How beautiful and amazing the underwater world is, it is just as mysterious. Until now, scientists have discovered some completely new, unusual species of animals, the incredible properties of plants are being investigated, and the areas of their application are expanding.
The flora of the oceans, seas, rivers, lakes and swamps is not as diverse as the land, but it is also unique and beautiful. Let's try to figure out what these amazing underwater plants are, what is the structure of algae and their significance in the life of humans and other living beings.
Systematic position in the system of the organic world
By generally accepted standards, algae are considered a group of lower plants. They are part of the Cellular kingdoms of Plants and the sub-kingdoms of Lower Plants. In fact, such a division is based precisely on the structural features of these representatives.
They got their name because they are able to grow and live under water. Latin name - Algae. Hence the name of the science involved in a detailed study of these organisms, their economic significance and structure, is formed - algology.
Classification of algae
Modernthe data allow us to attribute all available information about different types of representatives to ten departments. The division is based on the structure and activity of algae.
- Blue-green unicellular, or cyanobacteria. Representatives: cyanides, shotguns, microcystis and others.
- Diatoms. These include pinnularia, navicula, pleurosigma, melosira, gomphoneme, sinedra and others.
- Golden. Representatives: chrysodendron, chromulina, primnesium and others.
- Porphyry. These include porphyry.
- Brown. Laminaria, Sargassum, Cystoseira and others.
- Yellow-green. This includes classes such as Xanthopod, Xanthococcus, Xanthomonad.
- Reds. Gracilaria, anfeltia, crimson.
- Greens. Chlamydomonas, Volvox, Chlorella and others.
- Evshenovye. These include the most primitive representatives of the Greens.
- Char. Hara as the main representative.
This classification does not reflect the structure of algae, but only shows their ability to photosynthesize at different depths, showing pigmentation of one color or another. That is, the color of the plant is the sign by which it is assigned to a particular department.
Algae: structural features
Their main distinguishing feature is that the body is not differentiated into parts. That is, algae do not, like higher plants, have a clear division into a shoot, consisting of a stem, leaves and a flower, and a root system. The structure of the body of algae is represented by a thallus, orthallus.
In addition, the root system is also missing. Instead, there are special translucent thin thread-like processes called rhizoids. They perform the function of attaching to the substrate, while acting like suction cups.
Thallus itself can be very diverse in shape and color. Sometimes in some representatives it strongly resembles the shoot of higher plants. Thus, the structure of algae is very specific for each department, therefore, in the future it will be considered in more detail using the examples of the corresponding representatives.
Types of thalli
Thallus is the main distinguishing feature of any multicellular algae. The structural features of this organ are that the thallus can be of different types.
- Amoeboid.
- Monadic.
- Capsal.
- Coccoid.
- Filamented, or trichal.
- Sarcinoid.
- Faux fabric.
- Siphon.
- Pseudoparenchymal.
The first three are most typical for colonial and unicellular forms, the rest for more advanced, multicellular, complex organization.
This classification is only approximate, since each type has transitional variants, and then it is almost impossible to distinguish one from the other. The line of differentiation is erased.
Algae cell, its structure
The peculiarity of these plants lies initially in the structure of their cells. It is somewhat different from that of the higher representatives. There are several main points by which cells stand out.
- In some individuals, they contain specialized structures of animal origin - movement organelles (flagella).
- Sometimes there is stigma.
- Shells are not quite the same as those of an ordinary plant cell. They are often provided with additional carbohydrate or lipid layers.
- Pigments are enclosed in a specialized organ - the chromatophore.
The rest of the structure of the algae cell obeys the general rules of that of higher plants. They also have:
- nucleus and chromatin;
- chloroplasts, chromoplasts and other pigment-containing structures;
- vacuoles with cell sap;
- cell wall;
- mitochondria, lysosomes, ribosomes;
- Golgi apparatus, endoplasmic reticulum and other elements.
At the same time, the cellular structure of unicellular algae corresponds to that of prokaryotic creatures. That is, the nucleus, chloroplasts, mitochondria and some other structures are also missing.
The cellular structure of multicellular algae is fully consistent with that of higher land plants, with the exception of some specific features.
Green Algae Department: structure
This department includes the following species:
- unicellular;
- multicellular;
- colonial.
There are more than thirteen thousand species in total. Main classes:
- Volvox.
- Conjugates.
- Ulotrix.
- Siphon.
- Protococcal.
The peculiarities of the structure of unicellular organisms are that the outside of the cell is often covered with an additional shell that performs the function of a kind of skeleton - the pellicle. This allows it to be protected from external influences, keep a certain shape, and also form beautiful and amazing patterns of metal ions and s alts on the surface over time.
As a rule, the structure of green algae of a unicellular type necessarily includes some kind of organelle of movement, most often a flagellum at the rear end of the body. The reserve nutrient is starch, oil or flour. Main representatives: chlorella, chlamydomonas, volvox, chlorococcus, protococcus.
Very interesting are such representatives of siphons as caulerpa, codium, acetobularia. Their thallus is not a filamentous or lamellar type, but one giant cell that performs all the basic functions of life.
Multicellular organisms can be lamellar or filamentous. If we are talking about lamellar forms, then often they are multi-layered, and not just single-layered. Often the structure of this type of algae is very similar to the shoots of higher land plants. The more branches of the thallus, the stronger the similarity.
The main representatives are the following classes:
- Ulotrix - ulotrix, ulva, monostroma.
- Couplings, or conjugates - zygonema, spirogyra, muzhotsia.
Colonial forms are special. Structuregreen algae of this type lies in the close interaction between a large accumulation of unicellular representatives, united, as a rule, by mucus in the external environment. The main representatives can be considered volvox, protococcal.
Features of life activity
The main habitats are fresh water bodies and seas, oceans. Often cause the so-called flowering of water, covering its entire surface. Chlorella is widely used in cattle breeding, as it purifies and enriches water with oxygen, and the dry residue is fed to livestock.
Single-celled green algae can be used in spacecraft to produce oxygen through photosynthesis without changing their structure and dying. According to the time period, this particular department is the oldest in the history of underwater plants.
Red Algae Department
Another name for the department is Bagryanki. It appeared due to the special color of the representatives of this group of plants. It's all about the pigments. The structure of the red alga as a whole satisfies all the main features of the structure of lower plants. They can also be unicellular and multicellular, have a thallus of various types. There are both large and extremely small representatives.
However, their coloration is due to some features - along with chlorophyll, these algae have a number of other pigments:
- carotenoids;
- phycobilins.
They mask the main green pigment, so the color of plants can vary from yellow to bright red and crimson. It happensdue to the absorption of almost all wavelengths of visible light. Main representatives: anfeltia, phyllophora, gracilaria, porphyra and others.
Meaning and lifestyle
Able to live in fresh waters, but most are still marine representatives. The structure of the red algae, and specifically the ability to produce a special substance agar-agar, allows it to be widely used in everyday life. This is especially true for the food confectionery industry. Also, a significant part of the individuals is used in medicine and directly eaten by people.
Department Brown Algae: structure
Often, as part of the school curriculum of studying lower plants, their various departments, the teacher asks students: "List the structural features of brown algae." The answer will be this: the thallus has the most complex structure of all known individuals of lower plants; inside the thallus, which is often of an impressive size, there are conducting vessels; the thallus itself has a multi-layer structure, which is why it resembles the tissue type of higher land plants.
The cells of the representatives of these algae produce a special mucus, so the outside is always covered with a kind of layer. Reserve nutrients are:
- carbohydrate laminaritis;
- oils (different types of fats);
- alcohol mannitol.
Here's what to say if you are asked: "List the structural features of brown algae." There are actually a lot of them, and they are unique compared to other representatives.underwater plants.
Home use and distribution
Brown algae is the main source of organic compounds not only for marine herbivores, but also for people living in the coastal zone. Their use in food is widespread among different peoples of the world. Medicines are made from them, flour and minerals, alginic acids are obtained.
