Types of algae and characteristics of their varieties. Description of species of multicellular green algae - Abstract

Green, red and brown algae

Currently, more than 30 thousand species of algae are known. Blue-green algae are prokaryotes. Most likely, they are not the ancestors of true algae, however, they may have entered the plant cell as symbionts, turning into chloroplasts. The remaining algae are divided into ten divisions.

Euglenophyta are unicellular (less often colonial) motile flagellates, covered only plasma membrane, under which lies a protein pellicle, which serves as a kind of exoskeleton. Their length ranges from 10 to 500 microns. Chloroplasts (if present) are green or colorless. They reproduce by division; the sexual process was observed only in very few forms. At unfavorable conditions Euglenaceae shed their flagella, forming cysts. About a third of the 900 species are capable of photosynthesis, the rest feed heterotrophically. However, if green euglena is kept in the dark for a long time, the chloroplasts disappear and the algae begins to feed like a saprophyte. If it is then transferred to light, then chlorophyll appears again.

Pyrophyta (Pyrrhophyta) is another group of unicellular marine (less often freshwater) flagellated algae, uniting about 2,100 species from two subdivisions: cryptophyta and dinophyta. Chloroplasts are brown; the cell, as a rule, is enclosed in a cellulose shell, often of a bizarre shape. Most pyrophytes are autotrophs. They reproduce by division and spores, the sexual process is rarely observed. Pyrophytic algae are the cause of red tides; secreted by many of these microorganisms toxic substances cause the death of fish and shellfish. Other pyrophytes are symbionts of radiolarians and coral polyps.

Diatoms (Bacillariophyta) - from 10 to 20 thousand species of microscopic (0.75–1500 microns) solitary or colonial algae, the cells of which are surrounded by a hard silicon shell, consisting of two valves. The walls of the shell have pores through which exchange occurs with external environment. Many diatoms are able to move along the substrate, apparently due to the secretion of mucus. Colonial forms live in mucous tubes that form brown bushes up to 20 cm tall. When reproducing by division, each daughter individual receives one half of the shell, the second half grows again. Due to the fact that the old plate wraps its edges around the growing new one, generations of diatoms become smaller over and over again. Sometimes diatoms form spores; the contents of the cell leave the membrane and increase significantly in size.

Diatoms are the most common group of algae; they live in plankton and benthos, in silt at the bottom of freshwater bodies, on aquatic plants and objects, on damp soil and in moss. Fossil diatoms are known from the Jurassic period; thick deposits of the remains of these organisms form the sedimentary rock diatomite (tripod), used by humans as a filler, insulator or filter.

Among golden algae(Chrysophyta) there are unicellular, colonial, and less often multicellular (bushy, filamentous) freshwater organisms up to 2 cm long. Chloroplasts are golden-yellow or brown in color. Most unicellular golden algae are mobile and have several flagella or pseudopods, some are covered with a shell of scales. They reproduce by dividing cells in two; capable of forming cysts impregnated with silica. Several hundred species, some of them heterotrophs.

Yellow-green algae(Xanthophyta) are often combined with the two previous groups into one division. These are unicellular, colonial and multicellular freshwater forms, free-swimming or attached. The feeding method is mainly phototrophic. Single-celled yellow-green algae usually have two flagella different lengths and are surrounded by a hard pectin shell. They reproduce by fission and spores. More than 500 species have been described.

Majority green algae (Chlorophyta) – microscopic freshwater forms. Some algae (pleurococcus) live on trees, forming a clearly visible green coating on the bark. Filamentous spirogyra form long fibers of mud in streams. There are also colonial forms (for example, Volvox).

Green algae contain chlorophyll, which gives them the appropriate color, as well as other pigments (carotene, xanthophyll), also found in higher plants; most likely, these algae are their immediate ancestors. Multicellular green algae have a filamentous or plate-like shape, some of them are not divided into cells. Motile unicellular algae are equipped with flagella. The cell membrane consists of cellulose.

Green algae reproduce asexually (by parts of the thallus, dividing in half, forming spores) and sexually (for example, in specimens of filamentous algae growing close to each other, the cells are connected by short tubes, through which one of the cells “flows” into another as a gamete). In some green algae, the organs of sexual and asexual reproduction are present on the same specimen; in others, there are sporophytes and gametophytes. Among the 6,000 species (7 classes) of green algae, there are those used by humans for food (for example, ulva), as well as those bred by humans for cleaning Wastewater, as a regenerating element in closed ecosystems (for example, chlorella).

Charovaya algae, or rays (Charophyta) - a division of multicellular algae, sometimes combined with green algae. Cell walls often contain calcium carbonate. Lateral shoots extend from the grayish-green central “stem” 2.5–10 cm high (sometimes up to 1 m). They are fixed in the substrate by rhizoids. Reproduction is sexual or vegetative. About 300 species in fresh water bodies; known from the Devonian.

Red algae, or scarlet grass (Rhodophyta) have a characteristic red color due to the presence of the pigment phycoerythrin. In some forms the color is dark red (almost black), in others it is pinkish. Marine (rarely freshwater) filamentous, leaf-shaped, bushy or encrusting algae with a very complex sexual process. Red algae live mainly in the seas, sometimes at great depths, which is associated with the ability of phycoerythrin to use green and blue rays for photosynthesis, which penetrate deeper than others into the water column (the maximum depth of 285 m at which red algae was found is a record for photosynthetic plants). Some red algae live in fresh water and soil. About 4000 species are divided into two classes. Agar-agar and others are extracted from some scarlet plants. chemical substances, porphyry is used for food. Fossil red algae are found in Cretaceous sediments.

Department brown algae(Phaeophyta), perhaps the most advanced among algae, includes 1500 species (3 classes), most of which are marine organisms. Individual specimens of brown algae can reach a length of 100 m; they form real thickets, for example, in the Sargasso Sea. In some brown algae, for example, kelp, tissue differentiation and the appearance of conductive elements are observed. Multicellular thalluses owe their characteristic brown color (from olive green to dark brown) to the pigment fucoxanthin, which absorbs a large amount of blue rays that penetrate to great depths. The thallus secretes a lot of mucus that fills the internal cavities; this prevents water loss. Rhizoids or the basal disk attach the algae to the ground so tightly that it is extremely difficult to tear it away from the substrate. Many representatives of brown algae have special air bubbles that allow floating forms to hold the thallus on the surface, and attached ones (for example, fucus) to occupy a vertical position in the water column. Unlike green algae, many of which grow along their entire length, brown algae have an apical growth point.

Sexual reproduction of brown algae is associated with the formation of motile flagellated gametes. Their gametophytes are often completely different from the sporophytes that produce spores. Brown algae are used to produce alginic acids, iodine, and feed meal; some species (such as kelp) are eaten. Algae blooms that occur when wastewater is discharged into water bodies big amount nutrients are a serious problem for fish farming.

Ecological groups and habitats

The department of green algae (Chlorophyta) unites 5,700 species. Green algae are one of the most common and diverse groups of algae. Unlike red or brown algae, Most green algae live in freshwater bodies and only some species are in the seas.

Some representatives have adapted to life on land - in the soil or in damp, shaded places with periodic moistening (on tree bark, boulders, fences).

Green algae presented unicellular, multicellular And colonial forms. Some green algae have noncellular thallus. Among multicellular forms, filamentous algae are especially common, which form mud in ponds and rivers.

Evolutionary significance of green algae

Green algae are considered ancestors of land plants. They have the same set of photosynthetic pigments: main photo synthetic pigment - chlorophyll A, auxiliary pigments - chlorophyll b and carotenoids. Cell membrane green algae contains cellulose and pectin, That is characteristic feature not only green algae, but also terrestrial plants; reserve substance- just like terrestrial plants - starch(sometimes fat). Spare substances accumulate green algae not in the cytoplasm (as in representatives of other divisions of algae), but in plastids, which also indicates the relationship between green algae and land plants.

Rice. The structure of green algae. Above is Euglena. From below Chlamydomonas

The bright green color of algae in this department is due to the presence of chlorophylls, but in some species it can be masked by a red pigment - hematochrome, so there are types of green algae that cause red “blooming” of water or snow.

Using the example of individual representatives, two directions of evolution of the thallus of green algae can be traced:

• from a unicellular mononuclear thallus to a noncellular multinucleate one, which is one giant supercell (for example, in caulerpa);
• from a unicellular motile thallus equipped with flagella through immobile unicellular forms to a multicellular filamentous thallus, the development of which leads to the emergence of complex organisms with differentiation of organs and tissues - charophyte algae and land plants.

In general, the evolution of the thallus of green algae can be reflected by the diagram presented in Fig. 1.

Rice. 1. Evolution of the thallus of green algae

The green algae department includes 5 classes:

• Volvoxaceae;
• protococcal;
• ulotrix;
• siphon;
• conjugates, or couplings.

We present brief description the most characteristic representatives of each class.

Volvox class

To the class volvox(Volvocophyceae) are the most primitive representatives of the department of green algae, having a monadic thallus shape, i.e. a unicellular, mobile thallus with 2 (less often 4) identical flagella at the end of the body (for example, representatives of the genus Chlamydomonas). The cells of some Volvoxidae form colonies.

Volvoxaceae are typical planktonic algae that live in shallow, often drying up water bodies. Active cleaners of polluted and wastewater, in which they multiply very quickly, causing green “blooming” of the water.

Typical representatives of Volvoxidae

Genus Chlamydomonas(Chlamydomonas) - from Greek. "Chlamydomonas" is a single organism covered with the ancient Greek loose clothing - the chlamys. The genus includes over 500 species of microscopic algae (length 5-44 microns, width 3-28 microns) - Fig. 2.

Representatives of the genus Chlamydomonas are unicellular, motile algae with flagella (this form of thallus is called monadic). On the outside, the Chlamydomonas cell is covered with a transparent pectin-cellulose cell wall. At the anterior end of the body are located 2 flagella, and in the center of the cell - core and a light-sensitive peephole - stigma, which allows Chlamydomonas to move towards the light. Photosynthesis occurs in a large chloroplast - chromatophore shaped like a bowl. In the center of the chromatophore there is a rather large protein body - pyrenoid, around which starch granules are deposited. Thus, starch in green algae, unlike algae of other divisions, accumulates not in the cytoplasm, but in plastids, which indicates their relationship with green plants. At the base of the flagella there are 2 pulsating vacuoles, which remove excess water from the cell and harmful products exchange.

Rice. 2. Chlamydomonas: 1 - cytoplasm; 2 - flagella; 3 - core; 4 - pulsating vacuole; 5 - photosensitive eye; 6 - chromatophore; 7 photosynthetic membranes; 8 - pyrenoid

In addition to nutrition through photosynthesis, Chlamydomonas is able to absorb and assimilate dissolved in water organic matter. Thanks to mixed type nutrition chlamydomonas is an active sanitary worker of polluted and waste waters, rapidly multiplying in sedimentation tanks. Some types of Chlamydomonas can develop on the surface of snow and ice. They cause red “blooming” of water and snow (for example, Chlamydomonas snow).

Most species of Chlamydomonas are characterized by an isogamous sexual process, but in some species heterogamy and oogamy occur. Chlamydomonas is cultivated in laboratories as an object of research in the fields of genetics, photosynthesis, developmental biology and to determine the toxicity of polluted waters.

Volvox genus(Volvox) has about 20 species of colonial flagellates. A typical representative is Volvox globulus(Volvox globator), the colony of which has the shape of a ball with a diameter of 2-3 mm, consisting of 50-75,000 Chlamydomonas-like cells (Fig. 3). All cells are connected by cytoplasmic bridges, so they act as a single unit. The inside of the ball is filled with mucus.

During vegetative propagation, 8-15 daughter colonies are formed within the mother colony. When they mature, the walls of the ball rupture and the young colonies come out, and the mother colony dies, which is why it is sometimes said that Volvox is the first organism that “invented” inevitable (rather than random) death.

Rice. 3. Colonies of green algae: a) pandorina (round colony); b) gonium (flat colony); c) Volvox

Volvox can also reproduce sexually, and both monoecious and dioecious species are found. In monoecious species, each colony produces both female and male gametes; in dioecious species, each colony is either male or female and produces, respectively, only male or only female gametes.

The Volvox class also includes other colonial flagellates, for example the gonium, which has a flat colony. When moving, it looks like a small flying carpet. Colonies of Eudorina and Pandorina have a round shape. The cells of all these colonial flagellates are immersed in a common mucus wrapper.

Thus, the most primitive representatives of Volvoxidae- These are single-celled, motile organisms with flagella. They have a mixed diet- they can feed both like plants (through photosynthesis) and like animals (by assimilating organic substances from environment), which indicates their origin from ancient flagellates, which combined the characteristics of plants and animals.

From primitive mobile unicellular algae (Chlamydomonas mucus) arise colonial forms(such as Volvox). However, for plants this is a dead-end branch of evolution. Further evolutionary progress is associated with the loss of motility, which is typical for representatives of the protococcal class.

Class protococcal

Protococcal(Protococcophyceae) are unicellular or colonial algae, deprived of mobility in adulthood(only zoospores and gametes are motile). They live in freshwater bodies and soil. There are species that live in the air, for example, on the bark of trees and inside plants growing on water (for example, duckweed). Typical representatives of this class are chlorococcus, chlorella and water net.

Genus Chlorococcus(Chlorococcum) includes unicellular algae, the cells of which are round in shape and lack flagella (see Fig. 4 a). Representatives of the genus Chlorococcus are found on tree bark, fences, flower pots, and accumulate in significant quantities in soils (up to 140 kg per 1 ha). Sometimes they are a component of lichens.

Rice. 4. Protococcal (s. Protococcales): a) chlorococcus (s. Chlorococcum); 6) chlorella (p. Chlorella); 1 - unicellular thallus; 2- formation of zoospores; 3 - zoospore; 4 - young individuals; 5 - formation of autospores

Genus Chlorella(Chlorella) - rice. 4b. - includes unicellular, immobile algae with a diameter of about 15 microns, with one large cup-shaped chloroplast, one nucleus and one pyrenoid (pyrenoids are protein bodies around which carbohydrates are deposited). Chlorella reproduces using immobile, flagellated spores ( aplanospore). There is no sexual process. These are mainly planktonic organisms. They are widespread both in the seas and in freshwater bodies. Some species live in the soil and on tree bark. Chlorella absorbs and uses solar energy much more efficiently than ordinary terrestrial plants (the latter use about 1% of the solar energy falling on them for photosynthesis, and chlorella - more than 10%). It multiplies very quickly, as a result of which it is artificially cultivated, and the resulting biomass, containing about 50% complete proteins and about 20% fats and carbohydrates, is used as a feed additive. In terms of protein and fat content, chlorella is not inferior to soybean. Chlorella biomass also contains vitamins A, B, C, K(and it contains 2 times more vitamin C than lemon juice).

Due to the high rate of photosynthesis, Chlorella intensively absorbs carbon dioxide and releases oxygen, so it is used to purify air in submarines and on spaceships.

Rod water mesh(Hidrodiction) is represented by colonial forms. Water net colonies have the shape of a mesh bag ranging in length from a few centimeters to 5 m (Fig. 5).

From the immobile unicellular forms characteristic of representatives of the protococcal class, in the process of evolution filamentous and then lamellar forms of algae arise, characteristic of representatives of the ulothrix class.

Rice. 5. Water mesh (Hidrodiction reticulum)

Ulothrix class

Ulotrix(Ulotrichophyceae) are multicellular organisms with a filamentous or plate-like structure of the thallus, the cells of which have one nucleus and usually one chloroplast.

The most famous representatives of this class are Ulotrix and Ulva.

Genus Ulothrix(Ulothrix). This is a genus of filamentous algae that lives in fresh water bodies. Their thallus is an unbranched thread of one row of cells (Fig. 6).

Rice. 6. Life cycle of Ulothrix: a) asexual reproduction; 6) sexual reproduction; 1 - main life form; 2 - formation of zoospores; 3 — release of zoospores; 4 - empty cell; 5 - zoospores; 6 - formation of gametes; 7- yield of gametes; 8 - isgamy; 9-10 - zygote; 11 - germination of the zygote; 12 - zoospore

They reproduce mainly asexually (by 4-flagellated zoospores). The sexual process is a classic example of isogamy.

An important lateral evolutionary line in the development of green algae associated with the transition from the filamentous form of the thallus, characteristic of ulothrix, to the lamellar one. It is this form of thallus that is characteristic of representatives of the genus Ulva.

Ulva genus(Ulva) or sea salad. Externally, the ulva resembles a thin, bright green sheet of cellophane. The lamellar thallus is whole, dissected or branched, 30-150 cm high, consists of two layers of cells. Ulvacaceae evolved directly from Ulothrixaceae. In the initial stages of development, the ulva forms a single-row filament, reminiscent of ulotrix, and then a double-row filament, after which a tubular structure is formed. Subsequently, the walls of the tube close and it begins to grow like a two-layer plate. Ulva is characterized by an alternation of isomorphic generations, one of which reproduces asexually, and the other sexually.

Representatives of the Ulva genus can be found in the seas of all climatic zones, but they prefer relatively warm seas temperate zone(they are widespread in such warm seas, like Black or Japanese). Residents of many coastal countries eat ulva, hence its second name - “sea salad”.

Siphon class

Siphon algae(Siphonophyceae) (about 300 species) is one of the oldest groups of green algae, which is a dead-end branch of their evolutionary development.

Siphonaceae differ from other green algae in that their thallus is one giant multinucleate cell. However, externally the thallus is complexly dissected and often imitates a terrestrial plant with a rhizome, adventitious roots and large feathery leaves. An example of such a structure is seaweed caulerpa(Сaulerra) - fig. 7.

Over 90% of siphons are marine organisms that live in tropical seas, covering large areas of the seabed.

One of the most numerous genera of the class Siphonaceae - genus of Cladophora(Cladophora). A typical representative of the genus - Cladophora sauter(C. zauterii) (Fig. 8), which is widespread in freshwater bodies of temperate and cold zones. It has a branching filamentous thallus of large multinucleated cells. The threads form large spherical clusters that float to the surface of the reservoir. Such balls with a diameter of up to 25 cm contain a lot of cellulose. They are used to make paper. The initial stages of development of Cladophora show that it is close not to filamentous algae of the Ulotrix type, but to siphon algae, which have a non-cellular structure, since at first the thallus of Cladophora develops as one giant multinucleated cell, and partitions imitating individual cells appear later.

Fig 7. Caulerpa (Caulerpa sertularioides): a) general form; b) a section of the thallus on a cross section

Rice. 8. Cladophora (p. Cladophora): a) filamentous thallus; b) a cell with a chloroplast; c) cell with zoospores: 1 - reticulate chloroplast

Class conjugates, or couplings

Class conjugates, or couplings(Conjusatophyceae), unites about 4,500 species of multicellular and unicellular algae. The sexual process is conjugation. Flagellar stages of development are absent.

Conjugation is a side branch of the evolution of the sexual process. During conjugation, it is not the nuclei of cells that merge, but their entire protoplasts.

A classic example of conjugation is the reproduction of the freshwater filamentous alga Spirogyra ( Spirogyra).

In heterothallic Spirogyra species, so-called ladder conjugation occurs. Between the cells of the (+) - and (-) - threads, channels are formed through which the protoplasts of the (-) - thread cells pass into the cells of the (+) - thread. Externally, a series of conjugating cells connected by copulation channels resembles a ladder.

In homothallic Spirogyra species, lateral conjugation occurs, in which a conulation channel connects two adjacent cells. Outwardly, such a channel resembles a loop. After the fusion of protoplasts, a diploid zygote is formed.

The main life form of Spirogyra is haploid. Only the zygote is diploid. After a period of rest, the zygote divides twice, forming four haploid cells. Three of them, the smaller ones, degenerate, and the fourth, the largest, germinates and gives rise to a new individual.

When treating with algae, brown algae are most often used. marine species, for example, kelp, ascophylium, ampheltia, fucus, containing greatest number alginic acid. Many doctors insist on the benefits of algae in the treatment of cancer and glandular diseases internal secretion. Algae has also been used in cosmetology.

What is seaweed and how is it beneficial for humans?

Algae are a group of primarily aquatic, single-celled or colonial photosynthetic organisms. Unlike higher plants algae do not have stems, leaves, or roots; they form a protoplast. Contain a large range of useful substances.

The benefits of algae are known first-hand to adherents of alternative medicine. In particular, crushed or micronized algae are used in thalassotherapy: energy-rich substances penetrate the skin from the pulp, revitalizing metabolic processes and counteracting cellulite. In addition, the benefit of algae for humans is that they are rich in antioxidants: P-carotene, vitamins C and E, superoxide dismutase enzyme, microelements and are a source of essential fatty acids.

In total, there are more than 30 thousand species of seaweed - brown, green, red, blue-green and others. Treatment with seaweed is based on the fact that they contain large amounts of iodine, sea gum, plant mucus, chlorophyll, alginic acids, sodium salts, potassium, ammonium, and vitamins. Cosmetics mainly use extracts of brown algae - fucus, kelp, cystoseira. Speaking about the benefits of algae for humans, we must not forget that extracts obtained from individual types of algae differ in their composition and therefore have a targeted effect.

Vitamins in sea and freshwater algae

The content of vitamins A, B1 in freshwater and seaweed is especially high; B2, C, E and D. Algae also contains a lot of fucoxanthin, iodine and sulfoamino acids. The importance of algae in human life is that they are able to stimulate and regenerate skin cells, have a softening and mild bactericidal effect. In others, moisturizing and water-retaining properties are clearly manifested due to the higher content of polysaccharides, organic acids, and mineral salts. Third, due to the active influence of organic iodine, fucosterol, mineral salts and vitamins, they are effective against cellulite, acne, and are beneficial for the care of oily skin, since they provide regulation of fat metabolism and improve blood circulation.

In modern cosmetic practice, seaweed extracts are used in almost all types of skin and hair care products.

Main groups and features of algae, their classification

Speaking about the role of algae in human life, one cannot help but recall modern theory origins of life, which argues that bacteria were at the origins of all life on Earth. Later, some of them evolved, giving life to microorganisms containing chlorophyll. This is how the first algae appeared. Being capable of utilizing solar energy and releasing oxygen molecules, they were able to take part in the formation of the shell of atmospheric oxygen surrounding our planet. Thus, those forms of life on Earth that are familiar to modern man became possible.

Classification of algae in the general development table is difficult. The plant organisms called “seaweeds” are a highly random community of closely related organisms. Based on a number of characteristics, this community is usually divided into several groups. There are 11 main types of algae, and the difference between brown and green algae is more significant than the difference between green algae and higher plants such as grasses.

At the same time, all groups of algae have chlorophyll, a green pigment that is responsible for photosynthesis. Since only one of the groups of algae, green algae, has the same composition and ratio of pigments as higher plants, it is believed that they are the ancestors of forests.

In addition to green algae, there are blue-green, blue, red, and brown algae. But regardless of color, the entire huge number of species known to us, first of all, is divided into two large groups- unicellular and multicellular. Photos of the main types of algae are presented below on this page.

What are the main types of algae?

The main groups of algae include microscopic unicellular and large multicellular.

Microscopic unicellular algae represented by one cell, which is capable of providing all the functions of the body. As can be seen in the photo, these algae have a size of several tens of microns (l micron is a thousandth of a millimeter). Most of them are adapted to a floating lifestyle. In addition, many species have one or more flagella, which make them very mobile.

The second main type of algae is large multicellular- consist of large quantity cells forming the so-called thallus, or thallus - what we perceive as an individual algae. The thallus consists of three parts:

• fixing apparatus - rhizoid, with the help of which the algae holds onto the substrate;
• stalk (legs), varying in length and diameter;
• plates cut into fibers in the form of strands or straps.

The dimensions of the thallus are very different, depending on the type of algae. For example, the thallus of the ulva, or sea lettuce (Ulva lactuca), does not exceed a few centimeters. The peculiarity of these algae is that their extremely thin plate can continue to develop and grow even after being torn off from the substrate. Some kelp specimens reach several meters in length. It is their thallus, clearly divided into three parts, that well illustrates the structure of macroalgae.

The shape of the thallus is also very diverse. There are known marine calcareous deposits consisting of algae of the genus lithothamnion (Lithothamnium calcareum), which during life looks like a small pink coral.

The role and importance of freshwater algae in human life

What types of algae are there, besides seaweed? The sea is not the only habitat for algae colonies. Fresh water ponds, small and big rivers is also their habitat. Algae live wherever there is enough light for photosynthesis.

So, even at great depths, near the bottom, seaweeds called benthic algae live. These are macroalgae that require solid support to establish and develop.

Numerous microscopic diatoms also live here, which are either located on the bottom or live on the thallus of large benthic algae. A huge number of marine microscopic algae form a significant part of the phytoplankton that drifts with the current. Seaweed can be found even in bodies of water with high salinity. Small algae, when multiplying, can color the water, as happens in the Red Sea due to the microscopic algae Thishodesmium, which contains a red pigment.

Freshwater algae are usually presented in fibrous forms and develop on the bottom of reservoirs, on rocks or on the surface of aquatic plants. Freshwater phytoplankton are widely known. These are microscopic unicellular algae that live in literally all layers of fresh water.

Freshwater algae have unexpectedly succeeded in colonizing other areas, such as residential buildings. The main thing for any algae habitat is humidity and light. Algae appear on the walls of houses, they are found even in hot springs with temperatures up to +85 ° C.

Some unicellular algae - mainly zooxanthelles - settle inside animal cells, remaining in stable relationships (symbiosis). Even the corals that make up Coral reefs, cannot exist without symbiosis with algae, which, thanks to their ability to photosynthesize, supply them nutrients necessary for growth.

Laminaria is a brown algae

What types of algae are there, and in what industries are they used? Currently, science knows about 30,000 varieties of algae. Brown algae have found their use in cosmetology - kelp (seaweed), ampheltia and fucus; red algae lithothamnia; blue-green algae - spirulina, chrocus, nastuk; blue algae - spiral algae and green algae ulva (sea lettuce).

Laminaria is a brown algae that was one of the first to be used in cosmetic products. Despite the fact that there are several types of kelp, very different from each other in appearance, they all live only in cold, well-mixed water. The most famous is the sugar kelp (Laminaria Saccharina), which lives off the European coast and owes its name to the sweet taste of the mucus covering it. It grows in bushes, the size of which is directly dependent on the degree of protection of the habitat. It reaches 2-4 meters in length, its stem is cylindrical, turning into a long corrugated plate.

Wide famous name“sea kale” is historically associated with the palmate kelp (Laminaria digitata), living in places protected from the surf at the very upper boundary of the sublittoral zone - the sea shelf zone. Otherwise, kelp is called “witch’s tail.” The thallus of this algae, reaching a length of 3 meters, is beautiful a clear example general plan of the structure of macroalgae. The rhizoids (attachments), palmate, branched, with which the algae attaches to the stones are very clearly visible; stem - long, cylindrical, flexible and smooth; the plate is flat, solid in the lower section, and then cut into straps. This type of algae is especially rich in iodine, since kelp is always under water.

The use of algae of this type has been established in industrial scale. In addition to its nutritional purpose, it has valuable pharmacological properties. This type of kelp is especially known for its stimulating and tonic effect: it improves overall metabolism, is a source of microelements and is widely included in weight loss and anti-cellulite programs.

Numerous studies have shown that seaweed (and other algae) is distinguished by the fact that none of its components is harmful to patients, including those with malignant processes.

Fucus (fucus) is the second most important algae for cosmetics from the brown class (Phaeophycophyta). Grows on rocks in coastal zone and collect it by hand. Beneficial features These algae are due to the fact that they are extremely rich in iodine, vitamins, amino acids, plant hormones and microelements. You can find it on the beaches of the English Channel and along the entire Atlantic coast. For cosmetic purposes, two varieties of fucus are usually used:

Fucus vesiculosus

and Fucus serrafus.

The presence of a large amount of alginic acid determines the natural gelling and thickening ability of extracts of both kelp and fucus. Both algae are rich in organic and inorganic substances, determining their high biological activity. Extracts of kelp and, to a greater extent, bladderwrack (Fucus vesiculosus) contain a complex of substances that stimulate the functioning of β-receptors and block α-receptors of fat cells, providing an effective anti-cellulite effect.

What is it - red, blue and green algae (with photo)

Red algae is a division of algae that lives in seawater.

Lithothamnia (Lithothamnium), like all red algae, they are found on underwater rocks North Sea, English Channel and Atlantic. It was colorfully described in 1963 by the famous submariner Jacques Cousteau. At a depth of a hundred meters, he discovered a red beach - a platform of limestone - lithothamnia. This algae looks like large pieces of pink marble with an uneven surface. Living in the sea, it absorbs and accumulates lime. Its calcium content is up to 33% and magnesium up to 3%, and in addition it has an iron concentration 18,500 times greater than sea ​​water. Lithothamnia is mined mainly in Britain and Japan. It is included in cosmetic products due to its ability to restore the balance of minerals in the body, but it is also popular as a food additive.

In face and especially body care products developed in last years, it is common to use a mixture of fucus algae, kelp and lithothamnia. Rich inorganic compounds Lithothamnia perfectly complements the action of brown algae, providing a comprehensive effect on skin and hair.

Blue algae is a spiral-shaped algae that grows in some lakes in California and Mexico. Thanks to their high protein content, vitamin B12 and P-carotene, they increase skin elasticity and have a remarkable firming effect.

Look how blue algae look in the photo - they differ from other algae in their rich blue-turquoise color.

Green algae are a group of lower plants. Ulva (Ulva lactuca)- sea lettuce is a green algae that grows on rocks. It can only be collected at low tide. Sea salad- a real storehouse of B vitamins and iron, they help strengthen body tissues and improve blood circulation in capillary vessels.

Spirulina is a blue-green seaweed and is used for healing. Spirulina from more than 30,000 species of algae contains the richest set of vitamins, microelements, amino acids, and enzymes. It is rich in chlorophyll, gamma-linoleic acid, polyunsaturated fatty acids and other potentially valuable nutrients such as sulfolipids, glycolipids, phycocyanin, superoxide dismutase, RNase, DNase.

Spirulina differs from other algae in that it contains up to 70% of the most perfect protein; no other representatives of the plant and animal world on Earth contain such an amount.

Spirulina is the richest source of natural P-carotene, a vital antioxidant, and other carotenoids. Carotenoids are used by several organs in our body, including the adrenal glands, reproductive system, pancreas and spleen, skin and retina.

Only spirulina and mother's milk are complete sources of gamma-linoleic acid (GLA), which plays an indispensable role in ensuring the normal functioning of the body, all other sources are extracted oils. GLA helps prevent heart attacks and heart attacks, helps remove excess fluid, improves function nervous system and regulates cell reproduction, has anti-inflammatory properties, supports healthy condition joints, helps treat arthritis. GLA is also recognized as an important nutritional element for the prevention of skin diseases such as psoriasis. Spirulina contains the most perfect protein and all the essential amino acids. Spirulina protein is not required for consumption. heat treatment, while other products containing protein must be boiled or baked (cereals, meat, fish, eggs), as a result of which certain forms of protein partially, and some completely, lose their beneficial qualities.

Spirulina does not contain hard cellulose in its cell walls, unlike other algae, but consists of mucosol saccharides. This allows its protein to be easily digested and assimilated in the body. Protein absorption is 85-95%.

Lesson type - combined

Methods: partially search, problem presentation, reproductive, explanatory and illustrative.

Target:

Students’ awareness of the significance of all the issues discussed, the ability to build their relationships with nature and society based on respect for life, for all living things as a unique and invaluable part of the biosphere;

Tasks:

Educational: show the multiplicity of factors acting on organisms in nature, the relativity of the concept of “harmful and beneficial factors”, the diversity of life on planet Earth and options for adaptation of living beings to the entire range of environmental conditions.

Educational: develop communication skills, the ability to independently obtain knowledge and stimulate one’s cognitive activity; ability to analyze information, highlight the main thing in the material being studied.

Educational:

Formation of an ecological culture based on recognition of the value of life in all its manifestations and the need for a responsible, careful attitude to the environment.

Forming an understanding of the value of a healthy and safe lifestyle

Personal:

nurturing Russian civic identity: patriotism, love and respect for the Fatherland, a sense of pride in one’s Motherland;

Formation of a responsible attitude towards learning;

3) Formation of a holistic worldview, corresponding modern level development of science and social practice.

Cognitive: ability to work with various sources of information, transform it from one form to another, compare and analyze information, draw conclusions, prepare messages and presentations.

Regulatory: the ability to organize independent completion of tasks, evaluate the correctness of work, and reflect on one’s activities.

Communicative: Formation of communicative competence in communication and cooperation with peers, seniors and juniors in the process of educational, socially useful, educational and research, creative and other types of activities.

Planned results

Subject: know the concepts of “habitat”, “ecology”, “ environmental factors“their influence on living organisms, “connections between living and nonliving”;. Be able to define the concept “ biotic factors"; characterize biotic factors, give examples.

Personal: make judgments, search and select information; analyze connections, compare, find an answer to a problematic question

Metasubject:.

The ability to independently plan ways to achieve goals, including alternative ones, to consciously choose the most effective ways solving educational and cognitive problems.

Formation of semantic reading skills.

Form of organization educational activities - individual, group

Teaching methods: visual-illustrative, explanatory-illustrative, partially search-based, independent work with additional literature and a textbook, with COR.

Techniques: analysis, synthesis, inference, translation of information from one type to another, generalization.

Multicellular algae. The diversity and importance of algae

Objectives: to continue to develop an understanding of algae as a special group of plant organisms; introduce various multicellular algae, their habitat and structural and reproductive features; give an idea of ​​the role of algae in nature, their use in science, technology, human economy, and measures to protect algae; continue to develop the ability to work with a microscope and the skill of performing biological drawings.

Equipment and materials: tables: “Single-celled algae”, “Multicellular algae”, “Brown and red algae”, flowering plant Elodea from an aquarium, herbariums of various multicellular algae, live algae from an aquarium; some items made from seaweed: seaweed salad, seaweed supplements, iodine, agar-agar, etc.

Key words and concepts: filamentous algae (ulotrix, cladophora, spirogyra), brown algae (kelp, fucus, sargassum), red algae (phyllophora, porphyra, ptilote, radimenia); thallus (thallus), rhizoids, sporangium, nucleus with nucleus, vacuole, chromatophore; asexual reproduction, sexual reproduction, conjugation; zoospores, motile gametes, spores, zygote; phytoplankton

During the classes

Updating knowledge

Work at the board

Two students are called to the board. One of them needs to depict the structure of the unicellular green alga Chlamydomonas, and the other - Chlorella and indicate the main organelles of this algae. It takes about 2-3 minutes to complete the task. Afterwards, students respond orally according to the diagram drawn.

Next, three more students come to the board. One of them depicts a diagram of the asexual reproduction of Chlamydomonas, the other - the sexual reproduction of Chlamydomonas, and the third - the reproduction of Chlorella. Afterwards, students respond orally according to the diagrams they have drawn.

Learning new material

Teacher's story with elements of conversation

In the last lesson we studied unicellular algae. Today let's move on to multicellular ones. Let's start with filamentous algae.

Why do you think they got this name? (Answers from students.)

These algae resemble long threads in appearance.

Among filamentous algae, the most common in our latitudes is spirogyra. This is a multicellular green algae, the cells of which are arranged in one row. Growth occurs through division of the entire body. The plant leads unattached Lifestyle. Its threads move freely in water under the influence of various currents. This is a common inhabitant of our ponds and rivers with gentle currents. You, often swimming in a pond or river, have probably discovered accumulations of green, slippery to the touch mud. These are the filaments of Spirogyra.

(The teacher shows an image of this algae on the tables and, if possible, in live or dried form.)

Spirogyra cells have an elongated shape. On the outside they are covered with a layer mucus.

Why do you think this algae received such a name? (Students express their guesses.)

Chromatophores in the cells of this algae they have a special structure. They are long, elongated and located in the cytoplasm along the cell wall, as if encircling it in a spiral. Hence the name. In the center of the cell there is a large nucleus with nucleolus. Takes up quite a lot of space vacuole

Remember in what ways unicellular green algae can reproduce. (Sexually or asexually.)

Spirogyra is also characterized by both sexual and asexual reproduction. At asexual method, the filaments of spirogyra break, the cells of each part begin to divide, giving rise to new young organisms.

When does asexual reproduction of Chlamydomonas occur? (Under favorable conditions.)

Spirogyra also reproduces asexually under favorable conditions, most often in summer.

Sexual The reproduction of Spirogyra is somewhat different from the identical Chlamydomonas. During sexual reproduction of Spirogyra, two filaments are located parallel to each other. Then they get closer and become enveloped in mucus. Cells located closest to each other form special outgrowths that connect, creating a channel through which the contents of one cell flow into another. Thus it happens fertilization and is formed zygote. The zygote is covered with a thick membrane and can long time to be at rest. After a certain period of dormancy, the zygote germinates and gives rise to a new organism. This method of sexual reproduction is called conjugation.

On stones and snags lying at the bottom of shallow rivers, you can often find another filamentous algae - ulotrix. Clumps of ulotrix look like bright green silky threads. The body of this plant also consists of one row of cells, but the cells are not elongated, like those of Spirogyra, but shorter. Ulotrix grows due to the division of cells located only at the top. In addition, this algae leads attached Lifestyle. It is glued to the substrate with a special colorless cell. In the cytoplasm of each algae cell one can detect a nucleus and a chromatophore in the form of an open ring.

Asexual Reproduction of this alga occurs through zoospores.

Remember what a zoospore is.

Zoospores- motile cells with flagella, with the help of which asexual reproduction occurs. Zoospores float freely, and then attach to the substrate, divide and give rise to a new organism.

What method of reproduction is most often found in algae under unfavorable conditions? (They reproduce sexually.)

During sexual reproduction of ulotrix, numerous motile gametes with flagella are formed in some algae cells. Gametes from different individuals fuse in pairs and form a zygote. The zygote is also covered with a thick membrane and can remain dormant for a long time. As soon as conditions favorable for algae life are created, the zygote divides into 4 spore cells. The spores sink to the bottom and, having attached themselves to the substrate, begin to divide, giving rise to a new individual.

Quite often, the multicellular green alga Cladophora is found in fresh and salt water bodies. It is also a filamentous algae, but more highly organized than Spirogyra and Ulotrix. Cladophora threads branch. Young cladophorans lead an attached lifestyle, but subsequently often break off and go free swimming. Interesting feature of this plant is the presence in every cell large number cores. Such phenomena never occur in the cells of higher plants.

Independent work of students with the textbook

Using the text of the textbook (textbook by I.N. Ponomareva § 39; textbook by V.V. Pasechnik § 12), as well as personal experience, indicate the importance of algae in nature and human life.

(About 3-5 minutes are allotted to complete this task, after which 2-3 students’ notebooks are taken for checking, and another 3-4 answer orally. The teacher accompanies the students’ oral answers by demonstrating tables and, if possible, some seaweed products: salad from seaweed, food supplements with algae, iodine, agar-agar, etc.)

The role of algae in nature

The process of photosynthesis transforms the energy of the sun into energy available to other organisms and releases the oxygen necessary for their respiration.

Food for many marine animals ( sea ​​urchins, fish, etc.) and sea waterfowl.

Shelter for fish and many other animals.

Enrichment of water with oxygen during photosynthesis.

Some types of unicellular algae are pioneer plants: when they fall on infertile substrates, they participate in soil formation.

Some types of algae are part of complex organisms (lichens).

The role of algae in human life and activity

Food products for humans (kelp, ulva).

Use as an additive to livestock feed.

Manufacture of fertilizers.

Preparation of agar-agar used in the food industry and microbiology (red algae).

Use in chemical industry(obtaining iodine, potassium salts, alcohol, acetic acid, etc.).

Biological treatment of industrial and waste water (junk domonada, chlorella).

Receipt medicines and biologically active food additives.

Harm caused by algae to humans and their activities

Excessive proliferation in irrigation canals makes it difficult to supply water.

Excessive reproduction in fish ponds makes seasonal fishing difficult.

Excessive growth of algae leads to difficulties in navigation.

Creative tasks.

To draw a picture underwater world, on which various sections of algae will be present: red, brown, green, etc.

Compose a fairy tale about life in the underwater kingdom, where the main characters will be algae.

In the books of which writers are there descriptions of the underwater world?

An activity for students interested in biology. Find in the specialized literature the names and descriptions of algae grown in fresh and salt aquariums. What algae do they belong to?

Seaweed. Educational film

Travel across Africa. Algae forest. Educational film.

MarineseaweedKelp

Seaweed and Green Technologies from Olmix - EN

Marineseaweed

Resources:

I.N. Ponomareva, O.A. Kornilov, V.S. Kuchmenko Biology: 6th grade: textbook for students of general education institutions

Serebryakova T.I.., Elenevsky A. G., Gulenkova M. A. et al. Biology. Plants, Bacteria, Fungi, Lichens. Trial textbook for grades 6-7 of secondary school

N.V. Preobrazhenskaya Biology workbook for the textbook by V. Pasechnik “Biology 6th grade. Bacteria, fungi, plants"

Which have no stem, root or foliage. Preferential algae habitat are seas and fresh water bodies.

Green algae department.

Green algae there are unicellular And multicellular and contain chlorophyll. Green algae reproduce sexually and asexually. Green algae live in bodies of water (fresh and salty), in soil, on rocks and stones, and on the bark of trees. The Green Algae department has about 20,000 species and is divided into five classes:

1) Class protococcal- unicellular and multicellular flagellate forms.

2) Volvox class- the simplest unicellular algae that have flagella and are capable of organizing colonies.

3) Heat class- have a structure similar to that of horsetails.

4) Ulothrix class- have a filamentous or lamellar thallus.

5) Siphon class- a class of algae that are similar in appearance to other algae, but consist of a single cell with many nuclei. The size of siphon algae reaches 1 meter.

Department of red algae (purple algae).

Purple fish are found in warm seas at great depths. This department has about 4,000 species. Thallus red algae has a dissected structure; they are attached to the substrate using soles or rhizoid. Red algae plastids contain chlorophylls, carotenoids And phycobilins.

Another feature of red algae is that they reproduce using complex sexual process. Red algae spores and gametes are motionless because they do not have flagella. The fertilization process occurs passively through the transfer of male gametes to the female genitals.

Department of brown algae.

Brown algae- these are multicellular organisms that have a yellowish-brown color due to the concentration of carotene in the surface layers of cells. There are about 1.5 thousand species of brown algae, which have the most various shapes: bush-shaped, lamellar, spherical, crust-shaped, filamentous.

Due to the content of gas bubbles in the thalli of brown algae, most of them are able to maintain a vertical position. Thallus cells have differentiated functions: extinction and photosynthetic. Brown algae do not have a complete conducting system, but in the center of the thallus there are tissues that transport assimilation products. Nutrient minerals are absorbed by the entire surface of the thallus.

Different types of algae reproduce by all types of reproduction:

Sporov;

Sexual (isogamous, monogamous, heterogamous);

Vegetative (occurs when some parts of the thallus are accidentally divided).

The importance of algae for the biosphere.

Algae are the starting point of most food chains various bodies of water, oceans and seas. Algae also saturate the atmosphere with oxygen.

Seaweed actively are used to obtain various products: polysaccharides agar-agar and carrageenan, used in cooking and cosmetics, are extracted from red algae; alginic acids, also used in the food and cosmetics industries, are extracted from brown algae.