The Antarctic realm is one of eight terrestrial biogeographic realms. The ecosystem includes Antarctica and several island groups in the southern Atlantic and Indian oceans. The continent of Antarctica is so cold that it has supported only 2 vascular plants for millions of years, and its flora presently consists of around 250 lichens, 100 mosses, 25-30 liverworts, and around 700 terrestrial and aquatic algal species, which live on the areas of exposed rock and soil around the shore of the continent. Antarctica's two flowering plant species, the Antarctic hair grass (Deschampsia antarctica) and Antarctic pearlwort (Colobanthus quitensis), are found on the northern and western parts of the Antarctic Peninsula. Antarctica is also home to a diversity of animal life, including penguins, seals, and whales.
Several Antarctic and sub-Antarctic island groups are considered part of the Antarctic realm, including Bouvet Island, the Crozet Islands, Heard Island, the Kerguelen Islands, the McDonald Islands, the Prince Edward Islands, the South Georgia Group, the South Orkney Islands, the South Sandwich Islands, and the South Shetland Islands. These islands have a somewhat milder climate than Antarctica proper, and support a greater diversity of tundra plants, although they are all too windy and cold to support trees.
Antarctic krill is the keystone species of the ecosystem of the Southern Ocean, and is an important food organism for whales, seals, leopard seals, fur seals, crabeater seals, squid, icefish, penguins, albatrosses and many other birds. The ocean there is so full of phytoplankton because water rises from the depths to the light-flooded surface, bringing nutrients from all oceans back to the photic zone.
On August 20, 2014, scientists confirmed the existence of microorganisms living 800 metres (2,600 feet) below the ice of Antarctica.
Millions of years ago, Antarctica was warmer and wetter, and supported the Antarctic flora, including forests of podocarps and southern beech. Antarctica was also part of the ancient supercontinent of Gondwanaland, which gradually broke up by continental drift starting 110 million years ago. The separation of South America from Antarctica 30-35 million years ago allowed the Antarctic Circumpolar Current to form, which isolated Antarctica climatically and caused it to become much colder. The Antarctic flora subsequently died out in Antarctica, but is still an important component of the flora of southern Neotropical (Latin America and the Caribbean) and Australasian realms, which were also former parts of Gondwana.
Some botanists recognize an Antarctic Floristic Kingdom that includes Antarctica, New Zealand, and parts of Temperate South America where the Antarctic Flora is still a major component.
The Antarctic realm is divided into 17 tundra ecoregions:
|Adelie Land tundra||Adélie Land|
|Central South Antarctic Peninsula tundra||Antarctic Peninsula|
|Dronning Maud Land tundra||Queen Maud Land|
|East Antarctic tundra||Eastern Antarctica|
|Ellsworth Land tundra||Ellsworth Land|
|Ellsworth Mountains tundra||Ellsworth Mountains|
|Enderby Land tundra||Enderby Land|
|Marie Byrd Land tundra||Marie Byrd Land|
|North Victoria Land tundra||Victoria Land|
|Northeast Antarctic Peninsula tundra||Antarctic Peninsula|
|Northwest Antarctic Peninsula tundra||Antarctic Peninsula|
|Prince Charles Mountains tundra||Prince Charles Mountains|
|Scotia Sea Islands tundra||South Georgia and the South Sandwich Islands, South Shetland Islands, Bouvet Island|
|South Antarctic Peninsula tundra||Antarctic Peninsula|
|South Orkney Islands tundra||South Orkney Islands|
|South Victoria Land tundra||Victoria Land|
|Southern Indian Ocean Islands tundra||Crozet Islands, Prince Edward Islands, Heard Island, Kerguelen Islands, McDonald Islands|
|Transantarctic Mountains tundra||Transantarctic Mountains|