Cosmopolitan distribution
In biogeography
Biogeography is the study of the distribution of species , organisms, and ecosystems in space and through geological time. Organisms and biological communities vary in a highly regular fashion along geographic gradients of latitude, elevation, isolation and habitat area...

, a taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...

 is said to have a cosmopolitan distribution if its range
Range (biology)
In biology, the range or distribution of a species is the geographical area within which that species can be found. Within that range, dispersion is variation in local density.The term is often qualified:...

 extends across all or most of the world in appropriate habitats. For instance, the killer whale has a cosmopolitan distribution, extending over most of the world's oceans. Other examples include human
Humans are the only living species in the Homo genus...

s, the lichen
Lichens are composite organisms consisting of a symbiotic organism composed of a fungus with a photosynthetic partner , usually either a green alga or cyanobacterium...

 species Parmelia sulcata
Parmelia sulcata
Net-marked parmelia , or Shield lichen, is a lichen in the family Parmeliaceae. It is very tolerant of pollution and is widespread making it one of the more common lichens....

and the mollusc
The Mollusca , common name molluscs or mollusksSpelled mollusks in the USA, see reasons given in Rosenberg's ; for the spelling mollusc see the reasons given by , is a large phylum of invertebrate animals. There are around 85,000 recognized extant species of molluscs. Mollusca is the largest...

 genus Mytilus
Mytilus (mollusc)
Mytilus is a cosmopolitan genus of medium-sized to large edible saltwater mussels, marine bivalve molluscs in the family Mytilidae.-Species:Species within the genus Mytilus include:* Mytilus californianus Conrad, 1837 - California mussel...

. It may result from a broad range of environmental tolerances, or from rapid dispersal
Biological dispersal
Biological dispersal refers to species movement away from an existing population or away from the parent organism. Through simply moving from one habitat patch to another, the dispersal of an individual has consequences not only for individual fitness, but also for population dynamics, population...

 compared to the time needed for evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

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