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Mutualism

Many species of animals, plants and fungi coexist and cooperate with other species, which is generally beneficial to both organisms. This type of relation is called symbiosissymbiosissymbiosis and belongs to a group of non‑antagonistic relationsnon‑antagonistic relationsnon‑antagonistic relations. A kind of symbiosis in which cooperation between two species is necessary for their survival is referred to as mutualismmutualismmutualism, i.e. obligatory symbiosis. An example of this type of symbiosis is the cooperation of fungi and green algae forming lichens. Lichens are found in extremely unfavorable conditions, in which the living components of lichen could not survive. The fungus protects the algae cells against negative impact and absorbs water from the environment, and the algae conducts photosynthesis to produce nutrients for itself and its partner. They even reproduce together. They form easily detachable clusters of fungus and algae cells (isidia or soredia) that spread by the wind inhabit new environment.

A very interesting case of symbiosis is the relationship between manioc ants, living in Middle and South America, and fungi. These ants are not able to feed on the leaves, because they do not digest the cellulose contained therein. Therefore, they prepare the surface from them, instil fungi thereon and cultivate them. The cultivated fungi form at the ends of their hyphae spherical construct filled with easily digestible substances from the substrate decomposed by the fungi, which the ants collect and feed on. In the wilderness, there are no manioc ants in nests without fungi, and these fungi can be found only in the nests of manioc ants.

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Fotografia przedstawia rude mrówki idące po piasku i wchodzące na kamień. Kilka mrówek niesie liście, pocięte na trójkątne kawałki. Liście posłużą jako podłoże dla grzyba.

A special case of mutualism is the symbiotic relationship between ruminantsruminantsruminants, such as cows or deer, and microorganisms living in their digestive systems. In one of the parts of their multi‑chambered stomach, called the rumen, live bacteria and protozoa capable of digesting cellulose. From time to time, rumen content, partially digested by symbionts, returns to the mouth of the animal, where it is masticated. When swallowed again, grass and certain microorganisms are digested with the help of herbivore's digestive enzymes. This way, ruminants gain not only sugars but also protein and vitamins (mainly vitamins from B group and vitamin K) produced by bacteria.

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Fotografia przedstawia zbliżenie głowy żyrafy. Jest łaciata, brązowo – biała. Do góry sterczą okryte sierścią rożki. Dolna szczęka żyrafy jest mocno przesunięta względem górnej. Żyrafa przeżuwa zjedzony pokarm roślinny tak jak krowa.

Another example of symbiosis is the relationship between flowers and their pollinators. This is how the flowers can transfer male gametes from one flower (specimen) to another. As a result, fertilisation and seed production occurs. In return, pollinators use the nectar and pollen produced by flowers. In the case of certain plant species, only one specially adapted insect species can pollinate them. This is the case of red clover. It has particularly long and narrow flowers, the bottom of which can only be reached by the mouthpiece of a bumblebee. Clover cannot exist without this insect, but the bumblebee can also feed on the nectar of other flowers. Hummingbirds are also specialists in pollination of specific species. They only visit those flowers whose shape fits perfectly the shape of their beaks.

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Fotografia koniczyny łąkowej (kwiatostanu) z siedzącym na nim trzmielem. Widać aparat gębowy trzmiela.

MycorrhizamycorrhizaMycorrhiza, cooperation of fungi with plants, is also a case of mutualism. It involves braiding the roots of a plant by the hyphae of the mycelium, which grow into their interior, and form a dense network on their surface. Mycelium increases the absorbent surface of the root. This way, the fungi take and supply water, phosphorus and nitrogen compounds to the plants. In exchange, they can feed on the nutrients produced by plants in the process of photosynthesis. Larch seeds, as they fall on the soil overgrown with mycelium of the suillus luteus, quickly sprout and develop healthy plants. A larch grows much weaker in soil deprived of mycelium.

Further pairs of species that provide services to one another are birch boletes and birches, porcini mushrooms and oaks, red pine mushrooms and spruce.

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Rysunek przedstawia brązowego grzyba koźlarza babkę z lewej i pień biało – czarnej brzozy z prawej. Rosną na brązowej ziemi, w której ukazano białą grzybnię i szare korzenie drzewa. W centrum rysunku pomarańczowe kółko powiększenia wskazuje miejsce, w którym strzępki grzyba oplatają korzeń. Pomarańczowa strzałka od brzozy do koźlarza wskazuje przepływ związków organicznych. Strzałka od grzyba do drzewa wskazuje przepływ wody i soli mineralnych. Ponadto grzyb zapewnia drzewu ochronę przed mikroorganizmami chorobotwórczymi. To mikoryza. Podpisano: Mycorrhiza; birch bolate; organic compounds; water, mineral salts, protection against pathogenic microorganisma; birch; fungi hyphae entangling the roots of the plant;

Summary

• Non‑antagonistic relations bring benefits to at least one of the parties.

• Symbiosis is a way to adapt to the environment.

• Species living with each other in symbiosis usually develop adjustments that allow them to remain in this relationship that are reflected , e.g. in their physique.

Keywords

mutualism, symbiosis, mycorrhiza

Glossary