10. Vacuole 11. Hyaloplasm 12. Lysosome 13. Centrosome (Centriole)

eukaryotes, or Nuclear(lat. Eucaryota from the Greek εύ- - good and κάρυον - nucleus) - the kingdom of living organisms, whose cells contain nuclei. All organisms except bacteria and archaea are nuclear.

Essay on the topic: Pre-nuclear organisms

INTRODUCTION

1. THE SUPERKINGDOM OF THE PRE-NUCLEAR OR THE KINGDOM OF THE PROKARYOTES

2. STRUCTURE OF PROKARYOTES

2.1. Cell

2.2. Flagella

2.3. Pili and fimbriae

2.4. Plasma membrane, mesosomes and photosynthetic membranes

2.5. genetic material

3. PROKARYOT REPRODUCTION

4. LIFESTYLE OF PROKARYOTES

5. MAIN GROUPS OF PROKARYOTES

5.1. Bacteria are phototrophs

5.2. Bacteria are chemoautotrophs

5.3 Bacteria - organotrophs

6. BLUE-GREEN ALGAE

CONCLUSION

BIBLIOGRAPHY

INTRODUCTION

Pre-nuclear organisms - prokaryotes include the simplest unicellular organisms. In everyday life they are called bacteria or microbes.

Blue-green algae are also prokaryotes. In this work, I will try to describe the structure of prokaryotes, their reproduction, lifestyle, and the main groups of prokaryotes.

These microorganisms play a big role in our lives, so I'm interested in this topic.

Prokaryotes can be used in medicine. Until the second half of the last century, medicine was practically unable to treat diseases caused by bacteria. Now doctors with most of them successfully cope. Therefore, I believe that this topic is relevant today.

1. THE SUPERKINGDOM OF THE PRE-NUCLEAR OR THE KINGDOM OF THE PROKARYOTES

All known unicellular and multicellular organisms are quite naturally divided into two large groups - prokaryotes and eukaryotes.

All prokaryotes belong to the same kingdom Drobnyaki, represented by bacteria and blue-green algae.

Prokaryotic cells (from Greek pro - to, karion - core) do not have a formalized nucleus. In other words, the genetic material (DNA) of prokaryotes is located directly in the cytoplasm and is not surrounded by a nuclear membrane. There are two groups of bacteria: archaebacteria (from the Greek archaios - the oldest) and eubacteria.

2. STRUCTURE OF PROKARYOTES

Prokaryotes are much larger than viruses (on average 0.5 - 5 microns), the smallest of them can be smaller than the smallpox virus. The largest bacteria can be seen with the naked eye as dots and rods, but these are exceptions. Typically, prokaryotic cells are viewed under an optical microscope. For the first time, bacteria were noticed at the end of the 17th century by the Dutch naturalist A. van Leeuwenhoek in the simplest microscope - a magnifying glass from one tiny drop-shaped lens.

2.1. Cell

A prokaryotic cell is usually covered with a membrane (cell wall), like a plant cell. But this elastic, like a car tire, shell consists not of cellulose, but of the substance murein close to it (from the Latin “mura” - wall). Some bacteria (the same mycoplasmas) lost their membranes a second time.

2.2. Flagella

Many bacteria have flagella. Flagella are composed of identical spherical flagellin protein subunits (similar to muscle actin) that are arranged in a spiral and form a hollow cylinder about 10–20 nm in diameter. Despite the wavy shape of the flagella, they are quite rigid.

The flagella are driven by a unique mechanism. The base of the flagellum apparently rotates in such a way that the flagellum, as it were, is screwed into the medium without making random beats and, thus, moves the cell forward. This is apparently the only structure known in nature where the principle of the wheel is used.

Another interesting feature of flagella is the ability of individual flagellin subunits to spontaneously assemble in solution into helical filaments. Spontaneous self-assembly is a very important property of many complex biological structures. In this case, self-assembly is due to the amino acid sequence (primary structure) of flagellin. Motile bacteria can move in response to certain stimuli, that is, they are capable of taxis.

Flagella are easiest to see with an electron microscope using the metal sputtering technique. Flagella can be up to several dozen.

2.3. Pili and fimbriae

On the cell wall of some gram-negative bacteria, thin outgrowths (rod-shaped protein protrusions) called pili or fimbriae are visible. They are shorter and thinner than flagella and serve to attach cells to each other or to some surface, giving a specific "stickiness" to those strains that possess them. Drinking, there are different types. The most interesting are the so-called F-pills, which are encoded by a special plasmid and are associated with the sexual reproduction of bacteria.

2.4. Plasma membrane, mesosomes and photosynthetic membranes

Like all cells, the protoplasm of bacteria is surrounded by a semi-impermeable membrane. In some bacteria, the plasma membrane retracts into the cell and forms mesosomes or photosynthetic membranes.

mesosomes- folded membrane structures, on the surface of which there are enzymes involved in the process of respiration. Therefore, mesosomes can be called primitive organelles. During cell division, mesosomes bind to DNA, which appears to facilitate the separation of two daughter DNA molecules after replication and promote the formation of a septum between daughter cells.

2.5. genetic material

Bacterial DNA is represented by single circular molecules, about 1 mm long. Each such molecule consists of 5-10 0 pairs of nucleotides. The total content of DNA (genome) in a bacterial cell is much less than in a eukaryotic cell, and, consequently, the amount of information encoded in it is also smaller. On average, such DNA contains several thousand genes.

The shapes of prokaryotic cells are quite simple: balls ( cocci), sometimes combined in two (double coki- diplococci); generating chains ( streptococci) or glued into a kind of grape bunch ( staphylococci/ from Greek. staphylus - grapes), glued in four ( Sarcinas); sticks ( bacilli), curved sticks ( vibrios); corkscrew ( spirilla). Where branching forms of cells are less common.

The simplicity of the form makes it impossible to accurately identify prokaryotes by appearance. On the contrary, their physiology is so diverse that in microbiology, in the description of a new species or variety, it is necessary to indicate what the microorganism needs and what products it produces, that is, the main characteristics of exchange with the environment.

3. PROKARYOT REPRODUCTION

Prokaryotes reproduce most often by simple cell division. Budding is less common, when the lacing young cell is much smaller than the mother cell. Divided cells often stay together, forming filaments and sometimes more complex structures. Under favorable conditions, prokaryotes grow very quickly, exponentially. Having captured all the resources, the population stops growing. Further, their number may decrease due to poisoning by the products of their own metabolism. In a flowing medium, the growth rate is constant and depends on the temperature and amount of food. Therefore, there are no bacteria in the spring water filtered through the soil - they do not have time to multiply before they are taken out of the source.

Under unfavorable conditions, some bacteria form spores - resting stages covered with a dense shell. In the form of spores, they endure high temperatures, sometimes even above 100 0 C, and remain viable for many years. On the contrary, the growing, dividing cells of most prokaryotes die already at 80 0 C. However, there are also lovers of high temperature - thermophiles living in hot springs.

Microbiologists often grow bacteria on the surface of a solid medium in broth with gelatin or agar. A cell that has fallen on the surface of this nutritious jelly begins to divide and forms a colony (a spot of a certain shape and color), in which all cells are descendants of one, the original one. This is a very common technique for obtaining a clean line of microbes.

4. LIFESTYLE OF PROKARYOTES

Although micro-organisms are invisible in nature, they are found in huge numbers everywhere, especially in the soil. In fact, the entire appearance of the Earth was created by them. They can eat virtually anything, except for man-made plastics, washing powders and poisons. Everything else can be digested by all sorts of bacteria.

Microorganisms characterize by nature the three essential components of life: energy, carbon and hydrogen.

Hydrogen is needed not by itself, but as a source of electrons:

Н 2 → 2Н + + 2е ¬, so it can be replaced by other compounds and elements that easily donate electrons.

According to the source of energy, two categories of organisms are distinguished: phototrophs(using sunlight) and chymotrophs(using the energy of chemical bonds in nutrients).

Isolate according to carbon source autotrophs(CO 2) and heterotrophs(organic matter). Finally, according to the source of hydrogen (electrons), they distinguish organotrophs(consuming organic) and lithotrophs(optionally consuming stones / in Greek "lithos" - stone), and production lithospheres - the stone shell of the Earth; it can be H 2 and NH 3 itself, H 2 S, S, SO, Fe 2+ and so on.

According to this classification, terrestrial plants are photolithotrophs (light-stone-eaters), animals are chemoorganotrophs (organ-eaters). In the world of prokaryotes, the most amazing combinations occur.

Prokaryotes have another remarkable property that higher organisms lack. Although nitrogen (N 2) in Greek means "lifeless", it is necessary for life, therefore it is part of its main components - proteins and nucleic acids. But neither plants nor animals are able to assimilate atmospheric nitrogen, only some prokaryotes can do this, first reducing it to ammonia (NH 3), then turning it into nitrites (NO 2) and nitrates (NO 3). Before the advent of the chemical industry, we all lived off bacteria. This process takes place in an oxygen-free environment, so nitrogen-binding microorganisms have developed special devices to protect it from oxygen.

5. MAIN GROUPS OF PROKARYOTES

5.1. Bacteria are phototrophs

Many bacteria use light as a source of energy. All of them are colored red, orange, green or blue-green; because in order for light to do any work, it must be absorbed by the dye - pigment. Bacteria have a variety of chlorophylls and carotenoids.

Purple sulfur bacteria obtain hydrogen (electrons) from hydrogen sulfide (H 2 S), oxidizing it to sulfur and sulfates. Purple non-sulfur bacteria obtain it from dissolved organic matter.

Terrestrial bacteria can also assimilate H 2 S, molecular hydrogen and organics. Most of them can bind molecular nitrogen. They live, most often, in reservoirs on the surface of silt, some in hot springs.

A feature of bacterial photosynthesis is that free oxygen (O 2) is released during it. Such photosynthesis is called anoxygenic (oxygen-free).

Solar energy is used in a completely different way. cyanobacteria(they were inaccurately called blue-green algae). They split water and use hydrogen, and molecular oxygen is released into the atmosphere. It is believed that it was cyanobacteria with their oxygenic photosynthesis that made the atmosphere of our planet oxygen.

Cyanobacteria resistant to domestic and industrial pollution, cause "flowering" and spoilage in reservoirs, lakes, reservoirs. They can also live on coastal rocks and rocks, in mountains and deserts (they have enough dew), in hot springs.

But the troubles sometimes caused by cyanobacteria can be "forgiveable", and not only because they once made the Earth's atmosphere suitable for our breathing, releasing free oxygen.

These organisms actively fix atmospheric nitrogen, ensuring the yield of rice fields and the productivity of all other water bodies.

5.2. Bacteria are chemoautotrophs

Many bacteria obtain energy using inorganic substances: ammonia, nitrites, sulfur compounds, ferrous iron and other metal ions. Their source of carbon is carbon dioxide. These include bacteria that convert ammonia to nitrite - to nitrate. Other bacteria get energy for their growth by oxidizing sulfur compounds:

H 2 S → S → SO 3 2- → SO 4 2-

Since sulfur and hydrogen sulfide are often found in hot volcanic springs, these bacteria are common there. The metallurgists of antiquity, including those in Russia, highly valued the iron swamp ores deposited in the swamps. Of these, on charcoal, high-quality, purest iron was obtained. These ores create bacteria by oxidizing ferrous iron to ferric:

Fe 2+ → Fe 3+.

Some of the iron bacteria can also oxidize sulfur, processing soluble sulfates not only of iron sulfides, but also of other metals. Now such bacteria help metallurgists by leaching zinc, antimony, nickel, manganese, molybdenum and uranium from poor ores. The easiest way is to pass water with bacteria through a thick layer of crushed rock and collect the resulting water with sulfates of the corresponding metals. All other methods here are not economically viable.

5.3 Bacteria - organotrophs

Now let's move on to bacteria that consume organic matter. Back in the last century, the great French chemist and microbiologist L. Pasteur realized that without microorganisms, decay and fermentation converting organic matter into inorganic compounds NH3, H2S, CO2, H2O, life on Earth would become impossible. It is they who close the cycle of biogenic substances on our planet, supplying green plants - phytotrophs with the necessary "raw materials". "Too tough" for microorganisms are only man-made plastics, washing powders and poisons. Therefore, they accumulate in the environment around us and are already beginning to threaten the existence of the person himself.

Of the microorganisms - organotrophs, most often, people use in their practice bacteria that use the fermentation reaction as an energy source. These processes take place without the participation of oxygen; microorganisms that do not need H2O are called anaerobes.

There are obligatory, obligate anaerobes, for which free oxygen is a deadly poison; and optional, facultative, which easily pass from fermentation to oxygen respiration.

Lactic acid fermentation bacteria obtain energy by converting carbohydrates into lactic acid. This reaction also occurs in the muscles, during very hard work, when the blood does not have time to deliver oxygen. But in our organisms, it cannot go on for a long time - the resulting lactic acid, which physiologists expressively call "fatigue toxin," tire the muscle. Lactic acid bacteria turn milk into curdled milk, kefir and koumiss. They also form sour dough, different types of cheese, sauerkraut and cucumbers, silage.

Other bacteria during fermentation secrete other organic acids: propionic, formic, acetic, succinic, and other compounds. Some of them are used in the chemical industry.

Let's move on to prokaryotes, which have adapted to life on the integument and in the intestines of animals. Among them are useful for their owners. Cows, sheep and all ruminants contain in their complex stomachs a huge amount of bacteria that break down fiber (cellulose). Other intestinal bacteria supply vitamins to hosts. Among them there are simply “freeloaders” who do not bring direct benefit, but are not indifferent to the owners.

A person is no exception, on our skin acquires quite a few bacteria that consume organic substances of sweat. We wash them off periodically, but if these bacteria disappear all, for example, with the abuse of antibiotics, the vacant place will be occupied by yeast-like fungi that can cause skin diseases.

But there are incomparably more bacteria in the contents of our intestines. Human feces are 30% by mass composed of bacteria. Basically, these are strict obligate anaerobes from the genus Bactericides. There are much fewer facultative anaerobes that can breed in an oxygen atmosphere. Of these, Escherichia coli is the most famous. E. coli is easy to grow in the laboratory. This is the most studied bacterium, because for many decades it has been a favorite object of molecular biologists and genetic engineers.

These are bacteria that cause disease. The dangerous disease dysentery is widespread. The dysentery bacillus, multiplying in the intestines, causes its dangerous disorder ("bloody diarrhea"). Close pathogens cause salmonellosis and typhoid fever. All of them are called "diseases of dirty hands", but they can also be contracted through flies, contaminated food and water. Cholera is even more dangerous, it is caused by one of the types of vibrios - a facultative anaerobe that spreads with sewage. Its cells secrete a dangerous poison - a toxin, from which the cells of the intestinal mucosa are destroyed, the body loses a lot of water, and death can occur from dehydration.

Many bacteria infect the respiratory tract, as a result of which a person develops a sore throat. It is similar in symptoms, but incomparably more dangerous is diphtheria, caused by a rod of a club-shaped peculiar shape. It affects the cavity of the pharynx and tonsils. The diphtheria bacillus is dangerous not in itself, but only those of its varieties that contain a “tamed” virus - a “freeloader”. This virus produces a toxin that blocks protein synthesis in eukaryotic cells, including heart muscle, nerves, and kidneys. Diphtheria is especially dangerous for children. Various forms of pneumonia (pneumonia) caused by pneumococci are widespread.

Even at the beginning of the century, the word "tuberculosis" was terrifying, as AIDS is now. At that time, this disease, which usually affects the lungs, was incurable. But it can also affect other organs (bone tuberculosis). It is called the so-called wand Koch”, named after R. Koch, the great German microbiologist who described it. Koch's wand belongs to microbacteria. The causative agent of leprosy is close to it - a severe and intractable disease.

Other microbacteria live in the soil, some of them can absorb substances such as oil, paraffin, naphthalene. Tuberculosis is now curable, but is still considered a serious disease.

From time immemorial, the plague has been the scourge of mankind, from which entire cities died out in the Middle Ages. This disease is caused by the plague bacillus. Plague is actually a disease of rodents. From them to humans, it is carried by fleas. Even now, despite vaccinations and drugs, plague is difficult to cure. It is easier to prevent her outbursts.

Corkscrew-shaped microorganisms - spirochetes - can also be pathogens of dangerous diseases; relapsing fever, infectious jaundice, syphilis.

Microorganisms are obligate, strict anaerobes. These include pathogens of the most dangerous diseases: gas gangrene, tetanus, botulism. The first two people get sick when the earth gets into the wounds. In such cases, urgently need to be vaccinated. The botulinum bacterium develops in meat and fish products and canned beans rich in protein. It releases a deadly toxin - botulinum, which causes respiratory paralysis. It used to be called sausage poison.

6. BLUE-GREEN ALGAE

Blue-green algae (cyanes) are the most ancient (originated over 3 billion years ago) aquatic or less often soil autotrophic organisms. Cells have thick numerous walls (consist of polysaccharides, pectins and cellulose), often dressed in a mucous membrane. Their prokaryotic cells are structurally similar to bacteria. Photosynthesis is carried out on membranes freely lying in the cytoplasm, containing chlorophyll and other pigments.

Many species of blue-green algae have nitrogen-filled vacuoles. These vacuoles regulate the buoyancy of the cell and allow it to float in the water column. Usually, blue-green algae reproduce by dividing the cells in two, colonial or filamentous - by the decay of colonies or filaments. Under unfavorable conditions, spores may form.

Blue-green algae are widely distributed in the biosphere, but the bulk of species inhabit freshwater reservoirs, some species live in the seas and on land. Others live in places of pollution with organic substances, eating mycotrophically. They are able to purify water by mineralizing decay products.

Some blue-green algae are capable of nitrogen fixation. Blue-green algae are found as symbionts in many lichens. Cyanei are the first to develop the following habitats - volcanic islands, lava flows.

CONCLUSION

We have considered almost a hundredth of the pathogenic bacteria that cause disease only in humans. But animals and plants also suffer from bacteria.

In modern medicine, two main ways of treating and preventing such diseases have been developed.

The first of these is timely vaccinations and vaccines.

The second path is a great achievement of medicine - antibiotics, the first of which appeared during the Second World War and immediately after it.

In conclusion, summarizing all of the above, prokaryotes can be characterized using the following table:

Table 1

General characteristics of prokaryotes

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which have a core. Almost all organisms are eukaryotes, except bacteria (viruses belong to a separate category that not all biologists distinguish as a category of living beings). The eukaryotes are plants, animals, mushrooms and such kind of living organisms as slime molds. Eukaryotes are divided into unicellular organisms and multicellular, but the principle of cell structure is the same for all of them.

It is believed that the first eukaryotes appeared about 2 billion years ago and evolved largely due to symbiogenesis- the interaction of eukaryotic cells and the bacteria that these cells absorbed, being capable of phagocytosis.

eukaryotic cells have a very large size, especially compared to prokaryotes. There are about ten organelles in a eukaryotic cell, most of which are separated by membranes from the cytoplasm, which is not the case in prokaryotes. Eukaryotes also have a nucleus, which we have already talked about. This is the part of the cell that is separated from the cytoplasm by a double membrane. It is in this part of the cell that the DNA contained in the chromosomes is located. Cells are usually mononuclear, but sometimes multinucleated cells are found.

eukaryotic kingdoms.

There are several options for dividing eukaryotes. Initially, all living organisms were divided only into plants and animals. Subsequently, the kingdom of mushrooms was identified, which differ significantly from both the first and the second. Even later, slime molds began to be isolated.

slime molds is a polyphyletic group of organisms, which some refer to the simplest, but the final classification of these organisms is not fully classified. At one of the stages of development, these organisms have a plasmodic form - this is a mucous substance that does not have clear hard covers. In general, slime molds look like one multinucleated cell, which is visible to the naked eye.

Sporulation is related to slime mold fungi, which germinate with zoospores, from which plasmodium subsequently develops.

Slime molds are heterotrophs able to eat visually, that is, to absorb nutrients directly through the membrane, or by endocytosis - to take vesicles with nutrients inside. Slime molds include acrasia, myxomycetes, labyrinthulae and plasmodiophores.

Differences between prokaryotes and eukaryotes.

The main difference prokaryotes and eukaryotes is that prokaryotes do not have a well-formed nucleus separated by a membrane from the cytoplasm. In prokaryotes, circular DNA is located in the cytoplasm, and the place where the DNA is located is called the nucleoid.

Additional eukaryotic differences.

1. Of the organelles, prokaryotes have only ribosomes 70S (small), and eukaryotes have not only large 80S ribosomes, but also many other organelles.
2. Since prokaryotes do not have a nucleus, they divide by dividing in two - not with the help of meiosis/mitosis.
3. Eukaryotes have histones that bacteria do not have. Eukaryotic chromatin contains 1/3 DNA and 2/3 protein, in prokaryotes the opposite is true.
4. A eukaryotic cell is 1000 times larger in volume and 10 times larger in diameter than a prokaryotic cell.

Within this superkingdom, plants are divided into the kingdom of fungi and the kingdom of plants.

Fungi can enter into symbiotic relationships with other organisms, such as algae or cyanobacteria, to form lichens. They can also enter into symbiosis with higher plants, enveloping and penetrating the roots of plants with their hyphae and forming structures (root + fungus), called mycorrhiza. Such a symbiosis with plants provides the latter with a need for phosphates. For example, 80% of land plants, including many agricultural plants, form a symbiosis with the fungus Glornus versiforme, which lives on their roots and makes it easier for them to take up phosphate and mineral nutrients from the soil.

Among the organisms of this kingdom, there are both unicellular (microscopic), or lower, and multicellular (higher) fungi.

Mushrooms are classified into departments: True mushrooms, Oomycetes and Lichens.

Among the True mushrooms, there are classes of Chytridia fungi, Zygomycetes, Ascomycetes (Marsupial fungi), Basidiomycetes and Imperfect fungi (Deuteromycetes).

Ascomycetes are the most numerous group of fungi (more than 30,000 species), differing among themselves primarily in size. There are both unicellular and multicellular forms. Their body is represented by haploid mycelium. They form asci (bags) containing ascospores, which is a characteristic feature of these fungi. Among the mushrooms of this group, the most famous are yeast (beer, wine, kefir and others). For example, the yeast Saccharomices cerevisiae affects the fermentation of glucose (CgH^Og). One molecule of glucose produces two molecules of ethyl alcohol during this enzymatic process.

Basidiomycetes are higher fungi. They are characterized by large sizes, which can reach even up to half a meter. Their body also consists of mycelium (mycelium), but multicellular, forming mushrooms. The protoplast of fungal cells contains not only nuclei, but also mitochondria, ribosomes, the Golgi apparatus, and even glycogen as a reserve substance. The hyphae intertwine, forming fruiting bodies, which in everyday life are called mushrooms, consisting of a stem and a cap.

These fungi reproduce both vegetatively and asexually, as well as sexually. The most famous basidiomycetes are cap mushrooms, among which there are both edible and poisonous.

Oomycetes are mainly aquatic and soil fungi. Among these fungi, species from the genus Phytophtora are very well known, which cause diseases of potatoes, tomatoes and other nightshades.

Mushrooms play a significant role in nature. In particular, they are destructive organisms. Being part of many ecological systems, they are responsible for the destruction of organic material of plant origin, since they produce enzymes that act on cellulose, lignin and other substances of plant cells. They are widely used in the cheese industry for the production of many popular types of cheese. It should be noted that Neurospora crassa plays an outstanding role as an experimental object in the knowledge of many metabolic pathways.

Lichens are complex organisms formed as a result of symbiosis between fungi, green algae, or cyanobacteria, and Azotobacter (Fig. 4). Consequently, a lichen is a combined organism, i.e., a fungus + algae + Azotobacter, the existence of which is ensured by the fact that fungal hyphae are responsible for the absorption of water and minerals, algae for photosynthesis, and Azotobacter for fixing atmospheric nitrogen. Lichens are inhabitants of all botanical and geographical zones. They reproduce vegetatively, asexually and sexually.

The value of lichens in nature is great. Due to their high sensitivity to environmental pollutants, lichens are used as indicators of the purity of the atmosphere. In the north, they are the main food for deer. They are also used in pharmacy and perfumery.

Mushrooms are of ancient origin. Their fossil remains are noted in the Silurian and Devonian. Some botanists suggest that they are descended from green algae that have lost chlorophyll. The more common view is that fungi evolved from flagellates (protozoa).

Fossil remains of lichens have also been found in the Devonian, which determines their age at about 400 million years. It is believed that the formation of lichens was the first case of establishing a symbiotic relationship between organisms. This provided the possibility of their wide distribution in different ecological niches.

Plant Kingdom (Plantae or Vegetabilia). This kingdom is represented by organisms whose cells have dense cell walls and which are capable of photosynthesis. Plants of this kingdom are classified into three sub-kingdoms, namely: purple (Phycobionta), true algae (Phycobionta) and higher plants (Embryophyta).

The body of purple and real algae is not divided into tissues and organs. For this reason, they are often referred to as lower or thallus plants. On the contrary, the rest of the plants are known as higher plants, because they are characterized by the presence of different tissues and the division of the body into organs. These plants are adapted to life in terrestrial conditions.

Subkingdom of Bagryanka (Rhodophyta). The plants of this subkingdom are multicellular organisms (Fig. 5). The body of the purple is represented by a thallus. There are about 4,000 types of crimson, among which the most famous are porphyry, non-malion, corallines and others. Their crimson color depends on the content of chlorophyll, carotenoids, red phycoerythrins, blue phycocyanins and other pigments in them. They are inhabitants of the great depths of the seas and oceans. They are often referred to as red algae. The Red Sea is especially rich in them.

They reproduce both asexually and sexually with alternating sexual and asexual generations.

They are of economic importance. Some species serve as raw materials from which agar-agar is extracted. In some countries they are used for livestock feed.

Crimsonworts are ancient organisms, but their origin and phylogenetic relationships between individual species remain unclear.

Subkingdom True algae (Phycobionta). Real algae are plants whose body is represented by a thallus. About 30,000 species of these organisms are known. There are both unicellular and multicellular algae. They are inhabitants mainly of freshwater reservoirs and seas, but soil algae and even snow and ice algae are found. Reproduction of unicellular algae occurs by division, multicellular forms reproduce both asexually and sexually. Once Virgil wrote - "nigilvilor algo" (there is nothing worse than algae). In our time, algae have acquired other estimates.

Algologists classify algae into several divisions.

The Department Green algae (Chlorophyta). This section is represented by mobile and immobile unicellular and multicellular organisms, which have a rather thick cell wall and are shaped like filaments, tubules (Fig. 6). Some species form mobile and immobile colonies. There are over 13,000 species of these algae, most of which are inhabitants of fresh water. But marine forms are also known.

Unicellular and multicellular green algae are capable of photosynthesis, because they contain chloroplasts, in which chlorophyll is concentrated and from the presence of which they have a green color. They also have xanthophylls and carotenes.

Typical representatives of unicellular green algae are chlamydomonas (from the genus Chlamidomonas), living in puddles and other small fresh water bodies, and chlorella from the genus of the same name (Chlorella), which lives in fresh and salt waters, on the surface of damp earth, on the bark of trees. Chlorella has exceptional photosynthetic activity, being able to capture and use 10-12% of light energy. Contains a number of valuable proteins, vitamins B, C and K.

An example of multicellular green algae is the pond dweller Volvox. Forming a colony, this organism consists of 500-60,000 cells, each of which is equipped with two flagella, and also contains an ocellus, a differentiated nucleus, and a chloroplast. A thick gelatinous membrane surrounds each cell and separates it from neighboring cells. If one cell in a colony dies, the rest continue to live. The location of the cells in the colony ensures the movement of this organism.

They reproduce by division or the formation of mobile zoospores, which are separated from the mother's organism, attached to some substrate, and then develop into a new organism. Spirogyra has a sexual process in the form of conjugation.

The economic importance of these algae is small, except that due to the rich content of proteins and vitamins, chlorella is used in animal feed. As a component of phytoplankton, it serves as food for fish.

It is assumed that green algae arose as a result of aromorphoses, which turned out to be the formation of a nucleus, the appearance of multicellularity and the sexual process. It is also assumed that they gave rise to primitive land plants, which became the ancestral forms of bryophytes.

The Department diatoms algae, or diatoms (Chrysophyta) is represented mainly by multicellular organisms, and sometimes even by colonial forms (Fig. 7). There are also unicellular forms. 5700 species are known. They are characterized by a clear differentiation of the body into the cytoplasm and nucleus. The cell wall is "impregnated" with silica, as a result of which it is called the shell. They are inhabitants of fresh water bodies, seas and oceans and are part of phytoplankton.

In the cells of these algae, there are chloroplasts in the form of grains or plates, which are colored in different colors due to the content of different pigments (carotene, xanthophyll and its variant diatomine). For this reason, diatoms are often referred to as golden brown.

Reproduction occurs by cell division in half. Some species have sexual reproduction. Diatoms are diploid organisms.

Bedding of dead diatoms gave rise to diatomite, which consists of 50-80% of their shells and which is used as absorbers in chemistry and the food industry.

The value of diatoms in nature is very large. They occupy an exceptionally important place in the cycle of substances, being the main food for fish. Their nutritional value is very high.

Evolutionarily, diatoms are closest to green algae, but their origin is unclear.

The Department Brown algae (Phaeophyta). These algae are multicellular organisms. Each cell contains only one nucleus. In size, they are the largest (longest) algae, reaching several tens of meters in length (Fig. 8). About 900 species are known. They are inhabitants of the seas and oceans, including the northern ones. Their pigmentation is determined by the fact that they contain chloroplasts, colored brown due to the content of chlorophyll, as well as brown pigments (carotene, xanthophyll and fucoxanthin).

The most famous are algae from the genera Laminaria and Fucus.

They reproduce vegetatively, asexually and sexually. Vegetative reproduction occurs by parts of the thallus, asexual (spore) - with the help of haploid spores developing into a gametophyte, sexual - by isogamy, heterogamy or oogashi. The alternation of haploid and diploid generations is characteristic. Sex cells are equipped with flagella.

The economic importance of these algae, especially laminaria, is very high. Iodine, potassium salts, agar-like substances used in the food industry are extracted from them. Laminaria, known as "seaweed", are used for human food. Some algae are used as fertilizer.

Brown algae are the oldest aquatic plants. It is believed that they gave rise to fern-like plants.

To conclude this summary of algae data, it should be noted that, in general, algae are important in many ecological systems. In fact, they are the main source of organic matter in water bodies. It is estimated that algae are responsible for the annual synthesis of organic matter in the World Ocean in the amount of 550 billion tons, which is a significant part of the productivity of the entire biosphere. Further, they play a very significant role in enriching the atmosphere with oxygen. Finally, algae are involved in the self-purification of water bodies, in soil formation.

Subkingdom Higher plants (Embryophyta or Embryobionta). The plants that make up this sub-kingdom are often called deciduous, since their body is divided into a stem, leaf and root. In addition, they are also called germline, because they contain the germ. Finally, they are called vascular plants (except for bryophytes), since the organs of their sporophytes contain vessels and tracheids.

Higher plants in the course of historical development have adapted to life in terrestrial conditions. These plants have alternating sexual (gametophyte) and asexual (sporophyte) generations. The gametophyte produces gametes and protects the embryo, while the sporophyte produces spores that provide the next generation of the gametophyte. In higher plants, the diploid sporophyte dominates, which determines the appearance of the plant.

In the sub-kingdom Higher plants, higher spore and higher seed plants are distinguished. Higher spores are characterized by a separation of sexual and asexual reproduction. In the first case, reproduction occurs by unicellular spores formed in the sporangia of sporophytes, in the second - by gametes formed in the genital organs of gametophytes. Higher seed plants are characterized by the presence of a multicellular formation - a seed that is formed in the process of reproduction and gives seed plants the most important evolutionary advantage over spore ones.

Subkingdom Higher plants are classified into several departments. In particular, higher spore plants are classified into divisions Rhyniophyta (Rhyniophyta) and Zosterophyllophytes (Zostrophyllophyta), the organisms of which are completely extinct, as well as the currently existing divisions Bryophyta (Bryophyta), Lycopodiophyta (Lycopodiophyta), Psilotoid (Psilotophyta), Horsetail (Eguisetophyta ), Ferns (Polypodiophyta). Higher seed plants are classified into departments Gymnosperms (Gymnospermae) and Angiosperms, or Flowering (Angiospermae, or Magnoliophyta). Gymnosperms and Angiosperms are seed plants, while all the rest are higher spore plants. In some of the higher spores, all spores are the same (equisporous plants), and in some the spores are of different sizes (disspore plants).

Of the plants of modern divisions, only some of them will be considered below.

The Department Bryophytes(Bryophyta). This department is represented by undersized, perennial plants. In some of them, the body is represented by a thallus, but in most of them it is divided into a stem and leaves (Fig. 9). There are about 25,000 species of mosses. They are inhabitants of damp places in all geographical zones. They are attached to the soil with the help of hair-like outgrowths called rhizoids. Through these structures, they carry out soil nutrition. The most famous representatives of this type are cuckoo flax, diverse marchantia, mosses of the sphagnum genus (300 species).

In the development of mosses, the alternation of sexual (gametophyte) and asexual (sporophyte) generations is characteristic. On plants of the sexual generation, spores of different sizes are formed. After fertilization of the female germ cells by the male, a sporophyte (sporangium with spores) develops, the cells of which have a diploid set of chromosomes. Spores formed as a result of meiosis in sporangia have a haploid set of chromosomes. Spilling out on the soil, the spores germinate, giving rise to a plant, a gametophyte, which has a haploid set of chromosomes in cells multiplying by mitosis. The haploid gametophyte dominates the developmental cycle. On the gametophyte, germ cells are again formed, and the process is repeated. A specific feature of these plants is not only the dominance of the haploid gametophyte, but also that the gametophyte (sexual generation) and the sporophyte (asexual generation) are one plant.

The importance of mosses in nature lies in the fact that, being in ecosystems, they affect the habitat of many species of other plants, as well as animals. Intensive reproduction of mosses contributes to the deterioration of the soil. Dying off, sphagnum mosses "peat" and form peat deposits. Some species are used in the medical industry.

It is believed that the plants of this group were among the first terrestrial plants and grew widely as early as 450-500 million years ago, and that their evolution consisted in the regressive development of the sporophyte. It is believed that mosses are a blind evolutionary branch.

The Department Ferns(Palypodiophyta). Within this department, herbaceous plants are classified, which also live in damp places (Fig. 10). Some Ferns living in the tropics are represented by tree forms, some of which reach 25 meters in height. There are more than 10,000 species of these plants. Ferns are typical representatives of ferns.

For ferns, the alternation of sexual and asexual generations is also characteristic, however, unlike bryophytes, in organisms belonging to this department, the sporophyte is predominant, which is characterized by diploidy. The sporophyte has the main organs - the stem, leaves, root. On the contrary, the gametophyte is characterized by a very small size, representing a small plate attached to the soil with the help of rhizoids.

For ferns, a complex development cycle is characteristic. The cycle begins with the development of the isospores of the gametophyte (growth), on which the reproductive organs are formed in the form of antheridia and archegonia. In the latter, germ cells develop. After their fertilization, a sporophyte is formed from the zygote, on which spores are formed, giving rise to the gametophyte. Most ferns are represented by heterosporous plants.

The importance of ferns in nature is great, since they are part of many ecosystems. The economic importance of modern ferns is small, except for the fact that plants of certain species serve as medicinal raw materials.

Ferns are classified into 7 divisions, most of which are represented by extinct species.

Ferns are the most ancient spore plants. They were already in the Devonian, and in the Carboniferous they formed forests of plants, the height of which reached up to 30 m. The remains of these plants took part in the formation of coal.

The Department Gymnosperms(Gymnospermae). Plants of this division produce seeds, which are, in essence, ready-made embryos of future plants. The main organs of the seed are the germinal root, germinal stalk, germ layers. However, in gymnosperms, the seed is not covered with carpels. For this reason, they are called gymnosperms.

Gymnosperms are represented by trees, shrubs and vines. The number of species is about 700. Distributed throughout the globe. In the northern hemisphere, they occupy vast areas, forming coniferous forests.

Gymnosperms are characterized by an alternation of generations associated with a change in the haploid and diploid states, but they have a decrease in the gametophyte. Juniper, cycad, thuja, spruce, pine, larch are sporophytes. Like all seed plants, gymnosperms are heterosporous. The reproductive organs are female and male cones, which are formed on the same tree and in which the gametophyte is located.

Seed formation is the first stage in the development of the sporophyte. The female cones are built from large scales called megasporophylls, each of which bears two megasporangia on the inner surface, and each megasporangium in turn contains a megaspore that develops into a multicellular gametophyte containing two or three archegonia. Each archegonium consists of a single large egg and several small elongated cells. Megasporangium is covered with the so-called integument. A megasporangium with an integument is called an ovule.

Male cones bear on the inner surface of their scales (on microsporophylls) two microsporangia containing microspores, each of which develops into haploid pollen. Pollen granules (grains) make up the male gametophyte.

Megasporophylls and microsporophylls are collected into mega- and microstrobills (respectively) on a shortened spore-bearing shoot, which is a stem with spore-bearing leaves.

When the pollen hits the female cones, it passes into the ovule, with each pollen granule developing into a stamen tube and two sperm nuclei, and when the stamen tube enters the egg, the sperm nucleus fuses with the egg nucleus. This is fertilization. The diploid zygote becomes a diploid embryo. Over time, the outer integument of the ovule turns into a seed coat, and endosperm is formed from the remnants of the megasporangium. Therefore, the ovule turns into a seed. After maturation, the seeds from the cones fall out.

Gymnosperms are a very ancient group of higher plants. Appearing in the Devonian (about 350 million years ago), the gymnosperms at the end of the Paleozoic - the beginning of the Mesozoic took the place of ferns, since they turned out to be more adapted to life in terrestrial conditions. One of their hypotheses is that the gymnosperms originated from the most ancient ferns.

The Department Angiosperms, or Flowering(Angiospermae, or Magnoliophyta). Plants of this division are found almost everywhere. They account for 250,000-300,000 species, that is, almost two-thirds of the species of the plant kingdom. They are currently the most prosperous group of plants.

Within this department, monocotyledonous and dicotyledonous plants are distinguished, which are both herbaceous and shrubby species, and trees. Typical representatives of this department are rye, wheat, rose, birch, aspen and others. There are monocots and dicots angiosperms.

These plants are also characterized by alternation of generations, but they have experienced a significant decrease in the gametophyte.

A remarkable feature of these plants is the presence of a flower, which is a modified shoot and is a derivative of the sporophyte (Fig. 11). It is for this reason that plants that form flowers are called flowering plants. As a rule, the flowers are bisexual, but sometimes they are dioecious. In a flower, a pistil and stamens are distinguished, which are its main parts. Seeds develop at the bottom of the pistil (ovary). For this reason, these plants are called angiosperms. The lower part of the pistil is represented by an ovary, a narrow style and a stigma. As for the stamens, each of them consists of a filament and an anther.

In bisexual plants, which are the majority among angiosperms, flowers have both pistils and stamens, i.e., these plants have pistillate (female) and staminate (male) flowers. But in many species, some flowers have only pistils, on the other - only stamens. Such plants are called dioecious. Pollination is the result of the transfer of pollen from the stamens to the stigma of the pistil.

The general scheme of reproduction of angiosperms in fig. 12.

The female gametophyte of flowering plants consists of 8 cells of the embryo sac, one of which is an egg. This microscopic structure develops from a single megaspore. The male gametophyte develops from a microspore, or pollen granule, located in the microsporangium of the anther. Once on the stigma of the pistil, the pollen granule, as a result of division, gives rise to a generative cell and a cell that develops into a pollen tube. Next, the pollen tube grows into the cavity of the ovary. The nucleus of the generative cell tube migrates to the bottom of the pollen tube, where the generative cell divides to produce two spermatozoa. One of these sperm fuses with the egg, forming a diploid zygote, while the second sperm fuses with the nucleus (in the center of the embryo sac, in the ovule), producing a triploid nucleus, which then develops into the endosperm. Ultimately, both structures end up in the seed, and the seed ends up in the ovary, which develops into a fruit. The latter may contain from one to several seeds. Such fertilization is called double (Fig. 13). It was discovered in 1898 by S. G. Navashin (1857-1950). The biological meaning of double fertilization is that the development of the triploid endosperm, combined with a huge number of generations, saves the plastic and energy resources of plants.

It was discovered in 1898 by S. G. Navashin (1857-1950). The biological meaning of double fertilization is that the development of the triploid endosperm, combined with a huge number of generations, saves the plastic and energy resources of plants.

The stem is a plant organ to which leaves, roots, and flowers are attached. (The structure of the stem of a woody plant is shown in Fig. 14.)

Leaves are the most important plant organ. They are characterized by a different shape and are built from several layers of cells containing a large number of chloroplasts. They serve as an organ for gas exchange between plants and the environment. Due to the presence of chlorophyll in the leaves, photosynthesis occurs, which is based on two reactions - water photolysis and COg fixation.

The root is a plant organ that absorbs water and minerals from the soil and conducts them to the stem. In angiosperms, as well as gymnosperms, water and nutrients from the soil are adsorbed by root hairs and carried into the xylem as a result of osmotic pressure in the root system, the action of capillaries, negative pressure in the xylem, sometimes reaching up to 100 bar in some tree forms, and transpiration, t i.e. evaporation of water from the leaves (Fig. 15).

It is very difficult to overestimate the economic importance of angiosperms, since they are extremely widely used in human life (a source of food, raw materials for industry, animal feed, etc.).

Angiosperms are the dominant plants of our planet. Therefore, the explanation of their origin has long been one of the most important tasks in the theory of evolution. Starting with C. Darwin, several hypotheses have been put forward to explain angiosperms. According to one of them, it is suggested that angiosperms originated from some gymnosperms, and monocots come from some ancient dicots. However, this and other hypotheses are not exhaustive. There are disagreements in determining the time of the appearance of angiosperms. According to the latest ideas, the main diversification of flowering plants, including the division into monocots and dicots, occurred 130-90 million years ago, and this then gave rise to changes in terrestrial ecosystems.

Issues for discussion

1. How do you understand the differences between pre-nuclear and nuclear organisms?

2. Name the sub-kingdoms of pre-nuclear organisms.

3. What do you know about archaebacteria and their properties that other pre-nuclear organisms do not have?

4. What is the role of bacteria in nature and in human life? What morphological forms of bacteria do you know?

5. List the main properties of mushrooms. How are fungi different from lichens?

6. What are the similarities and differences between plant cells and animal cells?

7. How do green algae differ from cyanobacteria?

8. Do algae have any characteristics of economic importance?

9. What properties are characteristic of higher plants?

10. What does alternation of generations mean in plants and what is its biological role?

11. Are there any differences between mossy and fern-like plants? Is there a commonality in their origin?

13. Why do angiosperms have such a name?

14. What is the meaning of the flower?

16. What is double fertilization in angiosperms?

16. What is the importance of angiosperms in human life?

17. What do you know about the origin of angiosperms?

Literature

Green N., Stout W.. Taylor D. Biology. M.: Mir. 1996. 368 pages.

Nidon K., Peterman I., Scheffel P., Washer B. Plants and animals. M.: Mir. 1991. 260 pages.

Starostin B. A. Botany. In book. "History of Biology". M.: Science. 1975. 52-77.

Yakovlev G.P., Chelombitko V.A. Botany. M.: Higher school. 1990. 367 pages.

Rosemweig, M. L. Species Diversity in Space and Time. Cambridge University Press. 1995. 436pp.

Superkingdom Prenuclear organisms (Procaryota)

Unicellular and multicellular organisms without a separate nucleus. genetic information is concentrated in a single chromosome. the size of prokaryotes is from 0.015 to 20 cm. They appeared in the interval of 3.7-3.1 billion years. Prokaryotes are divided into two kingdoms: bacteria and cyanobiotes. their nutrition is carried out in the process of chemo- and photosynthesis.

Kingdom of bacteria

Bacteria are microscopic organisms measuring about 1-5 µm (micromicron). Unicellular bacteria can have a filamentous, rod-shaped, spiral shape. Bacteria include autotrophic and heterotrophic forms. The former create organic and inorganic substances; the latter use ready-made organic substances. Most bacteria are autotrophic. Their metabolic processes go without the use of light (chemosynthesis), or only in the light (photosynthesis). By types of metabolism, bacteria are extremely diverse. There are sulfur-forming, ferruginous-manganese, nitrogen, acetate, carbon-forming and other groups of bacteria. The role of bacteria in geological processes is great. The formation of various minerals is associated with their activity: iron ores (jespilites, ferruginous nodules), pyrite, sulfur, graphite, phosphorites, oil, gas, etc.

Reliable finds of bacteria are known from siliceous rocks, which are 6.5 billion years old. Most likely, the bacteria appeared independently in different habitats. At present, they inhabit all water basins from the littoral to the abyssal, and also live in the soil, in the air, and inside other organisms. They live in hot springs at temperatures exceeding 100 degrees Celsius and in salty waters with a sodium chloride concentration of up to 32%.

Kingdom Cyanobionta

Solitary and colonial organisms with cells without a separate nucleus. The sizes of single forms are about 10 microns, while the sizes of colonies and their metabolic products (stromatolites) are many hundreds of years. Accumulation of carbonates occurs in the body, leading to the formation of limestones. The calcareous layered formations are called stromatolites. Stromatolites differ in the form of buildings, the type of structure. They can have a reservoir, nodular, columnar shape. Oncolites, unlike stromatolites, are represented by small rounded formations up to several centimeters in diameter.

Stromatolites are the result of a symbiosis of cyanobionts and bacteria. The formation of stromatolites occurs as follows. Calcium is secreted in the mucous membrane. After the death of the organism, a carbonate crust remains, which is covered with sediments. Repeated cycles of growth of cyanobionts and bacteria lead to the formation of complex carbonate strata up to 1000 m thick. In addition to linear stromatolites, spherical oncolites and patterned in the form of irregular stars - catagraphies are formed. The shape of all structures of stromatolites depends on environmental factors and therefore they can be used to restore the physical and geographical conditions of past basins: salinity, temperature, depth, hydrodynamics. Cyanobionts took an active part in the construction of the biostrala and ….

Cyanobionts appeared about 3.5 billion years ago. Due to the presence of chlorophyll, they are the first photosynthetic organisms to produce molecular oxygen. Modern cyanobionts live in fresh and marine water bodies, mainly at a depth of up to 20 m. They tolerate pollution and sharp fluctuations in physicochemical conditions. The temperature ranges from glacial minus to almost boiling (85 degrees) in hot springs. By the absence of a nucleus, cyanobionts are close to bacteria, by the presence of chlorophyll and the ability to photosynthesize - to algae.

Superkingdom nuclear organisms (Eucaryota)

Single and multicellular organisms, subdivided into three sub-kingdoms: plants, fungi, animals. Unlike prokaryotes, they have a separate nucleus. sizes of eukaryotes, from 10 microns (single-celled) to 33 m (whale length) and 100 m (height of some conifers). Eukaryotes are the descendants of prokaryotes. They appeared at the level of 1.7-1.5 billion years (PR1). Plants, unlike animals, are capable of creating organic compounds from inorganic compounds through photosynthesis. They have different cells, assimilation processes. A form of existence that is mostly immobile (excluding passively swimming plankton).

Plant Kingdom (Phyta)

Diverse, mostly immobile unicellular and multicellular, with apical growth. All plants are characterized by photosynthesis: using the energy of light absorbed by chlorophyll, they release molecular oxygen and create organic compounds from inorganic ones. The plant cell consists of cytoplasm, which contains the nucleus, vacuoles - voids and organelles - independent intracellular formations. The hard cellulose shell of the cell is permeated with vapors, often saturated with salts and mineralized.

The plant kingdom is divided into two sub-kingdoms - lower (Thallophyta) and higher (Telomophyta). Lower plants live in water bodies. This is algae. They live at depths up to 200 m and among them there are both bottom - benthic and pelagic - planktonic. Higher plants live in terrestrial conditions at almost all latitudes. Plants are preserved in the fossil state in the form of separate parts (stem, leaves, roots, seeds), which makes it difficult to reconstruct their appearance.