Classification and structure of algae

The world of algae is huge. It occupies a very special place in the plant kingdom, exceptional in its significance, both in the historical aspect and in the role that belongs to it in the general circulation of substances in nature. At the same time, the very concept of "algae" in scientific terms suffers from great uncertainty. This forces us to specifically discern the difference between the plant organisms referred to here and the rest of the representatives of the plant kingdom, indeed, the word "algae" means only that these are plants living in water. But in botany, this term is used in a narrower sense, and not all plants that we observe in water bodies can be called algae. On the other hand, we often simply do not notice algae in water bodies, since very many of them are not easy to recognize with the naked eye. Looking closely at various water bodies, especially lakes, we first of all notice the richness of plants. Some of them are attached to the bottom. These include, for example, large green accumulations of the so-called mud. Larger algae are also often found here, consisting of ordinary or branching filaments that are perfectly visible to the eye, or completely large choral algae that look like horsetail from the outside. On the other hand, a significant amount of microscopic algae, the same as in water bodies, also grows on land: on the surface of the earth and in its very thickness, on trees, stones. True, the life of these algae is also closely connected with water, but they can only enjoy atmospheric and ground moisture, dew. Unlike "aquatic" algae, these algae simply tolerate desiccation and very soon come to life with the slightest moisture. In the plant kingdom, algae belong to a vast sub-kingdom of lower or thallus plants, which also includes bacteria, fungi and lichens. Like all lower plants, algae reproduce vegetatively or with the help of spores, that is, they belong to spore plants. But physiologically, algae differ sharply from other lower plants in the presence of chlorophyll, thanks to which they are able to assimilate carbon dioxide in the light. In addition, many algae that have well-developed chlorophyll, in addition to phototrophic, can also have other types of nutrition. Thus, based on what has been said, it is easy to derive a clear scientific definition of algae. Algae are lower, that is, thallus spore plants, containing chlorophyll in their own cells, and living mostly in water. Such a definition, however, does not give an idea of ​​the great diversity in body structure that is characteristic of algae. Here we meet with microscopic organisms - unicellular and multicellular, and with large forms of various structures. Here the methods of reproduction and the structure of the reproductive organs reach an enormous contrast. Even in color, algae are not the same, since some contain only chlorophyll, the rest still have a number of additional pigments that color them in different colors. The division of algae into systematic groups of the highest rank basically coincides with the nature of their coloration, which is naturally associated with structural features. Algae are divided into 10 departments:

Blue-green algae;

pyrophytic algae;

golden algae;

diatoms;

Yellow-green algae;

brown algae;

Red algae;

Evshenovye algae;

Green algae;

Choral algae.

Blue-green algae differ sharply from other algae in simplicity internal organization cells. Their cells are devoid of a formed nucleus, which brings them closer to bacteria. Together with bacteria, blue-green algae constitute a section of organisms designated as prokaryotes, that is, "pre-nuclear", in contrast to all other plants and animals that have a formed cell nucleus and are designated as eukaryotes.

Cell - the basic structural unit of the body of algae, represented by either unicellular or multicellular forms.

The highlight of unicellular forms is determined by the fact that here organisms consist of only one cell, therefore, cellular and organismal features are mixed in its structure and physiology.

A small unicellular alga not visible to the naked eye plays the role of a specific factory that extracts raw materials, processes them and produces such valuable compounds as proteins, carbohydrates and fats. In addition, oxygen is considered to be the principal product of its activity. Thus, it is actively involved in the cycle of substances in nature. Unicellular algae from time to time form temporary or permanent clusters in the form of colonies.

Multicellular forms appeared after the cell made a long and difficult path of development as an independent organism.

When meeting with algae, an extraordinary abundance of both shapes and sizes of their cells catches the eye. A large variety of pictures is found in free-living unicellular algae.

In algae, unlike higher plants, there are cells whose contents are surrounded only by a narrow membrane. Such cells are traditionally called naked. They are unable to maintain their shape and are constantly in an amoeboid state. Cells of this kind are found both among unicellular and multicellular algae, most often at the stage of gametes and zoospores.

Cells of some algae (euglena, yellow-green), except for the plasmalemma, are surrounded by a leathery, elastic layer. This layer is called pellicle or periplast. It is composed of a fibrillar substance and has a complex, multi-layered company. Cells with such a pellicle are traditionally quite variable in shape. Only a thick, shell-like pellicle can firmly fix it. From time to time, folds appear on the surface of the pellicle, outgrowths in the form of teeth or thickenings, called scales. These structures in different combinations form the most unusual patterns, giving the body a unique look. But their main function is to increase the strength of the cell cover.

Cell walls of algae are very diverse both in their structure and in chemical composition. The thickness of the shell varies not only from species to species, but even within the same species, depending on the age of the cell.

According to the time of initiation and growth characteristics, primary and secondary shells are distinguished. In actively dividing cells, only the primary membrane traditionally appears. Its growth goes in two directions: the surface and thickness increase.

The secondary membrane undergoes hydration, becomes elastic and gains the ability to stretch.

The shells of many algae are supplied with various kinds of outgrowths in the form of bristles, spines and scales. Their role for the cell is ambiguous: in some variants they perform a protective function, while in others they provide rational living conditions.

Green algae are unicellular, colonial and multicellular forms, of diverse structure, green color. The product of assimilation is starch, flour, oil. There are both motile forms with flagella at the anterior end of the cells, and immobile, attached or passively floating. Reproduction is vegetative, asexual and sexual. A number of forms have an alternation of asexual and sexual reproduction. Zoospores and gametes with 2 or 4 flagella located at the anterior end. Freshwater and marine algae.

The largest department of algae (13 thousand species). A large variety of forms is characteristic: unicellular, filamentous, colonial. Closest to higher plants. All types of differentiation of the thallus are represented: monadic, coccoid, palmelloid, filamentous, lamellar, siphonal. Representatives are characterized by a pure green color, since chlorophyll a and b predominate among the pigments. In addition, there are pimenty: carotenes and xanthophylls. The rigid cell wall is composed of cellulose and pectin. Spare substances are starch and oil.

Reproduction is vegetative, asexual and sexual.

They live mainly in freshwater reservoirs, although there are also marine, soil and terrestrial forms.

The division includes the following classes: volvox (Volvocophyceae), protococcal (Protococcophyceae), ulotrix (Ulotrichophyceae), conjugates (Conjugatophyceae) and siphon (Siphonophyceae).

Volvox class (Volvocophyceae)

The most primitive representatives of green algae. They are found as unicellular and colonial forms. A typical representative of unicellular is Chlamydomonas (Chlamidomonas). Chlamydomonas cells have a spherical or ellipsoidal shape and are covered with a sheath of hemicellulose and pectin substances. At the anterior end of the cell are two flagella, at the base of which there are two pulsating vacuoles. The entire inner part of the cell is occupied by a protoplast with a large pyrenoid with a starch sphere. Chlamydomonas breeds asexually using biflagellate zoospores. In addition, sexual reproduction is also possible by meiotic cell division with the formation of biflagellated gametes.

Another typical representative of the Volvox is the colonial genus Volvox. Volvox colonies have the appearance of mucous balls, up to 2 mm in diameter, along the periphery of which there are chlamydomonas-like cells connected by plasmodesmata. Cells in a colony are of two types - vegetative, smaller and numerous, and large generative, scattered between vegetative cells. Parthenogonidia (cells of asexual reproduction) and oogonia (female sex gametes) and antheridia (male sex cells) are formed from generative cells, which carry out the sexual process.

Protococcal class (Protococcophyceae)

These are immobile cells with a dense shell and colonies of such cells. Most representatives of the class have a coccoid structure. The cell membrane is cellulose or with an admixture of pectin (in lower representatives it may consist entirely of pectin). Asexual reproduction is carried out with the help of two-flagellated zoospores, the sexual process - with the help of mobile two-flagellated isogametes (isogamy is the process of fusion of identical single-nuclear gametes into a zygote.

The only exception is the alga Chlorella (Chlorella), which has no mobile stages during asexual reproduction and is not characterized by a sexual process.

Main representatives: chlorella (Chlorella), chlorococcus (Chlorococcum), protococcus (Protococcus).

Ulotrix class (Ulotrichophyceae)

A very diverse group of filamentous and lamellar algae living in salt and fresh water bodies. The structure of the threads can be simple or multifilamentous (heterotrichal). Plate forms are single-layer and two-layer.

Asexual reproduction is carried out by mobile zoospores. The sexual process is isogamous.

The main representatives: ulorix (Ulothrix), ulva (Ulva), monostoroma (Monostroma), etc.

The class combines unicellular and filamentous forms with a special type of sexual process - conjugation.

Conjugation (lat. conjugatio - fusion, connection) - the process of fusion of protoplasts of two vegetative cells that perform the function of gametes.

The fusion occurs through a special conjugation channel. It is sometimes quite difficult to separate cells into male and female and is possible only after some time has passed: a cell with female potency will be a cell that contains a zygote. But often the fusion of protoplasts occurs in the conjugation channel, which grows with the zygote to the walls of the mother cells. This phenomenon is observed when the protoplasts move along the channel at the same speed. In this case, they speak of isogamy. In the most developed representatives of mating cells, the contents of one cell flows into another with the formation of a zygote. This phenomenon is called heterogamy or anisogamy (from Gr. Hetero - another, anisos - unequal + gamos - marriage). After a dormant period, the zygote germinates and gives rise to one or more seedlings. For the normal course of conjugation, favorable conditions are necessary: ​​warm water (from +15 to +24 0С) and intense illumination. Conjugation lasts no more than 14 days, from the formation of conjugation channels to the maturation of the zygote.

Also, a distinctive feature of the class is the complete absence of mobile stages in their life cycle. The chromatophores are always pyrenoid, lamellar, and very variable in shape. Conjugates are cosmopolitan and can be found anywhere globe up to Antarctica. Couplings live in fresh and slightly salted water, but there are no typical marine forms among them. In addition, there are representatives of the class on the ground - in mosses, on rocks, damp earth and even on glaciers.

The main representatives: spirogyra (Spirogyra), zygnema (Zygnema), muzhotia (Mougeotia), etc.

Siphon class (Siphonophyceae)

Representatives of this class do not have a cellular structure. The thallus of these algae is one giant cell with one or many nuclei. Sometimes such a cell is divided into segments by partitions. Such a structure is called a siphon.

Siphon - the most ancient group of green algae. More than 90% of the group's representatives live in the seas, but there are also freshwater forms.

The most typical representatives: kaulerpa (Caulerpa), codium (Codium), dasikladus (Dasycladus), acetobularia (Acetobularia).

Indicate the similarities and differences between yellow-green and green algae:

Yellow-green algaeGreen algae chloroplastsChloroplast has a structure typical of ochrophytes. Usually there are several green or yellow-green discoid plastids in the cell. Their color is associated with the absence of fucoxanthin, which is responsible for the golden and Brown color in other ochrophytes. Of the carotenoids in Tribophytaceae, there is α - and β- carotenes (predominant), vosheriaxanthin, diatoxanthin, diadinoxanthin, heteroxanthin, lutein, violaxanthin, neoxanthin, etc. Chlorophylls - aand c. In the cells of Tribophytaceae, in addition to discoid ones, plastids of other forms are also found: lamellar, trough-shaped, ribbon-shaped, cup-shaped, stellate, etc. Pyrenoids of a semi-pressed type were found in a few species. The ocellus consists of a number of lipid globules, located at the anterior end of the body in the chloroplast, oriented to the basal swelling of the flagellum. The shape and size of chloroplasts green algae vary. In unicellular representatives, they are often cup-shaped with a thickened base. In filamentous representatives, they can be annular, reticulate, disc-shaped, in the form of spirally twisted ribbons, etc. Chloroplasts contain one or more pyrenoids. Pyrenoids are embedded in the chloroplast and pierced by thylakoids. In chloroplasts, thylakoids are grouped by 2-6 in the form of plates, as in higher plants. In their structure, the chloroplasts of green algae are close to those of higher plants. Pigments - chlorophylls aand b, some Prasinoficians have chlorophyll c. Of the carotenoids are always present: β- carotene, lutein (most important), zeaxanthin, violaxanthin, antheraxanthin, neoxanthin. In briopsids, lutein may be absent or present in a small amount, and then siphonoxanthin, loroxanthin and siphonein become the most important, in some prasinophicians lutein may be replaced by prasinoxanthin. Siphonoxanthin and loroxanthin are also found in a number of Cladophoran species, siphonoxanthin in some Ulva. Cells of some representatives of green algae ( Chlamydomonas nivales, Haematococcus pluvialis, Trentepohlia) are colored red or orange colors, which is associated with the accumulation of carotenoid pigments and their derivatives outside the chloroplast (previously this complex was referred to as hematochrome). Some siphon algae have colorless amyloplasts in which starch is deposited. The vast majority of green algae contain at least one chloroplast and are capable of autotrophic nutrition. But at the same time, among them there are colorless representatives - obligate heterotrophs, such as Protothecaand Polytoma. A number of green algae are mixotrophs and, along with photosynthesis, are capable of using organic compounds dissolved in water, such as sugars, amino acids, and other small molecules (osmotrophic absorption), and are also capable of phagotrophic absorption of food particles (a number of prasinophic ones). Circular molecules of chloroplast DNA look like small balls (nucleoids) and are distributed throughout the chloroplast. DNA never organizes as a single circular nucleoid FlagellaThe monad representatives (zoospores and gametes) have two flagella unequal in length and morphology: on the main flagellum there are pinnate ciliated hairs, the lateral flagellum is flagella. The exception is synzoospores. Vaucheria, in which numerous pairs of smooth flagella slightly different in length are located along the surface. Flagella are attached to the cell subapically (in the spermatozoon Vaucherialateral attachment). Mastigonemes are synthesized in cisterns of the endoplasmic reticulum. A short flagellum ends with an acroneme. The basal bodies of tribophytic flagella are of typical structure, located at right angles to each other. The radicular system is represented by a cross-striated root - a rhizoplast and three microtubular roots, each of which consists of 3-4 microtubules. Monad cells and stages of green algae are isocont, rarely heterocont. The number of flagella per cell can be different - 1,2,4,8,16 or more (up to 120). In edogoniaceae and some briopsids, numerous flagella are collected in the form of a corolla at the anterior end of the cell; such cells are called stephanocont. A characteristic feature of the transitional zone of the flagella of green algae is the presence of a stellate body in it. Flagella of green algae do not have mastigonemes (unlike heterokonts), but may have fine hairs or scales. According to the arrangement of microtubule roots, the flagellar apparatus of green algae can be divided into two groups, which correspond to the two main phyletic groups of green algae. For the first group, which includes classes Chlorophyceae, Trebuxiophyceaeand Ulvophyceae, a cruciform arrangement of microtubule roots is characteristic, with two microtubule roots located perpendicular to the roots, in which the number of microtubules can vary. This arrangement of microtubule roots is called X-2-X-2. This entry reflects the fact that two roots usually contain two microtubules, while the other two roots may have a different number of microtubules (from 3 to 8 in different taxa). In algae from this group, there are three options for the location of the basal bodies of the flagella: the basal bodies are located opposite each other (12-6 hours) (class Chlorophyceae); basal bodies are displaced clockwise (1-7 h) and do not overlap (class Chlorophyceae); basal bodies are shifted counterclockwise (11-5 o'clock) and overlap (classes Trebuxiophyceaand Ulvophyceae). For the second group, which includes Charophyta, are characterized by an asymmetric arrangement of flagellar roots and the presence of a multilayer structure, which is a complexly organized group of microtubules located near the basal bodies. A very similar multilayer structure is known for flagellar spermatozoa of higher plants. It is also found in zooids in Trentepoliaceae, in Trebuxian algae. Myrmecia israeliensisand some prasinoficians. The multilayered structure appeared sporadically in other groups of algae, for example, in glaucocystophytes, euglena Eutreptiella, in some dinophytes. In addition to microtubule roots, green algae may have a rhizoplast that extends from the basal bodies to the nucleus. Cell wall In species with amoeboid, monadal and palmelloid organization, the cell wall is absent, they are covered only by a cytoplasmic membrane and can easily change shape. Sometimes the "naked" cells are inside the houses, the walls of which can be painted brown with manganese and iron salts. The vast majority of tribophytiums have a cell wall that is solid or consists of two parts. In its composition, studied in Tribonemaand Vaucheria, cellulose predominates and contains polysaccharides, consisting mainly of glucose and uronic acids. In young cells, the membrane is thin, with age it thickens. Iron salts can be deposited in it, the compounds of which color it in various shades of brown and red tones. Most often, silica is present in the cell wall, giving it hardness and luster. It can also be inlaid with lime and sculpted in various ways (spines, cells, warts, bristles, denticles, etc.). In attached forms, an outgrowth of the shell can form - a leg with an attachment sole. In filamentous algae with bivalve membranes, when the filaments break down, the cell membranes fall apart into H-shaped fragments, which are tightly connected halves of the membranes of two neighboring cells. During the growth of the filaments, an H-shaped fragment of the cell wall of two neighboring daughter cells is embedded between the two halves of the membrane of the mother cell. As a result, each of the daughter cells is half covered with the old membrane of the mother cell and half with the newly formed membrane. In the classes Chlorophyceous and Prasinophyceous, there are algae in which the cells are naked and lack a cell wall. In mesostigmata and many prasinophycia, organic scales are deposited on top of the plasmalemma. They are found in motile cells of a number of ulvae and charophytes. The presence of organic scales on motile cells is apparently a primitive sign. The appearance of theca in Prasinophycia and then in Chlorophycia is considered to be more progressive. The theca in Chlorophycia is composed of glycoproteins rich in hydroxyproline and associated with various oligosaccharides. In siphon algae, cellulose is either absent in the cell wall, then the main component is xylan (for example, Halimeda), or available as an admixture to mannal or xylan. The composition of the fibrillar part of the cell wall may vary depending on the phase of development. For example, in the shell of a sporophyte Bryopsismannan is present, and xylan and cellulose are present in the gametophyte. The chemical composition of the shell can change in different parts thallus. For example, at Codiumin the old parts, mannan is present in the shell, and in the young, undifferentiated parts, glucan. In most green algae, the main component of the cell wall is cellulose. It is synthesized by the enzyme cellulose synthetase, which is built into the plasma membrane of the cell. From 6 to 10 molecules of cellulose synthetase are grouped into subunits, which are then combined into terminal complexes. In green algae, two types of terminal complexes are known - rosette (in charophytes) and linear (in chlorophytes, ulvophytes). Rosette complexes, as in higher plants, consist of 6-8 subunits. Among charophytes, such complexes were found in Spirogyra, Micrasterias, Nitellaand Coleochaete. Some coccoid green algae have an additional layer in the shell, consisting of a sporopollenin-like substance. Reproduction Most yellow-green algae are known to reproduce vegetatively and asexually. Vegetative reproduction is carried out by dividing cells in half, disintegration of colonies and multicellular thalli into parts. During asexual reproduction, amoeboids, zoospores, synzoospores, hemisoospores, hemiautospores, autospores, aplanospores can be formed. Zoospores are "naked" and usually pear-shaped, with two flagella. The sexual process (iso-, hetero- and oogamous) is described in a few representatives. When adverse conditions occur, the formation of cysts is observed. Cysts (statospores) are endogenous, mononuclear, rarely multinuclear. Their wall often contains silica and consists of two unequal or less often equal parts. Reproduction of green algae is vegetative, asexual and sexual. Vegetativereproduction in unicellular, devoid of a membrane, occurs by dividing the cell in half (for example, Dunaliella), in colonial and multicellular organisms - fragments of the thallus, in characeae - special rhizoidal and stem nodules. asexualReproduction in green algae is widely represented. During asexual reproduction, the resulting zoospores may be naked or covered with a rigid cell wall. Coating of scales, such as in many prasinophycian motile reproductive cells, many ulvophytic and charophytic cells, is rare in chlorophytic reproductive cells. Zoospores after a period of movement stop, lose their flagella, round (in the case of naked zoospores) and develop into vegetative individuals. Aplanospores (non-motile spores) are asexual spores that lack flagella, but have contractile vacuoles. Aplanospores are considered as cells in which further development into zoospores is suspended. Autospores, which are smaller copies of immobile vegetative cells, lack contractile vacuoles. The formation of autospores correlates with the conquest of terrestrial conditions in which water cannot always be present in sufficient quantity. sexual processpresented various forms: chologamy, conjugation, isogamy, heterogamy, oogamy. Vkuoles Contractile vacuoles are present in mobile representatives. Usually there are 1-2 of them per cell, sometimes more. Golgi apparatus of a peculiar structure. Dictyosomes are small, contain 3-7 cisterns. Spare nutrients are oils, in some - volutin, chrysolaminarin and leukosin. Only freshwater monadic and palmelloid representatives have contractile (pulsating) vacuoles. Since the concentration of salts in the cell is higher than in the reservoir, water enters the cell, and its excess is removed by contractile vacuoles. Usually, the cell contains two contractile vacuoles located at the base of the flagella. They are reduced one by one. Nucleus The nucleus is one, less often there are many nuclei, in coenotic representatives the cells are always multinucleated. The details of mitosis have been studied in detail only in Vaucheria. Her mitosis is closed, with centrioles located at the poles outside the nucleus. Kinetochores were not found. During anaphase, the interpolar microtubules of the spindle are greatly elongated, which leads to a significant distance of the daughter nuclei from each other. The nuclear membrane is preserved, therefore, in telophase, the daughter nuclei look like a dumbbell. It is believed that such mitosis is not typical for the entire group of Tribophytaceae. the nucleus (sometimes several nuclei) is usually located in the wall layer of protoplasm or, suspended on plasma filaments, is located in the central part of the cell. mitosis can be closed, i.e. the nuclear membrane remains intact during mitosis. unusual shape semi-closed mitosis have Trebuxian algae. This is the so-called metacentric mitosis. With it, the centrioles during metaphase are located in the region of the metaphase plate, and not at the poles of the spindle. In charophytes, mitosis is open, the nuclear membrane disappears by the beginning of mitosis and then appears in the telophase, as in higher plants.

In the columns of the table, enter the generic names of the most famous forms of algae from various divisions of distribution in various environmental conditions:

seaweed green coloring structure

Various ecological conditionsFresh watersCold seasWarm seasHot springsTree barkrocksoilGeneric names of the most famous forms of algae from different divisions Chlorella, glitter flexible,ulotrix, microcystis, oscillatoriaceae, volvox, vosheria, cladophora, nitela, spirogyra, scenedesmus, chlamydomonas, pandorina, spirulina, lingbia, nostoc, anabena, aphanizomenonrivularia, gleotrichia, stygonema, paranema, astasia, facus, trachelomanas, gleocapedhames, euglena , dermocarp, prochlotrix KelpOscillatoria, Anfeltia, Cladophora, Fucus, Cystoseira, Prochloronmerismopedia, Dermocarpaspirulina, Lingbia, Anabena, Aphanizomenon, Rivularia Ulva Cystosira Phyllophora Oscillatoria acetabularia caulerpa cladophora macrocystis porphyra Prochloron merismopedia dermocarpa trichodesmium spirulina Lingbia OscillatoryMastigocladus PleurococcusChlorella Oscillatorium GleocapsMacrocystis Oscillatorium Gleocaps Calotrix stigonema OscillatoryLingbia vosheria Chlorella Gleokaps Nostok stigonema

GENERAL CHARACTERISTICS OF ALGAE

The difference between algae and other plants. Methods of feeding algae. Pigments of the photosynthetic apparatus. Phototrophic, heterotrophic and mixotrophic ways of feeding algae. Cell structure. The main types of morphological structure of the body of algae. Reproduction and development cycles of algae (vegetative, asexual, sexual reproduction). Change of generations and nuclear phases in the life cycles of algae.

Algae and environment. external conditions of life. Ecological groups of algae. Planktonic algae. Benthic algae. Terrestrial algae. Soil algae. Algae of snow and ice. Algae of saline water bodies. Glowing algae. Cohabitation of algae with other organisms.

The value of algae in nature and human life.

Algae classification.

SYSTEMATIC REVIEW OF ALGAE

Division of blue-green algae (Cyanophyta). Organization levels. Cell structure. The structure of the thallus. Reproduction. Classification. Classes chroococcal, hormogonium, chamesiphon. Origin, evolution and phylogeny. Ecological features. distribution and representatives. Meaning.

Department of green algae (Chlorophyta). Organization levels. Cell structure. Types of morphological organization of thalli. Reproduction methods. Significance in nature and human life. Department classification. Principles of classification. Classes are equal flagella, prasinophyceous, conjugates, char.

The class is equal flagella, or actually green algae. Orders volvox, chlorococcal, ulotrix. Unicellular, colonial and coenobial forms. The structure of multicellular thalli. Reproduction. Cell structure. main representatives.

Conjugate class. Features of the organization and structure of thalli. Reproduction methods. Characteristics and types of conjugation. The orders are mesothenic, desmidian, and zygnemic. distribution in nature. Representatives.

Chara class. The structure of the thallus. Reproduction methods. Ecology and meaning. main representatives.

Time of occurrence of green algae. Origin, evolution and phylogeny. The main lines of evolution within orders. Green algae as the ancestors of higher plants.

Department of diatoms (Diatomeae, Bacillariophyta). Features of the organization and structure of colonies . cytological features. Reproduction methods. Classification. The classes are pennate and centric. main representatives. Distribution, ecology, significance. Representatives. Time of occurrence, origin and phylogeny of diatoms.

Department of brown algae (Phaeophyta). Organization level. Anatomical and morphological structure of thalli. cytological features. Reproduction methods. Types of life cycles. Department classification. Classes isogenerate, heterogenerate, cyclosporic. main representatives. Spreading. Ecology. Meaning. Time of occurrence, origin and phylogeny of diatoms.

Algae is a group of organisms of different origin, united by the following features: the presence of chlorophyll and photoautotrophic nutrition; in multicellular - no clear differentiation body (called thallus, or thallus- one-cell, multi-cell, colonial) on organs ; lack of a pronounced conductive system; living in the aquatic environment or in wet conditions(in soil, damp places, etc.)

Morphological types: 1. amoeboid structure(named after Pellikulu - compacted peripheral part of the protoplast, serving as a shell) 2. Monad structure(single algae with undulipodia and solid cell wall) 3. coccoid(no tourniquet, there is a solid wall) 4. Palmelloid(many coccoid cells immersed in the general mucosa of the body) 5. Filamentous 6. lamellar(1, 2, many layers of cells) 7. Siphonal(thallus is not a class of partitions in the presence of a large number of nuclei) 8. Charophytic(large polyclonal thallus of a linear-segmented structure)

Aquatic algae: planktonic (phytoplankton - diatoms ) and benthic

Reproduction:vegetative(part of the thallus), asexual(zoospores and aplanospores) sexual(chologamy - draining whole individuals, isogamy, heterogamy, oogamy). Conjugation. Gametophycote and sporophycote. isomorphic(n=2n external) and heteromorphic generational change.

Systematics

Kingdom of Eukaryotes, or Nuclear (lat. Eucaryota)

Plant kingdom (lat. Plantae)

Subkingdom Algae (lat. Phycobionta)

Department Green algae (lat. Chlorophyta)

Department Euglenophyta (lat. Euglenophyta)

1 cell, more often 2 tourniquet, dense or elastic pellicle, 1 nucleus with closed mitosis and condensed chromosomes, plastids have a different shape and are surrounded by a tightly fitting layer of eps, chlorophyll a,b + ß-carotene + xanthophylls + others, there is a pyrenoid, paramylon is a glucose polymer for assimilation , some have a stigma - a peephole from ß-carotene, did not reveal sexual reproduction, nourished by phototrophic, saprotrophic (some have holozoic - ingestion of the mouth app), mixed,

Department Golden algae (lat. Chrysophyta) (often combined with brown algae) single class.

Department Yellow-green algae (lat. Xanthophyta)

Division Diatoms (lat. Bacillariophyta)

Department Dinophyta algae (lat. Dinophyta = Pyrrophyta)

Single cell, more often with 2 bundles, plankton in the main marine, auto, hetero and mixotrophs, dense cellulite wall - theca + pellicle under it, chlorophyll a,c + ɑ, β-carotenoids + brown pigments (fucoxanthin, peridinine), vova reserve - starch , fatty oil, reproduce: predominantly vegetative and asexual (various spores), sexual reproduction in some (isogamy)

Department Cryptophyte algae (lat. Cryptophyta)

Department Brown algae (lat. Phaeophyta)

Mainly benthic, Sargasso - secondarily plankton. Polyclinic Archaic - one or multi-row threads, the rest is large and dissected by the thallus. They are mucous membranes with cellulus and alginic cts, pectin layer + algin - sodium salt. Matrix im polysac fucoidan. They include inclusions - physodes - bubbles with a high content of polyphenols. Usually small disk-shaped plastids without pyrenoids, less often ribbon-like and lamellar with pyrenoids. Xanthophyll (fucoxanthin) + chlorophylls a, c + ß-carotene. The main food supply is the polysaccharide laminarin (deposited in the cytoplasm), alcohol mannitol, fats. 2n dominance Reproduce vegetative (with the help of parts of the thallus), asexual (2 bundles and motionless spores), sexes (isogamy, heterogamy, oogamy - 2 bundles). The zygote germinates without a dormant period. Often the generational change is iso or heteromorphic. Species: lamilaria, fucus.

Role in biogeocenoses 1. food 2. Soil sample 3. Silicon and calcium cycle 4. Photosynthesis 5 purification (+ wastewater) 6. Indicators of purity, salinity 7. Soil sample 8. Fertilizer 9. Agar 10. Algin gluing sva, paper dressing of leather, fabrics ( tablets, thread surgeon) 11. Algae are involved in the formation of some types of therapeutic mud. 12. Biofuel 13. In research work

Subkingdom of Bagryanka(Rhodobionta) . Crimson flowers are similar to cyanobacteria in a set of pigments (chlorophyll a, d, phycocyanin, phycoerythrin) and differ from all other plants in this way. They have a special crimson starch as a reserve substance. The cell membrane contains special pectin substances used by man under the name agaragar in microbiology and the confectionery industry.

The body of the purple thallus (thallus), in the form of multicellular filaments, forming pseudoparenchymal plates. They are attached to the substrate by rhizoids. The deepest inhabitants of the seas.

Reproduction is vegetative, sexual and asexual. A characteristic feature of the development cycle is the absence of flagellar stages, spores and gametes are always immobile, carried by a stream of water.

The sub-kingdom includes one department Rhodophyta, has about 4 thousand species.

Typical representatives of porphyry, nemalion, callitamnion. Let's consider the sexual reproduction of the purple on the example of a nemalion that lives in the Black Sea. The thallus of this algae consists of thin threads fastened into bundles. The oogonium is bottle-shaped and is called karpogon. The ovum matures in the enlarged part of the abdomen. The upper part of the karpogon is called the trichogyne. In numerous antheridia immobile male gametes of spermatozoa mature. With the flow of water, they passively move, stick to the trichogyne, the protoplasts of spermatozoa and eggs merge. From the resulting zygote, a carpospore is formed, giving rise to a new plant. Asexual reproduction is carried out by tetraspores.

Marine, attached, chlorophyll a, d + carotenoids + phycobiliproteins (phycoerythrins, phycocyanins + allophycocyanin), prod assim - purplish starch (deposited out of touch with plastids), im pseudoparenchymal thalli (interlacing by nia), im of mucous membranes (entrance to the composition of agar and carrageenan), cell wall 2 layers (pectin - external, hemicell internal) + some deposits of calcium carbonate, 1 or many nuclei, plastids are numerous in the form of grains or plates. Propagation of vegetative, sexes arr carpospores 2n (oogamy, female sex organ - carpogon developed on carpogonial branch - consists of an expanded abdomen, and a process of trichogyne, male - antheridia - nice colorless cells without spermatozoa) and asexual (ntetraspores). Species: porphyry (Porphyra)

Subkingdom True algae Phycobionta. It contains several divisions, of which we are considering 4: diatoms, brown, green and chara algae.

general characteristics: lower phototrophic plants that live mainly in water. The body is represented by a thallus (unicellular, multicellular or colonial) without dividing it into organs and tissues.

Division Diatoms Bacillariophyta. They differ sharply from other groups of algae in the presence of a solid silica shell (shell). Unicellular or colonial species. The cellulose shell is absent. The carapace consists of two halves of an epithecus and a hypotheca. Chloroplasts in the form of grains or plates. Pigments chlorophyll, carotene, xanthophyll, diatomine. Spare product fatty oil. Reproduction is vegetative and sexual. They live everywhere in the seas and fresh waters. Pinnularia representative.

Odnokl, im frustulu (silica shell), composed of epithecus (most of the lid) and hypotheca + pellicle, from a cat shell and arr. Solitary or colony, almost all autotrophs, but there are heterotrs. Plankton, benthos. There are centric (symmetrical), pennate (billaterally symmetrical), the cat is able to actively move, but they are not harnessed. Plastids vary in shape, with or without pyrenoids (in small ones). Chlorophyll a, c + ß, Ɛcaratins + brown xanthophylls (fucoxanthin, diatoxanthin, etc.). food stock - fatty oil, polysaccharides (chrysolaminarin, currency). Propagate the vegetative (div cl on the valves in two), sexes (isogamy, oogamy). All diatoms are 2n, n only gametes.

Division Brown algae Phaeophyta. Multicellular inhabitants of the seas, the largest known algae, sometimes up to 60 m long.

Cells have a nucleus, one or more vacuoles, the membranes are strongly mucilaginous. Chloroplasts are colored brown (pigments: chlorophyll a and c, carotene, xanthophyll, fucoxanthin). Spare product laminarin, mannitol and fats. Reproduction is vegetative, sexual and asexual with a clear alternation of generations according to isomorphic or heteromorphic type.

Representatives - kelp, fucus.

Division Green algae Chlorophyta. The largest department among algae, about 5 thousand species. Its representatives are very diverse in appearance: unicellular, multicellular, siphonal, filamentous and lamellar. They live in fresh or sea water, as well as on the soil.

A distinctive feature of the pigment composition is almost the same as in higher plants (chlorophyll a and b, carotenoids). Chloroplasts have a two-membrane membrane, are diverse in shape, and may contain pyrenoids. The cell membrane consists of cellulose and pectin. There are mobile forms with undulipodia. The reserve substance is starch, rarely oil.

Representatives: chlamydomonas is a unicellular algae, the sexual process is isogamous. Spirogyra is a filamentous algae. The sexual process is conjugation. Caulerpa is a non-cellular structure (siphonal), outwardly resembling stem plants. It is a giant cell with outgrowths sometimes up to 50 cm long, having a single protoplast with a continuous vacuole and numerous nuclei.

Single, siphon, multi-clear, filamentous, lamellar. In the main fresh, there is a fruit drink and a ground. Chlorophyll a, b, carotenes. pyrenoids present or not. CL single and multi-core. Cellulose pectin shell, rarely with pellicle only. Iso, heteromorphs. Stock - starch inside plastids, sometimes oil. Note: chlamydomanades, volvox, chlorella, spirogyra, characeae. Propagate vegetative (dividing into autospores), sexual (isogamy, less often hetero and oogamy (arr oospore), 2, 4, multi-burnt). Conjugation in filamentous spirogyres.

Types of life cycles of green algae: 1. Haplophase - algae develop in a haploid state, only the zygote is diploid (with zygotic reduction). Hapl spores (asexual reproduction). Gametes (n) - fusion - zygote (2n) - dormancy - germinates after reduction in the number of chromosomes - haploid seedlings. Most algae 2. Diplophase - diploid algae, and haploid gametiphyte (diatoms, siphon from green, cyclospore from brown). Thallus - 2n. Propagation - sex and vegetative. Before the burden of gametes - meiosis - copulation of haploid hapl gametes - zygote 2n. Gametic reduction. 3. Haplodiplophase - algae has a haploid gametophyte, gametes are combined in pairs - a zygote that germinates in a diploid thallus, on which spores. Sporic reduction. M.b. haplodiplophase life cycle with somatic reduction (less often)

Division Charophyta Charophyta. Multicellular, divided into parts, outwardly similar to higher plants. Reproduction is vegetative and sexual (oogamous). The oogonium has a characteristic structure, with a sheath of 5 spirally twisted cells, forming a crown at the top. Antheridium is spherical. The zygote, after a dormant period, germinates into a new plant. The representative is a fragile character.

The value of algae. A huge role in the creation of organic substances and oxygen on the planet, in the circulation of substances, as well as in the nutrition of the inhabitants of reservoirs. They can carry out self-purification of water. Many algae are indicators of habitat pollution. They can be used as food for humans and farm animals, as well as fertilizers. Used to obtain agaragar, sodium alginate (glue). In medicine, kelp, fucus, spirulina are used.

How beautiful and amazing the underwater world is, it is just as mysterious. Until now, scientists have discovered some completely new, unusual species of animals, the incredible properties of plants are being investigated, and the areas of their application are expanding.

The flora of the oceans, seas, rivers, lakes and swamps is not as diverse as the terrestrial one, but it is also unique and beautiful. Let's try to figure out what these amazing structures of algae are and their significance in the life of humans and other living beings.

Systematic position in the system of the organic world

By generally accepted standards, algae are considered a group of lower plants. They are part of the Cellular Empire and the sub-kingdom of Lower Plants. In fact, such a division is based precisely on the structural features of these representatives.

They got their name because they are able to grow and live under water. Latin name- Algae. Hence the name of the science involved in the detailed study of these organisms, their economic importance and structure, - algology.

Algae classification

Modern data allow us to attribute all available information about different types of representatives to ten departments. The division is based on the structure and activity of algae.

1. Blue-green unicellular, or cyanobacteria. Representatives: cyanide, shotguns, microcystis and others.
2. diatoms. These include pinnularia, navicula, pleurosigma, melosira, gomphonema, sinedra and others.
3. Golden. Representatives: chrysodendron, chromulina, primnesium and others.
4. Porphyry. These include porphyry.
5. Brown. cystoseira and others.
6. Yellow-green. This includes classes such as Xanthopod, Xanthococcus, Xanthomonad.
7. Red. Gracilaria, anfeltia, crimson.
8. Greens. Chlamydomonas, Volvox, Chlorella and others.
9. Evshenovye. These include the most primitive representatives of the greens.
10. as the main representative.

This classification does not reflect the structure of algae, but only shows their ability to photosynthesize at different depths, showing pigmentation of one color or another. That is, the color of the plant is the sign by which it is assigned to one or another department.

Algae: structural features

Their main distinguishing feature is that the body is not differentiated into parts. That is, algae do not, like higher plants, have a clear division into a shoot, consisting of a stem, leaves and a flower, and a root system. The structure of the body of algae is represented by a thallus, or thallus.

In addition, the root system is also missing. Instead, there are special translucent thin thread-like processes called rhizoids. They perform the function of attachment to the substrate, while acting like suction cups.

The thallus itself can be very diverse in shape and color. Sometimes in some representatives it strongly resembles the shoot of higher plants. Thus, the structure of algae is very specific for each department, therefore, in the future, it will be considered in more detail using examples of the corresponding representatives.

Types of thalli

Thallus is the main distinguishing feature of any multicellular algae. The structural features of this organ are that the thallus can be of different types.

1. Amoeboid.
2. Monadic.
3. Capsular.
4. coccoid.
5. Filamentous, or trichal.
6. Sarcinoid.
7. False tissue.
8. Siphon.
9. Pseudoparenchymal.

The first three are most typical for colonial and unicellular forms, the rest for more advanced, multicellular, complex in organization.

This classification is only approximate, since each type has transitional options, and then it is almost impossible to distinguish one from the other. The line of differentiation is blurred.

Algae cell, its structure

The peculiarity of these plants lies initially in the structure of their cells. It is somewhat different from that of the higher representatives. There are several main points by which cells are distinguished.

1. In some individuals, they contain specialized structures of animal origin - movement organelles (flagella).
2. Sometimes there is stigma.
3. The shells are not quite the same as those of an ordinary plant cell. Often they are provided with additional carbohydrate or lipid layers.
4. Pigments are enclosed in a specialized organ - the chromatophore.

The rest of the structure of the algae cell obeys general rules that of higher plants. They also have:

• nucleus and chromatin;
• chloroplasts, chromoplasts and other pigment-containing structures;
• vacuoles with cell sap;
• cell wall;
• mitochondria, lysosomes, ribosomes;
• Golgi apparatus, and other elements.

At the same time, the cellular structure of unicellular algae corresponds to that of prokaryotic creatures. That is, the nucleus, chloroplasts, mitochondria and some other structures are also missing.

The cellular structure of multicellular algae is fully consistent with that of higher land plants, with the exception of some specific features.

Department of Green Algae: structure

This section includes the following types:

• unicellular;
• multicellular;
• colonial.

In total there are more than thirteen thousand species. Main classes:

• Volvox.
• Conjugates.
• Ulotrix.
• Siphon.
• Protococcal.

The structural features of unicellular organisms lie in the fact that the outside of the cell is often covered with an additional shell that performs the function of a kind of skeleton - the pellicle. This allows it to be protected from external influences, keep a certain shape, and also, over time, form beautiful and beautiful surfaces on the surface. amazing patterns from metal ions and salts.

As a rule, the structure of green algae of a unicellular type necessarily includes some kind of organelle of movement, most often a flagellum at the posterior end of the body. The reserve nutrient is starch, oil or flour. The main representatives: chlorella, chlamydomonas, volvox, chlorococcus, protococcus.

Such representatives of siphons as caulerpa, codium, acetobularia are very interesting. Their thallus is not a filamentous or lamellar type, but one giant cell that performs all the basic functions of life.

Multicellular organisms may have a lamellar or filamentous structure. If we are talking about lamellar forms, then often they are multi-layered, and not just single-layered. Often the structure of this type of algae is very similar to the shoots of higher land plants. The more branches of the thallus, the stronger the similarity.

The main representatives are the following classes:

• Ulotrix - ulotrix, ulva, monostroma.
• Couplings, or conjugates - zygonema, spirogyra, muzhotsia.

Colonial forms are special. The structure of green algae of this type consists in the close interaction between a large accumulation of unicellular representatives, united, as a rule, by mucus in the external environment. The main representatives can be considered volvox, protococcal.

Features of life

The main habitats are fresh water bodies and seas, oceans. Often cause the so-called flowering of water, covering its entire surface. Chlorella is widely used in cattle breeding, as it purifies and enriches water with oxygen, and goes to feed livestock.

Unicellular green algae can be used in spacecraft to produce oxygen through photosynthesis without changing their structure and dying. According to the time period, this particular department is the most ancient in the history of underwater plants.

Department Red Algae

Another name of the department is Bagryanki. It appeared due to the special color of the representatives of this group of plants. It's all about the pigments. The structure of the red alga as a whole satisfies all the main features of the structure of lower plants. They can also be unicellular and multicellular, have a thallus of various types. There are both large and extremely small representatives.

However, their color is due to some features - along with chlorophyll, these algae have a number of other pigments:

• carotenoids;
• phycobilins.

They mask the main green pigment, so the color of plants can vary from yellow to bright red and crimson. This happens due to the absorption of almost all wavelengths of visible light. The main representatives: anfeltia, phyllophora, gracilaria, porphyry and others.

Meaning and lifestyle

They are able to live in fresh waters, but the majority are still marine representatives. The structure of the red algae, and specifically the ability to produce a special substance agar-agar, allows it to be widely used in everyday life. This is especially true for the food confectionery industry. Also, a significant part of the individuals is used in medicine and directly eaten by people.

Department Brown algae: structure

Often, as part of the school program for studying lower plants, their various departments, the teacher asks students: “List the structural features The answer will be this: the thallus has the most complex structure of all known individuals of lower plants; inside the thallus, which is often of an impressive size, there are conducting vessels; the thallus has a multilayer structure, which is why it resembles the tissue type of the structure of higher land plants.

The cells of the representatives of these algae produce a special mucus, so the outside is always covered with a kind of layer. Reserve nutrients are:

• carbohydrate laminar;
• oils (fats different type);
• alcohol mannitol.

Here's what to say if you are asked: "List the structural features of brown algae." There are actually a lot of them, and they are unique compared to other representatives of underwater plants.

Household use and distribution

Brown algae is the main source of organic compounds not only for marine herbivores, but also for people living in the coastal zone. Their consumption is widespread among different peoples peace. Medicines are made from them, flour and minerals, alginic acids are obtained.

1.4. DEPARTMENT OF CYANOBACTERIA (CYAN ABOUT BACTERIA), OR BLUE-GREEN ALGAE (CYANOPHYTA)

Cyanobacteria, or blue-green algae (or cyanes), are the most ancient, morphologically and physiologically unique group of organisms. Many properties of blue-green algae (nitrogen fixation, intravital release of organic substances, oxygenic type of photosynthesis) determine their extremely important role in soil and water bodies. AT recent times cyanoeas have become the objects of research by biochemists and physiologists, hydro- and microbiologists, geneticists and plant growers, as well as specialists in space biology.

The department includes unicellular, colonial and multicellular (filamentous), from microscopic to visible to the naked eye organisms of various morphological structures. Colonial forms exist throughout life or at separate stages of development of the alga. Multicellular cyanideas live in separate threads or are collected in sods. They have symmetrical or asymmetrical, simple or branched trichomes (bodies), intercalary or apical growth zones. A number of filamentous cyanides have specialized cells - heterocysts with strongly thickened colorless two-layer shells. They take part in the process of atmospheric nitrogen fixation.

The cell is dressed in a pectin membrane of complex structure and composition, often mucilaginous, under which there is a protoplast, usually devoid of vacuoles with cell sap. The cell lacks a separate nucleus, chromatophores, Golgi apparatus, mitochondria, and endoplasmic reticulum.

The cytoplasm is divided into the central part - the centroplasm (nucleoplasm) and the colored peripheral part - the chromatoplasm. The structure of the centroplasm - an analog of the nucleus in blue-green algae - is close to the identical structures of bacterial cells and differs significantly from the structure of cells with formed nuclei.

The chromatoplasm contains photosynthetic lamellar structures and pigments: chlorophyll a, carotenoids and bilichromoproteins (blue phycocyanin and allophycocyanin and red phycoerythrin), which absorb light in the 540–630 nm region, which is poorly used by all other photosynthetic organisms (this ability is red algae). Due to the unique and labile composition of pigments, cyanide is able to absorb light of various wavelengths.

Reserve substances are represented by glycogen, volutin, cyanophycin grains. Many blue-green algae have gas vacuoles in their cytoplasm.

Cyanides reproduce by simple binary cell division, the collapse of colonies, fragmentation of threads into separate sections of the thallus - hormogony, capable of germinating into new thalli, as well as gonidia, cocci, planococci. Gonidia - small cells with a mucous membrane, separated from the thallus or located inside the endospores.

cocci - unicellular fragments of the thallus that do not have a clearly defined shell.

Planococci - small naked cells capable of independent movement.

Many filamentous cyanides form spores (akinetes) from one, and sometimes from two or more adjacent vegetative cells, which serve mainly to endure unfavorable conditions. Sporulation is characteristic of Nostoc and Chamesiphon, the latter form exo- and endospores that serve for reproduction.

The sexual process and mobile flagellar forms and stages of development in cyanobacteria have not been identified.

Blue-green algae are common in fresh and salt waters, on the surface of the soil, rocks, in hot springs, and are part of lichens. Together with bacteria cyanide enrich the soil with organic matter and nitrogen, contribute to the eutrophication of water bodies, are food for zooplankton and fish, can be used to obtain a number of valuable substances produced by them in the course of their vital activity (amino acids, vitamin B 12 , pigments, etc.) During the period of mass reproduction in reservoirs, the so-called "bloom" of water, some cyanides are toxic to aquatic animals. Some species can be used for food.

Blue-green algae are divided into 3 classes: Chroococcophyceous, Hamesiphonophyceous and Hormogoniophyceous. The classification is based on the structural features of the thallus and the reproduction of cyanide.

Class Chroococcophytes ( Chroococcophyceae)

The class includes colonial and unicellular organisms. Colonies are formed mainly by cells that have not dispersed after division, less often by their adhesion. The cells in the colony are arranged mostly randomly. They are not differentiated into bottoms and tops. They reproduce vegetatively. Heterocysts, as well as endo- and exospores are absent. There are 2 orders and 35 genera in a class.

Order Chroococcal (Chroococcales). It combines widespread unicellular and colonial forms, free-floating or lying on the substrate. Some representatives lead an attached lifestyle.

Genus Microcystis (Microcystis)- These are microscopic, as a rule, shapeless lumps of mucus, in which randomly located small spherical cells are immersed. In many species, cells appear almost black under a microscope due to the abundance of gas vacuoles in them, due to which

nii float to the surface of the water. The outlines of the mucus of this colony can be very diverse, and sometimes peculiar cells appear in the mucus, due to which the colonies become reticulated (Fig. 1.1).

About 25 species are known, distributed in fresh and marine waters, as well as in the soil. In Belarus, 19 species and 26 varieties* have been identified. Found in reservoirs, lakes and rivers. The most common M. bluish-green (M. aeruginosa), M. Greville (M grevillei) and M. powdery (M pulverea). Some species are toxic.

Class Hormogoniophyceous ( Hormogoniophyceae)

The class includes multicellular algae of a filamentous or trichome form, in which the protoplasts of neighboring cells are interconnected by plasmodesmata. Trichomes are naked or covered with mucous sheaths. Many of them are characterized by heterocysts. Reproduction occurs by hormogonia, less often by akinetes. The class has over 10 orders. The most important of them are oscillatory and nostocal.

Order Oscillatory(Oscillatoriales). Includes species that have single-row homocytic trichomes, which consist of the same cells, with the exception of the apical one. Trichomes do not have heterocysts and are almost always devoid of spores, often mobile in a vegetative state.

Most of the filamentous blue-green algae belong to this order.

Genus Oscillatoria (Oscillatoria) includes species that often form blue-green films that cover wet ground after rain, underwater objects and plants, drag the muddy bottom and water surface of stagnant reservoirs.

The oscillator is a long blue-green filament. By observing the end of the thread under a microscope, one can notice its oscillatory movements. This oscillation is accompanied by the rotation of the thread around its own axis and its translational movement.

With a high magnification of the microscope, it can be seen that the threads are made up of identical cylindrical cells, with the exception of the apical ones, which are somewhat different in shape from the rest (Fig. 1.2).

Inside the cell, one can see granular inclusions - cyanophycin grains, located, as a rule, along the transverse partitions. The thread multiplies by breaking up into separate sections - hormogonia, growing into new threads.

More than 100 species are known. In Belarus, 39 species and 49 varieties have been identified. They live in the benthos and plankton of mainly fresh water bodies, sometimes causing them to "bloom". Attached to underwater objects. Live in the silt

wet sand or soil, and are also found in sewage. The most common in the plankton of ponds and lakes: O. lake ( O. limnetica), O. planktonic (O. planctonica), O. muddy (O. limosa), O. thin (O. tenuis). O. slender is found everywhere on piles, stones, and the surface of stagnant water. (O. formosa).

Nostocal order(Nostocales). It combines hormogonian algae with heterocytic unbranched filaments or filaments with false branching (due to the breakthrough of the trichomes to the side), often with akinetes. Trichomes come with or without sheaths.

Genus Anabena (Anabaena) of the family of the same name is represented by single or irregular clusters of trichomes. Trichomes are symmetrical, consisting of round or barrel-shaped vegetative cells with intermediate heterocysts, mostly free-floating, straight or curved. Anabena species are found both in plankton and in benthos. Reproduction is carried out by hormogonia, into which the threads break down, as a rule, along heterocysts. Hormogonia grow only due to transverse cell divisions. In addition, in these algae, individual vegetative cells, due to strong growth, turn into akinetes (Fig. 1.3). Akinetes are much larger than vegetative cells and are distinguished by their bright blue-green color against the background of other cells almost black from gas vacuoles. The contents of the akinetes are usually granular, which in most cases is due to the accumulation of cyanophycin grains. About 100 species are known, 28 of them are in Belarus. They are found in fresh water plankton, some in brackish water and on moist soil. The most common A. Gassala (A. hassalii), A. Sheremetyeva (A. scheremetievii), A. changeable (A. variabilis), A. spiral (A. spiroides), A. "blooming" water (A.flos-aquae) and etc.

Genus Nostoc (Nostoc) characterized by complex mucous or gelatinous colonies of various sizes (from microscopically small to large, reaching the size of a plum) and shape, often spherical. In the mucus there are intricately intertwined threads, similar to the threads of anabaena. Reproduces by hormogonia. They become mobile and leave the mother colony, the mucus of which is blurred by this time. After a certain period of movement, the hormogonia stop, lose their gas vacuoles (in benthic species), and grow into spirally twisted filaments. Then, as a result of repeated divisions of hormogony cells, a zigzag thread is formed by longitudinal or oblique partitions, which is characteristic of nostocs. These threads are covered with abundant mucus and thus a young colony appears (Fig. 1.4). Sporulation is also observed, in which many vegetative cells turn into akinetes, usually little different in shape and size from vegetative cells.

Nostok species (more than 50, including 8 in Belarus) are widespread in water bodies and on soil. Some species are edible. A typical representative of the genus - N. plum-shaped (N. pruniforme), listed in the Red Book of the Republic of Belarus.

Genus Gleotrichia (Gloeotrichia) includes species in which the threads are connected by a common mucus into spherical or hemispherical colonies. Asymmetrical string-like filaments inside the mucus are located radially, have widened ends, bearing heterocysts and akinetes facing the inside of the colony (Fig. 1.5). Reproduces by hormogonia. 15 species are known, including 3 in Belarus. They are found mainly in stagnant fresh water bodies; first attached to the substrate, then swim freely; of these, only two species are planktonic organisms. Widespread G. floating ( G. natans) and G. pisiform (G. pisum).

Tasks

1. Consider and draw a general view of a microcystis colony, several individual cells with gas vacuoles.

2. Place a drop from a bottle with an oscillatorium on a glass slide and examine it under a microscope, first at low magnification, then at high magnification. Draw part of the trichome. Note the cylindrical shape of the vegetative cells, the rounded shape of the apical cells, the thin pectin membrane, the strongly colored peripheral layer of the cytoplasm - the chromatoplasm and the lighter centroplasm, the cyanophycin grains.

3. Consider and draw the thread of the anabaena. Mark vegetative cells with gas vacuoles, heterocysts and akinetes.

4. With dissecting needles, separate a piece of mucus from the peripheral part of the nostoc colony, place it in a drop of water on a glass slide and examine it under a microscope. Draw a general view of a part of the colony at low magnification and a separate thread at high magnification. Note vegetative cells and heterocysts.

5. Consider and draw a colony of gleotrichia. Then destroy the colony, take a piece of mucus containing gleotrichia filaments, and examine it under a microscope. Note that the heterocyst lies at the base of the thread. The cells that make up the thread, as they move away from the heterocyst, become thinner and at the top turn into a colorless hair.

Questions for self-control

1. How do cyanobacteria differ from phototrophic green and purple bacteria in terms of body structure, pigment set, and type of photosynthesis?

2. How does the cell structure of blue-green algae differ from the cell structure of other organisms?

3. What forms of thallus organization and reproduction are known in cyanide?

4. What pigments and reserve products are noted in the cells of blue-green algae?

5. What is the uniqueness of the photosynthetic apparatus of blue-green algae?

6. What are the features of the structure and function of heterocysts and akinetes?

7. What is the importance of blue-green algae in nature and the national economy?

1.5. DEPARTMENT OF EUGLENIC ALGAE (EUGLENOPHYTA)

The department includes microscopic unicellular organisms equipped with one or two flagella and actively moving. The body shape of euglena algae is elongated, oval, elliptical or fusiform. There is no cellulose shell; its role is played by the outer compacted layer of the cytoplasm - the pellicle. Those species in which the pellicle is soft, elastic, have the ability to change the shape of the body. Few algae have a hard outer shell, usually impregnated with iron salts, which does not adhere tightly to the protoplast. The number and shape of chromatophores are different. They are spindle-shaped, ribbon-shaped, disc-shaped, stellate, lamellar. The green color of eugleno algae is due to the presence of chlorophylls. a and b. In addition to them, there are carotenes and xanthophylls. The reserve product is paramylon, a derivative of glucose; it is deposited on the outer parts of the pyrenoids protruding from the chromatophores in the form of shells or in the cytoplasm in the form of small grains.

At the anterior end of the euglenophyta is a depression, often called the pharynx. It is the output end for the system of contractile vacuoles, in which fluid accumulates with dissolved metabolic products.

The movement of euglena algae is carried out due to metabolic changes in the shape of the body and with the help of a flagellum.

Reproduction occurs by longitudinal division of the cell in half in a mobile or immobile state. Under unfavorable conditions, some euglena algae form dormant cysts with thick shells. The sexual process has not been proven.

Euglena algae are common inhabitants of small fresh stagnant water bodies, causing a “bloom” of water during mass development. This group of plants is characterized by all three main types of nutrition: phototrophic, saprotrophic, and holozoic (ingestion of formed particles of organic matter or small organisms), sometimes mixed (mixotrophic).

The department includes class 1 Euglenophycia.

Class Euglenophycia (Euglenophyceae)

The class combines several orders, the differences between which are based mainly on the details of the structure of the flagellar apparatus.

Representatives of the order Euglenales (Euglenales) can serve as the genera Euglena, Trachelomonas and Facus.

Algae genus Euglena (Euglena) cells are motile, spindle-, ovoid- and ribbon-shaped, cylindrical, more or less spirally twisted. The anterior end is narrowed and rounded, the posterior end is pointed, rarely rounded or with a narrow styloid process (Fig. 1.6). At the anterior end of the cell there is a stigma, pulsating vacuoles and a pharyngeal opening, from which one of the flagella emerges, and the second, short, is located inside the pharynx. Single nucleus, one to several chromatophores, with or without pyrenoids.

155 species are known, distributed mainly in small fresh water bodies (puddles, lakes, rivers), swamps, and on wet soil. Some species cause the water to "bloom" green or red. 25 species are known in Belarus. Often found E. green ( E. viridis), E. spirogyra (E. spirogyra), E. needle (£. acus), E. caudate (E. caudata) and others. Euglenophytes can serve as indicators of water quality.

includes free-swimming organisms with a flagellum and a solid house. The structure of the house is a characteristic feature of the species. The houses have a different shape, as a rule, they are brown in color and in front there is a hole for the tourniquet to exit (Fig. 1.7). The walls are smooth or with pores, papillae, granules, spines. Chromatophores (two or more) green, with or without pyrenoids. There are species without chlorophyll - saprotrophs. During reproduction, the cell divides inside the house: one of the daughter individuals slips out through the hole and develops a new house.

About 200 species are known, in Belarus there are 57 and 84 varieties, common in shallow reservoirs with fresh water. The most famous T. volvox ( T. volvocina), T. small-bristle (T. hispida), T. armed (T. armata), T. oblong (T. oblonga), T. ovoid (T. ovata) and etc.

Species genus Facus (Phacus)(Fig. 1.8) cells are flattened, more or less corkscrew-shaped, asymmetrical, ovoid, oval or spherical, with one flagellum, often with a colorless steering process at the posterior end of the body. The pellicle is dense, colorless, with streaks or rows of granules, papillae, or spines. Chromatophores numerous, small, discoid, near-wall, without pyrenoids. The nucleus is one (usually in the back of the cell). The protoplast contains paramylon grains.

About 140 species are known, distributed in shallow stagnant water bodies or in the coastal part of lakes and rivers polluted with organic substances. In Belarus, there are 18 species and 27 varieties. The most common F. longtail (Ph. longicauda), F. fine bubble (Ph. vesiculosum), F. round (Ph. orbicularis), F. caudate (Ph. caudatus) and etc.

Exercise

Examine at high magnification of the microscope and draw the cells of euglena, phacus and trachelomonas. Note the structural features of the house, a colorless straight process at the phacus and a neck or funnel in trachelomonas, a nucleus, chromatophores, a flagellum at the anterior end of the body. (To see the flagella, stain the slide with 2% methylene blue or iodine in potassium iodide.)

Questions for self-control

1. What are the features of the structure and lifestyle of euglena algae?

2. What is the significance of some representatives of euglena algae for characterizing the degree of water pollution?

3. In what cases do euglena algae switch to a mixotrophic mode of nutrition?

1.6. DIVINOPHYTE ALGAE DEPARTMENT (DINOPHYTA)

Most dinophyte algae have a monadic structure and are represented by single cells. Less common are amoeboid, palmelloid, coccoid and filamentous forms. They are characterized by a dorsoventral body shape: the dorsal and ventral sides are clearly expressed in the structure of the cells, the difference between the anterior and posterior ends of the body is clearly visible.

An important feature for all dinophytes is also the presence of two grooves in the cells. One of them - transverse - covers the cell in a ring or spiral, but does not close completely, the other - longitudinal - is located on the ventral side of the cell.

The cell cover in the most primitive forms is represented by a smooth thin periplast(spherical shapes). Most dinophytes are covered current, consisting of a cytoplasmic membrane, under which the theca components are located in one layer - flattened blisters (vesicles, cisterns) surrounded by a membrane.

Two flagella different in length, structure, and even functions (one of them is swimming, the other is steering) are attached on the ventral side; one is almost completely hidden in the transverse groove, the other protrudes from the longitudinal groove and is directed along the backward movement of the cell. Many unicellular algae have a so-called pharynx (a kind of tube) and special mucous bodies that strongly refract light - trichocysts, located in the peripheral layer of the cytoplasm or in longitudinal rows on the inner surface of the pharynx. Contacting during movement with another algae or grain of sand, trichocysts are ejected in the form of long mucous threads, causing an abrupt movement of the cell.

Dinophyte algae are characterized by the so-called mesokaryotic type of cell organization with a nuclear apparatus, which still retains the features of some primitiveness. This is expressed in the chemical composition of chromosomes (absence of histones) and their behavior during mitosis, the phases of which are atypical; in particular, chromosomes that are poorly differentiated in length due to the absence of centromeres are constantly in a condensed state and are preserved in the interphase nucleus. There may be one or more nucleoli in the nucleus, which usually disappear during division. During mitosis, the nuclear envelope does not disappear and the fission spindle does not form.

The protoplast contains chromatophores of various colors (olive, brown or brown, yellow, golden, red, blue, blue). The color is due to the presence of chlorophylls a and c, carotenes a, )