The term biosphere is derived from two words: bios, meaning life, and sphere meaning globe. Therefore the biosphere is the earth's relatively thin zone of air, soil, and water that is capable of supporting life. This ranges from about 10 km into the atmosphere, to the deepest ocean floor. The biosphere can be viewed as a system or a set of functions that operates together and is dependent on each other, that is, a global ecosystem …showed first 75 words of 2099 total…

…showed last 75 words of 2099 total…the most severe conditions of winter. Each year, at the end of the short growing season, they either move southward into the boreal forest, only returning to the tundra to breed, or else they lay dormant when the winter season sets in. The tundra wildlife is vulnerable to habitat destruction, over hunting, and extinction through loss of any of the animal or plant species that make up the fragile, highly interdependent tundra community of life.