Group of taxa. Taxonomic (systematic) units. The main taxa are

Classification is the division of the entire diversity of living organisms into various groupings of one level or another, volume and subordination, which allows one to understand this diversity and determine family relations various organisms. The discipline of taxonomy deals with the classification of organisms, as well as the description of the identified groups and the study of all related issues.

The foundations of taxonomy were laid several centuries ago - just remember the Swedish naturalist Carl Linnaeus, whose system of taxonomic ranks he created continues (of course, with additions) to be used to this day. In contrast to artificial systems initially created by man, which group organisms according to an arbitrarily chosen characteristic (http://taxonomy.elgeran.ru).

Historically, there are five main kingdoms of living organisms: animals, plants, fungi, bacteria (or pellets) and viruses. Since 1977, two more kingdoms have also been added to them - protists and archaea. Since 1998, another one has been distinguished - chromists.

All kingdoms are grouped into four superkingdoms or domains: bacteria, archaea, eukaryotes and viruses. The domain of bacteria includes the kingdom of bacteria, the domain of archaea includes the kingdom of archaea, the domain of viruses includes the kingdom of viruses, and the domain of eukaryotes includes all other kingdoms (ru.wikipedia.org).

The main goals of taxonomy are:

• § name (including description) of taxa,
• § diagnostics (determining the place in the system),
• § extrapolation (that is, prediction of the characteristics of an object), based on the fact that the object belongs to a particular taxon.

The main taxa are:

• § kingdom
• § type (department)
• § Class
• § squad (order)
• § family
• § genus
• § view

Each previous group in this list combines several subsequent ones (thus, a family unites several genera and, in turn, belongs to some order or order). As one moves from a higher hierarchical group to a lower one, the degree of relatedness increases. For a more detailed classification, auxiliary units are used, the names of which are formed by adding the prefixes “over-” and “under-” to the main units.

Only species can be given a relatively strict definition; all other taxonomic groups are defined quite arbitrarily

Kingdom- one of the highest taxonomic categories (ranks) in the system of the organic world.

Department (Section, Division)- one of the taxonomic categories used in plant taxonomy. Corresponds to the type in the taxonomy of animals.

Latin names of specific departments have standard endings - phyta.

Type (Typus or Phylum)- one of the largest taxonomic categories used in the taxonomy of animals, unites related classes.

The term "Type" was first proposed in 1825. A. Blainville. Types are often divided into subtypes. The number and volume of Types for different taxonomists ranges from 10 to 33.

Class (Class, Classis)- a taxonomic category or taxon of rank below a division. Latin names of classes, like taxa, have a standard ending - psida.

Squad (Ordo)- in animal taxonomy, a taxonomic category that unites several families. Close units make up a class. In plant taxonomy, order is equivalent to order.

Suborder (Subordo)

Order. One of the main categories of taxonomy, uniting related plant families. Latin name order is usually formed by adding the ending ales to the stem of the family name. Large orders are sometimes divided into suborders (subordo). The number of orders in different phylogenetic systems is not the same (according to one system, all families of flowering plants are combined into 94 orders, according to another - into 78).

Family- Systematic category in botany and zoology. A family unites closely related genera that have common origin. Large families are sometimes divided into subfamilies. Close relatives are grouped into orders in animals, into orders in plants, and in some cases into intermediate groups - superfamilies, suborders. Latin names of families, as taxa, have the standard endings - aceae.

Genus- the main supraspecific taxonomic category, uniting phylogenetically the closest (closely related) species to each other.

Scientific name genders are denoted by one Latin word. Genera that include only 1 species are called monotypic. Genera with several or many species are often divided into subgenera, which include species that are especially closely related to each other. Each genus is necessarily part of a family.

Species- the basic structural unit in the system of living organisms. A species is a collection of populations of individuals capable of interbreeding to form fertile offspring and, as a result, producing transitional hybrid populations between local forms, inhabiting a certain area, possessing a number of common morpho-physiological characteristics and types of relationships with the environment (http://cyclowiki.org/wiki ).

At the first stage of classification, experts divide organisms into separate groups, which are characterized by a certain set of characteristics, and then arrange them in the correct sequence. Each of these groups in taxonomy is called a taxon (from the Greek taxon - (location, order). A taxon is the main object of systematics research, representing a group of zoological objects that actually exist in nature, which are sufficiently isolated, they can be identified and assigned a certain rank. Examples of taxa include such groups as “vertebrates”, “mammals”, “artiodactyls”, “red deer” and others.

Taxon (lat. taxon, plural taxa; from taxare- “to feel, determine the price by feeling, evaluate”) - a group in the classification consisting of discrete objects united on the basis general properties and signs.

In the International Code of Botanical Literature (Vienna Codex, 2006), the term “taxon” is understood to mean a taxonomic group of any rank, and it is understood that each plant is considered to belong to an indefinite number of taxa of successively subordinate rank, among which the species rank is considered the main one. Taxon is defined similarly in zoology.

In modern biological classifications, taxa form a hierarchical system: each taxon, on the one hand, consists of one or more taxa of a lower level of generality, at the same time each taxon is part of another taxon - a group of more high level community. Such a hierarchical system is called a taxonomic hierarchy, and its various levels are called taxonomic ranks

The three most significant characteristics of a taxon in modern biological systematics are volume, diagnosis and rank.

In the classification of the “father of taxonomy” Carl Linnaeus, taxa were arranged in the following hierarchical structure

Kingdom (lat. regnum) Animalia (animals)

Class (lat. classis) Mammalia (mammals)

Order (Squad) (lat. ordo) Primates (primates)

Genus (lat. genus) Homo (human)

Species (lat. species) Homo sapiens(reasonable person)

Variety (lat. varietas)

The levels of this hierarchy are called ranks. Ranks (universal levels of hierarchy that have proper names) were reflected in the classification at the end of the 17th century and since then, despite criticism from theoretical positions, have formed an integral part of taxonomic practice. In connection with the significantly more detailed understanding of taxonomists about the structure biological diversity the number of ranks has increased significantly since the time of Linnaeus.

Taxon volume can be objectively specified by listing organisms (or taxa of lower rank). Often the volume of a taxon during historical development ideas about the system of a particular group turns out to be much more stable than its rank. Thus, liver mosses in different systems plants were considered either as a family, or as a department or class (in this case, only the rank of the group changed, but not its volume). Such taxa, for which there are established ideas about volume, but not about rank, are often simply called “major groups”.

Monophyly(ancient Greek μόνος - one and φυλή - family clan) - the origin of the taxon from one common ancestor. According to modern ideas, monophyletic in biological systematics is a group that includes all known descendants of a hypothetical closest ancestor, common only to members of this group and no one else. In some groups of organisms, phylogenetic relationships have not been definitively established.

It is now generally accepted that taxa must include descendants and all or some ancestors, although the validity of this latter requirement is increasingly subject to debate. A natural taxon is one such group that is generated through the process of evolution. Such groups are monophyletic. An artificial taxon is the result of an old way of classification (for example, by apparent similarity resulting from the evolution of dissimilar organisms), that is, such taxa are polyphyletic or paraphyletic.

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 this 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:

Kingdom Animalia (Animalia) Phylum Chordata (Chordata)

Class Mammals (Mammalia)

Order Lagomorpha Family Leporidae Genus Lepus

In addition to the main taxonomic categories, additional taxonomic categories are used in zoological systematics, which are formed by adding the corresponding prefixes to the main taxonomic categories (super-, sub-, infra- and others) or auxiliary taxa (cohort, section).

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

Animal Kingdom (Animalia)

Subkingdom True metazoans (Eumetazoa) Phylum Chordata (Chordata)

Subphylum Vertebrates (Invertebrata)

Superclass Tetrapoda

Class Mammals (Mammalia)

Subclass Viviparous (Theria)

Infraclass Placental (Eetheria)

Order Lagomorpha (Lagomorpha)

Family Leporidae

Genus Hares (Lepus)

Species Mountain hare (Lepus timidus)

Knowing the position of the animal in the system, one can characterize its external and internal structure, features of biology. So, from the above systematic position For the white hare, you 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. These rules are compiled in the International Code of Zoological Nomenclature, which is published by the International Commission on Zoological Nomenclature, the latest 4th edition of the code came into force on January 1, 2000.

The history of the development of zoology is closely connected with the history of the formation of the basic principles of animal taxonomy. It would be impossible to understand all the diversity of the Earth's fauna without an apparatus that allows us to record the position of the organisms being studied on the phylogenetic tree of the animal kingdom. Such an apparatus is modern taxonomy, which arose as a result of the painstaking work of many zoologists throughout the history of the development of science.

General principles:

– assignment of a scientific name or concept.

- description.

– highlighting similarities and differences with related concepts.

– classification.

- similarity of species.

Taxonomy

There are many different types of plants on Earth. It is difficult to navigate in their diversity. Therefore, plants, like other organisms, are systematized - distributed, classified into certain groups. Plants can be classified according to their uses. For example, medicinal, spice, oil-bearing plants, etc. are isolated.

The most common system used by botanists today is hierarchical. It is built on the “box within a box” principle. Any level of the system hierarchy is called taxonomic rank (taxonomic category).

Taxon- these are actually existing or existing groups of organisms, classified in the process of classification into certain taxonomic categories.

Classifying alive organisms, scientists assigned them to one group or another taking into account their similarity (commonality). Such groups are called units of systematics, or taxonomic units.

The main taxonomic rank is – view (species). Usually under biological species understand the totality of populations of individuals capable of interbreeding to form fertile offspring, inhabiting a certain area, possessing a number of common morphophysiological characteristics and types of relationships with the abiotic and biotic environments, and separated from other similar populations of individuals by the absence of hybrid forms.

In other words view is a group of organisms that are similar in structure, live in a certain territory, are adapted to similar living conditions and are capable of producing fertile offspring.

Genus. A group of species similar in many characteristics is united into a genus.

Families. Close genera are united into families.

Classes. Similar in common features families are combined into classes.

Departments. The classes of plants, fungi and bacteria are grouped into divisions.

Kingdom. All plant divisions form the plant kingdom.

Above the view are the genus (genus), family (surname), order (ordo), subclass (subclassis), Class (classis), Department (divisio) and kingdom (regnum).

Within a species, smaller systematic units can be distinguished: subspecies (subspecies), variety (varietas), form (forma); For cultivated ones, the category - variety is used.

Table 1

Basic taxonomic ranks taxonomy of higher plants and examples of taxa

Swedish professor Carl Linnaeus proposed in the 18th century binary nomenclature instead of cumbersome polynomial. Binary nomenclature was introduced by Calus Lineus in 1753. The rules for assigning botanical names to plants are contained in the International Code of Botanical Nomenclature, which is revised at the International Botanical Congresses every 6 years.

The scientific name of the species according to binary nomenclature (double) consists of two Latin words. The first word is the name of the genus, the second is the specific epithet. After the Latin name of the species, the surname or initials of the author who gave the name to the species is written in abbreviation.

For example, view Triticum aestivum L. (wheat) consists of two words: genus Triticum– wheat, specific epithet aestivum– soft.

The scientist who first described the taxon is its author. The author's surname is placed after the Latin name of the taxon, usually in abbreviated form. For example, the letter L. indicates the authorship of Linneus, DS. – De Candolle, Bge. – Bunge, Com. – V.L. Komarov, etc. IN scientific works authorship of taxa is considered mandatory; they are often omitted from textbooks and popular publications.

The Latin name of the family is formed by adding the ending - seae(cee) or – aseae(acee) to the basis of the name of one of the most common genera of this family. For example, gender Roa(bluegrass) gave the family its name Roaseae(bluegrass).

Sometimes alternative, traditional names are allowed, for example, families:

Asteraceae (Asteraceae) – Asteraceae Compositae

Legumes ( Fabaceae) – Moths (Leguminosae)

Celery (Apiaceae) – Umbelliferae (Umbelliferae)

Lamiaceae ( Lamiaceae)– Lamiaceae (Labiaceae)

Bluegrass ( Poaceae)– Cereals (Graminea).

Department names usually end with – phyta ( fita), for example, Angiospermophyta– angiosperms, etc. The names of plant orders end with - ales

The plant kingdom is divided into two subkingdoms:

Lower plants (Thallobionta);

Higher plants (Kormobionta).

Subkingdom "lower plants"

The lower plants include the most simply constructed representatives flora. The vegetative body of lower plants is not divided into organs (stem, leaf) and is represented by a thallus - called thallus .

Lower plants are characterized by the absence of complex internal differentiation; they do not have an anatomical and physiological system of tissues, like higher plants; the reproductive organs of lower plants are unicellular (with the exception of characeae and some brown algae. Lower plants include bacteria, algae, slime molds (myxomycetes), fungi, lichens.

Algae belong to the group of autotrophic organisms. Bacteria (with rare exceptions), myxomycetes and fungi are heterotrophic organisms that require ready-made organic matter. Both of them seem to complement each other.

Algae serve as the main producers of organic matter in water bodies. The decomposition of organic substances and their mineralization are carried out as a result of the activity of heterotrophic organisms: bacteria and fungi. Thanks to the processes of decomposition of organic matter, the atmosphere is replenished with carbon dioxide.

Some soil bacteria and blue-green algae are capable of fixing free atmospheric nitrogen. Thus, the biological cycle of substances performed by autotrophic and heterotrophic organisms is unthinkable without the activity of lower plants. In terms of their wide distribution in nature and in numbers, lower plants are superior to higher ones.

Subkingdom "higher plants"

Higher plants include organisms that have well-defined tissues, organs (vegetative: root and shoot, generative) and individual development(ontogenesis) of which is divided into embryonic (embryonic) and postembryonic (post-embryonic) periods.

Higher plants are divided into two groups:

Spores (Archegoniophyta);

Seeds (Spermatophyta).

Spore plants spread by spores. Reproduction requires water. Spore plants also called archegonial. The body of higher plants is differentiated into tissues and organs that appeared in them as one of the adaptations to life on land. The most important organs are root And the escape, dissected into stem and leaves. In addition, special tissues are formed in land plants: cover, conductive And main.

cover tissue performs protective function, protecting plants from unfavorable conditions. Through conductive fabric metabolism takes place between the underground and aboveground parts of the plant. Main fabric performs various functions: photosynthesis, support, storage, etc.

In all spore plants, in their life cycle of development, the alternation of generations is clearly expressed: sexual and asexual.

The sexual generation is the outgrowth, or gametophyte- formed from spores, has a haploid set of chromosomes. It performs the function of forming gametes (sex cells) in special organs of sexual reproduction; archegonia(from the Greek “arche” - beginning and “gone” - birth) - female genital organs and antheridia(from the Greek “anteros” - blooming) - male genital organs.

The sporangial tissue also has a double set of chromosomes; it divides by meiosis (division method), resulting in the development of spores - haploid cells with a single set of chromosomes. The generation name "sporophyte" means a plant that produces spores.

Spore plants are divided into the following sections:

Bryophyta (Bryophyta);

Lycophyta;

Horsetails (Sphenophyta);

Ferns (Pterophyta).

Seed plants spread by seeds. Water is not needed for reproduction.

Main differences between seed plants from higher disputes are as follows:

1. Seed plants produce seeds that serve for propagation. They are divided into two departments.

- angiosperms- plants that produce seeds enclosed in fruits.

2. In seed plants, further improvement in the life cycle and even greater dominance of the sporophyte and further reduction of the gametophyte are observed. The existence of the gametophyte in them is completely dependent on the sporophyte.

3. The sexual process is not associated with a droplet-liquid environment, and gametophytes develop and go through the full cycle of their development on the sporophyte. Due to the independence of the fertilization process from water, immobile male germ cells - sperm - arose, which reach female germ cells - eggs - with the help of special education- pollen tube.

In seed plants, the only mature megaspore remains permanently enclosed within the megasporangium, and here, inside the megasporangium, the development of the female gametophyte and the process of fertilization occur.

The megasporangium in seed plants is surrounded by a special protective cover called integument. The megasporangium with the surrounding integument is called the ovule. This is really the rudiment of the seed (ovule), from which the seed develops after fertilization.

Inside the ovule, the process of fertilization and development of the embryo occurs. This ensures the independence of fertilization from water, its autonomy.

During the development of the embryo, the ovule turns into a seed - the main unit of dispersal of seed plants. In the vast majority of seed plants, this transformation of the ovule into a mature seed ready for germination occurs on the mother plant itself.

Primitive seeds, for example, cycads, are characterized by the absence of a dormant period. Most seed plants are characterized by a more or less long period of dormancy. The rest period is long biological significance, because it makes it possible to survive unfavorable times of the year, and also contributes to more distant settlement.

Internal fertilization, the development of the embryo inside the ovule and the emergence of a new, extremely effective unit of dispersal - the seed - are the main biological advantages of seed plants, which gave them the opportunity to more fully adapt to terrestrial conditions and achieve higher development, higher spore plants.

Seeds, unlike spores, have not only a fully formed embryo of the future sporophyte, but also spare nutrients necessary in the first stages of its development. Dense shells protect the seed from unfavorable natural factors, destructive for most spores.

Thus, seed plants acquired serious advantages in the struggle for existence, which determined their flourishing during the drying climate. Currently, this is the dominant group of plants.

Seeds are divided into the following sections:

Angiosperms, or flowering plants (Magnoliophyta);

Let's look at them in more detail

Lower plants

In terms of their wide distribution in nature and in numbers, lower plants are superior to higher ones. As lower plants are studied, the scope of their use expands and their importance in human life increases.

The basis modern system plants, the following classification scheme for lower plants is based:

1. Department of Bacteria.

2. Department Blue-green algae.

3. Section Euglena algae.

4. Department of Green algae.

5. Division Characeae.

6. Department Pyrophytic algae.

7. Department of Golden algae.

8. Department Yellow-green algae.

9. Section Diatoms.

10. Department Brown algae.

11. Department Red algae.

12. Slime mold department.

13. Department of Mushrooms.

14. Department Lichens.

Algae – Algae

Algae belong to this subkingdom – the simplest in structure and the most ancient plants. This is an ecological heterogeneous group of phototrophic multicellular, colonial and unicellular organisms that often live in aquatic environments.

However, the world of algae is very diverse and numerous. Most of them live in or on the water. But there are algae that grow in the soil, on trees, on rocks and even in ice. Algae body – it is a thallus or thallus that has neither roots nor shoots. Algae do not have organs or various tissues; they absorb substances (water and mineral salts) over the entire surface of the body.

All types of algae are interconnected the following signs:

The presence of photoautotrophic nutrition and chlorophyll;

Lack of strict differentiation of the body into organs;

Well-defined conductive system;

Living in a humid environment;

Lack of cover.

Algae are distinguished by the number of cells:

- unicellular;

- multicellular (mainly filamentous);

- colonial;

- non-cellular.

There is also a difference in the cell structure and pigment composition of algae. In this regard, the following are highlighted:

- green(with a green tone and slight splashes of yellow);

- blue-green(with pigments of green, blue, red and yellow);

- brown(with green and brown pigments);

- red(with pigments various shades red);

- yellow-green(with coloring in corresponding tones, as well as two flagella of different structures and lengths);

- golden(with pigments that form a golden color, and cells that do not have a shell or are enclosed in a dense shell);

- diatoms(with a strong shell, consisting of two halves, and a brownish color);

- pyrrophytic(brownish-yellow in color with bare or shell-covered cells);

- Euglenaseaweed(unicellular, naked, with one or two flagella).

Algae reproduce in several ways:

- vegetative(by simple division of body cells);

- sexual(fusion of germ cells of a plant to form a zygote);

- asexual(zoospores).

Depending on the type of algae and how favorable the environmental conditions are, the number of generations in just a few years can exceed 1000.

All types of algae produce oxygen due to the presence of chlorophyll in their cells. Its share of the total volume produced by plants on planet Earth is 30-50%. By producing oxygen, algae absorb carbon dioxide, the percentage of which is quite high in the atmosphere today.

Algae also act as a source of food for many other living creatures. They feed on mollusks, crustaceans, different kinds fish Their high adaptability to harsh conditions provides high-quality nutrition for plants and animals high in the mountains, in polar regions, etc.

If there are too many algae in reservoirs, the water begins to bloom. A number of them, for example, blue-green algae, actively release a toxic substance during this period. Its concentration is especially high at the surface of the water. Gradually, this leads to the death of aquatic inhabitants and a significant deterioration in water quality, up to waterlogging.

Algae benefit not only flora and fauna. Humanity also actively uses them. The life activity of organisms in the past became modern generation source of minerals, the list of which includes oil shale and limestone.