Scandinavia
Norway, Sweden, Denmark, Iceland
Because of the Vikings, who attacked other countries.
Scandinavia includes Denmark, Norway, and Sweden. These countries have dominated Northern Europe throughout history, and have conquered Iceland and Finland in addition to other lands. They've spread their Scandinavian culture, languages, etc. to these lands, which is why Finland and Iceland are sometimes included in Scandinavia, but rarely. The term 'Nordic' refers to all five of these countries. Northern Europe most commonly includes these five countries.
Australia is referred to as the island continent because it is both a country and a continent surrounded by water, making it the largest island in the world. It is also the smallest continent in terms of land area, yet it is considered a continent due to its size and geologic nature.
Northern Europe is usually composed of only the Nordic countries: Denmark, Finland, Iceland, Norway, and Sweden. Scandinavia includes Denmark, Norway, and Sweden. These countries have dominated Northern Europe throughout history, and have conquered Iceland and Finland in addition to other lands. They've spread their Scandinavian culture, languages, etc. to these lands, which is why Finland and Iceland are sometimes included in Scandinavia, but rarely. The term 'Nordic' refers to all five of these countries.
The genes present on same chromosomes are sometimes linked to each other that inherit collectively are linked genes and can be separated by crossing over
The countries which make up the region of Scandinavia include Sweden, Denmark, Norway, Finland, and Iceland. However, the definition of Scandinavia varies a lot. Some would not include Iceland because it is nowhere near the Scandinavian peninsula and/or Finland because they don't speak a Scandinavian language.
Canada and the United States
In Finland (and some other countries like Russia) they claim that Santa Claus lives in Lapland, which is the Northern part of the Scandinavian peninsula. In reality Santa is of course living on Greenland, i.e. not in the geographical Scandinavia.
Boreal forests? Canada, Russia and Scandinavia have vast boreal forests
Iceland was ruled by Scandinavian countries for centuries. This caused Icelandic culture to be based on Scandinavian culture, the Icelandic language to be based off other Scandinavian languages, and the majority of Icelandics to be of Scandinavian descent. So in a way, Iceland could be considered a child of Scandinavia, as Scandinavia helped produce Iceland.