Unicellular algae: features of the structure. Representatives of unicellular algae

Underwater world always attracted people with its brightness, unprecedented beauty, diversity and unknown secrets. Amazing animals, stunning plants of all sizes - all these unusual organisms do not leave anyone indifferent. In addition to the large representatives of the flora visible to the eye, there are also the smallest, visible only under a microscope, but this does not lose its importance and significance in the overall biomass of the ocean. These are unicellular algae. If we take the total production of organic matter produced by underwater plants, then most of them are produced, these tiny and amazing creatures.

Algae: a general characteristic

In general, algae is a sub-kingdom of the Lower plants. They refer 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 the root system, they have devices for attachment to the substrate in the form of rhizoids.

This group of organisms is very numerous, diverse in form and structure, lifestyle and habitats. The following divisions of this family stand out:

• Red;
• Brown;
• Green;
• Golden;
• Diatoms;
• Cryptophytic;
• Yellow-green;
• Euglenic;
• Dinophyte.

Each of these departments can include unicellular algae and representatives with a multicellular thallus. Also there are the following forms of organisms:

• Colonial;
• Filamentary;
• Free-floating;
• Attached and others.

Signs for classification can be found set. One of the most important, determining in practical terms - the way of energy absorption. Representatives of green unicellular algae are all autotrophs, most multicellular in the same class also carry out photosynthesis. However, heterotrophic, mixotrophic, and even parasitic forms are also encountered.

We will study in more detail the structure, vital activity and reproduction of representatives of precisely unicellular organisms belonging to different classes of algae. We will 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? First, although they have only one cell, but it performs all the vital functions of the whole organism:

• growth;
• development;
• food;
• breath;
• Reproduction;
• motion;
• Selection.

Also, this unicellular organism has a function of irritability.

In its internal structure, unicellular algae features that are able to surprise the interested researcher, do not have. All the same structures and organelles as in the cells of more highly developed organisms. The cell membrane has the ability to absorb the surrounding moisture, so the body can dive under water. This allows algae to spread more widely not only in the seas, oceans and other water bodies, but also on land.

The nucleus with the genetic material has all the representatives, except blue-green algae, which are prokaryotic organisms. Also in the cell are standard compulsory organelles:

• Mitochondria;
• cytoplasm;
• Endoplasmic reticulum;
• Golgi apparatus;
• Lysosomes;
• Ribosomes;
• The cellular center.

A special feature is 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 with the help of one or several flagella. However, not all species. There are also forms attached to the substrate.

Distribution and habitats

Due to the small size and some peculiarities of the structure, unicellular algae managed to spread all over the globe. They inhabit:

• Fresh water bodies;
• seas and oceans;
• Swamps;
• The surface of rocks, trees, stones;
• Polar plains covered with snow and ice;
• Aquariums.

Where they just do not meet! So, nostok unicellular algae, examples of blue-green or cyanobacteria - inhabitants of permafrost of Antarctica. Having in composition different pigments, these organisms wonderfully decorate a snow-white landscape. They paint the snow in pink, lilac, green, purple and blue tones, which, of course, looks very nice.

Green unicellular algae, examples of which can be given: chlorella, trentepolia, chlorococcus, pleurococcus - live on the surface of trees, covering their bark with a green bloom. They force to acquire the same color of the surface of the stones, the upper layer of water, plots of land, sheer cliffs and other places. They belong to a group of terrestrial or air algae.

In general, representatives of unicellular algae surround us everywhere, just to notice them is possible only with the help of a microscope. In the water, air, on the surfaces of products, earth, plants and animals live red, green and golden algae, as well as cyanobacteria.

Reproduction and way of life

On the lifestyle of a particular algae should be spoken in each case. Someone prefers to freely swim in the water column, forming phytobenthos. Other species are placed inside the animal organisms, entering into symbiotic relationships with them. Some simply attach themselves to the substrate and form colonies and strands.

But reproduction of unicellular algae is a process similar to all representatives. This is the usual vegetative division in two, mitosis. The sexual process is extremely rare and only when adversity conditions occur.

Asexual reproduction reduces to the following stages.

1. Preparatory. The cell grows and develops, accumulates nutrients.
2. The organoids of movement (flagella) are reduced.
3. Then begins the process of DNA replication and the simultaneous formation of a transverse waist.
4. Centromers stretch the genetic material at different poles.
5. The constriction closes, and the cell is divided in half.
6. Cytokinesis occurs simultaneously with all these processes.

The result is new daughter cells, identical to the parent cells. They complete the missing parts of the body and begin an independent life, growth and development. Thus, the life cycle of a unicellular individual begins with division and ends with it.

Features of the structure of green unicellular algae

The main feature is a rich green color, which has a cage. It is explained by the fact that the chlorophyll pigment predominates in the plastids. That is why these organisms are able to carry out the process of photosynthesis, producing for themselves an organic matter independently. This in many respects brings them closer to the higher land representatives of the flora.

Also features of the structure of green unicellular algae are the following general patterns.

1. The reserve nutrient is starch.
2. Such an organoid, as a chloroplast, is surrounded by a double membrane, which occurs in higher plants.
3. For movement, use flagella covered with hairs or scales. They can be from one to 6-8.

It is obvious that the structure of green unicellular algae makes them special and brings closer to highly organized representatives of terrestrial species.

Who is in this department? The most famous representatives:

• Chlamydomonas;
• Wolvox;
• chlorella;
• Pleurococcus;
• Euglena green;
• Acrosiphonia and others.

Let us consider in detail several such organisms.

Chlamydomonas

This representative refers to a department such as green unicellular algae. Chlamydomonas is a predominantly freshwater organism with some structural features. It is characterized by a positive phototaxis (movement toward the light source), due to the presence of a photosensitive eye on the anterior end of the cell.

The biological role of chlamydomonas is that it is a producer of oxygen in the process of photosynthesis, a valuable source of feed for livestock. It is also this alga that causes the "flowering" of water bodies. Her cells are easily cultivated under artificial conditions, so geneticists have chosen chlamydomonad as an object of laboratory research and experiments.

Chlorella

Single-celled chlorella algae also belongs to the department of green. Its main difference from all others is that it lives only in fresh water, and its cell is devoid of flagella. The ability to photosynthesize makes it possible to use chlorella as a source of oxygen in space (on ships, missiles).

Inside the cell contains a unique complex of nutrients and vitamins, thanks to which this alga is highly valued as a fodder base for cattle. Even for a person, eating it for food would be very beneficial, because 50% of the protein in its composition is superior to the energy value of many crops. However, as a food for people, it still did not get accustomed.

But chlorella is successfully used for biological water purification. Observe this organism can be in glassware with stagnant water. On the walls a slippery coating of green color is formed. This is chlorella.

Euglena the Green

A single-celled alga is euglena green, which belongs to the euglena division. Unusual, elongated with a pointed end shape of the body makes it different from others. It also has a photosensitive eye and a flagellum for active movement. An interesting fact is that euglena is a mixotroph. It can be fed heterogeneously, but in most cases it carries out the process of photosynthesis.

For a long time there was debate about the belonging of this organism to a certain kingdom. By one sign it is an animal, on others it is a plant. It dwells in water bodies contaminated with organic remnants.

Pleurococcus

These are round green organisms that live on rocks, earth, stones, trees. Form a blue-green coating on the surfaces. Relate to the family Hetoforovye algae of the department of green.

It is through the pleurococcus that one can orientate in the forest, since it settles only from the northern side of the trees.

Diatoms

A single-celled alga is the diatome and all its accompanying species. All together they form diatoms, which differ in one interesting feature. Above, their cell is covered with a beautiful patterned shell, on which a natural pattern of salts of silicon and its oxide is applied. Sometimes these patterns are so incredible that it seems like it's some kind of architectural structure or an intricate drawing of an artist.

Over time, dead representatives of diatoms form valuable deposits of rocks that are used by humans. Xanthophylls predominate in the cell, so the color of these algae is golden. They are a valuable food for marine animals, since they form a significant part of the plankton.

Red algae

These are such species, the color of which varies from light red to orange and maroon. In the cell structure, other pigments that suppress chlorophyll predominate. We are interested in red algae, unicellular forms.

This class includes the class of bangs algae, which includes about 100 species. Of these, a large proportion 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. One can distinguish several of the most common organisms among unicellular red algae:

• Porphyridium.
• Chrootec.
• Geotrichum.
• Asteroceitis.

The main habitats are the ocean and sea waters of temperate latitudes. In the tropics are much less common.

Porphyridium

Everyone can observe where single-cell algae of this species live. They form blood-red films on the ground, walls, other wet surfaces. Singly exist rarely, mostly collected in colonies, surrounded by mucus.

They are used by man to study such processes as photosynthesis in unicellular ones and the formation of polysaccharide molecules inside organisms.

Chrootec

This algae is also unicellular and belongs to the red department, the class of bang. Its main distinctive feature is the formation of a mucous "leg" for attachment to the substrate. It is interesting that this "leg" can exceed the dimensions of the body itself by almost 50 times. Slime is produced by the cell itself in the process of vital activity.

This organism settles on soils, also forming a noticeable red coating, slippery to the touch.