Dimorphism


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Dimorphisms in the bee . From left to right: worker, queen, drone

In biology, dimorphism (from ancient Greek δίμορφος dímorphos , ` ` two-shaped '') describes the occurrence of two clearly different occurrences of the same species.

Sexual dimorphism

The best known form of dimorphism is sexual or gender dimorphism, in which male and female individuals differ significantly from each other. The difference, as is often the case with spiders and some fish, may be in size. The sexes can also have different colors, as is the case with many bird species, in which the female is often inconspicuously colored for camouflage, while the male has bright colors. In walruses , sexual dimorphism is given by the male's tusks , which the females lack. In plants, dioecious as well as some forms of Subdiözie and Gynodioecy and Pleogamie (occurrence monosexual flowers beside the hermaphrodite flowers in varying distribution on the individuals of the same species).

Other forms of biological dimorphism

On ivy ( Hedera helix ) the shoot dimorphism can be observed - there are tendrils and flower shoots, as well as the leaf dimorphism on the same plant.
  • Two different dimmorphisms can be observed in honey bees: on the one hand, a sexual dimorphism between males (drones) and switches, and on the other hand, there is a pheromone- controlled dimorphism in the females in queen and worker.
  • Seasonal dimorphism , example: many dwarf shrubs of the Phrygana produce larger leaves in the rainy half of the year (winter) and smaller leaves in the dry half of the year (summer).
  • Certain types of yeast can take different forms , depending on their pH .
  • Leaf dimorphism is the expression of differently pronounced leaves in one and the same individual. It can be related to the age of the leaves (e.g. in marsh jugs ) or the position on the plant itself (can dimorphism in pitcher plants ).
  • Tawny owls occur in two color morphs , regardless of gender.
  • In plants, the phenomenon of heteromesogamy , the occurrence of flowers which differ in the type of pollination, in different specimens of the same species. Individuals of the same species have different pollinating systems.

Extra biological use

In the meantime, the term has been transferred in the general sense of two forms or the juxtaposition of different forms to other areas of science, where it denotes two different manifestations of a basic form, for example in archeology with settlement dimorphism , which indicates different forms of a basic type of settlement (for example in the village). Even prehistoric tool categories are sometimes differentiated in this way.

With this rather unspecific use, however, the boundary to polymorphism is sometimes blurred, as one would like to describe above all a drifting apart of initially two, but later also more, variants that are not always precisely delimited, for example in paleoanthropology the environmentally-related dimorphism in Australopithecus into graceful and robust Forms ( A. robustus vs. A. africanus ).

In mineralogy , dimorphism denotes minerals when they occur in two different crystal systems.

See also

Individual evidence

  1. ^ Wilhelm Gemoll : Greek-German school and hand dictionary . G. Freytag, Hölder-Pichler-Tempsky, Munich / Vienna 1965.
  2. Karl Linsbauer (Ed.): Short dictionary of botany. 2nd Edition. Engelmann, 1917, p. 306, archive.org .