The Tundra Biome and Arctic Region
Compared with other biomes, the tundra biome is relatively young, having its origin in the Pleistocene (1,600,000 to 10,000 years ago). Individual plant and animal species of the tundra, however, probably first appeared in the Late Miocene (11.2 to 5.3 million years ago) or Early Pliocene (5.3 to 3.4 million years ago). Coniferous forests were present on Ellesmere Island and in northern Greenland, the northernmost land areas, in the mid-Pliocene (2.5 million years ago). Most paleoecologists believe that tundra flora evolved from plants of the coniferous forests and alpine areas as continents drifted into higher and cooler latitudes during the Miocene (23.7 to 5.3 million years ago). Antarctica has been isolated from other continental landmasses by broad expanses of ocean since early in the Tertiary Period, about 60 to 40 million years ago. Prior to its separation it existed, along with Australia, South America, peninsular India, and Africa, as part of the landmass known as Gondwanaland. This long separation has impeded the establishment and development of land-based flora and fauna in the Antarctic. Other significant factors that have hampered terrestrial biotic evo
The vegetation of the High Arctic is less rich than that of the Low Arctic, containing only about half the vascular plant species found in the Low Arctic. For example, more than 600 species of plants are found in the Low Arctic of North America, but in the extreme High Arctic of northern Ellesmere Island and Greenland--north of 83º N--fewer than 100 species of vascular plants grow. The shorter growing season, cooler summers, and drier conditions, as well as the distance of these landmasses from continental flora, account for this difference. More than 40 percent of vascular plant species of the Arctic are circumpolar in distribution. Mosses increase in importance in High Arctic plant communities, and shrub species decrease markedly, with only a few prostrate willows, dwarf birch, and other dwarf shrubs remaining. Prostrate willows, however, remain important components of plant communities that retain some winter snow cover, even in the northernmost land areas. Sedge-moss meadows occur on limited wet sites in valley bottoms watered by melting snows. Upland sites are drier and have a more sparse ground cover that merges into polar desert at higher elevations or where insufficient moisture is available for plant growth. Grasses, occasional prostrate willows, and mat-forming dryas occur in patches in the uplands and are the dominant vegetation in the polar barrens. In Antarctica unique endolithic (stone-dwelling) forms of life (cyanobacteria) occur within and just below the surface of porous rocks. These cyanobacteria can be found in dry valleys of southern Victoria Land, where they are adapted to remain dormant for extended periods until rare occasions when melting snow provides the moisture necessary for life processes. Although this is an extreme cold-desert environment, similar forms of life occur within rocks in hot deserts. (For information on the biota of the Antarctic islands see above Origin of the flora and fauna of the polar regions: The Antarctic region.)
Some common words found in the essay are:
Arctic Antarctic, Low Arctic, Arctic Ocean, South Georgia, Island Greenland--north, Land Arctic, Arctic Archipelago, Greenland Eurasia, Biota Antarctica, Arctic Wet, low arctic, polar barrens, tundra polar barrens, tundra polar, north america, plant growth, snow cover, species arctic, plant animal, plant communities, flora fauna, species vascular plants, temperate tropical ecosystems, shorter growing season, north america greenland,
Approximate Word count = 3602
Approximate Pages = 14 (250 words per page double spaced)
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