aquatic plants are divided into higher (Cormobionta) and lower (Thallobionta). The latter includes all types of algae. They are one of the oldest representatives of the flora. Their main feature- spore reproduction, and the peculiarity lies in the ability to adapt to different conditions. There are types of algae that can live in any water: salty, fresh, dirty, clean. But for aquarists they become a big problem, especially if they grow wildly.
There are types of algae that can live in any water: salty, fresh, dirty, clean. Main characteristics
Depending on the variety of algae, some are attached to underwater surfaces, while others live freely in the water. Crops may only contain green pigment, but there are species with different pigments. They color the algae pink, blue, purple, red and almost black.
The biological processes occurring in the aquarium are the basis for the independent appearance of algae. They are introduced when fish feed live food or newly acquired aquatic plants.
Some algae look like a fluffy tuft, others resemble a spread carpet, and others resemble a slimy coating. There are flat, thallous, branching, filamentous cultures. Unlike higher plants, they do not have roots, stems or leaves. Their shape, structure and sizes are varied. There are species that can only be seen under a microscope. IN natural environment plants reach several meters in length.
Classification of algae
Each species has its own requirements for the environment in which they grow - the temperature of the liquid, the intensity and duration of lighting. An important factor is chemical composition water.
An imbalance of algae in the aquarium indicates the occurrence of unfavorable conditions. An excessive increase in them in the tank worsens the quality of the water, which adversely affects the health of the inhabitants of the aquarium. An algae outbreak can be caused by:
- Unregulated aquarium lighting mode. This is a disadvantage daylight hours or its excess.
- Excess organic matter in the container. They can be in the form of leftover food, dead aquarium plants, or fish waste.
- Organic decomposition. The appearance of nitrites and ammonia in the aquarium.
Having identified which factor causes the appearance of crops, it is necessary to eliminate it or minimize it as much as possible.
An imbalance of algae in the aquarium indicates the occurrence of unfavorable conditions in it.
Algae are divided into 12 types. An aquarium is most often characterized by the presence of three main types of crops.
Their presence is predictable where water, light and nutrients are available.
Green group
This is the most widespread and most diverse group of plants in structure and form, which has about 7 thousand species. They come in noncellular, unicellular and multicellular forms. Algae form colonies on glass or soil.
Their peculiarity is that almost all crops appear as a result of excess lighting. They are green in color, despite containing yellow pigment in addition to green chlorophyll. Algae color the liquid green or brick green.
There are sea and freshwater species. Names of algae that are found in the aquarium:
The main reason for the appearance of most species green algae- excessive lighting, so when the biological balance is restored, this problem can quickly disappear.
Diatoms (brown) plants
If the liquid in the container has to be changed frequently because it quickly becomes cloudy, - got wound up in her kelp . It not only spoils the interior of the aquarium, but also causes inconvenience to its inhabitants. These are single-celled microscopic organisms that multiply quickly and create a slimy coating on the leaves of aquarium plants and tank glass. They live alone or in colonies in the form of a ribbon, thread, chain, film, bush.
At the initial stage of the appearance of plaque in the container, it is easily removed, but in advanced cases it becomes multi-layered, and it can be difficult to get rid of it. Brown plants will not harm aquarium animals, but they are dangerous for aquarium plants. Plaque on crops interferes with photosynthesis, which leads to their death.
Reproduction of diatoms is carried out by division. Plant cells have a hard shell with a silica composition. Their sizes are minimum 0.75 microns, maximum 1500 microns. This culture is easily distinguished by its shell in the form of dots, chambers, strokes, ribs located with geometric regularity.
Naviculas live almost everywhere, appearing in spring and autumn.
There are about 25 thousand varieties of brown crops in nature. Most often found in containers are:
- Navicula. This genus has about 1 thousand species of algae. The containers are started in spring and autumn. The method of reproduction is cell division. Cells vary in shape, shell structure and structure. They serve as food for the inhabitants of the aquarium, and they themselves feed phototrophically.
- Pinnularia. Early autumn and summer is the time of appearance for this genus. As a result of cell division, each cell receives one leaflet from the mother cell. Single cells are rarely connected into ribbons. About 80 species of these algae are known.
- Cymbella. The genus consists of single free-living cells, which are sometimes attached to the substrate by a mucous stalk. In addition, they may be enclosed in gelatinous tubes.
Brown algae develops in tanks where the water is not changed promptly or the lighting is poor. Their distribution is influenced by the dense population of the aquarium, a large number of organics, clogged filter.
Red or “purple”
Red algae, or scarlet algae, are a small species of crops, the vast majority are multicellular, numbering up to 200 varieties. All scarlets are divided into 2 classes, each of which contains 6 orders. They settle on the stems and ends of leaves of aquarium plants, stones, grow quickly and multiply intensively.
The reason for the appearance of this type of plant is an excess of organic matter in the water, improperly installed lighting or overcrowding in the container. These crops pose a danger to its inhabitants, so they must be destroyed in a timely manner.
Purple fish, depending on the combination of pigments, change color from bright red to bluish-green and yellow, and freshwater ones are usually green, blue or brownish-black. A feature of plants is their complex development cycle. As a rule, these crops grow attached to other plants, stones, and tanks. Colonies of crops can be found in the form of mucous coatings.
Red algae, or scarlet algae, are a small species of crops, the vast majority are multicellular, numbering up to 200 varieties.
For aquarists, there are two types of disaster:
- Black beard. At the initial stage, they appear as single black bushes that are concentrated in one place, or they can be scattered throughout the tank. If you don’t start fighting it, then with the help of rhizoids the culture clings to the substrate, as if growing into it. Very often, these algae appear after purchasing new aquarium plants, or if the rules for caring for the tank are neglected.
- Vietnamese. Such aquarium algae belong to filamentous species. Based on their appearance, aquarists call them bush, beard or brush. Plants have different colors and reproduce very quickly by spores. The culture prefers to be located on the tips of aquarium plants or tank decor.
The appearance of any type of algae indicates problems with the microclimate in the tank. It takes months to fight some plants, while others can be quickly and easily gotten rid of.
The underwater world has always attracted people with its brightness, unprecedented beauty, diversity and unknown secrets. Amazing animals, amazing plants different sizes- all these unusual organisms do not leave anyone indifferent. Besides visible to the eye major representatives floras, there are also tiny ones, visible only under a microscope, but this does not lose their importance and significance in the total biomass of the ocean. This unicellular algae. If we take the total output produced underwater plants, That most It is they who produce, these tiny and amazing creatures.
Algae: general characteristics
In general, algae are a subkingdom of lower plants. They belong to this group for the reason that their body is not differentiated into organs, but is represented by a continuous (sometimes dissected) thallus or thallus. Instead of a root system, they have devices for attachment to the substrate in the form of rhizoids.
This group of organisms is very numerous, diverse in shape and structure, lifestyle and habitats. The following divisions of this family are distinguished:
- red;
- brown;
- green;
- golden;
- diatoms;
- cryptophytes;
- yellow-green;
- euglena;
- dinophytes.
Each of these departments may include unicellular algae and representatives with a multicellular thallus. Also found following forms organisms:
- colonial;
- filamentous;
- free-swimming;
- attached and others.
Let us study in more detail the structure, vital activity and reproduction of representatives of precisely unicellular organisms belonging to different classes of algae. Let's evaluate their role in nature and human life.
Features of the structure of unicellular algae
What are the specific features that allow these tiny organisms to exist? Firstly, although they have only one cell, it performs all the vital functions of the whole organism:
- height;
- development;
- nutrition;
- breath;
- reproduction;
- movement;
- selection.
Also by this single-celled organisms inherent function of irritability.
In his internal structure single-celled algae do not have any features that could surprise an interested researcher. All the same structures and organelles as in the cells of more highly developed organisms. The cell membrane has the ability to absorb surrounding moisture, so the body can submerge under water. This allows algae to spread more widely not only in the seas, oceans and other bodies of water, but also on land.
All representatives except blue-green algae, which are prokaryotic organisms, have a nucleus with genetic material. The cell also contains standard essential organelles:
- mitochondria;
- cytoplasm;
- endoplasmic reticulum;
- Golgi apparatus;
- lysosomes;
- ribosomes;
- cell center.
A feature can be called the presence of plastids containing one or another pigment (chlorophyll, xanthophyll, phycoerythrin and others). Also interesting is the fact that unicellular algae can move freely in the water column using one or more flagella. However, not all types. There are also forms attached to the substrate.
Distribution and habitats
Thanks to their small size and some structural features, unicellular algae managed to spread throughout the globe. They inhabit:
- fresh water bodies;
- seas and oceans;
- swamps;
- surfaces of rocks, trees, stones;
- polar plains covered with snow and ice;
- aquariums.
Where can you find them! Thus, Nostok unicellular algae, examples of blue-green or cyanobacteria - inhabitants permafrost Antarctica. Having different pigments, these organisms amazingly decorate the snow-white landscape. They paint the snow in pink, lilac, green, purple and blue tones, which, of course, looks very beautiful.
Green unicellular algae, examples of which include the following: chlorella, trentepoly, chlorococcus, pleurococcus - live on the surface of trees, covering their bark with a green coating. They force the surface of stones, the top layer of water, areas of land, to acquire the same color. sheer cliffs and other places. They belong to the group of terrestrial or aerial algae.
In general, representatives of unicellular algae surround us everywhere; it is only possible to notice them with the help of a microscope. Red, green and cyanobacteria live in water, air, on the surfaces of products, soil, plants and animals.
Reproduction and lifestyle
The lifestyle of a particular algae should be discussed in each specific case. Some people prefer to swim freely in the water column, forming phytobenthos. Other species are placed inside the organisms of animals, entering into a symbiotic relationship with them. Still others simply attach to the substrate and form colonies and filaments.
But the reproduction of unicellular algae is a process similar for all representatives. This is a common vegetative division in two, mitosis. The sexual process occurs extremely rarely and only when unfavorable living conditions occur.
Asexual reproduction comes down to the following stages.
- Preparatory. The cell grows and develops, accumulates nutrients.
- Organelles of movement (flagella) are reduced.
- Then the process of DNA replication begins and the simultaneous formation of a transverse constriction.
- Centromeres stretch genetic material to different poles.
- The constriction closes and the cell divides in half.
- Cytokinesis occurs simultaneously with all these processes.
The result is new daughter cells identical to the mother one. They complete the missing parts of the body and begin independent life, growth and development. Thus, life cycle of a single-celled individual begins with division and ends with the same.
Structural features of green unicellular algae
The main feature is the rich green color which the cell has. It is explained by the fact that the pigment chlorophyll predominates in the composition of plastids. That is why these organisms are able to produce organic matter for themselves independently. This in many ways makes them similar to the higher terrestrial representatives of the flora.
Also, the structural features of green unicellular algae consist of the following general principles.
- The reserve nutrient is starch.
- An organelle such as a chloroplast is surrounded by a double membrane, which is found in higher plants.
- For movement they use flagella covered with hairs or scales. There can be from one to 6-8.
It is obvious that the structure of green unicellular algae makes them special and brings them closer to highly organized representatives of terrestrial species.
Who belongs to this department? The most famous representatives:
- chlamydomonas;
- Volvox;
- chlorella;
- pleurococcus;
- green euglena;
- acrosiphony and others.
Let's take a closer look at several of these organisms.
Chlamydomonas
This representative belongs to the department of green unicellular algae. Chlamydomonas is a predominantly freshwater organism that has some structural features. It is characterized by positive phototaxis (movement towards the light source), due to the presence of a light-sensitive eye at the front end of the cell.
The biological role of Chlamydomonas is that it is an oxygen producer during photosynthesis and a valuable source of feed for livestock. It is also this algae that causes “blooming” of water bodies. Its cells are easily cultivated under artificial conditions, so geneticists chose Chlamydomonas as an object laboratory research and experiments.
Chlorella
The single-celled algae Chlorella also belongs to the green group. Its main difference from all others is that it lives only in and its cell is devoid of flagella. The ability to photosynthesize allows chlorella to be used as a source of oxygen in space (on ships, rockets).
Inside the cell there is a unique complex of vitamins, thanks to which this algae is highly valued as a feed source for livestock. Even for humans, eating it would be very beneficial, because 50% of the protein in its composition exceeds energy value many grain crops. However, it still did not take root as food for people.
But chlorella is successfully used for biological water purification. This organism can be observed in glassware with stagnant water. A slippery green coating forms on the walls. This is chlorella.
Euglena green
A single-celled algae that belongs to the Euglena family. The unusual, elongated body shape with a pointed end makes it different from others. It also has a light-sensitive eye and a flagellum for active movement. An interesting fact is that euglena is a mixotroph. It can feed heterogeneously, but in most cases it carries out the process of photosynthesis.
For a long time there were disputes about the belonging of this organism to any kingdom. According to some characteristics it is an animal, according to others it is a plant. It lives in bodies of water polluted with organic residues.
Pleurococcus
These are round green organisms that live on rocks, earth, stones, and trees. They form a bluish-green coating on surfaces. They belong to the Chaetophora family of green algae.
It is by pleurococcus that one can navigate in the forest, since it settles only on the north side of trees.
Diatoms
A unicellular algae is a diatom and all its accompanying species. Together they form diatoms, which differ in one interesting feature. The top of their cell is covered with a beautiful patterned shell, onto which a natural pattern of silicon salts and its oxide is applied. Sometimes these patterns are so incredible that it seems like some kind of architectural structure or an intricate drawing by an artist.
Over time, dead representatives of diatoms form valuable deposits of rocks that are used by humans. The cell composition is dominated by xanthophylls, which is why the color of these algae is golden. They are valuable food for marine animals, as they form a significant part of plankton.
Red algae
These are species whose color varies from light red to orange and dark burgundy. The cell composition is dominated by other pigments that suppress chlorophyll. We are interested in unicellular forms.
This group includes the class of bangie algae, which includes approximately 100 species. Of these, a significant portion are unicellular. The main difference is the predominance of carotenes and xanthophylls, phycobilins over chlorophyll. This explains the coloring of the representatives of the department. There are several of the most common organisms among unicellular red algae:
- porphyridium.
- lame father.
- geotrichum.
- asterocytis.
The main habitats are oceanic and sea waters temperate latitudes. In the tropics they are much less common.
Porphyridium
Anyone can observe where single-celled algae of this species live. They form blood-red films on the ground, walls, and other wet surfaces. They rarely exist alone; they mainly gather in colonies surrounded by mucus.
They are used by humans to study processes such as photosynthesis in unicellular organisms and the formation of polysaccharide molecules inside organisms.
Chrootse
This algae is also unicellular and belongs to the red department, the class Banguiaceae. Its main distinctive feature- this is the formation of a mucous “leg” for attachment to the substrate. Interestingly, this “leg” can exceed the size of the body itself by almost 50 times. Mucus is produced by the cell itself during its life processes.
This organism settles on soils, also forming a noticeable red coating that is slippery to the touch.
Algae are classified into a separate subkingdom. And this is not surprising! Scientists have proven that despite the absence of a stem and root, like higher plants, these unique living organisms are not classified in their kingdom, since they have many characteristics that characterize them as a separate area of living organisms.
Biology, a science that studies all life on the planet, gives its definition to this kingdom. Algae, in Latin "algae", are the lower plant organisms. These are spore-bearing plant structures. Taxonomy defines more than 10 various types. Their names are written in both Latin and Russian.
In nature, both unicellular and multicellular representatives of this kingdom are found. Below we will briefly consider the accepted classification of organisms, give examples, and also talk about the main life processes of these living organisms.
In the end, let’s try to figure out: what is their main role in nature, what main groups are distinguished in this sub-kingdom, what are the characteristics of the representatives of various departments, what algae look and how they live, and how they can be used in everyday life.
Department: Green algae
The body of all algae is a thallus.
Chlamydomonas
List of representatives:
- Chlamydomonas is a subspecies of unicellular motile organisms;
- Spirogyra is a subspecies of filamentous organisms;
- Ulva is a subspecies of thalliform marine deep-sea representatives;
- Ulothrix is a subspecies of diatoms.
Using Chlamydomonas as an example, let’s look at what green algae are made of, how the processes of respiration, nutrition and reproduction occur, etc.
As a single-celled eukaryotic organism, it includes:
- Golgi apparatus;
- mitochondria;
- ribosomes;
- vacuoles
In addition, she has a formation that helps retain carbon dioxide in her body. It is with the help of him that she breathes. It moves, as a rule, with the help of 2 flagella, like a “corkscrew”. There are two types of reproduction in this species: asexual (by spores) and sexual (by heterolytic organisms).
The listed signs show that Chlamydomonas is a simple creature.
Department: Red algae
In their structure they are very similar to green algae.
These are the same unicellular algae, usually having a dismembered body: parts carry out photosynthesis, but nutrition occurs through a complete thallus. Reproduction also comes in two types.
Department: Brown algae
Representatives of this department are well adapted to harsh environmental changes. As an example, consider kelp.
This is a multicellular organism covered with a membrane containing pigments.
The thallus is divided into a sole and a plate. They do not have a conducting system - they absorb nutrients throughout the entire surface of the body. Reproduction is sexual, with each representative having reproductive organs both sexes.
How they eat
Nutrition occurs through photosynthesis, when carbon dioxide and other salts are exchanged in plastids with the help of chloroplasts.
In some cases, organic oxidation of oxygen is possible. Most often it is mixed: photosynthesis and heterotrophic nutrition occur simultaneously.
Reproduction
There are two types: asexual and sexual.
Asexuality can occur:
- Vegetatively - the formation of new forms and their subsequent separation from algae.
- Fragmentation - occurs in filamentous representatives: the thread is divided into two identical parts in a strictly defined position.
- Binary fission - single-celled organisms divide in half and then exist independently of each other.
- Zoospores and aplanospores - organisms reproduce using flagella.
Sexual reproduction occurs through the fusion of gametes of both sexes.
Variety of colors
This is explained by the different depths at which algae live. For example, red algae, living at a depth of 200 meters, have special pigments - carotenoids and phycobilins, which can capture light even at such a distance.
Green representatives live on the surface and contain chlorophyll. Brown ones contain fucoxanthin, they absorb blue light, which is why they have such a shade.
It is worth noting: the deeper the algae grows, the less sunlight arrives, that’s why the coloring is different.
Adaptation to terrestrial life
According to scientists, algae have adapted to terrestrial life, and the evolution started from green ones - representatives of single-celled organisms.
Further, the diversity of forms through the separation of functions of individual elements of the body structure of algae, division and fragmentation, adaptation to more complex environmental conditions helped the emergence of multicellular representatives of this kingdom.
Difference from higher plants
They lack a stem and roots, but have a thallus. Algae lack tissues like higher plants. Organs reproductive system, as a rule, unicellular.
Meaning
Algae playing important role in the life of animals and humans:
Despite such a wide range useful properties, algae significantly harm water bodies and interfere with the full operation of the engines of ships, motor ships and steamships.
Seaweed- these are multicellular, predominantly aquatic, eukaryotic photosynthetic organisms that do not have tissues or whose body is not differentiated into vegetative organs (i.e., belonging to the subkingdom of lower plants).
❖ Systematic divisions of algae(they differ in the structure of the thallus, the set of photosynthetic pigments and reserve nutrients, the characteristics of reproduction and development cycles, habitat, etc.):
■ Golden;
■ Green (examples: spirogyra, ulotrix);
■ Red (examples: porphyry, phyllophora);
■ Brown (examples: lessonia, fucus);
■ Characeae (examples: hara, nitella);
■ Diatoms (example: Lycmophora), etc.
The number of algae species is more than 40 thousand.
❖Algae habitat: fresh and salt water bodies, wet soil, tree bark, hot springs, glaciers, etc.
❖ Environmental groups algae: planktonic, benthic (), terrestrial, soil, etc.
Planktonic forms are represented by green, golden and yellow-green algae, which have special adaptations to facilitate transport by water: reducing the density of organisms (gas vacuoles, lipid inclusions, gelatinous consistency) and increasing their surface (branched outgrowths, flattened or elongated body shape, etc.).
Benthic forms live at the bottom of reservoirs or envelop objects in the water; They are attached to the substrate by rhizoids, basal discs and suckers. In the seas and oceans they are represented mainly by brown and red algae, and in fresh water bodies - by all departments of algae, except brown algae. Benthic algae contain large chloroplasts with a high chlorophyll content.
Ground, or air, algae (usually Green or Yellow-green algae) form deposits and films of various colors on the bark of trees, wet stones and rocks, fences, roofs of houses, on the surface of snow and ice, etc. When there is a lack of moisture, terrestrial algae become saturated with organic and inorganic substances.
Soil algae (mainly Yellow-green, Golden and Diatoms) live in the thickness of the soil layer at a depth of 1-2 m.
Features of the structure of algae
The body of algae is not divided into vegetative organs and is durable and elastic thallus (thallus) . The structure of the thallus is filamentous (examples: ulotrix, spirogyra), lamellar (example: kelp), branched or bushy (example: chara). Dimensions - from 0.1 mm to several tens of meters (for some brown and red algae). The thallus of branched and bushy algae is dissected and has a linear-segmented structure; it can be distinguished main axis, “leaves” and rhizoids.
Some algae have special air bubbles , which hold the thallus near the surface of the water, where there is the possibility of maximum light capture for photosynthesis.
The thallus of many algae secretes mucus, which fills their internal cavities and is partially discharged out, helping to better retain water and prevent dehydration.
Algal thallus cells are not differentiated and have a permeable cell wall, the inner layer of which consists of cellulose, and the outer layer of pectin substances and (in many species) a number of additional components: lime, lignin, cutin (retaining ultraviolet rays and protecting cells from excessive loss of water during low tide ) etc. The shell performs protective and support function while providing opportunity for growth. With a lack of moisture, the shells thicken significantly.
The cytoplasm of the cell in most algae forms a thin layer between the large central vacuole and the cell wall. The cytoplasm contains organelles: chromatophores , endoplasmic reticulum, mitochondria, Golgi apparatus, ribosomes, one or more nuclei.
Chromatophores- these are algal organelles containing photosynthetic pigments, ribosomes, DNA, lipid granules and pyrenoids . Unlike the chloroplasts of higher plants, chromatophores are more diverse in shape (can be cup-shaped, ribbon-shaped, lamellar, star-shaped, disc-shaped, etc.), size, number, structure, location and set of photosynthetic pigments.
In shallow water ( green ) algae photosynthetic pigments are mainly chlorophylls a and b, which absorb red and yellow light. U brown algae that live at medium depths, where green and blue light penetrates, the photosynthetic pigments are chlorophylls a and c, as well as arotin and fucoxanthin having a brown color. In red algae, which live at depths of up to 270 m, the photosynthetic pigments are chlorophyll d (characteristic only for this group of plants) and have a reddish color phycobilins- phycoerythrin, phycocyanin and allophycocyanin, which absorb blue and violet rays well.
Pyrenoids- special inclusions that are part of the chromatophore matrix and are a zone of synthesis and accumulation of reserve nutrients.
Algae reserves: starch, glycogen, oils, polysaccharides, etc.
Algae propagation
Algae reproduce asexually and sexually.
❖ Reproductive organs of algae (unicellular):
■ sporangia (organs asexual reproduction);
■ gametangia (organs of sexual reproduction).
❖ Methods of asexual reproduction of algae: vegetative (thallus fragments) or single-celled zoospores.
❖ Forms of the sexual process in algae:
■ isogamy
- fusion of motile gametes of identical structure and size,
■ heterogamy
- fusion of mobile gametes of different sizes (the larger one is considered female),
■ oogamy
- fusion of a large immobile egg with a sperm,
■ conjugation- fusion of the contents of two unspecialized cells.
The sexual process ends with the formation of a diploid zygote, from which a new individual is formed or motile flagella are formed zoospores , serving for the dispersal of algae.
❖ Features of algae reproduction:
■ in some types of algae, each individual is capable of forming (depending on the time of year or environmental conditions) both spores and gametes;
■ y individual species algae, the functions of asexual and sexual reproduction are performed by different individuals - sporophytes
(they form spores) and gametophytes (they form gametes);
■ in the development cycle of many types of algae (red, brown, some green) there is a strict alternation of generations - sporophyte and gametophyte
;
■ gametes of algae, as a rule, have taxis, which determine the direction of their movement depending on the intensity of light, temperature, etc.;
■ flagellated spores perform amoeboid movement;
■ in seaweed, the release of spores or gametes coincides with the tide; there is no rest period in the development of the zygote (i.e., the zygote begins to develop immediately after fertilization, so as not to be carried away to the sea).
The meaning of algae
❖ Meaning of algae:
■ they produce through photosynthesis organic matter;
■ saturate water with oxygen and absorb carbon dioxide from it;
■ are food for aquatic animals;
■ are the ancestors of plants that colonized the land;
■ participated in the formation of mountain limestone and chalk rocks, some types coal and oil shale;
■ green algae clean water bodies polluted with organic waste;
■ used by humans as organic fertilizers and feed additives in the diet of animals;
■ used in the biochemical, food and perfume industries for the production of proteins, vitamins, alcohols, organic acids, acetone, iodine, bromine, agar-agar (necessary for the production of marmalade, pastille, soufflé, etc.), varnishes, dyes, glue ;
■ many species are used for human food (kelp, some green and red algae);
■ some types are used in the treatment of rickets, goiter, gastrointestinal and other diseases;
■ sludge from dead algae (sapropel) is used in mud therapy;
■ can cause “blooming” of water.
Green algae
❖ Spirogyra
■ Habitat: fresh standing and slowly flowing reservoirs, where it forms bright green mud; widespread in Belarus.
■ Body Shape: thin thread-like; the cells are arranged in one row.
■ Structural features cells are cylindrical in shape with a well-defined cell wall; covered with a pectin shell and a mucous sheath. The chromatophore is ribbon-shaped, spirally twisted. The vacuole occupies most of the cell. The nucleus is located in the center and is connected by cords to the wall cytoplasm; contains a haploid set of chromosomes.
■ Reproduction: asexual carried out by breaking the thread into short sections; there is no sporulation. Sexual process - conjugation. In this case, two threads of algae are usually located parallel to each other and grow together with the help of copulation processes or bridges. Then the cell membranes at the points of contact of the threads dissolve, forming a through channel through which the contents of one of the cells move into the cell of the other thread and merge with its protoplast, forming a zygote with a dense membrane. The zygote divides by meiosis; 4 nuclei are formed, three of them die; from the remaining cell, after a period of rest, an adult develops.
❖ Ulotrix
■ Habitat: fresh, less often sea and brackish water bodies, soil;
- What is the structure of a plant cell?
- What are plastids?
- What plastids do you know?
- What are pigments?
- What is plant tissue called?
Algae are the most ancient plants on Earth. They mainly live in water, but there are species that live in damp areas of soil, tree bark and other places with high humidity.
Among algae there are unicellular and multicellular plants. Algae belong to lower plants, they have no roots, no stems, no leaves. Algae reproduce asexually ( simple division cells or spores) and sexually.
Despite its relatively simple structure, various groups algae have their own characteristics and come from different ancestors.
Green algae live in salty and fresh water, on land, on the surface of trees, stones or buildings, in damp, shaded places. Species that live out of water are dormant during drought periods. The simplest green algae are unicellular (Fig. 58).
Rice. 58. Unicellular algae
You, obviously, have observed the “blooming” of water in puddles and ponds in summer, and in strong lighting in aquariums. “Blooming” water has an emerald hue. If you scoop up some of this water, it will turn out to be clear, but containing small suspended “particles”. In a drop of such water, under a microscope, many different single-celled green algae are clearly visible, which give it an emerald hue.
During the “blooming” of small puddles or ponds, the unicellular alga Chlamydomonas (translated from Greek as “the simplest organism covered with clothing” - a shell) is most often found in the water. Chlamydomonas is a pear-shaped, single-celled green algae. It moves in water with the help of two flagella located at the anterior, narrower end of the cell (Fig. 59).
Rice. 59. Chlamydomonas and chlorella
On the outside, Chlamydomonas is covered with a transparent membrane, under which there is cytoplasm with a nucleus, a red “eye” (a light-sensitive red body), a large vacuole filled with cell sap, and two small pulsating vacuoles. Chlorophyll and other pigments in Chlamydomonas are located in a large cup-shaped plastid, which in algae is called a chromatophore (translated from Greek as “carrying light”). The chlorophyll contained in the chromatophore gives the entire cell a green color.
Another single-celled green algae, chlorella, is widespread in fresh water bodies and wet soils (see Fig. 59). Its small spherical cells are visible only with a microscope. The outside of the chlorella cell is covered with a membrane, under which there is cytoplasm with a nucleus, and in the cytoplasm there is a green chromatophore.
The structure of green unicellular algae
- Place a drop of “blooming” water on a microscope slide and cover with a coverslip.
- Examine unicellular algae at low magnification. Look for Chlamydomonas (a pear-shaped body with a pointed front end) or Chlorella (a spherical body).
- Remove some of the water from under the cover glass with a strip of filter paper and examine the algae cell under high magnification.
- Find the membrane, cytoplasm, nucleus, and chromatophore in the algae cell. Pay attention to the shape and color of the chromatophore.
- Draw a cell and label the names of its parts. Check the correctness of the drawing using the drawings in the textbook.
You probably paid attention to green deposits in the lower parts of trees, on fences, etc. They are formed by various unicellular green algae that have adapted to terrestrial life (Fig. 60). Under a microscope, single cells or groups of green algae cells are visible. The only source of moisture for these algae is precipitation(rain and dew). If there is a lack of water or low temperatures pleurococcus and other terrestrial algae can spend part of their lives in a dormant state.
Rice. 60. Green algae on a tree trunk
In multicellular representatives of green algae, the body (thallus) has the shape of threads or flat leaf-like formations. In flowing bodies of water you can often see bright green clusters of silky threads attached to underwater rocks and snags. This is a multicellular filamentous green algae ulothrix (Fig. 61). Its filaments consist of a number of short cells. In the cytoplasm of each of them there is a nucleus and a chromatophore in the form of an open ring. The cells divide and the thread grows.
Rice. 61. Multicellular green algae
In stagnant and slowly flowing waters, slippery bright green lumps often float or settle to the bottom. They look like cotton wool and are formed in clusters filamentous algae spirogyra (see Fig. 61). The elongated cylindrical cells of Spirogyra are covered with mucus. Inside the cells there are chromatophores in the form of spirally twisted ribbons.
Multicellular green algae also live in the waters of seas and oceans. An example of such algae is Ulva, or sea salad, about 30 cm long and only two cells thick (see Fig. 61).
The most complex structure in this group of plants is found in charophyte algae, which live in freshwater bodies. These numerous green algae resemble horsetails in appearance. Charovaya algae nitella, or flexible glitter, is often grown in aquariums (see Fig. 61).
Characeae have formations that, in shape and function, resemble roots, stems, and leaves, but in structure they have nothing in common with these organs of higher plants. For example, they are attached to the ground with the help of colorless branched thread-like cells, which are called rhizoids (from the Greek words “rhiza” - root and “eidos” - species).
Brown algae mainly sea plants. General external sign These algae have yellowish-brown coloration of the thalli.
Brown algae are multicellular plants. Their length ranges from microscopic to gigantic (several tens of meters). The thalli of these algae can be filamentous, spherical, lamellar, or bush-like. Sometimes they contain air bubbles that hold the plant upright in the water. Brown algae are attached to the ground by rhizoids or a disc-like overgrown base of the thallus.
Some brown algae develop groups of cells that can be called tissues.
In our Far Eastern seas and the seas of the North Arctic Ocean a large brown algae, kelp, or seaweed grows (Fig. 62). In the coastal strip of the Black Sea, the brown alga Cystoseira is often found (see Fig. 62).
Rice. 62. Brown algae
Red algae, or scarlet algae, are mainly multicellular marine plants (Fig. 63). Only some species of scarlet grass are found in fresh water bodies. Very few red algae are single-celled.
Rice. 63. Red algae
The sizes of scarlet mushrooms usually range from a few centimeters to a meter in length. But among them there are also microscopic forms. In addition to chlorophyll, the cells of red algae contain red and blue pigments. Depending on their combination, the color of the scarlets changes from bright red to bluish-green and yellow.
Externally, red algae are very diverse: filamentous, cylindrical, plate-like and coral-like, dissected and branched to varying degrees. They are often very beautiful and whimsical.
In the sea, red algae is found everywhere in the most different conditions. They usually attach to rocks, boulders, man-made structures, and sometimes other algae. Due to the fact that red pigments are able to capture even very small amounts of light, scarlet plants can grow at considerable depths. They can be found even at a depth of 100-200 m. Phyllophora, porphyry, etc. are widespread in the seas of our country.
The importance of algae in nature and human life. Fish and other aquatic animals feed on algae. Algae absorb carbon dioxide from water and, like all green plants, release oxygen, which living organisms living in water breathe. Algae produce great amount oxygen, which not only dissolves in water, but is also released into the atmosphere.
Man uses seaweed V chemical industry(Fig. 64). From them we obtain iodine, potassium salts, cellulose, alcohol, acetic acid and other products. Algae are used as fertilizers and fed to livestock. From some types of red algae, a gelatinous substance agar-agar is extracted, which is necessary in the confectionery, baking, paper and textile industries. Microorganisms are grown on agar-agar for use in laboratory research.
Rice. 64. Meaning and use of algae
In many countries, seaweed is used to prepare a variety of dishes. They are very useful, as they contain a lot of carbohydrates, vitamins, and are rich in iodine.
Laminaria (seaweed), ulva (sea lettuce), porphyra, etc. are especially often eaten.
Chlamydomonas, chlorella and other unicellular green algae are used for biological treatment Wastewater.
Excessive growth of algae, such as in irrigation canals or fish ponds, can be harmful. Therefore, canals and reservoirs have to be periodically cleared of these plants.
Presence of algae - necessary condition for the normal life of reservoirs. If sewage, chemical waste, scrap metal, rotting wood and other materials are dumped into them, this inevitably leads to the death of algae, other plants and animals, and the appearance of dead and contaminated water bodies.
New concepts
Seaweed. Chromatophore. Rhizoids. Chlamydomonas. Chlorella. Kelp
Questions
- Why are algae classified as lower plants?
- Where do green unicellular algae live?
- What is the structure of Chlamydomonas?
- Where do green multicellular algae live and what structure do they have?
- Where do brown algae live and what structure do they have?
- Where do red algae live and what structure do they have?
- What is thallus?
- What is a chromatophore?
- What are rhizoids? Why can't they be called roots?
- What is the significance of algae in nature?
- How do people use seaweed?
Think
Why do even large multicellular algae lack a vascular system?
Quests for the curious
Remove carefully green coating from the bark of several trees. Prepare microslides and examine them under a microscope. Look at the algae cells that form the green coating. Try to determine whether it is formed by one or more types of algae.
Do you know that...
- In many places globe so-called “red snow” is observed. In our country, this phenomenon occurs in the Caucasus, Northern Urals, and in some areas of Siberia and the Arctic. The unusual color of snow is caused by the so-called snow chlamydomonas. Its cells contain red pigment. When the upper layers of snow thaw, the cells of this algae begin to multiply very quickly, coloring the snow in all shades of red: from pale pink to blood red and dark crimson. Sometimes the area covered with “red snow” reaches several square kilometers.
- Giant Pacific brown algae grows 45 cm per day and reaches a length of 60 m.
- In the area of the Bahamas, red algae was found at a depth of 269 m, despite the fact that at this depth the water absorbs 99.9995% of sunlight.
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