Mutually beneficial relationships of organisms - symbiosis. What is the phenomenon of symbiosis What is the phenomenon of symbiosis 5 cells

The phenomenon of symbiosis occurs in many groups of plants and animals. Legumes and their associated nitrogen-fixing bacteria provide a remarkable example. These bacteria live in special nodules that develop on the roots of legumes under the action of the bacteria themselves; they receive nutrients from the plant, while they themselves bind atmospheric nitrogen, turning it into such chemical compounds that can be used by symbiont plants. Bacteria live in symbiosis with many other organisms. So, in horses, cattle, sheep and other ruminants, consuming feed rich in fiber, in gastrointestinal tract bacteria live, partially digesting this rough food. In return, the bacteria receive all the nutrition they need from the host.

Another example of symbiosis is lichens. They are a very close union of the fungus and unicellular green (rarely blue-green) algae. The fungus provides the algae with anchorage and protection, as well as a supply of water and inorganic salts. The algae provides the fungus with the products of photosynthesis. Under favorable circumstances, both the fungus and algae that make up the lichen can live separately, but only being in symbiosis are they able to grow in such harsh conditions in which many plants do not survive. It is no coincidence that it is lichens that often live on bare rocks, being the only settlers in such places.

Unicellular green, yellow-green and brown algae often act as animal symbionts. At the same time, algae supplies the animal with the products of photosynthesis, receiving, in turn, both a shelter and a number of substances necessary for life. Green algae are symbionts of freshwater protozoa, hydra, and some freshwater sponges. Brown algae are often found as symbionts of marine protozoa (some species of foraminifera and radiolarians). Similar algae live in symbiosis with corals, sea anemones and certain types flatworms.

Various protozoa are symbionts of wood-eating animals; they are typical inhabitants of the intestines, for example, termites and forest cockroaches, where they perform the same work as the bacteria processing fiber - symbionts of ruminants. The union of termites and the protozoa living in their intestines is strictly obligate, i.e. these organisms cannot exist without each other.

A well-known example of symbiosis is the cohabitation of a hermit crab and sea anemone. The sea anemone settles on the shell in which the hermit crab lives, and with its tentacles equipped with stinging cells creates additional protection for it, and he, in turn, drags the sea anemone from place to place, thereby increasing its hunting territory; in addition, sea anemones can also eat leftovers from the meal of a hermit crab.

Another interesting case symbiosis - the relationship between ants and aphids. Ants guard, graze and "milk" completely defenseless aphids, receiving sweet excretory products from them. See also MARINE BIOLOGY
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Symbiosis

or mutualism, a form of relationship between organisms (symbionts) of two different types bringing mutual benefit. The degree of manifestation of symbiosis can be different, resembling parasitism in this respect, the manifestations of which also vary significantly. Sometimes symbiotic relationships are so important for the life of organisms that the death of one of them inevitably leads to the death of another. However, the connection is not always so rigid, and organisms can live separately, although they grow and reproduce in this case far from being as successful as when they exist together. In other cases, the equilibrium in the relationship between symbionts turns out to be rather unstable: when conditions are favorable for one of them, it can significantly outstrip its partner in growth and even turn into a predator or parasite in relation to it. The phenomenon of symbiosis occurs in many groups of plants and animals. Legumes and their associated nitrogen-fixing bacteria provide a remarkable example. These bacteria live in special nodules that develop on the roots of legumes under the action of the bacteria themselves; they receive nutrients from the plant, while they themselves bind atmospheric nitrogen, turning it into such chemical compounds that can be used by symbiont plants. Bacteria live in symbiosis with many other organisms. So, in horses, cattle, sheep and other ruminants that consume feed rich in fiber, bacteria live in the gastrointestinal tract, partially digesting this roughage. In return, the bacteria receive all the nutrition they need from the host. Another example of symbiosis is lichens. They are a very close union of the fungus and unicellular green (rarely blue-green) algae. The fungus provides the algae with anchorage and protection, as well as a supply of water and inorganic salts. The algae provides the fungus with the products of photosynthesis. Under favorable circumstances, both the fungus and algae that make up the lichen can live separately, but only being in symbiosis are they able to grow in such harsh conditions in which many plants do not survive. It is no coincidence that it is lichens that often live on bare rocks, being the only settlers in such places. Unicellular green, yellow-green and brown algae often act as animal symbionts. At the same time, algae supplies the animal with the products of photosynthesis, receiving, in turn, both a shelter and a number of substances necessary for life. Green algae are symbionts of freshwater protozoa, hydra, and some freshwater sponges. Brown algae are often found as symbionts of marine protozoa (some species of foraminifera and radiolarians). Similar algae live in symbiosis with corals, sea anemones and certain types of flatworms. Various protozoa are symbionts of wood-eating animals; they are typical inhabitants of the intestines, for example, termites and forest cockroaches, where they perform the same work as the bacteria processing fiber - symbionts of ruminants. The union of termites and the protozoa living in their intestines is strictly obligate, i.e. these organisms cannot exist without each other. A well-known example of symbiosis is the cohabitation of a hermit crab and sea anemone. The sea anemone settles on the shell in which the hermit crab lives, and with its tentacles equipped with stinging cells creates additional protection for it, and he, in turn, drags the sea anemone from place to place, thereby increasing its hunting territory; in addition, sea anemones can also eat leftovers from the meal of a hermit crab. Another interesting case of symbiosis is the relationship between ants and aphids. Ants guard, graze and "milk" completely defenseless aphids, receiving sweet excretory products from them. See also MARINE BIOLOGY.

Such relationships are always successful when they increase the chances of both partners to survive. The actions carried out in the course of symbiosis or the substances produced are essential and irreplaceable for the partners. In a generalized sense, such a symbiosis - intermediate between interaction and fusion.

A kind of symbiosis is endosymbiosis (see Symbiogenesis), when one of the partners lives inside the cell of the other.

The science of symbiosis is symbiology.

Mutualism

Mutually beneficial relationships can be formed on the basis of behavioral responses, for example, as in birds that combine their own food with the distribution of seeds. Sometimes mutualistic species enter into close physical interaction, as in the formation of mycorrhiza (fungal root) between fungi and plants.

The close contact of species in mutualism causes their joint evolution. A typical example is the mutual adaptations that have developed between flowering plants and their pollinators. Mutualist species often co-populate.

Commensalism

Depending on the nature of the relationship of commensal species, three types are distinguished:

• the commensal is limited to the use of the food of an organism of another species (for example, an annelids from the genus Nereis lives in the coils of the shell of a hermit crab, feeding on the remnants of the food of the crab);
• the commensal is attached to the organism of another species, which becomes the "master" (for example, a fish stuck with a sucker fin attaches to the skin of sharks and other large fish, moving with their help);
• commensal settles in the internal organs of the host (for example, some flagellates live in the intestines of mammals).

An example of commensalism is legumes (for example, clover) and cereals growing together on soils poor in available nitrogen compounds, but rich in potassium and phosphorus compounds. Moreover, if the cereal does not suppress the legume, then it, in turn, provides it with an additional amount of available nitrogen. But such a relationship can only last as long as the soil is poor in nitrogen and the grasses cannot grow strongly. If, as a result of the growth of legumes and the active work of nitrogen-fixing nodule bacteria a sufficient amount of nitrogen compounds available for plants accumulates in the soil, this type of relationship is replaced by competition. Its result, as a rule, is the complete or partial displacement of less competitive legumes from the phytocenosis. Another variant of commensalism: one-sided help of a “nanny” plant to another plant. So, birch or alder can be a nanny for spruce: they protect young spruces from direct sun rays, without which a spruce cannot grow in an open place, and also protect the seedlings of young Christmas trees from squeezing them out of the soil by frost. This type of relationship is typical only for young spruce plants. As a rule, when the spruce reaches a certain age, it begins to behave like a very strong competitor and suppresses its nannies.
Shrubs from the families of labiales and Asteraceae and South American cacti are in the same relationship. Possessing a special type of photosynthesis (CAM metabolism), which occurs during the day with closed stomata, young cacti become very overheated and suffer from direct sunlight. Therefore, they can develop only in the shade under the protection of drought-resistant shrubs. There are also numerous examples of symbiosis that is beneficial to one species and does not bring any benefit or harm to another species. For example, the human intestine is inhabited by many types of bacteria, the presence of which is harmless to humans. Similarly, plants called bromeliads (which include, for example, pineapple) live on the branches of trees, but get their nutrients from the air. These plants use the tree for support without depriving it of nutrients. Plants make their own nutrients, they don't get them from the air.

Commensalism is a way of coexistence of two different types of living organisms, in which one population benefits from the relationship, and the other does not receive any benefit or harm (for example, common silverfish and humans).

Symbiosis and evolution

In addition to the nucleus, eukaryotic cells have many isolated internal structures called organelles. Mitochondria, one type of organelle, generate energy and are therefore considered the powerhouses of the cell. Mitochondria, like the nucleus, are surrounded by a bilayer membrane and contain DNA. On this basis, a theory has been proposed for the emergence of eukaryotic cells as a result of symbiosis. One of the cells absorbed the other, and then it turned out that together they cope better than individually. This is the endosymbiotic theory of evolution.
This theory easily explains the existence of a bilayer membrane. The inner layer originates from the membrane of the engulfed cell, while the outer layer is part of the membrane of the engulfed cell wrapped around the alien cell. It is also well understood that the presence of mitochondrial DNA is nothing more than remnants of the alien cell's DNA. So, many (perhaps all) of the eukaryotic cell organelles at the beginning of their existence were separate organisms, and about a billion years ago they joined forces to create a new type of cell. Therefore, our own bodies are an illustration of one of the oldest partnerships in nature.

It should also be remembered that symbiosis is not only the coexistence of different types of living organisms. At the dawn of evolution, symbiosis was the engine that brought unicellular organisms of the same species into one multicellular organism (colony) and became the basis for the diversity of modern flora and fauna.

Examples of symbioses

• Endophytes live inside the plant, feed on its substances, while releasing compounds that promote the growth of the host organism.
• Transportation of plant seeds by animals that eat the fruits and excrete the undigested seeds along with the droppings elsewhere.

insects/plants

mushrooms/algae

• A lichen is composed of a fungus and an algae. As a result of photosynthesis, algae produce organic substances (carbohydrates) that are used by the fungus, which supplies water and minerals.

Animals/Algae

mushrooms/plants

• Many fungi receive nutrients from the tree and supply it with minerals (mycorrhiza).

insects/insects

• Some ants protect ("herd") aphids and receive sugar-containing secretions from them in return.

see also

Notes

Literature

• Margelis L. The role of symbiosis in cell evolution. - M: Mir, 1983. - 354 p.
• Douglas A.E Symbiotic interaction. - Oxford University. Press: Oxford:Y-N, Toronto, 1994. - 148 p.

Links

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Symbiosis- (from Greek symbiosis cohabitation), close cohabitation of organisms of two or more species, which, as a rule, has become necessary and beneficial for both partners (symbionts). Symbiosis in marine animals was discovered by K. Möbius (1877). According to the degree of connection ... Ecological dictionary

symbiosis- a, m. symbiose f. gr. symbiosis. biol. The cohabitation of organisms of different species, usually bringing them mutual benefit, for example. fungus and algae that together form a lichen. SIS 1954. Symbiosis of hermit crab and sea anemone. BAS 1. Vinogradov completed ... ... Historical Dictionary of Gallicisms of the Russian Language

SYMBIOSIS- (from Greek symbiosis living together), diff. forms of coexistence of heterogeneous organisms that make up a symbiotic system. The term "S." proposed by A. De Bari in 1879. In symbiotic. systems, one of the partners (or both) in a certain ... ... Biological encyclopedic dictionary

SYMBIOSIS- (from the Greek syn with, together and bios life), a form of mutual cohabitation of two organisms (or organic groups) associated with obtaining mutual benefit. The term C, introduced in 1867 by de Bari (de Vagu), has various interpretations and in the broadest ... ... Big Medical Encyclopedia

symbiosis- coexistence, cohabitation, epioikia, entoikia, mutualism, commensalism Dictionary of Russian synonyms. symbiosis n., number of synonyms: 13 amensalism (2) ... Synonym dictionary

symbiosis- in biology, long-term cohabitation of organisms of different species, usually mutually beneficial. In psychology, it is often understood broadly. Dictionary of practical psychologist. Moscow: AST, Harvest. S. Yu. Golovin. 1998. Symbiosis ... Great Psychological Encyclopedia

Question 1. Define the main forms of interactions of living organisms.
1. Symbiosis (cohabitation)- a form of relationship in which both partners or one of them benefit from the interaction without causing harm to the other.
2. Antibiosis- a form of relationship in which both interacting populations (or one of them) experience a negative impact.
3. Neutralism- a form of relationship in which organisms living in the same territory do not directly influence each other. They turn them into simple compounds.

Question 2. What forms of symbiosis do you know and what are their features?
There are several forms of symbiotic relationships, characterized by varying degrees of dependence of partners.
1. Mutualism- a form of mutually beneficial cohabitation, when the presence of a partner is a prerequisite for the existence of each of them. For example, termites and flagellate protozoa that live in their intestines. Termites themselves cannot digest the cellulose they feed on, and flagellates receive food, protection and a favorable microclimate; lichens, which are an inseparable cohabitation of a fungus and algae, when the presence of a partner becomes a condition for the life of each of them. Hyphae of the fungus, braiding the cells and threads of algae, receive substances synthesized by algae. Algae extract water and minerals from fungal hyphae. In a free state, lichen fungi do not occur and are able to form a symbiotic organism only with a certain kind algae.
Higher plants also enter into mutually beneficial relationship with mushrooms. Many grasses and trees develop normally only when soil fungi settle on their roots. The so-called mycorrhiza is formed: root hairs do not develop on the roots of plants, and the mycelium of the fungus penetrates into the root. Plants receive water and mineral salts from the fungus, and the fungus, in turn, receives carbohydrates and other organic substances.
2. Cooperation- mutually beneficial coexistence of representatives of different we see, but which, however, is mandatory. For example, hermit crab and anemone soft coral.
3. Commensalism(companionship) - a relationship in which one species benefits, while the other is indifferent. For example, jackals and hyenas, eating up leftover food for large predators- lions; pilot fish.

Question 3. What is the evolutionary significance of symbiosis?
Symbiotic relationships allow organisms to most fully and effectively master the environment, are essential components natural selection involved in the process of species divergence.

Question 1. What is a mycelium?

Mycelium - the vegetative body of the fungus, formed by thin branching threads - hyphae.

Question 3. What is symbiosis?

Symbiosis (from the Greek symbiosis - living together, cohabitation) - a type of interspecific relationship between organisms: coexistence beneficial for individuals of both species or at least for one (nodule nitrogen-fixing bacteria on plant roots).

Question 1. Where are lichens found?

In a dark spruce forest, shaggy gray beards of a bearded lichen descend from old branches to the very ground. In dry pine forests, a continuous carpet of branched pink, gray and white lichens is formed. They crunch underfoot in dry weather. These are bushy lichens. Known as "reindeer moss", the fruticose moss lichen is widely distributed in the tundra. Scale lichens settle on the stones, similar to frozen brown-gray foam. Leafy lichens are widespread in the form of plates of different colors. They grow on rocks and on the bark of trees. Of these lichens, golden-yellow wall xanthoria is especially common on the bark of aspens.

Question 2. How are lichens arranged?

The body of a lichen - thallus - consists of a fungus and algae living in symbiosis as one organism. It is formed by intertwining threads of mycelium, between which are unicellular green algae or blue-green (cyanobacteria). Suction cups sometimes appear on mushroom threads, which penetrate into the algae cell.

Question 3. How do they eat?

The threads of the lichen fungus absorb water and minerals dissolved in it, and in the cells green algae organic matter is formed. The algae that enters the body of the lichen, separated from the fungus, as a rule, can exist independently. The fungus cannot live separately from the algae.

Question 4. Why are lichens called the pioneers of vegetation cover?

Lichens are the first to settle in the most barren places. By releasing special acids, lichens slowly destroy rocks. When they die, they form soil on which other plants can live.

Question 5. What is their practical significance?

In the North, they serve as the main food for deer in winter. From some types of lichens, paint and litmus are obtained, which is necessary for the chemical industry. Many types of lichens are used in medicine and the perfume industry.

Question 6. What is the phenomenon of symbiosis?

The phenomenon of symbiosis consists in the relationship between organisms under such conditions that coexistence is beneficial for individuals of both species.

Question 7. What other examples of symbiosis are you familiar with?

Fungus and algae in lichen, nodule nitrogen-fixing bacteria on plant roots, fungi and trees.

Think

Why are lichens considered as a special group of organisms?

Lichens represent a peculiar group of complex organisms, the body of which always consists of two components - a fungus and an algae. How are lichens different from other plants? First, a specific feature of lichens is the symbiotic cohabitation of two different organisms- heterotrophic fungus and autotrophic algae. Not every cohabitation of fungus and algae forms a lichen. Secondly, lichens form special morphological types, life forms of external and internal structure, not found separately in the fungi and algae that make up the lichen thallus. Thirdly, lichens differ significantly from other groups of organisms, including free-living fungi and algae, in their special biology: methods of reproduction, slow growth, and attitude to environmental conditions.

Quests for the curious

Air pollution is detrimental to most lichens, so the presence of lichens indicates the purity of the air in the area. Study the lichens in your area. Determine what forms of lichens are found here. Make pictures and descriptions of them. Make a conclusion about the purity of the air in your area.

Parmeliopsis doubtful. Thallus in the form of rosettes up to 10 cm in diameter, consists of thin-skinned lobes dissected along the edge, tightly fused with the substrate. The upper side is orange-yellow, sometimes dark greenish, densely covered with yellowish-greenish capitate sorals; the lower one is almost black, densely covered with dark rhizoids. Habitat. On the trunks and branches of conifers and hardwood(especially often on a birch); common on twigs of shrubs, dwarf shrubs, treated wood and stumps. Spreading. Throughout Russia in coniferous and mixed lowland and mountain forests. One of the most common lichens.

Bryoria is hairy. Thallus bushy, hanging, 10–20 cm long, greenish-white. The branches are filiform, slightly branched, thin (0.15–0.3 mm in diameter). Spreading. Buryatia, the species is distributed in the European part of Russia, in the Urals, the North Caucasus, Siberia and Far East. Habitat. It grows in old-growth dark coniferous and black forests, on the trunks and branches of predominantly dark coniferous species.

Cetraria Icelandic. Its thallus looks like a loose turf up to 10-15 cm high. It is formed by flat, sometimes grooved-folded lobes. The lower surface is lighter in color, it is light brown, almost to white, with numerous white spots and ruptures in the bark, which serve to penetrate the air. ground lichen representative pine forests, moorland, swamps, tundra and forest-tundra. It grows directly on the soil or on the bark of old stumps. Prefers sandy unshaded places, where it sometimes forms almost pure thickets. Grows only in clean air.

Evernia is mesomorphic. Thallus is bushy, erect, often hanging, 2.5-10.0 cm long. Lobes 1.0-2.5 mm wide, branched, more or less flattened, sometimes slightly rounded, radial in structure, equally colored on both sides. Grows on tree bark, treated wood, occasionally on mossy soil. Found in temperate and tropical regions of Asia, Europe, North America, including Mexico, the arctic zone. In Russia - throughout the territory.

Conclusion: these are far from all lichens, but even by the presence of these, we can say that the air in our forests is clean.

Answer left Guest

Usually, symbiosis is mutualistic, that is, the cohabitation of both organisms (symbionts) is mutually beneficial and arises in the process of evolution as one of the forms of adaptation to the conditions of existence. Symbiosis can be carried out both at the level of multicellular organisms and at the level of individual cells (intracellular symbiosis). Plants with plants, plants with animals, animals with animals, plants and animals with microorganisms, microorganisms with microorganisms can enter into symbiotic relationships. The term "symbiosis" was first introduced by the German botanist A. de Bari (1879) as applied to lichens. A striking example of symbiosis among plants is mycorrhiza - the cohabitation of fungal mycelium with roots. higher plant(hyphae braid the roots and contribute to the flow of water and minerals from the soil into them); some orchids cannot grow without mycorrhiza.

Nature knows numerous examples of symbiotic relationships from which both partners benefit. For example, for the nitrogen cycle in nature, the symbiosis between leguminous plants and soil bacteria Rhizobium. These bacteria - they are also called nitrogen-fixing - settle on the roots of plants and have the ability to "fix" nitrogen, that is, to break down strong bonds between the atoms of atmospheric free nitrogen, making it possible to incorporate nitrogen into plant-available compounds, such as ammonia. AT this case the mutual benefit is obvious: the roots are the habitat of bacteria, and the bacteria supply the plant with essential nutrients.

There are also numerous examples of symbiosis that is beneficial to one species and does not bring any benefit or harm to another species. For example, the human intestine is inhabited by many types of bacteria, the presence of which is harmless to humans. Similarly, plants called bromeliads (which include, for example, pineapple) live on the branches of trees, but get their nutrients from the air. These plants use the tree for support without depriving it of nutrients.

A type of symbiosis is endosymbiosis, when one of the partners lives inside the cell of the other.

The science of symbiosis is symbiology.