The underwater world has always attracted people with its brightness, unprecedented beauty, diversity and unknown secrets. Amazing animals, amazing 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, visible only under a microscope, but because of 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 Description
In general, algae is a sub kingdom of the Lower Plants. They belong to this group for the reason that their body is not differentiated into organs, but represented by a solid (sometimes dissected) thallus or thallus. Instead of the root system, they have devices for attaching to the substrate in the form of rhizoids.
This group of organisms is very numerous, diverse in shape and structure, lifestyle and habitat. The following departments of this family are distinguished:
- reds;
- brown;
- green
- golden;
- diatoms;
- cryptophytic;
- yellow green
- euglenic;
- dinophytic.
Each of these departments may include unicellular algae and representatives with 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, practical ones, is the way energy is absorbed. Representatives of green unicellular algae are all autotrophs; most multicellular organisms of the same class also carry out photosynthesis. However, there are heterotrophic, mixotrophic and even parasitic forms.
Let us examine in more detail the structure, vital activity and reproduction of representatives of precisely unicellular organisms belonging to different classes of algae. Let us evaluate their role in nature and human life.
Structural Features of Unicellular Algae
What are the specific features that allow these tiny organisms to exist? Firstly, although they have only one cell, but it performs all the vital functions of the whole organism:
- height;
- development;
- food;
- breath;
- reproduction;
- motion;
- selection.
Also, these unicellular organisms have an inherent function of irritability.
In their internal structure, unicellular algae do not have 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 surrounding moisture, so the body can immerse itself in water. This allows algae to spread more widely, not only in the seas, oceans and other bodies of water, but also on land.
The core with the genetic material are all representatives, except for blue-green algae, which are prokaryotic organisms. The cell also includes standard binding 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 freely move in the water column using one or more flagella. However, not all species. There are also forms attached to the substrate.
Distribution and habitats
Due to its 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 you just will not meet them! So, nostock unicellular algae, examples of blue-green or cyanobacteria are inhabitants of the permafrost of Antarctica. Having different pigments in their composition, these organisms wonderfully adorn themselves with a 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 are: 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, land, steep cliffs and other places. They belong to the group of land or air algae.
In general, representatives of unicellular algae surround us everywhere, just to notice them is possible only with a microscope. Red, green and golden algae, as well as cyanobacteria, live in water, air, on the surfaces of products, land, plants and animals.
Reproduction and lifestyle
The lifestyle of a particular alga should be discussed in each case. Someone prefers to swim freely in the water column, forming phytobenthos. Other species are placed inside animal organisms, entering into symbiotic relationships with them. Still others simply attach to the substrate and form colonies and strands.
But the reproduction of unicellular algae is a process similar for all representatives. This is the usual vegetative bisection, mitosis. The sexual process is extremely rare and only upon the onset of adverse living conditions.
Asexual reproduction is reduced to the following stages.
- Preparatory. The cell grows and develops, accumulates nutrients.
- Organoids of movement (flagella) are reduced.
- Then begins the process of DNA replication and the simultaneous formation of a transverse constriction.
- Centromeres stretch genetic material at 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. They complete the missing parts of the body and begin independent life, growth and development. Thus, the life cycle of a single-celled individual begins with division and ends with it.
Structural features of green unicellular algae
The main feature is the saturated green color that the cell has. It is explained by the fact that chlorophyll pigment 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. This is in many ways related to them with the highest terrestrial representatives of the flora.
Also, the structural features of green unicellular algae are in the following general laws.
- The reserve nutrient is starch.
- An organoid such as chloroplast is surrounded by a double membrane, which is found in higher plants.
- For movement, flagella are used, covered with hairs or scales. They 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;
- acrosiphony and others.
Let us consider in more detail several such organisms.
Chlamydomonas
This representative belongs to a department such as green unicellular algae. Chlamydomonas is a predominantly freshwater organism that has some structural features. It is characterized by positive phototaxis (movement toward 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 photosynthesis, a valuable source of feed for livestock. Also, it is this algae that causes the "bloom" of water bodies. Its cells are easily cultivated under artificial conditions, so geneticists have chosen Chlamydomonas as an object of laboratory research and experiments.
Chlorella
The unicellular alga chlorella also belongs to the green department. 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 alga is highly regarded as a forage base for livestock. Even for humans, eating it would be very profitable, because 50% of the protein in its composition surpasses many crops in energy value. However, as food for people, she still did not take root.
But chlorella is successfully used for biological treatment of water. You can observe this organism in a glass bowl with stagnant water. A slippery coating of green forms on the walls. This is chlorella.
Euglena green
Unicellular algae is euglena green, which belongs to the euglena department. Unusual, elongated with a pointed end, the body shape 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 eat heterogeneously, but in most cases it carries out the process of photosynthesis.
For a long time there was a debate about the belonging of this organism 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. Form a bluish-green coating on the surfaces. Khetoforovye algae of the green family belong to the family.
It is by pleurococcus that one can navigate in the forest, since it settles only on the north side of trees.
Diatoms
The unicellular alga is the diatom and all associated species. Together, they form diatoms, which differ in one interesting feature. From above, their cell is covered with a beautiful patterned carapace, on which a natural pattern of silicon salts and its oxide is applied. Sometimes these patterns are so incredible that it seems as if it is some kind of architectural structure or an intricate drawing of the artist.
Over time, dead representatives of diatoms form valuable deposits of rocks that are used by humans. Xanthophyllae predominate in the composition of the cell; therefore, the color of these algae is golden. They are a 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 maroon. The composition of the cell is dominated by other pigments that inhibit chlorophyll. We are interested in red algae, single-celled forms.
This group includes the class of bangium algae, which includes approximately 100 species. Of these, a significant part is unicellular. The main difference is the predominance of carotenes and xanthophylls, phycobilins over chlorophyll. This explains the coloring of the representatives of the department. We can distinguish several of the most common organisms among unicellular red algae:
- porphyridium.
- hototse.
- geotrichum.
- asterocytis.
The main habitats are ocean and sea waters of temperate latitudes. In the tropics are much less common.
Porphyridium
Everyone can observe where single-celled algae of this species live. They form blood-red films on the ground, walls, and other wet surfaces. They seldom exist alone, mostly they 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.
Hotothec
This alga is also unicellular and belongs to the red, the bangian class. Its main distinguishing feature is the formation of a “leg” mucosa for attachment to a 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 the soil, also forming a noticeable red coating, slippery to the touch.