A variety of protozoan plants that laid the foundation for the development of representatives of the flora is the department - green algae. Their emerald color is due to the predominance of chlorophyll over other pigments. Most often they are distributed in fresh water, but can also exist in the seas.

They also include green plants that we see in aquariums, such as threadworm. This species reproduces so rapidly in strong light that it is difficult to control it.

Besides aquatic environment their habitat is swampy soils, tree trunks, walls of houses. The presence of moisture required condition for their prosperous life and reproduction.

The department of green algae includes approximately 13 thousand species that differ in structure and appearance having common characteristics. Meanwhile, among the diversity of this species, algae can be distinguished not only green, they are transparent, brown, as well as any shade of the spectrum. According to their structure, they are divided into:

• unicellular;
• multicellular;
• siphon;
• lamellar;
• colonial;
• filamentous.

The forms of representatives of this class are diverse. From fractions of microns, their size can reach tens of meters.

Structure

Outwardly, green algae resemble their complex counterparts, while they are deprived of the structure of tissues and organs familiar to plants, they do not have roots, stems and leaves. At the same time, all physiological processes - nutrition, growth, reproduction proceed as in complex representatives of the flora.

Some species - unicellular and colonial, unlike amoebic ones, are equipped with a dense shell - a wall of cellulose or pectin, resembling glass, two or more flagella, which make it possible to move in the aquatic environment, screwing along its own axis into the thickness of the surrounding liquid. Those algae that consist of several cells form loose aggregates. This combination creates various forms, similar to thin threads, trees, balls, stars and others.

The structure of cells can differ in the number of nuclei - one or more. However, all have a cytoplasm with plastoid vacuoles. The first contain chlorophyll, the second - a liquid with nutrients, gases and mineral salts. The cytoplasm also contains a red light-sensitive eye.

Life cycles

Green algae reproduce in several ways. This is a direct cell division, a vegetative method and a spore one.

The life cycle of the plant depends on the propagation method. For clarity, consider an example, with the direct division of the mother cell into two daughter cells, the process can continue indefinitely. Thus, the plant becomes practically immortal, dying only from an accident.

In sexually reproducing gametes have a variety of structure, size and shape, as well as the similarity or difference between female and male cells. Some gametes in the period before fertilization can lead a passive lifestyle.

In the third type of reproduction, one half of the shell is inherited from the mother cell and the second is formed independently.

Role in nature and use

Algae can be observed in any natural and artificial reservoir. They are found in nature in almost every puddle, quietly existing in fresh and salt water. Other types populate the soil (colorless) or strengthen on its surface, feeding on chloroform - green.

Some settle on snow-covered mountain peaks, in the arctic deserts. They are also capable of living in cold ocean water. The phenomenon of "red snow" is the result of the presence of algae in it. Meanwhile, this species is also diverse and can have, in addition to red, green, yellow and brown hues.

As you can see, the area of ​​distribution of these primitive plants is quite wide, but for life they require certain conditions - this is the presence of moisture, light, temperature, gases and mineral salts.

Algae play an important role in nature. They serve as food for the inhabitants underwater world. Great importance has their ability to absorb carbon dioxide and release oxygen, which is necessary for the respiration of representatives of the aquatic fauna. In addition, they are natural cleansing systems.

For scientific purposes, they are used in biology, growing as a nutrient medium on which they reproduce. different kinds organic crops.

A person uses these plants as feed for farm animals, receives iodine, agar-agar from them, and also uses them in cooking. Dishes with seaweed are especially common in the countries of the East. Ulva, chlorella, umi, which contain a large number of minerals, iodine, vitamins A, B, C, K, PP therefore have a beneficial effect on health.

Application in medicine

Since they have antibacterial and anti-inflammatory properties, they found wide application in therapy various diseases. Their influence on the activity of T-lymphocytes helps to strengthen the immune system.

Anti-inflammatory and regenerating properties make it widely used for cosmetic purposes.

Classification

Previously, scientists classified algae as a single type of primitive tolloma, which consisted of fungi and other lower plants. In a later classification, they began to be divided by color. However, this factor is not fundamental, therefore, the method of reproduction and formation of colonies, as well as the type of cell wall, chloroplasts, reserve substances and other signs are taken into account.

Green algae are the largest group of living microorganisms, the tissues of which are practically not subject to any differentiation, therefore they are still classified as lower plants, which include, in addition to the designated species, bacteria, lichens and fungi.

Green algae are considered lower organisms along with bacteria and fungi.

Species Chlorophyta

The Chlorophyta division includes a huge list of green algae, which, according to preliminary estimates of research scientists, number in the thousands of plant species (their approximate number varies in an extremely wide range from 13 to 20 thousand).

That is why it is impossible to determine the exact number of their species today and main reason This situation lies in the difficulty of differentiating these plant organisms.

Department representatives

Almost all types of thallus can be found among green algae. Representatives of this department are not only the simplest unicellular and multicellular colonial planktonic algae, unable to resist the flow of water masses, but also unicellular and multicellular phytobenthos, the distinguishing feature of which lies in its habitat - ocean, sea or river soil.

Not all members of the green algae class are green.

The only exceptions are unicellular and multicellular plants of the rhizopodial type with their complex structure and excellent thallus.

Nevertheless, it is the department in question that is officially recognized as the most extensive in all flora reservoirs. Despite the name, far not all representatives have a thallus (body) of a green hue. For example, such a representative of the species as trentepolia has cells of orange-red pigment, due to the accumulation of carotene and all kinds of derivatives of this useful substance.

Filamentous plants are also found among these algae, the main difference of which is not in the predominant pigment of a different color, but in the habitat. If at the beginning of your life path they can be attributed to benthos, since filamentous algae tend to attach to the water body, then over time they start up free swimming, actually becoming planktonic algae, forming numerous balls and mats from their colonies.

Classes of green algae

Due to the complexity of identifying the thalli of plant organisms that are part of the green algae department, as well as their more than impressive number, scientists have not yet been able to create any unified register or detailed classifier. However, currently there are five main classes of green algae, which include:

• ulvophyceous;
• brypsoides;
• chlorophytium;
• trebuksievye;
• prazine.

Representatives of the class Ulvophyceae live mainly in sea ​​water

The Ulvophyceae class includes at least a thousand species of plants, predominantly found in the marine environment. It is noteworthy that this class includes not only filamentous and lamellar algae, but also some types of lichens. As for its marine representatives, which are the absolute majority, their characteristic feature is the presence of calcareous microparticles. In turn, this The class is divided into two orders:

1. Ulotrix, most often living in water bodies with fresh water, attaching to any objects and forming numerous colonies in the form of undersized bushes. Asexual plants of this order tend to reproduce in two ways, the first of which involves the division of one thread into several, while the second is characterized by the formation of zoospores in mother cells with their further release and distribution.
2. Ulva, which are found in all the seas of the world, preferring primarily salty reservoirs with warm water. A distinctive characteristic of these algae with a bright green thallus is the presence of a leg for attaching to the sea soil, as well as a variety of structures (the thallus of plants can be either tubular or bag-shaped or lamellar).

Class Bryopsidophyceae has about five hundred species of plant organisms with non-cellular thallus. All these algae belong to a single order with the same name Briopsidaceae, which prevails in fresh waters. In turn, this order is divided into three main genera: bryopsis, codium and caulerpa, which differ from each other not only in structure, but also in habitat.

class of unicellular algae Chlorophyceae has about 2500 species that belong to a single order of volvox. At the same time, it is divided into two genera: Chlamydomonas (at least 500 species) and Volvox (about 2 thousand). The first genus, which is also asexual, has the property of reproducing through cell division. At the same time, Volvox, which is rightfully considered the most highly organized representative of this group, is able to organize huge colonies numbering thousands of living organisms.

Chlamydomonas belongs to the class of green algae.

Another class Trebouxiophyceae consists of 170 species of unicellular organisms, predominantly coccoid in shape, which can live both on earthen soil and on the bottom of fresh lakes and rivers.

This class is classified in two orders into chlorella and trebuxian algae, and if the first type is immobile balls, for which natural environment habitats are water bodies, the second is part of the lichens found on tree bark or leading a free lifestyle.

Structure, cycles and purpose

In spite of great amount species of green algae, which amaze with their diversity, scientists were able to identify several general characteristics these living plant organisms.

Structural features and life cycle

Plastid cells, which are part of algae, most often have a cup-shaped shape, and, in addition to the classic green, they include yellow (lutein) and red-orange pigments of the carotene group (zeaxanthin, violaxanthin, neoxanthin, etc.). The chloroplast itself has a special internal inclusion - the pyrenoid, which is penetrated by 2-6 membrane-limited compartments called thylakoids.

At the same time, green algal plastids have double membranes, which is characteristic of red algae and other more developed plant organisms.

The life cycle of green algae depends on their habitat

The cells of most species of the group under consideration have contractile vacuoles, which are single-membrane organelles with cell sap in the middle part. It is also possible that there is a stigma - an intracellular organoid with bright red spots, due to which the body is able to move towards or away from the light source.

Flagella, almost identical in structure, often have different length, although there may be two or more. These isoconts do not have lateral hairs (mastigonemes), however, this does not mean at all that algal flagella are completely absent of any hairs or scales.

A factor in the increased growth of algae is an increase in the temperature of their habitat

The life cycle of these plant organisms directly depends on their species and habitat. Altogether, scientists distinguish three main cycles of their development:

• Haplobiont (zygotic reduction), which is characterized by the release of a gamete through the pore of the mother cell and its further fusion with another gamete through the tube. Further, transformation into a zygospore occurs, in which, after a dormant period, 4 zoospores are formed, followed by the formation of a polyhedron in each of them.
• Haplo-diplobiont (sporic reduction), in which the gametes released from the mother cell merge in water, forming not two, as in the haplobiotic cycle, but four-flagellated zygotes, freely floating in the water masses. The next stage involves attaching the zygote to any solid surface and covering it with a dense layer, after which the formation of a codiolum occurs, leaving for a long rest. The re-activation of these club-like cells usually becomes possible with the onset of favorable conditions. As a result, from 4 to 16 spores are released from the codiolum, forming new threads, and everything repeats again.
• Diplobiont (gametic reduction), characterized by the division of a large nucleus, which is formed during the settling of a planozygote and the formation of a separate filamentous thallus.

The most favorable factor for the development of algae is an increase in temperature, so it is not at all surprising that their rapid growth can be observed in warm waters and during the onset of spring and summer seasons.

Role for humanity and the environment

It is extremely difficult to underestimate the importance of green algae in the biosphere, because by absorbing the carbon dioxide emitted by animals and humans, they give off oxygen, without which life on the planet becomes impossible by definition. Thanks to this unique feature, plants are widely used not only on earth, but also in space flights, as well as on submarines. In addition, they are often used as a kind of indicator of the level of pollution of water, air and other important ecosystems.

A huge amount of all kinds of vitamins, minerals and trace elements that are part of these plant organisms allows you to actively use certain types of them in cooking (people from countries especially love this component). South-East Asia), as well as in cosmetology. The most effective masks, creams, serums and wrapping clays usually contain extracts of these amazing plants.

In addition, seaweeds play a huge role in pharmacology, because their useful qualities and properties are actively used to make a variety of medicines for indoor and outdoor use.

GREEN ALGAE (Chlorophycota, Chlorophyta), algae department. Unicellular, multicellular (filamentous and lamellar) and siphonal (non-cellular) organisms. Most are painted various shades Green colour due to the predominance of the green pigment chlorophyll (types a and b) over other pigments (carotenoids). Many size green algae 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. They live in fresh water bodies (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 the 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 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 the entire surface of the body dissolved in water organic matter(along with the autotrophic type of nutrition) accelerates the processes of natural self-purification of polluted water bodies, 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.

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. 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. There are also mixotrophs among the plants of this group, which 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. During vegetative reproduction, individuals divide or break up into separate parts. The sexual path involves the fusion of gametes to form zygospores or oospores.

Green algae are widely distributed throughout the globe. Many types have 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

The species richest division of algae are green algae, numbering up to 20 thousand species. They are distinguished by the pure green color of the thalli, which is associated with the predominance of chlorophyll over all other pigments. Along with chlorophyll, which is identical to the chlorophyll of higher plants, the chloroplast also contains carotenes and xanthophylls. Sometimes the green color of algae can be masked by a red pigment (hematochrome). Spare nutrient the same as in higher plants - starch. Green algae are typical eukaryotes; cells may contain one or more nuclei. The shape of the cell is clearly fixed by dense cellulose and pectin membranes.

The morphological structure of representatives of this department is very diverse. Among green algae there are unicellular, colonial, coenobial (unlike a colony in a coenobium, the number of cells is always constant) and multicellular species. All types of vegetative body structure inherent in algae as a whole, except for amoeboid and tissue structures, can be found in the study of green algae. Green algae vary greatly in size: along with microscopic forms, there are species whose thallus length reaches several tens of centimeters and even a meter.

Green algae have all types of asexual and sexual reproduction. They often reproduce vegetatively.

The department of green algae is a very systematically fractional group. Until now, there is no consensus regarding the position in the system of the department of various classes. The criteria by which the department is divided into taxonomic ranks have not been established, which is associated with the extraordinary diversity of green algae. Most scientists divide the department into classes, depending on the structure of the vegetative body: volvox, chlorococcal (or protococcal), ulotrix, siphon, conjugates.

Volvox algae have a monadic structure of the thallus; most Volvox are solitary species, but some species form coenobia. The cell has a dense cellulose membrane, sometimes pectin, one cup-shaped chloroplast, in which pigments are concentrated. A light-sensitive eye is associated with the chloroplast - stigma, there is one or two pulsating vacuoles. The reserve nutrient is starch. Volvox algae are predominantly autotrophic, but cases of a mixed type of nutrition, and sometimes heterotrophic, are known. These algae usually reproduce vegetatively - by cell division, asexual and sexual reproduction is also found.

Among the volvox algae, only a small number of species can live in water bodies with high salinity. The bulk of them are inhabitants of stagnant, well-heated reservoirs with fresh water. Their usual habitats are ditches, puddles, and ponds. They feel very well, actively moving in the water column with the help of flagella, in reservoirs. treatment facilities rich in organic matter. Due to the ability to heterotrophic nutrition, they play an important role in the processes of self-purification of water in wastewater bodies, are food base for other aquatic life. With sufficient illumination, appropriate temperature and the presence of biogenic elements, they develop especially quickly, causing green and red "blooming" of water.

In the reservoirs of the region, such species as chlamydomonas spherical, Reinhard's chlamydomonas, marine carteria, lenticular phacotus, pectoral gonium, blackberry pandorina, graceful evdorina, spherical volvox, golden yellow volvox live in the reservoirs of the region.

Volvox algae originated from primary primitive amoeboid ancestors, their evolution followed the path of complicating the sexual process and the structure of the thallus.

Cells of representatives of the class of chlorococcal algae in a vegetative state are completely immobile. These are unicellular or coenobial species. The most primitive representatives of this class inherited the ocellus and flagella from their ancestors, but the latter are motionless and are called pseudocilia. Most species are microscopic and have the most different shape cells - spherical, fusiform, sickle-shaped. Cell membranes are cellulose, sometimes equipped with setae and spines. They reproduce vegetatively or asexually. The sexual process is known in a few species and is rarely observed.

The most famous in the algoflora of the region are common chlorella, four-tailed scenedesmus, beautiful dictyospherium, square crucigenia, perforated pediastrum and others.

Chlorococcal algae, leading their pedigree from Volvox, in turn, in the process of evolution gave rise to the next class - ulotrix. In the class of chlorococcal algae, the beginnings of new structures appeared for the first time in the organization of the vegetative body of algae - filamentous and lamellar.

Most representatives of the ulotrix class have a multicellular filamentous thallus, although lamellar species are also found. The thread consists of one or two layers of cells; it serves as the basis for all more complexly organized thalli. The latter are formed as a result of cell division in different axes. The lamellar thallus is single-layer, two-layer, may have a cavity inside. Ulothrix cells have one nucleus, one chloroplast, which occupies a parietal position in the form of a plate. Ulotriksovye can lead both an attached lifestyle and lie freely at the bottom of reservoirs. Reproduction - sexual, asexual, and also vegetative - by pieces of thallus. Pleurococcus vulgaris, trentepolia shady, ulothrix zona, enteromorpha enteromorpha, stygeoclonium slender are found in the region from the class of ulothrixes in the region.

Siphon algae have a so-called non-cellular structure. The thallus of these algae is one large cell, sometimes of very complex outlines. This group of algae is quite ancient, and at present its representatives are found mainly in tropical seas. Our flora is characterized by species in which the vegetative body is divided into multinuclear sections, or segments. These are weak cladophora, twisted cladophora, egagropile cladophora, hieroglyphic rhizoclonium, ringed spheroplea, graceful chetophora, Kützing's microtumnion, curly praziola. The chloroplast in such segments has a mesh structure. Sometimes these algae are even isolated as an independent class of siphonocladium ex. They usually reproduce sexually and asexually. V life cycle there is an alternation of generations - gametophyte and sporophyte.

Conjugates, or couplings, are predominantly microscopic algae, unicellular or filamentous. Unicellular linkages have bizarre outlines, distinguishable, of course, only under a microscope, and clusters of threads are visible to the naked eye. The algae of this department got their name from the method of reproduction: conjugation is a temporary connection of two individuals, which exchange parts of the nuclear apparatus and cytoplasm. In nature, conjugation occurs at a fairly high water temperature (not lower than 25 ° C), on a bright sunny day. Two cells or two filaments approach each other, and their contents merge, most often with the help of a bridge connecting either cells of different filaments or adjacent cells of the same filament. As a result of the fusion, a zygote is formed, which, after a dormant period, gives rise to a new plant. The cells of the conjugates in appearance are distinguished by exceptional elegance, delicacy of the ornaments covering their shells.

Conjugates can also reproduce vegetatively: in unicellular organisms, this is cell division, and in filamentous ones, the breakdown of filaments into separate cells, from which new filaments subsequently grow.

Conjugates are quite numerous in the reservoirs of the region. These are spirogyra, muzhotia, signema, Kützing's closterium, graceful closterium, needle closterium, lined closterium, truncated mycrasterium, Maltese cross mikrasteria, grape-like cosmarium, low cosmarium, shortened cosmarium, strange staurastrum, moon-shaped staurastrum, xanthidium ray.

Bright green, silky to the touch clusters of spirogyra are called "mermaid hair"

Green algae - the largest and most specific group among algae, characterized by a huge variety of species included here. Their evolution went from primitive flagellar species to multicellular ones, although the latter did not reach high level differentiation. Green algae in the process of development gave rise to charophytes - this is one branch of their evolution, the other branch led to the emergence of higher plants.