LYCOS RETRIEVER 
Species: Plants
built 282 days ago
In the earliest works of science, a species was simply an individual organism that represented a group of similar or nearly identical organisms. No other relationships beyond that group were implied. Aristotle used the words genus and species to mean generic and specific categories. Aristotle and other pre-Darwinian scientists took the species to be distinct and unchanging, with an "essence", like the chemical elements. When early observers began to develop systems of organization for living things, they began to place formerly isolated species into a context. Many of these early delineation schemes would now be considered whimsical and these included consanguinity based on color (all plants with yellow flowers) or behavior (snakes, scorpions and certain biting ants).
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Exotic species are constantly being introduced to new locations around the world, and Canada is certainly no exception. In many cases, the introduced species die out, leaving no permanent impact. Other times, though, they can grow out of control and directly interfere with native ecosystems, perhaps even dominating them and driving native species to extinction. A few of the better-known examples of successful exotic species in Canada include Dutch elm disease, purple loosestrife, zebra mussels, sea lampreys and starlings. The number of exotic plant species is staggering; it is estimated that 800 of the 5 000 plant species in Canada are exotic introductions and successful enough to maintain populations in the wild!
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A coastal plain species found in river bottoms and swampy areas characterized by frequent and prolonged flooding. Baldcypress is a large, long-lived, deciduous tree reaching 100-150 feet in height and 3-6 feet in diameter. It grows best in full sunlight. It can be grown on many upland soils and can tolerate a wide climatic range making it increasingly popular in cities and urban areas as an ornamental or shade tree. Commercially, baldcypress should not be planted above the coastal plain, but for ornamental purposes its range can be extended considerably. The heartwood of old growth baldcypress is very resistant to rot. This is not true with younger second growth trees.
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[A]dopting only an interbreeding approach to species has its costs: it would exclude all asexual organisms from forming species. Interbreeding requires the genetic contributions of two sexual organisms. Asexual organisms reproduce by themselves, either through cloning, vegetative means or self fertilization. Some reptiles and amphibians reproduce asexually. Many insects reproduce asexually. And asexuality is rampant in plants, fungi and bacteria.
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A good illustration of Paine's keystone species concept is provided by the sea otter, which formerly occupied a range extending from the northern Japanese archipelago, through the Aleutian Islands, down the coast of North America as far south as Baja California. The return of the sea otter to southern California, for example, is restoring kelp beds and associated marine life there. That's because one of the favorite delicacies of the otter is the large sea urchin, which in turn feeds on kelp. As the sea otter returns to its native territories, scientists expect the population of invertebrates, like urchins and abalone, for example, to decrease as marine plant biomass increases. In fact, a decrease in sport and commercial abalone fisheries was reported following an influx of sea otters into areas of California, causing a controversy there.
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Researchers at the University of California, San Diego and the University of Bonn, Germany have realized the first global map of estimated plant species richness. The map assessed three hundred thousand species and is the most extensive map of the distribution of biodiversity on Earth to date. [read more >>]
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