Length of green algae. Green algae: list of main species and description

GREEN ALGAE (Chlorophycota, Chlorophyta), algae department. Unicellular, multicellular (filamentous and lamellar) and siphonal (non-cellular) organisms. Most are painted various shades green color due to the predominance of the green pigment chlorophyll (types a and b) over other pigments (carotenoids). The size of many green algae is microscopic, but there are species (for example, large codium, Codium magnum), reaching a width of 25 cm and a length of more than 8 m. The cells are mononuclear and multinuclear, the main component of the cell wall is cellulose. Chloroplasts are not associated with membranes endoplasmic reticulum or kernels; thylakoids in stacks of 2-6 or more. Flagella of equal or unequal length (most often 2) can be covered with delicate "felt" or scales; in the zone of their exit from the cell there is a nine-pointed stellate body. A light-sensitive eye (stigma) is found in many motile algae, as well as in gametes and zoospores of immobile forms; as a photoreceptor, it mediates phototaxis. The reserve substance of cells is starch; It is formed on the surface of special protein bodies (pyrenoids), usually located inside the chloroplast. Green algae have all the main types of vegetative, asexual and sexual reproduction. They number 13-20 thousand species, over 500 genera. live in fresh water oceans (90%), as well as in the seas, the deepest sea green algae (found at a depth of 84 m) belong to the genus Codium. Some green algae live in soil, on snow, trees, rocks, various buildings etc. Many green algae are components of lichens and animal symbionts.

An established classification system for green algae still does not exist. The most specific units of classification are orders, but they are grouped into classes in various systems differently. The greatest controversy is still caused by the position in the system of two groups - charophytes and conjugates, or conjugates, which in modern systems are either included in the department of green algae, or isolated into independent departments. Among the green algae are representatives of Volvox, Desmidean, Zignem, Ulothrix algae and many other orders. The mass development of microscopic green algae causes "blooming" of water, snow, tree bark, etc. The ability of many green algae to absorb organic substances dissolved in water with the entire surface of the body (along with the autotrophic type of nutrition) accelerates the processes of natural self-purification of polluted reservoirs, in which they multiply very quickly. Due to this property, they are used as bioindicators of polluted waters. Green algae serve as food in fishery reservoirs. Some species (from the genera Ulva, Codium, etc.) are eaten. Research is underway on the industrial cultivation of unicellular green algae (chlorella, scenedesmus, etc.) as a source of food and feed and for air regeneration in closed systems ( spaceships, submarines).

Lit .: South R., Wittik A. Fundamentals of algology. M., 1990.

Green algae (lat. Chlorophyta) is a group of lower plants. In modern systematics, this group has the rank of a division that includes unicellular and colonial planktonic algae, unicellular and multicellular forms of benthic algae. All morphological types of the thallus are found here, except for rhizopodial unicellular and large multicellular forms with a complex structure. Many filamentous green algae are attached to the substrate only in the early stages of development, then they become free-living, forming mats or balls. Multicellular green algae [ Electronic resource] - Access mode: http://www.town33.ru/statrasvod.html

All green algae are distinguished primarily by the pure green color of their thalli, similar to the color of higher plants and caused by the predominance of chlorophyll over other pigments. The chromatophores of cells contain the pigments chlorophyll, carotene and xanthophyll, with the green pigment quantitatively predominating over the yellow ones. Encyclopedia for children. T. 2. Biology. - 5th ed., revised. And additional / Chapter. Ed. M.D. Aksenova. - M.: Avanta +, 2001. - S. 305-308

Among green macrophytes, there are various forms: colonial, filamentous in the form of highly branched bushes, lamellar, siphon and rather complex chara algae, outwardly resembling higher plants - hornwort or horsetail. The thallus of charophytes consists of branching shoots ("stems") and whorled branches of limited growth ("leaves"). The locations of the "leaves" are called nodes, and the sections of the stem between them are called internodes.

The stock product of green algae is starch.

Green algae are inhabitants of fresh and salt waters.

The most common species found in Russia and living mainly in the sea belong to the genera: Khara - Chara Vaill; Ulva -- Ulva L; Caulerpa -- Caulerpa Lamour; Codium -- Codium Stackh; Cladophora - Cladophora Kutz.; Ulvaria -- Ulvaria Rupr and others.

Characteristics of the most common genera of marine green algae

Rod Chara -- Chara Vaill:

Representatives of this genus are very different from the rest in that their filamentous multicellular thalli have a complex morphological organization. On the main shoots growing at the top (“stems”), at some distance from each other there are whorls of identical short lateral jointed shoots (“leaves”) with limited growth. The locations of the whorls are called nodes, and the sections of the thallus between them are called internodes.

In appearance, many of the charophytes are very reminiscent of horsetails, although this resemblance, of course, is purely external. Each internode on their thallus is one multinucleated, giant (up to several centimeters long), often covered with a bark, a cell incapable of division. And the nodes consist of several small mononuclear cells assembled into a disk, in the process of their division forming the lateral branches of the “stem” and the whorl of “leaves”. Shoots of characeae are attached to the bottom with the help of numerous thin rhizoids. These algae reach very large sizes - from 20-30 cm to 1-2 m.

Characeae do not have asexual reproduction, the sexual process is oogamy. Organs that produce gametes - multicellular oogonia and antheridia - are formed on the segments of the thallus, in the nodes. In the oogonium up to 1 mm in size, one egg develops, in the antheridium (its diameter is about 0.5 mm) - many male germ cells. In most species of characeae, oogonia and antheridia develop on the same plant, but there are also dioecious species.

About 300 species of charophytes are known. They are common in fresh water, especially with hard lime water, where they often form continuous thickets at the bottom. Some species are also found in sea bays.

In most species, the thalli are heavily encrusted with lime, which makes them brittle and break easily. Annuals.

The genus contains 117 species. There are 15 species in Russia. The most common type is

Rod Ulva -- Ulva:

The algae thallus of the genus Ulva is a bright green two-layer plate with corrugated edges, about 10-12 cm in size, attached to the substrate with a base narrowed into a short petiole. Ulva cells are mononuclear with a parietal chromatophore and a large central vacuole. The most common method of vegetative propagation of Ulva is the germination of base cells with the formation of young plants. Unlike the algae listed above, life cycle where the haploid stage predominates, the Ulva has an alternation of generations: a diploid sporophyte and a haploid gametophyte. The nuclei of sporophyte cells contain a double set of chromosomes, and during reduction division, haploid zoospores are formed. Germinating, they form haploid plants - gametophytes, capable of forming gametes. When the gametes merge, a zygote is formed containing a diploid nucleus and germinating into a sporophyte without a dormant period. Ulva is characterized by an isomorphic change of generations - its sporophyte and gametophyte outwardly look exactly the same.

Ulva is found in the seas of all climatic zones although it prefers warm waters. It is found in almost all seas of Russia. For example, in the shallow waters of the Black Sea, this is one of the most mass species algae. Many Ulva species tolerate desalination; they are often found in river mouths.

Ulva: A - appearance of the thallus; B - cross section of the thallus

The genus contains approximately 30 species. In Russia there are 3 types. The most common types:

Genus Caulerpa -- Caulerpa Lamour:

The genus caulerpa includes about 60 species of seaweeds, the creeping parts of the thallus that are spread on the ground look like branching cylinders, reaching a length of several tens of centimeters. At certain intervals, abundantly branching rhizoids extend down from them, fixing the plant in the ground, and up - flat, leaf-like vertical shoots in which chloroplasts are concentrated.

Caulerpa thallus, despite its large size, does not have a cellular structure - it completely lacks transverse partitions, and formally it is one giant cell. This structure of the thallus is called siphon. Inside the thallus of the caulerpa is a central vacuole surrounded by a layer of cytoplasm containing numerous nuclei and chloroplasts. Various parts of the thallus grow at their tops, where the cytoplasm accumulates. The central cavity in all parts of the thallus is crossed by cylindrical skeletal cords - cellulose beams, which give the body of the algae mechanical strength.

Caulerpa: A - appearance of the thallus; B - section of the thallus with cellulose beams

Caulerpa easily reproduces vegetatively: when the older parts of the thallus die off, some sections of it with vertical shoots become independent plants.

Species of this genus live mainly in tropical seas, and only a few enter subtropical latitudes, for example, the germinating caulerpa (Caulerpa prolifera), common in the Mediterranean Sea. Caulerpa prefers shallow waters with calm water, for example, lagoons protected from the action of constant surf by coral reefs, and settles both on various hard substrates - stones, reefs, rocks, and on sandy and silty ground. Green algae [Electronic resource] - Access mode: http://bio.1september.ru/articlef.php?ID=200201003

Genus Codium -- Codium Stackh:

Thallus various shapes- compressed-cylindrical, cord-like or cushion-shaped, but not jointed and not calcified. Branching is dichotomous or polychotomous. It is attached to the substrate by rhizoids.

The inner tissue is a loose plexus of threads, the outer layer is formed by dark green swollen close ends of the branches. The filaments that make up the thallus are not separated by septa and are giant cells with many nuclei.

Marine plants found only in warm waters.

The genus contains 50 species. In Russia there are 3 types. The most common type:

Genus Ulvaria -- Ulvaria Rupr:

Thallus is lamellar, single-layered, on a cylindrical stalk, in initial stage tubular development. There are sometimes microscopic outgrowths on the surface of the plate. Attaches with a small sole.

Characterized by the presence of brown pigment.

Annuals.

Found exclusively in the seas.

In Russia there are 2 types. The most common type is

Genus Enteromorpha -- Enteromorpha Link:

The thallus is tubular, sometimes strongly compressed, simple or branched, single-layer, with a cavity or with its remains due to adhesion of the walls of the thallus.

Annuals.

It grows on stones, algae, shells in all seas of Russia and in fresh water.

The genus contains about 40 species. In Russia, there are about 10 species. The most common type is

Enteromorpha intestines - Enteromorpha intestinalis

Genus Bryopsis -- Bryopsis Lamour:

The thallus is quite large, unicellular, in the form of a strongly branched tubular bush, having a more or less distinct main axis and pinnatiously extending lateral branches from it. Branching in one plane or along the entire axis. Lateral branches can in turn branch like a main axis, resembling a feather. The thallus is attached with the help of rhizoidal outgrowths, which extend from the base of the thallus and from the main branches, and at the same time spread along the main axis.

It can reproduce by separate branches that break off from the mother plant.

Annuals.

grows on rocky soils, on algae and shells in warm seas.

The genus contains 30 species. In Russia there are 5 types. The most common type:

Bryopsis pinnate -- Bryopsis plumosa

Rod Ulothrix (Ulothrix):

It lives in sea and fresh waters, forming green mud on underwater objects. Filamentous type of thallus differentiation. The chloroplast is parietal in the form of a girdle, closed or open, with several pyrenoids. The core is one, but it is not visible without painting.

Reproduces mainly vegetatively by four-flagellated zoospores. The sexual process is isogamy (gametes of the same size). Some species are characterized by heterothallism. Biflagellate gametes are formed in cells in the same way as zoospores. They come out and merge. The zygote, after a dormant period, germinates into the codiolum stage, where its nucleus passes. After some time, meiosis occurs, after which there may be more mitoses. As a result, 4-8 zoospores are formed, germinating into new ulotrix filaments. All stages except the zygote are haploid.

The most widespread is the girdled Ulothrix (Ulothrix zonata). Belyakova G.A. Botany: in 4 volumes. Vol. 2. Algae and mushrooms: a textbook for students. higher textbook manager - M: Publishing Center "Academy", 2006. - S. 221.

Tull

In green algae, the following types of thallus differentiation are known:

1. monadic (for example, Chlamydomonas, Volvox, Gonium, Dictyosphaerium");
2. palmelloid, or tetrasporal ( Tetraspora, Sphaerocystis);
3. coccoid ( Chlorella, Hydrodiction);
4. sarcinoid ( Chlorosarcinopsis);
5. trichal, or filamentous ( Ulothrix, Spirogyra);
6. heterotrichous, or multifilamentous ( Chara, Stigeoclonium);
7. pseudoparenchymal ( Protoderma);
8. parenchymal ( Ulva, Ulvaria);
9. siphonal ( Caulerpa, Bryopsis);
10. siphonocladal ( Cladophora, Dictyospheria).

Cell structure

flagellar apparatus

Monad cells and stages of green algae are isocont, rarely heterocont. The number of flagella per cell can be different - 1, 2, 4, 8, 16 or more (up to 120). In edogoniaceae and some briopsids, numerous flagella are collected in the form of a corolla at the anterior end of the cell; such cells are called stephanocont. characteristic feature the transition zone of the flagella of green algae is the presence of a stellate body in it. Flagella of green algae do not have mastigonemes (unlike heterokonts), but may have fine hairs or scales.

cell wall

In the classes Chlorophyceous and Prasinophyceous, there are algae in which the cells are naked and lack a cell wall. In mesostigmata and many prasinophycia, organic scales are deposited on top of the plasmalemma. They are found in motile cells of a number of ulvae and charophytes. The presence of organic scales on motile cells is apparently a primitive feature. The appearance of theca in Prasinophycia and then in Chlorophycia is considered to be more progressive. The theca in Chlorophycia is composed of glycoproteins rich in hydroxyproline and associated with various oligosaccharides.

Ecology and significance

Green algae are widely distributed throughout the world. Most of them can be found in fresh water bodies (representatives of charophytes and chlorophytes), but there are many brackish and marine forms (most representatives of the class of ulvophytes). They are found in water bodies of different trophicity (from dystrophic to eutrophic) and with different content of organic substances (from xeno- to polysaprobic), hydrogen ions (from alkaline to acidic), at various temperatures(thermo-, meso- and cryophilic species). Among them are planktonic, periphytonic and benthic forms. In the group of marine picoplankton representatives, the prasinoficial algae Ostreococcus tauri considered the smallest eukaryotic free-living cell. There are green algae that have adapted to life in soil and terrestrial habitats. They can be found on the bark of trees, rocks, various buildings, on the soil surface and in the air column. Among them, in these habitats, representatives of the genera Trentepohlia and Trebuxia. The mass development of microscopic green algae causes a "bloom" of water, soil, snow, tree bark, etc. So, Chlamydomonas nivalis can be found high in the mountains on red-tinted snow. In this species, chlorophyll is masked by carotenoid pigments.

peculiar environmental group are endolithophytic algae associated with a calcareous substrate. First, it is drilling algae. For example, algae from the genus Gomontia they drill barley and toothless shells, they are introduced into the calcareous substrate in fresh water bodies. They make the lime substrate loose, easily amenable to various effects of chemical and physical factors. Secondly, a number of algae in fresh and marine water bodies are able to convert calcium salts dissolved in water into insoluble ones and deposit them on their thalli. A number of tropical green algae, in particular Halimeda, deposits calcium carbonate in the thallus. They take an active part in the construction of reefs. Giant deposits of remains Halimeda, sometimes reaching 50 m in height, are found in continental shelf waters associated with the Great Barrier Reef in Australia and other regions, at a depth of 12 to 100 m.

Green algae (class trebuksofitsievye), entering into a symbiotic relationship with fungi, are part of lichens. About 85% of lichens contain unicellular and filamentous green algae as a phytobiont, 10% of lichens contain cyanobacterial partners, and 4% (or more) contain cyanobacteria and green algae. As endosymbionts, they exist in the cells of protozoa, hydras, sponges, and some flatworms. Even the chloroplasts of individual siphon algae, for example Codium, become symbionts for nudibranch molluscs. These animals feed on algae, the chloroplasts of which remain viable in the cells of the respiratory cavity, and in the light they photosynthesize very efficiently. A number of green algae develop on the fur of mammals.

A number of green algae are of economic importance. They are used as indicator organisms in the monitoring system of aquatic ecosystems. For example, the Defense Agency environment The United States recommends the use of indicator organisms in freshwater tests, such as Selenastrum capricornutum and Scenedesmus subspicatus. Green algae are used for purification and post-treatment of polluted waters, as well as forage in fishery reservoirs. Some species are used by the population of a number of countries for food. For these purposes, for example, in Japan, they are specially cultivated Ulva and Enteromorpha. Certain types of green algae are used as producers of physiologically active substances. So, species of the genus Haematococcus cultivated in industrial scale to obtain the carotenoid astaxanthin, Botryococcus- to obtain lipids. At the same time, with the "blooming" of the water of one of the lakes in Taiwan, caused by Botryococcus associated with the death of fish.

Types of childbirth Chlorella and Chlamydomonas- model objects for studying photosynthesis in plant cells. Giant multinucleated thalli Acetabularia, multicellular thalli Chara and unicellular representatives Dunaliella and Chlamydomonas in genetic engineering they are used as objects for transformation.

Phylogeny

The presence of chloroplasts, in which the shell consists of two membranes, collected in stacks of thylakoids, chlorophylls a and b, carotenoids (lutein, β-carotene) and starch, which is deposited in the chloroplast, are the main synapomorphic features that distinguish green algae and their sister group of streptophytes from other eukaryotic lines. Monophyletic origin of all green plants supports phylogenetic analysis based on comparison of 18S rRNA sequences in various lines eukaryotes. This analysis showed the division of all green plants into two major groups - Chlorophyta s. str. Sluiman 1985 and Streptophyta Bremer 1985. Within the monophyletic group Chlorophyta s. str. there are four independent evolutionary lines - classes Chlorophyceae, Trebouxiophyceae, Ulvophyceae and Prasinophyceae. The last class is a polyphyletic group that split off at the base Chlorophyta. Within the Streptophyta group, two lines are distinguished - higher plants and charophytes. Notice the position Mesostigma viride, which was previously attributed to prasinoficial algae. To date, there are two points of view on its position: 1) it stood out at an early stage in the streptophyte branch; 2) the place of its departure is associated with the division of all green plants into two main groups.

Having a green color due to the presence of chlorophyll. About 500 genera and 20 thousand species of green algae are known, distributed mainly in fresh water bodies and on moist land areas. For example, chlamydomonas, chlorella, ulotrix, volvox. Occasionally, representatives of this department are found in the seas, sometimes in the soil and on tree trunks.

This group includes unicellular and colonial plankton algae, as well as multicellular species that make up benthos. In the composition of plankton, they can provoke the "bloom" of water. In this case, green algae are being fought.

Tull. A characteristic feature of these plant organisms is the green color of the thalli, similar to that of higher plants, due to the predominance of chlorophyll over other pigments. The sizes vary from a few microns to several meters. In the representatives of the group, except for unicellular, all morphological types of thalli (thalli) are found: parenchymal, monadic, coccoid, palmelloid, trichal, sarcinoid, etc.

Cell structure. The internal and external structure of algae cells is diverse. Cells may be cell walled or naked. Basic structural element cell wall - cellulose. Some species of algae are characterized by the presence of a flagellar apparatus, consisting of different number flagella.

Each cell of green algae contains chloroplasts. They differ in size and shape. They can be mesh, ring-shaped, spiral-twisted, etc. The structure of algal chloroplasts is similar to higher plants. Due to this, algae are capable of autotrophic nutrition. Among the plants of this group there are also mixotrophs that receive nutrients not only in the process of photosynthesis, but also absorb organic substances dissolved in water. Throughout the chloroplast, DNA molecules are distributed in the form of small spherical formations.

Some representatives of green algae have a red or orange color due to the accumulation of carotenoid pigments and their derivatives, hematochrome, outside the chloroplast. A number of siphon algae are characterized by the presence of transparent amyloplasts containing starch. Lipids can also accumulate in the cytoplasm and stroma of chloroplasts. Important element cells of many species of algae - a light-sensitive eye, so that the cell is able to move to a lighted place.

Reproduction. It features both asexual and sexual reproduction. asexual reproduction occurs through zoospores. At vegetative propagation individuals are divided or disintegrate into separate parts. The sexual path involves the fusion of gametes to form zygospores or oospores.

Green algae are widely distributed throughout the world. Many species are of economic importance, in particular as indicators of pollution of fresh water bodies, as well as for purification and post-treatment. Wastewater. Green algae are the most common group aquatic plants in aquariums. In fish farms, algae are used as fish food. Some species are used by humans for food. In industry, carotenoids are obtained from some species, lipids from others. Representatives of green algae are the objects of study of genetic engineering.

Green algae is one of the most numerous divisions of algae. They are widespread on our planet and include up to 20,000 species. First of all, they are united by the color of the main pigment, otherwise they are very different. Let's find out which algae are green. What types and classes do they belong to? What traits do they have?

The main signs of algae

Algae is what we usually call all plants that live in water. They really love moisture, but this is far from their only sign. They represent an extensive group of organisms of different origin, which are united by some common features:

• the presence of chlorophyll;
• photoautotrophy;
• lack of division of the body into functional parts;
• lack of an integument;
• lack of a distinct conducting system.

Algae live in humid areas. They can live in the soil, on the surface of the earth, on the bark of plants, in the seas, oceans, swamps and other bodies of water. They are important participants in ecological and biological processes. It is with algae that the marine and some terrestrial food chains begin.

By type of nutrition, they are photoautotrophs. This means that they are able to produce organic substances from inorganic and do this using the energy of light and carbon dioxide. Through their activities, they produce about half of the total amount of oxygen that is produced by plants.

Their body is called a thallus, or thallus. Unlike the body of higher plants, it is not divided into different organs and tissues. And although outwardly algae may have visible stems, roots, leaves - this is just a hoax. All their parts consist of cells of the same type that perform the same functions.

What are algae?

More than 100 thousand species of algae are known. They are divided into sections: brown, diatoms, red, green algae. They are all eukaryotes because their cells contain a nucleus. However, science also knows blue-green algae, which are prokaryotic organisms. For their ability to photosynthesize, they were once classified as plants, but now they are considered bacteria and are found under the names "cyan" or "cyanobacteria".

Green algae belong to the plant kingdom and include organisms of a wide variety of shapes and sizes. Most often they live in fresh water bodies and humid regions, but they are found in both salty and brackish waters.

There are several classes of green algae:

• ulfocium;
• bryopside;
• chlorophytium;
• trebuksievye;
• prazine;

Their sizes range from a few micrometers to two meters. Characteristic green color gives them high content chlorophyll. In addition to it, algae contain the pigment lutein, neoxanthin. Due to the presence of carotenoids, some of them have a reddish or orange hue.

Appearance and structure

The internal and external structure of green algae is very diverse. They can be mononuclear and multinuclear, consist of a different number of cells, or even have a non-cellular thallus. Some of them do not attach to surfaces and live freely in aquatic environment. Others are firmly fixed on objects and various substrates.

Among green algae, there are those that consist of only one cell. It is impossible to see them without a microscope, because their size is extremely small. But in summer and spring, one can observe how, from their active reproduction, the water in puddles, ponds and swamps turns green.

Multicellular green algae are more like ordinary higher plants. Their body can consist of many threads, form a kind of stems and leaves. An intermediate variant between multicellular and unicellular is represented by colonial. They are a group of interconnected cells or organisms. Despite the association, they can retain their independence and react differently to stimuli. In the event of a rupture of the colony, they quietly continue to exist and are able to form new groups by dividing their cells.

Relationships with other organisms

Green algae can exist in almost all wet places. They are found in soil, on the shady side of rocks, and even in snow. high mountains and the Arctic zone of the Earth. If a glass of water is left for several days in a sunny place, then they will appear there.

Algae easily enter into symbiotic relationships with other organisms. They coexist perfectly with molluscs, sponges, protozoa, hydras and flatworms. With mushrooms, their collaboration turned out to be so productive that it even received separate title- lichen. Once such an association was considered an integral plant organism, for example, moss. About 80 algae are involved in the formation of lichens, of which representatives of the genus Trebuxia are most often found.

The genus Chlamydomonas unites more than 500 species of green algae that live mainly in fresh water. These are unicellular organisms of pear-shaped or oval shape. They are equipped with special light-sensitive eyes and a pair of flagella, rotational movements which help chlamydomonas to move in the water to more lit places.

Most of them live in small, well-heated water bodies and can contribute to their flowering. The most unusual representative is snow chlamydomonas, living at low temperatures. It lives in snow and ice, and thanks to the pigment astaxanthin, it colors them in a pinkish hue.

Spirogyra

Spirogyra is the most common multicellular algae. It is painted bright green and consists of many thin threads of various lengths. Spirogyra is found in both fresh and salt waters. It appears in slowly flowing and stagnant ponds, in aquariums that are not properly cared for. Together with other algae, it forms a sticky mud that feels like cotton wool.

Volvox

Volvox are mobile colonial algae that live in stagnant fresh water. During the period of mass reproduction, they contribute to the flowering of water, coloring it green. About 20 types of Volvox are known.

The Volvox colony looks like a green ball with a maximum size of 3 mm. Each of these balls includes from 10 to 200 thousand microscopic cells, which are connected by threads from protoplasm. Like chlamydomonas, they have flagella for movement inside the reservoir. Cells are not identical and are divided according to their specificity. Some are vegetative, others are generative and take part in sexual reproduction.

Ulva

The Ulva genus is a marine green algae that lives within the subtropical and temperate zones. the globe. They are multicellular organisms with a branched lamellar thallus ranging in size from 30 centimeters to 1.5 meters. At the base of the body of the algae are filamentous formations, rhizoids, with which they cling to various surfaces.

Ulva needs sunshine, therefore, lives at shallow depths. It serves as food for marine animals and is great place for laying eggs by fish. Some types of ulva are eaten by people. In cooking, she is better known as sea ​​salad.

Nitella

Algae of the genus Nitella are widespread throughout the Northern Hemisphere. They live in the fresh waters of Asia, Europe and North America. Outwardly, algae are difficult to distinguish from higher plants. Their thallus consists of thin stems with small nodes, from which 5-7 narrow and thin leaves extend in a circle.

They love well-lit places and warm temperature water - within 20-28 degrees. The plant is quite unpretentious and is able to make the water clearer, which is why it is often planted in aquariums. In natural reservoirs, the overgrown nitella becomes a refuge for small fish and a place for their spawning.

Caulerpa

Briopsidic algae of the genus Caulerpa live mainly in warm tropical and subtropical seas. Outwardly, they are very diverse and visually divided into leaves, stems and roots. They can be branched or resemble mushrooms in appearance. Despite the apparent complexity, their internal structure is very simple. The thallus of algae consists of only one cell, which contains many nuclei. In some species, it can grow strongly, reaching 2-3 meters in size.

Caulerpa is motionless and always attaches to some surface. Often she settles at the bottom of reservoirs, clinging to silt or sand. It also grows on underwater rocks and coral reefs. Due to their size, algae of this genus are the largest single-celled organisms in the world. Due to their unusual appearance, they are popular, so they are often grown in aquariums. In the countries of Southeast and East Asia some species of caulerp are eaten.