The Antarctica

The Arctic

The Arctic is a very cold, windy, and often snowy biome located around the North Pole. When referring to the Arctic, people usually mean the part of the earth within the Arctic Circle (an imaginary circle around the Earth, parallel to the Equator and 23 degrees 28 minutes from the North Pole, that is, above about 75 degrees North Latitude). Although there is no land at the North Pole, the icy Arctic Ocean is teeming with life ranging from the microscopic (like zooplankton) to the huge (like whales).

There is also a lot of land within the Arctic Circle (northern parts of Asia, Europe, and North America). Land within the Arctic Circle is tundra, and it supports less life most other biomes because of the cold temperatures, strong, dry winds, and permafrost (permanently-frozen soil). Long periods of darkness (in the winter) and light (in the summer) also affect Arctic life.

Arctic Land Zones

The most extreme Arctic land (the closest to the North Pole) is called the High Arctic Zone; this polar desert supports very little animal or plant life (less than 5 % of the land area is covered with vegetation) due to a very short, dry growing season, dry air, permafrost, poor soils, and a lack of pollinating insects. The warmer Arctic region is called the Low Arctic Zone. This area supports more life, with more than 90 % of the land area covered with hardy, cold-and-dry-adapted vegetation.

Arctic Animals

Animals that live in the Arctic (either full time or seasonally) are adapted to extreme conditions. Many animals who overwinter in the Arctic (like the Arctic fox and the ermine) have a coat that thickens and changes color to white during the winter as camouflage in the snow (blending into the background is called cryptic coloration).

Some animals hibernate during the cold season; they go into a very deep, sleep-like state in which their heartbeat slows down. These animals often hibernate in an underground burrow or pit. Some hibernators include skunks, chipmunks, and some bears (but these bears are not true hibernators, they go into a state that is closer to a normal deep sleep).

Many animals (like the Arctic tern) spend the summer months in the Arctic, but leave as the weather turns frigid and food becomes scarce (these animals return again the next summer, repeating this pattern year after year). This behavior is called migrating.

The Taiga

The taiga, also called a boreal forest or northern coniferous forest, is a cold woodland or forest. This biome span the northern parts of North America, Europe, and Asia. Taigas are generally located south of tundras and north of temperate deciduous forests and temperate grasslands. The taiga is the largest land biome on Earth, covering about 50 million acres of land (20 million hectares); this is about 17 % of the Earth's land area. Taiga is a Russian word for marshy pine forest.

The taiga is characterized by a cold, harsh climate, a low rate of precipitation (snow and rain), and short growing season. There are two types of taigas: open woodlands with widely spaced trees, and dense forests whose floor is generally in shade.

Taigas are relatively low in animal diversity because of the harsh winters. Some taiga animals are able to cope with the cold winter environment, but many migrate south to warmer climates during the winter and others go into hibernation.

The Tundra

The tundra is a cold, treeless area; it is the coldest biome. The tundra is characterized by very low temperatures, very little precipitation (rain or snow), a short growing season, few nutrients, and low biological diversity. The word tundra comes from the Finnish word tunturia, which means "treeless plain".

There are two types of tundras, Arctic tundras and alpine tundras.

· Arctic tundras are frozen, windy, desert-like plains in the Arctic that are dotted with bogs and ponds. Permafrost (a layer of frozen subsoil) covers the ground, so there is very little drainage of water. The short growing season lasts for only 50 to 60 days. Arctic tundras are located in the far north of Greenland, Alaska, Canada, Europe, and Russia. Some animals of the Arctic tundra include:

o Mammals – Arctic foxes, Arctic hares, caribou, ermine, lemmings, musk oxen, polar bears, porcupines, Arctic shrews, squirrels, voles, weasels, wolves.

o Birds – Arctic loons, snowy owls, falcons, ptarmigans, ravens, snow buntings, snow birds, snow geese, sandpipers, Arctic terns, tundra swans, many species of gulls.

o Fish – cod, flatfish, salmon, trout.

o Insects – Arctic bumblebees, blackflies, flies, grasshoppers, mosquitoes, and moths.

· Alpine tundras are located high in mountains worldwide, above the tree line. The growing season is about 180 days, and nighttime temperatures are usually below freezing. The soil is well-drained (unlike the Arctic tundra). Some animals of the alpine tundra include:

o Mammals – elk, marmots, mountain goats, pikas, sheep.

o Birds – grouse-like birds.

o Insects – beetles, butterflies, grasshoppers, and springtails.

The Antarctica

The Antarctica, the frozen continent surrounding the Earth's South Pole, and the frigid seas surrounding it, are home to many animals. In particular, the Antarctic seas are teeming with life, ranging from microscopic plankton to the biggest animal that ever lived on Earth, the Blue whale.

The Antarctica is the coldest, windiest, and driest place on Earth. The coldest temperature ever recorded on Earth was in the Antarctica; it went down to approximately –129 °F (–89 °C)! The Antarctic land does not support many life forms. Most of the land of the Antarctica is a frozen desert, with less precipitation than the Sahara Desert (under 2 inches = 5 cm a year). Oddly enough, 70 % of the world's fresh water is frozen in the region of the South Pole.

All of the Antarctic animals have adapted to life in extremely cold conditions. Some, like the whales, seals, and birds, have an insulating layer of fat to protect them from the cold. Others, like many fish and insects, have special chemicals in their blood (natural antifreeze proteins) that keep them from freezing. Many animals (like penguins and seals) have a compact body form and thick skin to help retain body heat. Birds also have waterproof plumage (feathers) and downy insulating feathers.

Some animals leave the Antarctica during its horrendous coldest months, from June until August. Animals like the Humpback whale migrate to warmer waters to reproduce after eating huge amouns of krill in the Antarctic waters. Many other animals (like the Emperor penguin) remain in the Antarctic year-round.

Land and sea animals from Antarctica include:

· Crustaceans – krill (euphausiids), copepods, amphipods, isopods, crabs, shrimp, sea spiders, and many others.

· Other marine invertebrates – squid, cuttle-fish, octopus, marine snails, limpets, sponges, sea stars, sea squirts, nudibranchs, sea anemones, comb jellies, corals, hydroids, sea urchins, Antarctic krill, zooplankton, and many others.

· Insects and Arachnids – Springtails, mites, the midge Parochlus steineni (the only winged insect native to the Antarctic), and others.

· Fish – Antarctic cod, ice fish, crocodile fish, dragon fish, robber fish, rat-tailed fish, skates, eel-pouts, sea snails, and others.

· Mammals – Fur seals (including the Elephant seal, Leopard seal, Weddell seal, Crabeater seal, Ross seal, and Fur seal), Whales (including the Blue whale, Fin whale, Sei whale, Southern right whale, Humpback whale, Minke whale, Sperm whale, Killer whale or Orca, Southern bottlenose whale, Blackfish, Dusky dolphin, Cruciger dolphin, and Spectacled porpoise).

· Birds – many penguins (including Emperor, King, Macaroni, Rockhopper, Chinstrap, Adélie, and Gentoo), many albatrosses (including the Lightly-maned sooty, Wandering, Gray-headed and Black-browed), many petrels (including the Blue, Kerguelen, Gray, Great-winged, White-headed, White-chinned, Snow, Southern giant, Wilson's storm, Black-bellied storm, Gray-backed storm, and pintado), many prions (including the dove, fulmar, and thin-billed), Antarctic fulmar, Antarctic cormorant Kerguelen cormorant, Dominican gull, Brown skua, McCormick's skua, Arctic tern, Kerguelen tern, Wattled sheathbill, Lesser sheathbill, South Georgia pintail, Kerguelen pintail, and South Georgia pipit (the only Antarctic songbird).

Дата добавления: 2015-10-29