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The wildlife of Antarctica are extremophiles, having to adapt to the dryness, low temperatures, and high exposure common in Antarctica. The extreme weather of the interior contrasts to the relatively mild conditions on the Antarctic Peninsula and the subantarctic islands, which have warmer temperatures and more liquid water. Much of the ocean around the mainland is covered by sea ice. Birds and seals mostly live near the edges of the continent. The oceans themselves are a more stable environment for life, both in the water column and on the seabed. There is relatively little diversity in Antarctica compared to much of the rest of the world. Flying birds nest on the milder shores of the Peninsula and the subantarctic islands. Eight species of penguins inhabit Antarctica and its offshore islands. They share these areas with seven pinniped species. The Southern Ocean around Antarctica is home to 10 cetaceans, many of them migratory. There are very few terrestrial invertebrates on the mainland, although the species that do live there have high population densities. High densities of invertebrates also live in the ocean, with Antarctic krill forming dense and widespread swarms during the summer. Benthic animal communities also exist around the continent. Over 1000 fungi species have been found on and around Antarctica. Larger species are restricted to the subantarctic islands, and the majority of species discovered have been terrestrial. Plants are similarly restricted mostly to the subantarctic islands, and the western edge of the Peninsula. Some mosses and lichens however can be found even in the dry interior. Many algae are found around Antarctica, especially phytoplankton, which form the basis of many of Antarctica's food webs. Human activity has caused introduced species to gain a foothold in the area, threatening the native wildlife. A history of overfishing and hunting has left many species with greatly reduced numbers. Pollution, habitat destruction, and climate change pose great risks to the environment. The Antarctic Treaty System is a global treaty designed to preserve Antarctica as a place of research, and measures from this system are used to regulate human activity in Antarctica. ==Environmental conditions== Around 98% of continental Antarctica is covered in ice up to thick. Antarctica's icy deserts have extremely low temperatures, high solar radiation, and extreme dryness. Any precipitation that does fall usually falls as snow, and is restricted to a band around from the coast. Some areas receive as little as 50mm of precipitation annually. The coldest temperature recorded on Earth was at Vostok Station on the Antarctic Plateau.〔 Organisms that survive in Antarctica are often extremophiles.〔 The dry interior of the continent is climatically different from the western Antarctic Peninsula and the subantarctic islands. The Peninsula and the islands are far more habitable, some areas of the peninsula can receive 900mm of precipitation a year, including rain, and the northern Peninsula is the only area on the mainland where temperatures are expected to go above in summer.〔 The subantarctic islands have a milder temperature and more water, and so are more favourable for life.〔 The surface temperature of the Southern Ocean varies very little, ranging from to . During the summer sea ice covers of ocean. The continental shelf surrounding the mainland is - wide. The depth of the seafloor in this area ranges from - , with an average of . After the shelf the continental slope descends to abyssal plains at - deep. In all these areas 90% of the seafloor is made up of soft sediments, such as sand, mud, and gravel. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Wildlife of Antarctica」の詳細全文を読む スポンサード リンク
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