Presentation on the topic of mutualism. Presentation on the topic "symbiosis". Between organisms there are direct and indirect relationships, what is their essence

Symbiosis (Greek " living together”) a form of relationship in which both partners or one of them benefit from the other. In nature, there is a wide range of examples of mutually beneficial symbiosis (mutualism). From stomach and intestinal bacteria, without which digestion would be impossible, to plants (an example is orchids, whose pollen can be spread by only one, certain type of insect). 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 is an intermediate link between interaction and merging. In a broader scientific sense, symbiosis is any form of interaction between organisms. different types, including parasitism (relationships that are beneficial to one, but harmful to another symbiont). A mutually beneficial type of symbiosis is called mutualism. Commensalism is a relationship that is beneficial to one, but indifferent to another symbiont, and amensalism is a relationship that is harmful to one, but indifferent to another. A type of symbiosis is endosymbiosis, when one of the partners lives inside the cell of the other. l The science of symbiosis is sim biology. The foundations of the doctrine of mutual assistance (including symbiosis) in the second half of the 19th century were laid independently by Russian naturalists P. A. Kropotkin and K. F. Kessler, as well as the German scientist Heinrich Anton de Bary, who proposed the terms "symbiosis" and "mutualism".

Commensalism Depending on the nature of the relationship of commensal species, three types of commensalism are distinguished: commensal is limited to the use of food from the organism of another species (for example, in the windings of the shell of a hermit crab lives ringed worm from the genus Nereis, feeding on the remains of cancer food); commensal attaches itself to an organism of another species, which becomes a “host” (for example, a fish stuck with a sucker fin attaches to the skin of sharks, etc. big fish, moving with their help); commensal settles in internal organs host (for example, some flagellates live in the intestines of mammals). l An example of commensalism is legumes (eg 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 sunlight, without which spruce cannot grow in an open place, and also protect seedlings of young spruces 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. l Shrubs of the labiate and Compositae families and South American cacti are composed in the same relationship. With a special type of photosynthesis (CAM photosynthesis), 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 of the organelles of the eukaryotic cell at the beginning of their existence were separate organisms, and about a billion years ago they combined their efforts to create cells of a new type. Therefore, our own bodies illustration of one of the oldest partnerships in nature. l 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 (symbiotic fungi or bacteria) live inside the plant, feed on its substances, releasing compounds that promote the growth of the host organism. The transport of plant seeds by animals that eat the fruit and excrete the undigested seeds along with the droppings elsewhere. l Insects/Plants - Pollination flowering plants insects, during which the insects feed on nectar. -Some plants, such as tobacco, attract insects that can protect them from other insects. -The so-called "gardens of the devil": Duroia hirsuta trees serve as dwellings for ants of the species Myrmelachista schumanni, which kill the green sprouts of other tree species that appear in the vicinity, thereby making it possible for Duroia hirsuta to grow without competition.

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The concept of symbiosis

Symbiosis is cohabitation, a form of relationship in which both partners or one of them benefit from the other. There are several forms of mutually beneficial cohabitation of living organisms.

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Cooperation

• Cooperation - the usefulness of the coexistence of organisms is obvious, but their connection is not necessary.
• It is well known cohabitation of hermit crabs with soft coral polyps- anemones. Cancer settles in an empty shell of a mollusk and carries it on itself along with a polyp.

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Symbiosis is cohabitation, a form of relationship in which both partners or one of them benefit from the other. There are several forms of mutually beneficial cohabitation of living organisms (Zakharov V. B. General biology: Textbook for grades 10-11 of general educational institutions / V. B. Zakharov, S. G. Mamontov, N. I. Sonin. - 7th ed., stereotype - M.: Drofa, 2004).

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Cooperation - the usefulness of the coexistence of organisms is obvious, but their connection is not necessary. It is well known that hermit crabs cohabit with soft coral polyps - sea anemones. Cancer settles in an empty shell of a mollusk and carries it on itself along with a polyp.

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Cooperation Such cohabitation is mutually beneficial: moving along the bottom, the cancer increases the space used by the sea anemone for catching prey, part of which is affected by the stinging cells of the sea anemone, falls to the bottom and is eaten by the cancer.

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Some birds lead a similar lifestyle. They go into the mouth of a crocodile and clean it

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Mutualism is a form of mutually beneficial cohabitation, when the presence of a partner becomes a prerequisite for the existence of each of them. One of the most famous examples of such relationships is lichens, which are the cohabitation of a fungus and algae. In lichen, the hyphae of the fungus, braiding the cells and threads of algae, form special suction processes that penetrate into the cells. Through them, the fungus receives the products of photosynthesis formed by algae. The algae from the hyphae of the fungus extracts water and mineral salts. Cetraria centrifuga

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A typical mutualism is the relationship between termites and flagellar protozoa that live in the intestines. Termites feed on wood, but they do not have enzymes for digestion and cellulose. Flagellates produce these enzymes and convert fiber into simple sugars.

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Without protozoa - symbionts - termites die of starvation. The flagellates themselves, in addition to a favorable climate, receive food and conditions for reproduction in the intestines of termites. Intestinal symbionts involved in the processing of rough plant foods have been found in many animals: ruminants, rodents, and grinder beetles.

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Cohabitation of nodule bacteria and legumes An example of a mutually beneficial relationship is the cohabitation of so-called nodule bacteria and legumes (peas, beans, soybeans, clover, alfalfa, vetch, locust, peanut or peanut).

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Nodules on the roots of soybeans These bacteria, capable of absorbing atmospheric nitrogen and converting it into ammonia and then into amino acids, settle in the roots of plants. The presence of bacteria causes the growth of root tissues and the formation of nodules.

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Cohabitation of nodule bacteria and leguminous plants Plants in symbiosis with nitrogen-fixing bacteria can grow on soils poor in nitrogen and enrich the soil with it. That is why legumes - clover, alfalfa, vetch - are introduced into crop rotations as predecessors for other crops.

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Mycorrhiza - cohabitation of a fungus with the roots of higher plants On the roots of birch, pine, oak, spruce, as well as orchids, heather, lingonberry and many perennial herbs, the mycelium of the fungus forms a thick layer.

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Hyphae of the fungus Root hairs on the roots of higher plants do not develop, and water and mineral salts are absorbed by the fungus.

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Mycorrhiza is the cohabitation of a fungus with the roots of higher plants. The mycelium of the fungus even penetrates into the root, receiving carbohydrates from the partner plant and delivering water and mineral salts to it. Trees with mycorrhiza grow much better than without it. Different types of mycorrhiza

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Symbiosis Some species of ants feed on the sugary excrement of aphids and protect them from predators, in a word - "graze".

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Freeloading Freeloading can take many forms. For example, hyenas pick up the remains of half-eaten prey by lions.