Algae is a general characteristic. Classification, nutrition, habitats

Topic: CLASSIFICATION OF PLANTS. SEAWEED. Lecture plan 1. Classification of plants. Systematics. 2. General characteristics of algae. 3. Division Blue-green algae (Cyanophyta). 4. Division Yellow-green algae (Xanthophyta). 5. Division Diatoms (Diatomophyta). 6. Division Brown algae (Phaeophyta). 7. Division Red algae (Rhodophyta). 8. Division Green algae (Chlorophyta). 9. Department of Chara algae (Charophyta).

1. Classification of plants. Systematics is the science of the diversity of living organisms, methods of their description and regularities of occurrence. The ultimate goal of taxonomy is to build a system of the organic world - a unified classification. Systematics faces two tasks: - the distribution of living beings into groups. - Description and naming of living beings. In accordance with these tasks, systematics is divided into two constituent disciplines: axonomy and nomenclature. t

Taxonomy is the science of organizing living beings into groups based on the analysis of their inherent features. The most significant signs are called diagnostic. Based on diagnostic characters, organisms are grouped into groups called taxa. A taxon is a group of individuals created during a classification process. Hierarchy - the arrangement of groups of objects in the order of subordination, that is, the inclusion of some groups in others. For all groups of organisms, a single hierarchy system is adopted, formed by generally accepted taxonomic categories.

taxonomic categories. 1. Imperia empire; 2. Dominion dominion; 3. Regnum kingdom; 4. Divislo department, Phylum phylum; Typos type; 5.classis class; 6. Ordo order, detachment; 7. Familia family; 8. Tribus tribe, knee; 9. Genus genus; 10. Sectio section; 11. Series series; 12.species view; 13 Var. Setas variety, variety; 14.Forma form; 15. Forma specialis is a specialized form. The prefixes “under” (sub) and “above” (super) are used for additional categories, for example, subregnum - sub-kingdom or superordo - superorder

Nomenclature is a system of rules for describing living beings and naming organisms and their groups in order to facilitate their identification. To streamline this process and subordinate it to certain rules, nomenclature codes are created. Codes of nomenclature - sets of rules governing the principles of the nomenclature of a particular group of living beings.

Basic nomenclature codes. Ø "International Code of Botanical Nomenclature" (ICBN); Ø "International Code of Zoological Nomenclature (ICZN)"; Ø "International Code of Nomenclature for Bacteria (ICNB)"; Ø "International Code of Classification and Nomenclature of Viruses" (ICVCN); Ø "International Code of Nomenclature for Cultivated Plants" (ICNCP). There is a development of a unified "International Code of Biological Nomenclature" (Bio. Code).

The first set of rules for botanical nomenclature 1867 Alphonse Decandol. In 1952, the first "International Code of Botanical Nomenclature" was adopted in Stockholm. All changes and additions are made to the nomenclature codes in accordance with the decisions international congresses– botanical (IBC), zoological (IZC), bacteriological (ICB) and virological (IVC). International forums meet every 4-5 years to solve the most important taxonomic and nomenclatural problems.

2. General characteristics of algae. Algae (Algae) - a set of departments, mainly aquatic organisms. Algae do not have real organs and tissues, and therefore, the body of multicellular forms is represented by thallus. Structural features. Algae can be unicellular, colonial, and multicellular; depending on the location of the cells - filamentous, lamellar or complexly branched.

The vegetative cells of the algae thallus consist of: Ø a solid cell wall made of cellulose and pectin substances. Ø cytoplasm. vacuole with cell sap. one or more nuclei. chloroplasts (lamellar, cylindrical, ribbon-like, cup-shaped, stellate, etc.). Pyrenoids are protein bodies around which starch, oils, leukosin, volutin are deposited.

Vegetative reproduction in unicellular organisms occurs by cell division, in colonial ones by the breakdown of the colony into parts, in multicellular organisms by parts of the thallus, and sometimes by the formation of special organs of vegetative reproduction.

Actually asexual reproduction is carried out with the help of zoospores or spores that arise inside vegetative cells or in special organs - zoosporangia or sporangia. After entering the water, zoospores drop flagella, become covered with a cell membrane and germinate into a new individual.

The sexual process in algae can be in various forms: iso, hetero and oogamy. Iso and heterogametes are formed in ordinary vegetative cells, eggs - in oogonia, spermatozoa - in antheridia. In some algae, a sexual process is observed in the form of somatogamy (conjugation), the fusion of the protoplasts of two vegetative cells. The end result of the sexual process is the formation of a zygote.

Individuals that form spores are called sporophytes, and those that form gametes are called gametophytes. They can be bisexual and dioecious. Most algae are independent plants. In some species, spores and gametes are formed on the same plants, they are called sporogametophytes. The sporophyte and gametophyte may have the same structure (isomorphic generational change) or different (heteromorphic generational change).

The ratio of development phases in the life cycle depends on when meiosis occurs: Ø if the zygote germinates, then all life passes in the haploid phase, only the zygote is diploid.

Ø during the formation of gametes - then all life passes in the diploid phase, only gametes are haploid;

Ø if during the formation of spores, then the diploid and haploid phases alternate in the life cycle.

Distribution and economic importance of algae. Habitat: Ø Water, mostly sea water. Part of the algae floating on the surface and in the upper layer of water form plankton, the other part freely lie on the bottom or attach to it is called benthos. Ø Algae live on the soil, in the soil. Ø In atmospheric air (some types of chlorella). Separate types, getting together with bacteria on barren substrates, become the pioneers of their settlement.

Ø Ø Ø Fix and accumulate nitrogen in the soil. They are part of the complex organisms of lichens. serve as food for fish and waterfowl. Receive flour for feed. X. animals. Used as fertilizer. Brown and red algae are the source of agar, and their ash is the raw material for the production of bromine and iodine. Ø Some algae are used as food by humans and serve as raw materials for the pharmaceutical industry.

3. Division Blue-green algae (Cyanophyta). These are prokaryotes - cyanobacteria. The total number of species is about 1.4 thousand. Structure. These are colonial and multicellular, less often unicellular organisms of various colors (blue-green, olive, dark green). The color is due to pigments that are contained in the cells in different combinations: Ø phycocyanin (blue-green); Ø chlorophyll (green); Ø carotenoids (yellow); Ø phycoerythrin (red).

Structure In the cells of blue-green algae there are no isolated nuclei, chloroplasts, mitochondria and vacuoles with cell sap. The cell wall is mostly pectin and is easily mucilaginous. The cell cavity is filled with cytoplasm, which is divided into two layers: chromatoplasm - a dense wall layer containing membranes with pigments, and centroplasm (nucleoid) - a colorless central part containing DNA.

Multicellular blue-green algae are usually filament-shaped. The protoplasts of adjacent cells are connected by plasmodesmata. The growth of threads is carried out due to simple cell division. Among the homogeneous cells that make up the thread, there are larger thick-walled cells with yellow-brown contents - heterocysts. d Types of blue-green algae: 1 oscillator (general view of the thread); 2 anabens (general view of the thread); 3 gleokaps; 4 Chroococcus (from spore, g heterocyst)

Blue-green algae feed autotrophically or mixotrophically (mixed). As reserve substances are formed: Ø glycoprotein similar to glycogen; Ø volutin (protein); Ø cyanophycin (lipoprotein). Reproduction is predominantly vegetative. In unicellular forms, by cell division, in multicellular forms, by breaking apart threads. Under unfavorable conditions, thick-walled spores are formed from the cells.

Distribution and economic importance. Live in fresh water sea ​​waters, on soil and in soil, on bare rocks, in snow and hot springs. Some planktonic species cause "flowering" of water in reservoirs, others purify water by mineralizing decay products. Soil species of blue-green algae are able to absorb atmospheric nitrogen. Many species enter into symbiosis with fungi, forming lichens. The most common in Belarus are representatives of the genera Anabaena and Nostoc.

4. Division Yellow-green algae (Xanthophyta). The department unites about 2.5 thousand species. Yellow-green algae are represented by unicellular, colonial, multicellular and non-cellular organisms. Spreading. In reservoirs with fresh, less often salty water, where they serve as an important component of plankton, and sometimes benthos, they also live in the soil, on stones. Structure. The walls of their cells are often pectin, less often cellulose. The nucleus in most species is one, less often - there are many nuclei. Chloroplasts, in addition to chlorophyll, contain carotenoids, which give the thallus a yellow-green color. Pyrenoids are rare. Spare products. Oil, sometimes in the form of leukocin and volutin.

Vegetative reproduction is carried out by cell division or parts of the thallus. sexual reproduction known from a few species. The sexual process is predominantly isogamous, occasionally oogamous. Unicellular individuals, as well as oospores and spermatozoa, have two flagella of unequal length: one of them is short, straight, smooth, and the other is long, pinnate. Botridium: 1 thallus; 2 output of zoospores; 3 zoospores

Representatives of the department are species of the genus Vaucheria. Spreading. They live in fresh stagnant and running water, as well as along the banks of drying water bodies, attaching to the soil with the help of rhizoids. Structure. The thallus is branched, multinucleate, but there are no cell partitions between the nuclei. The cytoplasm contains numerous small disc-shaped chloroplasts.

Reproduction. During asexual reproduction, a zoosporangium is formed with one large zoospore equipped with numerous flagella. The zoospore floats in the water for some time, then sheds its flagella and germinates into a new thallus. The sexual process is oogamous. Antheridia and oogonia are unicellular. After a dormant period, the zygote divides by meiosis and germinates, forming a new individual. Vosheria: 1 - 2 - stages of zoosporangium formation; 3 – 4 zoospore exit; 5 area of ​​the zoospore at high magnification; 6 - sperm; 7 fragment of thallus of vosheria; 8 section of the thallus (oogonia, antheridia).

5. Department of diatoms (Diatomophyta). The department unites more than 10 thousand species. These are unicellular organisms, sometimes uniting in colonies. Spreading. Everywhere. They live in salt and fresh water bodies, on moist soil, rocks, tree trunks. Structure. The cell walls are composed of silica (Si. O 2) forming a shell. Valves of the theca, upper - epithecus, lower - hypotheca. There are through holes in the pores, as well as voids in the valves. The sculpture of the valve surface is very diverse and is important in species identification. Inside the cell are the protoplast and vacuoles. The core is one. Chloroplasts are brown in color, since the chlorophyll in them is masked by pigments - carotenoids and diatomine. Spare products are deposited in the form of fatty oils, volutin and leukosin.

Diatoms: A pinnularia: 1, 2 shell (view from the side of the valve and girdle); 3 cage (view from the side of the sash); At the nodule; SH seam; From the sash; P belts; E epithecus; G hypothesis.

Vegetative reproduction is carried out by mitotic division of the protoplast. Then the daughter protoplasts diverge, carrying one of the valves. Subsequently, each of the daughter individuals completes the construction of a new valve. A series of such divisions leads to successive shredding of individuals. In this regard, the sexual process does not lead to a numerical increase in individuals, but to the restoration of their normal size. Vegetative propagation of pinnularia: 1 - epithecus, 2 - hypothecus, 10 - valve, 11 - girdle

The form of the sexual process is very peculiar: the crushed individuals approach one another, discard the theca and become covered with mucus. Each cell divides by meiosis, resulting in the formation of four haploid cells - a tetrad. Two or three cells in each individual die, and the rest merge in pairs. The zygote is called an auxospore. From it grows a new individual of normal size.

The use of diatoms: Ø Thick deposits of rocks - diatomite and tripoli - formed from the valves of dead diatoms. They are used in the production of dynamite, materials for sound and thermal insulation, in grinding metals, and in the manufacture of filters. Ø Participate in the natural processes of water purification. Ø Silicon compounds of diatoms are promising for use in nanotechnology, for obtaining materials with predetermined properties. The most widespread in fresh water bodies of the Republic of Belarus are the species of the genera Pinnularia, Tabellaria and Cyclotella.

6. Division Brown algae (Phaeophyta). The total number of species is about 1.5 thousand. Spreading. Mainly in the seas and oceans around the world. The color of the thallus is from olive yellowish to dark brown. The color is due to a mixture of different pigments: chlorophyll, carotenoids, fucoxanthin (brown).

Structure. The thallus of brown algae is multicellular. Among them there are giants, sometimes reaching 30-50 m. In highly organized species, they form separate cell complexes resembling assimilation, storage, mechanical and conductive tissues. Such differentiation is due to the division of the thallus into sections that perform various functions: rhizoids, the axial (“stem”) part, and phylloids (“leaf” part). Brown algae cells are mononuclear. Numerous chloroplasts more often

Spare products accumulate in the form of laminarin, mannitol and fatty oils. Pectin cellulose cell walls are easily mucilaginous. The growth of the thallus is apical or intercalary. Life expectancy reaches several years. Vegetative reproduction can be carried out by sections of the thallus. Asexual reproduction occurs with the help of numerous two-flagellated zoospores, which are formed in single-celled, occasionally multi-celled zoosporangia, or immobile tetraspores, which are formed in single-celled tetrasporangia. Sexual process. Isogamous, heterogamous and oogamous.

In all brown algae, except for fucus, the change of nuclear phases is well expressed in the life cycle. Meiosis occurs in zoosporangia or tetrasporangia. Zoospores or tetraspores give rise to gametophyte (n), which is bisexual or dioecious. The zygote without a dormant period grows into a sporophyte (2 n). In species of different genera, the nature of the change in nuclear phases is different: in some, the sporophyte and gametophyte do not differ in appearance, in others the sporophyte is more powerful and more durable than the gametophyte.

Brown algae have great importance as fodder, food, medicinal and technical plants. The species of the genus Laminaria (Laminaria) are of the greatest importance as food raw materials. Species of the genus - perennial plants that grow in the Sea of ​​Okhotsk, White, Black, Red and Japan Seas, have a long leaf-shaped thallus of a greenish brown color. The lower part of the thallus is similar in appearance to the petiole of the leaf. With the help of rhizoids, kelp is attached to stones.

7. Division Red algae (Rhodophyta). The total number of species is 4 thousand. Distributed in the seas of tropical and subtropical regions, sometimes in water bodies of temperate climates, and few are freshwater or aerophytic (settle on the soil and bark of trees). Structure. Their thallus looks like bushes, composed of multicellular branching filaments, less often lamellar or leaf-shaped, sometimes up to 2 m long. There are signs of tissue-like differentiation. Growth is diffuse (there are no specialized growth zones) or apical. There are no mobile forms in the life cycle.

The color is diverse due to various pigments: chlorophyll, carotenoids, phycoerythrin, phycocyanin. Chloroplasts are more often in the form of disks without pyrenoids. Spare substances in the form of purple starch. Pectin-cellulose cell walls, together with the intercellular substance, in some species become so mucilaginous that the entire thallus acquires a mucous consistency. In other species, the cell walls are inlaid with lime, which stiffens the thallus.

Vegetative reproduction occurs through the formation of additional shoots that originate from the sole or from creeping branches. The vertical thallus dies off in a certain period and only the basal part of the plant remains, which after some time germinates, forming new shoots. The most primitive crimson reproduce only vegetatively. Various types of spores are used for asexual reproduction. In low-organized purple plants, asexual reproduction is carried out by monospores. Monospores do not have a flagellum and a membrane; after leaving the mother cell, they are capable of amoeboid movement. In some species, monospores are formed in any cell of the thallus and do not differ from vegetative cells until they emerge; in others, monosporangia are formed on branches of limited growth.

Sexual reproduction of red algae is carried out through the formation of complex genital organs. The female genital organ, called karpogon, arises at the ends of the lateral branches. The lower part of it is expanded, and the upper part is narrowed into the so-called trichogyne. At the bottom of the car chasing is an egg. Male organs - antheridia - are collected in groups at the ends of strongly branching filaments. They develop one non-motile sperm, called permacia. With

Meaning. Raw materials for obtaining agar and iodine, they are used as animal feed, eaten. One of the species of freshwater algae is found in Belarus - Batrachospermum (moniliforme).

Marine representatives of red algae are species of the genera Porphyra (Porphyra) and Phicodrys (Phicodrys). Porphyry has a thallus in the ide in a single-layer or two-layer plate, tapering at the bottom into a small stalk. The stalk passes into the sole formed by rhizoids. Plants reach a length of a meter or more. The color of the plates is pink-red.

Representatives of the genus Phycodris have thalli up to 20 cm tall, often with highly branched stems. The plates are single or numerous, leathery, with a short wedge-shaped or heart-shaped base.

8. Division Green algae (Chlorophyta). The total number of species is about 15 thousand. Distributed everywhere, mainly in fresh water, some in the seas and very few in conditions of periodic moisture on the soil, tree trunks, fences, flower pots. Structure. The department includes unicellular and multicellular forms. Organs of locomotion in motile forms are two, rarely four flagella of the same length and shape. Cells are uninuclear, but can also be multinucleated. Chloroplasts in most cases with pyrenoids, varied in shape, size and number per cell. Pigments - chlorophyll, carotenoids. Spare products are starch and fatty oils. Reproduction is vegetative, asexual and sexual. The sexual process is known in almost all species and is very diverse: isogamy, heterogamy, oogamy, somatogamy.

A typical representative of multicellular green algae are species of the genus Spirogyra (Spirogyra). Habitat. Freshwater bodies, rivers, ponds, lakes and peat bogs. Structure. The filamentous thallus consists of one row of cells. Chloroplasts 1 2 per cell are located in the parietal layer of the cytoplasm. They look like spirally twisted ribbons. The nucleus is located in the center of the cell and is immersed in the cytoplasm, the thinnest threads of which stretch to its wall layer. Several vacuoles. Threads grow in length due to cell division.

vegetative reproduction. Parts of the thallus. Sexual process. Conjugation. Two individuals are located in parallel. In their cells, protrusions of the walls arise, growing towards each other. At the junction, the cell walls become mucilaginous, forming a conjugation channel, through which the protoplast from the cell of one individual passes into the cell of another individual. A large spherical zygote with a thick wall is formed. The zygote divides by meiosis. Four haploid cells are formed, three of them die off, and one germinates into a new individual.

9. Department of Chara algae (Charophyta). The department unites no more than 700 species. Structure. These are macroscopic algae, outwardly similar to some higher plants. The height of their thallus is usually 20-30 cm, but can reach 1-2 m. Lateral branches have limited growth, are located in whorls in multicellular nodes. The internodes consist of one long cell, which can be overgrown with a bark of narrow cells. The cell walls are impregnated with lime. Chloroplasts are green and contain chlorophylls and lycopene. The reserve substance is starch. Reproduction. Vegetative reproduction is carried out by means of special nodules on rhizoids or star-shaped clusters of cells on the lower stem nodes, which give rise to a new thallus. There is no asexual reproduction.

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 also red algae). Due to the unique and labile composition of pigments, cyanide is capable of absorbing 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 slightly 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 still waters. (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 grains of cyanophycin.

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. Green color euglena algae 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 euglenoids 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 mobile, 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 different shape, as a rule, 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 species, 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 dinophytes 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, )