So, isolated lichen symbionts settled in laboratories, in sterile test tubes and flasks with a nutrient medium. Having pure cultures of lichen partners at their disposal, scientists decided on the most daring step - the synthesis of lichen in the laboratory. The first success in this field belongs to E. Thomas, who in 1939 in Switzerland obtained from myco- and photobionts the lichen Cladonia capillary with clearly visible fruiting bodies. Unlike previous researchers, Thomas performed the synthesis under sterile conditions, which inspires confidence in his result. Unfortunately, his attempts to repeat the synthesis in 800 other experiments failed.

V. Akhmadzhyan’s favorite object of research, which brought him worldwide fame in the field of lichen synthesis, is Cladonia comb. This lichen is widespread in North America and has received the common name “British soldiers”: its bright red fruiting bodies are reminiscent of the scarlet uniforms of English soldiers during the war of the North American colonies for independence. Small lumps of the isolated mycobiont Cladonia crestata were mixed with a photobiont extracted from the same lichen. The mixture was placed on narrow mica plates, soaked in a mineral nutrient solution and fixed in closed flasks. Strictly controlled conditions of humidity, temperature and light were maintained inside the flasks. An important condition of the experiment was the minimum amount of nutrients in the medium. How did the lichen partners behave in close proximity to each other? The algae cells secreted a special substance that “glued” the fungal hyphae to them, and the hyphae immediately began to actively entwine the green cells. Groups of algal cells were held together by branching hyphae into primary scales. The next stage was the further development of thickened hyphae on top of the scales and their release of extracellular material, and as a result, the formation of the upper crustal layer. Even later, the algal layer and the core differentiated, just like in the thallus of a natural lichen. These experiments were repeated many times in Akhmadzhyan’s laboratory and each time led to the appearance of a primary lichen thallus.

In the 40s of the 20th century, the German scientist F. Tobler discovered that for the germination of xanthoria wallae spores, the addition of stimulating substances is required: extracts from tree bark, algae, plum fruits, some vitamins or other compounds. It was suggested that in nature the germination of some fungi is stimulated by substances coming from algae.

It is noteworthy that for a symbiotic relationship to occur, both partners must receive moderate or even meager nutrition, limited humidity and lighting. Optimal conditions for the existence of a fungus and algae do not stimulate their reunification. Moreover, there are cases where abundant nutrition (for example, with artificial fertilizer) led to the rapid growth of algae in the thallus, disruption of the connection between symbionts and death of the lichen.

If we examine sections of the lichen thallus under a microscope, we can see that most often the alga is simply adjacent to fungal hyphae. Sometimes the hyphae are closely pressed against the algal cells. Finally, fungal hyphae or their branches can penetrate more or less deeply into the algae. These projections are called haustoria.

Coexistence also leaves an imprint on the structure of both lichen symbionts. Thus, if free-living blue-green algae of the genera Nostoc, Scytonema and others form long, sometimes branching filaments, then in the same algae in symbiosis the filaments are either twisted into dense balls or shortened to single cells. In addition, differences in the size and arrangement of cellular structures are noted in free-living and lichenized blue-green algae. Green algae also change in a symbiotic state. This primarily concerns their reproduction. Many of the green algae, living “in freedom”, reproduce by mobile thin-walled cells - zoospores. Zoospores are usually not formed in the thallus. Instead, aplanospores appear - relatively small cells with thick walls, well adapted to dry conditions. Of the cellular structures of green photobionts, the membrane undergoes the greatest changes. It is thinner than that of the same algae “in the wild”, and has a number of biochemical differences. Very often, fat-like grains are observed inside the symbiotic cells, which disappear after the algae are removed from the thallus. Speaking about the reasons for these differences, we can assume that they are associated with some kind of chemical effect of the algae’s fungal neighbor. The mycobiont itself is also influenced by its algal partner. Dense lumps of isolated mycobionts, consisting of closely intertwined hyphae, do not at all look like lichenized fungi. The internal structure of the hyphae is also different. The cell walls of hyphae in a symbiotic state are much thinner.

So, life in symbiosis encourages the algae and the fungus to change their external appearance and internal structure.

What do cohabitants get from each other, what benefits do they derive from living together? The algae supplies the fungus, its neighbor in the lichen symbiosis, with carbohydrates obtained during the process of photosynthesis. An algae, having synthesized one or another carbohydrate, quickly and almost entirely gives it to its mushroom “companion”. The fungus receives not only carbohydrates from the algae. If the blue-green photobiont fixes atmospheric nitrogen, there is a rapid and steady outflow of the resulting ammonium to the fungal neighbor of the algae. The algae, obviously, simply gets the opportunity to spread widely throughout the Earth. According to D. Smith, “the most common algae in lichens, Trebuxia, very rarely lives outside the lichen. Inside the lichen, it is perhaps more widespread than any genus of free-living algae. The price for occupying this niche is supplying the host fungus with carbohydrates.”

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It is believed that mutualism (mutually beneficial symbiosis) of two types of living beings should form gradually, as a result of long co-evolution. However, experiments by American biologists have shown that many species of fungi and unicellular algae can form mutualistic systems almost instantly, without a previous period of mutual adaptation and without any genetic modifications. To do this, the fungus and algae must find themselves in an environment where they will be each other’s only sources of necessary substances, such as carbon dioxide and ammonium. The study confirmed the “ecological correspondence” hypothesis, according to which not all mutualistic systems existing in nature should be interpreted as the result of long-term previous coevolution.

Obligate (obligatory) mutualism is a mutually beneficial relationship between two species that cannot exist without each other. It is generally accepted that such relationships are formed gradually, during long-term coevolution and mutual adaptation, the “grinding in” of organisms to each other. Undoubtedly, in many cases this was the case (see N. Provorov, E. Dolgikh, 2006. Metabolic integration of organisms in systems of symbiosis).

Of course, not every species is able to integrate into a new environment. During introduction, a kind of sorting occurs, during which some newcomers take root in a new place, while others die. One way or another, we have to admit that an integral and interconnected community can be formed not only due to the co-evolutionary “grinding in” of species with each other over millions of years, but also due to the selection from among random migrants of species that successfully complement each other and get along well together. This idea, known as ecological fitting, has been developed by the famous American ecologist Daniel Janzen since the 1980s.

Can obligate-mutualistic systems, usually considered something like the apotheosis of coevolution, be formed according to the same scheme, that is, without any coevolution - simply due to the random correspondence of two accidentally encountered species, which, under certain conditions, turn out to be unable to live without each other? Experiments conducted by biologists from Harvard University (USA) allow us to answer this question in the affirmative.

The authors worked with the common baker's budding yeast Saccharomyces cerevisiae and the equally common unicellular algae Chlamydomonas reinhardtii. In nature, these species have not been observed in mutualistic relationships. In the laboratory, however, they formed an inextricable bond easily and quickly, without any evolution or genetic modification. To do this, it turned out to be enough to grow yeast and chlamydomonas without access to air in an environment where glucose is the only source of carbon and potassium nitrite is the only source of nitrogen.

The scheme of mutualistic relationships between yeast and Chlamydomonas is quite simple (Fig. 1). Yeast feeds on glucose and produces carbon dioxide, which is necessary for chlamydomonas for photosynthesis (chlamydomonas do not know how to use the glucose contained in the medium). Algae, for their part, reduce nitrite, converting nitrogen into a form accessible to yeast (ammonium). Thus, yeast provides carbon to Chlamydomonas, and Chlamydomonas provides nitrogen to yeast. Under such conditions, neither species can grow without the other. This is obligate mutualism.

The authors were convinced that the mutualistic system grows safely in a wide range of glucose and nitrite concentrations, although neither of the two species survives alone under these conditions. Only with a very strong decrease in the concentration of glucose or nitrite does the growth of the mixed culture stop.

If you uncork the system, that is, give it access to atmospheric CO2, you get a community in which only one of the participants (yeast) cannot live without the other, while the second participant (Chlamydomonas) no longer needs the first to survive. However, even in this case, Chlamydomonas grows better in the presence of yeast than without it (obviously, the additional CO2 released by the yeast benefits them). Thus, the system remains mutualistic, although on the algae side the mutualism is no longer obligate. Neither species displaces the other.

If you add ammonium to the medium, the situation is reversed: now the yeast can live without algae (and does not need it at all), while the algae still cannot live without yeast. This is no longer mutualism, but commensalism (freeloading on the part of algae). In this case, yeast, which reproduces faster than algae, fills the entire living space, driving Chlamydomonas to extinction. The authors suggest that the stability of such asymmetric systems (in which only one of the participants is highly dependent on the other) is determined by the ratio of reproduction rates. If a dependent species reproduces faster than an independent one, then the cohabitation of the two species can be stable; otherwise, the independent species may completely displace its partner.

The authors conducted similar experiments with other species of Chlamydomonas and ascomycete fungi. It turned out that almost all types of yeast under these conditions form obligate-mutualistic relationships with Chlamydomonas. True, the productivity (growth rate) of symbiotic complexes turns out to be different. It was not possible to determine what it depends on: the authors did not find a connection either with the tendency of yeast to oxygen respiration or oxygen-free metabolism (fermentation), or with the natural habitats of the yeast, or with the rate of reproduction, or with the degree of influence of nitrite concentration on yeast growth. Obviously, the matter is in some other characteristics of the studied species.

The unicellular alga Chlorella refused to enter into a mutualistic relationship with yeast, because it itself can feed on glucose and in a mixed culture displaces yeast. The yeast Hansenula polymorpha did not form obligate-mutualistic complexes with algae, because they themselves are able to use nitrite as a source of nitrogen. But still, the study showed that a variety of species of ascomycetes and chlamydomonas are ready to enter into a symbiotic relationship with each other, once in suitable conditions.

Of the multicellular (more precisely, filamentous hyphae-forming) ascomycetes, two classic laboratory objects were tested - Neurospora crassa and Aspergillus nidulans. Both species are able to reduce nitrite and therefore do not form obligate-mutualistic systems with Chlamydomonas. However, genetically modified strains of these fungi, deprived of the ability to utilize nitrite, entered into symbiosis with algae in the same way as yeast. As it turned out, in this case, chlamydomonas cells come into direct physical contact with fungal hyphae: under a microscope, hyphae covered with chlamydomonas are visible, like a Christmas tree (Fig. 2).

Mutualistic relationships between Chlamydomonas and yeast also apparently require the establishment of physical contacts between cells. This is evidenced by the fact that systematic shaking of a mixed culture of yeast and algae sharply slows down the growth of the symbiotic system.

Using an electron microscope, the authors discovered tight junctions formed between the cell walls of Aspergillus nidulans and Chlamydomonas reinhardtii, and the algal cell wall at the points of contact becomes thinner, possibly under the influence of enzymes secreted by the fungus.

Similar intercellular contacts are characteristic of classical fungal-algal symbiotic systems - lichens. During their evolution, ascomycetes many times entered into symbiosis with algae and cyanobacteria, forming lichens. Lichen-forming groups are scattered throughout the phylogenetic tree of ascomycetes. This means that such evolutionary events occurred repeatedly and independently in different evolutionary lineages of fungi (see F. Lutzoni et al., 2001. Major fungal lineages are derived from lichen symbiotic ancestors). Apparently, ascomycetes in general are “predisposed” (preadapted) to the formation of mutualistic complexes with unicellular algae. Experiments by American scientists may shed light on the early stages of the formation of such complexes.

However, one should not overestimate the similarity of the experimentally obtained mutualistic systems with lichens. If only because in most lichens, only the fungal component cannot live alone, while photosynthetic components (unicellular algae and cyanobacteria), as a rule, can live perfectly well without a fungus. That is, lichens are not obligate-mutualistic systems. And lack of access to atmospheric CO2 is hardly a problem that algae often have to face in nature. The main thing in the work under discussion is the demonstration of the general principle. The study showed that obligate mutualism can develop instantly, without any evolution - simply due to the fact that changing conditions make species interdependent. Of course, in order for something truly complex and highly integrated, like a lichen, to develop from such a hastily formed symbiotic complex, millions of years of coevolution are no longer necessary.

Photo of symbiosis of mushrooms with roots

A striking example of fungal symbiosis is mycorrhiza - a community of fungi and higher plants (various trees). With such “cooperation” both the tree and the mushroom benefit. Settling on the roots of a tree, the fungus performs the function of absorbing root hairs and helps the tree absorb nutrients from the soil. With this symbiosis, the fungus receives ready-made organic substances (sugars) from the tree, which are synthesized in the leaves of the plant with the help of chlorophyll.

In addition, during the symbiosis of fungi and plants, the mycelium produces substances such as antibiotics that protect the tree from various pathogenic bacteria and pathogenic fungi, as well as growth stimulants such as gibberellin. It has been noted that trees under which cap mushrooms grow practically do not get sick. In addition, the tree and the mushroom actively exchange vitamins (mainly groups B and PP).

Many cap mushrooms form symbiosis with the roots of various plant species. Moreover, it has been established that each type of tree is capable of forming mycorrhiza not with one type of fungus, but with dozens of different species.

In the photo Lichen

Another example of the symbiosis of lower fungi with organisms of other species is lichens, which are a union of fungi (mainly ascomycetes) with microscopic algae. What is the symbiosis of fungi and algae, and how does such “cooperation” occur?

Until the middle of the 19th century, it was believed that lichens were separate organisms, but in 1867, Russian botanists A. S. Famintsyn and O. V. Baranetsky established that lichens are not separate organisms, but a community of fungi and algae. Both symbionts benefit from this union. Algae, with the help of chlorophyll, synthesize organic substances (sugars), which the mycelium feeds on, and the mycelium supplies the algae with water and minerals, which it sucks from the substrate, and also protects them from drying out.

Thanks to the symbiosis of fungus and algae, lichens live in places where neither fungi nor algae can exist separately. They inhabit hot deserts, high mountains and harsh northern regions.

Lichens are even more mysterious creatures of nature than mushrooms. They change all the functions that are inherent in separately living fungi and algae. All vital processes in them proceed very slowly, they grow slowly (from 0.0004 to several mm per year), and also age slowly. These unusual creatures are distinguished by a very long life expectancy - scientists suggest that the age of one of the lichens in Antarctica exceeds 10 thousand years, and the age of the most common lichens that are found everywhere is at least 50-100 years.

Thanks to the collaboration of fungi and algae, lichens are much more resilient than mosses. They can live on substrates on which no other organism on our planet can exist. They are found on stone, metal, bones, glass and many other substrates.

Lichens still continue to amaze scientists. They contain substances that no longer exist in nature and which became known to people only thanks to lichens (some organic acids and alcohols, carbohydrates, antibiotics, etc.). The composition of lichens, formed by the symbiosis of fungi and algae, also includes tannins, pectins, amino acids, enzymes, vitamins and many other compounds. They accumulate various metals. Of the more than 300 compounds contained in lichens, at least 80 of them are found nowhere else in the living world of the Earth. Every year, scientists find in them more and more new substances that are not found in any other living organisms. Currently, more than 20 thousand species of lichens are already known, and every year scientists discover several dozen more new species of these organisms.

From this example it is clear that symbiosis is not always a simple cohabitation, and sometimes gives rise to new properties that none of the symbionts had individually.

There are a great many such symbioses in nature. With such a partnership, both symbionts win.

It has been established that the desire for unification is most developed in mushrooms.

Mushrooms also enter into symbiosis with insects. An interesting association is the connection between some types of molds and leaf-cutter ants. These ants specifically breed mushrooms in their homes. In separate chambers of the anthill, these insects create entire plantations of these mushrooms. They specially prepare the soil on this plantation: they bring in pieces of leaves, crush them, “fertilize” them with their feces and the feces of caterpillars, which they specially keep in the neighboring chambers of the anthill, and only then introduce the smallest fungal hyphae into this substrate. It has been established that ants breed only mushrooms of certain genera and species that are not found anywhere in nature except anthills (mainly fungi of the genera Fusarium and Hypomyces), and each species of ants breeds certain types of mushrooms.

Ants not only create a mushroom plantation, but also actively care for it: they fertilize, prune and weed. They cut off the emerging fruiting bodies, preventing them from developing. In addition, ants bite off the ends of fungal hyphae, as a result of which proteins accumulate at the ends of the bitten off hyphae, forming nodules resembling fruiting bodies, which the ants then feed on and feed their babies. In addition, when the hyphae are trimmed, the mycelium of the fungi begins to grow faster.

“Weeding” is as follows: if mushrooms of other species appear on the plantation, the ants immediately remove them.

It is interesting that when creating a new anthill, the future queen, after the nuptial flight, flies to a new place, begins to dig tunnels for the home of her future family, and creates a mushroom plantation in one of the chambers. She takes mushroom hyphae from an old anthill before flight, placing them in a special suboral pouch.

Termites are also bred in similar plantations. In addition to ants and termites, bark beetles, boring insects, some types of flies and wasps, and even mosquitoes are involved in “mushroom farming.”

German scientist Fritz Schaudin discovered an interesting symbiosis of our ordinary blood-sucking mosquitoes with actinomycetes yeast fungi, which help them in the process of sucking blood.

Symbiosis - This is the long-term cohabitation of organisms of two or more different species of plants or animals, when their relationships with each other are very close and usually mutually beneficial. Symbiosis provides these organisms with better nutrition. Thanks to symbiosis, it is easier for organisms to overcome the adverse effects of the environment.

In tropical countries there is a very interesting plant - myrmecodia. This is an anthill plant. It lives on the branches or trunks of other plants. The lower part of its stem is greatly expanded and looks like a large onion. The entire bulb is permeated with channels communicating with each other. Ants settle in them. These channels arise during the development of a thickened stem, and are not gnawed by ants. Consequently, the ants receive a ready-made home from the plant. But the plant also benefits from the ants living in it. The fact is that in the tropics there are Leaf-cutter ants. They cause great harm to plants. Ants of another species settle in myrmecodia and are at war with leaf-cutter ants. The residents of myrmecodia do not allow leaf cutters to reach its top and do not allow them to eat its tender leaves. Thus, the plant provides the animal with a home, and the animal protects the plant from its enemies. In addition to myrmecodia, many other plants grow in the tropics that are in collaboration with ants.

Anthill plant - myrmecody: 1 - two plants settled on one tree branch; 2 - section of the myrmecodia stem.

There are even closer forms of symbiosis between plants and animals. This is, for example, the symbiosis of unicellular algae with amoebas, sunflowers, ciliates and other protozoa. These single-celled animals harbor green algae, such as zoochlorella. For a long time, green bodies in the cells of the simplest animals were considered organelles, i.e., permanent parts of the unicellular animal itself, and only in 1871 the famous Russian botanist L. S. Tsenkovsky established that there is cohabitation of different simple organisms. Subsequently, this phenomenon was called symbiosis.

Zoochlorella, living in the body of the simplest animal amoeba, is better protected from adverse external influences. The body of the amoeba is transparent, so the process of photosynthesis occurs normally in the algae. The animal receives soluble products of photosynthesis (mainly carbohydrates - sugar) from the algae and feeds on them. In addition, during photosynthesis, the algae releases oxygen, and the animal uses it for respiration. In turn, the animal provides the algae with the nitrogenous compounds necessary for its nutrition. The mutual benefit for animal and plant from symbiosis is obvious.

Algae in the body of animals: 1 - amoeba, a - zoochlorella algae, b - amoeba core, c - contractile vacuole of amoeba; 2 - paulinella rhizome, a - core of the rhizome, b - green algae, c - pseudopodia of the rhizome.

Not only the simplest unicellular animals, but also some multicellular animals have adapted to symbiosis with algae. Algae are found in the cells of hydras, sponges, worms, echinoderms and mollusks. For some animals, symbiosis with algae has become so necessary that their An organism cannot develop normally if there are no algae in its cells.

Above - symbiosis in the life of lower plants. Lichens: 1 - cladonia; 2 - parmelia; 3 - ksaiatorium; 4 - chains and spherical cells of algae, visible through a microscope in a section of the thallus of various lichens. Below - plants from the orchid family: 1 - epiphytic tropical orchids with aerial (a) and ribbon-like (b) roots; 2 - terrestrial orchid of the temperate zone - Lady's slipper.

Symbiosis is especially interesting when both participants are plants. Perhaps the most striking example of the symbiosis of two plant organisms is lichen. Lichen is perceived by everyone as a single organism. In fact, it consists of a mushroom and algae. It is based on intertwined hyphae (threads) of the fungus. On the surface of the lichen, these hyphae are tightly intertwined, and algae nest among the hyphae in the loose layer below the surface. Most often these are unicellular green algae. Less common are lichens with multicellular blue-green algae. Algae cells are entwined with fungal hyphae. Sometimes suckers form on the hyphae and penetrate into the algae cells. Cohabitation is beneficial for both the fungus and the algae. The fungus provides water with dissolved mineral salts to the algae, and receives from the algae organic compounds produced by it during photosynthesis, mainly carbohydrates.

Symbiosis helps lichens so well in the struggle for existence that they are able to settle on sandy soils, on bare, barren rocks, on glass, on sheet iron, that is, where no other plant can exist. Lichens are found in the Far North, in high mountains, in deserts - as long as there is light: without light, the algae in the lichen cannot absorb carbon dioxide and dies. The fungus and algae live so closely together in the lichen, they are so much a single organism that they even reproduce most often together.

For a long time, lichens were mistaken for ordinary plants and classified as mosses. The green cells in the lichen were mistaken for the chlorophyll grains of a green plant. Only in 1867 was this view shaken by the research of Russian scientists A. S. Famintsyn and O. V. Baranetsky. They were able to isolate green cells from the xanthorium lichen and establish that they can not only live outside the body of the lichen, but also reproduce by division and spores. Consequently, green lichen cells are independent algae.

Everyone knows, for example, that boletuses should be looked for where aspen trees grow, and boletuses - in birch forests. It turns out that cap mushrooms grow near certain trees for a reason. Those “mushrooms” that we collect in the forest are only their fruiting bodies. The body of the fungus itself - the mycelium, or mycelium - lives underground and consists of thread-like hyphae that penetrate the soil (see article “Mushrooms”). From the surface of the soil they stretch to the tips of tree roots. Under a microscope you can see how the hyphae, like felt, entwine the tip of the root. The symbiosis of a fungus with the roots of higher plants is called mycorrhiza(translated from Greek - “mushroom root”).

The vast majority of trees in our latitudes and a lot of herbaceous plants (including wheat) form mycorrhiza with fungi. Scientists have found that the normal growth of many trees is impossible without the participation of the fungus, although there are trees that can develop without them, for example, birch and linden. The symbiosis of a fungus with a higher plant existed at the dawn of terrestrial flora. The first higher plants - psilotaceae - already had underground organs closely associated with fungal hyphae. Most often, the fungus only entwines the root with its hyphae and forms a sheath, like the outer tissue of the root. Less common are forms of symbiosis, when the fungus settles in the root cells themselves. This symbiosis is especially pronounced in orchids, which generally cannot develop without the participation of the fungus.

It can be assumed that the fungus uses carbohydrates (sugar) secreted by the roots for its nutrition, and the higher plant receives from the fungus the products of decomposition of nitrogenous organic substances in the soil. The tree root itself cannot obtain these products. It is also assumed that mushrooms produce vitamin-like substances that enhance the growth of higher plants. In addition, there is no doubt that the mushroom cover, which envelops the root of a tree and has numerous branches in the soil, greatly increases the surface of the root system that absorbs water, which is very important in the life of the plant.

The symbiosis of a fungus and a higher plant should be taken into account in many practical activities. So, for example, when planting forests, when laying shelterbelts, it is imperative to “infect” the soil with fungi that enter into symbiosis with the tree species that is planted.

Of great practical importance is the symbiosis of nitrogen-assimilating bacteria with higher plants from the legume family (beans, peas, beans, alfalfa and many others). Thickenings usually appear on the roots of a legume plant - nodules, the cells of which contain bacteria that enrich the plant, and then the soil, with nitrogen (see article “How a green plant works and feeds”).

All living organisms on the planet are divided into kingdoms. The classification was based on the presence of a nucleus. There is a kingdom of prokaryotes that do not have a nucleus. These include bacteria and blue-green algae (cyanea). The kingdom of eukaryotes includes those organisms that have a nucleus: fungi, plants and animals. Despite the fact that bacteria, fungi, plants (algae and higher), animals constitute separate kingdoms, there are also common features between them.

Bacteria and cyanides are classified as prokaryotes. Their main differences are:

• lack of a clearly defined core;
• absence of membrane organelles;
• the presence of mesosomes (a kind of protrusion of the membrane into the middle of the cell);
• small ribosomes compared to eukaryotes;
• Bacteria have one chromosome, cyanobacteria have several chromosomes that are located in the cytoplasm;
• absence of nucleoli;
• no mitochondria;
• the cell wall of bacteria consists of murein, and that of cyanides consists of cellulose;
• flagella are distinguished by their simple structure and small diameter;
• There is no sexual process; reproduction occurs through division.

Under unfavorable conditions, many microorganisms form spores, which can lie for years waiting for suitable conditions for life and development. Plants and fungi also produce spores, but they need them to reproduce. There are microbes that feed like plants and are autotrophs, and some feed like animals and are heterotrophs. Unlike other living organisms, whose life is impossible without the presence of oxygen, there are microorganisms that are able to live in an anaerobic environment, and oxygen, on the contrary, is destructive for them.

Bacteria are the most numerous creatures on the planet, and most of them are still unexplored.

plant kingdom

The classification is based on their main difference - autotrophic nutrition. They are capable of converting inorganic substances into organic ones. To do this they need solar energy. This is also characteristic of cyanobacteria. Thanks to plants and cyanobacteria, the air on the planet is enriched with oxygen, which is so necessary for other living organisms. Plants are a source of food for many other organisms. They are divided into two subkingdoms: algae and higher ones. Algae do not have roots, stems and leaves, unlike higher forms.

A special place is occupied by primitive algae (pyrrophytes), whose cells lack histones in their chromosomes; their structure is close to the nucleoid of bacteria. The cell wall of some algae is made of chitin, like those of animals and fungi. Red algae differ from other species in that their cells do not have flagella. There are differences in structural features and biochemical processes.

kingdom of mushrooms

For a long time, scientists argued about whether to classify mushrooms into a separate kingdom or not. As a result of long debates, they were nevertheless identified separately, since they have much in common with both plants and animals.

Their method of nutrition is the same as that of animals - heterotrophic. Just like animals, they lack plastids and have chitin in their cell walls. As a result of metabolic processes, urea is formed. Fungi, like plants, absorb nutrients through absorption. They are immobile and have a growth pattern similar to that of plants.

Some fungi reproduce like bacteria ─ asexually, some like plants ─ vegetatively, some like animals ─ sexually. Many of them, like microbes, process dead living organisms, thereby playing the role of “orderlies”. Many of them are beneficial and are used in the production of antibiotics, hormones, and vitamins.

Depending on how they consume organic substances, they are divided into three types:

Lichens

Many scientists insist on classifying lichens as a separate kingdom. There are several reasons for this. They can be symbionts:

• mushroom and algae;
• bacteria fungi and algae.

Based on their appearance, they are divided into three groups:

• cortical (which grow on stones and firmly grow together with the surface);
• leafy (attached to the surface with a stalk);
• bushy (attached to the soil, trees, shrubs in the form of bushes).

The body of the lichen is called the thallus, which differs in size, color, shape and structure among different species. The thallus can be from several centimeters to a meter.

Lichens grow very slowly, but their lifespan can be from hundreds to thousands of years.

As a result of symbiosis, a single organism is obtained. Moreover, the hyphae of the fungus are closely intertwined with algae cells. Thus, the lichen combines two completely different organisms in structure and method of nutrition. Fungi that form a symbiosis with algae are not found separately in nature, but the species of algae participating in the symbiosis can also be found as a separate living organism.

Lichens have a unique way of feeding: fungi absorb dissolved minerals, and cyanobacteria form organic matter and participate in the process of photosynthesis. Lichens can reproduce either by spores or by dividing the thallus.

The sensitivity of lichens to polluted environments makes them indicators of cleanliness. Many species are used for animal nutrition and for medicinal purposes.

animal kingdom

The animal kingdom is divided into two subkingdoms: protozoa and multicellular. Even though protozoa are made up of a single cell, just like bacteria, they have all the characteristics of animals. There are species of protozoa that feed autotrophically in the light, and in its absence switch to heterotrophy. Protozoa can reproduce both asexually (cell division) and sexually (conjugation).

What animals and plants have in common is metabolism and cell structure. The main difference is the way of eating. Animals are heterotrophs, that is, they feed on ready-made organic compounds and are not able to synthesize inorganic substances. For the most part they are mobile.

The more complex structure of eukaryotic cells suggests that they received these improvements as a result of evolution. And the simultaneous existence on earth of both prokaryotes and eukaryotes suggests that biological processes are characteristic of all forms of life. All living organisms live in complete interaction with each other, and the disappearance of at least one of the species would lead to irreversible consequences. There is a place on the planet for all types of ecological chain.