Examples of a natural system for classifying living organisms. Animal classification

21.11.202327.05.2017

Systematics is a science that divides the animal and plant world into subordinate groups depending on their similarities or differences, and builds a system of the animal world. The emergence of systematics was caused by the need to navigate the diversity of animal forms. Initially, its task was purely practical and consisted of identifying organisms useful and harmful to humans (edible, inedible, poisonous, non-poisonous). From the moment of the emergence of Charles Darwin’s theory to the present day, the main purpose of taxonomy is the reflection of the historical relationship of existing forms.

The principles of systematics were developed by the Swedish naturalist C. Linnaeus (1707-1778) and outlined in the work “System of Nature” (1735). K. Linnaeus identified four systematic categories: species, genus, order and class. A species, according to K. Linnaeus, is the smallest systemic unit that unites organisms that are most similar to each other. Similar species are united into a genus, genera into an order, orders into a class, which represents the highest systematic unit. The entire animal world, according to K. Linnaeus, included only 6 classes: mammals, birds, reptiles, fish, insects and worms.

K. Linnaeus' system was artificial because it did not reflect the real historical relationship between organisms, since the division into groups was based on the formal similarity of individual characteristics.

Many classifications created in subsequent years were also artificial or largely formal. The modern animal system is the result of a long development of biological sciences. It is natural and reflects real phylogenetic relationships between groups of organisms, since the classification is based on a set of characteristics of organisms.

The system of subordinate groups of modern classification includes species (species), genus (genus), family (familia), order (ordo), class (classis) and type (typus). For some groups, intermediate groups, subtypes, suborders, and subfamilies are used. The number of species in the animal world is more than 2 million, types - over 20.

In taxonomy, a double, or binary, nomenclature was adopted, first introduced by C. Linnaeus. The essence of binary nomenclature is that each species has a double name. The first word means the name of the genus to which the species belongs, the second means the specific name itself. For example, the taiga tick is Ixodei persulcatus, the dog tick is Ixodes ricinus (the word Ixodes means the name of the genus, and persulcatus and ricinus are the names of the species). Binary nomenclature represents the generally accepted international system, which uses only Latin terminology. Thanks to this, mutual understanding between specialists from any country is possible. "

Chapter 16

PROTOZOTS

(MEDICAL PROTOZOOLOGY)

The type of protozoa (Protozoa) includes a number of forms that are pathogenic for humans, affecting individual tissues and organs and causing diseases of varying severity, including fatal ones.

Morphophysiological characteristics. In structure they correspond to an individual cell of multicellular organisms (hence the name “unicellular”), in function they correspond to a whole independent organism. The fundamental difference between protozoa and multicellular cells is the specialization of the latter, i.e. Each type of cell performs a single function in the body and therefore depends on the activity of other cells and cannot exist in isolation. In contrast, a single cell, which is a protozoan organism, moves, captures food, reproduces, defends itself from enemies, i.e., it has all the properties of the whole organism and physiologically corresponds to it. Therefore, protozoa are now called organisms at the cellular level. In the animal world, protozoa are represented by only one type.

The body of protozoa has microscopic dimensions and consists of the same components as a multicellular cell - the outer membrane, cytoplasm, nucleus and organelles.

The outer membrane has a typical three-layer structure, but due to additional formations in some species it can reach great thickness and density. The cytoplasm is divided into two layers: outer and inner. The outer layer (ectoplasm) is denser, homogeneous and transparent, the inner layer (endoplasm) is granular and has a more liquid consistency. The endoplasm contains general-purpose organelles - mitochondria, endoplasmic reticulum, reticular apparatus, etc. In addition, in accordance with the functions inherent in the whole organism, protozoa have special-purpose organelles that perform the functions of movement, blinking, excretion, protection, etc.

The organelles of protozoan movement are: 1) pseudopodia or stalks, which are temporary outgrowths of the cytoplasm;

flagella are permanent organelles that look like long thin moss, usually starting at the anterior end; 3) cilia - permanent organelles, which are numerous short filaments.

The structure of nutritional organelles is not the same and depends on the feeding method of different protozoa. Most protozoa feed on particles of solid food. In such organisms, to digest food, there is a digestive vacuole - a drop of liquid containing digestive enzymes, which is formed when food enters the endoplasm. The digestive vacuole surrounds the food particle and moves throughout the body of the protozoan. Food is digested and absorbed into the cytoplasm. The remains of undigested food along with the digestive vacuole are thrown out.

The excretory organelles are represented by a contractile or pulsating vacuole, which looks like a small bubble filled with liquid, which periodically increases, reaching a certain volume, and then contracts, throwing the liquid out. Accumulation and contraction alternate rhythmically. The main function of the contractile vacuole is to maintain osmotic pressure at a constant level. The concentration of mineral and organic substances, which determines the osmotic pressure, in the body of protozoa is higher than in the environment, therefore, according to the law of osmosis, water constantly enters the cytoplasm. If the water is not removed, the protozoan will swell and die.

Simultaneously with excess water, liquid dissimilation products are removed through the contractile vacuole and the cell is supplied with oxygen supplied with water.

Organoids of protection see 16. 4.

Most protozoa have a single nucleus, but multinucleate forms also exist. The nucleus has a structure characteristic of ukaryotes. The morphology and forms of nuclear division are varied, but, as has now been proven, nuclear division in any case represents mitosis.

Reproduction. Protozoa can reproduce asexually and sexually. Asexual reproduction occurs both in the form of divisions into two parts and in the form of multiple divisions. The sexual process of most protozoa is represented by copulation, in ciliates -1 by conjugation.

Life cycle. Unlike somatic cells* of multicellular organisms, the life cycle of protozoa consists of successive stages of development, which are repeated with a certain pattern. Most often the initial stage is; zygote, followed by asexual reproduction by division, then the formation of sexual individuals and again the formation of a zygote.

encystment. Under unfavorable environmental conditions (increase or decrease in temperature, drying out, etc.), vegetative forms of protozoa turn into cysts. They stop feeding, moving and become covered with a thick shell; Metabolic processes slow down sharply. When favorable conditions are restored, the active vegetative form emerges from the cyst again. Encystment is a protective reaction that arose during the process of evolution, ensuring survival in unfavorable conditions. Cysts can persist for a long time, months or even years.

Spreading. Protozoa live in fresh and sea water, liquid environments of organisms.

Classification. Currently, the classification of the type of protozoa is being revised. New classifications have appeared. Some authors (V.A. Dogel) distinguish protozoa as a kingdom! which is divided into 5 independent types: sarcomastigophora, sporozoans, cnidosporidia, microsporidia and ciliates. The generally accepted classification is according to which all protozoa are divided into 4 classes: 1. Class sarcodaceae; 2. Class flagella; 3. Classic sporozoans; 4. Class of ciliates;

16.1. CLASS SARCODA (5A1<СООША)

Morphophysiological characteristics. The most primitive protozoa, which manifest themselves primarily as a weak degree of differentiation. The cytoplasm is limited only by the outer membrane, the body shape is variable. Pseudopodia serve as organelles for movement and food capture. Special mouth! there is no hole. The intake of food and the excretion of undigested residues can occur in any part of the body. There is only one contractile vacuole. The release of dissimilation products and excess water can also occur anywhere. There is usually only one core, although multinucleate forms also occur.

Reproduction. Reproduction is mainly asexual - by dividing into two parts

encystment. Under unfavorable conditions they form a cyst.

Only one order of the subclass Roots is of medical importance, namely the order Amoebas (Amoebina).

16.1.1. Amoeba squad (Amoebina)

Several types of amoebas live in the human body. The most important is the dysenteric amoeba.

Dysenteric amoeba (Entamoeba histolytica). The causative agent of a severe disease - amoebic dysentery or amoebiasis.

Localization. Large intestine, v

Geographical distribution. Ubiquitous, but more common in hot climates.

Rice. 172. Dysenteric and intestinal amoebas.

Chnaenteric amoeba: a large vegetative form; b, c - small vegetative form: 1 - ectoplasm; 2 endoplasm; 3 - pseudopodia; 4 - core; 5 - karyoema; 6 - phagocytosed erythrocytes in digestive vacuoles; g - cyst; intestinal amoeba: A ~ - vegetative form; e - cyst.

Morphophysiological characteristics and

Rice. 173. Life cycle of dysenteric amoeba.

a - - healthy adult carriers] b ■ (amoebiasis; 1 cyst; 2 excised vegetative form; 1 small vegetative form, large vegetative form 1 ingested chrytropite."^ 5 in the intestinal tract; 6 7 excreted e feces out.

The invasive stage is a cyst containing 4 nuclei (a distinctive feature of the species). In the human intestine, the cyst shell dissolves and a quadruple amoeba emerges from it, which quickly divides into 4 mononuclear small (7-15 microns in diameter) vegetative forms (f. minuta).

A small vegetative form lives in the lumen of the large intestine, feeds mainly on bacteria, reproduces and causes diseases. When it enters the lower parts of the large intestine, it turns into a cyst, initially containing one nucleus, which, during maturation, divides to form a quadruple cyst.

In some people, under appropriate conditions (cooling (overheating, vitamin deficiencies, diet disorders, helminthiasis), formt minuta penetrates the intestinal walls, where it multiplies intensively and causes damage to the mucous membrane with the formation of ulcers. In this case, the walls of blood vessels are destroyed and bleeding occurs > intestinal cavity.

Etc and by the phenomenon of amoebic intestinal lesions, small vegetative "

Fig 173 continued

forms located in the intestinal lumen begin to transform into a large vegetative form. The latter is characterized by large size (30-40 microns) and the structure of the nucleus: the chromatin of the nucleus forms radial structures, a large lump of chromatin - the karyosome - is located strictly in the center, f-magna begins to feed on erythrocytes, i.e. it becomes eri trophage(Fig. 172). Characterized by blunt, wide pseudopodia and movement in jerks.

Amoebas that multiply in the tissues of the intestinal wall - the tissue form - enter the lumen and become similar in structure and size to the large vegetative form, but are not able to swallow red blood cells.

With treatment or an increase in the body's defense reaction, large 1yugetatt1vnaya-fosma_returns into small ones, which begin to become uncysted (risTTGZ). In the future, recovery occurs, or the disease becomes chronic.

In some infected people, the small vegetative form never develops into a large one. Such people are called cyst carriers. They pose a great danger as they serve as a source of infection for others. One cyst carrier releases up to 600 million cysts per day. Shchisto carrier and next to zha^ identification and mandatory treatment. |

The only source of amoebiasis is humans. Cysts released in feces contaminate soil and water. Since feces are often used as fertilizer, cysts end up in gardens and gardens, where they contaminate vegetables and fruits. Cysts are resistant to environmental influences. They enter the intestines with unwashed vegetables and fruits, through unboiled water, and dirty hands. Mechanica^^ kami_sdu2k at flies, cockroaches, for dirty food u.

Pathogenic disease with tTvTGe^ A severe disease develops, the main symptoms of which are: KpQB0T04j^Uie-ulcers ^ intestinal<е 1 _частый и жидкий стул (до 10-20 раз в сутки) с примесью кров^1Гслит иногдаТГОТфовёносньш сосудам дизентерийная амеба может заноситься в печень^and other^organs, call There is the formation of abscesses (focal ~ stagnoenia). In the absence of treatment, mortality reaches 2-40%._

Laboratory diagnostics. Microscopy of fecal smears. In the early period, the smear contains large, vegetative^Bo^mg, containing red blood cell y^; cysts are usually absent, since f. magna is unable to encyst. In case of chronic; form or cyst carriage, four are found in feces nuclear cysts. *""

Prevention: personal - washing vegetables and fruits with boiled water, drinking only boiled water, washing hands before eating, after using the toilet, etc.; public - combating soil and water contamination with feces, extermination of flies, sanitary educational work, examination for cyst carriage of persons working in public catering establishments, ] treatment of patients j.

Along with the dysenteric amoeba, the human digestive tract contains sarcode amoeba, which is non-pathogenic or whose pathogenicity has not been sufficiently proven. Knowledge of the morphophysiological characteristics of these amoebas is necessary, since some of them are similar to dysentery amoeba and can be mistaken for a pathogenic form.; In this regard, the doctor in some cases has to make a differential diagnosis between pathogenic and non-pathogenic types of amoebas. Non-pathogenic amoebae include intestinal and oral amoebae. Intestinal amoeba (Entamoeba coli).

Localization. The upper part of the colon, lives only in the intestinal lumen.

Geographical distribution. It is found in approximately 40-50% of the population in various regions of the globe.

Morphophysiological characteristics. The begetative form has dimensions of 20-40 µm, but sometimes larger forms are also found. There is no sharp boundary between ectoplasm and endoplasm. It has a characteristic method of movement - it simultaneously releases pseudopodia from different sides and, as it were, “marks time”. The nucleus contains large clumps of chromatin, the nucleolus lies eccentrically, and there is no radial structure. It does not secrete a proteolytic enzyme; it feeds on bacteria, fungi, and the remains of plant and animal food. The endoplasm contains many vacuoles. It does not swallow red blood cells, even if they are contained in large quantities in the intestines (in patients with bacterial dysentery). In the lower part of the digestive tract it forms eight- and two-core cysts.

Oral amoeba (Entamoeba gingival is).

Localization. Oral cavity, dental plaque in healthy people and those with oral diseases, dental caries.

Deo graphic distribution. Everywhere.

Morphophysiological characteristics. The vegetative form has dimensions from 10 to 30 µm, with highly vacuolated cytoplasm. The type of movement and structure of the nucleus resembles a dysentery amoeba. It does not swallow red blood cells; it feeds on bacteria and fungi. In addition, leukocyte nuclei or so-called salivary corpuscles are found in the vacuoles, which, after staining, may resemble red blood cells. It is believed that it does not form cysts. The pathogenic effect is currently denied. It is found in dental plaque of healthy people in 60-70%. It is more common in people with dental and oral diseases.

16.2. CLASS Flagellates (FLAGELLATA)

Flagellates include the largest number of forms pathogenic for humans.

Morphophysiological characteristics. They have microscopic dimensions. The body is oval, spherical or fusiform, covered, in addition to the outer membrane, with a thin shell - pellicle and retains a constant shape. Organelles of movement - flagella (1,2,4, 8 or more) - thin long outgrowths of the cytoplasm, which usually begin at the anterior end of the body. The flagellum consists of a free part extending beyond the body of the protozoan, and a section immersed in ectoplasm - the basal body or cylindrical kinetosome. In some flagellates (Leishmania, trypanosomes), at the base of the flagellum, in addition, a special organelle is placed - the kinetoplast. In terms of its ultrastructure, it corresponds to a mitochondrion, but is distinguished by a high DNA content. It is believed that energy is generated in the kinetoplast for the movement of the flagellum, which performs a rotational movement and seems to be screwed into the water. In some representatives of the class, the flagellum runs along the body, connecting to it with a thin outgrowth of the cytoplasm. The mentioned outgrowth, or undulating membrane, makes wave-like movements and serves as an additional organelle of movement.

Reproduction. Usually asexual, by longitudinal division into two parts. In some species, sexual reproduction occurs.

They live in fresh and sea water. Many forms are parasites of humans and animals.

16.2.1. Order Protomonadina Genus Leishmania

The most important are representatives of the genus Leishmania, which belongs to the Trypanosoma family.

A distinctive feature of the Trypanosome family is the ability to form several morphologically different forms during the development cycle, depending on the conditions of existence. Changes in form occur in both invertebrate and vertebrate hosts.

The following morphological forms are distinguished: trypanosomal, critidial, leptomonasal, leishmanial and metacyclic (Fig. 174).

The trypanosomal form is characterized by a flattened ribbon-like body, in the center of which there is an oval nucleus. The flagellum begins behind the nucleus. The axial filament of the flagellum goes to the anterior end of the body, forming a well-developed undulating membrane. At the anterior end of the body it ends, and the flagellum protrudes forward, forming a long free end.

In the critidial form, the flagellum begins slightly anterior to the nucleus, moving forward, forming a short undulating membrane and a free end.

In the leptomonad form, the flagellum begins at the very edge of the anterior end of the body, the undulating membrane is absent, and the free end of the flagellum is of considerable length.

The leishmanial form has a rounded shape and a large round nucleus. The rod-shaped kinetoplast is located at the anterior end of the body. The flagellum is either absent, or there is only its intracellular part; it does not extend beyond the body.

The metacyclic form is similar to the critidial one, but lacks a free flagellum.

Flagellates of the genus Leishmania have two morphological forms - leptomonas and leishmanial (Fig. 175) or intracellular.

Leishmanias are divided into dermatotropic (localized in the skin) and viscerotropic types (localized in the internal organs).

Rice. 174. Forms of the life cycle of ripanosomes I.

Inside cell shape

Extracellular forms

Leishmania (leptomonas form); b - leishmania (leishmanial form); c - fichomonas; g lamblia; I flagellum; 2 - core; 3 - kinetoplast; 4 - axoetil; 5 - undulating membrane; 6 - nucleus of a tissue cell affected by leishia.

[ - metacyclic (invasive); P - | rhinosomal; III - critidial; IV - leptomonas; V - leishmanial; 1 - core; 2 - undulating membrane; 3 - cystoplast; 4 - free end of the flagellum; D) - intracellular section of the flagellum; b - rod-shaped kinetoplast.

The causative agent of visceral leishmaniasis (Leischmania donovani).

Localization. Cells of the liver, spleen, bone marrow, lymph nodes, reticuloendothelial cells of subcutaneous tissue.

Geographical distribution. Mediterranean countries, Asia, a number of areas of tropical Africa and South America; in the USSR - Central Asia and Transcaucasia.

Morphophysiological characteristics. Leptomonas and leishmanial forms.

Life cycle. The reservoir is humans and various mammals (dogs, jackals). The carriers are small blood-sucking insects - mosquitoes of the genus Phlebotomus, which become infected by biting a sick person or animal. Leishiania enter the mosquito's digestive tract, where they undergo a very complex development cycle, then penetrate the salivary glands. A person becomes infected through a mosquito bite. Leishmania (leptomonas form) quickly penetrates from the blood and lymph into the cells of internal organs, where

Recently, it was discovered that Leishmania is also found in the reticuloendothelial cells of the skin, which explains the method of infection of mosquitoes. The affected cells sometimes form a continuous layer or are concentrated near the sweat glands and blood vessels.

Pathogenic effect. There is an irregular, persistent fever. The spleen and liver gradually increase and can reach enormous sizes (Fig. 176). Exhaustion and anemia develop. The disease can be acute or take a chronic course (1-3 years). The mortality rate is very high. Mostly children get sick. ,

Prevention: personal - individual protection against mosquito bites; public - destruction of reservoirs (stray dogs, jackals). At the same time, it is necessary to carry out mosquito control, sanitary education, and treatment of patients.

Pathogens of cutaneous leishmaniasis (Leishmania tropica).

Three subspecies of the dermatotropic species of Leishmania are known: L. tropica minor and L. tropica major (in the eastern hemisphere) and L. tropica mexicana (in the western hemisphere). Localization. Skin cells.

Geographical distribution. Widely distributed in a number of countries in Europe, Asia, America, and Africa. I! USSR - in Central Asia and Transcaucasia.

Morphophysiological characteristics. Leptomonas and leishmanial fbrms are indistinguishable from the forms of scerotropic leishmania.

Life cycle. Almost no different from the causative agent of visceral leishmaniasis. The source of infection is humans and wild animals (small rodents living in sandy semi-deserts and deserts - gerbils, gophers, hamsters, some types of rats and mice). Infection in animal reservoirs under natural conditions sometimes reaches 70%. The disease in animals also manifests itself in the form of skin ulcers. Mosquitoes serve as carriers. There is close contact between reservoir rodents and mosquito vectors. The time of the rodent is a permanent habitat and breeding place for mosquitoes, the infestation of which can reach 35%. The role of humans in the spread of cutaneous leishmaniasis is small, with the exception of some areas of the globe (India).

Pathogenic effect. Causes the formation of long-term (about a year) non-healing ulcers on open parts of the body; after healing, a disfiguring scar remains (Fig. 177).

Laboratory diagnostics. Microscopic examination of discharge from ulcers.

Prevention: personal - individual protection against mosquito bites; public - fight against mosquitoes, destruction of natural reservoirs; in particular, the destruction of rodents in areas adjacent to settlements. It is recommended to carry out preventive vaccinations of cutaneous leishmaniasis strains from animals on closed areas of the skin.

16.2.2. Order Polymastigina

Intestinal trichomonas (Trichomonas hominis). Causes intestinal trichomoniasis.

Localization. Colon.

Geographical distribution. Everywhere.

Morphophysiological characteristics. The body is oval in shape with a pointed outgrowth at the posterior end. The length of the body is 5-15 µm, 4 free flagella extend from the anterior end, extending forward, and one directed backward, which is connected to the undulating membrane; a supporting rod passes through the middle, the end of which protrudes at the posterior end of the body. The cell mouth is located near the nucleus. In the cytoplasm there are digestive vacuoles that serve to digest bacteria and intestinal contents. Osmotic nutrition is also possible. Reproduction is asexual, by longitudinal division. The ability to form cysts is disputed.

A person becomes infected through contaminated vegetables and fruits, dirty hands, and unboiled water.

Pathogenic effect. It has not been proven; there is an opinion that intestinal Trichomonas does not cause disease, but only accompanies pathological processes caused by other reasons. It is also found in healthy people.

Laboratory diagnostics. Microscopic examination of fecal smears.

Prevention. The same as for amoebiasis.

Urogenital trichomonas (Trichomonas vaginalis). Localization. Genitourinary tract of men and women.

Geographical distribution. Everywhere.

Morphophysiological characteristics. Its structure is very similar to intestinal Trichomonas. Distinctive features are the large size of the body (length ranges from 7 to 30 microns) and the presence of a longer spine at the posterior end of the body.

Pathogenic effect. Causes inflammatory processes that are protracted. It is believed that the predisposing factor for the manifestation of pathogenicity is the presence of a certain type of bacteria in the genital tract.

In women, the vagina is initially affected, but subsequently the disease becomes multifocal. Acute cases are characterized by copious fluid discharge, itching and burning. In men, the disease is mostly asymptomatic.

Infection occurs through sexual contact, as well as through the use of bedding, linen, and sponges of the patient. Infection is possible during examination by a gynecologist through contaminated instruments and gloves.

Laboratory diagnostics. Microscopic examination of smears from the discharge of the genitourinary tract.

Prevention. Determined by the method of infection.

Giardia (Lamblia intestinalis). The disease causes giardiasis.

Localization. Twenty-tipdzsgvats__ gut, can penetrate into the bile ducts for the second time.

G e o F r~a~f-i- h e- skoe distribution. Everywhere.

Laboratory diagnostics. Detection of cysts in feces or vegetative forms in the contents of the duodenum during probing.

Prevention. The same as for other intestinal diseases caused by protozoa.

16.3. CLASS SPOROZOA

Life cycle. Complex is different! yo, often with a change of hosts and alternation of asexual reproduction, sexual and sporogony. Asexual reproduction occurs in the form of schizogony, or multiple fission. The final stage of development is the formation of spores and sporozoites.

16.3.1 Order Blood sporozoans (Haemosporidia)

Life cycle. 1. Preerythrocygaric schizogony. Plasmodium reaches a person through the bite of an infected mosquito, which injects narrow crescent-shaped sporozoites into the human blood with saliva. With the blood flow, they are carried throughout the body and penetrate into the liver cells, where they acquire a rounded shape, grow and turn into the schizont stage. After some time, schizonts begin to reproduce through multiple fission or schizogony. The schizont nucleus divides many times, then a section of cytoplasm separates near each nucleus and the schizont breaks up into a large number of mononuclear merozoites (1000-5000 individuals, depending on the type of plasmodium). This process is called preerythrocytic, or tissue schizogony. When the liver cell is destroyed, the resulting merozoites leave it and pass into the bloodstream, where they penetrate into red blood cells (Fig. 178, see color on). In all plasmodia pathogenic to humans, the preerythrocyte cycle occurs once.

Scheme of subordination of animal groups

Animal taxonomy is a science that deals with the distribution of animals into groups - types, classes, orders, genera.

The Animal Kingdom is usually divided into a number of systematic units, the main of which is the species. In zoology, as in botany, species similar in characteristics and close in origin are combined into a genus, genera into a family, families into an order, orders into a class, classes into a phylum.

The diagram below shows the subordination of systematic groups (taxa) of animals. The highest taxon is the kingdom, the lowest is the species.

Classification Kingdom Animals

In the animal kingdom, there are subkingdoms of unicellular (protozoa) and multicellular animals. The subkingdom Unicellular includes the phyla Sarcoflagellates, Apicomplexans and Ciliates. The subkingdom Metazoans contains the following phyla: molluscs, chordates, coelenterates, echinoderms, arthropods, flatworms, roundworms and annelids. The diagram below shows the complete classification of Kingdom Animals.

Comparison of plants and animals

PLANTS	ANIMALS
Similarities
1. Cellular structure. 2. Nutrition. 3. Breathing. 4. Selection. 5. Reproduction. 6. Irritability (the ability to respond to changes in external
Differences
1. Autotrophic nutrition (formation of organic substances from inorganic ones). 2. Less irritability.	1. Heterotrophic nutrition (ready-made organic substances). 2. More irritability.

_______________

A source of information: Biology in tables and diagrams./ Edition 2, - St. Petersburg: 2004.

Currently, the organic world of the Earth has about 1.5 million animal species, 0.5 million plant species, and about 10 million microorganisms. It is impossible to study such a diversity of organisms without systematizing and classifying them.

The Swedish naturalist Carl Linnaeus (1707-1778) made a great contribution to the creation of the taxonomy of living organisms. He based the classification of organisms on principle of hierarchy, or subordination, and took as the smallest systematic unit view. For the name of the species it was proposed binary nomenclature, according to which each organism was identified (named) by its genus and species. It was proposed to give the names of systematic taxa in Latin. So, for example, the domestic cat has a systematic name Felis domestica. The foundations of Linnaean systematics have been preserved to the present day.

Modern classification reflects evolutionary relationships and family ties between organisms. The principle of hierarchy is preserved.

View- this is a collection of individuals that are similar in structure, have the same set of chromosomes and a common origin, interbreed freely and produce fertile offspring, adapted to similar living conditions and occupy a certain area.

Currently, nine main systematic categories are used in taxonomy: empire, superkingdom, kingdom, phylum, class, order, family, genus, species (Scheme 1, Table 4, Fig. 57).

Based on the presence of a designed kernel, everything cellular organisms are divided into two groups: prokaryotes and eukaryotes.

Prokaryotes(nuclear-free organisms) - primitive organisms that do not have a clearly defined nucleus. In such cells, only the nuclear zone containing the DNA molecule is distinguished. In addition, prokaryotic cells lack many organelles. They only have an outer cell membrane and ribosomes. Prokaryotes include bacteria.

Eukaryotes- truly nuclear organisms, have a clearly defined nucleus and all the main structural components of the cell. These include plants, animals, and fungi.

Table 4

Examples of classification of organisms

In addition to organisms that have a cellular structure, there are also non-cellular life forms - viruses And bacteriophages. These forms of life represent a kind of transitional group between living and inanimate nature.

Rice. 57. Modern biological system

* The column represents only some, but not all, existing systematic categories (phyla, classes, orders, families, genera, species).

Viruses were discovered in 1892 by Russian scientist D.I. Ivanovsky. Translated, the word “virus” means “poison”.

Viruses consist of DNA or RNA molecules covered with a protein shell, and sometimes additionally with a lipid membrane (Fig. 58).

Rice. 58. HIV virus (A) and bacteriophage (B)

Viruses can exist in the form of crystals. In this state, they do not reproduce, do not show any signs of being alive, and can persist for a long time. But when introduced into a living cell, the virus begins to multiply, suppressing and destroying all structures of the host cell.

Penetrating into a cell, the virus integrates its genetic apparatus (DNA or RNA) into the genetic apparatus of the host cell, and the synthesis of viral proteins and nucleic acids begins. Viral particles are assembled in the host cell. Outside a living cell, viruses are not capable of reproduction and protein synthesis.

Viruses cause various diseases of plants, animals, and humans. These include tobacco mosaic viruses, influenza, measles, smallpox, polio, human immunodeficiency virus (HIV), defiant AIDS disease.

The genetic material of the HIV virus is presented in the form of two RNA molecules and a specific reverse transcriptase enzyme, which catalyzes the reaction of viral DNA synthesis on the viral RNA matrix in human lymphocyte cells. Next, the viral DNA is integrated into the DNA of human cells. In this state it can remain for a long time without manifesting itself. Therefore, antibodies in the blood of an infected person are not immediately formed and it is difficult to detect the disease at this stage. During the process of blood cell division, the DNA of the virus is passed on to the daughter cells.

Under any conditions, the virus is activated and the synthesis of viral proteins begins, and antibodies appear in the blood. The virus primarily affects T-lymphocytes, which are responsible for producing immunity. Lymphocytes stop recognizing foreign bacteria and proteins and producing antibodies against them. As a result, the body stops fighting any infection, and a person may die from any infectious disease.

Bacteriophages are viruses that infect bacterial cells (bacteria eaters). The body of the bacteriophage (see Fig. 58) consists of a protein head, in the center of which there is viral DNA, and a tail. At the end of the tail there are tail processes that serve to attach to the surface of the bacterial cell and an enzyme that destroys the bacterial wall.

Through a channel in the tail, the DNA of the virus is injected into the bacterial cell and suppresses the synthesis of bacterial proteins, instead of which DNA and viral proteins are synthesized. In the cell, new viruses are assembled, which leave the dead bacterium and invade new cells. Bacteriophages can be used as medicines against pathogens of infectious diseases (cholera, typhoid fever).

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8. Diversity of the organic world§ 51. Bacteria. Mushrooms. Lichens

Taxonomy

SYSTEMATICS -And; and.

1. Specialist. Classification, grouping of objects, phenomena. C. isotopes. C. crystals.

2. A department of botany or zoology that deals with the description and classification of existing and extinct animals and plants into species, genera, families, etc. S. plants. S. birds.

taxonomy

(biol.), the science of the diversity of all existing and extinct organisms, of the relationships and relationships between their various groups (taxa) - populations, species, genera, families, etc. The main tasks of taxonomy are to determine by comparison the specific features of each species and each taxon of a higher rank, clarifying the general properties of certain taxa. In an effort to create a complete system (classification) of the organic world, taxonomy is based on the evolutionary principle and data from all biological disciplines. By determining the place of organisms in the system of the organic world, taxonomy has important theoretical and practical significance, allowing one to navigate the huge diversity of living beings. The foundations of taxonomy were laid by the works of J. Ray (1693) and C. Linnaeus (1735).

SYSTEMATICS

SYSTEMATICS, in biology, is the science of the diversity of all existing and extinct organisms, the relationships and relationships between their different groups (taxa) - populations, species, genera, families, etc. The main tasks of taxonomy are to determine, by comparing, the specific features of each species and each taxon of a higher rank, and to clarify the general properties of certain taxa. In an effort to create a complete system (classification) of the organic world, taxonomy is based on the evolutionary principle and data from all biological disciplines. By determining the place of organisms in the system of the organic world, taxonomy has important theoretical and practical significance, allowing one to navigate the huge variety of living beings. The foundations of taxonomy were laid by the works of J. Ray (1693) and C. Linnaeus (cm. LINNEAUS Karl) (1735).

encyclopedic Dictionary. 2009 .

Synonyms:

See what “systematics” is in other dictionaries:

- (from the Greek sistematikos - ordered) the science and art of systematization. Systematic – presented in the form of a specific system, forming a specific system. Philosophical encyclopedic dictionary. 2010. SI... Philosophical Encyclopedia

Scientific explanation of systems. Dictionary of foreign words included in the Russian language. Chudinov A.N., 1910. SYSTEMATICS grouping something according to similar characteristics, arrangement according to one specific plan, for example, in botany p. plants,... ... Dictionary of foreign words of the Russian language

- (biological), the science of the diversity of all existing and extinct organisms, the relationships and relationships between their various groups (taxa), populations, species, genera, families, etc. Striving to create a complete system... ... Modern encyclopedia

In biology, the science of the diversity of all existing and extinct organisms, the relationships and relationships between their various groups (taxa), populations, species, genera, families, etc. The main tasks of taxonomy are definition... ... Big Encyclopedic Dictionary

SYSTEMATICS, systematics, women. (scientific). 1. units only Bringing into a system, classification and grouping of objects and phenomena. Do taxonomy. 2. A department of botany or zoology devoted to such classification. Systematics of plants... ... Ushakov's Explanatory Dictionary

Noun classification classification systematization systematization grouping grouping Dictionary of Russian synonyms. Context 5.0 Informatics. 2012. taxonomy… Synonym dictionary

The biological science of the diversity, classification of organisms and the relationships among them. The first attempts to classify the organic world were made by Aristotle (384,322 BC) and Theophrastus (372,287 BC). Life forms of plants according to... ... Ecological dictionary

taxonomy- and, f. systemmatique, German Systematik gr. 1. A department of botany or zoology concerned with the classification and description of extinct and extant plants or animals. BAS 1. 2. Grouping, classification of objects and phenomena. Systematics of isotopes. ALS... Historical Dictionary of Gallicisms of the Russian Language

SYSTEMATICS, and, female. Bringing into the system (in 1 value) what no., as well as the systemic classification of whom what no. S. plants. C. animals. Ozhegov's explanatory dictionary. S.I. Ozhegov, N.Yu. Shvedova. 1949 1992 … Ozhegov's Explanatory Dictionary

- (from the Greek systematikos, ordered, relating to the system), a section of biology, the task of which is to describe and designate all existing and extinct organisms, as well as their classification into taxa (groupings) of various types. rank. Relying on the… … Biological encyclopedic dictionary

A section of biology, the task of which is to describe and designate all existing and extinct organisms, as well as their classification into taxa (groups) of various ranks. The special significance of S. is to create the possibility of orientation in... ... Dictionary of microbiology

Books

Taxonomy of Mammals, V. E. Sokolov, The book represents the first attempt in the domestic literature to provide a taxonomic summary of modern mammals belonging to the orders of monotremes, marsupials, insectivores, woolly wings, ... Category: Zoology Publisher: Higher School,
Taxonomy of flowering plants, Goncharov M., Povydysh M., Yakovlev G., The textbook “Systematics of Flowering Plants” provides information on the modern taxonomy of flowering plants based on molecular phylogenetic data, characterizes... Category:

8. DIVERSITY OF THE ORGANIC WORLD

§ 50. System of classification of living organisms

The Swedish naturalist Carl Linnaeus (1707–1778) made a great contribution to the creation of the taxonomy of living organisms. He based the classification of organisms on principle of hierarchy, or subordination, and took as the smallest systematic unit view. For the name of the species it was proposed binary nomenclature, according to which each organism was identified (named) by its genus and species. It was proposed to give the names of systematic taxa in Latin. So, for example, the domestic cat has a systematic name Felis domestica. The foundations of Linnaean systematics have been preserved to the present day.

Modern classification reflects evolutionary relationships and family ties between organisms. The principle of hierarchy is preserved.

View- this is a collection of individuals that are similar in structure, have the same set of chromosomes and a common origin, interbreed freely and produce fertile offspring, adapted to similar living conditions and occupy a certain area.

Currently, nine main systematic categories are used in taxonomy: empire, superkingdom, kingdom, phylum, class, order, family, genus, species (Scheme 1, Table 4, Fig. 57).

Based on the presence of a designed kernel, everything cellular organisms are divided into two groups: prokaryotes and eukaryotes.

Prokaryotes(nuclear-free organisms) are primitive organisms that do not have a clearly defined nucleus. In such cells, only the nuclear zone containing the DNA molecule is distinguished. In addition, prokaryotic cells lack many organelles. They only have an outer cell membrane and ribosomes. Prokaryotes include bacteria.

Eukaryotes– truly nuclear organisms, have a clearly defined nucleus and all the main structural components of the cell. These include plants, animals, and fungi.

Table 4

Examples of classification of organisms

In addition to organisms that have a cellular structure, there are also non-cellular life forms – viruses And bacteriophages. These life forms represent a kind of transitional group between living and inanimate nature.

Rice. 57. Modern biological system

* The column represents only some, but not all, existing systematic categories (phyla, classes, orders, families, genera, species).

Viruses were discovered in 1892 by Russian scientist D.I. Ivanovsky. Translated, the word “virus” means “poison”.

Viruses consist of DNA or RNA molecules covered with a protein shell, and sometimes additionally with a lipid membrane (Fig. 58).

Rice. 58. HIV virus (A) and bacteriophage (B)

§ 51. Bacteria. Mushrooms. Lichens

Bacteria. These are single-celled prokaryotic organisms. Their size ranges from 0.5 to 10–13 microns. Bacteria were first observed under a microscope by Anthony van Leeuwenhoek in the 17th century.

A bacterial cell has a membrane (cell wall) similar to a plant cell. But in bacteria it is elastic, non-cellulose. Under the shell there is a cell membrane, which ensures the selective flow of substances into the cell. It protrudes into the cytoplasm, increasing the surface of membrane formations on which many metabolic reactions take place. A significant difference between a bacterial cell and the cells of other organisms is the absence of a formed nucleus. In the nuclear zone there is a circular DNA molecule, which is the carrier of genetic information and regulates all life processes of the cell. Of the other organelles in bacterial cells, only ribosomes are present, on which protein synthesis occurs. Prokaryotes lack all other organelles.

Rice. 59. Various forms of bacteria

The shape of bacteria is very diverse and forms the basis of their classification (Fig. 59). These are spherical - cocci, rod-shaped – bacilli, curved – vibrios, twisted – spirilla And spirochetes. Some bacteria have flagella that help them move. Bacteria reproduce by simply dividing a cell into two. Under favorable conditions, a bacterial cell divides every 20 minutes. If conditions are unfavorable, further proliferation of the bacterial colony is stopped or slowed down. Bacteria do not tolerate low and high temperatures well: when heated to 80 °C, many die, and some, under unfavorable conditions, form disputes– resting stages, covered with a dense shell. In this state they remain viable for quite a long time, sometimes several years. Some bacterial spores can withstand freezing and temperatures up to 129°C. Sporulation is characteristic of bacilli, for example, the causative agents of anthrax and tuberculosis.

Bacteria live everywhere - in soil, water, air, in the bodies of plants, animals and humans. Many bacteria according to the way they feed are heterotrophic organisms, i.e., they use ready-made organic substances. Some of them, being saprophytes, destroys the remains of dead plants and animals, participates in the decomposition of manure, and promotes soil mineralization. Bacterial processes of alcoholic and lactic acid fermentation are used by humans. There are species that can live in the human body without causing harm. For example, E. coli lives in the human intestines. Certain types of bacteria, settling on food products, cause their spoilage. Saprophytes include bacteria of decay and fermentation.

In addition to heterotrophs, there are also autotrophic bacteria that can oxidize inorganic substances and use the released energy for the synthesis of organic substances. For example, soil azotobacteria enrich it with nitrogen, increasing fertility. On the roots of leguminous plants - clover, lupine, peas - you can see nodules containing such bacteria. Autotrophs include sulfur bacteria and iron bacteria.

Another group of microorganisms belongs to prokaryotes - cyanobacteria. Cyanobacteria are autotrophs, have a photosynthetic system and the corresponding pigments. That's why they are green or blue-green in color. Cyanobacteria can be solitary, colonial, or filamentous (multicellular).

They are similar in appearance to algae. Cyanobacteria are common in water, soil, hot springs, and are part of lichens.

Mushrooms. This is a group of heterotrophic organisms that has characteristics similar to plants and animals.

Like plants, fungi have a cell wall, unlimited growth, they are immobile, reproduce by spores, and feed by absorbing nutrients dissolved in water.

Like animals, fungi are not able to synthesize organic substances from inorganic ones, do not have plastids and photosynthetic pigments, accumulate glycogen rather than starch as a reserve nutrient, and the cell membrane is built from chitin, not cellulose.

That is why mushrooms are classified into a separate kingdom. The kingdom of mushrooms unites about 100 thousand species that are widespread on Earth.

Rice. 60. Structure of mushrooms: 1 – mucor; 2 – yeast; 3 – penicillium

Mushroom body (Fig. 60) – thallus consists of thin threads - hyphae. A collection of hyphae is called mycelium or mycelium. Hyphae may have septa, forming individual cells. But in some cases there are no partitions (in mucor). Therefore, fungal cells can contain one or many nuclei.

The mycelium develops on the substrate, while the hyphae penetrate into the substrate and grow, branching repeatedly. Mushrooms reproduce vegetatively - by parts of mycelium and spores that mature in specialized cells - sporangia.

Mushrooms are divided into two classes: lower and higher mushrooms.

1. Lower mushrooms often have multinucleate mycelium or consist of a single cell. Representatives of lower fungi are mold fungi: mucor, penicillium, aspergillus. In penicillium, unlike mucor, the mycelium is multicellular, divided into partitions. Molds develop in the soil, on wet foods, in fruits and vegetables, causing them to spoil. One part of the fungal hyphae penetrates into the substrate, and the other part rises above the surface. Spores mature at the ends of vertical hyphae.

Yeast - These are lower unicellular fungi. Yeast does not form mycelium and reproduces by budding. They cause alcoholic fermentation, decomposing sugar in the process of their life activity. They are used in brewing, baking, and winemaking.

2. TO higher mushrooms relate cap mushrooms. They are characterized by multicellular mycelium, which develops in the soil and forms on the surface. fruiting bodies, consisting of tightly intertwined hyphae in which spores mature. The fruiting bodies consist of a stem and a cap. In some mushrooms, the lower layer of the cap is formed by radially arranged plates - this is lamellar mushrooms. These include russula, chanterelles, champignons, toadstool, etc. Other mushrooms have numerous tubes on the underside of the cap - these are tubular mushrooms. These include porcini mushroom, boletus, boletus, fly agaric, etc. Fungal spores ripen in tubes and on plates. Often the mycelium of the fungus forms mycorrhiza, growing by hyphae into plant roots. The plant supplies the fungus with organic nutrients, and the fungus provides mineral nutrition to the plant. Such mutually beneficial cohabitation is called symbiosis. Many cap mushrooms are edible, but some are poisonous.

1. Saprophytic mushrooms they feed on dead organisms, organic residues, food products, and ripened fruits, causing them to rot and decay. Saprophytes include mucor, penicillium, aspergillus, and most cap mushrooms.

Fungi, along with bacteria, play an important role in the cycle of substances in the biosphere. They decompose organic substances, mineralize them, and participate in the formation of a fertile soil layer - humus. The importance of mushrooms in human life is also great. In addition to being used as food, medicines are obtained from mushrooms - antibiotics (penicillin), vitamins, plant growth substances (gibberellin), enzymes.

Lichens. This is a unique group of organisms, representing a symbiosis of a fungus and unicellular algae or cyanobacteria. The fungus protects the algae from drying out and supplies it with water. And algae and cyanobacteria, through the process of photosynthesis, form organic substances that the fungus feeds on.

Lichen body - thallus (thallus) consists of fungal hyphae, among which are unicellular algae. The surface layer of lichen is formed by densely woven hyphae, and the lower ones are more sparse. Green algae are located among the sparse network of hyphae.

Such structural features of the lichen allow it not only to receive nutrition from the soil, but also to capture moisture and dust particles that settle on the thallus from the air. Therefore, lichens have a unique feature - they can exist in the most unfavorable conditions, settling on bare rocks and stones, tree bark, and house roofs. They are called “pioneers” of soil formation, since, by “inhabiting” rocks, they create conditions for the subsequent settlement of plants. The only necessary condition for the life of lichens is clean air. Therefore, they serve as indicators of the degree of air pollution.

Lichens reproduce vegetatively - by parts of the thallus and algae cells. They grow very slowly.

Based on their appearance, lichens are divided into three groups: crustose (scale), leafy and bushy (Fig. 61).

crustose lichens The thallus adheres tightly to the substrate, from which they cannot be separated. They are completely satisfied with a small amount of water that falls in the form of precipitation or is in the atmosphere in the form of vapor. They settle on tree trunks and stones.

Rice. 61. Lichens: A – structure (1 – green algae cells; 2 – fungal hyphae); B – variety: 2 – cortical, 3 – leafy, 4 – bushy

Xanthoria – Wall goldenrod is often found on aspen bark, board fences and roofs. Parmelia – a lichen with large lobes of gray-blue color, lives on the bark of pine trees and dead branches of spruce.

Foliose lichens can be found on the bark of trees, soil where there is no grass. They are attached to the substrate with the help of thin outgrowths of the thallus.

Peltigera – a gray-green lichen with black veins below, growing on the soil in damp places.

Fruticose lichens have a highly branched thallus. They grow mainly on soil, stumps, and tree trunks. They are attached to the substrate only by the base.

Iceland moss- a gray-yellow lichen with strongly curved narrow outgrowths of the thallus. Contains a lot of vitamin C, used for scurvy in the North. Reindeer moss, or reindeer moss, occupies large spaces in the tundra and serves as the main food for reindeer. These are graceful bushes consisting of thin, highly branched stems. When dry, it becomes brittle and crunches underfoot. It also grows in dry pine forests. Krasnogolovka– gray-green small, 3 cm, tubes, with a red edge or balls (heads) along the edge. Grows on old stumps. bearded man forms long hanging clumps, settling on trees in humid forests, most often on spruce trees.

Being autoheterotrophs, lichens create organic substances through the process of photosynthesis in places inaccessible to other organisms. At the same time, they mineralize organic matter, thereby participating in the cycle of substances in nature and playing an important role in soil formation.

§ 52. Plants, their structure. Vegetative organs

Plants are photosynthetic living organisms that belong to eukaryotes. They have a cellulose cell wall, a storage nutrient in the form of starch, are inactive or immobile and grow throughout life.

The science that studies the structure and vital activity of plants, their taxonomy, ecology and distribution is called botany(from Greek botane – grass, greenery and logos – teaching).

Plants make up the bulk of the biosphere, forming the green cover of the Earth. They live in various conditions - water, soil, ground-air environment, and occupy the entire landmass of our planet, with the exception of the ice deserts of the Arctic and Antarctica.

Life forms of plants.Trees characterized by the presence of a lignified stem - a trunk that persists throughout life. Shrubs have several small stems. For herbs characterized by juicy, green, non-lignified shoots.

Lifespan. Distinguish annual, biennial, perennial plants. Trees and shrubs are perennial plants, and herbs can be perennial, annual or biennial.

The structure of plants. The body of plants is usually divided into root And the escape. Of the higher plants, the most highly organized, numerous and widespread are flowering plants. In addition to roots and shoots, they have flowers and fruits - organs that are absent in other groups of plants. It is convenient to consider the structure of plants using the example of flowering plants. The vegetative organs of plants, roots and shoots, provide their nutrition, growth and asexual reproduction.

Rice. 62. Types of root systems: 1 – taproot; 2 – fibrous; 3 – cone-shaped parsley root; 4 – beetroot; 5 – dahlia root cones

With the help of the root (Fig. 62), the plant is anchored in the soil. It also provides water and minerals and often serves as a site for the synthesis and storage of nutrients.

Roots begin to form already in the embryo of the plant. When a seed germinates from the embryonic root, it forms main root. After some time, numerous lateral roots. In a number of plants, stems and leaves produce adventitious roots.

The set of all roots is called root system. The root system can be core, with a well-developed main root (dandelion, radish, apple tree) or fibrous, formed by lateral and adventitious roots (barley, wheat, onion). The main root in such systems is poorly developed or completely absent.

A number of plants store nutrients (starch, sugar) in their roots, for example, carrots, turnips, and beets. Such modifications of the main root are called root vegetables. In dahlias, nutrients are deposited in thickened adventitious roots, they are called root tubers. Other modifications of roots are also found in nature: root-trailers(in vines, ivy), aerial roots(in monstera, orchids), stilted roots(in mangrove plants - banyan), respiratory roots(in marsh plants).

The root grows with the apex where the cells are located educational tissue is a growth point. She's protected root cap. Root hairs absorb water with dissolved minerals into suction zone. By conducting system From the roots, water and minerals move up to the stems and leaves, and organic matter moves down.

The escape is a complex vegetative organ consisting of buds, stems and leaves. Along with vegetative shoots, flowering plants have generative shoots on which flowers develop.

The shoot is formed from the embryonic bud of the seed. The development of shoots of perennial plants from the buds is clearly visible in the spring.

Based on the location of the buds on the stem, they are distinguished apical And lateral buds. The apical bud ensures the growth of the shoot in length, and the lateral buds ensure its branching. The outside of the bud is covered with dense scales, often impregnated with resinous substances; inside there is a rudimentary shoot with a growth cone and leaves. In the axils of the rudimentary leaves there are barely noticeable rudimentary buds. The generative bud contains the primordia of flowers.

Stem– this is the axial part of the shoot on which the leaves and buds are located. It performs a supporting function in the plant, ensures the movement of water and minerals from the root up to the leaves, and organic substances - down, from the leaves to the root.

Externally, the stems are very diverse: those of corn, sunflower, and birch are erect; in wheatgrass and cinquefoil - creeping; in bindweed and hops – curly; peas, vines, and grapes have climbing ones.

The internal structure of the stem is different in monocotyledonous and dicotyledonous plants (Fig. 63).

Rice. 63. Internal structure of the stem. Cross section: 1 – corn stalk (vascular bundles are located throughout the stalk); 2 – linden branches

1. U dicotyledonous plant the stem is covered with skin on the outside - epidermis, in perennial woody stems the skin is replaced cork. Under the cork there is a bast formed by sieve tubes that ensure the movement of organic substances along the stem. Bast mechanical fibers give strength to the stem. Cork and bast form bark

To the center of the bast is cambium- a single layer of educational tissue cells that ensures the growth of the stem in thickness. Below it is located wood with vessels and mechanical fibers. Water and mineral salts move through the vessels, and the fibers give the wood strength. When wood grows, it forms tree rings, by which the age of the tree is determined.

In the center of the stem is located core. It performs a storage function; organic substances are deposited in it.

2. U monocots the stem is not divided into bark, wood and pith; they lack a cambial ring. Conducting bundles, consisting of vessels and sieve tubes, are evenly distributed throughout the stem. For example, in cereals the stem is a straw, hollow inside, and the vascular bundles are located along the periphery.

A number of plants have modified stems: spines in hawthorn, serving for protection; mustache in grapes - for attachment to a support.

Sheet- This is an important vegetative organ of the plant, performing the main functions: photosynthesis, water evaporation and gas exchange.

Plants have several types of leaf arrangement: next, when the leaves are arranged alternately one after another, opposite– the leaves are located opposite each other and whorled– three or more leaves extend from one node (Fig. 64).

Rice. 64. Leaf arrangement: 1 – alternate; 2 – opposite; 3 – whorled

The sheet consists of leaf blade And petiole, sometimes stipules are present. Leaves without a petiole are called sedentary. In some plants (cereals), petiolate leaves form a tube - a sheath, encircling the stem. Such leaves are called vaginal(Fig. 65).

Rice. 65. Types of leaves (A): 1– petiolate; 2 – sedentary; 3 – vaginal; leaf venation (B): 1 – parallel; 2 – arc; 3 – mesh

Leaves can be simple or complex. Simple sheet has one leaf blade and difficult– several leaf blades located on one petiole (Fig. 66).

Rice. 66. Leaves are simple: 1 – linear; 2 – lanceolate; 3 – elliptical; 4 – ovoid; 5 – heart-shaped; 6 – rounded; 7 – swept; complex: 8 – paripirnate; 9 – odd-pinnate; 10 – trifoliate; 11 – finger-compound

The shapes of leaf blades are varied. In simple leaves, the leaf blades can be whole or dissected with various edges: serrated, serrate, crenate, wavy. Compound leaves can be paired or imparipinnate, palmate, or trifoliate.

The sheet plate contains the system veins, performing support and transport functions. Distinguish mesh venation (in most dicotyledonous plants), parallel(cereals, sedges) and arc(lily of the valley) (see Fig. 65).

Internal structure of the leaf (Fig. 67). The outside of the sheet is covered epidermis – peel, which protects the internal parts of the leaf, regulates gas exchange and water evaporation. Skin cells are colorless. On the surface of the leaf there may be outgrowths of skin cells in the form of hairs. Their functions are different. Some protect the plant from being eaten by animals, others from overheating. The leaves of some plants are covered with a waxy coating that does not allow moisture to pass through easily. This helps reduce water loss from the leaf surface.

Rice. 67. Internal structure of the leaf: 1 – skin; 2 – stomata; 3 – columnar fabric; 4 – spongy tissue; 5 – leaf vein

On the underside of the leaf of most plants, the epidermis contains numerous stomata- openings formed by two guard cells. Gas exchange and water evaporation occur through them. The stomatal fissure is open during the day and closes at night.

The inner part of the leaf is formed by the main assimilating tissue, ensuring the process of photosynthesis. It consists of two types of green cells - columnar, located vertically, and round, loosely located spongy They contain a large number of chloroplasts, which give the leaf its green color. The pulp of the leaf is penetrated by veins formed by conducting vessels and sieve tubes, as well as fibers that impart strength. Along the veins, organic substances synthesized in the leaf move to the stem and roots, and the flow of water and minerals flows back.

In our latitudes, there is a massive shedding of leaves every year - leaf fall This phenomenon has an important adaptive significance; it protects the plant from drying out, freezing, and prevents breakage of tree branches. In addition, with dead leaves, the plant is freed from substances that are unnecessary and harmful to it.

Many plants have modified leaves that perform specific functions. The tendrils of the pea, clinging to the support, support the stem, the scaly leaves of the onion store nutrients, the spines of the barberry protect it from being eaten, and the sundew traps lure and catch insects.

Most perennial herbaceous plants have modification of shoots, which have adapted to perform various functions (Fig. 68).

Rice. 68. Modifications of shoots: 1 – rhizome of the kupena; 2 – onion bulb; 3 – potato tuber

Rhizome- This is a modified underground shoot that performs the functions of a root, and also serves for storing nutrients and vegetative propagation of plants. Unlike the root, the rhizome has scales - modified leaves and buds; it grows horizontally in the ground. Adventitious roots grow from it. Rhizomes are found in lily of the valley, sedge, rosemary, and creeping wheatgrass.

Strawberries form above-ground modified stolons - mustache, providing vegetative propagation. When they come into contact with the ground, they take root with the help of adventitious roots and form a rosette of leaves.

Underground stolons – tubers in potatoes these are also modified shoots. Nutrients are stored in the well-developed core of their highly thickened stem. On the tubers you can see eyes - buds arranged in a spiral, from which above-ground shoots develop.

Onion – This is a short shoot with succulent leaves. The lower part - the bottom - is a shortened stem from which adventitious roots grow. The bulb is formed in many lilies (tulips, lilies, daffodils).

Modified shoots are used for vegetative propagation of plants.

§ 53. Generative organs of plants

Generative organs – flower, fruit And seed– provide sexual reproduction of plants.

1. Flower structure(Fig. 69).

Rice. 69. Flower structure: 1 – ovary; 2 – column; 3 – stigma with germinating pollen; 4 – stamens; 5 – sepals; 6 – petals; 7 – peduncle

Flower is a shortened modified generative shoot, the reproductive organ of angiosperms.

The flower is located on peduncle. The expanded part of the peduncle is called receptacle, on which all parts of the flower are located. In the center of the flower are its main parts: the pistil and stamens. Pestle- female organ of a flower, stamens- male organ. The pestle usually consists of stigma, style And ovaries In the ovary are ovules, in which the egg develops and matures. Stamens consist of a filament and anthers. Pollen grains develop in the anthers, in which sperm are formed.

The inner parts of the flower are protected by leaves perianth. Outer green leaves sepals form cup, internal petals form whisk A double perianth is a perianth consisting of a calyx and a corolla, while a simple perianth consists of identical leaves. The cherry, pea, and rose have a double perianth, while the tulip and lily of the valley have a simple perianth. The perianth serves to protect the internal parts of the flower and attract pollinators, so it is often brightly colored. In wind-pollinated plants, the perianth is often reduced or represented by scales and films (cereals, birch, willow, aspen, poplar).

Some plants have special glands in their flowers - nectaries, which secrete a sugary odorous liquid - nectar, which serves to attract pollinators.

Based on the presence of stamens and pistils, two types of flowers are distinguished. Flowers that have a pistil and stamens (apple, cherry) are called bisexual, only stamens or pistils - same-sex(cucumber, poplar).

If staminate and pistillate flowers are located on one individual, then the plants are called monoecious(corn, oak, hazel, cucumber), and if on different ones, then dioecious(poplar, willow, willow, sea buckthorn).

Inflorescences. Plants may have large single or numerous small flowers. Small flowers collected together are called inflorescences. The inflorescences are more visible to pollinators and are more effectively pollinated by the wind. There are several types of inflorescences (Fig. 70).

Rice. 70. Types of inflorescences: 1 – raceme; 2 – ear; 3 – cob; 4 – umbrella; 5 – head; 6 – basket; 7 – shield; 8 – complex umbrella; 9 – panicle; 10 – complex ear

Ear characterized by the presence of sessile (without pedicels) flowers on the main axis (plantain). Complex ear formed by several simple spikelets (wheat, rye).

cob has a thick central axis on which sessile flowers (whitewing) are located. In inflorescence brush(lily of the valley, bird cherry) flowers on pedicels are located on a common axis, one after the other. In inflorescence basket(chamomile, dandelion) many sessile flowers are located on a wide thickened saucer-shaped axis. At the inflorescence head(clover) small sessile flowers are located on a shortened spherical axis. IN a simple umbrella(cherry, primrose) on the main shortened axis, the flowers are on identical long pedicels. In carrots and parsley, the inflorescences consist of a group of simple umbrellas and form complex umbrella.

U shield, Unlike a brush, the flowers are located in the same plane, so the pedicels extending from the central axis have different lengths (yarrow, pear).

Panicle – this is a complex inflorescence that has several lateral branches consisting of racemes and corymbs (oats, lilacs, male corn flowers).

In some inflorescences, part of the flowers consists only of a corolla, and the pistil and stamens are absent: for example, white petals of chamomile, large yellow petals of sunflower. They serve to attract insects and are located along the edges of the inflorescence, while true bisexual flowers are located in the center.

Sexual reproduction of flowering plants. For the formation of a seed, it is necessary for pollen from the stamens to reach the stigma of the pistil, i.e. pollination. If pollen lands on the stigma of the same flower, then selfing(beans, peas, wheat). At cross pollination Pollen from the stamens of one flower lands on the stigma of another.

Fine dry pollen can be carried by the wind (alder, hazel, birch). U wind-pollinated Plant flowers are usually small, collected in inflorescences, the perianth is absent or poorly developed. Insects can carry pollen ( insect-pollinated plants), as well as birds and some mammals. The flowers of such plants are usually bright, fragrant, and contain nectar. In most cases, pollen is sticky and has outgrowths called hooks.

A person can, for his own purposes, transfer pollen from the stamens to the stigma of the pistils, such pollination is called artificial. Artificial pollination is used to obtain higher yields and breed new plant varieties.

The male gametophyte is formed in the stamens - pollen grains (pollen), consisting of two cells - vegetative and generative. In the generative cell, male reproductive cells are formed - sperm.

In the ovary of the pistil, the female gametophyte is formed in the ovule - eight-core embryo sac. This is actually one cell containing 8 haploid nuclei, where one of the largest, located at the pollen entrance, is called egg, and two smaller nuclei located in the center - central cores. When pollen lands on the stigma of the pistil, the vegetative cell grows into the pollen tube, moving the generative cell to the pollen entrance - micropyle. Through the pollen duct, two sperm enter the embryo sac and fertilization occurs. One sperm fuses with the egg to form zygote from which the seed embryo develops. The second sperm fuses with the two central nuclei, forming a triploid endosperm seed in which nutrients can be stored. The seed coat is formed from the covering of the ovule. This fertilization process is called double. It was discovered by the Russian botanist S. G. Navashin in 1898. The overgrown wall of the ovary or other parts of the flower form the fruit.

Rice. 71. The structure of seeds of dicotyledonous (A – beans) and monocotyledonous (B – wheat) plants: 1 – seed coat; 2 – cotyledons; 3 – germinal root; 4 – embryonic stalk with bud; 5 – endosperm

2. Seed. The seed consists of seed coat, embryo And endosperm(Fig. 71). On the outside it is covered with a dense protective seed coat. In the embryo they distinguish root, stalk, bud And cotyledons. Cotyledons are the first embryonic leaves of a plant. Depending on the number of cotyledons in the embryo, monocotyledonous plants (one cotyledon) and dicotyledonous plants (two cotyledons) are distinguished.

Nutrients can be found in cotyledons or special storage tissue - endosperm, in this case the cotyledons are almost not developed.

3. Fruit. The fruit is a complex formation; not only the pistil, but also other parts of the flower can take part in its formation: the bases of the petals, sepals and receptacle. A fruit formed from several pistils is called prefabricated(raspberries, blackberries).

The shape of the fruit is very diverse. Depending on the number of seeds, they are distinguished single-seeded And polyspermous fruits, which is related to the number of ovules in the ovary. There are also juicy And dry fruits (Fig. 72).

Rice. 72. Juicy fruits: 1 – berry (tomato); 2 – drupe (cherry); 3 – apple (pear); 4 – multi-nut (raspberry); 5 – pumpkin (cucumber); dry: 6 – achene (sunflower); 7 – grain (wheat); 8 – bean (pea); 9 – nut (hazel); 10 – pod (radish); 11 – box (poppy)

drupe– juicy single-seeded fruit (cherry, plum, apricot).

Berry – juicy multi-seeded fruit (tomatoes, currants, gooseberries).

Apple - a juicy multi-seeded fruit formed not from the ovary, but from other parts of the flower (pear, plum, apple).

Pumpkin – juicy multi-seeded fruit, the seeds are located in the central part (pumpkin, melon, cucumber).

Pomeranian – juicy multi-seeded fruit of citrus fruits (lemon, orange).

Caryopsis – a dry, single-seeded, indehiscent fruit (corn, rice, wheat), in which the pericarp is fused with the seed coat.

Achene– a dry, single-seeded, indehiscent fruit (sunflower, dandelion), in which the pericarp does not grow together with the peel.

Walnut – dry single-seeded fruit with a lignified pericarp (hazel, walnut).

Bob - dry multi-seeded dehiscent fruit (peas, beans).

Box – a dry multi-seeded fruit (flax, poppy), in which the seeds spill out of numerous holes or cracks.

Pod – dry multi-seeded dehiscent fruit, the seeds are located on the internal partition (cabbage, shepherd's purse, radish).

§ 54. Systematics of plants. Lower plants

The flora is very diverse. Along with multicellular organisms, there are also unicellular organisms. They belong to the most primitive, evolutionarily more ancient forms. plant kingdom divided by two subkingdoms – inferior And higher plants.

Lower plants include various algae, higher plants include spore plants (mosses, mosses, horsetails, ferns) and seed plants (gymnosperms and angiosperms).

Lower plants include a large group of unicellular and multicellular plants, united under the common name “algae”.

Seaweed- the oldest representatives of the plant world, their total number is about 40 thousand species. Among them there are both unicellular, microscopic-sized plants and multicellular giants (Fig. 73). Their habitat is predominantly aquatic, but they are found in soil, on tree bark and even in snow - snow chlamydomonas. Clusters of this algae give melting snow different shades - from red to green.

Rice. 73. Unicellular algae: 1 – Chlamydomonas; 2 – chlorella; 3 – filamentous algae spirogyra; 4 – colonial algae Volvox; multicellular algae: 5 – kelp; 6 – porphyry

A distinctive feature of algae is the lack of differentiation into tissues and organs. The body of the simplest algae consists of one cell. Groups of cells can unite and form colonies - colonial forms. Multicellular algae can have a filamentous form or a lamellar structure.

The body of multicellular algae is called thallus or thallus. They absorb water and mineral salts throughout their entire surface.

All algae cells contain chromatophores- organelles in which the process of photosynthesis occurs. The color of chromatophores, and therefore algae, depends on the content of the coloring pigment and can be green, yellow, brown, red. But all algae have a green pigment - chlorophyll. The classification of algae into various types is based on the structure of the body and the composition of coloring pigments.

Algae multiply more often asexually: unicellular - by dividing the cell into two or four, and multicellular - vegetatively: by parts of the thallus or spores. During sexual reproduction, gametes fuse in pairs and form a zygote. From the zygote, after a period of rest, spores arise through division, giving rise to new organisms. In some algae, the sexual process is more complex.

In a water sample from a fresh reservoir it is easy to find representatives green algae. For example, a mobile unicellular algae - chlamydomonas. Reproducing in large quantities, it gives the water a greenish tint and causes it to bloom. Under a microscope, it is clearly visible that the cell has a rounded shape, covered with a durable membrane with two or four flagella, with the help of which it actively moves. In the cell, the nucleus, cytoplasm, stigma - a light-sensitive red “eye”, a vacuole with cell sap, two pulsating vacuoles and a green cup-shaped chromatophore are clearly visible.

Some green algae do not have flagella and float passively in water, for example chlorella. Its round cells reach sizes up to 15 microns. It reproduces very actively asexually, synthesizing a large amount of organic matter (up to 40 g of dry mass per 1 m2 per day). This feature is used to obtain feed. In addition, chlorella is bred in water treatment plants for biological wastewater treatment, on spaceships and submarines to maintain normal oxygen concentrations in the air.

At the bottom of reservoirs you can find green “pillows” formed by the accumulation of filamentous algae - Spirogyra. This is a multicellular algae, each thread of which consists of elongated cylindrical cells with a spirally twisted chromatophore. Another representative of filamentous multicellular algae is ulotrix. Its structure is similar to spirogyra, but the chromatophore has the shape of a semiring.

Brown algae widespread in the seas and oceans, some of them can reach enormous sizes - up to 50 m. These giants are attached to the bottom with the help of special outgrowths - rhizoids. Algae thickets are a refuge for many marine inhabitants and a spawning place for marine fish, such as Far Eastern herring.

Seaweed – kelp(sea kale) is used by humans for food, as animal feed, and as fertilizer. seaweed sargassum forms large accumulations in the Atlantic Ocean.

Substances necessary in the production of confectionery products are obtained from brown algae.

Red algae usually live at great depths (up to 200 m). This is the most highly organized group of algae. Some of them have the ability to absorb calcium salts from sea water and accumulate in their thalli. That's why they sometimes resemble corals. Scientists believe that many reefs in the South Pacific Ocean are formed by dead parts of red algae.

The population of the coastal regions of China, Korea, and Japan uses red algae for food. In industry they are used to obtain agar Agar is necessary for the production of marshmallows, marmalade, non-staling bread, and special media for growing microorganisms on them.

§ 55. Higher spore plants

The subkingdom of higher plants unites multicellular plant organisms, the body of which is divided into organs - roots, stems, leaves. Their cells are differentiated into tissues, specialized and perform specific functions.

According to the method of reproduction, higher plants are divided into spore And seed. Spore-bearing plants include mosses, mosses, horsetails, and ferns.

Mosses- This is one of the most ancient groups of higher plants. Representatives of this group are most simply structured, their body is divided into stems and leaves. They do not have roots, and the simplest ones - liver mosses - do not even have a division into stem and leaves; the body has the appearance of a thallus. Mosses attach to the substrate and absorb water with minerals dissolved in it using rhizoids– outgrowths of the outer layer of cells. These are mainly perennial plants of small size: from a few millimeters to tens of centimeters (Fig. 74).

Rice. 74. Mosses: 1 – Marchantia; 2 – cuckoo flax; 3 – sphagnum

All mosses are characterized by alternating generations of sexual (gametophyte) and asexual (sporophyte), and the haploid gametophyte predominates over the diploid sporophyte. This feature sharply distinguishes them from other higher plants.

On a leafy plant or thallus, germ cells develop in the genital organs: spermatozoa And eggs. Fertilization occurs only in the presence of water (after rain or during floods), through which sperm move. From the resulting zygote, a sporophyte develops - a sporogon with a capsule on a stalk in which spores are formed. After ripening, the capsule opens and the spores are spread by the wind. When dropped into moist soil, the spore germinates and gives rise to a new plant.

Mosses are fairly common plants. Currently there are about 30 thousand species. They are unpretentious, can withstand severe frosts and prolonged heat, but grow only in moist, shady places.

Body liver mosses rarely branches and is usually represented by a leaf-shaped thallus, from the back of which rhizoids extend. They settle on rocks, stones, tree trunks.

In coniferous forests and swamps you can find moss - cuckoo flax Its stems, planted with narrow leaves, grow very densely, forming continuous green carpets on the soil. Cuckoo flax is attached to the soil by rhizoids. Kukushkin flax is a dioecious plant, i.e. some individuals develop male and others develop female reproductive cells. After fertilization, female plants produce spore capsules.

Very widespread white, or sphagnum, mosses. By accumulating large amounts of water in their bodies, they contribute to waterlogging of the soil. This is due to the fact that the leaves and stem of sphagnum, along with the green cells containing chloroplasts, have dead, colorless cells with pores. It is they who absorb water 20 times more than their mass. Sphagnum has no rhizoids. It is attached to the soil by the lower parts of the stem, which, gradually dying, turn into sphagnum peat. The access of oxygen into the peat layer is limited; in addition, sphagnum releases special substances that prevent the proliferation of bacteria. Therefore, various objects, dead animals, and plants that fall into a peat bog often do not rot, but are well preserved in the peat.

Unlike mosses, other spore mosses have a well-developed root system, stems and leaves. More than 400 million years ago, they dominated among tree organisms on Earth and formed dense forests. Currently, these are a few groups of mainly herbaceous plants. In the life cycle, the predominant generation is the diploid sporophyte, on which spores are formed. The spores are carried by the wind and, under favorable conditions, germinate, forming a small outgrowth – gametophyte This is a green plate ranging in size from 2 mm to 1 cm. Male and female gametes are formed on the prothallus - sperm and eggs. After fertilization, a new adult plant, a sporophyte, develops from the zygote.

Moss mosses- very ancient plants. Scientists believe that they appeared about 350–400 million years ago and formed dense forests of trees up to 30 m high. Currently, there are very few of them left, and they are perennial herbaceous plants. In our latitudes the most famous club moss(Fig. 75). It can be found in coniferous and mixed forests. The stem of the club moss creeping along the ground is attached to the soil by adventitious roots. Small awl-shaped leaves densely cover the stem. Mosses reproduce vegetatively - by sections of shoots and rhizomes.

Rice. 75. Ferns: 1 – horsetail; 2 – clubmoss; 3 – fern

Sporangia develop on erect shoots collected in the form of spikelets. Ripe small spores are carried by the wind and ensure the reproduction and spread of the plant.

Horsetails- small perennial herbaceous plants. They have a well-developed rhizome, from which numerous adventitious roots extend. Articulated stems, unlike the stems of club mosses, grow vertically upward, with lateral shoots extending from the main stem. The stem contains whorls of very small scaly leaves. In the spring, brown spring shoots with spore-bearing spikelets grow on the wintering rhizomes, which die off after the spores ripen. Summer shoots are green, branching, photosynthesize and store nutrients in rhizomes, which overwinter and form new shoots in the spring (see Fig. 74).

The stems and leaves of horsetails are tough and impregnated with silica, so animals do not eat them. Horsetails grow mainly in fields, meadows, swamps, along the banks of reservoirs, and less often in pine forests. Horsetail, a difficult to eradicate weed of field crops, used as a medicinal plant. Due to the presence of silica, the stems of different types of horsetails are used as a polishing material. Horsetail poisonous to animals.

Ferns, like horsetails and club mosses, were a thriving group of plants during the Carboniferous period. Now there are about 10 thousand species, most of which are distributed in tropical rainforests. The sizes of modern ferns range from a few centimeters (grasses) to tens of meters (trees of the humid tropics). Ferns of our latitudes are herbaceous plants with a shortened stem and feathery leaves. Under the ground there is a rhizome - an underground shoot. From its buds, long, complex feathery leaves - fronds - develop above the surface. They have apical growth. Numerous adventitious roots extend from the rhizome. The fronds of tropical ferns reach a length of 10 m.

Ferns are the most common in our area. bracken, male shieldweed etc. In the spring, as soon as the soil thaws, a shortened stem with a rosette of beautiful leaves grows from the rhizome. In summer, brown tubercles appear on the underside of the leaves - sori, representing clusters of sporangia. Spores form in them.

Young leaves of the male fern are used by humans as food and as a medicinal plant. Bracken fronds are used to decorate bouquets. In tropical countries, some types of ferns are grown in rice fields to enrich the soil with nitrogen. Some of them became ornamental, greenhouse and houseplants, e.g. nephrolepis.

The main difference between gymnosperms and previously studied plants is the presence of seeds and the reduction of the gametophyte. The formation of germ cells, fertilization and seed maturation occur on an adult plant - sporophyte. The seed tolerates unfavorable conditions better and promotes the spread of the plant.

Let us consider the features of the reproduction of gymnosperms using pine as an example (Fig. 76). In the spring, at the end of May, pollen is formed in the light green male cones of the pine tree - a male gametophyte containing sex cells - two sperm. The pine begins to “gather dust”, clouds of pollen are carried by the wind. At the tops of the shoots, female reddish cones consisting of scales develop. They bear two ovules openly (nakedly), hence the name - gymnosperms. Two eggs mature in the ovules. Pollen falls directly on the ovules and grows inside. After this, the scales are tightly closed and glued together with resin. After fertilization, a seed is formed. Pine seeds ripen 1.5 years after pollination. They become brown, the scales move apart, mature seeds with wings spill out and are carried by the wind.

Rice. 76. Development cycle of conifers (pines): 1 – male cone; 2 – microsporophyll with microsporangium; 3 – pollen; 4 – female cone; 5 – megasporophyll; 6 – scale with two ovules; 7 – scales with two seeds in a cone of the third year; 8 – seedling

Coniferous class contains about 560 modern plant species. All conifers are trees and shrubs. There are no herbs among them. These are pines, fir, spruce, larch, juniper. They form coniferous and mixed forests, which occupy vast spaces. These plants got their name because of their peculiar leaves - pine needles They are usually needle-shaped, covered with a layer of cuticle, their stomata are immersed in the pulp of the leaf, which reduces water evaporation. Many trees are evergreens. Among our coniferous forests, various types of pine trees are known and widespread - Scots pine, Siberian pine (cedar) etc. These are tall, powerful trees (up to 50–70 m) with a well-developed, deep-rooted root system and a rounded crown, located at the tops of adult plants. The needles are located in different species, 2, 3, 5 pieces in a bunch.

There are nine species of spruce found in Russia: common spruce (European), Siberian, Canadian (blue) etc. Unlike pine, the crown of spruce is pyramidal, and the root system is superficial. The needles are arranged one at a time.

Pine and spruce wood is a good building material; resin, turpentine, rosin, and tar are obtained from it. Seeds and needles serve as food for birds and animals. They contain a large amount of vitamin C. Pine nuts are collected by the local population and used for food.

Of great importance is also Siberian fir, growing in Russia. Its wood is used to make musical instruments.

Unlike evergreen pines and spruces, larches are deciduous trees. Their needles are soft and flat. Most common Siberian larch And Daurian Their wood is strong, durable, and resists rotting well. It is used in shipbuilding, for the manufacture of parquet, furniture, and for the production of turpentine and rosin. It is also grown in parks as an ornamental plant.

Conifers also include cypress, thuja, and juniper. Common juniper – evergreen shrub, found almost everywhere. Its cones are berry-shaped, juicy, small, they are used in medicine and as food.

One of the tallest (up to 135 m) trees on the planet is the sequoia, or mammoth tree. In height it is second only to eucalyptus.

More ancient gymnosperms are representatives of another class - cycads. They reached their heyday in the Carboniferous period. They are found in all parts of the world except Europe and resemble a palm tree in appearance. Another representative of relict gymnosperms is ginkgo. These trees survive only in Japan, Korea and China.

Angiosperms. Angiosperms, or flowering plants, appeared relatively recently, about 150 million years ago, but quickly spread and conquered our entire planet. Now this is the largest group of plants, numbering about 250 thousand species.

These are the most highly organized of higher plants. They have complex organs, highly specialized tissues, and a more advanced conduction system. They are characterized by intensive metabolism, rapid growth and high adaptability to various environmental conditions.

The main feature of these plants is that their ovule is protected from adverse influences and is located in the ovary of the pistil. Hence their name - angiosperms. Angiosperms have a flower - a generative organ and a seed protected by a fruit. The flower serves to attract pollinators (insects, birds), protects the reproductive organs - stamens and pistil.

Flowering plants are represented by all three life forms: trees, shrubs, and herbs. Among them there are both annual and perennial plants. Some of them switched to life in water for the second time, losing or simplifying some organs and tissues. For example, duckweed, elodea, arrowhead, water lily. Flowering plants are the only group of plants that form complex multi-layered communities on land.

Angiosperms are divided into two classes based on the number of cotyledons in the seed embryo: dicotyledonous And monocots(Table 5).

Dicotyledonous plants- a more numerous class, it includes more than 175 thousand species, united in 350 families. Distinctive features of the class: the root system is usually taprooted, but in herbaceous forms it can also be fibrous; the presence of cambium and differentiation of bark, wood and pith in the stem; leaves are simple and compound with reticulate and arcuate venation, petiolate and sessile; flowers are four- and five-membered; The seed embryo has two cotyledons. Most well-known plants are dicotyledons. These are all trees: oak, ash, maple, birch, willow, aspen, etc.; shrubs: hawthorn, currant, barberry, elderberry, lilac, hazel, buckthorn, etc., as well as numerous herbaceous plants: cornflower, buttercup, violet, quinoa, radish, beets, carrots, peas, etc.

Monocots make up approximately 1/4 of all angiosperms and unite about 60 thousand species.

Distinctive features of the class: fibrous root system; the stem is mostly herbaceous, the cambium is absent; leaves are simple, often with arcuate and parallel veins, sessile and vaginal; flowers three-membered, rarely four- or two-membered; The seed embryo has one cotyledon. The predominant life form of monocots is herbs, perennial and annual, tree-like forms are rare.

These are numerous cereals, agaves, aloe, orchids, lilies, reeds, sedges. Monocot trees include palm trees (date, coconut, Seychelles).

Table 5

The most important families of angiosperms

Continuation of the table. 5

End of table. 5

§ 57. Animal Kingdom. Protozoa

More than 2 million animals live on Earth, and this list is constantly growing.

The science that studies the structure, behavior, and vital functions of animals is called zoology.

The sizes of animals range from a few microns to 30 m. Some of them are visible only through a microscope, such as amoeba and ciliates, while others are giants. These are whales, elephants, giraffes. The habitat of animals is very diverse: water, land, soil and even living organisms.

Having common features with other representatives of eukaryotes, animals also have significant differences. Animal cells lack membranes and plastids. They feed on ready-made organic substances. A significant part of animals actively move and have special organs of movement.

animal kingdom divided into two sub-kingdoms: unicellular (protozoa) And multicellular.

Rice. 77. Protozoa: 1 – amoeba; 2 – green euglena; 3 – foraminifera (shells); 4 – ciliate-slipper ( 1 – large core; 2 – small core; 3 – cell mouth; 4 – cell pharynx; 5 – digestive vacuole; 6 – powder; 7 – contractile vacuoles; 8 – eyelashes)

Protozoa are divided into several types, the most widespread and significant of which are Sarcodaceae, Flagellates, Sporozoans and Ciliates.

Sarcodaceae (Rhizopods). A typical representative of Sarcodaceae is the amoeba. Amoeba is a freshwater, free-living animal that does not have a constant body shape. When an amoeba cell moves, it forms pseudopodia, or pseudopods, which also serve to capture food. In the cell, the nucleus and digestive vacuoles are clearly visible, which are formed at the site where the amoeba captures food. In addition, there is also contractile vacuole, through which excess water and liquid metabolic products are removed. Amoeba reproduces by simple division. Respiration occurs across the entire surface of the cell. Amoeba has irritability: a positive reaction to light and food, a negative reaction to salt.

Testate amoebas - foraminifera have an external skeleton - a shell. It consists of an organic layer impregnated with limestone. The shell has numerous openings - holes through which pseudopodia protrude. The size of the shells is usually small, but in some species it can reach 2–3 cm. The shells of dead foraminifera form sediments on the seabed - limestones. Other shell amoebas also live there - radiolarians(rays). Unlike foraminifera, they have an internal skeleton, which is located in the cytoplasm and forms needles - rays, often of an openwork design. In addition to organic matter, the skeleton contains strontium salts - this is the only case in nature. These needles form the mineral celestine.

Flagellates. These microscopic animals have a constant body shape and move with the help of flagella (one or more). Euglena green – a single-celled organism that lives in water. Its cell is spindle-shaped and has one flagellum at its end. At the base of the flagellum there is a contractile vacuole and a light-sensitive eye (stigma). In addition, the cell contains chromatophores containing chlorophyll. Therefore, euglena photosynthesizes in the light and feeds on ready-made organic substances in the dark.

After several asexual generations, cells appear in the erythrocytes from which gametes develop. For further development, they must enter the intestines of the Anopheles mosquito. When a mosquito bites a person with malaria, the gametes are carried through the blood into the digestive tract, where sexual reproduction and the formation of sporozoites occur.

Ciliates- the most complex representatives of protozoa, there are more than 7 thousand species. One of the most famous representatives - ciliate-slipper. This is a fairly large single-celled animal that lives in fresh water bodies. Its body is shaped like the footprint of a shoe and is covered with a dense shell with cilia, the synchronous movement of which ensures the movement of the ciliate. It has a cellular mouth surrounded by cilia. With their help, the ciliate creates a current of water, with which bacteria and other small organisms on which it feeds enter the “mouth”. A digestive vacuole is formed in the body of the ciliate, which can move throughout the cell. Undigested food remains are thrown out through a special place - powder. Ciliates have two nuclei - large and small. The small nucleus takes part in the sexual process, and the large one controls protein synthesis and cell growth. The slipper reproduces both sexually and asexually. Asexual reproduction after several generations is replaced by sexual reproduction. Next (§ 58–65) multicellular organisms of the Animal Kingdom are considered.

§ 58. Animal Kingdom. Multicellular organisms: sponges and coelenterates

Sponges. These are the simplest multicellular organisms (Fig. 78). The primitiveness of their organization is confirmed by the absence of tissues and organs, although the body of protozoa consists of various types of cells. These are sedentary animals, often forming colonies. They live, attached to the substrate, in seas and oceans, less often in fresh water bodies. The body shape of sponges is varied, but most often it resembles a bag or glass, pierced with numerous holes - at times. The body of the sponge is formed by two layers of cells, between which there is a gelatinous mass - mesoglea. A calcareous or silicon skeleton of the sponge is formed in it, so the body is hard to the touch. But sometimes the skeleton is formed entirely from elastic organic matter. After the death of the organism, in this case, an elastic porous mass remains, which is called a toilet sponge. Through the pores and channels of the body, water is constantly filtered, along with which food particles enter the cavity. They are captured by the flagellar cells of the inner layer and digested. The continuous operation of the flagella ensures the flow of water.

Living sponges resemble raw liver and have a sharp, specific smell. Sometimes they contain toxic substances, so other animals rarely use them as food. Sponges often cohabit with other organisms; small crustaceans, worms, and mollusks live in their cavities and voids. In turn, sponges themselves can settle on the shells of crabs, hermit crabs, and mollusk shells.

Rice. 78. Sponges: 1 – siphon; 2 - freshwater trampoline. Coelenterates: 3 – hydra (1 - mouth; 2 – digestive cavity; 3 – ectoderm cells; 4 – endoderm cells; 5 – sole; 6 – tentacles; 7 – ovary; 8 – testes); 4 – jellyfish cornet; 5 – coral polyp (colony)

Sponges have both asexual and sexual reproduction. During asexual reproduction, they form internal buds. Sponges are in most cases bisexual. The fertilized egg develops into a larva, from which a new organism develops.

Bodyaga - This is a freshwater sponge that lives in overgrown bodies of water rich in organic debris. In thistles, the horny skeleton is connected to tiny calcareous needles. Dry ground bodyagi are used for grinding metals as an abrasive material. Sometimes they are used in medicine and as a cosmetic product.

In nature, sponges act as filters, but they cannot live in polluted water.

Coelenterates. Like sponges, coelenterates belong to lower multicellular(see Fig. 78). There are about 20 thousand species of coelenterates. Most of them are characterized by an attached form - polyp. These are hydras, coral polyps, sea anemones (anemones). But there are also free-floating ones - jellyfish. Some species at different stages of development can have both a polypoid and a medusa form, with the polyp representing the asexual generation, and the jellyfish the sexual generation.

All coelenterates have a single structure plan. These are two-layer animals with a cavity inside. Cell differentiation is higher than that of sponges. In coelenterates, nerve cells appear that form nervous system of diffuse type. Coelenterates have radial symmetry of the body. In sessile forms of polyps, the body has a cylindrical shape, at the anterior end there is a mouth opening surrounded by tentacles. The number of tentacles varies. In swimming jellyfish, the body is shaped like an umbrella, and the mouth opening and tentacles are on the underside, under the umbrella. All species have tentacles with stinging cells, serving for defense and attack. When a sensitive hair is irritated, the cell shoots out a thread with a harpoon at the end and strikes the victim with a poisonous liquid. Paralyzed small animals become food for a polyp or jellyfish, which, with the help of tentacles, sends them into the mouth. Swallowed prey is digested in the intestinal cavity and endoderm cells. Undigested residues are expelled through the mouth. Polyps reproduce by budding, sometimes forming entire colonies. But sexual intercourse is also possible. Sex cells mature on one individual, but cross-fertilization occurs. A larva is formed from a fertilized egg - planula, which floats freely, is covered with a dense shell and can tolerate unfavorable conditions. Attaching to the substrate, it forms a new polyp. In species with a change of generations, medusoid forms are formed on the polyp, which are separated from the polyp and swim freely. Gametes mature only in jellyfish, and the polyp stage is formed from the larva. This is how the alternation of generations occurs.

1. Hydroid. The most famous coelenterate of our fresh water bodies from this class is hydra. This is small, no more than 1 cm in size, the animal has the shape of a stalk and leads an attached lifestyle. At the front end near the mouth opening there are 6-12 tentacles, with the help of which the hydra captures food. It reproduces by budding and sexually. In summer, budding predominates and is very active. The matured young individuals are separated from the mother’s body. In autumn, hydra begins sexual reproduction. Adult hydras die in winter, and the larva formed as a result of the sexual process overwinters at the bottom of the reservoir and gives rise to a new polyp in the spring. Hydra has a developed regeneration– the ability to restore lost body parts. If a polyp is cut into several parts, a new organism can arise from each part.

In marine polyps, the bud is not separated from the mother's body, but remains on it, forming a colony in the form of a bush. Sometimes special buds are formed on the colony, in which jellyfish develop - sexual individuals. They bud from the polyp, and the current carries them over a long distance. This contributes to better distribution of the species. Since jellyfish swim and lead an active lifestyle, their nervous system is more complex, and at the base of the tentacles there are primitive eyes and balance organs. Therefore, jellyfish distinguish between light and dark, up and down in water. Jellyfish produce sex cells. Fertilization occurs in water, and the resulting planula gives rise to the polypoid stage.

2. Scyphoid. These coelenterates are characterized by weak polyp development, but the formation of complex and large jellyfish. The size of scyphoid species can reach 1–2 m in diameter, and numerous tentacles hang down to 10–12 m. For example, in the jellyfish of our seas, the eared aurelia jellyfish has an umbrella diameter of 40 cm, and in the northern cyanide – up to 2 m. Many jellyfish are dangerous for a person. With their stinging cells, they can cause burns, poisoning, and in some especially severe cases, even death.

3. Coral polyps the most numerous and varied. The name of the class is literally translated from Greek as animal-flowers. They live in the seas, forming entire colonies, and really look like bright flowers. The digestive cavity of colonial polyps is single, but divided into chambers, which increases the surface on which digestion occurs. They reproduce both sexually and asexually, but they do not have alternation of generations.

The soft, delicate body of the polyp is protected by a calcareous skeleton, which grows from the base upward. Although the polyps themselves are small (about 1 cm in length and up to 2 mm in diameter), colonies of billions of living creatures create powerful calcareous structures in tropical seas - reefs.

There are coastal reefs, barrier reefs and coral islands - atolls. Coastal reefs- the result of coral activity in the immediate vicinity of the shore. Barrier reefs located far from the coast and stretch over long distances. The Great Barrier Reef near Australia is one and a half thousand kilometers long.

Atolls- These are ring-shaped coral islands, the diameter of which reaches 10 km. In the center of the atoll there is usually a lake with sea water, and the shores are formed by coral limestone. Such a coral reef usually appeared around a volcanic island if an extinct volcano gradually sank into the water. Corals, demanding light, food and oxygen, grew at the top, and at a depth of about 30 m, parts of the colony died, leaving their calcareous skeleton.

The coral structures are compressed over time into solid, dense coral limestone. Coral reefs abound with numerous fish, shellfish, crustaceans and other animals.

Among the representatives of this class there are also single forms that do not form a skeleton. These are anemones, or sea anemones. They are inactive or immobile. Some of them settle on the shells of hermit crabs. The cancer drags the sea anemone along the bottom of the sea and provides food, and the sea anemone protects it from enemies by paralyzing small fish and other animals with stinging cells.

§ 59. Flat, round and annelid worms

All flatworms are three-layer animals (Fig. 79). They have a skin-muscular sac that forms the cover and muscles of the body. The excretory and digestive systems appear. The nervous system consists of two nerve ganglia and nerve trunks. Free-living worms have eyes and tactile lobes. All flatworms are hermaphrodites and lay eggs in a cocoon. Flatworms are divided into ciliated, tapeworms and flukes.

Rice. 79. Flatworms: 1 – liver fluke; 2 – pork tapeworm; 3 – echinococcus; round: 4 – roundworm, 5 – pinworm; ringed: 6 – leech, 7 - earthworm

Representative eyelash worms is free-living white planaria. This animal is 2 cm long, milky white in color, lives in ponds, slow-flowing rivers, and quiet creeks. Its body is covered with cilia, the main movement of which ensures the movement of the planaria along the bottom of the reservoir. Planaria is a predator, feeding on protozoa, coelenterates, daphnia and other small animals. The planaria's throat is capable of turning outward and, due to the suction cup, tightly attaching itself to the victim.

All eyelash worms have the ability to regenerate. Under unfavorable conditions, they can disintegrate into pieces, each of which is subsequently restored into a whole organism.

The length of echinococcus is only 1–1.5 cm. Humans can become infected with it from dogs and other animals. Finna echinococcus is capable of multiplying, forming daughter blisters. Sometimes it grows to the size of a walnut, and in some cases it is as big as a child’s head. This bubble can destroy tissue and can only be removed through surgery.

Ringed worms. These are more highly organized animals than those discussed earlier. The body of annelids is segmented. The nervous system of the nodal type and the excretory system are well developed, and a closed circulatory system appears. There are tactile and light-sensitive cells.

Best known earthworm. This worm lives in the soil, its body is segmented, on the underside there are bristles that are directly involved in movement. If you put an earthworm on paper, you can hear the rustling sound produced by the bristles as the worm moves. It refers to class of oligochaetes.

Worms do not have special respiratory organs. They breathe through their skin. Often after rain, earthworms crawl to the surface of the earth: rainwater floods the worm holes, displacing oxygen from the soil, which makes breathing difficult.

Earthworms are bisexual animals, but they undergo cross-fertilization. When mating, two individuals come closer, overlap their anterior ends and exchange male reproductive products. Eggs are injected into a special belt - a coupling formed from mucus, on the 13th segment, which, moving with the coupling, are fertilized with sperm on the 9th segment. The clutch containing the fertilized eggs slides off the front and forms an egg cocoon. Eggs in a cocoon develop in the soil.

Earthworms are capable of regeneration. When a worm is cut in half, the missing part can be restored.

Earthworms feed on fallen leaves and grass, passing a large amount of soil through themselves, thereby loosening it, aerating it and enriching it with humus. They play a very important role in soil formation.

Lives in sewage polluted water bodies tubifex, serving as food for fish and purifying water from organic contaminants.

In our fresh water bodies there are false horse leech black and gray-green medicinal leech. U medical leech in the depths of the oral cavity there are three ridges with pointed chitinous teeth. They are located at the vertices of the triangle, with teeth facing each other. By sucking, the leech cuts through the skin with them, secreting hirudin, preventing blood clotting. Hirudin stops the development of blood clots, is useful for hypertension, sclerosis, strokes, and resolves subcutaneous hemorrhages.

Previously, medicinal leeches were widely used, but nowadays they have become very rare.

The large false horse leech attacks earthworms, mollusks, and tadpoles. It does not cause any harm to humans, although it sometimes attaches itself to the body of a person bathing in a pond using its rear suction cup.

§ 60. Arthropods

This is the most numerous type of animal. It unites more than 1.5 million species, with the largest number being insects. Arthropods are the top of the evolutionary branch of invertebrates. They began their development in the seas of the Cambrian period and became the first land animals capable of breathing atmospheric oxygen. The ancestors of arthropods, in all likelihood, were ancient annelids. The larval stages of these animals resemble worms, and the segmented body is retained in the adult forms.

General characteristics of arthropods.

1. The body is covered with chitin - a horny substance, sometimes impregnated with lime. Chitin forms the exoskeleton and performs protective functions.

2. The limbs have a segmented structure, connected to the body through joints, with one pair of legs located on each segment.

3. The body is segmented and divided into two or three sections.

4. The muscles are well developed and attached in the form of muscle bundles to the chitinous cover.

5. The circulatory system is not closed, there is a heart. Blood - hemolymph flows into the body cavity and washes the internal organs.

6. There are respiratory organs - gills, trachea, lungs.

7. The nodal type nervous system is more advanced. There are complex compound eyes, antennae - organs of smell and touch, organs of hearing and balance.

8. The excretory system is more advanced than that of annelids.

9. Arthropods are mostly dioecious animals.

Arthropods are divided into crustaceans, arachnids, and insects. They are widespread on our planet and have mastered all living environments: water, land-air, soil.

1. Crustaceans. The class has about 20 thousand species. It includes crayfish, crabs, lobsters, daphnia, cyclops, woodlice, shrimp and many others (Fig. 80). They are mainly inhabitants of water, and their respiratory organs are gills.

Rice. 80. Crustaceans: 1 – crayfish; 2 – daphnia; 3 – Kamchatka crab

The body of crustaceans is divided into three sections: head, chest and abdomen. The head and chest often fuse to form cephalothorax, covered with a common shell. They are characterized by the presence of two pairs of antennae. First pair - antennules– is located on the head, and the second pair – antennas- on the first segment of the body. The limbs that follow are well adapted for holding and grinding food and form the oral apparatus.

Crustaceans, with rare exceptions, are dioecious animals. After internal fertilization, the female lays eggs. Development occurs with metamorphosis- complex transformation. The larva molts several times as it grows, each time becoming more and more similar to the adult form.

The most primitive crustaceans are Daphnia and Cyclops. These are quite small animals. They can be viewed with low magnification under a microscope. U daphnia there are two-branched antennae, which are not only sensory organs, but also organs of movement. Many fish feed on daphnia. Their number is very large in all freshwater bodies. Daphnia feed on bacteria, algae and other small organisms.

The higher crustaceans include the well-known crayfish. It is found mainly in rivers. In cancer, the body is divided into the cephalothorax and abdomen. There are two pairs of antennae and three pairs of jaws on the head. On the chest there are three pairs of jaws and five walking legs, and the first pair of walking legs has powerful claws. The gills of the crayfish are located under the lateral edges of the cephalothorax.

U crabs five pairs of legs extending from the powerful shell of the cephalothorax are clearly visible. Turning the crab over with its bottom side up, you can see a shortened flat abdomen tucked under the cephalothorax. Many crabs are of commercial importance.

Unlike crabs, lobsters and spiny lobsters have a long, well-developed abdomen. These crustaceans live in the seas and oceans and are also of commercial importance.

U hermit crab the fleshy abdomen is covered only with a thin soft film. Therefore, he hides it in the empty shells of sea mollusks, causing the body to take the shape of a twisted shell cavity. When a crayfish grows after molting, it changes its shell to a more spacious one.

Almost all crustaceans are edible and have almost the same taste. But the most valuable are considered to be large representatives of decapods: lobsters, lobsters, crabs, shrimp, crayfish.

2. Arachnids. About 60 thousand species of arachnids are known (Fig. 81). Possessing all the characteristics of arthropods, these animals are characterized by the presence four pairs of legs, extending from the cephalothorax, and two pairs of jaws. The second pair of jaws bears segmented tentacles. Due to the terrestrial lifestyle, the gills were replaced by lungs, and in some, by trachea.

The spider's body is divided into a cephalothorax and an unsegmented spherical abdomen. The upper jaws have sharp, curved ends where ducts open poisonous glands. At the end of the abdomen there are arachnoid warts, to which ducts open arachnoid glands. They produce a thick liquid, which, when leaving the body, solidifies into a thin, transparent thread - a web.

Rice. 81. Arachnids: 1 – cross spider; 2 – tarantula; 3 – karakurt; 4 – taiga tick; 5 – itching; 6 – Scorpio

The web is a trapping network and is used to capture prey. The spider approaches the entangled victim through its web and pierces it with its upper jaws, injecting poison and digestive juices. The venom kills the victim, and digestive enzymes begin to digest the victim. After some time, the spider sucks in the digested food. This type of digestion is called external.

Most famous cross spider with a cross-shaped light spot on the back, house spider, silver spider, living in water. The silverback spider builds a “bell” from its web, which is filled with the air the animal needs to breathe underwater. Many spiders weave a cocoon from their web where they lay their eggs.

Spiders are very useful animals that destroy many harmful insects. The venom of most spiders is not dangerous to humans.

In the southern regions, in Ukraine and the Caucasus, there is a large spider tarantula. He lives in a hole that he digs in the ground, and the entrance to it is covered with cobwebs. Its bite is very painful. A small black spider lives in the deserts and steppes of the south karakurt(translated from Turkic means “black death”). The bite of this spider is extremely dangerous. Karakurt poison causes pain, convulsions, vomiting, and sometimes death. The bite of karakurt is fatal for camels and horses, but sheep calmly eat it along with grass.

Causes considerable harm flour (barn), cheese, grains And bulb mites. Scabies mite(up to 0.3 mm) gnaws numerous passages under human skin, causing acute itching (scabies). The disease is contagious and is transmitted by shaking hands.

Taiga tick suffers a severe viral disease – encephalitis. When bitten, the virus enters the bloodstream, reaches the brain, causing inflammation, and in severe cases, death can occur.

Ticks are also carriers of dangerous diseases such as typhus and relapsing fever, tularemia, etc.

Scorpios- These are the oldest arachnids, at first glance they look more like crustaceans. They are descendants of an ancient group of crustacean scorpions that became extinct about 190 million years ago. They have a segmented abdomen, the body is covered with a thick chitinous covering, and on the cephalothorax there are claws very similar to the claws of a crayfish. But upon closer examination, you will notice that four pairs of legs extend from the cephalothorax, and the claws are a modified second pair of jaws. On the rear abdomen there is a pair of poisonous glands with a sting. The scorpion, grabbing its prey with its claws, bends its abdomen over its head and stings the victim. Scorpions are poisonous; tropical species are especially dangerous to humans. The stings of scorpions, which live in the Volga region and the Caucasus, are painful, but not fatal.

3. Insects. This is the largest group not only among invertebrates, but also among vertebrates. Their number is believed to range from about 1.5 to 2 million, and dozens of new species are described every year.

Insects have mastered all living environments: air, water, land, soil. Their evolution followed the path of adaptation to terrestrial existence. A small part switched to life in water for the second time, mainly in the coastal part.

Body structure. Despite the diversity of appearance, the structure of insects is uniform, which made it possible to combine them into one class. Second class name six-legged, reflects their characteristic feature - the presence of three pairs of jointed limbs.

Insects are characterized by features common to the type of arthropods: a jointed body is covered with a chitinous covering, and there are jointed limbs. The body is divided into three sections: head, chest and abdomen, three pairs of legs extend from three segments of the chest. Most adults have wings. The head is not segmented, the chest consists of three segments, and the abdomen consists of 7–8. On the head there is one pair of antennae (antennae) and three pairs of jaws, forming different types of oral apparatus. The oral apparatus has four main structural plans: gnawing (chewing), licking, sucking and piercing. It consists of one pair of lower and upper jaws, lower and upper lips.

Gnawing mouthparts- This is the most primitive organ. Ancient insects had such organs. Currently, it is characteristic of the larvae of almost all orders, as well as cockroaches, some beetles, and grasshoppers.

licking or lapping, Bumblebees, bees, and wasps have organs that feed on liquid food—flower nectar.

Sucking organs characteristic of butterflies.

piercing-sucking Mosquitoes, bedbugs, and aphids have mouthparts.

Due to different lifestyles, the limbs of insects are modified in running(cockroach), burrowing(medvedka), swimming(swimming beetle), jumping(grasshopper).

The nervous system of insects is well developed. The sense organs have reached a high level of organization: touch, smell, taste, sight, hearing. Complex compound eyes are especially well developed (up to 28 thousand facets in each). Insects see green-yellow, blue and ultraviolet rays. Many of them hear well, including ultrasound.

The respiratory system of insects is represented by tracheas. The tracheal trunks, branching repeatedly in the body of the insect, open with spiracle openings on the sides of the metathoracic and abdominal segments.

The organ of excretion, in addition to special tubes-outgrowths of the intestine, is also the fatty body, where metabolic products are deposited.

Development of insects. All insects are dioecious animals. After internal fertilization, the female lays several dozen eggs. The places where eggs are laid are very diverse: plant leaves, soil, water surface, sewage, meat, etc. The female always lays eggs near the food that the larva will feed on. After some time, the egg hatches into a larva that actively feeds and grows. Depending on the type of larva and its development into an adult insect, it may undergo complete or incomplete transformation.

Rice. 82. Insects: with incomplete transformation (A): 1 – grasshopper development;

2 – locust; 3 – mole cricket; 4 – soldier bug; with complete transformation (B): 5 – butterfly development; 6 – swimming beetle; 7 – gadfly; 8 – bee; 9 – dragonfly

At complete transformation– metamorphosis development occurs in four stages: egg, larva, pupa, adult insect (imago).

The larva is completely different from the adult form (Fig. 82, B), but is more reminiscent of an annelid worm. Its type of nutrition and habitat may completely differ from that of an adult insect. The larvae have a gnawing mouthpart, actively feed and grow, molting several times. When the larva reaches its maximum size, it freezes, becomes covered with a new chitinous shell or arachnoid cocoon and turns into chrysalis. At this stage, insects do not feed (sometimes for the whole winter). After some time, an adult form, an imago, appears from the pupa, with all the signs characteristic of an adult insect (wings, limbs, mouthparts).

Development with complete transformation is characteristic of evolutionarily younger orders. Evolutionarily more ancient insects are characterized by incomplete transformation.

At incomplete transformation development occurs in three stages: egg, larva, imago.

There is no pupal stage. The larva resembles an adult insect in body shape, differing only in size and the absence of wings (Fig. 82, A). As the larva grows, it molts several times before it reaches adult size. In insects with incomplete metamorphosis, eggs usually overwinter.

The class of insects is very diverse. It has more than 30 orders, differing from each other mainly in the structure of the wings, mouthparts and development.

The most widespread lower insects with incomplete metamorphosis are cockroaches, dragonflies, orthoptera(grasshoppers, locusts, crickets),Hemiptera(bugs).

Higher insects with complete metamorphosis include Coleoptera(butterflies),Hymenoptera(bumblebees, wasps, bees, ants, riders),Diptera(flies, horseflies, mosquitoes).

Having colonized various biocenoses, insects settled in them vertically and horizontally. They live on all continents and in all natural areas from the Arctic to Antarctica. Insects of tropical countries are more diverse and larger in size than insects of temperate and northern latitudes. Adapting to different conditions, they acquired different appearances. This applies to body size, coloring, structure of limbs and oral apparatus.

Most insects are small in size (up to 1–3 cm). This allows them to live in places inaccessible to other animals. Thanks to various adaptations, they successfully survive in the struggle for existence. Their color may be patronizing, masking the color of the environment (grasshoppers), warning, in the presence of poisonous glands or an unpleasant smell and taste (wasps, ladybugs), repellent(“eye-shaped” spots on the wings of butterflies). Characteristic for unprotected individuals mimicry– imitation of protected individuals (wasp flies). Insects may have chemical “weapons” of defense, like bombardier beetles, which can fire the end of their abdomen to form a cloud of smoke. Ants secrete large amounts of formic acid, which has a burning effect.

Insects are characterized by seasonal and daily activity and migration in space. For example, butterflies can be diurnal or nocturnal. Locusts are capable of moving over vast distances. In addition, there are social insects: bees, ants, termites, forming large families - colonies in which responsibilities are clearly distributed and individuals are differentiated: queen (large female), drones (males), workers, or soldiers.

The behavior of insects consists of direct reactions to environmental factors, and is also determined by instincts - hereditary unconditional reflex activity. Instincts are highly complex and ensure the appropriateness of the insect’s behavior. For example, a bee, performing a certain “dance” (flight), shows the way to flowers with nectar. In the evening, the ants close the passages to the anthill and expel the alien individuals. Some ants grow fungal mycelium in anthills, cultivate aphids, and “milk” them, forcing them to secrete special sugary substances.

Many centuries ago, man tamed the silkworm, from whose cocoon he obtains silk fiber. This animal can no longer live in nature. Bees also serve people. Soil insects loosen the soil, promote its aeration and accumulation of organic matter. In general, insects are an important link in complex food chains and are an integral part of various biocenoses.

§ 61. Molluscs and echinoderms

Shellfish. This is a fairly large type of animal, numbering about 100 thousand species. They live both in water and on land (Fig. 83). Their body is not segmented and is divided into three sections: head, torso and leg. The head of sessile forms can be reduced. The leg is a muscular formation with the help of which the mollusk moves.

Rice. 83. Molluscs: 1 – forest snail; 2 – scallop; 3 – oyster; 4 – octopus

The body of the mollusk is surrounded on the outside by a fold of skin - mantle. On the ventral side it does not fit tightly to the body, forming mantle cavity. The mantle contains many glands that secrete mucus and form the shell of mollusks. Sink, protecting the body of the mollusk, consists of three layers. The outer layer is made of elastic organic matter similar to horn. The middle layer is calcareous and consists of calcium carbonate. The inner layer is also calcareous, it can be mother-of-pearl or porcelain. The mollusk grows, and the shell grows with it. Some massive sea shells have a very thick and powerful calcareous layer. The organic layer protects the limestone from the effects of acids.

Shellfish breathe gills, which are located in the mantle cavity. In terrestrial forms, the gills were reduced; such mollusks breathe through the walls of the mantle cavity, which turned into lungs. It's interesting that the pond snail and the reel respiration is secondary pulmonary. They returned to the water a second time, maintaining their breathing with atmospheric oxygen. The excretory ducts of the kidneys, genitals and anus open into the mantle cavity. The nervous system of mollusks is much simpler than that of arthropods, and resembles that of flatworms. The circulatory system is not closed. Mollusks are dioecious and bisexual. Fertilization is internal.

There are several classes in a type.

Gastropods They have a spirally twisted shell, into which in case of danger they retract their body. The mouth of the shell is closed with mucus. Some gastropods have lost their shells.

The representatives are grape snail, rapana, large and small pond snails, coils, slugs(shellless). Herbivorous terrestrial mollusks - snails and slugs - are agricultural pests.

Bivalves inhabit salt and fresh water bodies. Their shell has two valves, which are closed by special closing muscles. Often the valves have protrusions - teeth, which contribute to a tighter closure. From the inhabitant of our fresh water body toothless There is no such lock on the sash. In bivalves, the head is reduced. A giant representative of this class is Tridacna. It lives in the Pacific and Indian oceans. The size of its shells reaches 1.35 m, weight – 250 kg. This class includes mussels, scallops, and oysters.

Cephalopods – squid, cuttlefish, octopus, the most highly organized of mollusks. All cephalopods are predators. To capture prey, they have well-developed tentacles with suction cups - this is a modified leg. The shell is greatly reduced, partially preserved as a plate under the mantle. Cephalopods have well-developed eyes. They move due to jet shocks when water is ejected from the mantle cavity.

Echinoderms. The phylum of echinoderms has about 5 thousand species. Its representatives live exclusively in the seas. These are quite highly organized animals, resembling balls, stars and even plant flowers in appearance. Depending on their body shape, they are divided into starfish, snaketails, sea urchins, sea capsules, and sea lilies (Fig. 84).

Rice. 84. Echinoderms: 1 – starfish; 2 – sea urchin; 3 – brittle star; 4 – stalked lily; 5 – sea cucumber (cucumaria)

A characteristic feature of echinoderms is the presence of a subcutaneous calcareous skeleton, consisting of plates with spines-needles (hence the name of the type). Calcareous plates often form a continuous shell with a large number of outgrowths - needles that protrude outward. In starfish and urchins, some spines sit on movable legs. Sometimes they are equipped with poisonous glands and perform a protective function.

All echinoderms are radially symmetrical animals; as a rule, they have five rays. Radial symmetry was acquired secondarily as a result of the transition to a sedentary or sedentary lifestyle. In the center of the body is the mouth opening. A characteristic feature of echinoderms is the presence of a water-vascular system, which is a ring canal with branched radial rays-channels. It performs the functions of respiration, gas exchange, and excretion.

Echinoderms are dioecious animals. After external fertilization, a larva develops from the egg, which floats freely and undergoes changes. Echinoderms are characterized by regeneration of body parts. A severed ray of a starfish can restore a new star at the damaged end. In some species, under unfavorable conditions, spontaneous disintegration of the body into separate parts occurs, followed by regeneration. Echinoderms are found in abundance in salt water bodies at all latitudes and at the greatest depths. They cannot tolerate fresh water.

Sea stars distributed in the seas from the Arctic Ocean to the coast of Antarctica, but mainly in tropical and equatorial zones.

Their body has from 5 to 17 rays and is shaped like a star. Stars can reach large sizes: up to 70 cm in diameter. These animals often have bright variegated colors. Starfish are predators, and they are rarely eaten by other animals due to their sharp spines and toxicity.

sea lilies- This is the most ancient group of echinoderms. They look like graceful flowers, sometimes sitting on a stem, and sometimes directly on the ground, brightly, magnificently colored in delicate colors from snow-white to red.

The body of the sea lily consists of a calyx with five extending “arms” that can bifurcate and sometimes branch. The mouth opening of crinoids is located on the upper side of the body, unlike starfish, which is located on the lower side. Sea lilies lead a mostly sessile lifestyle, although some stemless ones can swim, but for very short distances - up to 3–5 m.

Sea urchins most often have a spherical, but sometimes round, flattened or heart-shaped body. Their shell is covered with needles, and often the size of the needles is 2–3 times the size of the body. Tropical species reach the size of a child's head. The mouth opening is at the bottom. Unlike starfish, they are omnivores, but more often feed on plant foods. In many countries, sea urchins are eaten and are subject to commercial fishing.

Dartertails, or brittle stars, similar to starfish, but their rays are much longer, constantly bending and resemble the tail of a snake. In addition, they are clearly separated from the central part. At the brittle star Gorgon head the rays branch repeatedly, truly resembling the head of an ancient Greek mythical monster. Their body coloring is bright and varied. Many of them are capable of emitting a bright greenish-yellow light.

Holothurians, or sea egg pods, have a highly reduced skeleton with bilateral symmetry. The body is elongated, worm-shaped. The disturbed sea cucumber shrinks, taking the shape of a cucumber. The mouth opening, surrounded by tentacles, is located laterally, i.e. they lie on their sides. These are bottom crawling animals, sometimes they burrow into muddy soil. Some species can be eaten - these are sea cucumbers and cucumaria.

§ 62. Chordates. Fish

Chordata. The number of chordates is small - 45 thousand species and makes up only 3% of the total number of animal species. This is the most highly organized group, and its representatives can be found in all environments where there is life.

All chordates have three distinctive characteristics.
1. They have an internal axial skeleton - chord, which in higher forms is replaced spine. Central nervous system in the form neural tube located above the axial skeleton and is divided into head And spinal cord.
2. All chordates in the adult, embryonic or larval state have pharyngeal gill slits, located on both sides of the pharynx. Through these slits, water entering the pharynx passes into the gills and is expelled out.
3. All chordates - bilaterally symmetrical animals.

In addition to the listed characteristics, they are characterized by a closed circulatory system and the heart, a muscular organ that ensures the movement of blood through the vessels in the body. The evolution of the circulatory system followed the path of formation of two circles of blood circulation and an increase in the heart chambers from 2 to 4 (Fig. 85). The improvement of the nervous system followed the path of enlargement of the brain, in particular its anterior section, and the development of sensory organs. During the transition from an aquatic to a terrestrial way of life, the skin, respiratory system, and organs of movement changed significantly. All vertebrates are dioecious.

Subphylum Vertebrates received the greatest importance and distribution, includes several main classes: Cartilaginous fish, Bony fish, Amphibians, Reptiles, Birds, Mammals.

Fish are divided into two classes: cartilaginous And bone(Fig. 86). The habitat of fish is water, so they have a streamlined body shape. Their organs of locomotion are their fins. All fish are characterized by a two-chambered heart and one circulation. Breathing is carried out using gills (see Fig. 85).

1. Cartilaginous fish- the most primitive of modern fish. They have a cartilaginous, non-ossifying skeleton. The paired fins are arranged horizontally. The swim bladder is missing. They are characterized by internal fertilization. Females lay fertilized eggs in the cornea or give birth to live young. This class of fish includes sharks, rays, and chimeras.

Typical representatives of cartilaginous fish - sharks have a spindle-shaped body. Paired pectoral and pelvic fins and an asymmetrical caudal fin allow them to swim quickly.

Sharks have well-developed dentition; many are predators. Among them there are large species. This is a giant shark (up to 15 m), a whale shark (up to 20 m), and a blue shark (up to 4 m). In the Black Sea there is a katran shark (up to 1 m). Sharks are distributed throughout the globe. Many of the sharks that live in tropical seas are dangerous to humans. Large sharks, basking and whale, feed on plankton and are not dangerous.

Stingrays – These are bottom fish. Their body is flattened in the dorso-ventral direction. They are inactive and feed on bottom animals. Stingrays that live in the Black Sea have a long, barbed needle on their tail that secretes poison. The stings of tropical stingrays are especially poisonous. Electric stingrays have electrical organs on their sides - modified muscles that create electrical discharges up to 200 V. They use electric shock to infect fish and other animals that they feed on. These stingrays live in warm waters, such as the Mediterranean Sea.

Group chimeras – the fewest. They have some similarities with bony fish. These are mainly deep-sea fish that feed on shellfish.

2. Bony fish- This is the largest group. Their skeleton is made of bone tissue, the gills are covered with gill covers. A swim bladder appears, which reduces the density of the body and helps to float on the water.

Most modern fish are bony fishes. Their skeleton consists of real bones, their body is covered with scales. Among bony fish there are herbivores, predators and omnivores.

Bony fish are characterized by external fertilization. The female lays eggs, and the male waters them with seminal fluid. However, there are species with internal fertilization and viviparous.

Among bony fishes there are representatives of ancient groups - dipnoi And lobe-finned. These fish are able to breathe atmospheric air, and their fins have turned into blades that are used to crawl along the ground. It is from such fins that the limbs of terrestrial vertebrates developed. Lungfish and lobe-finned fish are rare and flourished more than 380 million years ago. Their ancestors gave rise to amphibians. Currently, the most famous coelacanth is a large fish, up to 180 cm in length, with blades instead of fins that allow it to move along the ground.

Deep-sea fish include anglerfish, and bottom-dwelling fish include flounder, which has a flattened body and a deformed, asymmetrical skull.

Many of the bony fish are of great commercial importance. This salmoniformes(salmon, salmon, pink salmon, sockeye salmon),herring-shaped(Atlantic herring, herring, sprat, sardine, anchovies),carp-like- inhabitants of fresh water bodies (carp, carp, ide),codlike and many others.

The transition group has osteochondral fish cartilage is preserved, the vertebral bodies are not developed. These include sturgeon fish: beluga, sturgeon, kaluga, stellate sturgeon, sterlet, etc.

Rice. 85. Evolution of organ systems of vertebrate animals: brain (P – forebrain; S – middle; Pd – oblongata; Pr – intermediate; M – cerebellum); circulatory system (P – atrium; F – ventricle)

Rice. 86. Fish. Cartilaginous: 1 – herring shark; 2 – electric ramp; osteochondral: 3 – sturgeon; 4 – sterlet; bony: 5 – Atlantic herring; 6 – pink salmon; 7 – saury; 8 – catfish; 9 – piranha; 10 – flying fish

§ 63. Amphibians and reptiles

Amphibians (amphibians). This is a small group of the most primitive terrestrial vertebrates (Fig. 87). Depending on the stage of development, most of them spend part of their lives in water. The ancestors of amphibians were lobe-finned fish that lived in fresh, drying reservoirs.

Rice. 87. Amphibians: 1 – newt; 2 – spotted salamander; 3 – proteus; 4 – axolotl (ambistoma larva); 5 – pond frog; 6 – pipa; 7 – caecilian

In the larval stage (tadpoles), amphibians are very similar to fish: they retain gill breathing, have fins, a two-chambered heart and one circulation. Adult forms are characterized by a three-chambered heart, two circles of blood circulation, and two pairs of limbs. The lungs appear, but they are poorly developed, so additional gas exchange occurs through the skin (see Fig. 85). Amphibians live in warm, humid places, especially common in the tropics, where climatic conditions are suitable for them.

These are dioecious animals. They are characterized by external fertilization and development in water. From the eggs of a tailless amphibian, such as a frog, a tailed larva emerges - a tadpole with long fins and branched gills. As development progresses, the forelimbs appear, then the hind limbs, and the tail begins to shorten. Branched gills disappear, and gill slits (internal gills) appear. From the anterior section of the digestive tube, the lungs are formed, and as they develop, the gills disappear. Corresponding changes occur in the circulatory, digestive and excretory systems. The tail dissolves and the young frog comes to land. In tailed amphibians, the gills are retained much longer (sometimes throughout life), the tail does not dissolve.

Amphibians feed on animal food (worms, mollusks, insects), but larvae living in water can be herbivorous.

There are three groups of amphibians: caudate(newt, salamander, ambistoma), anurans(toads, frogs), legless, or caecilians(fish snake, worm).

Tailed amphibians most primitive. They live in and near water; their limbs, as a rule, are poorly developed. Some have feathery gills that last their entire lives.

The Ambystoma axolotl larva even begins to reproduce without reaching the adult stage. The most numerous are salamanders.

Worms- a very small family. They have no limbs, their body is elongated, reminiscent of a worm or snake.

The most prosperous group is tailless amphibians. They have a short body and well-developed limbs. During the breeding season, they “sing” - they make various sounds (croak).

Reptiles (reptiles). Reptiles belong to terrestrial vertebrates. They adapted well to life on land and displaced many of their amphibian ancestors. Reptiles have a three-chambered heart. They begin to separate arterial and venous blood due to the appearance of an incomplete septum in the ventricle of the heart; The nervous system is better developed than that of amphibians: the cerebral hemispheres are much larger (see Fig. 85). The behavior of reptiles is much more complex than that of amphibians. In addition to innate unconditioned ones, they also develop conditioned reflexes. The digestive, excretory and circulatory systems open into cloaca- part of the intestine.

The body of reptiles is covered with scales. It is formed in the thickness of the skin - the epidermis - and protects the body from drying out. Some species shed their scales during the molting process (snakes, lizards). The lungs of reptiles are much larger and more voluminous than those of amphibians due to their cellularity.

Reptiles are dioecious animals. Their fertilization is internal. The female lays eggs covered with a leathery shell in the sand or in the soil in small depressions. Even among aquatic inhabitants, egg development occurs on land. Some species are characterized by viviparity.

Reptiles reached their greatest prosperity in the Mesozoic era, about 100–200 million years ago, which is why this era is called the era of reptiles. There was a huge number and variety of them: dinosaurs on land, ichthyosaurs in water, pterosaurs in the air. Among them were species of enormous size, as well as rather small forms, the size of a cat. Almost all of them went extinct about 70 million years ago. The cause of the extinction is still not fully understood. There are several hypotheses: a sudden sharp change in climate, the fall of a giant meteorite, etc. But all of them do not fully explain this mystery.

Currently there are four main groups: turtles, snakes, lizards and crocodiles (Fig. 88).

Rice. 88. Reptiles: 1 – steppe gecko; 2 – agama; 3 – long-eared roundhead; 4 – frilled lizard; 5 – gray monitor lizard; 6 – spectacled snake; 7 – rattlesnake; 8 – already

Characteristic feature turtles is the presence of a shell consisting of bone plates and covered with horny substance. Representatives of this group can live both on land and in water. Giant and elephant turtles (up to 110 cm long) are the largest of those living on land. They are common on the Galopogos Islands of the Pacific Ocean, Madagascar, and the islands of the Indian Ocean.

Sea turtles are much larger (up to 5 m) and have flipper-like legs. They live in water all their lives, but lay eggs on land.

Lizards very diverse. This is the most prosperous group. These include chameleons, geckos, iguanas, agamas, roundheads, monitor lizards and true lizards. Most lizards are characterized by an elongated body, a long tail, and well-developed limbs. Some (yellowbellies) have lost limbs, they resemble snakes.

U snake The main feature is a long, limbless body. These are crawling animals. All snakes are predators; they swallow prey whole or strangle it, squeezing it in the coils of their bodies. Venom glands (modified salivary glands) open through a duct at the base of the poisonous tooth. Snakes include: viper, viper, cobra, python, boa constrictor, as well as snakes - non-venomous representatives of this group.

Crocodiles Of all reptiles, they are closest to mammals. Their heart can be called four-chambered, there is a bony palate, and air enters through the nostrils into the back of the mouth. In terms of the structure of the oral cavity and the position of the tongue, they are closer to mammals than to other reptiles. These are quite large tailed animals that live in water, along river banks. On land they move slowly, but they swim well. Females lay lime-shelled eggs on land in small holes. They are characterized by caring for their offspring: the female protects the clutch and takes care of the cubs.

Reptiles live mainly in warm climates: tropics, subtropics, wet and dry places: deserts, swamps, forests. Their diet is also varied: plants, insects, worms, mollusks, and large individuals eat birds and mammals. All reptiles swallow food whole. Many species, feeding on agricultural pests (insects, rodents), bring great benefits to humans. Snake venom is used to prepare many medicines. Shoes and handbags are made from the skin of snakes and crocodiles, which previously led to the mass extermination of animals. Currently, many species are protected and grown on farms and nurseries.

§ 64. Birds

Birds are higher vertebrates that have adapted to flight. They are distributed throughout the globe and number up to 9 thousand species. The body of birds is covered with feathers, the forelimbs are turned into wings.

Due to the fact that they spend a significant part of their lives in the air, birds have developed some features. Their hollow bones filled with air, which allows you to lighten the body weight. Flying species have a well-developed sternum - keel, to which powerful muscles are attached. This warm-blooded animals with intense metabolism. Body temperature reaches 42 °C. The respiratory system, in addition to well-developed cellular lungs, is also represented air bags, allowing ventilation of the lungs during inhalation and exhalation (double breathing)(see Fig. 85). When you inhale, air enters the lungs and pulmonary sacs. When you exhale, the wings lower, squeezing the bags, and the air passes through the lungs a second time. This promotes better oxygen absorption and high metabolism. Birds have a four-chambered heart. Arterial and venous blood are completely separated. The digestive, excretory and reproductive systems of birds and reptiles are similar. However, unlike the latter, birds lack teeth, a bladder, and females lack a second ovary and oviduct, which is associated with adaptation to flight.

Birds swallow their food whole and enter through the long esophagus. goiter, where it is previously exposed to digestive juices. The stomach consists of two sections: glandular and muscular. Due to the large number of small stones swallowed with food, food is ground in the muscular section. The nervous system of birds is much better developed than that of reptiles, especially the forebrain and cerebellum. Therefore, the behavior of birds is more complex; they develop many conditioned reflexes.

Fertilization in birds is internal. The female lays eggs in built nests. They are characterized by incubating eggs and caring for offspring.

Birds are divided into brood birds and nesting birds.

U brood Bird chicks hatch more adapted to life: they are sighted, covered with down, able to move and feed on their own. These are chickens, ducks, geese, black grouse. They usually build nests on the ground.

U nesting Bird chicks hatch helpless and blind, their body is not pubescent, they are fed by their parents. These are crows, pigeons, starlings, woodpeckers, eagles, hawks and many others. They nest high in trees, in hollows, in burrows along river banks (swallows), on rocks, and in hard-to-reach places.

According to the method of feeding, birds are divided into herbivores(finches, siskins, crossbills, blackbirds), insectivores(woodpeckers, nuthatches, tits), predatory(falcons, hawks, eagles, owls). In addition, many aquatic birds feed on fish (ducks, penguins, herons, pelicans). Among the birds there are scavengers, that feed on animal carcasses, such as vultures.

All birds are divided into three large groups: ratites, swimmers (penguins) and keel-breasted birds (Fig. 89).

Rice. 89. Ratite birds: 1 – kiwi; 2 – African ostrich; 3 – cassowary; 4 – penguin; Keelebreasts: 5 – finch; 6 – falcon; 7 – black grouse; 8 – woodpecker; 9 – stork; 10 – owl; 11 – bustard

1. Ratites, or running, birds live in Africa, Australia, South America. This is the most primitive group: their sternum is flat, there is no keel, and the wings are poorly developed. These include African and American ostriches, emus and cassowaries that inhabit Australia. These are quite large birds, good runners, reaching a height of 2.5 m. Emus and cassowaries have even more underdeveloped wings than ostriches, but have well-developed strong legs. The smallest ratite birds are kiwis that inhabit the forests of New Zealand (height up to 55 cm). Their wings are greatly reduced, almost disappeared, their legs are widely spaced, so they move slowly. In ratites, the eggs are usually incubated by the male.

2. Penguins- also flightless birds, but they have a keel on their sternum. The largest species, the emperor penguin, reaches a height of 1 m. All penguins are excellent swimmers, their wings have turned into flippers, under water they “fly”, flapping their wings and steering with their legs, like other birds in the air, and on land they move awkwardly, waddling. Their feathers fit tightly together and are well lubricated with the fat of the coccygeal gland, which prevents them from getting wet. Penguins live on the coast of Antarctica and feed on fish, mollusks, and crustaceans. They nest on the ground. The eggs are incubated by the males, pinching them between their paws and lower abdomen. Females feed in the sea at this time. Towards the end of the development period before hatching, they return, nurse and feed the chicks.

3. Keelebreasts- the most common group of birds. They are divided into 34 squads. Most of them are flying. Depending on their habitat and nutrition, they can be divided into the following ecological groups: forest, steppe-desert, swamp-meadow, aquatic, landscape and carnivorous.

Forest birds nest and feed in the forest, both in trees and in the lower tier, on the ground. These are woodpeckers, goldfinches, siskins, finches, finches, and birds of paradise that live in Australia. And also black grouse, wood grouse, partridges, pheasants living in forest clearings and edges.

TO swamp-meadow Birds include cranes, storks, waders, corncrakes, and herons. Birds of this group have long legs and feed on small animals. Birds of open spaces include larks, which soar high in the sky. But they nest and feed on insects on the ground.

Steppe-desert birds are usually good runners. Along with ostriches, these are bustards and runners.

To the group water unite those birds, most of whose life is spent on the water. These are seagulls, ducks, geese, pelicans, swans, etc. They feed mainly on fish.

Predatory Birds live everywhere and are divided into daytime and nighttime predators. Diurnal predators include hawks, falcons, eagles, buzzards, sea eagles, gyrfalcons, kestrels, and vultures. Nocturnal predators include owls and eagle owls.

Birds of great economic importance are chickens, ducks, geese, and turkeys. Many of them serve as objects of fishing and hunting. Birds bring great benefits by destroying insect pests, especially during the period of feeding chicks.

§ 65. Mammals or animals

Mammals are the most highly organized class of vertebrates. They are characterized by a highly developed nervous system (due to an increase in the volume of the cerebral hemispheres and the formation of the cortex); relatively constant body temperature; four-chambered heart; the presence of a diaphragm - a muscular septum separating the abdominal and thoracic cavities; development of cubs in the mother’s body and feeding with milk (see Fig. 85). The body of mammals is often covered with fur. The mammary glands appear as modified sweat glands. The teeth of mammals are unique. They are differentiated, their number, shape and function vary significantly among different groups and serve as a systematic feature.

The body is divided into head, neck and torso. Many have a tail. Animals have the most perfect skeleton, the basis of which is the spinal column. It is divided into 7 cervical, 12 thoracic, 6 lumbar, 3–4 sacral fused and caudal vertebrae, the number of the latter varies. Mammals have well-developed senses: smell, touch, vision, hearing. There is an auricle. The eyes are protected by two eyelids with eyelashes.

With the exception of oviparous mammals, all mammals bear their young in uterus- a special muscular organ. The cubs are born alive and are fed milk. The offspring of mammals are in greater need of further care than other animals.

All of these characteristics allowed mammals to gain a dominant position in the animal world. They are found all over the globe.

The appearance of mammals is very diverse and is determined by their habitat: aquatic animals have a streamlined body shape, flippers or fins; land dwellers have well-developed limbs and a dense body. In the inhabitants of the air, the front pair of limbs are transformed into wings. A highly developed nervous system allows mammals to better adapt to environmental conditions and promotes the development of numerous conditioned reflexes.

The class of mammals is divided into three subclasses: oviparous, marsupials and placentals.

1. Oviparous, or primal beasts. These animals are the most primitive mammals. Unlike other representatives of this class, they lay eggs, but feed their young with milk (Fig. 90). They have preserved the cloaca - a part of the intestine into which three systems open - digestive, excretory and reproductive. Therefore they are also called monotreme. In other animals these systems are separated. Oviparous species are found only in Australia. These include only four species: echidnas (three species) and the platypus.

2. Marsupials more highly organized, but they are also characterized by primitive features (see Fig. 90). They give birth to live, but underdeveloped young, practically embryos. These tiny cubs crawl into a pouch on the mother's belly, where, feeding on her milk, they complete their development.

Rice. 90. Mammals: oviparous: 1 – echidna; 2 – platypus; marsupials: 3 – opossum; 4 – koala; 5 – dwarf marsupial squirrel; 6 – kangaroo; 7 – marsupial wolf

Australia is home to kangaroos, marsupial mice, squirrels, anteaters (nambats), marsupial bears (koalas), and badgers (wombats). The most primitive marsupials live in Central and South America. This is an opossum, a marsupial wolf.

3. Placental animals have a well developed placenta- an organ attached to the wall of the uterus and performs the function of exchanging nutrients and oxygen between the mother’s body and the embryo.

Placental mammals are divided into 16 orders. These include Insectivores, Chiroptera, Rodents, Lagomorphs, Carnivores, Pinnipeds, Cetaceans, Ungulates, Proboscideans, and Primates.

Insectivores mammals, which include moles, shrews, hedgehogs, etc., are considered the most primitive among placentals (Fig. 91). These are quite small animals. The number of teeth they have is from 26 to 44, the teeth are undifferentiated.

Chiroptera- the only flying animals among animals. They are mainly crepuscular and nocturnal animals that feed on insects. These include fruit bats, bats, noctule bats, and vampires. Vampires are bloodsuckers; they feed on the blood of other animals. Bats have echolocation. Although their eyesight is poor, due to their well-developed hearing, they catch the echo of their own squeak reflected from objects.

Rodents– the most numerous order among mammals (about 40% of all animal species). These are rats, mice, squirrels, gophers, marmots, beavers, hamsters and many others (see Fig. 91). A characteristic feature of rodents is their well-developed incisors. They have no roots, grow throughout their lives, wear down, and have no fangs. All rodents are herbivores.

Rice. 91. Mammals: insectivores: 1 – shrew; 2 – mole; 3 – tupaya; rodents: 4 – jerboa, 5 – marmot, 6 – nutria; lagomorphs: 7 – brown hare, 8 – chinchilla

Close to rodents squad lagomorphs(see Fig. 91). They have a similar tooth structure and also eat plant matter. These include hares and rabbits.

To the squad predatory belongs to more than 240 species of animals (Fig. 92). Their incisors are poorly developed, but they have powerful fangs and carnassial teeth, which are used for tearing animal flesh. Predators feed on animal and mixed food. The order is divided into several families: canids (dog, wolf, fox), bears (polar bear, brown bear), felines (cat, tiger, lynx, lion, cheetah, panther), mustelids (marten, mink, sable, ferret) and etc. Some predators are characterized by hibernation (bears).

Pinnipeds They are also predatory animals. They have adapted to life in water and have specific features: the body is streamlined, the limbs are turned into flippers. The teeth are poorly developed, with the exception of the fangs, so they only grab food and swallow it without chewing. They are excellent swimmers and divers. They feed mainly on fish. They breed on land, along seashores or on ice floes. The order includes seals, walruses, fur seals, sea lions, etc. (see Fig. 92).

Rice. 92. Mammals: carnivores: 1 – sable; 2 – jackal; 3 – lynx; 4 – black bear; pinnipeds: 5 – harp seal; 6 – walrus; ungulates: 7 – horse; 8 – hippopotamus; 9 – reindeer; primates: 10 – marmoset; 11 – gorilla; 12 – baboon

To the squad cetaceans also include inhabitants of the waters, but, unlike pinnipeds, they never go onto land and give birth to their young in the water. Their limbs have turned into fins, and their body shape resembles fish. These animals mastered the water for the second time, and in connection with this they acquired many features characteristic of aquatic inhabitants. However, they retained the main features of the class. They breathe atmospheric oxygen through their lungs. Cetaceans include whales and dolphins. The blue whale is the largest of all modern animals (length 30 m, weight up to 150 tons).

Ungulates are divided into two orders: equids and artiodactyls.

1. TO equid include horses, tapirs, rhinoceroses, zebras, donkeys. Their hooves are modified middle toes, with the remaining toes reduced to varying degrees in different species. Ungulates have well-developed molars, as they feed on plant foods, chewing and grinding them.

2. U artiodactyls the third and fourth toes are well developed, transformed into hooves, which bear the entire weight of the body. These are giraffes, deer, cows, goats, sheep. Many of them are ruminants and have a complex stomach.

To the squad proboscidea belong to the largest of land animals - elephants. They live only in Africa and Asia. The trunk is an elongated nose fused with the upper lip. Elephants do not have tusks, but their powerful incisors have turned into tusks. In addition, they have well-developed molars that grind plant foods. Elephants change these teeth 6 times during their life. Elephants are very voracious. One elephant can eat up to 200 kg of hay per day.

Primates combine up to 190 species (see Fig. 92). All representatives are characterized by a five-fingered limb, grasping hands, and nails instead of claws. The eyes are directed forward (primates have developed binocular vision). These are inhabitants of tropical and subtropical forests, leading both arboreal and terrestrial lifestyles. They feed on plant and animal foods. The dental apparatus is more complete and differentiated into incisors, canines, and molars.

There are two groups: prosimians and monkeys.

1. TO prosimians include lemurs, lorises, and tarsiers.

2. Monkeys are divided into broad-nosed(marmosets, howler monkeys, koatas) and narrow-nosed(macaques, monkeys, baboons, hamadryas). To the group higher narrow-nosed Great apes include gibbon, chimpanzee, gorilla, and orangutan. Humans also belong to the primates.

Scheme of subordination of animal groups

Classification Kingdom Animals

Comparison of plants and animals

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