written with a capital letter, the name of the species is always written with a small letter (even if it comes from a proper name).

Explain the principle of taxon hierarchy using specific examples.

Answer. At the first stage of classification, experts divide organisms into separate groups, which are characterized by a certain set of characteristics, and then place them in correct sequence. Each of these groups in taxonomy is called a taxon. A taxon is the main object of systematics research, representing a group of zoological objects that actually exist in nature, which are quite isolated. Examples of taxa include such groups as “vertebrates”, “mammals”, “artiodactyls”, “red deer” and others.

In the classification of Carl Linnaeus, taxa were arranged in the following hierarchical structure:

Kingdom - animals

Class - mammals

Order - primates

Rod - person

View - Homo sapiens

One of the principles of systematics is the principle of hierarchy, or subordination. It is implemented as follows: closely related species are united into genera, genera are united into families, families into orders, orders into classes, classes into types, and types into a kingdom. The higher the rank of a taxonomic category, the fewer taxa at that level. For example, if there is only one kingdom, then there are already more than 20 types. The principle of hierarchy allows one to very accurately determine the position of a zoological object in the system of living organisms. An example is the systematic position of the white hare:

Animal Kingdom

Type Chordata

Class Mammals

Order Lagomorpha

Family Zaitsevye

Genus Hares

Mountain hare species

In addition to the main taxonomic categories, zoological taxonomy also uses additional taxonomic categories, which are formed by adding the corresponding prefixes to the main taxonomic categories (super-, sub-, infra- and others).

The systematic position of the mountain hare using additional taxonomic categories will be as follows:

Animal Kingdom

Subkingdom True multicellular organisms

Type Chordata

Subphylum Vertebrates

Superclass Quadrupeds

Class Mammals

Subclass Viviparous

Infraclass Placental

Order Lagomorpha

Family Zaitsevye

Genus Hares

Mountain hare species

Knowing the position of the animal in the system, one can characterize its external and internal structure, features of biology. Thus, from the above systematic position of the white hare, one can obtain the following information about this species: it has a four-chambered heart, a diaphragm and fur (characters of the class Mammals); in the upper jaw there are two pairs of incisors, there are no sweat glands in the skin of the body (characters of the order Lagomorpha), the ears are long, the hind limbs are longer than the front ones (characters of the family Lagomorpha), etc. This is an example of one of the main functions of classification - prognostic (forecast, prediction function). In addition, the classification performs a heuristic (cognitive) function - it provides material for reconstructing the evolutionary paths of animals and an explanatory one - it demonstrates the results of studying animal taxa. To unify the work of taxonomists, there are rules that regulate the process of describing new animal taxa and assigning scientific names to them.

Ecosystems are one of the key concepts of ecology, which is a system that includes several components: a community of animals, plants and microorganisms, a characteristic habitat, a whole system of relationships through which the interchange of substances and energies occurs.

In science, there are several classifications of ecosystems. One of them divides all known ecosystems into two large classes: natural, created by nature, and artificial, those created by man. Let's look at each of these classes in more detail.

Natural ecosystems

As noted above, natural ecosystems were formed as a result of the action of natural forces. They are characterized by:

• The close relationship between organic and inorganic substances
• A complete, closed circle of the circulation of substances: starting from the appearance organic matter and ending with its disintegration and decomposition into inorganic components.
• Resilience and self-healing ability.

All natural ecosystems are defined by the following characteristics:

• 1. Species structure: the number of each species of animal or plant is regulated by natural conditions.
  2. Spatial structure : all organisms are arranged in a strict horizontal or vertical hierarchy. For example, in a forest ecosystem, tiers are clearly distinguished; in an aquatic ecosystem, the distribution of organisms depends on the depth of the water.
  3. Biotic and abiotic substances. The organisms that make up the ecosystem are divided into inorganic (abiotic: light, air, soil, wind, humidity, pressure) and organic (biotic - animals, plants).
  4. In turn, the biotic component is divided into producers, consumers and destroyers. Producers include plants and bacteria, which use sunlight and energy to create organic matter from inorganic substances. Consumers are animals and carnivorous plants that feed on this organic matter. Destroyers (fungi, bacteria, some microorganisms) are the crown of the food chain, as they carry out the reverse process: organic matter is converted into inorganic substances.

The spatial boundaries of each natural ecosystem are very arbitrary. In science, it is customary to define these boundaries by the natural contours of the relief: for example, a swamp, a lake, mountains, rivers. But in the aggregate, all ecosystems that make up the bioshell of our planet are considered open, since they interact with the environment and with space. In the very general idea the picture looks like this: living organisms are obtained from environment energy, cosmic and terrestrial substances, and the output is sedimentary rocks and gases, which ultimately escape into space.

All components of the natural ecosystem are closely interconnected. The principles of this connection develop over years, sometimes centuries. But this is precisely why they become so stable, since these connections and climatic conditions determine the species of animals and plants that live in a given area. Any imbalance in a natural ecosystem can lead to its disappearance or extinction. Such a violation could be, for example, deforestation or extermination of a population of a particular animal species. In this case, the food chain is immediately disrupted, and the ecosystem begins to “fail.”

By the way, introducing additional elements into ecosystems can also disrupt it. For example, if a person begins to breed animals in the chosen ecosystem that were not there initially. A clear confirmation of this is the breeding of rabbits in Australia. At first this was beneficial, since in such a fertile environment and excellent climatic conditions for breeding, the rabbits began to reproduce with incredible speed. But in the end everything came to a crash. Countless hordes of rabbits devastated the pastures where sheep had previously grazed. The number of sheep began to decline. And a person gets much more food from one sheep than from 10 rabbits. This incident even became a saying: “The rabbits ate Australia.” It took incredible effort from scientists and a lot of expense before they managed to get rid of the rabbit population. It was not possible to completely exterminate their population in Australia, but their numbers decreased and no longer threatened the ecosystem.

Artificial ecosystems

Artificial ecosystems are communities of animals and plants living in conditions created for them by humans. They are also called noobiogeocenoses or socioecosystems. Examples: field, pasture, city, community, spaceship, zoo, garden, artificial pond, reservoir.

The most simple example artificial ecosystem is an aquarium. Here the habitat is limited by the walls of the aquarium, the flow of energy, light and nutrients is carried out by man, who also regulates the temperature and composition of the water. The number of inhabitants is also initially determined.

First feature: all artificial ecosystems are heterotrophic, i.e. consuming ready-made food. Let's take a city as an example, one of the largest artificial ecosystems. The influx of artificially created energy (gas pipeline, electricity, food) plays a huge role here. At the same time, such ecosystems are characterized by a large release of toxic substances. That is, those substances that later serve for the production of organic matter in a natural ecosystem often become unsuitable in artificial ones.

Another distinctive feature of artificial ecosystems is an open metabolic cycle. Let’s take agroecosystems as an example—the most important for humans. These include fields, gardens, vegetable gardens, pastures, farms and other agricultural lands on which people create conditions for the production of consumer products. People take out part of the food chain in such ecosystems (in the form of crops), and therefore the food chain becomes destroyed.

The third difference between artificial ecosystems and natural ones is their small number of species. Indeed, a person creates an ecosystem for the sake of breeding one (less often several) species of plants or animals. For example, in a wheat field, all pests and weeds are destroyed, and only wheat is cultivated. This makes it possible to get a better harvest. But at the same time, the destruction of organisms that are “unprofitable” for humans makes the ecosystem unstable.

Comparative characteristics of natural and artificial ecosystems

It is more convenient to present a comparison of natural ecosystems and socioecosystems in the form of a table:

Natural ecosystems	Artificial ecosystems
The main component is solar energy.	Mainly receives energy from fuels and prepared foods (heterotrophic)
Forms fertile soil	Depletes the soil
All natural ecosystems absorb carbon dioxide and produce oxygen	Most artificial ecosystems consume oxygen and produce carbon dioxide
Great species diversity	Limited number of species of organisms
High stability, ability for self-regulation and self-healing	Weak sustainability, since such an ecosystem depends on human activities
Closed metabolism	Open metabolic chain
Creates habitats for wild animals and plants	Destroys wildlife habitats
Accumulates water, using it wisely and purifying it	High water consumption and pollution

1. Natural selection - the process of survival of individuals with hereditary changes that are useful in given environmental conditions and the leaving of offspring by them - is the main driving force of evolution. The undirected nature of hereditary changes, their diversity, the predominance of harmful mutations and the directing nature of natural selection - the preservation of individuals only with hereditary changes that are useful in a certain environment.

2. Artificial selection is the main method of selection, which deals with the development of new varieties of plants and animal breeds. Artificial selection is the preservation by man for subsequent reproduction of individuals with hereditary changes of interest to the breeder.

3. Comparison of natural and artificial selection.

4. The role of natural selection in the creation of new varieties of plants and animal breeds is to increase their adaptability to environmental conditions.

36. Basic methods of animal selection.

The creation of breeds of domestic animals began following their domestication and domestication, which began 10-12 thousand years ago. Keeping in captivity reduces the effect of the stabilizing form of natural selection. Various forms of artificial selection (first unconscious, and then methodical) lead to the creation of a whole variety of breeds of domestic animals.

Animal breeding, compared to plant breeding, has a number of features. Firstly, animals are characterized mainly by sexual reproduction, therefore any breed is a complex heterozygous system. The assessment of qualities of males that are not externally manifested in them (egg production, fat milk production) is assessed by offspring and pedigree. Secondly, they often have late sexual maturity, the change of generations occurs after a few years. Thirdly, the offspring are few.

The main methods of animal selection are hybridization and selection. There are the same methods of crossing - inbreeding, inbreeding, and unrelated - outbreeding. Inbreeding, as in plants, leads to depression. Selection from animals is carried out according to exterior(certain parameters external structure), because This is precisely the criterion for the breed.

1. Intrabreeding: aimed at preserving and improving the breed. In practice, it is expressed in the selection of the best producers, the culling of individuals that do not meet the requirements of the breed. In breeding farms, stud books are kept that reflect the pedigree, conformation and productivity of animals over many generations.

2. Interbreeding used to create a new breed. In this case, inbreeding is often carried out, parents are crossed with offspring, brothers with sisters, this helps to obtain a larger number of individuals with the desired properties. Inbreeding is accompanied by strict constant selection; usually several lines are obtained, then different lines are crossed.

A good example is the breed of pigs bred by Academician M.F. Ivanov - the Ukrainian White Steppe. When creating this breed, sows of local Ukrainian pigs with low weight and low quality of meat and fat, but well adapted to local conditions, were used. The male sires were boars of the white English breed. The hybrid offspring were again crossed with English boars, inbreeding was used in several generations, pure lines were obtained, by crossing which the ancestors of a new breed were obtained, which in terms of meat quality and weight did not differ from the English breed, and in endurance - from Ukrainian pigs.

3. Using the heterosis effect. Often, during interbreeding, the effect of heterosis appears in the first generation; heterotic animals are distinguished by early maturity and increased meat productivity. For example, when crossing two meat breeds of chickens, heterotic broiler chickens are obtained; when crossing Berkshire and Duroc Jersey pig breeds, early maturing pigs with large weight and good quality of meat and lard are obtained.

4. Progeny test carried out to select males who do not exhibit certain qualities (milk and fat content of bulls, egg production of roosters). To do this, male producers are crossed with several females, the productivity and other qualities of the daughters are assessed, comparing them with the mother’s and with the average breed.

5. Artificial insemination used to obtain offspring from the best male sires, especially since the germ cells can be stored at liquid nitrogen temperature for any time.

6. Using hormonal superovulation and transplantation Dozens of embryos can be taken from outstanding cows per year and then implanted into other cows; the embryos are also stored at liquid nitrogen temperature. This makes it possible to increase the number of offspring from outstanding sires several times.

7. Distant hybridization, interspecific crossing, has been known since ancient times. Most often, interspecific hybrids are sterile; their meiosis is disrupted, which leads to disruption of gametogenesis. WITH ancient times a person uses a hybrid of a mare and a donkey - a mule, which is distinguished by endurance and longevity. But sometimes gametogenesis in distant hybrids proceeds normally, which made it possible to obtain new valuable breeds of animals. An example is arharomerinos, which, like argali, can graze high in the mountains, and, like merino sheep, produce good wool. Fertile hybrids have been obtained by crossing local cattle with yaks and zebu. By crossing beluga and sterlet, a fertile hybrid is obtained - bester, ferret and mink - honorik, a productive hybrid is between carp and crucian carp.

There are two types of classification: auxiliary and natural (scientific).

An auxiliary classification is created with the goal of quickly finding any individual item among the classified items. The purpose of this classification determines the principle of its construction. The auxiliary classification is based on some external insignificant feature, which, however, turns out to be useful in the search process.

Examples of auxiliary classification could be the distribution of course students in a list in alphabetical order, or the same distribution of library cards in an alphabetical catalog, etc. Knowing the order of the letters in the alphabet, we can easily and quickly find the name we need in the list or information about the book we are interested in in the catalog.

But knowing what place a particular object occupies in the auxiliary classification system does not make it possible to state anything about its properties. So, for example, the fact that student Arkhipov is listed first, and student Yakovlev - last, says absolutely nothing about their abilities and character traits. Therefore, the auxiliary classification is not scientific.

In contrast to auxiliary classification, natural classification is the distribution of objects into classes based on their most significant characteristics. The most significant features of an object are those that determine its other features. For example, the most essential characteristic of a person is his ability to work. This sign predetermines the presence in a person of such characteristics as upright walking, the ability to communicate (work presupposes a team), the ability to think, etc.

Classification has a connection with the definition of concepts. Those characteristics in accordance with which objects are distributed into classes must be distinctive species-forming characteristics. We have already seen that indicating the specific distinctive feature is the main task of definition, therefore knowledge of the classification of objects makes it possible to determine them. The more significant a feature underlies the classification, the deeper definitions can be given to the objects included in the classification system.

Thus, natural classification, in contrast to auxiliary classification, allows one to determine the properties of this object based on the place occupied in it by one or another object, without resorting to experimental verification. In some cases, natural classification makes it possible to detect a pattern in changes in the properties of classified objects, which makes it possible to foresee the existence of as yet undiscovered objects and predict their main characteristics. For example, based on periodic table elements D.I. Mendeleev predicted the existence of elements unknown at that time and later discovered, such as gallium, scandium and germanium. Similarly, the American physicist Gell-Mann, based on his classification elementary particles predicted the existence of some particles unknown to him and determined their properties. Later these particles were discovered experimentally.

Although classification plays a huge role in cognition, this role cannot be absolute. Any classification is relative. The relativity of classification is due to two factors: firstly, the relativity of our knowledge and, secondly, the fact that in nature there are no sharp boundaries between individual species.

With the development of science, the classification is clarified and supplemented, as the human mind comprehends the ever deeper essence of things. Instead of one classification, another, more adequate (corresponding) to reality, can be created.

Over time, a classification that is recognized as natural can turn into an artificial one if it turns out that it was based on an insignificant, secondary feature. Such a classification is rejected as unsuitable for science and practice. The history of science knows many similar examples.

The classification (periodization) of the history of human society, for example, before Marxism, was carried out in accordance with which royal dynasties or individual monarchs ruled in a particular era. And only the classics of Marxism created a genuine scientific classification (periodization) of human history, taking as a basis the most essential feature - the method of production of material goods - after which it was discovered that the pre-Marxist classification of history was artificial.

The classification of plants created by the Swedish naturalist Carl Linnaeus also turned out to be artificial. Since the basis was based on an insignificant feature (the number of stamens and the method of their attachment to flowers), as a result of the classification, the elementary rules of division were not observed. Related groups of plants (for example, cereals) found themselves in different, extremely dissimilar classes. Conversely, completely dissimilar plants (for example, oak and one type of sedge) ended up in the same class.

The relative, approximate nature of the classification is also due to the fact that in nature there are no sharp demarcation lines separating a class of objects from another. There are many transitional forms that stand on the border between different classification groups, preserving the features of both one and the other group. F. Engels wrote about this: “Hard and fast lines (absolutely sharp demarcation lines) are incompatible with the theory of development. Even the dividing line between vertebrates and invertebrates is no longer absolute, nor is it between fish and amphibians; and the boundary between birds and reptiles is disappearing more and more every day.”

Classification always operates with concepts such as species, genus, class, accordingly distributing classified objects. According to F. Engels, these concepts “thanks to the theory of development have become fluid and thereby relative.” All this gives the classification a relative, approximate character. But even in this relative meaning, classification continues to be a serious means scientific knowledge, because before exploring development and change, it is necessary to know what is changing and developing. Since every classification is built on a single principle, since it allows us to consider the classified objects in their unity, interconnection and interaction, it allows us to establish patterns of their development.