The underwater world has always attracted people with its brightness, unprecedented beauty, diversity and unexplored mysteries. Amazing animals, stunning plants of various 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 ones, visible only under a microscope, but from this they do not lose their importance and significance in the total 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 by these tiny and amazing creatures.
Algae: general characteristics
In general, algae is a sub-kingdom 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 attaching to the substrate in the formrhizoids.
This group of organisms is very numerous, diverse in form and structure, lifestyle and habitats. The following departments 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. The following forms of organisms are also found:
- colonial;
- filamentous;
- free floating;
- attached and others.
There are many signs for classification. One of the most important, determining in practical terms, is the method of energy absorption. Representatives of green unicellular algae are all autotrophs, most multicellular organisms of the same class also carry out photosynthesis. However, there are also heterotrophic, mixotrophic and even parasitic forms.
Let's study in more detail the structure, life activity and reproduction of representatives of exactly 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:
- growth;
- development;
- food;
- breath;
- reproduction;
- movement;
- selection.
The function of irritability is also inherent in these unicellular organisms.
In their internal structure, unicellular algae have no features that can 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 the surrounding moisture, so the body can be submerged under water. This allows algae to settle more widely not only in the seas, oceans and other water bodies, but also on land.
All representatives have a nucleus with genetic material, except for blue-green algae, which are prokaryotic organisms. The cell also includes standard mandatory 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 of interest is the fact that unicellular algae can move freely in the water column with the help of one or more flagella. However, not all types. There are also forms attached to the substrate.
Distribution and habitats
Due to their small size and some structural features, unicellularalgae have managed to spread throughout the globe. They inhabit:
- fresh waters;
- seas and oceans;
- bogs;
- surfaces of rocks, trees, stones;
- polar plains covered with snow and ice;
- aquariums.
Wherever you meet them! So, single-celled nostococcal algae, examples of blue-green or cyanobacteria, are inhabitants of the permafrost of Antarctica. Having different pigments in their composition, these organisms adorn the snow-white landscape in an amazing way. They paint the snow in pink, lilac, green, purple and blue tones, which, of course, looks very beautiful.
Green single-celled algae, examples of which are: chlorella, trentepolia, chlorococcus, pleurococcus - live on the surface of trees, covering their bark with a green coating. They make the surface of stones, the upper layer of water, plots of land, sheer cliffs and other places acquire the same color. They belong to the group of terrestrial or air algae.
In general, representatives of unicellular algae surround us everywhere, it is simply possible to notice them only with the help of a microscope. Red, green and golden algae, as well as cyanobacteria live in water, air, product surfaces, earth, plants and animals.
Reproduction and lifestyle
The way of life of a particular algae should be discussed in each case. Someone prefers to swim freely in the water column, forming phytobenthos. Other typesare 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 the usual vegetative division in two, mitosis. The sexual process is extremely rare and only when unfavorable conditions of existence occur.
Asexual reproduction comes down to the following stages.
- Preparatory. The cell grows and develops, accumulates nutrients.
- The organelles of movement (flagella) are reduced.
- Then, the process of DNA replication begins and the simultaneous formation of a transverse constriction.
- Centromeres stretch the genetic material along different poles.
- The constriction closes, and the cell is divided in half.
- Cytokinesis occurs simultaneously with all these processes.
The result is new daughter cells, identical to the mother. They complete the missing parts of the body and begin an independent life, growth and development. Thus, the life cycle of a single-celled individual begins and ends with division.
Features of the structure of green unicellular algae
The main feature is the rich green color that the cage 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 carry out the process of photosynthesis, producing organic matter for themselves on their own. This isin many ways they have in common with the highest terrestrial representatives of the flora.
Also, the structural features of green unicellular algae are in the following general patterns.
- The reserve nutrient is starch.
- An organelle like a chloroplast is surrounded by a double membrane, which is found in higher plants.
- Flagella covered with hairs or scales are used for locomotion. There can be from one to 6-8.
Obviously, 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;
- euglena green;
- Acrosiphonia and others.
Let's take a closer look at several of these organisms.
Chlamydomonas
This representative belongs to such a department as 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 photosensitive eye at the front end of the cell.
The biological role of chlamydomonas is that it is an oxygen producer in the process of photosynthesis, a valuable source of feed for livestock. Also, it is this algae that causes the "bloom" of reservoirs. Its cells are easily cultivated inartificial conditions, so geneticists chose chlamydomonas as an object of laboratory research and experiments.
Chlorella
Single-celled algae chlorella also belongs to the green division. Its main difference from all others is that it lives only in fresh water, and its cell is devoid of flagella. The ability to photosynthesis allows the use of chlorella as a source of oxygen in space (on ships, rockets).
Inside the cell contains a unique complex of nutrients and vitamins, thanks to which this algae is highly valued as a feed base for livestock. Even for a person, eating it would be very beneficial, because 50% of the protein in its composition is superior in energy value to many cereals. However, it still did not take root as food for people.
But chlorella is successfully used for biological water treatment. You can observe this organism in a glass dish with stagnant water. A slippery green coating forms on the walls. This is chlorella.
Green Euglena
Single-celled algae is Euglena green, which belongs to the department of Euglena. 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 ownership of thisorganism to any kingdom. According to some signs, this is an animal, according to others - a plant. It lives in reservoirs polluted with organic residues.
Pleurococcus
These are rounded green organisms that live on rocks, earth, stones, trees. They form a bluish-green coating on surfaces. They belong to the family of Chaetophore algae of the green department.
It is precisely by the pleurococcus that you can navigate in the forest, since it settles only on the northern side of the trees.
Diatoms
Single-celled algae is a diatom and all its accompanying species. Together they form diatoms, which differ in one interesting feature. From above, their cage is covered with a beautiful patterned shell, on which a natural pattern of silicon s alts 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. Xanthophylls predominate in the composition of the cell, so the color of these algae is golden. They are a valuable food for marine animals, as they form a significant part of the plankton.
Red algae
These species range in color from light red to orange to maroon. Other pigments that suppress chlorophyll predominate in the composition of the cell. We are interested in red algae, unicellular forms.
To this groupbelongs to the class of bangui algae, which includes approximately 100 species. Most of them 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 single-celled red algae:
- porphyridium.
- chrootse.
- geotrichum.
- asterocitis.
The main habitats are ocean and sea waters of temperate latitudes. In the tropics, they are much less common.
Porphyridium
Everyone can observe where unicellular algae of this species live. They form blood-red films on the ground, walls, and other wet surfaces. They rarely exist alone, mostly gathering in colonies surrounded by mucus.
Used by humans to study processes such as photosynthesis in unicellular organisms and the formation of polysaccharide molecules within organisms.
Chrootse
This algae is also unicellular and belongs to the department of reds, the class of banguis. Its main distinguishing feature 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 in the process of life.
This organism settles on soils, also forming a noticeable red coating, slippery to the touch.
