Calcium is the chemical element with atomic number 20; it has an atomic mass of 40.078 atomic mass units (amu). The chemical symbol for calcium is Ca. Calcium is a soft gray...
PleistoceneLast Updated on 2014-07-02 14:12:09This article on the Pleistocene Epoch was written by P. D. P, Brian R. Speer and Ben Waggoner.
The mammoth was one of the largest land mammals of the Pleistocene, the time period that spanned from 1.8 million to approximately 10,000 years ago. Pleistocene biotas were extremely close to modern ones — many genera and even species of Pleistocene conifers, mosses, flowering plants, insects, mollusks, birds, mammals and others survive to this day. Yet the Pleistocene was also characterized by the presence of distinctive large land mammals and birds. Mammoths and their cousins the mastodons, longhorned bison, sabre-toothed cats, giant ground sloths, and many other large mammals characterized Pleistocene habitats in North America, Asia, and Europe. Native horses and camels galloped across the plains of North America. Great teratorn birds with 25-foot wingspans stalked prey. Around the... More »
SeleniumLast Updated on 2014-06-29 16:59:07
Selenium is a gray, metallic element. Its atomic number is 34 and its symbol is Se. The Swedish scientist Jons Jacob Berzelius discovered selenium in 1817. In studying the sulfuric acid produced in a particular Swedish factory, he discovered an impurity which he eventually identified as selenium. Selenium occurs in three distinct forms: as a non-crystalline, gray metal; it can form as a deep red to black powder; and it can form as red crystals. It is stable in air and in water. Selenium is actually an important trace element to mammals and some plants. Too much selenium in a mammal’s diet is poisonous and has been shown to cause deformities. When there is not enough selenium, a mammal can also have health problems. For example, sheep that graze in areas with too little selenium in the soil eventually have a problem known as “white muscle disease.” Lack of selenium... More »
Von Humboldt, AlexanderLast Updated on 2014-06-26 16:40:53
Baron Alexander von Humboldt (1769-1859) was one of the last true generalists in science. While generally considered a geographer, he contributed to most of the sciences of the natural environment found today. Born in Berlin, von Humboldt’s father was Chamberlain to the King, a royal advisor, who died when Alexander was nine years old. As a child, he received a private education and was a slow learner and sickly much of the time. On his own, though, he loved collecting local plants and animals and reading books on foreign travel and adventure. He also loved to draw, mostly landscapes. Typical of the time, science was not part of his schooling; Humboldt was generally self taught in that area. At sixteen, he attended some lectures on physics and philosophy by a local doctor and then he decided to pursue a career in science.
Humboldt... More »
Ecoregions of Wisconsin (EPA)Last Updated on 2014-06-26 16:34:28Ecoregions denote areas of general similarity in ecosystems and in the type, quality, and quantity of environmental resources; they are designed to serve as a spatial framework for the research, assessment, monitoring, and management of ecosystems and ecosystem components. Special purpose maps of characteristics such as plant communities, water quality, soils, and fish distributions are necessary and have long been used for dealing with specific research and management problems. Ecoregions, on the other hand, portray areas within which there is similarity in the mosaic of all biotic and abiotic components of both terrestrial and aquatic ecosystems. Recognition, identification, and delineation of these multipurpose regions are critical for structuring and implementing integrated management strategies across federal, state, tribal, and local governmental agencies that are responsible for... More »
Perspective of Antarctica in 1911Last Updated on 2014-06-25 18:41:34Exploration of the Antarctic - Part7
See also Chronology of Antarctic Exploration.
In 1911, the Heroic Age of Antarctic Exploration was in full stride and the world's understanding of the nature of Antarctica was being shaped by many new facts. An interesting snapshot of Antarctica at this time, after the Nimrod Expedition, but before the expeditions to the South Pole was the entry on Polar Regions in the 1911 Edition of the Encyclopaedia Britannica which summarized the view of Antarctica at that time:
In contrast to the Arctic region, the Antarctic is essentially a land area. It is almost certain that the South Pole lies on a great plateau, part of a land that must be larger and loftier than Greenland, and may probably be as large as Australia. This land area may be composed of two main masses, or of one continent and a great archipelago, but it can no longer be... More »
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